Tissue engineering and regenerative medicine is a rapidly growing field striving to develop biological constructs that restore, maintain, or improve the function of a tissue or organ. While the past few decades have reported success in relatively thin non-vascularized tissues, the development of large and complex tissues requires adequate blood supply throughout the construct upon implantation. Specifically, rapid integration (~1 day) of engineered vasculature is essential to graft survival by providing nutrients and oxygen to all cells within the living construct. While many have reported successful assembly of vascular networks in vitro, vessel maturation and rapid anastomosis to host vasculature post-implantation remain significant challenges. Thus, the long-term goal of this work is to establish a prevascularized biomaterial that supports rapid host integration and subsequent perfusion. Towards this goal, the overall objective of this proposal is to understand the role of ECM physical properties, specifically fibrous microstructure, in 1) regulating the self-assembly of endothelial cells (ECs) into a mature vascular network and 2) promoting host cell invasion and integration upon implantation. Our central hypothesis is that the incorporation of fibrous structure into synthetic hydrogels will increase the rate of assembly and maturation of microvessels as well as increase host cell invasion upon implantation, both of which will lead to faster anastomosis and perfusion in vivo. Our preliminary data utilizing electrospun fibrous matrices supports this hypothesis, indicating that deformable fibrous microenvironments promote mechanical communication between ECs that underlies the formation and maturation of multicellular structures. In the first aim we will utilize 3D fiber reinforced dextran vinyl sulfone (DexVS) synthetic hydrogels to investigate the role of mechanical communication in the formation and maturation of functional microvascular networks. We will first determine optimal physical matrix conditions (e.g. bulk stiffness, fiber density) that support long range force transmission and mechanical communication by quantifying cell force mediated 3D matrix deformations. Additionally, we will utilize these results to intelligently design fibrous DexVS hydrogels that promote rapid formation of mature, functional vascular networks. Maturation of these networks will be analyzed by quantifying network morphology, strength of cell-cell junctions, and anastomoses and perfusion within a microfluidic device.
In Aim 2, we will determine the ability of prevascularized fibrous DexVS matrices to support rapid host engraftment in a SCID- mouse subcutaneous model. Implants will be dissected from mice at various time points within the first week to quantify perfusion rate of implanted vessels as well as host cell invasion into the graft. The contribution of this work is expected to be a novel synthetic fibrous biomaterial that supports rapid vessel formation and host engraftment as well as a better understanding of how biomaterial physical properties regulate the success of prevascularized tissue constructs. The information gleaned from these studies will be critical to the advancement of biomaterial design for tissue engineering and regenerative medicine applications.

Public Health Relevance

The field of tissue engineering holds great potential to develop biological constructs that restore the function of damaged tissues or organs, but recent success has been limited to thin non-vascularized tissues as the development of larger, more complex tissues requires adequate blood supply throughout the construct. One promising solution to this 3D vascularization problem is to engineer microvascular networks by self-assembly of cells within the tissue construct prior to implantation. The proposed work will utilize synthetic fibrous biomaterials to understand how matrix physical properties and cell forces regulate this self-assembly process in order to develop stable and mature prevascularized tissue constructs that support rapid engraftment with host circulation.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Predoctoral Individual National Research Service Award (F31)
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Special Emphasis Panel (ZRG1)
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Lidman, Karin Fredriksson
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University of Michigan Ann Arbor
Biomedical Engineering
Biomed Engr/Col Engr/Engr Sta
Ann Arbor
United States
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