Differentiation of Neural Crest Stem Cells in Response to Matrix Stiffness and TGF-β1 in Vascular Regeneration.

The neural crest stem cells derived from human induced pluripotent stem cells (iPSC-NCSCs) are a valuable autologous cell source for tissue engineering and regenerative medicine. In this study, we investigated how iPSC-NCSCs could be regulated to regenerate arteries by microenvironmental factors, including the physical factor of matrix stiffness, and the chemical factor of transforming growth factor beta-1 (TGF-β1). We found that, compared to soft substrate, stiff substrate drove iPSC-NCSCs differentiation into smooth muscle cells, which was further enhanced by TGF-β1.

Matrix stiffness modulates the differentiation of neural crest stem cells in vivo.

Stem cells are often transplanted with scaffolds for tissue regeneration; however, how the mechanical property of a scaffold modulates stem cell fate in vivo is not well understood. Here we investigated how matrix stiffness modulates stem cell differentiation in a model of vascular graft transplantation. Multipotent neural crest stem cells (NCSCs) were differentiated from induced pluripotent stem cells, embedded in the hydrogel on the outer surface of nanofibrous polymer grafts, and implanted into rat carotid arteries by anastomosis.

Mucin covalently bonded to microfibers improves the patency of vascular grafts.

Due to high incidence of vascular bypass procedures, an unmet need for suitable vessel replacements exists, especially for small-diameter (<6 mm) vascular grafts. Here, we developed a novel, bilayered, synthetic vascular graft of 1-mm diameter that consisted of a microfibrous luminal layer and a nanofibrous outer layer, which was tailored to possess the same mechanical property as native arteries. We then chemically modified the scaffold with mucin, a glycoprotein lubricant on the surface of epithelial tissues, by either passive adsorption or covalent bonding using the di-amino-poly(ethylene glycol) linker to microfibers.

Heparin-modified small-diameter nanofibrous vascular grafts.

Due to high incidence of vascular bypass procedures, an unmet need for suitable vessel replacements exists, especially for small-diameter vascular grafts. Here we produced 1-mm diameter vascular grafts with nanofibrous structure via electrospinning, and successfully modified the nanofibers by the conjugation of heparin using di-amino-poly(ethylene glycol) (PEG) as a linker. Antithrombogenic activity of these heparin-modified scaffolds was confirmed in vitro.

Antithrombogenic modification of small-diameter microfibrous vascular grafts.

Objective: To develop small-diameter vascular grafts with a microstructure similar to native matrix fibers and with chemically modified microfibers to prevent thrombosis.

Methods And Results: Microfibrous vascular grafts (1-mm internal diameter) were fabricated by electrospinning, and hirudin was conjugated to the poly (L-lactic acid) microfibers through an intermediate linker of poly(ethylene glycol). The modified microfibrous vascular grafts were able to reduce platelet adhesion/aggregation onto microfibrous scaffolds, and immobilized hirudin suppressed thrombin activity that may interact with the scaffolds.

The effect of fiber alignment and heparin coating on cell infiltration into nanofibrous PLLA scaffolds.

Biodegradable nanofibers simulate the fibril structure of natural extracellular matrix, and provide a cell-friendly microenvironment for tissue regeneration. However, the effects of nanofiber organization and immobilized biochemical factors on cell infiltration into three-dimensional scaffolds are not well understood. For example, cell infiltration into an electrospun nanofibrous matrix is often limited due to relatively small pore size between the fibers.