This work was supported by NSFC grant 81800928, Research Funding from the West China School/Hospital of Stomatology Sichuan University (No. RCDWJS2021-1), and the State Key Laboratory of Oral Diseases Open Funding grant SKLOD-R013.

This study was approved by the Institutional Animal Care and Use Committee at the State Key Laboratory of Oral Diseases, Sichuan University. Permission was obtained from relevant local agencies before the experiment. Eight 8-10 week old male Sprague-Dawley (SD) rats, with an average weight of 200-250 g, were used for the present study. The animals were obtained from a commercial source (see Table of Materials). Food and water were provided ad libitum throughout the experimental period.
1. Preoperative preparation for the generation of carbon-nanoparticle-assisted PTX rats
<ol>
	<li>Anesthetize the 8-10 week old rats using 2.0%-2.5% isoflurane inhalation, followed by an intraperitoneal (i.p.) injection of tribromoethanol at 10 mL/kg body weight. Guarantee a sufficient depth of anesthesia by testing the absence of the pupillary light reflex. Use vet ointment on the eyes to prevent dryness while under anesthesia. 
	&#8203;NOTE: Rats that are 8-10 weeks old are recognized as adult rats. However, this modeling method can be used on rats as young as 7 days old.</li>
	<li>Prepare the anesthetized SD rats for surgery by shaving the fur of the ventral neck region in the supine position. Disinfect the operative area using povidone-iodine cotton balls (see Table of Materials).</li>
	<li>Cover the animal with surgical drapes (see Table of Materials), and expose the surgical region, aiming to minimize microbial contamination.</li>
</ol>
2. Parathyroidectomy (PTX)
<ol>
	<li>Start at the midpoint between the two ears, and cut a 2 cm incision longitudinally toward the tail using a surgical scalpel. Dissect the fascia and fat layer successively with sharp, curved, serrated forceps.</li>
	<li>Separate the paratracheal muscles, and expose the trachea using relatively blunt forceps under a stereo microscope at 4x-5x magnification.</li>
	<li>Locate the left and right lobes of the butterfly-shaped thyroid glands by the side of the trachea.</li>
	<li>Inject 1 &#181;L of the carbon nanoparticle suspension (see Table of Materials) beneath the membrane of the thyroid glands using a 10 &#181;L syringe with a 30 G beveled needle. After 5 min, irrigate the operative region with saline to clean the extra carbon nanoparticle suspension covering the thyroid gland membrane. 
	NOTE: The recommended injection point is the mesial portion of the thyroid gland lobe, which has fewer blood vessels. A carbon nanoparticle suspension is commonly used in thyroid surgery due to its ability to detect the lymph nodes. Staining the thyroid glands and leaving the parathyroid glands unstained eases the identification of the latter.</li>
	<li>Check to ensure that the thyroid glands turn black while the parathyroid glands remain unstained in ~5 min. Observe the highlighted parathyroid glands under ordinary light using either the light of a stereo microscope or a table lamp. 
	NOTE: Typically, rodents have two drop-shaped parathyroid glands located on the left and right surfaces of the thyroid glands. Occasionally, additional parathyroid glands may be located further away.</li>
	<li>Precisely cut the unstained parathyroid glands with microsurgery forceps and scissors. Use sterile cotton balls for hemostasis or a gelatin sponge if there is more bleeding.</li>
	<li>Close the muscles, fat layers, and skin, layer by layer, with an interrupted horizontal mattress suture using 6-0 polyglactin 910 sutures (see Table of Materials).</li>
	<li>For the sham group, perform all the steps of the preoperative preparation and PTX except step 2.6. Anesthetize the rats, and separate the tissues above the trachea. Locate the parathyroid glands but do not remove them. Conduct postoperative recovery and observation together with the rats of the PTX group.</li>
</ol>
3. Postoperative recovery and observation
<ol>
	<li>After surgery, place the rats on a thermostatic electric blanket (37 &#176;C) to maintain their body temperature. Inject buprenorphine hydrochloride 0.01 mg/kg subcutaneously (s.c) every 12 h as postoperative analgesia. Transfer the rats to a sterile cage when they begin to move and try to crawl.&#160;</li>
	<li>Closely observe the rats postoperatively for 2 h. Return the rats to the rearing room, observe them routinely, and record their state.</li>
	<li>Draw 10 &#181;L of blood from the tail vein 7 days after the surgery. Measure the serum Ca2+, serum Pi, and serum PTH using appropriate commercial kits (see Table of Materials). A successful parathyroidectomy produces a reduced serum ionized Ca2+ level 2 SD lower than that of sham-operated rats (9.00 mmol/L, n = 16). 
	NOTE: A statistics and graphing software (see Table of Materials) was used for the statistical analysis. A Student&#39;s t-test was used to compare the serum and urinary parameters between the sham and PTX groups. p &#60; 0.05 was considered statistically significant. Serum and urinary Ca2+ and Pi and serum urea and creatinine were measured with commercial kits according to the manufacturers&#39; instructions (see Table of Materials). Serum C-telopeptide of type I collagen and osteocalcin were measured with commercially available ELISA kits (see Table of Materials).</li>
</ol>

