There is a clear need for improved bone grafting substitutes, in particular for large defects in which complete bridging is difficult to achieve. Current clinical therapies are hampered by limited availability of autograft tissue and inconsistent effectiveness of allogeneic approaches. It has become increasingly evident that vascularization of the regenerating tissue is a main hurdle, since large defects require a concomitant blood supply to achieve complete healing. A promising recent strategy is the co-transplantation of endothelial cells (EC) and mesenchymal stem cells (MSC) to promote both blood vessel and bone formation. This proposal combines this approach with an innovative biomaterials-based system to deliver both osteogenic and vasculogenic progenitor cells locally to large bone defects. We have developed a method to embed cells in protein-based microenvironments that provide the structure and support of a 3D extracellular matrix while also presenting instructive cues through cell-matrix interactions. Importantly, these modules are in the form of discrete microbeads (200?50 ?m in diameter), which can be created and cultured separately, but can be combined and concentrated into a multi-component paste for direct delivery to bone defects, without the need to disrupt cell-matrix contacts. Our general hypothesis is that delivery of osteogenic and vasculogenic modules together as multiphase tissues will enhance in situ osteogenesis, due to paracrine interactions between the cells and their combined ability to generate vascularized bone tissue. The project has three Specific Aims. In SA1, we will create and characterize protein-based microbeads that separately promote osteogenic and vasculogenic functions of embedded cells, by systematically examining the cell and matrix compositions that are most conducive to the desired tissue-specific functions. In SA2, we will combine osteogenic and vasculogenic microbeads to create multiphase tissues and characterize tissue-specific functions in vitro, and will examine how the different module types interact in a high density culture system. In SA3, we will test our overall hypothesis and demonstrate enhanced bone formation capability of multiphase tissue constructs in vivo, using an established femoral defect model in the rat. Key endpoints include quantified measures of the rate and extent of biomechanically competent, vascularized and metabolically active bone. This project employs attractive features of modular tissue engineering and capitalizes on recent advances in our understanding of paracrine interactions between EC and MSC that are important in bone regeneration. It therefore has the potential to improve treatment of the most challenging orthopaedic defects, and could have important impact on the clinical treatment of musculoskeletal injuries.

Public Health Relevance

Healing of large bone defects is a major clinical problem, and current therapeutic options are not adequate for the most challenging cases. An important component of achieving complete healing is regenerating a vascular supply to nourish the new bone tissue. This project will apply a new and innovative approach to this problem, by creating small, modular tissue units that are designed to regenerate both bone tissue and blood vessels, and which can be combined for injection into bone defects.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR062636-05
Application #
9521351
Study Section
Musculoskeletal Tissue Engineering Study Section (MTE)
Program Officer
Wang, Fei
Project Start
2014-09-11
Project End
2019-06-30
Budget Start
2018-07-01
Budget End
2019-06-30
Support Year
5
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Biomedical Engineering
Type
Biomed Engr/Col Engr/Engr Sta
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Tiruvannamalai Annamalai, Ramkumar; Rioja, Ana Y; Putnam, Andrew J et al. (2016) Vascular Network Formation by Human Microvascular Endothelial Cells in Modular Fibrin Microtissues. ACS Biomater Sci Eng 2:1914-1925
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Hong, Xiaowei; Stegemann, Jan P; Deng, Cheri X (2016) Microscale characterization of the viscoelastic properties of hydrogel biomaterials using dual-mode ultrasound elastography. Biomaterials 88:12-24
Tiruvannamalai Annamalai, Ramkumar; Mertz, David R; Daley, Ethan L H et al. (2016) Collagen Type II enhances chondrogenic differentiation in agarose-based modular microtissues. Cytotherapy 18:263-77
Wise, Joel K; Alford, Andrea I; Goldstein, Steven A et al. (2016) Synergistic enhancement of ectopic bone formation by supplementation of freshly isolated marrow cells with purified MSC in collagen-chitosan hydrogel microbeads. Connect Tissue Res 57:516-525
Daley, Ethan Lh; Coleman, Rhima M; Stegemann, Jan P (2015) Biomimetic microbeads containing a chondroitin sulfate/chitosan polyelectrolyte complex for cell-based cartilage therapy. J Mater Chem B 3:7920-7929

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