This study was supported by the National Nature Science Foundation of China (No. 81974572 and No.82274523) and the Beijing University of Chinese Medicine (No.202310026002).

This protocol has received ethical approval from the Beijing University of Chinese Medicine (No.2023033103-1183). Twelve male Sprague-Dawley rats (weight, 208 g &#177; 5 g) were used in this protocol and divided into four groups: NC group (n = 3), OA group (n = 3), C. acnes group (n = 3) and OA + C. acnes group (n = 3).
1. Developing the acne model
<ol>
	<li>Measure and record the thickness of rat ears using an electronic vernier caliper (see Table of Materials) before modeling.
	<ol>
		<li>Place the outer jaw of the electronic vernier caliper at the midpoint of the outer edge of the ear and extend it into the ear canal. Record the thickness of 2/3 points and the thickness of 1/2 points along the line. Measure each point 3x and calculate the average values of the thickness of two points to be considered the thickness of the ear.</li>
	</ol>
	</li>
	<li>Tilt the rat&#39;s head to one side, make the ear face upwards, and apply 50 &#181;L of oleic acid (see Table of Materials) to the ventral and dorsal sides of the ear evenly, once a day, for 25 days.</li>
	<li>From day 21 to day 25, daily prior to the application of oleic acid, anesthetize the rats using 4% isoflurane and then inject 50 &#181;L of 1 &#215; 107 CFU C. acnes suspension (see Table of Materials) intradermally into the ventral surface of the ear using a 1 mL syringe equipped with a 34 G or 36 G needle (see Table of Materials). 
	NOTE: Take care to avoid blood vessels in the ear when injecting intradermally. A micro-syringe with a 34 G or 36 G needle (see Table of Materials) is required. To ensure proper intradermal injection, the needle should be punctured at an angle of 10 to 15 degrees, with a depth of approximately 1 mm.</li>
	<li>On day 25, measure and record the thickness of the ears, as described in step 1.1. 
	NOTE: The OA group was only smeared by oleic acid as described in step 1.2 and injected with saline from the 21st to the 25th day. The C. acnes group was only injected intradermally by C. acnes suspension, as described in step 1.3. The OA + C. acnes group was treated with oleic acid and C. acnes suspension, as described in steps 1.2 and 1.3.</li>
</ol>
2. Tissue collection and analysis
<ol>
	<li>On day 26, after the rats are humanely euthanized using an institutionally approved method, drill fixed size on bilateral ears with an 8 mm ring drill.</li>
	<li>Immerse the ear tissues in 4% paraformaldehyde for 24 h, followed by paraffin-embedding and sectioning into slices 5 &#181;m thick for hematoxylin and eosin (HE) staining20. Observe the sections under a light microscope and record the pathological changes for follow-up evaluation by a pathologist. Assign scores to the pathological changes according to Table 1 (also see Figure 1).</li>
	<li>Deparaffinize, rehydrate, and heat the sections for antigen retrieval. Inactivate endogenous peroxidases by incubating with 0.3% H2O2 in methanol for 15 min at room temperature.</li>
	<li>Wash the sections with phosphate-buffered saline (PBS) and then incubate them with 3% BSA for 30 min at room temperature.</li>
	<li>Incubate the sections with TNF-&#945; monoclonal antibody (dilution 1:800) (see Table of Materials) at 4 &#176;C overnight.</li>
	<li>Wash the sections with PBS again and incubate with horseradish peroxidase-conjugated secondary antibody (see Table of Materials) for 50 min.</li>
	<li>After another PBS wash, apply 3,3&#39;-diaminobenzidine (DAB) mixture to the slides and monitor the staining process under a microscope, stopping the reaction with PBS when the desired intensity is reached.</li>
	<li>Counterstain the sections with Meyer&#39;s hematoxylin for 1 min, rinse them with running water, and dehydrate and mount the sections. Observe the sections under a microscope and record the pathological changes for follow-up evaluation by a pathologist.</li>
</ol>
3. Statistical analysis
<ol>
	<li>Perform statistical analysis.</li>
	<li>Present data as mean &#177; standard deviation. Access the normality of all the data using the Shapro-Wilke test. If it follows a normal distribution, use one-way ANOVA to assess significant differences. For non-normally distributed data, apply the Kruskal-Wallis test followed by Dunn&#39;s multiple comparisons. A p-value less than 0.05 is considered statistically significant.</li>
</ol>