<ol>
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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hypoparathyroidism.">Hypoparathyroidism.</a> The Journal of Clinical Endocrinology and Metabolism. 105 (6), 1722-1736 (2020).</li><li>Underbjerg, L., Sikjaer, T., Mosekilde, L., Rejnmark, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postsurgical+hypoparathyroidism-Risk+of+fractures,+psychiatric+diseases,+cancer,+cataract,+and+infections.">Postsurgical hypoparathyroidism-Risk of fractures, psychiatric diseases, cancer, cataract, and infections.</a> Journal of Bone and Mineral Research. 29 (11), 2504-2510 (2014).</li><li>Underbjerg, L., Sikjaer, T., Mosekilde, L., Rejnmark, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+epidemiology+of+nonsurgical+hypoparathyroidism+in+Denmark:+A+nationwide+case+finding+study.">The epidemiology of nonsurgical hypoparathyroidism in Denmark: A nationwide case finding study.</a> Journal of Bone and Mineral Research. 30 (9), 1738-1744 (2015).</li><li>Astor, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemiology+and+health-related+quality+of+life+in+hypoparathyroidism+in+Norway.">Epidemiology and health-related quality of life in hypoparathyroidism in Norway.</a> The Journal of Clinical Endocrinology and Metabolism. 101 (8), 3045-3053 (2016).</li><li>Rodriguez-Ortiz, M. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+deficiency+reduces+circulating+levels+of+FGF23.">Calcium deficiency reduces circulating levels of FGF23.</a> Journal of the American Society of Nephrology. 23 (7), 1190-1197 (2012).</li><li>Davies, B. M., Gordon, A. H., Mussett, M. 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The authors declare that they have no competing financial interests.

Epidemiological reports indicate that the detection of thyroid diseases has increased significantly, and the number of related surgeries performed has increased accordingly19,20. The incidence rate of postsurgical hypoparathyroidism is approximately 7.6%8,21, while the increased morbidity of acquired hypoparathyroidism has caused this rare disease to gain greater research attention. It is, therefore, particularly important to establish a suitable animal model to investigate the pathogenesis of the disease, as well as to test the outcomes of novel therapeutic treatments. However, at present, there are limited animal models available. Moreover, the success rate, survival rate, and difficulty of surgical procedures in producing such models remain problematic. Our group has previously reported two HypoPT models in mice. In PTHcre+/Rosa-mTmG mice, the parathyroid glands were fluorescently labeled to help accurately dissect the parathyroid glands, and this method was also helpful for finding parathyroid glands with abnormal anatomical distribution to improve the success rate of surgery14. Another modeling approach used transgenic mice, in which parathyroid gland cells could be targeted by diphtheria toxin. The parathyroid glands could then be destroyed by the systemic administration of the diphtheria toxin without requiring surgery14,15. However, the abovementioned methods require extensive crossbreeding of transgenic mice, resulting in relatively high time and cost requirements. Moreover, the systemic administration of diphtheria toxin may have widespread side effects. Currently, thyro-parathyroidectomy (TPTX) is the usual procedure performed to ensure the resection of the parathyroid glands12. Although the technique is easily performed and has a high success rate, the damage to the thyroid glands cannot be ignored. The potential impact of injury to or destruction of the thyroid glands on the experimental results might be significant, meaning this is a major limitation of all studies in this field21,22.
In the current study, a carbon nanoparticle suspension, commonly used to visualize the thyroid glands in clinical practice, was injected to enhance the PTX surgery. This method is safe, fast, and highly feasible. It can effectively label the thyroid glands with a black stain and leave the parathyroid glands unstained, which enables the precise identification and dissection of the parathyroid glands while avoiding injury to the thyroid glands. This labeling method has the same effect as that achieved using the fluorescent labeling of transgenic mice but is not limited by the genotype. Furthermore, the surgery time of carbon-nanoparticle-assisted PTX is around 20 min, which saves time compared with the 2 h surgery required for 5-ALA fluorescence identification23. In addition, due to the biosecurity of the carbon nanoparticles24, this modeling method can be used on rats as young as 7 days old. One critical step to be noted during the surgery is that the dosage of the carbon nanoparticle suspension can be adjusted according to the weight of the rats. The volume of carbon nanoparticle suspension used in this study (1 &#181;L) is enough for surgery on adult rats, even if some amount is lost in the syringe. The distribution of all the parathyroid glands is difficult for beginners to identify, and plenty of practice is recommended.
The current study has some limitations. For instance, it is impossible to identify remote parathyroid glands unattached to the thyroids using carbon nanoparticles. If the serum parameters remain unchanged after surgery, it may indicate that some remote parathyroid glands were present and not removed. The staining period required for the optimal differentiation and identification of the parathyroid glands was not measured; however, the thyroid glands were stained properly within 5 min of nanoparticle administration and retained the stain during the entire surgical procedure. The functioning of the thyroid glands during the follow-up period was not recorded in this study. However, in our previous study, which involved utilizing a transgenic mouse model to identify and remove the parathyroid glands, the thyroid gland function was shown to be preserved15. The tolerance of the rats to the carbon nanoparticles was also not tested in this study; however, these nanoparticles have been commercially used as pharmaceuticals in clinical surgeries16. Generally, this method allows researchers to choose an animal with a desired genotype and operation time point. Ultimately, this approach is expected to provide useful rat models for acquired hypoparathyroidism.

