Objective  To analyze the effects of bone marrow mesenchyml stem cells (BMSCs) on bone alkaline phosphatase (BALP)/C-terminal telopeptide of type-Ⅰ collagen (CTX-1) expression and mechanical dynamics in rats with osteoporotic (OP) vertebral fracture.

  Methods  A total of 60 female Sprague-Dawley rats were evenly divided into three groups, a control group that received sham operation (sham group), a group consisting of rats with OP vertebral fracture (OP group), and the last group consisting of OP vertebral fracture rats given BMSCs treatment (BMSCs group). Comparison of the three groups of animals was made in terms of bone dynamic change, bone quantitative broadband ultrasound attenuation (BUA) measurement, and bone mineral density (BMD). HE staining was done to examine the bone histological morphological parameters of the vertebral body. Serum CTX-1 and BALP levels were determined by ELISA.

  Results  Mechanical comparison showed that there were significant differences in mechanical changes of L₅ vertebra body and right femur among the three experimental groups (P<0.05). The elastic modulus and maximum load of the OP group significantly decreased compared with those of the sham group (P<0.05). After the intervention, the maximum load and elastic modulus of the BMSCs group were significantly higher than those of the OP group (P<0.05). Compared with the sham group, BUA and BMD values in the OP group were significantly downregulated (P<0.05). After intervention, BUA and BMD of the BMSCs group were significantly higher than those of the OP group and were comparable to those of the sham group (P<0.05). Compared with the sham group, the number of trabeculae in the OP group was significantly fewer, and the distribution of trabeculae was disorderly and lacked regularity. Compared with the OP group, there were more trabeculae in the BMSCs group, and their distribution was more regular. Compared with sham group, bone histological morphological parameters of the vertebral body of rats in the OP group were significantly changed--mean trabecular plate thickness (MTPT) and trabecular bone volume (TBV) parameters were significantly decreased, while mineral apposition rate (MAR) and trabecula bone surface (TRS) parameters were significantly upregulated (all P<0.05). After the experimental intervention, bone histological morphological parameters of the vertebral body in the BMSCs group showed significant improvement compared with those of the OP group (P<0.05). Compared with the sham group, serum BALP content in the OP group was greatly decreased, while the CTX-1 level was upregulated (P<0.05). After the intervention, the BMSCs group had higher serum BALP content than that of the OP group and substantially lower CTX-1 content than that of the OP group (P<0.05).

  Conclusion  BMSCs can improve the mechanical changes in rats with OP vertebral fracture, and can increase the maximum load and elastic modulus of bone tissue. In addition, BMSCs can upregulate the expression of BALP in serum and downregulate the expression of CTX-1, thus helping rats with OP vertebral fracture heal early.