Establishing a Compound Acne Model in Rats Using Oleic Acid and C. acnes

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M., Thiboutot, D., Tan, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reviewing+the+global+burden+of+acne:+how+could+we+improve+care+to+reduce+the+burden.">Reviewing the global burden of acne: how could we improve care to reduce the burden.</a> The British Journal of Dermatology. 184 (2), 219-225 (2021).</li><li>Hazarika, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acne+vulgaris:+new+evidence+in+pathogenesis+and+future+modalities+of+treatment.">Acne vulgaris: new evidence in pathogenesis and future modalities of treatment.</a> Journal of Dermatological Treatment. 32 (3), 277-285 (2021).</li><li>Das, S., Reynolds, R. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+acne+pathogenesis:+implications+for+therapy.">Recent advances in acne pathogenesis: implications for therapy.</a> American Journal of Clinical Dermatology. 15 (6), 479-488 (2014).</li><li>Dr&#233;no, B., 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=Cutibacterium+acnes+(Propionibacterium+acnes)+and+acne+vulgaris:+a+brief+look+at+the+latest+updates.">Cutibacterium acnes (Propionibacterium acnes) and acne vulgaris: a brief look at the latest updates.</a> Journal of the European Academy of Dermatology and Venereology: JEADV. 32, 5-14 (2018).</li><li>Marples, R. R., Downing, D. T., Kligman, A. 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H., 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=HR-1+mice:+A+new+inflammatory+acne+mouse+model.">HR-1 mice: A new inflammatory acne mouse model.</a> Annals of Dermatology. 27 (3), 257-264 (2015).</li><li>De Young, L. M., Young, J. M., Ballaron, S. J., Spires, D. A., Puhvel, S. 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All authors declare that they have no conflicts of interest.

As the methodology and evaluation criteria for an acne model were not clear, this protocol aimed to provide a reference for researchers studying acne. Due to the small size of the mouse ear and the interference caused by growing hair on the back, the use of depilatory cream and a shaver, the ear of the rat may be a better alternative to establish a rodent model of acne. We had attempted to create the acne model on the back skin of rats, but the effect was not as good as those observed on the rat ear.
Some researchers only adopt a single methodology to cause acne inflammation, such as applying oils or injecting microbes14,16. However, studies have shown that increased sebum secretion will promote the excessive proliferation of C. acnes in clogged follicles, while C. acnes in turn stimulates the abnormal secretion of sebaceous glands; the interplay between both may exacerbate acne inflammation. Therefore, the compound model induced by oils and C. acnes may be more consistent with the clinical lesions of acne10,21,22. To objectively assess the pathological alterations across different experimental groups, we devised a scoring system inspired by prior research, which includes the keratin accumulation and the resulting enlargement of hair follicle canals and epithelial proliferation, the infiltration of inflammatory cells in the dermis, and even the further development of abscess (Table 1 and Figure 1)16,23. Utilizing this scoring method, along with histopathological and immunohistochemical (IHC) analyses, we found that the application of C. acnes and oleic acid to the ears led to more significant dermal disorder and inflammation. These findings mirror the symptoms observed in moderate cases of human acne, underscoring the value of this composite model in mimicking the development of acne (Figure 4 and Figure 5)24.
To better evaluate the model, it is necessary to record the thickness of the ears before applying oil and C. acnes. Considering that the external and internal thickness of the ear are different, we recorded two specific points to ensure that the results were better to represent the thickness of the ears and two operators collaborated while measuring the ears. When applying oleic acid to the ear, attention should be paid to the fact that the fluidity of oleic acid makes it easily flow into the ear canal and irritate the rats; hence, it is necessary to tilt the head of rats to avoid oleic acid going into the ear canal.
Comedones were observed on day 7, and the lesions continued to be aggravated until the end of the experiment. The stimulation with C. acnes is another important factor affecting acne. C. acnes not only promotes lipid synthesis in sebaceous glands but also reacts with inflammatory cells around the hair follicle and sebaceous glands in the dermis to induce inflammatory factors; this further aggravates inflammatory response6,25. Therefore, we use intradermal injection of C. acnes to accelerate the inflammation. Considering that the ears of rats are extremely thin, micro needles are needed to avoid piercing them. To ensure proper intradermal injection, the needle should be punctured at an angle of 10 to 15 degrees, with a depth of approximately 1 mm. In addition, when one operator carries out the intradermal injection, another operator must fix the head of the rats to prevent the ears from being pierced. To prevent hemorrhage, the injection site must avoid the superficial blood vessels of the rats. After being injected with C. acnes, the ears were significantly rougher, redder, and more swollen and found with papules (Figure 3).
The applications of sebum/sebum components and C. acnes vary in different experiments. Some researchers adopted the method of injection with C. acnes once and then application with sebum for seven days, which induced abscess, erythema, and induration on the back of rats19. Some other researchers injected C. acnes for 4 days and smeared sebum for 30 days on the ears of rats18. There is no unified standard because acne inflammation is related to the application of sebum/sebum components, the activity and concentration of C. acnes, and the tissues for the model. In this experiment, instead of artificial sebum, oleic acid was used for simulating sebum, considering that oleic acid not only induces keratinization of hair follicles, stimulates epidermis inflammation, but also promotes the growth of C. acnes6,7,8. In the experiment, 7 days after the application of oleic acid, the rats&#39; ears showed redness and swelling. From day 7 to day 14, the rat ears began to display scales and comedones. From day 15 to day 21, comedones increased, but no further acne symptoms were observed. On day 21, we began to intradermally inject 1 &#215; 107 CFU C. acnes, a widely used approach documented in previous studies19.
At first, the effects were not obvious, but later, we found papules in the ears of the rats injected with C. acnes. Given that the ear thickness did not show significant variation over time among the groups, we decided to terminate the experiment on day 25 (Figure 2 and Table 2). This protocol still has some limitations. The small size of the ear area may affect follow-up drug treatment. C. acnes is not the only microbiota involved in the pathological process of acne, so it may be better to use a variety of bacteria to induce acne to mimic the clinical condition26.

