Our long-term objective is to develop tissue engineering strategies to form orthopaedic and orthodontic tissues in vitro for transplantation. Because of the close inter-relationship between tissue matrix structure and cellular activity, we hypothesize that mechanical stimulation during ex vivo tissue formation will guide the appropriate spatial architectural and cellular patterns necessary for proper in vivo biomechanical performance. A necessary first step is to quantify the association between matrix loading and cell function, This relationship can then, in the future, be used to design appropriate in vitro loading regimens. Toward this end, we propose to conduct studies aimed at investigating the relationship between cell function and the time history of tissue loading. Briefly, we will harvest cells from rabbit temporomandibular joint discs, and culture these cells in three- dimensional gels subjected to a complex loading history that produces spatially-varying regimens of matrix compression, tension and shear. Temporal and spatial correlations will be made between measures of cell function (phenotype and matrix content) and the time history of matrix deformation (predicted mathematically using finite element analysis). The specific objectives of this feasibility study are to: 1) develop a tissue culture apparatus that can produce a spatially-varying regimen of matrix strain in gel disks uniformly seeded with cells; 2) develop a validated engineering model (using finite element analysis) to predict temporal and spatial patterns of matrix deformation and fluid flow; 3) characterize matrix composition, cell phenotype and cell gene expression within the loaded gels; and 4) use statistical models to correlate biologic outcomes with mechanical exposures and thereby test our hypothesis. We anticipate that this study will elucidate key structure-function relationships and in doing so lead to the development of improved methods for forming hydrated tissues in vitro. The scope of this study represents a new research area for the PI (tissue engineering) and initiates a collaboration between two laboratories with significant bioengineering (Lotz) and molecular biology (Kapila) expertise. Active collaboration between bioengineers and biologists is critical for successful development of tissue engineering principles. The results from this feasibility study will serve as the foundation for a center of tissue engineering emphasis at UCSF.
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