Development of clinically relevant tissue-like structures requires a three-dimensional (3D) biomaterial scaffold (within which to develop the tissues) and perfusion of culture medium (to maintain tissue viability). However, perfusion imparts mechanical stimuli (e.g., mechanical deformation of the cell membrane, tensile stress on cell-substrate and cell-cell adhesions) that can activate signaling pathways involved in proliferation and expression of differentiation markers. Further, this phenotypic response may be coupled to the chemical and topographic properties of the biomaterials scaffold, the morphology of the adherent cells, and the contractile stresses they are exerting on the substrate. However, it is intrinsically difficult to probe these cell behaviors within perfused 3D scaffolds. Therefore, we plan to study cell responses to scaffold biomaterials under perfusion using 2D model substrates.
The proposed project involves the development of a parallel-plate perfusion bioreactor to permit evaluation of osteoblastic differentiation of mesenchymal stem cells on model surfaces – that are intended to recapitulate the roughness and chemistry of porous biomaterial scaffolds – under perfusion conditions. To this end, TR&D1 will design, construct, and validate a perfusion bioreactor that can accommodate biomaterial films on coverslips. The bioreactor will circulate small volumes of medium to permit cell signaling via secreted autocrine factors (e.g., PGE2), and will permit in situ fluorescence imaging to evaluate cell behavior (e.g., morphology, viability), and deposition of osteogenic ECM proteins (e.g., BMP-2, osteocalcin).