Cell-Matrix Tensional Forces Within Cell-Dense Type I Collagen Oligomer Tissue Constructs Facilitate Rapid In Vitro Vascularization of Dense Tissue Constructs for Skin Engineering
thesisposted on 03.01.2019, 18:17 by Kevin P. Buno
The skin provides protection and maintains homeostasis, making it essential for survival. Additionally, skin has the impressive ability to grow, as observed in children as they grow into adults. However, skin functions are compromised in large skin defects, a serious problem that can be fatal. The gold standard treatment is to use an autologous skin graft; however, due to donor site morbidity and limited availability, when full-thickness defects surpass 2% total body surface area (TBSA), skin substitutes are preferred. Unfortunately, current skin substitutes on the market: are slow to revascularize (2+ weeks), have low graft survival rates (<50% take), and lead to significant scarring and contracture. Fortunately, a promising solution is to prevascularize engineered skin substitutes in vitro, which has been shown to facilitate rapid tissue integration upon grafting by providing an intact vascular network that readily connects to the host’s circulation. However, current approaches for prevascularizing tissue constructs require long in vitro culture times or implement low extracellular matrix (ECM) density tissue constructs – both which are problematic in a clinical setting. To address this, we implemented a novel multitissue interface culture model to define the design parameters that were essential for rapid vascularization of soft tissue constructs in vitro. Here, we identified endothelial colony forming cell (ECFC) density and maintenance of cell-matrix tensional forces as important factors for rapid in vitro tissue vascularization (18% vessel volume percentage after 3 days of culture). We then applied these parameters to achieve rapid in vitro vascularization of dense, oligomer tissue constructs (12, 20, and 40 mg/mL). We demonstrated, for the first time, rapid in vitro vascularization at 3 days within dense matrices (ECM concentration > 10 mg/mL). Lastly, a rat full-thickness excisional wound model was developed to determine the acellular densified oligomer’s (20 and 40 mg/mL) ability to resist wound contraction and facilitate a wound healing response (recellularization and vascularization) when grafted into wounds. Future work will implement the vascularized, dense tissue constructs into the developed animal model to assess the vascularized graft’s efficacy on treating wounds to reduce scarring and contracture outcomes.