Publication
Articular cartilage regeneration poses particularly tough challenges for implementing cell-based therapies. Many cell types have been investigated looking for a balanced combination of responsiveness and stability, yet techniques are still far from defining a gold standard. The work presented here focuses on the reliable expansion and characterization of a clinical-grade human epiphyseal chondro-progenitor [ECP] cell bank from a single tissue donation. ECPs were investigated at both low and high cumulative population doublings, tracking morphology, monolayer expansion kinetics and resistance to cryogenic shock. Three dimensional micro-pellet assays were used to determine spontaneous cartilage-like extracellular matrix deposition. Differentiation studies were undertaken to assess the propensity for commitment into other lineages and their stability. ECPs exhibited remarkable homogeneity in expansion with a steady proliferative potential and a stable population surface marker profile (CD14-, CD34-, CD45-, HLA-DP, DQ, DR-, and CD26+, CD44+, CD73+, CD90+, CD105+, CD166+, HLA-A,B,C+). ECPs also exhibit a stable spontaneous chondrogenic potential, depositing glycosaminoglycan rich matrix as well as Collagen I, Collagen II and display an inherent resistance to multilineage differentiation. ECPs were photoencapsulated in methacrylated hyaluronic acid hydrogels and subjected to dynamic compression. In response to 3D mechanostimulation, ECPs modulated the presentation of surface receptors for TGF|3, a potent chondrogenic morphogen. When co-encapsulated with bone marrow derived MSCs, the trend was reversed, pointing to potential crosstalk regulation between ECPs prone to shifting their baseline expression and the modulating MSCs. As a first step in defining a novel strategy for cartilage regeneration, we have conducted a GLP-grade pre-clinical safety study in goats to assess the effect of implanted ECPs in a full thickness cartilage defect. ECPs were delivered within a collagen-based matrix to optimize therapeutic cellular localization. The cell-laden construct is delivered in combination with microfracture to direct new tissue repair and remodeling. The results from the 3-months pre-clinical study highlight the safety of ECPs, the feasibility of the proposed treatment protocol as well as early indications as to their regenerative role and potential. The findings presented herein demonstrate the reliability, stability and responsiveness of Epiphyseal Chondro-Progenitor cells, granting them clear advantages for their use in defining novel strategies for cartilage regeneration.