Acne vulgaris is a common chronic skin disease characterized by the presence of comedones, papules, and pustules on the face, neck, and chest, which, in severe cases, may progress to nodules, cysts, and permanent scars1. Epidemiological studies report that acne impacts 9.4% of the global population while its resulting symptoms pose severe physical and psychosocial challenges2,3.
The pathogenesis of acne is multifactorial, including four critical processes: excess sebum production, comedone formation, follicular colonization by skin microbiota, and the release of inflammatory mediators around the pilosebaceous unit4,5. Increased sebum secretion, resulting in the accumulation of excess unsaturated free fatty acids (UFFAs), contributes to the abnormal reproduction of skin microbiota, one of which is Cutibacterium acnes, as shown in genomic studies6. Meanwhile, skin microbiota decomposes the sebum and increases the concentration of UFFAs, leading to a vicious circle7. In addition, excess UFFAs cause hyperkeratinization in hair follicles, which in turn triggers acne8. Skin microbiota and increased sebum both activate Toll-like receptors (TLRs) to produce multiple proinflammatory cytokines such as interleukin (IL)-1 and TNF-&#945;9,10. This cascade of inflammation, coupled with increased sebum and microbial overgrowth, culminates in pronounced hyperkeratosis of the hair follicle and the onset of acne11.
The rapid development in the field of acne research and related clinical requirements has driven the creation of a series of animal models of acne inflammation on the rat ear, the backs of rats or mice, and rabbit ear12,13,14,15. The methods include intradermal injection of C. acnes,&#160;the application of oils on the skin to simulate the abnormal secretion of the sebaceous glands and hyperkeratinization, or a combination of both to accelerate the skin inflammation to form acne16,17,18,19. However, the usage and dosage of chemical agents and biological agents vary among previous studies, which may confuse researchers intending to establish an appropriate acne model. This study aimed to establish an easy-to-operate and effective method to form a compound acne rodent model and provide a model reference for researchers studying acne vulgaris.

<table><tbody><tr><td>Anaero-indicator&amp;nbsp;</td><td>Mitsubishi, Japan</td><td>C-22</td><td></td></tr><tr><td>AnaeroPack</td><td>Mitsubishi, Japan</td><td>C-11, C-41</td><td></td></tr><tr><td>Columbia blood agar plate</td><td>BeNa Cuture Collection, China</td><td>BNCC330605</td><td></td></tr><tr><td>Constant temperature incubator</td><td>SHANGCHENG, China</td><td>303-0</td><td></td></tr><tr><td>Cotton swab</td><td>HYNAUT, China</td><td>_</td><td></td></tr><tr><td>&lt;em&gt;Cutibacterium acnes&lt;/em&gt;</td><td>BeNa Cuture Collection, China</td><td>BNCC330605</td><td></td></tr><tr><td>Dako REAL EnVision Detection System, Peroxidase/DAB+, Rabbit/Mouse</td><td>DAKO, Denmark</td><td>K5007</td><td></td></tr><tr><td>disposable sterile injection needle</td><td>Zhejiang Oujian Medical Apparatus, China</td><td>_</td><td></td></tr><tr><td>Electronic scale</td><td>JINXUAN, China</td><td>A017</td><td></td></tr><tr><td>Electronic vernier caliper</td><td>Deli, China</td><td>DL90150</td><td></td></tr><tr><td>Oleic acid (Analytical reagent, AR)</td><td>Fangzheng, China</td><td>_</td><td></td></tr><tr><td>Sodium chloride injection</td><td>CR Double CRANE, China</td><td>Y2212241</td><td></td></tr><tr><td>SPSS Statistics</td><td>IBM, USA</td><td>26.0</td><td></td></tr><tr><td>sterile hypodermic syringes</td><td>Shandong weigao group medical polymer, China</td><td>_</td><td></td></tr><tr><td>TNF Alpha Monoclonal antibody</td><td>Proteintech Group,int, USA</td><td>60291-1-lg</td><td></td></tr></tbody></table>

