Genetically Designed Materials for Cartilage Repair

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DESCRIPTION (provided by applicant): Maintenance of healthy intervertebral disc function depends on preservation of the anatomic integrity and function of the nucleus pulposus (NP). Aging-related cell losses leave the disc with little ability to respond to injury or aging-related changes such as loss of disc height or hydration, disc fissures or extrusion, all features associated with symptomatic intervertebral disc disorders. Cell supplementation to the disc is now of great interest, using autologous, progenitor and other cells that carry the potential to regenerate NP-like matrix in vivo. Little is known of unique and specific cellular characteristics required for regenerating NP-like matrix, however, and there are few technical strategies available to assist this goal in vitro or in vivo. We have identified unique features of immature NP cells to be their adhesion to specific laminins, and their expression of laminin-binding receptors and laminin-associated proteins. These unique features have been identified in three species (porcine, rat and human NP) and include an ability to bind to laminin-1 and laminin-10, to express both integrin and non-integrin laminin receptors, and to express a laminin associated protein. Furthermore, laminin binding protects cells from serum deprivation-induced cell apoptosis and promotes formation of extracellular matrix that uniquely contains laminin and these associated receptors. We propose to synthesize new biomaterials that promote laminin binding for primary NP cells and adult progenitor (hADAS) cells, in order to stimulate regeneration of a distinct, NP-like extracellular matrix. In Aim 1, we will select human and porcine NP cell populations for their attachment to laminin or cell-binding laminin peptides and encapsulate them in 3D polypeptide hydrogels composed of laminins and elastin-like polypeptides (ELPs). Newly synthesized matrix will be studied for its expression of specific laminin-associated and other NP matrix markers. Cell attachment strength and receptor expression will also be studied. Differences in the quantity or quality of matrix, attachment strength and receptor expression profile, amongst cell populations will be modeled using artificial neural networks and tested to determine if laminin binding promotes an enhanced capacity to regenerate the NP. In Aim 2, we will design fusion proteins of cell-binding laminin peptides and ELPs that function as 3D scaffolds. Preservation of the 3D hydrogel-forming ELP domain, together with introduction of a cell- binding domain unique to NP cells, is proposed to promote the regeneration of NP-like matrix. The significance of this work will be the design of a new cell-instructive biomaterial that, combined with a readily accessible cell source, can serve as an effective, broadly available therapeutic option for NP-like matrix regeneration for the treatment of pathological NP changes.