Approximately 500,000 bone-grafting procedures are performed each year in the United States (Boden, 2002). Autologous iliac crest bone graft continues to be the gold standard because it provides the three essential elements for bone formation: osteoprogenitor cells, an osteoconductive matrix, and osteoinductive molecules. Iliac crest harvest is however associated with a significant number of complications and often provides an inadequate volume of graft (Gupta 2001). To address these limitations, much work has been done to improve alternative grafts with better osteoconductive matrices and exogenous delivery of osteoinductive agents such as the bone morphogenic proteins (BMP's) (Sykaras and Opperman 2003). In contrast, there are only a few basic point-of-care devices to isolate osteogenic progenitor cells, which are the third and truly essential element to foster bone healing. A device that could isolate stem cells from a bone marrow aspirate (BMA) at point of care would be of significant clinical benefit. In this phase I proposal, we will identify specific binding peptides for the multipotent subpopulation of cells in human bone marrow known as mesenchymal stem cells (MSC's), which have been shown to promote healing of bone and soft tissue (Caplan and Bruder 2001). Interfacial biomaterials (IFBM's) will be synthesized by chemically crosslinking combinations of MSC binding sequences with Affinergy's polystyrene binding sequences. These IFBM's will then be tested for their ability to bind and retain MSC's from suspensions of MSC's, suspensions of mixed cell populations, and human bone marrow aspirates. Finally, we will develop a chemical release system for bound MSC's and verify their continued viability and multipotentiality after release. These studies, upon successful completion, will validate the utility of IFBM technology in the development of a point of care stem cell isolation device. Although beyond the scope of this proposal, we envision the addition of IFBM's that bind osteogenic growth factors, which are also present in bone marrow (Barnes, Kostenuik et al. 1999), to a second generation bone marrow filtration device. This second generation device is envisioned to select and concentrate osteoinductive molecules as well as a functional population of osteoprogenitor cells. Finally, to be most effective as a timely point of care device, the entire process from drawing a marrow aspirate to re-implantation of the filtered osteogenic cells and growth factors should be as quick as possible (ideally, less than 1 hour). ? ? ?