a rat model of compound acne

Acne vulgaris is a prevalent chronic skin condition characterized by the presence of comedones, papules, and pustules on the face, neck, and chest. To simulate the inflammation of acne vulgaris, this protocol details an approach to establish a compound acne rodent model by inducing acne inflammation in rat ears using oleic acid and Cutibacterium acnes (C. acnes).&#160;Rats were randomly divided into four groups: the normal control group (NC), ears treated with oleic acid group (OA), ears treated with C. acnes group (C. acnes), ears treated with oleic acid and C. acnes (OA + C. acnes). To mimic excessive sebum production, oleic acid was smeared on the ears of rats in OA and OA + C. acnes groups for 25 days.
From days 21 to 25, C. acnes suspension was injected intradermally into the ears of rats in the C. acnes and OA + C. acnes groups to aggravate the acne inflammation. Ear thickness was measured weekly as a gauge of inflammation severity. Gross observation, hematoxylin and eosin staining, and immunohistochemistry (IHC) were conducted and the results showed that the ears of the OA group and the OA + C. acnes group were thickened and indurated, accompanied by erythema and the presence of comedones. Additionally, papules were observed in C. acnes and OA + C. acnes groups. The histopathology exhibited hyperkeratinization and expanded infundibulum of the hair follicles in OA and OA + C. acnes groups. Infiltration of inflammatory cells and abscesses were found in the dermis of C. acnes and OA + C. acnes groups. The IHC results confirmed increased levels of tumor necrosis factor (TNF)-&#945; in the dermis of C. acnes and OA + C. acnes groups. All the above results collectively indicated the successful establishment of the compound acne rodent model.

