OBJECTIVE: To investigate the effect of human adipose-derived mesenchymal stem cells (hASCs) exosomes on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) extracted from osteoporotic mice, and to evaluate the effect of hASCs exosomes on preventing bone loss induced by estrogen deficiency. METHODS: hASCs exosomes were extracted by ultracentrifugation. The osteoporotic mice were established by bilateral ovariectomy (OVX). BMSCs were isolated from osteo-porotic mice and cultured for further analysis. In the experimental group, these BMSCs were exposed to an osteogenic induction medium supplemented with hASCs exosomes to evaluate their potential effects on osteogenesis. In contrast, the control group was treated with the same osteogenic induction medium, but without the addition of hASCs exosomes, to serve as a baseline comparison for the study. To comprehensively assess the osteogenic differentiation of BMSCs influenced by hASCs exosomes, alkaline phosphatase (ALP) staining, ALP activity quantitative analysis and quantitative reverse transcription polymerase chain reaction (qPCR) were performed. These evaluations provided critical insights into the role of hASCs exosomes in promoting osteoblast differentiation and bone formation in osteoporotic conditions. The fluorescence labeled hASCs exosomes were injected via the tail vein to observe the biodistribution of exosomes. Two weeks after OVX, the mice were divided into three groups: The experimental group consisted of estrogen-deficient mice receiving hASCs exosome injections; the negative control group consisted of estrogen-deficient mice receiving phosphate-buffered saline (PBS) injections; and the positive control group consisted of mice that underwent Sham surgery and received PBS injections.The injections were administered once every 3 days, for a total of 8 injections. Afterward, the femurs were collected from the mice, and micro-computed tomography (micro-CT) was performed to measure bone mineral density and conduct bone morphometric analysis. RESULTS: hASCs exosomes were successfully extracted using ultracentrifugation. After the induction by hASCs exosomes, ALP staining and ALP activity in the BMSCs extracted from osteoporotic mice were significantly enhanced, the expression of osteogenesis related genes in BMSCs were significantly up-regulated. More trabecular bone and higher bone mineral density were observed in estrogen-deficient mice injected with hASCs exosomes compared with estrogen-deficient mice injected with PBS, and there was no significant decrease in bone mineral density compared with the Sham operation group. CONCLUSION hASCs exosomes promoted the osteogenic differentiation of BMSCs extracted from osteoporotic mice. hASCs exosomes prevented bone loss induced by estrogen deficiency.
Animals ; Mesenchymal Stem Cells/cytology* ; Exosomes ; Estrogens/deficiency* ; Humans ; Osteogenesis ; Cell Differentiation ; Female ; Mice ; Osteoporosis/prevention & control* ; Ovariectomy ; Adipose Tissue/cytology* ; Cells, Cultured

Objective:To investigate the role of bone morphogenetic protein 2/7 heterodimer (BMP-2/7)in the osteogenesis of human adipose-derived stem cells (hASCs).Methods:hASCs were exposed to three different treatments in vitro:osteogenic medium with 1 50 μg/L BMP-2/7 (experimental group), osteogenic medium alone (OM group)and proliferation medium (PM group).After 1 ,4 and 7 days of osteogenic induction,the amount of cellular DNA was measured to investigate the cytotoxicity.After 7 and 1 4 days,alkaline phosphatase (ALP)staining and quantification were performed to test the activity of ALP.After 21 and 28 days,the calcification deposition was determined by Alizarin Red S (ARS)stai-ning and quantification.The expressions of the osteoblast-related genes were tested on days 1 ,4,7 and 1 4.In the in vivo study,6 nude mice were used and 4 groups were set and implanted subcutaneously into the back of nude mice:(1 )β-TCP scaffold only (scaffold control group );(2 )β-TCP scaffold with hASCs cultured by PMin vitro for 1 week (PMcontrol group);(3)β-TCP scaffold with hASCs cultured by OM in vitro for 1 week (OM control group);(4)β-TCP scaffold with hASCs cultured by OM with 1 50 μg/L BMP-2/7 in vitro for 1 week (test group).After 4 weeks of implantation,histological staining was performed to evaluate the in vivo osteogenesis of hASCs.Results:After induction for 1 day,there was no significant difference between the experimental group and the PM group on the cellular DNA con-tent (P>0.05 ).After 4 days,the cellular DNA content increased under the stimulation of BMP-2/7 (P<0.05).On day 7,there was no significant difference among the three groups (P>0.05).ALP ac-tivity was higher by the induction of BMP-2/7 than in OMalone and PM(P<0.05).More mineraliza-tion deposition and more expressions of osteoblast-related genes such as Runx2,ALP,COL-1 A1 and OC were determined in the experimental group at different time points (P<0.05).HE staining showed that, in the test group and OM control group,the extracellular matrix (ECM)with eosinophilic staining were observed around hASCs,and newly-formed bone-like tissues could be found in ECM around the scaffold materials.Moreover,compared with the OM control group,more bone-like tissues could be observed in ECMwith typical structure of bone tissue in the test group.Masson’s trichrome staining showed that more expression of collagen could be observed in ECM in the test group compared with the other groups.There was small amount of expression of collagen in the OM and PM control groups.No obvious positive results were found in the scaffold group.Conclusion:BMP-2/7 heterodimer plays a significant role in the osteo-genesis of hASCs and is able to enhance the osteogenic differentiation of hASCs in vitro and in vivo.