Alginate Hydrogels with Tethered IGF-1 Mimicking Peptides to enhance the Therapeutic Potency of Mesenchymal Stem Cells for Intervertebral Disc Repair

Degeneration of the intervertebral disc (IVD) is associated with changes to tissue composition and structure that include a loss of IVD height, decreased water content and decreased cellularity. Therapies based on supplementing degenerated IVD with mesenchymal stem or progenitor cells (MSC) have been widely explored

for MSCs’ ability to secrete factors that contribute to cell survival, tissue repair and blunted inflammation. However, cells delivered without a carrier have short residence times in the tissue and are associated with a limited ability to repair the tissue. Strategies that promote MSC survival and localization in the IVD, such as

injectable cell carriers and the addition of growth factors to promote MSC survival and biosynthesis are important to enable the true potential of cellular repair strategies. We aim to develop injectable, cell adhesive and growth factor presenting alginate hydrogels that unlock the reparative potential of MSCs to repair the disc. Many engineered cell carriers seek to reproduce

the presence of cell-adhesive sites in the native extracellular matrix (ECM), by including full-length ECM proteins or short cell-adhesive peptides. Natural ECM also sequesters growth factors, including Insulin Like Growth Factor 1 (IGF-1) which promotes MSC survival and drives matrix synthesis by cells endogenous to the

IVD. We propose to modify alginate gels to present both integrin-binding cyclic RGD peptides as well as tethered short peptides that mimic IGF-1. We hypothesize that combined presentation of cyclic RGD and IGF-1 mimicking peptides from MSC-encapsulating alginate gels will protect the MSC from apoptosis and

inflammation in the hostile environment of the degenerative IVD, and enhance MSCs’ ability to promote survival and production of healthy ECM by resident cells of the IVD. We will test this hypothesis with in vitro studies of MSCs encapsulated in optimized peptide-modified alginate carriers, co-cultured with primary cells derived from human degenerative IVDs. We will also perform in vivo

studies of human MSC encapsulation in optimized peptide-modified alginate carriers for transplantation into degenerated lumbar IVDs of the RNU rat. We expect the delivery of gel-encapsulated MSCs to induce IVD repair through activation of both cell adhesive and IGF-1 signaling pathways that promote MSCs’ secretion of

cytokines for new ECM synthesis and blunted inflammation. Measures of IVD quality and single cell RNAseq will be obtained in the degenerated and treated rat IVDs to reveal the key populations and subpopulations of host cells that mediate pathology in IVD degeneration and those that are altered in response to MSC therapy.