Thickness and skin appearance 
From day 7 to day 21, the ears in the OA group and the OA + C. acnes group were significantly thicker than that of the NC and C. acnes groups. On day 25, the ears in the OA group, C. acnes group, and OA + C. acnes group were significantly thicker than those of the NC group (p &#60; 0.05). The average thickness of the ears during the experiment is shown in Figure 2 and Table 2.
From day 7 to day 25, the ears in the OA group and the OA + C. acnes group were thickened and indurated, accompanied by erythema, scales, and comedones. The rats were observed to be scratching their ears from time to time, which caused bleeding. On day 25, papules were found in the ears of the C. acnes group and the OA + C. acnes group (Figure 3).
Histopathology 
Parakeratosis and hyperkeratosis were observed in the hair follicles, along with hypertrophy of the granular layer and spinous layer, and dilation of the hair follicle infundibulum in the ears of the OA group and the OA + C. acnes group. The dermis of the C. acnes and OA + C. acnes groups showed mixed inflammatory cell infiltration, including lymphocytes and neutrophils. Also, the dermis exhibited a significant presence of erythrocyte extravasation and abscesses in C. acnes and OA + C. acnes (Figure 4). As shown in Figure 5, the pathological scoring revealed an increase in the C. acnes group and OA group compared to the NC group and the score was significantly higher in the OA + C. acnes group than in the NC and OA groups (p &#60; 0.05).
IHC 
As shown in Figure 6, TNF-&#945; was highly expressed in the dermis of the C. acnes and OA + C. acnes groups.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65859/65859fig01.jpg" /> 
Figure 1: Sample images of pathological scores. Inflammatory cells are marked with red arrows. Refer to Table 1 for the scoring assignment. (A) Score = 0, no horn in infundibulum; (B) score = 1, epithelial hyperplasia and a dense, consistent accumulation of horn distending the follicular canal, though not severe; (C) score = 1, a small number of inflammatory cells around the follicles; (D) score = 2, widespread infiltration of inflammatory cells in the dermis; (E) score = 3, accumulation of dense horn that expands the infundibulum and extends into the sebaceous ducts, resembling the comedones of clinical cases; (F) presence of abscesses around the infundibulum that can potentially result in papules or pustule. Scale bars = 100 &#181;m. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65859/65859fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65859/65859fig02.jpg" /> 
Figure 2: The changing trends of ear thickness from day 0 to day 25. The NC group is indicated by the red line, the OA group is indicated by the blue line, the C. acnes group is indicated by the green line, and the OA and C. acnes group is indicated by the yellow line. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65859/65859fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/65859/65859fig03.jpg" /> 
Figure 3: Gross appearance of ears. The comedones and papules are denoted by red arrows. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65859/65859fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/65859/65859fig04.jpg" /> 
Figure 4: Histology of rat ears. (&#9650;) Hyperkeratosis; (&#9632;) parakeratosis; (&#8226;) expanded infundibulum of the hair follicle; (&#9830;) Infiltration of inflammatory cells. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65859/65859fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/65859/65859fig05.jpg" /> 
Figure 5: Pathological score. @ indicates a statistically significant difference between the NC group and the C. acnes group; # indicates a significant difference between the NC group and the OA + C. acnes group; * indicates a significant difference between the OA + C. acnes group and the OA group (p &#60; 0.05). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65859/65859fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/65859/65859fig06.jpg" /> 
Figure 6: IHC images of TNF-&#945; expression in rat ears. (&#9830;) Infiltration of inflammatory cells. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65859/65859fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Score</td>
			<td colspan="3">Characteristics</td>
		</tr>
		<tr>
			<td>0</td>
			<td colspan="3">Non-comedogenic. (see Figure 1 A)</td>
		</tr>
		<tr>
			<td>1</td>
			<td colspan="3">Epithelial hyperplasia and a dense, consistent accumulation of horn beginning to distend the follicular canal. (see Figure 1 B)</td>
		</tr>
		<tr>
			<td>1</td>
			<td colspan="3">The presence of a small number of inflammatory cells, especially around the follicles or sebaceous ducts. (see Figure 1 C)</td>
		</tr>
		<tr>
			<td>2</td>
			<td colspan="3">Widespread infiltration of a large number of inflammatory cells. (see Figure 1 D)</td>
		</tr>
		<tr>
			<td>3</td>
			<td colspan="3">The presence of accumulation of dense horn that expands the infundibulum and extends into the sebaceous ducts, along with notable hyperplasia of follicular epithelium. (see Figure 1 E)</td>
		</tr>
		<tr>
			<td>3</td>
			<td colspan="3">The presence of abscesses. (see Figure 1 F)</td>
		</tr>
	</tbody>
</table>
Table 1: Pathological score assignment. Sample images are shown in Figure 1.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Time</td>
			<td>&#160;NC group (mm)</td>
			<td>OA group (mm)</td>
			<td>C. acnes group (mm)</td>
			<td>OA + C. acnes group (mm)</td>
		</tr>
		<tr>
			<td>Day 0</td>
			<td>0.4000&#177;0.0250</td>
			<td>0.4167&#177;0.0144</td>
			<td>0.4500&#177;0.0000</td>
			<td>0.4667&#177;0.0382</td>
		</tr>
		<tr>
			<td>Day 7</td>
			<td>0.5250&#177;0.0661</td>
			<td>0.7667&#177;0.0878*&#9650;</td>
			<td>0.4500&#177;0.0000</td>
			<td>0.7917&#177;0.0764*&#9650;</td>
		</tr>
		<tr>
			<td>Day 14</td>
			<td>0.5083&#177;0.0289</td>
			<td>0.8167&#177;0.1233*&#9650;</td>
			<td>0.6083&#177;0.0382</td>
			<td>0.9333&#177;0.0804*&#9650;</td>
		</tr>
		<tr>
			<td>Day 21</td>
			<td>0.5250&#177;0.0433</td>
			<td>1.0667&#177;0.2241*&#9650;</td>
			<td>0.5583&#177;0.0144</td>
			<td>0.9417&#177;0.0722*&#9650;</td>
		</tr>
		<tr>
			<td>Day 25</td>
			<td>0.5750&#177;0.0500</td>
			<td>0.8250&#177;0.1392*</td>
			<td>0.9500&#177;0.1639*</td>
			<td>1.0583&#177;0.0804*</td>
		</tr>
	</tbody>
</table>
Table 2: Thickness of the ears. Data are displayed as mean &#177; standard deviation. Symbol &#34;*&#34; indicates a statistically significant difference compared with the NC group; Symbol &#34;&#9650;&#34; indicates a statistically significant difference compared with the C. acnes group (p &#60; 0.05).

