The differentiation of stem cells into smooth muscle cells (SMCs) plays an important role in vascular development and remodeling. In addition, stem cells represent a potential source of SMCs for regenerative medicine applications such as constructing vascular grafts. Previous studies have suggested that various biochemical factors, including transforming growth factor-β (TGF-β) and the Notch pathway, may play important roles in vascular differentiation. However, the interactions of these two signaling pathways in the differentiation of bone marrow mesenchymal stem cells (MSCs) have not been clearly defined. In this study, we profiled the gene expression in MSCs in response to TGF-β, and showed that TGF-β induced Notch ligand Jagged 1 (JAG1) and SMC markers, including smooth muscle α-actin (ACTA2), calponin 1 (CNN1), and myocardin (MYOCD), which were dependent on the activation of SMAD3 and Rho kinase. In addition, knocking down JAG1 expression partially blocked ACTA2 and CNN1 expression and completely blocked MYOCD expression, suggesting that JAG1 plays an important role in TGF-β-induced expression of SMC markers. On the other hand, the activation of Notch signaling induced the expression of SMC markers in MSCs and human embryonic stem cells (hESCs). Notch activation in hESCs also resulted in an increase of neural markers and a decrease of endothelial markers. These results suggest that Notch signaling mediates TGF-β regulation of MSC differentiation and that Notch signaling induces the differentiation of MSCs and hESCs into SMCs, which represents a novel mechanism involved in stem cell differentiation.

Human embryonic stem cell (ESC)-derived neural cells are a potential cell source for neural tissue regeneration. Understanding the biochemical and biophysical regulation of neural differentiation and axon growth will help us develop cell therapies and bioactive scaffolds. We demonstrated that basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) had different effects on human ESC differentiation into neural cells. EGF was more effective in inducing expression of neuron and glial markers and cell extensions. In addition to biochemical cues, poly(l-lactic acid) scaffolds with aligned nanofibers increased axon growth from ESC-derived neural cells, demonstrating the significant effects of biophysical guidance at nanoscale. To combine the biochemical and biophysical cues, bFGF and EGF were either adsorbed or bound to heparin on nanofibrous scaffolds. EGF, but not bFGF, was effectively adsorbed onto nanofibers. However, adsorbed EGF and bFGF did not effectively enhance axon growth. In contrast, immobilization of bFGF or EGF onto nanofibers using heparin as the adapter molecule significantly promoted axon growth. This study elucidated the effect of bFGF and EGF in neural differentiation and axon growth, and demonstrated a method to immobilize active bFGF and EGF onto aligned nanofibers to promote neural tissue regeneration.

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Transforming growth factor-beta1 (TGF-beta1) is believed to be a key player in wound healing, promoting cell proliferation, migration, and matrix synthesis in a variety of cell types. We have designed two peptides, i.e., cytomodulin-1 (CM-1) and cytomodulin-2 (CM-2), to simulate the binding domain of TGF-beta1. In this study we examined the bioactivity of the two synthetic peptides CM-1 and CM-2 on human foreskin fibroblasts (HFF). Synthetic peptides CM-1 and CM-2 in culture media increased wound healing of fibroblasts in an injury model in vitro. In addition, CM-1 and CM-2 enhanced the gene expression of collagen I and increased the production of pro-collagen I peptide in HFF. These results suggest that CM-1 and CM-2 have potentially useful clinical applications in wound healing.