A Rat Model of Compound Acne

Summary

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

Abstract

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). 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)-α 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.

Introduction

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 challenges^2,3.

The pathogenesis of acne is multifactorial, including four critical processes: excess sebum production, comedone formation, follicular colonization by skin microbiota, and the release....

Protocol

This protocol has received ethical approval from the Beijing University of Chinese Medicine (No.2023033103-1183). Twelve male Sprague-Dawley rats (weight, 208 g ± 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

1. Measure and record the thickness of rat ears using an electronic vernier caliper (see Table .......

Discussion

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.

Materials

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