Bioactive signal gradients to engineer TMJ condyle osteochondral constructs

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DESCRIPTION (provided by applicant): The long-term objective of this application is to engineer seamless osteochondral constructs for clinical treatment of patients with degenerated joints, in particular the temporomandibular joint (TMJ). The use of a readily available, non-controversial human cell source with low immunogenicity and an FDA-approved biomaterial will facilitate the translational research phase after the core technology described in this proposal is developed. The TMJ is the focus of our attention due to the considerable morbidity of related disorders and due to the relative paucity of research attention paid to this joint that falls outside of the orthopaedic umbrella. The overall objective of this proposal is to use human umbilical cord matrix (HUCM) stem cells and microparticle technology to engineer seamless osteochondral constructs. The chief hypothesis is that using chondro-induced and osteo-induced HUCM stem cells in a novel gradient-driven scaffold design approach will lead to an osteochondral construct with superior cartilage and bony regions than either region cultured alone, resulting in a continuous transition region with a heterogeneous cartilage organization that better resembles zonal organization in native cartilage. To test this hypothesis, we propose the following specific aims: 1) to develop and characterize the novel gradient scaffold, 2) to select microparticle diameters with homogeneous scaffolds, and 3) to engineer a continuous osteochondral construct. The novel scaffolds, constructed from PLGA microparticles of discrete diameters, will be developed to provide the desired release profile of transforming growth factor-beta1 (TGF-beta1) and bone morphogenic protein-2 (BMP-2) from homogeneous scaffolds. Growth factor activity will be ensured and ability to maintain a gradient over time will then be verified. This development/characterization phase will provide an encapsulation concentration for the growth factors in the tissue engineering phase, which will begin with a study to determine an appropriate microparticle size based on separate homogeneous osteogenic and chondrogenic scaffolds. At that stage, we will create scaffolds exhibiting two distinct gradient profiles of these growth factors with opposing concentration profiles (linear or sigmoidal) within the PLGA scaffold. Signal gradients of growth factors are a fundamental part of human development and it is probable that synthetically mimicking such gradients will be beneficial to tissue engineering. Moreover, this initial commitment to osseous and cartilaginous lineages lends to mutually inductive signals between bone and cartilage cells. The proposed research presents an innovative approach to musculoskeletal tissue engineering by utilizing a new attractive cell source and creating bioactive signal gradients via novel scaffold design.