Parathyroid hormone (PTH) is secreted by the parathyroid glands. It is a major modulator of the calcium balance, maintains phosphate metabolism, and participates in bone turnover1,2. Hypoparathyroidism (HypoPT) manifests as a decreased secretion or functional loss of PTH. It is a rare endocrine disorder, with a prevalence of approximately 9-37 per 100,000 person-years3,4,5. HypoPT is characterized by decreased serum PTH and calcium levels accompanied by increased serum phosphorus6,7. HypoPT is classified based on its cause: acquired hypoparathyroidism (AHypoPT) or idiopathic hypoparathyroidism (IHypoPT)8. AHypoPT is more commonly encountered in clinical practice; about 75% of AHypoPT cases are caused by resection or accidental injury of the parathyroid glands during thyroid surgery or other head and neck surgeries. Other causes include radiotherapy and chemotherapy for head and neck tumors and drug toxicity1,8. Upgraded diagnostic methods and an increase in screening for thyroid gland-associated diseases have increased the number of thyroid gland surgical operations. This has led to a corresponding increase in the related parathyroid gland complications9,10.
Easily established animal models with stable characteristics are needed to better investigate AHypoPT and verify the therapeutic effectiveness of novel treatments. Parathyroidectomy (PTX) performed on rats and mice has been reported in previous studies6,11; however, due to the extremely small size of the parathyroid glands and the variability in their anatomical distribution, the success rate is relatively low in practice. Thus, thyro-parathyroidectomy (TPTX) (i.e., the total removal of the thyroid and parathyroid glands) is usually performed to ensure the resection of the parathyroid glands12. However, the resulting low thyroxine levels may complicate studies with this animal model13. HypoPT models established by other methods, such as drug stimulation and gene editing, cannot properly represent the most common AHypoPT pathogenesis. Our group previously used knockout mouse models to label the parathyroid glands and allow the removal of the parathyroid glands without damaging the thyroid glands and surrounding anatomical structures14,15. However, this method utilizes transgenic mouse models, which require a longer development time due to the mating and breeding requirements.
Therefore, we aimed to establish an easily generated model of AHypoPT. This study describes a rat model for PTX using carbon nanoparticle labeling. A carbon nanoparticle suspension of 50 mg/mL, which is commonly used in thyroid surgery, evenly distributes in the thyroid glands after local injection16. The thyroid glands turn black, but the parathyroid glands are left unstained17, thus clearly distinguishing the parathyroid glands from the thyroid glands and allowing the PTX to be performed without affecting the thyroid glands. This method is suitable for rats of different ages. The injection of the carbon nanoparticle suspension is safe and has a negligible effect on thyroid function18. The carbon nanoparticle-labeled PTX rat model generated in this study showed significant hypocalcemia and hyperphosphatemia phenotypes during the 4 week observation period. Thus, this AHypoPT model is easy to establish and has a reproducible phenotype.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.9% Sodium Chloride Solution</td>
			<td>Kelun Co. Sichuan, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>10 &#181;L 30G NanoFil Syringe</td>
			<td>WPI</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>6-0 polyglactin 910 suture with needle</td>
			<td>Ethicon, Inc</td>
			<td>J510G</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium LiquiColor test</td>
			<td>EKF</td>
			<td>0155-225</td>
			<td>For Ca2+ analysis</td>
		</tr>
		<tr>
			<td>Carbon Nanoparticles Suspension Injection</td>
			<td>Lummy, Chongqing, China</td>
			<td>H20073246</td>
			<td>1 mL : 50 mg</td>
		</tr>
		<tr>
			<td>Creatinine (Cr) Assay kit ( sarcosine oxidase )</td>
			<td>Jiancheng, Nanjing, China</td>
			<td>C011-2-1</td>
			<td>For creatinine analysis</td>
		</tr>
		<tr>
			<td>Disposable Scalpel</td>
			<td>Shinva, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dumstar Biology forceps</td>
			<td>Shinva, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Dissecting Spring Scissors</td>
			<td>Shinva, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MicroVue Rat intact PTH ELISA</td>
			<td>Immunotopics</td>
			<td>30-2531</td>
			<td>For the measurement of PTH in rat serum</td>
		</tr>
		<tr>
			<td>Needle Holder</td>
			<td>Shinva, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphorus Liqui-UV test</td>
			<td>EKF</td>
			<td>0830-125</td>
			<td>For Pi analysis</td>
		</tr>
		<tr>
			<td>Ply gauze</td>
			<td>Weian Co. Henan, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Povidone-Iodine</td>
			<td>Yongan pharmaceutical Co.Ltd. Chengdu, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Prism 9.0 (statistics and graphing software)</td>
			<td>GraphPad Software, Inc., San Diego, CA, USA</td>
			<td></td>
			<td>https://www.graphpad.com/scientific-software/prism/</td>
		</tr>
		<tr>
			<td>Rat C-telopeptide of type I collagen (CTX-I) ELISA Kit</td>
			<td>CUSABIO, Wuhan, China</td>
			<td>CSB-E12776r</td>
			<td>For CTX-I analysis</td>
		</tr>
		<tr>
			<td>Rat Osteocalcin/Bone Gla Protein (OT/BGP) ELISA Kit</td>
			<td>CUSABIO, Wuhan, China</td>
			<td>CSB-E05129r</td>
			<td>For osteocalcin analysis</td>
		</tr>
		<tr>
			<td>Safety Single Edge Razor Blades</td>
			<td>American Safety Razor Company</td>
			<td>66-0089</td>
			<td></td>
		</tr>
		<tr>
			<td>Sprague-Dawley Rats</td>
			<td></td>
			<td></td>
			<td>8 to 10 weeks old</td>
		</tr>
		<tr>
			<td>Surgical Incise Drapes</td>
			<td>Liangyou Co. Sichuan, China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Urea Assay Kit</td>
			<td>Jiancheng, Nanjing, China</td>
			<td>C013-2-1</td>
			<td>For urea analysis</td>
		</tr>
	</tbody>
</table>

generation of hypoparathyroid rats via carbon-nanoparticle-assisted parathyroidectomy

