Chondrogenesis of hMSC in affinity-bound TGF-beta scaffolds.

Herein we describe a bio-inspired, affinity binding alginate-sulfate scaffold, designed for the presentation and sustained release of transforming growth factor beta 1 (TGF-ß1), and examine its effects on the chondrogenesis of human mesenchymal stem cells (hMSCs). When attached to matrix via affinity interactions with alginate sulfate, TGF-ß1 loading was significantly greater and its initial release from the scaffold was attenuated compared to its burst release (>90%) from scaffolds lacking alginate-sulfate. The sustained TGF-ß1 release was further supported by the prolonged activation (14 d) of Smad-dependent (Smad2) and Smad-independent (ERK1/2) signaling pathways in the seeded hMSCs. Such presentation of TGF-ß1 led to hMSC chondrogenic differentiation; differentiated chondrocytes with deposited collagen type II were seen within three weeks of in vitro hMSC seeding. By contrast, in scaffolds lacking alginate-sulfate, the effect of TGF-ß1 was short-term and hMSCs could not reach a similar differentiation degree. When hMSC constructs were subcutaneously implanted in nude mice, chondrocytes with deposited type II collagen and aggrecan typical of the articular cartilage were found in the TGF-ß1 affinity-bound constructs. Our results highlight the fundamental importance of appropriate factor presentation to its biological activity, namely - inducing efficient stem cell differentiation.

Stromal cell-induced immune regulation in a transplantable lymphoid-like cell constructs.

Engineering of cell-based constructs for treating a variety of immune-related diseases by local transplantation of the cells in a pre-designed matrix is an emerging therapeutic approach, which can potentially reduce the side effects associated with systemic cell injection. Stromal cells have been shown to exert immunosuppressive properties and thus can be exploited for autoimmune regulation and cell transplantation. Here, we demonstrate the fabrication of a stromal cell-based construct, which serves as a lymphoid-like organ with immune regulatory characteristics. In the proposed system, stromal cells are co-seeded with dendritic cells (DC) in a macro-porous alginate scaffold containing the encephalitogenic myelin-derived peptide, proteolipid protein (PLP). We demonstrate that the presence of stromal cells attenuates DC maturation upon lipopolysaccharide stimulus. In vitro, we show that while the migration of pathogenic PLP-specific T cells to construct cultivated with or without stromal cells does not differ, their activation and proliferation are significantly suppressed in the presence of stromal cells. Upon in vivo transplantation, under the kidney capsule of mice, the pathogenic activation and proliferation of T cells which were drawn into the construct were suppressed in the co-seeded constructs. This system thus serves as a lymphoid-like organ with regulatory characteristics, which can be applied for local tolerance induction, for application in cell transplantations as well as autoimmune diseases.