Construct Tissue-engineered Bone By Co-seeding Marrow Stromal Cells And Endothelial Cells

Bone tissue engineering is to restore and reconstruct the bone at the defect site under the principles of tissue engineering. Since constructing tissue-engineered bone, researchers find the osteogenic progress is very slow and can't match the degradation of the scaffold. The most important reasons are: (1) Osteogenic progress of the seed cells is slow. (2) Nutritional capillary network grows into the scaffold very slowly. The seed cells can't crawl deep into the scaffold because of lack of nutritional supply, so the deposit doesn't match the degradation of the scaffold.Recently, researchers find that endothelial cells (ECs) can promote osteogenic progress and stimulate osteoblasts and osteoprecursor cells to produce vascular endothelial growth factor (VEGF) through producing bone morphogenetic protein (BMP). VEGF can stimulate proliferation of ECs and angiogenesis. So we assume that seeding marrow stromal cells (MSCs) and ECs onto biocomposite to construct tissue-engineered bone might promote osteogenesis and angiogenesis simultaneously, so as tosatisfy the nutritional need of osteogenesis.We find that under activation of ECs, MSCs (test group) produce more calcification nodules than those untreated (control group). After cultured 14 days and 21 days, respectively, The activity level of alkaline phosphatase (ALP) and osteocalcin (OCN) production of the test group are higer 2-3 times than those of the control group. These results prove that ECs can promote osteogenesis.In our in vivo studies, we seed rat marrow stromal cells (rMSCs) and human umbilical vein endothelial cells (hUVECs) onto poly(L-lactic acid)/p-tricalcium phosphate (PLLA/P-TCP) macroporous composite to be the test group, and seed rMSCs onto the same kind of composite to be the control group. We find the capillary network growth of test group is much better than that of control group, and so is the osteogenesis. These results suggest that co-seeding MSCs and ECs onto scaffold to construct tissue-engineered bone promote angiogenesis in the prosthesis, and the problem that calcification deposit can't occur deep in the prosthesis because of lack of nutritional supply might be resolved.