Hypoparathyroidism (HypoPT) is a rare disease involving the parathyroid glands that is characterized by a reduced secretion or potency of the parathyroid hormone (PTH), which leads to high serum phosphorus levels and low serum calcium levels. HypoPT most commonly results from accidental damage to the glands or their removal during thyroid or other anterior neck surgery. Parathyroid/thyroid surgery has become more common in recent years, with a corresponding rise in the occurrence of HypoPT as a postoperative complication. There is a critical need for a HypoPT animal model to better understand the mechanisms underlying the effects of HypoPT on mineral ion homeostasis and to verify the therapeutic effectiveness of novel treatments. Here, a technique is reported to create acquired HypoPT in male rats by performing parathyroidectomy (PTX) using carbon nanoparticles. The rat model shows great promise over the mouse models of hypoparathyroidism.&#160;Importantly, the human PTH receptor binding region has an 84.2% sequence similarity with that of the rat, which is higher than the 73.7% similarity shared with mice. Moreover, the effects of estrogen, which can affect the PTH/PTHrP receptor signaling pathway, have not been fully investigated in male rats. Carbon nanoparticles are lymphatic tracers that stain the thyroid lymph nodes black without affecting their function, but they do not stain the parathyroid glands, which makes them easy to identify and remove. In this study, serum PTH levels were undetectable after PTX, and this resulted in significant hypocalcemia and hyperphosphatemia. Thus, the clinical state of postoperative HypoPT can be remarkably represented in the rat model. Carbon-nanoparticle-assisted PTX can, therefore, serve as an extraordinarily effective and readily implementable model for studying the pathogenesis, treatment, and prognosis of HypoPT.

The locations and number of parathyroid glands were initially observed in rats under a dissection microscope. Before the carbon nanoparticle injection, the thyroid glands were a translucent red color, and the parathyroid glands were hardly distinguishable under the microscope (Figure 1A). After the nanoparticle injection, the thyroid glands were stained black, while the parathyroid glands remained unstained (Figure 1B). The careful dissection of the light-colored parathyroid glands left the thyroid glands untouched (Figure 1C). Generally, the parathyroid glands were distributed over the lateral or posterior edges of the thyroid glands.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64611/64611fig01.jpg" /> 
Figure 1: The appearance of the thyroid and parathyroid glands during the surgical procedures. (A) The thyroid glands (white dotted line) are located lateral to the trachea. (B,C)&#160;The thyroid glands showed black staining (white dotted line) after the injection of the carbon nanoparticles, while the parathyroid glands (yellow dotted line) exhibited a light color. Scale bars = 2 mm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64611/64611fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The operation time from preoperative preparation to PTX completion was approximately 20 min. The 4 week survival rate of the postoperative rats was 90.9% (60/66). The PTX rats were observed to be hunch-backed 1 week after surgery. A sham-operated control group was simultaneously established by conducting all the steps in the protocol except for step 2.6. All the surviving carbon nanoparticle-labeled PTX rats had a lower mean ionized Ca2+ level, which was 2 SD lower than that of the sham-operated group. The hypoparathyroidism phenotype in the carbon nanoparticle-labeled PTX rats, evidenced by reduced serum calcium, elevated serum phosphate, and undetected PTH, remained steady during the 4 week monitoring period.
At 7 days after surgery, the serum Ca2+ and PTH levels were significantly reduced in the PTX rats compared to the sham group (Ca2+ = 4.97 mmol/L &#177; 0.99 mmol/L vs. 8.98 mmol/L &#177; 0.58 mmol/L, p &#60; 0.05; PTH = 13.13 pg/mL &#177; 6.58 v pg/mL s. 313.06 pg/mL &#177; 75.24 pg/mL, p &#60; 0.05). Serum Pi was significantly increased after the PTX surgery (Pi = 13.90 mmol/L &#177; 1.77 mmol/L vs. 7.46 mmol/L &#177; 1.28 mmol/L). The serum levels of urea and creatinine were comparable between the sham and PTX groups 7 days after the PTX surgery (urea = 8.71 mmol/L &#177; 0.81 mmol/L vs. 8.84 mmol/L &#177; 0.89 mmol/L, p &#62; 0.05; creatinine = 49.03 &#181;mol/L &#177; 13.14 &#181;mol/L vs. 53.15 &#181;mol/L &#177; 18.28 &#181;mol/L, p &#62; 0.05). At 14 days after the PTX surgery, the urinary Ca2+ and Pi levels were significantly reduced (Ca2+ = 2.33 mmol/L &#177; 0.53 mmol/L vs. 7.18 mmol/L &#177; 4.27 mmol/L, p &#60; 0.05; Pi = 2.40 mmol/L &#177; 1.90 mmol/L vs. 5.29 mmol/L &#177; 1.52 mmol/L, p &#60; 0.05) (Figure 2).
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/64611/64611fig02.jpg" /> 
Figure 2: Serum Ca2+, Pi, PTH, urea, and creatinine levels and urinary Ca2+ and Pi levels after carbon-nanoparticle-assisted parathyroidectomy. (A) The PTX rats exhibited stable hypocalcemia and hyperphosphatemia over the 4 week observation period (N = 4). (B)&#160;Serum PTH was undetectable in the PTX rats 7 days after the operation (N = 8). (C,D)&#160;The serum levels of urea and creatinine were comparable between the sham and PTX groups 7 days after the surgery (N = 5). (E,F) The urinary Ca2+ and Pi levels were significantly reduced 14 days after PTX surgery (N = 8). The error bars indicate the standard deviation. Abbreviations: PTX = parathyroidectomy; Ca++ = ionized calcium in serum; PTH = parathyroid hormone; Pi = ionized phosphorous in serum. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64611/64611fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
There were no significant differences in body weight between the PTX and sham groups on postoperative day 7 (POD7), POD14, and POD28 (body weight on POD0 = 256.40 g &#177; 4.76 g vs. 252.56 g &#177; 6.69 g, p &#62; 0.05; body weight on POD7 = 266.00 g &#177; 6.93 g vs. 257.44 g &#177; 30.56 g, p &#62; 0.05; body weight on POD14 = 294.80 g &#177; 25.90 g vs. 288.22 g &#177; 37.35 g, p &#62; 0.05; body weight on POD28 = 327.75 g &#177; 24.82 g vs. 324.17 g &#177; 57.97 g, p &#62; 0.05). Moreover, serum C-telopeptide of type I collagen (CTX-1) was statistically decreased on POD28 (CTX-1 = 82.03 pg/mL &#177; 8.98 pg/mL vs. 100.33 pg/mL &#177; 6.36 pg/mL, p &#60; 0.05). Serum osteocalcin showed no significant difference on POD28 (osteocalcin = 913.66 pg/mL &#177; 378.03 pg/mL vs. 1066.17 pg/mL &#177; 549.80 pg/mL, p &#62; 0.05) (Figure 3).
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64611/64611fig03.jpg" /> 
Figure 3: Body weight, blood C-telopeptide of type I collagen, and osteocalcin levels after carbon-nanoparticle-assisted parathyroidectomy. (A)&#160;There were no significant differences in body weight between the PTX and sham groups on POD7, POD14, and POD28 (N = 14).(B)&#160;The&#160;PTX rats exhibited a statistical decrease in serum C-telopeptide of type I collagen (N = 4). (C) There were no significant differences in the serum osteocalcin levels (N = 5). The error bars indicate the standard deviation. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64611/64611fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Generation of Hypoparathyroid Rats via Carbon-Nanoparticle-Assisted Parathyroidectomy at JoVE.com