Author Spotlight: Development and Evaluation of a Compound Acne Rodent Model Using C. acnes and Oleic Acid

This protocol outlines the procedure for inducing acne inflammation in rat skin with oleic acid and Cutibacterium acnes.

A Rat Model of Compound Acne

Acne vulgaris is a prevalent chronic skin condition characterized by the presence of comedones, papules, and pustules on the face, neck, and chest. To ...

Nanyang Technological University

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JoVE Journal

Medicine

2.3K Views.  Capital Medical University. This protocol outlines the procedure for inducing acne inflammation in rat skin with oleic acid and Cutibacterium acnes.

Video: Author Spotlight: Development and Evaluation of a Compound Acne Rodent Model Using C. acnes and Oleic Acid

Chemical-Induced Skin Carcinogenesis Model Using Dimethylbenz[a]Anthracene and 12-O-Tetradecanoyl Phorbol-13-Acetate (DMBA-TPA)

Cancer is one of the most devastating human diseases. Experimental cancer models are important to gain insight into the complex interplay of different cell types and genes in promoting tumor progression and to provide a platform for testing the efficacy of different therapeutic approaches. One of the most commonly used experimental inflammatory cancer models is the DMBA-TPA two-stage skin carcinogenesis model. Tumor formation is induced in this model by the topical application of two different chemicals, 7,12-dimethylbenz[a]anthracene (DMBA) and 12-O-tetradecanoyl phorbol-13-acetate (TPA), that together cause papilloma formation in the skin. As the primary outcome is papilloma formation in the skin, the model is an ideal, reliable, and reproducible way to address both tumor initiation (tumor-free survival) and tumor progression (number and size of visible tumors). The effects of the DMBA-TPA treatment are transmitted via an inflammatory mechanism, which makes this model especially suitable for studying the role of the immune system in tumor formation. However, this model is restricted to the skin and other surfaces where the chemicals can be applied on. A detailed protocol is provided in this article to use the model successfully.

Chemical-Induced Skin Carcinogenesis Model Using Dimethylbenz[a]Anthracene and 12-O-Tetradecanoyl Phorbol-13-Acetate DMBA-TPA

Two-stage skin carcinogenesis is induced by two topically applied chemicals. A mutagen 7,12-dimethylbenz[a]anthracene) causes mutations in the epidermal cells and a continuous application of general growth stimulator 12-O-tetradecanoyl phorbol-13-acetate accelerates skin papilloma formation.

Cancer is one of the most devastating human diseases. Experimental cancer models are important to gain insight into the complex interplay of different ...

Cancer Research

Resolving Water, Proteins, and Lipids from In Vivo Confocal Raman Spectra of Stratum Corneum through a Chemometric Approach

Development of this in vivo confocal Raman spectroscopic method enables the direct measurement of water, proteins, and lipids with depth resolution in human subjects. This information is very important for skin-related diseases and characterizing skin care product performance. This protocol illustrates a method for confocal Raman spectra collection and the subsequent analysis of the spectral dataset leveraging chemometrics. The goal of this method is to establish a standard protocol for data collection and provide general guidance for data analysis. Preprocessing (e.g., removal of outlier spectra) is a critical step when processing large datasets from clinical studies. As an example, we provide guidance based on prior knowledge of a dataset to identify the types of outliers and develop specific strategies to remove them. A principal component analysis is performed, and the loading spectra are compared with spectra from reference materials to select the number of components used in the final multivariate curve resolution (MCR) analysis. This approach is successful for extracting meaningful information from a large spectral dataset.

Here, we present a protocol for collection of confocal Raman spectra from human subjects in clinical studies combined with chemometric approaches for spectral outlier removal and the subsequent extraction of key features.

