Objective: To explore the effect of human adipose-derived stromal cells (hASCs) on the osteogenesis during the process of bone formation in vivo, and to lay the foundation of further investigations on the mechanism of in vivo osteogenesis of hASCs.
Methods: hASCs were isolated from adipose tissue by the method of collagenase digestion, and were routinely proliferated and passaged. In the in vivo study 16 nude mice were used and 4 groups were set and implanted subcutaneously into the back of nude mice: (1) blank; (2) β-tricalcium phosphate (β-TCP) scaffold only (scaffold control group); (3) β-TCP scaffold with human fibroblasts (negative cell control group); (4) β-TCP scaffold with hASCs (test group). After 1 week, 2 weeks, 4 weeks and 6 weeks of implantation, samples from the 4 nude mice were collected at each time point. Scanning electron microscope (SEM) observation and histological staining were performed to evaluate the in vivo osteogenesis of hASCs.
Results: SEM images showed that large amount of extracellular matrix (ECM) could be observed around hASCs in test group after 2 weeks of implantation. At the time point of 4 weeks, mineral deposit was found in ECM. At the time point of 6 weeks, the mineral deposit was observed to increase significantly. HE staining showed that the ECM with eosinophilic staining could be observed around hASCs after 2 weeks of implantation. At the time point of 4 weeks, newly-formed bone-like tissue could be found in ECM around the scaffold materials. At the time point of 6 weeks, more bone-like tissues were observed in ECM with typical structure of bone tissue. In comparison, no obvious mineralization and bone-like tissue were found in other groups.
Conclusion: hASCs play important roles in the process of osteogenesis in vivo, including secretion of large amount of ECM, acceleration of the mineralization of ECM and guidance for the formation of bone-like tissues.