Generation of Hypoparathyroid Rats via Carbon-Nanoparticle-Assisted Parathyroidectomy

An animal model of acquired hypoparathyroidism (HypoPT) is crucial to understanding how HypoPT affects mineral ion homeostasis and to verify the effectiveness of novel treatments. Here, a technique is presented to generate an acquired hypoparathyroidism (AHypoPT) rat model by parathyroidectomy (PTX) using carbon nanoparticles.

Generation of Hypoparathyroid Rats via Carbon-Nanoparticle-Assisted Parathyroidectomy

Hypoparathyroidism (HypoPT) is a rare disease involving the parathyroid glands that is characterized by a reduced secretion or potency of the parathyroid ...

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Medicine

1.8K Views.  Sichuan University. An animal model of acquired hypoparathyroidism (HypoPT) is crucial to understanding how HypoPT affects mineral ion homeostasis and to verify the effectiveness of novel treatments. Here, a technique is presented to generate an acquired hypoparathyroidism (AHypoPT) rat model by parathyroidectomy (PTX) using carbon nanoparticles.

Video: Generation of Hypoparathyroid Rats via Carbon-Nanoparticle-Assisted Parathyroidectomy

Acute Myocardial Infarction in Rats

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular diseases. Animal models that mimic human cardiac disease, such as myocardial infarction (MI) and ischemia-reperfusion (IR) that induces heart failure as well as pressure-overload (transverse aortic constriction) that induces cardiac hypertrophy and heart failure (Goldman and Tarnavski), are useful models to study cardiovascular disease. In particular, myocardial ischemia (MI) is a leading cause for cardiovascular morbidity and mortality despite controlling certain risk factors such as arteriosclerosis and treatments via surgical intervention (Thygesen). Furthermore, an acute loss of the myocardium following myocardial ischemia (MI) results in increased loading conditions that induces ventricular remodeling of the infarcted border zone and the remote non-infarcted myocardium. Myocyte apoptosis, necrosis and the resultant increased hemodynamic load activate multiple biochemical intracellular signaling that initiates LV dilatation, hypertrophy, ventricular shape distortion, and collagen scar formation. This pathological remodeling and failure to normalize the increased wall stresses results in progressive dilatation, recruitment of the border zone myocardium into the scar, and eventually deterioration in myocardial contractile function (i.e. heart failure). The progression of LV dysfunction and heart failure in rats is similar to that observed in patients who sustain a large myocardial infarction, survive and subsequently develops heart failure (Goldman). The acute myocardial infarction (AMI) model in rats has been used to mimic human cardiovascular disease; specifically used to study cardiac signaling mechanisms associated with heart failure as well as to assess the contribution of therapeutic strategies for the treatment of heart failure. The method described in this report is the rat model of acute myocardial infarction (AMI). This model is also referred to as an acute ischemic cardiomyopathy or ischemia followed by reperfusion (IR); which is induced by an acute 30-minute period of ischemia by ligation of the left anterior descending artery (LAD) followed by reperfusion of the tissue by releasing the LAD ligation (Vasilyev and McConnell). This protocol will focus on assessment of the infarct size and the area-at-risk (AAR) by Evan's blue dye and triphenyl tetrazolium chloride (TTC) following 4-hours of reperfusion; additional comments toward the evaluation of cardiac function and remodeling by modifying the duration of reperfusion, is also presented. Overall, this AMI rat animal model is useful for studying the consequence of a myocardial infarction on cardiac pathophysiological and physiological function.