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Chemistry

Improving 2D and 3D Skin In Vitro Models Using Macromolecular Crowding

The glycoprotein family of collagens represents the main structural proteins in the human body, and are key components of biomaterials used in modern tissue engineering. A technical bottleneck is the deposition of collagen in vitro, as it is notoriously slow, resulting in sub-optimal formation of connective tissue and subsequent tissue cohesion, particularly in skin models. Here, we describe a method which involves the addition of differentially-sized sucrose co-polymers to skin cultures to generate macromolecular crowding (MMC), which results in a dramatic enhancement of collagen deposition. Particularly, dermal fibroblasts deposited a significant amount of collagen I/IV/VII and fibronectin under MMC in comparison to controls.
The protocol also describes a method to decellularize crowded cell layers, exposing significant amounts of extracellular matrix (ECM) which were retained on the culture surface as evidenced by immunocytochemistry. Total matrix mass and distribution pattern was studied using interference reflection microscopy. Interestingly, fibroblasts, keratinocytes and co-cultures produced cell-derived matrices (CDM) of varying composition and morphology. CDM could be used as &#34;bio-scaffolds&#34; for secondary cell seeding, where the current use of coatings or scaffolds, typically from xenogenic animal sources, can be avoided, thus moving towards more clinically relevant applications.
In addition, this protocol describes the application of MMC during the submerged phase of a 3D-organotypic skin co-culture model which was sufficient to enhance ECM deposition in the dermo-epidermal junction (DEJ), in particular, collagen VII, the major component of anchoring fibrils. Electron microscopy confirmed the presence of anchoring fibrils in cultures developed with MMC, as compared to controls. This is significant as anchoring fibrils tether the dermis to the epidermis, hence, having a pre-formed mature DEJ may benefit skin graft recipients in terms of graft stability and overall wound healing. Furthermore, culture time was condensed from 5 weeks to 3 weeks to obtain a mature construct, when using MMC, reducing costs.

Improving 2D and 3D Skin In Vitro Models Using Macromolecular Crowding

We present a protocol to obtain cell-derived matrices rich in extracellular matrix proteins, using macromolecular crowders (MMC). In addition, we present a protocol which incorporates MMC in 3D organotypic skin co-culture generation, which reduces culture time while maintaining maturity of construct.

The glycoprotein family of collagens represents the main structural proteins in the human body, and are key components of biomaterials used in modern ...

Bioengineering

In Vitro Model of Human Cutaneous Hypertrophic Scarring using Macromolecular Crowding

It has been shown that in vivo tissues are highly crowded by proteins, nucleic acids, ribonucleoproteins, polysaccharides, etc. The following protocol applies a macromolecular crowding (MMC) technique to mimic this physiological crowding through the addition of neutral polymers (crowders) to cell cultures in vitro. Previous studies using Ficoll or dextran as crowders demonstrate that the expression of collagen I and fibronectin in WI38 and WS-1 cell lines are significantly enhanced using the MMC technique. However, this technique has not been validated in primary hypertrophic scar-derived human skin fibroblasts (hHSFs). As hypertrophic scarring arises from the excessive deposition of collagen, this protocol aims to construct a collagen-rich in vitro hypertrophic scar model by applying the MMC technique with hHSFs. This optimized MMC model has been shown to possess more similarities with in vivo scar tissue compared to traditional 2-dimensional (2-D) cell culture systems. In addition, it is cost-effective, time-efficient, and ethically desirable compared to animal models. Therefore, the optimized model reported here offers an advanced &#8220;in vivo-like&#8221; model for hypertrophic scar-related studies.

This protocol describes the use of macromolecular crowding to create an in vitro human hypertrophic scar tissue model that resembles in vivo conditions. When cultivated in a crowded macromolecular environment, human skin fibroblasts exhibit phenotypes, biochemistry, physiology, and functional characteristics resembling scar tissue.

It has been shown that in vivo tissues are highly crowded by proteins, nucleic acids, ribonucleoproteins, polysaccharides, etc. The following protocol ...

A Mouse Ear Model for Allergic Contact Dermatitis Evaluation

Skin is the human body&#39;s first line of defense and one of the most exposed organs to environmental chemicals. Allergic contact dermatitis (ACD) is a common skin disease that manifests as a local rash, redness, and skin lesions. The occurrence and development of ACD are influenced by both genetic and environmental factors. Although many scholars have constructed a series of models of ACD in recent years, the experimental protocols of these models are all different, which makes it difficult for readers to establish them well. Therefore, a stable and efficient animal model is of great significance to further study the pathogenesis of atopic dermatitis. In this study, we detail a modeling method using 1-fluoro-2,4-dinitrobenzene (DNFB) to induce ACD-like symptoms in the ears of mice and describe several methods for assessing the severity of dermatitis during modeling. This experimental protocol has been successfully applied in some experiments and has a certain promotional role in the field of ACD research.

Here, we describe the methods for inducing allergic contact dermatitis in mouse ears by 1-fluoro-2,4-dinitrobenzene (DNFB) and how to evaluate the severity of allergic contact dermatitis.

