Inhibition of the Progression of Skin Inflammation, Fibrosis, and Vascular Injury by Blockade of the CX3 CL1/CX3 CR1 Pathway in Experimental Mouse Models of Systemic Sclerosis.

OBJECTIVE: To assess the preclinical efficacy and mechanism of action of an anti-CX3 CL1 monoclonal antibody (mAb) in systemic sclerosis (SSc). METHODS: Cultured human dermal fibroblasts were used to evaluate the direct effect of anti-CX3 CL1 mAb on fibroblasts. In addition, bleomycin-induced and growth factor-induced models of SSc were used to investigate the effect of anti-CX3 CL1 mAb on leukocyte infiltration, collagen deposition, and vascular damage in the skin. RESULTS: Anti-CX3 CL1 mAb treatment significantly inhibited Smad3 phosphorylation (P < 0.05) and expression of type I collagen and fibronectin 1 (P < 0.01) in dermal fibroblasts stimulated with transforming growth factor ß1 (TGFß1). In the bleomycin model, daily subcutaneous bleomycin injection increased serum CX3 CL1 levels (P < 0.05) and augmented lesional CX3 CL1 expression. Simultaneous administration of anti-CX3 CL1 mAb or CX3 CR1 deficiency significantly suppressed the dermal thickness, collagen content, and capillary loss caused by bleomycin (P < 0.05). Injection of bleomycin induced expression of pSmad3 and TGFß1 in the skin, which was inhibited by anti-CX3 CL1 mAb. Further, the dermal infiltration of CX3 CR1+ cells, macrophages (inflammatory and alternatively activated [M2-like] subsets), and CD3+ cells significantly decreased following anti-CX3 CL1 mAb therapy (P < 0.05), as did the enhanced skin expression of fibrogenic molecules, such as thymic stromal lymphopoietin and secreted phosphoprotein 1 (P < 0.05). However, the treatment did not significantly reduce established skin fibrosis. In the second model, simultaneous anti-mCX3 CL1 mAb therapy significantly diminished the skin fibrosis induced by serial subcutaneous injection of TGFß and connective tissue growth factor (P < 0.01). CONCLUSION: Anti-CX3 CL1 mAb therapy may be a novel approach for treating early skin fibrosis in inflammation-driven fibrotic skin disorders such as SSc.

A chondromimetic microsphere for in situ spatially controlled chondrogenic differentiation of human mesenchymal stem cells.

Human mesenchymal stem cells (hMSCs) have been identified as a viable cell source for cartilage tissue engineering. However, to undergo chondrogenic differentiation hMSCs require growth factors, in particular members of the transforming growth factor beta (TGF-ß) family. While in vitro differentiation is feasible through continuous supplementation of TGF-ß3, mechanisms to control and drive hMSCs down the chondrogenic lineage in their native microenvironment remain a significant challenge. The release of TGF-ß3 from an injectable microsphere composed of the cartilage-associated extracellular matrix molecule hyaluronan represents a readily translatable approach for in situ differentiation of hMSCs for cartilage repair. In this study, chondromimetic hyaluronan microspheres were used as a growth factor delivery source for hMSC chondrogenesis. Cellular compatibility of the microspheres (1.2 and 14.1 µm) with hMSCs was shown and release of TGF-ß3 from the most promising 14.1 µm microspheres to control differentiation of hMSCs was evaluated. Enhanced accumulation of cartilage-associated glycosaminoglycans by hMSCs incubated with TGF-ß3-loaded microspheres was seen and positive staining for collagen type II and proteoglycan confirmed successful in vitro chondrogenesis. Gene expression analysis showed significantly increased expression of the chondrocyte-associated genes, collagen type II and aggrecan. This delivery platform resulted in significantly less collagen type X expression, suggesting the generation of a more stable cartilage phenotype. When evaluated in an ex vivo osteoarthritic cartilage model, implanted hMSCs with TGF-ß3-loaded HA microspheres were detected within cartilage fibrillations and increased proteoglycan staining was seen in the tissue. In summary, data presented here demonstrate that TGF-ß3-bound hyaluronan microspheres provide a suitable delivery system for induction of hMSC chondrogenesis and their use may represent a clinically feasible tissue engineering approach for the treatment of articular cartilage defects.