A Mouse Model of Mechanotransduction-driven, Human-like Hypertrophic Scarring

Summary

This protocol will explain how to establish a hypertrophic scarring murine model that increases mechanotransduction signaling to simulate human-like scarring. This method involves increasing mechanical tension across a healing incision in a mouse and using a specialized device to create reproducible, excessive scar tissue for detailed histological and bioinformatic analyses.

Abstract

Hypertrophic scarring (HTS) is an abnormal process of wound healing that results in excessive scar tissue formation. Over the past decade, we have demonstrated that mechanotransduction—the conversion of mechanical stimuli into cellular responses—drives excessive fibrotic scar healing. A mouse model to assess human-like hypertrophic scarring would be an essential tool for examining various therapeutics and their ability to reduce scarring and improve healing. Specifically, our laboratory has developed a murine wound model that increases mechanical strain to promote human-like HTS. This protocol utilizes biomechanical loading devices, made from modified 13 mm palatal expanders, whose arms are placed on either side of the incision and distracted incrementally apart in order to apply continuous tension across the wound bed during healing. Over nearly two decades of use, this model has been significantly advanced to improve efficacy and reproducibility. Using the murine HTS model, significant dermal fibrotic scars can be induced to be histologically comparable to human hypertrophic scars. This murine model provides an environment to develop biologics involved in the treatment of HTS and mechanotransduction-related conditions such as foreign body response.

Introduction

Wound healing, the process by which the body attempts to repair damaged tissue and rebuild the skin barrier, can result in atypical healing if its processes of hemostasis, inflammation, proliferation, and remodeling are irregular¹. Hypertrophic scarring (HTS) is an example of irregular wound healing, characterized by excessive deposition of extracellular matrix and connective tissue at the site of injury resulting in the formation of an enlarged scar tissue area^1,2,3. Areas on the body that undergo repeated mechanical stretch stimulations, such as arou....

Protocol

Approval from the University of Arizona Institutional Animal Care and Use Committee (IACUC) was obtained for all experiments (control number: 2021-0828). This protocol uses 15-week-old C57BL/6J male mice although it could be applied to other ages and strains^9,26.

1. Creating the HTS biomechanical loading device

NOTE: Modifying the palatal expanders into the HTS device can occur at any point be.......

Discussion

The HTS mouse model is a cost-effective and highly reproducible method for inducing HTS via mechanotransduction and developing potential therapies. While there is an initial learning curve to effectively use the model, the protocol can, with practice, be performed by any researcher without surgical training. Using this model allows researchers to better understand HTS formation and the role of mechanotransduction in wound healing, which may lead to tangible improvements in patient wound care. The video demonstration acco.......

Materials

Name	Company	Catalog Number	Comments
100 mL PYREX Griffin beaker	Milipore Signma	CLS1000100
Aesculap Exacta mini trimmer	Aesculap
AutoClip System	Fine Surgical Instruments	12020-00
BD brand isopropyl alcohol swabs	Fisher Scientific	13-680-63
Buprenorphine SR (0.5 mg/mL)	Buprenex, Indivior Inc.	12496-0757-1
C57/BL6 females (6–8 weeks old)	The Jackson Laboratory	000664
Covidien sterile gauze	Fisher Scientific	2187
Covidien TelfaTM non-adherent pads	Fisher Scientific, Covidien	1961
Dental surgical ruler	DoWell Dental Products	S1070
Depilatory cream (Nair Hair Remover Lotion)	Church&Dwight, CVS	339823
Ethanol 70% solution	Fisher Scientific	64-17-5
Excel	Microsoft Cooperation	Microsoft.com	software program
ImageJ	ImageJ, Wayne Rasband	imagej.net	software program
Inhalation anesthesia system	VetEquip	922130
Iris scissors 4½ in. stainless	McKesson	43-2-104
Isoflurane, USP	Dechra Veterinary Products	17033-094-25
Kaka industrial MUB-1	Kaka Industrial	173207	Only necessary if there is no maker space or fabrication shop available
Leone Rapid Palatal Expander- 13 mm	Great Lakes Dental Technologies	125-004	The key necessary to expand and cotnract the device will come with this product in the box
Liquid repellent drape 75 x 90 cm with adhesive hole 6 x 9 cm	Omnia S.p.A.	12.T4362
Medequip Depot Silk Black Braided Sutr 6-0 Rx	Medequip Depot D707N, Fisher Scientific	NCO835822
Needle holder 5 in. with serrated jaws	McKesson	43-2-842
Prism 9	GraphPad Holdings, LLC	graphpad.com	software program
Puralube ophthalmic ointment	Dechra, NDC	17033-211-38
R studio Desktop	RStudio PBC	rstudio.com	software program
Surgical skin marker	McKesson	19-1451_BX
Tegaderm, 3 M	VWR	56222-191	foam adhesive dressing
Thermo-peep heating pad	K&H, Amazon
Tissue forceps 4¾ in. stainless 1 x 2 teeth	Mckesson	43-2-775
Vetbond (3 M)	Saint Paul, MN	1469SB