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Immunology and Infection

Organotypic Tissue Model Systems for Investigating Host-Pathogen Interactions In Vitro

Recapitulating the host-pathogen interface at the epithelial or mucosal barrier in vitro remains a challenging prospect for infection biologists. While in-house grown 2D epithelial monolayers lack true representation of the in vivo situation, commercially available tissue models are often overlooked due to their cost and practicality. However, with careful planning, such models provide reproducible platforms for a vast array of different applications. Here, we report the use of epithelial models that can be utilized for a wide variety of experimental purposes to investigate host-pathogen interactions in various ecological niches, such as the oral cavity, skin, and vaginal mucosa. From simple planktonic cells to complex biofilm co-culture, epithelial models are used to assess microbial adherence and invasion, and to evaluate the host response at a transcriptional and/or protein level, with scope for more detailed profiling using different omics approaches. Furthermore, these biological systems can be used as more accurate test beds for evaluating conventional and novel antimicrobial activity in a complex host-pathogen microenvironment in vitro. The protocols described herein document how models are handled upon arrival and prepared in the laboratory for co-culture stimulation with biofilm communities. The methods detail how experimental outputs are achieved from the model systems, including the processing of tissue, the co-culture setup, and data generation. These experiments include host gene expression through single- and multiplex qPCR analyses and inflammatory protein detection using ELISAs. In conclusion, epithelial models provide useful in vitro systems for preclinical investigatory studies into simple or complex host-pathogen interactions.

The present protocol outlines the application of organotypic tissue models for investigating host-pathogen interactions in vitro. Specifically, the model system described uses a multi-layered oral epithelium exposed to microorganisms associated with biofilms (dental plaque) within the context of oral health versus disease.

Recapitulating the host-pathogen interface at the epithelial or mucosal barrier in vitro remains a challenging prospect for infection biologists. While ...

Visualizing and Quantifying Pharmaceutical Compounds within Skin using Coherent Raman Scattering Imaging

Cutaneous pharmacokinetics (cPK) after topical formulation application has been a research area of particular interest for regulatory and drug development scientists to mechanistically understand topical bioavailability (BA). Semi-invasive techniques, such as tape-stripping, dermal microdialysis, or dermal open-flow microperfusion, all quantify macroscale cPK. While these techniques have provided vast cPK knowledge, the community lacks a mechanistic understanding of active pharmaceutical ingredient (API) penetration and permeation at the cellular level. 
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Multicolor Immunofluorescence of the Nasal Tissue in an Allergic Rhinitis Rat Model

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Evaluating Acupoint Catgut Embedding Therapy for Allergic Rhinitis Management

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Acupuncture Point Embedding Therapy is a comprehensive treatment method that combines modern biomaterials with acupuncture techniques. Acupoint catgut embedding (ACE) not only avoids the adverse reactions associated with Western medicine but also incorporates the benefits of traditional acupuncture, extending the duration of its therapeutic effects. Allergic rhinitis (AR) is a condition known for its challenging treatment and tendency to persist. This randomized controlled trial included 128 AR patients to evaluate the effectiveness of ACE for AR management. Data were collected at baseline, four weeks after treatment, and eight weeks after treatment. Baseline analysis was performed, and the visual analog scale (VAS) was used as a clinical observation index for this method. The rhinoconjunctivitis quality of life questionnaire (RQLQ) served as a quality of life index. Specific IgE (sIgE), IL-4, IL-10, and IL-12 were used as laboratory observation indices. The results of the experiment validate the clinical effectiveness of ACE in treating AR. Although this technique is efficient and commonly used in clinics, its invasive nature poses risks of hospital-acquired infections. Based on this experiment, this protocol refines traditional techniques, providing detailed instructions on patient preparation, operation techniques, and postoperative care to ensure the safe and effective administration of therapy. By standardizing this therapy, ACE is anticipated to become an important non-drug treatment option for alleviating symptoms in AR patients, thereby significantly enhancing their quality of life.

This protocol details the procedure for acupoint burrowing and demonstrates its effectiveness in treating allergic rhinitis.

Acupuncture Point Embedding Therapy is a comprehensive treatment method that combines modern biomaterials with acupuncture techniques. Acupoint catgut ...

A Rat Model of Compound Acne

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Chemical-Induced Skin Carcinogenesis Model Using Dimethylbenz[a]Anthracene and 12-O-Tetradecanoyl Phorbol-13-Acetate (DMBA-TPA)

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