Tropoelastin incorporation into a dermal regeneration template promotes wound angiogenesis.

Severe burn injury results in substantial skin loss and cannot be treated by autografts. The Integra Dermal Regeneration Template (IDRT) is the leading synthetic skin substitute because it allows for wound bed regeneration and wound healing. However, all substitutes suffer from slow blood vessel ingrowth and would benefit considerably from enhanced vascularization to nurture tissue repair. It is shown here that by incorporating the human elastic protein tropoelastin into a dermal regeneration template (TDRT) we can promote angiogenesis in wound healing. In small and large animal models comprising mice and pigs, the hybrid TDRT biomaterial and IDRT show similar contraction to autografts and decrease wound contraction compared to open wounds. In mice, TDRT accelerates early stage angiogenesis by 2 weeks, as evidenced by increased angiogenesis fluorescent radiant efficiency in live animal imaging and the expression of endothelial cell adhesion marker CD146. In the pig, a full thickness wound repair model confirms increased numbers of blood vessels in the regenerating areas of the dermis closest to the hypodermis and immediately below the epidermis at 2 weeks post-surgery. It is concluded that including tropoelastin in a dermal regeneration template has the potential to promote wound repair through enhanced vascularization.

The effect of collagen nerve conduits filled with collagen-glycosaminoglycan matrix on peripheral motor nerve regeneration in a rat model.

BACKGROUND: Bioabsorbable unfilled synthetic nerve conduits have been used in the reconstruction of small segmental nerve defects with variable results, especially in motor nerves. We hypothesized that providing a synthetic mimic of the Schwann cell basal lamina in the form of a collagen-glycosaminoglycan (GAG) matrix would improve the bridging of the nerve gap and functional motor recovery. METHODS: A unilateral 10-mm sciatic nerve defect was created in eighty-eight male Lewis rats. Animals were randomly divided into four experimental groups: repair with reversed autograft, reconstruction with collagen nerve conduit (1.5-mm NeuraGen, Integra LifeSciences), reconstruction with collagen nerve conduit filled with collagen matrix, and reconstruction with collagen nerve conduit filled with collagen-GAG (chondroitin-6-sulfate) matrix. Nerve regeneration was evaluated at twelve weeks on the basis of the compound muscle action potential, maximum isometric tetanic force, and wet muscle weight of the tibialis anterior muscle, the ankle contracture angle, and nerve histomorphometry. RESULTS: The use of autograft resulted in significantly better motor recovery compared with the other experimental methods. Conduit filled with collagen-GAG matrix demonstrated superior results compared with empty conduit or conduit filled with collagen matrix with respect to all experimental parameters. Axon counts in the conduit filled with collagen-GAG matrix were not significantly different from those in the reversed autograft at twelve weeks after repair. CONCLUSIONS: The addition of the synthetic collagen basal-lamina matrix with chondroitin-6-sulfate into the lumen of an entubulation repair significantly improved bridging of the nerve gap and functional motor recovery in a rat model. CLINICAL RELEVANCE: Use of a nerve conduit filled with collagen-GAG matrix to bridge a motor or mixed nerve defect may result in superior functional motor recovery compared with commercially available empty collagen conduit. However, nerve autograft remains the gold standard for reconstruction of a segmental motor nerve defect.

Engineered cellular response to scaffold architecture in a rabbit trephine defect.

Tight control of pore architecture in porous scaffolds for bone repair is critical for a fully elucidated tissue response. Solid freeform fabrication (SFF) enables construction of scaffolds with tightly controlled pore architecture. Four types of porous scaffolds were constructed using SFF and evaluated in an 8-mm rabbit trephine defect at 8 and 16 weeks (n = 6): a lactide/glycolide (50:50) copolymer scaffold with 20% w/w tri-calcium phosphate and random porous architecture (Group 1); another identical design made from poly(desaminotyrosyl-tyrosine ethyl ester carbonate) [poly(DTE carbonate)], a tyrosine-derived pseudo-polyamino acid (Group 2); and two poly(DTE carbonate) scaffolds containing 500 microm pores separated by 500-microm thick walls, one type with solid walls (Group 3), and one type with microporous walls (Group 4). A commercially available coralline scaffold (Interpore) with a 486-microm average pore size and empty defects were used as controls. There was no significant difference in the overall amount of bone ingrowth in any of the devices, as found by radiographic analysis, but patterns of bone formation matched the morphology of the scaffold. These results suggest that controlled scaffold architecture can be superimposed on biomaterial composition to design and construct scaffolds with improved fill time.