The rat model of acute myocardial infarction (AMI) is useful to study the consequence of a MI on cardiac pathophysiological and physiological function.

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular ...

Roux-en-Y Gastric Bypass Operation in Rats

Currently, the most effective therapy for the treatment of morbid obesity to induce significant and maintained body weight loss with a proven mortality benefit is bariatric surgery1,2. Consequently, there has been a steady rise in the number of bariatric operations done worldwide in recent years with the Roux-en-Y gastric bypass (gastric bypass) being the most commonly performed operation3. Against this background, it is important to understand the physiological mechanisms by which gastric bypass induces and maintains body weight loss. These mechanisms are yet not fully understood, but may include reduced hunger and increased satiation4,5, increased energy expenditure6,7, altered preference for food high in fat and sugar8,9, altered salt and water handling of the kidney10 as well as alterations in gut microbiota11. Such changes seen after gastric bypass may at least partly stem from how the surgery alters the hormonal milieu because gastric bypass increases the postprandial release of peptide-YY (PYY) and glucagon-like-peptide-1 (GLP-1), hormones that are released by the gut in the presence of nutrients and that reduce eating12.
During the last two decades numerous studies using rats have been carried out to further investigate physiological changes after gastric bypass. The gastric bypass rat model has proven to be a valuable experimental tool not least as it closely mimics the time profile and magnitude of human weight loss, but also allows researchers to control and manipulate critical anatomic and physiologic factors including the use of appropriate controls. Consequently, there is a wide array of rat gastric bypass models available in the literature reviewed elsewhere in more detail 13-15. The description of the exact surgical technique of these models varies widely and differs e.g. in terms of pouch size, limb lengths, and the preservation of the vagal nerve. If reported, mortality rates seem to range from 0 to 35%15. Furthermore, surgery has been carried out almost exclusively in male rats of different strains and ages. Pre- and postoperative diets also varied significantly.
Technical and experimental variations in published gastric bypass rat models complicate the comparison and identification of potential physiological mechanisms involved in gastric bypass. There is no clear evidence that any of these models is superior, but there is an emerging need for standardization of the procedure to achieve consistent and comparable data. This article therefore aims to summarize and discuss technical and experimental details of our previously validated and published gastric bypass rat model.

Numerous studies using gastric bypass rat models have been recently conducted to uncover the underlying physiological mechanisms of Roux-en-Y gastric bypass operations. This article aims to demonstrate and discuss the technical and experimental details of our published gastric bypass rat model to understand advantages and limitations of this experimental tool.

Currently, the most effective therapy for the treatment of morbid obesity to induce significant and maintained body weight loss with a proven mortality ...

Orthotopic Small Bowel Transplantation in Rats

Small bowel transplantation has become an accepted clinical option for patients with short gut syndrome and failure of parenteral nutrition (irreversible intestinal failure). In specialized centers improved operative and managing strategies have led to excellent short- and intermediate term patient and graft survival while providing high quality of life 1,3. Unlike in the more common transplantation of other solid organs (i.e. heart, liver) many underlying mechanisms of graft function and immunologic alterations induced by intestinal transplantation are not entirely known6,7. Episodes of acute rejection, sepsis and chronic graft failure are the main obstacles still contributing to less favorable long term outcome and hindering a more widespread employment of the procedure despite a growing number of patients on home parenteral nutrition who would potentially benefit from such a transplant. The small intestine contains a large number of passenger leucocytes commonly referred to as part of the gut associated lymphoid system (GALT) this being part of the reason for the high immunogenity of the intestinal graft. The presence and close proximity of many commensals and pathogens in the gut explains the severity of sepsis episodes once graft mucosal integrity is compromised (for example by rejection). To advance the field of intestinal- and multiorgan transplantation more data generated from reliable and feasible animal models is needed. The model provided herein combines both reliability and feasibility once established in a standardized manner and can provide valuable insight in the underlying complex molecular, cellular and functional mechanisms that are triggered by intestinal transplantation. We have successfully used and refined the described procedure over more than 5 years in our laboratory 8-11. The JoVE video-based format is especially useful to demonstrate the complex procedure and avoid initial pitfalls for groups planning to establish an orthotopic rodent model investigating intestinal transplantation.

Small bowel transplantation has become an accepted treatment option for patients with irreversible intestinal failure. Our experimental model of orthotopic small bowel transplantation in rats serves as a reliable tool to address underlying immunologic and inflammatory processes that complicate intestinal transplantation.

Small  bowel transplantation has become an accepted clinical option for patients with  short gut syndrome and failure of parenteral nutrition ...

Orthotopic Liver Transplantation in Rats

Clinical progress in the field of liver transplantation has been largely supported by animal models1,2. Since the publication of the first orthotopic rat liver transplantation in 1979 by Kamada et al.3, this model has remained the gold standard despite various proposed alternative techniques4. Nevertheless, its broader use is limited by its steep learning curve5.
In this video paper, we show a simple and easy-to-establish revision of Kamada's two-cuff technique. The suprahepatic vena cava anastomosis is performed manually with a running suture, and the vena porta and infrahepatic vena cava anastomoses are performed utilizing a quick-linker cuff system6. Manufacturing the quick-linker kit is shown in a separate video paper.

We present an easy-to-establish revision of the classical two-cuff technique for orthotopic liver transplantation in rat.

Clinical progress in the field of liver transplantation has been largely supported by animal models1,2. Since the publication of the first orthotopic rat ...

