Venous Angiogenesis and Dermal Fibroblast Augmentation of Decellularized Dermis: Towards Transplantable Dermal Substitutes

Abstract

The ability to generate vascularized tissue constructs supplied by surgically accessible vessels remains a major limitation in reconstructive tissue engineering. Previous work demonstrated that positioning porous biomaterials around a vein can induce extensive vascular sprouting and generate a vascularized tissue volume without creation of an arteriovenous loop. However, this phenomenon has principally been demonstrated using rigid calcium-phosphate scaffolds, limiting its direct relevance to soft-tissue reconstruction. Here, we investigated whether a flexible decellularized dermal matrix could similarly be vascularized around a single unmodified vein and whether autologous dermal fibroblasts could further enhance this response. Decellularized rat dermis, with or without autologous dermal fibroblast seeding, was implanted either subcutaneously in the dorsal region or around the femoral vein for 8 weeks. Following Microfil perfusion, three-dimensional micro-CT demonstrated an extensive branching vascular network within perivenous constructs. Vessel volume relative to tissue volume was 0.2 +/- 0.1% in subcutaneous constructs without fibroblasts (n = 11) and 0.6 +/- 0.2% with fibroblasts (n = 9), compared with 6.+/- 1.4 % in perivenous constructs without fibroblasts (n = 10) and 7.3+/- 1.2% with fibroblasts (n = 10). Histology and immunohistochemistry similarly showed greater cellular repopulation and substantially higher CD31- and -SMA-positive vessel densities following perivenous implantation. Integrated two-way ANOVA of the same 8-week data confirmed a dominant effect of implantation site across the vascular outcomes, while fibroblast seeding significantly affected vascular volume, dermal remodeling, and nuclear density. The effect of fibroblast seeding on vascular volume was site dependent, with a significant implantation site fibroblast interaction. At 8 weeks, the vascularized dermal construct was completely dissected free from the surrounding tissues while maintaining its connection to the femoral vein. A small superficial incision into the isolated dermis produced visible bleeding, supporting an acute functional connection of the intradermal vascular network to the host circulation while the femoral venous connection was preserved. After flap elevation, perivenous constructs retained substantially greater vascular volume and showed more complete surface healing and organized skin architecture than subcutaneous constructs. Fibroblast seeding accelerated wound closure, while its effect on post-elevation vascular volume depended on implantation site: VV/TV decreased in subcutaneous constructs but increased in perivenous constructs. These findings show that single-vein vascularization can extend from rigid calcium-phosphate biomaterials to a compliant biological extracellular-matrix scaffold and may provide a simplified axial vascularization strategy without arterialization or incorporation of an arterial vessel.