All ETDs from UAB

Advisory Committee Chair

Susan L Bellis

Advisory Committee Members

Marcas M Bamman

Steven J Thomas

Joanne E Murphy-Ullrich

Lisa M Schwiebert

Document Type

Dissertation

Date of Award

2014

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Skin is often severely damaged, resulting in the need for surgical intervention. There are many limitations to current therapies, therefore a synthetic skin graft would be invaluable for skin regeneration. The focus of the current study is on developing engineered scaffolds with embedded dermal fibroblasts that can be remodeled into native skin tissue upon implantation. To achieve this goal we created electrospun scaffolds composed of collagen I and polycaprolactone (PCL), and then introduced pores to allow fibroblast infiltration. In initial experiments performed to optimize pore size and collagen to PCL concentration, we determined that a 160 µm pore diameter, and 70:30 ratio of collagen to PCL, were ideal parameters based on favorable fibroblast responses and mechanical properties. Fibroblasts grown in these scaffolds exhibited proper morphology, rapid proliferation, and importantly, the cells secreted and filled the pores with native matrix molecules, including collagen I and fibronectin. These molecules are important for scaffold remodeling into human skin. Upon implantation, the scaffolds must support the formation of an epidermal layer: therefore, we evaluated keratinocyte growth on the scaffolds and determined that keratinocytes proliferate and stratify into an epithelial layer upon fibroblast embedded scaffolds. Scaffolds also exhibited a low rate of contraction (< 19%), which is comparable, and possibly less than, the contraction rates of current clinical graft products. Furthermore, porous scaffolds composed of 70:30 col I/PCL have degradation rates in the 3-4 week range, an appropriate time frame for degradation in vivo. Also, when placed in full-thickness rat skin wound defects these porous electrospun scaffolds enhance the skin wound healing effect as seen from H&E stained sections. Porous scaffolds had a significantly higher degree of more normal appearing dermal matrix than scaffolds not containing large induced pores. Additionally, porous electrospun scaffolds pre-seeded with fibroblasts prior to implantation further enhanced skin regenerative properties, with healed tissues resembling normal unwounded skin with a high degree of basket weave matrix, hair follicle development, and blood vessel infiltration. In conclusion, microporous electrospun scaffolds with embedded fibroblasts are promising new substrates for skin regeneration.

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