The long-term goal of this research is to elucidate the mechanisms involved in implant-induced osteolysis and the effect(s) of mechanical loading on this process. Biological training proposed in this application augmented with the applicant's engineering background, would enable the applicant to complete the research proposed herein and develop future research aimed at osteolysis. The goal of the current application is to determine the role of the substrate in enhancing the mechanoresponsiveness of osteoblastic cells and the effects of stimulated soluble factors on osteoclastic cells. Specifically, we will determine if substrate contributes to cell flattening, cell networking and cell-cell communication by analyzing these factors in communication-competent and -deficient osteoblastic cell lines on artificial and native substrates. We will then determine if these factors contribute to the mechanoresponsiveness of osteoblastic cells by quantifying fluid flow-induced cell secreted levels of osteoprotegerin (OPG) and its ligand (RANKL). Finally, we will determine if enhanced osteoblastic responsiveness is coupled to an inhibition of osteoclastogenesis and functional osteoclastic activity by quantifying OPG, RANKL and bone resorption by osteoclasts in the presence and absence of stimulated media from the osteoblastic fluid flow studies. We propose that a native substrate, relative to an artificial substrate, contributes to the mechanoresponsiveness of osteoblastic cells by promoting cell flattening, cell networking and cell-cell communication. Furthermore, we propose that coupling mechanisms exist between osteoblastic and osteoclastic cells which enable the orchestration of bone formation and resorption and that stimulation of osteoblastic activity results in an upregulation of soluble factors promoting inhibition of osteoclastogenesis and osteoclastic activity. Future work will focus on the development of in situ mechanotransduction models incorporating bone substrates. Research in this area will illuminate the mechanisms by which normal cells sense and respond to mechanical loading and the effects of the milieu in this process. This is the first step in understanding the breakdown of these mechanisms associated with disease and altered loading environments. This work has several clinically relevant applications including implant- and metastatic-induced osteolysis, osteoporosis, osteopetrosis, fracture healing and functional tissue engineering.