Histological Quantification of Chronic Myocardial Infarct in Rats

Myocardial infarction is defined as cardiomyocyte death due to prolonged ischemia; an inflammatory response and scar formation (fibrosis) follow the ischemic injury. Following the initial acute phase, chronic remodeling of the left ventricle (LV) modifies the structure and function of the heart. Permanent coronary ligation in small animals has been widely used as a reference model for a chronic model of MI. Thinning of the infarcted wall progressively develops to transmural fibrosis. Histological assessment of infarct size is commonly performed; nevertheless, a standardization of the methods for quantification is missing. Indeed, important methodological aspects, such as the number of sections analyzed and the sampling and quantification methods, are usually not described and therefore preclude comparison across investigations. Too often, quantification is performed on a single section obtained at the level of the papillary muscles. Because novel strategies aimed at reducing infarct expansion and remodeling are under investigation, there is an important need for the standardization of accurate heart sampling protocols. We describe an accurate method to quantify the infarct size using a systematic sampling of harvested rat heart and image analyses of trichromatic stained histological sections obtained from base to apex. We also provide evidence that calculating the expansion index (EI) allowed for infarct size assessment, taking into account changes of the left ventricle throughout the remodeling.

The post-mortem assessment of myocardial infarction (MI) in rodents is based on quantification of the infarct on stained heart sections. We describe an accurate method to quantify the infarct size using systematic sampling of harvested rat hearts from base to apex and image analyses of trichrome-stained histological sections.

Myocardial infarction is defined as cardiomyocyte death due to prolonged ischemia; an inflammatory response and scar formation (fibrosis) follow the ...

Two Techniques to Create Hypoparathyroid Mice: Parathyroidectomy Using GFP Glands and Diphtheria-Toxin-Mediated Parathyroid Ablation

Hypoparathyroidism (HP) is a disorder characterized by low levels of PTH which lead to hypocalcemia, hyperphosphatemia, and low bone turnover. The most common cause of the disease is accidental removal of the parathyroid glands during thyroid surgery. Novel therapies for HP are needed, but testing them requires reliable animal models of acquired HP. 
Here, we demonstrate the generation of two mouse models of acquired HP. In the GFP-PTX model, mice with green fluorescent protein (GFP) expressed specifically in the parathyroids (PTHcre-mTmG) were created by crossing PTHcre+ mice with Rosa-mTmGfl/fl mice. Green fluorescing parathyroid glands are easily identified under a fluorescence dissecting microscope and parathyroidectomy is performed in less than 20 min. After fluorescence-guided surgery, mice are profoundly hypocalcemic. Contrary to the traditional thyro-parathyroidectomy, this precise surgical approach leaves thyroid glands and thyroid function intact. The second model, which does not require surgery, is based on a diphtheria-toxin approach. PTHcre-iDTR mice, which express the diphtheria toxin (DT) receptor specifically in the parathyroids, were generated by crossing the inducible DTR mouse with the PTHcre mouse. Parathyroid cells are thus rendered sensitive to diphtheria toxin (DT) and can be selectively destroyed by systemically injecting mice with DT. The resulting hypocalcemic phenotype is stable.

Mice with acquired hypoparathyroidism would be useful for studying novel drug therapies for hypoparathyroidism. Two procedures to create such mice are demonstrated. The GFP-PTX mouse is generated by surgical parathyroidectomy guided by green fluorescing parathyroid glands. A second, non-surgical approach is based on parathyroid-specific expression of the diphtheria toxin receptor.

Hypoparathyroidism (HP) is a disorder characterized by low levels of PTH which lead to hypocalcemia, hyperphosphatemia, and low bone turnover. The most ...

One-anastomosis Gastric Bypass (OAGB) in Rats

The goal of this protocol is to set up a preclinical model of bariatric surgery and, more specifically, OAGB in obese rats. Based on this preclinical model, longitudinal studies can be carried out to provide an improved understanding of the mechanisms underlying the outcomes seen after bariatric surgery in humans. For this purpose, rats are operated on through a laparotomy under general anesthesia with isoflurane. First, the surgeon creates a long and tubular gastric pouch: after greater curve and hiatal dissection, the nonglandular stomach is stapled and removed. Then, the remaining stomach is also stapled in order to create a gastric tube and exclude the antrum of the stomach. After that, the surgeon performs a single end-to-side gastrojejunostomy 35 cm from the duodenojejunal angle. This limb length has been chosen in order to reproduce the same ratio between the biliopancreatic limb (BPL) and common limb (CL) length as in human bariatric surgery. The operation ends by aponeurotic and cutaneous closure. The early postoperative management consists of subcutaneous hydration, an intramuscular prophylactic antibiotic injection, a parietal injection of xylocaine, the administration of painkillers, and a progressive reintroduction of diet.

One-anastomosis Gastric Bypass OAGB in Rats

This protocol is for the performance of one-anastomosis gastric bypass (OAGB) on rat. The operator performs a long and tubular-stapled gastric pouch followed by hand-sewn anastomosis. For this model, the operator reproduces the same ratio between biliopancreatic and common limb in humans; therefore, the biliopancreatic limb measures 35 cm.

The goal of this protocol is to set up a preclinical model of bariatric surgery and, more specifically, OAGB in obese rats. Based on this preclinical ...

