Murine Model of Wound Healing

Summary

A murine model of cutaneous wound healing that can be used to assess therapeutic compounds in physiological and pathophysiological settings.

Abstract

Wound healing and repair are the most complex biological processes that occur in human life. After injury, multiple biological pathways become activated. Impaired wound healing, which occurs in diabetic patients for example, can lead to severe unfavorable outcomes such as amputation. There is, therefore, an increasing impetus to develop novel agents that promote wound repair. The testing of these has been limited to large animal models such as swine, which are often impractical. Mice represent the ideal preclinical model, as they are economical and amenable to genetic manipulation, which allows for mechanistic investigation. However, wound healing in a mouse is fundamentally different to that of humans as it primarily occurs via contraction. Our murine model overcomes this by incorporating a splint around the wound. By splinting the wound, the repair process is then dependent on epithelialization, cellular proliferation and angiogenesis, which closely mirror the biological processes of human wound healing. Whilst requiring consistency and care, this murine model does not involve complicated surgical techniques and allows for the robust testing of promising agents that may, for example, promote angiogenesis or inhibit inflammation. Furthermore, each mouse acts as its own control as two wounds are prepared, enabling the application of both the test compound and the vehicle control on the same animal. In conclusion, we demonstrate a practical, easy-to-learn, and robust model of wound healing, which is comparable to that of humans.

Introduction

Impaired wound healing is responsible for significant morbidity and mortality worldwide; this is particularly true for sufferers of diabetes mellitus^1,2. In humans, wound healing is a continuum of processes, in which there is significant overlapping³. Immediately following wounding, inflammatory processes are initiated. Inflammatory cells release factors that encourage the processes of cell proliferation, migration and angiogenesis. After re-epithelialization and new tissue formation there is a phase of remodeling that entails both apoptosis and re-organization of matrix proteins such as collagen.

The complexity of wou....

Protocol

1. Preparation of Splints and Occlusive Dressings

1. Outline 10 mm circles on 0.5 mm thick silicone sheeting and use scissors or a biopsy punch to create silicone disks.
2. Centre a 5 mm biopsy punch in the middle of the 10 mm circle and press firmly to create a hole to form a "donut"-like disc that will be used as a splint.
3. Outline 10 mm circles on a transparent occlusive dressing such as Opsite and use scissors to create circular dressings.

2. Experimental Animals

1. Obtain Animal Ethics Committee approval for all experiments that will be performed.
2. Use 8-week old (22-26 grams) male C57B....

Results

A wound closure curve is determined by calculating the average diameter of the wound and expressing the results as a percentage, i.e. 100 - (Day 0 diameter/Day X diameter). In this experiment a therapeutic compound (or vehicle control) was applied daily to the wound. The therapeutic compound greatly accelerated wound closure (Figure 3). It is important to note that the splints must be maintained for the duration of the experiment, as removal of splints will lead to rapid wound contraction (

Discussion

This is an experimental murine model of cutaneous wound healing. A significant feature of this model is the use of silicone splints to prevent wound contraction so that re-epithelialization and new tissue formation may occur, making it similar to the process that occurs in humans. This model is versatile and can be used to assess wound healing in both physiological and pathophysiological (e.g. diabetes mellitus) settings. The model may also be used to assess potential wound healing or angiogenesis therapeutics i.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Press-to-seal silicone sheeting 0.5 mm thick	Invitrogen	P18178	Cut into "donuts" with external diameter of 1cm external, 0.5 cm internal diameter
Biopsy punch 5 mm	Steifel	BC-B1-0500	To outline wound area to be excised
Vannas scissors 8.5 cm curved	World Precision Instruments	501232	For wound incision and excision
Dumonte #7b forceps, 11 cm	World Precision Instruments	501302	To grip skin when creating incision and excising skin
Graefe forceps, serrated 10cm	World Precision Instruments	14142	To help attach silicone splint to skin
Needle holder, smooth jaws, curved, 12.5 cm	World Precision Instruments	14132
Malis forceps, smooth, straight, 12 cm	Codman and Shurtleff, Inc (J&J)	80-1500	To suture the silicon rings to the skin
Ruler, 0.5 mm gradation	n/a
Calipers 0.25 mm gradation	Duckworth and Kent	9-653	To measure wound area
Opsite FlexiFix transparent adhesive film. 10 cm x 1 m	Smith & Nephew	66030570
Rimadyl (Carprofen)	Pfizer	462986