Functional tissue-engineered bone-like graft made of a fibrin scaffold and TG2 gene-modified EMSCs for bone defect repair

The transplantation of tissue-engineered scaffolds with stem cells is a promising therapeutic approach for bone defect repair. To improve the therapeutic efficacy of this approach, in this study, a novel biofunctional live tissue-engineered bone-like graft was designed and constructed using a fibrin scaffold loaded with TG2 gene-modified ectomesenchymal stem cells (TG2-EMSCs) derived from nasal respiratory mucosa for bone defect repair. Autocalcification of the cell-free fibrin gel in osteogenic medium with additional alkaline phosphatase (ALP) and the osteogenic differentiation of TG2-EMSCs on the fibrin scaffold were assessed in vitro. The results indicated that the cell-free fibrin gel could autocalcify in the osteogenic medium with ALP and that the overexpression of TG2 by TG2-EMSCs could promote the osteogenic differentiation of these stem cells in the fibrin scaffold. Moreover, TG2 could enhance the deposition of extracellular matrix proteins in the fibrin scaffold, followed by calcification of the bone matrix in vitro. After transplantation into critical-sized cranial defects in rats, the functional tissue-engineered bone-like grafts improved bone regeneration. These results indicate that this tissue-engineered bone-like graft could improve the process of bone defect repair. A spongy biomaterial containing olfactory stem cells can successfully repair skull injuries in rats. Marrow-derived stem cells show promise for initiating cell growth and mineralization in studies on bone reconstruction, but harvesting these cells can be traumatic for patients. Naiyan Lu from Jiangnan University in Wuxi, China, and colleagues report that stem cells located in easy-to-access nasal cavities can also be used for next-generation bone grafts. The team genetically modified olfactory stem cells from rats to enhance differentiation into bone-forming cells, and then seeded the cells onto a porous scaffold made of fibrin proteins. Implantation experiments with rats with millimeter-scale cranial defects revealed that after four weeks, the stem cell-loaded scaffolds promoted regenerative growth of thick bone tissue. In contrast, scaffolds with non-genetically modified stem cells showed little bone growth. In this study, ectomesenchymal stem cells (EMSCs) were modified with the transglutaminase 2 (TG2) genes and tested for their ability to enhance bone regeneration on fibrin scaffold. In vitro analyses revealed that osteogenic differentiation of the EMSCs on the fibrin scaffold was promoted by TG2 expression. Transplanting fibrin scaffold loaded with TG2 gene-modified EMSC into bone defects on rat skull induced significantly faster bone regeneration compared with non-genetically modified EMSC.