Echocardiographic Assessment of Cardiac Anatomy and Function in Adult Rats

The use of experimental animal models has become crucial in cardiovascular science. Most studies using rodent models are focused on two-dimensional imaging to study the cardiac anatomy of the left ventricle and M-mode echo to assess its dimensions. However, this could limit a comprehensive study. Herein, we describe a protocol that allows an assessment of the heart chamber size, left ventricular function (systolic and diastolic) and valvular function. A conventional medical ultrasound machine was used in this protocol and different echo views were obtained through left parasternal, apical and suprasternal windows. In the left parasternal window, the long and short axis were acquired to analyze left chamber dimensions, right ventricle and pulmonary artery dimensions, and mitral, pulmonary and aortic valve function. The apical window allows the measurement of heart chamber dimensions and evaluation of systolic and diastolic parameters. It also allows Doppler assessment with detection and quantification of heart valve disturbances (regurgitation or stenosis). Different segments and walls of the left ventricle are visualized throughout all views. Finally, the ascending aorta, aortic arch, and descending aorta can be imaged through the suprasternal window. A combination of ultrasound imaging, Doppler flow and tissue Doppler assessment have been obtained to study cardiac morphology and function. This represents an important contribution to improve the assessment of cardiac function in adult rats with impact for research using these animal models.

A non-invasive protocol for transthoracic echocardiography assessment of cardiac anatomy and function for adult rats is presented in the current study. The heart valves, all four cardiac chambers and the ascending aorta, aortic arch and descending aorta are studied in detail.

The use of experimental animal models has become crucial in cardiovascular science. Most studies using rodent models are focused on two-dimensional ...

Inducing Acute Liver Injury in Rats via Carbon Tetrachloride (CCl4) Exposure Through an Orogastric Tube

Acute liver injury (ALI) plays a crucial role in the development of hepatic failure, which is characterized by severe liver dysfunction including complications such as hepatic encephalopathy and impaired protein synthesis. Appropriate animal models are vital to test the mechanism and pathophysiology of ALI and investigate different hepatoprotective strategies. Due to its ability to perform chemical transformations, carbon tetrachloride (CCl4) is widely used in the liver to induce ALI through the formation of reactive oxygen species. CCl4 exposure can be performed intraperitoneally, by inhalation, or through a nasogastric or orogastric tube. Here, we describe a rodent model, in which ALI is induced by CCl4 exposure through an orogastric tube. This method is inexpensive, easily performed, and has minimal hazard risk. The model is highly reproducible and can be widely used to determine the efficacy of potential hepatoprotective strategies and assess markers of liver injury.

Inducing Acute Liver Injury in Rats via Carbon Tetrachloride CCl4 Exposure Through an Orogastric Tube

This protocol describes a common and feasible method of inducing acute liver injury (ALI) via CCl4 exposure through an orogastric tube. CCl4 exposure induces ALI through the formation of reactive oxygen species during its biotransformation in the liver. This method is used to analyze the pathophysiology of ALI and examine different hepatoprotective strategies.

Acute liver injury (ALI) plays a crucial role in the development of hepatic failure, which is characterized by severe liver dysfunction including ...

Intratracheal Instillation of Stem Cells in Term Neonatal Rats

Prolonged exposure to high concentrations of oxygen leads to inflammation and acute lung injury, which is similar to human bronchopulmonary dysplasia (BPD). In premature infants, BPD is a major complication despite early use of surfactant therapy, optimal ventilation strategies, and noninvasive positive pressure ventilation. Because pulmonary inflammation plays a crucial role in the pathogenesis of BPD, corticosteroid use is one potential treatment to prevent it. Nevertheless, systemic corticosteroid treatment is not usually recommended for preterm infants due to long-term adverse effects. Preclinical studies and human phase I clinical trials demonstrated that use of mesenchymal stromal cells (MSCs) in hyperoxia-induced lung injuries and in preterm infants is safe and feasible. Intratracheal and intravenous MSC transplantation has been shown to protect against neonatal hyperoxic lung injury. Therefore, intratracheal administration of stem cells and combined surfactant and glucocorticoid treatment has emerged as a new strategy to treat newborns with respiratory disorders. The developmental stage of rat lungs at birth is equivalent to that in human lungs at 26&#8722;28 week of gestation. Hence, newborn rats are appropriate for studying intratracheal administration to preterm infants with respiratory distress to evaluate its efficacy. This intratracheal instillation technique is a clinically viable option for delivery of stem cells and drugs into the lungs.

Described is a protocol for performing intratracheal transplantation of mesenchymal stromal cells (MSCs) through intratracheal injection in term neonatal rats. This technique is a clinically viable option for delivery of stem cells and drugs into neonatal rat lungs to evaluate their efficacy.

Prolonged exposure to high concentrations of oxygen leads to inflammation and acute lung injury, which is similar to human bronchopulmonary dysplasia ...

Generation of Hypoparathyroid Rats via Carbon-Nanoparticle-Assisted Parathyroidectomy

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Acute Myocardial Infarction in Rats

Roux-en-Y Gastric Bypass Operation in Rats

Orthotopic Small Bowel Transplantation in Rats

Orthotopic Liver Transplantation in Rats

Histological Quantification of Chronic Myocardial Infarct in Rats

Two Techniques to Create Hypoparathyroid Mice: Parathyroidectomy Using GFP Glands and Diphtheria-Toxin-Mediated Parathyroid Ablation

One-anastomosis Gastric Bypass (OAGB) in Rats

Echocardiographic Assessment of Cardiac Anatomy and Function in Adult Rats

Inducing Acute Liver Injury in Rats via Carbon Tetrachloride (CCl₄) Exposure Through an Orogastric Tube

Intratracheal Instillation of Stem Cells in Term Neonatal Rats