Robust small molecule-aided cardiac reprogramming systems selective to cardiac fibroblasts.

Direct cardiac reprogramming to induce cardiomyocyte-like cells, e.g., by GMT (Gata4, Mef2c and Tbx5), is a promising route for regenerating damaged heart in vivo and disease modeling in vitro. Supplementation with additional factors and chemical agents can enhance efficiency but raises concerns regarding selectivity to cardiac fibroblasts and complicates delivery for in situ cardiac reprogramming. Here, we screened 2000 chemicals with known biological activities and found that a combination of 2C (SB431542 and Baricitinib) significantly enhances cardiac reprogramming by GMT. Without Gata4, MT (Mef2c and Tbx5) plus 2C could selectively reprogram cardiac fibroblasts with enhanced efficiency, kinetics, and cardiomyocyte function. Moreover, 2C significantly enhanced cardiac reprogramming in human cardiac fibroblasts. 2C synergistically enhances cardiac reprogramming by inhibiting Alk5, Tyk2 and downregulating Oas2, Oas3, Serpina3n and Tgfbi. 2C enables selective and robust cardiac reprogramming that can greatly facilitate disease modeling in vitro and advance clinical therapeutic heart regeneration in vivo.

Enhancement of the chondrogenic differentiation of mesenchymal stem cells and cartilage repair by ghrelin.

Transforming growth factor beta (TGF-ß) is commonly utilized in chondrogenic differentiation protocols, but this often results in incomplete maturation of the derived chondrocytes. Gene expression analysis, quantitation of sulfated glycosaminoglycan and collagen, and histological staining were performed to assess the effects of ghrelin. The signaling pathways involved were investigated with inhibitors or targeted by shRNAs. Joint cavity delivery of TGF-ß with or without ghrelin, within a rat cartilage defect model was performed to evaluate the in vivo effects of ghrelin. Ghrelin dramatically enhanced gene expression levels of SOX9, ACAN, and COL II and resulted in increased synthesis of sulfated glycosaminoglycan (sGAG) and collagen in vitro. Combined treatment with TGF-ß and ghrelin synergistically enhanced the phosphorylation of ERK1/2 and DMNT3A, which accounted for increased expression of chondrogenic genes. Delivery of ghrelin in combination with TGF-ß after MSC implantation within a rat osteochondral defect model significantly enhanced de novo cartilage regeneration, as compared to delivery with TGF-ß alone. In conclusion, ghrelin could significantly enhance MSC chondrogenic differentiation in vitro and can also enhance cartilage regeneration in vivo when used in combination with TGF-ß. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1387-1397, 2019.