PEG-Poly(l-alanine) Thermogel As a 3D scaffold of bone-marrow-derived mesenchymal stem cells

Bone-marrow-derived mesenchymal stem cells (BMSCs) were cultured in three-dimensional (3D) scaffolds formed by temperature-sensitive sol-to-gel transition of BMSC-suspended poly(ethylene glycol)-poly(l-alanine) (PEG-PA) aqueous solutions. A commercialized thermogelling 3D scaffold of Matrigel™ was used for the comparative study. The cells maintained their spherical shapes in the PEG-PA thermogel, whereas fibrous cell morphologies were observed in the Matrigel™. Type II collagen and myogenic differentiation factor 1 were dominantly expressed in the PEG-PA thermogel. On the other hand, a significant extent of type III β-tubulin was expressed in the Matrigel™ in addition to type II collagen and myogenic differentiation factor 1. After confirming the dominant chondrogenic differentiation of the BMSCs in the PEG-PA thermogel in in vitro study, in vivo study was performed for injectable tissue engineering application of the BMSCs/PEG-PA system. The cell-growing implant was formed in situ by subcutaneous injection of the BMSC-suspended PEG-PA aqueous solution to mice. In vivo study also proved the excellent expressions of chondrogenic biomarkers including collagen type II and sulfated glycosaminoglycan in the mouse model. This paper suggests that the PEG-PA thermogel is a very promising as a 3D culture matrix as well as an injectable tissue-engineering system for preferential chondrogenic differentiation of the BMSCs. Polypeptide thermogel prepared by increasing the temperature of cell suspended polymer aqueous solution to 37 °C provides an excellent 3D culture matrix of bone marrow-derived mesenchymal stem cells. Both in vitro and in vivo studies on a three-dimensional culture of the stem cells prove the preferential chondrogenic differentiation of the stem cells in the in situ formed hydrogel.