Study of rrPDGF-BB gene modified BMSCs in promoting distraction osteogenesis of rat femur / 中华显微外科杂志

ABSTRACT

Objective:To investigate the therapeutic effect of rat bone marrow mesenchymal stem cells (BMSCs) transfected with recombinant rat platelet-derived growth factor BB (rrPDGF-BB) gene on the distraction osteogenesis.Methods:From October, 2019 to June, 2020, 48 batches of BMSCs were cultured from 48 young SD rats, 24 of which were transfected with rrPDGF-BB gene by lentivirus. Meanwhile, other 72 male adult SD rats were randomly selected to establish the right femoral distraction osteogenesis model. The rats were equally divided into 3 groups. PBS, BMSCs without intervention and BMSCs transfected with rrPDGF-BB gene were injected into the distraction space of each group of rats assigned as Blank group, Negative group and Experimental group, respectively. Results of the experiment were evaluated by means of imaging and immunohistochemistry. P<0.05 indicated a statistically significant difference. Results:The cultured BMSCs grew well. The expression of CD34(0.1%) and CD45(2.8%) in the third generation of BMSCs was low, and that of CD29 (95.1%) was high, which was consistent with the phenotype of BMSCs described in literatures. After transfection, the expression of green fluorescence gradually increased with the extension of transfection time, confirming the success of transfection. After 14 days, all rats reached the expected distance of distraction. The rats were observed at assigned time points in 2, 4 and 8 weeks. The photos of femur specimen showed that continuous callus could be seen in the experimental group, the hardness and colour were close to the normal bone tissue, and the activity of the distraction space was poor, which was lower than that of the blank group. X-ray examination showed that there were more new callus in the experimental group, and the bone marrow cavity was re-canalized earlier than that of the blank group; Micro-CT examination, in sagittal plane, showed that the distraction space of the experimental group healed well, the broken end was connected, and the recanalization of bone marrow cavity was earlier than that of the blank group; Micro-CT parameters of each group showed that trabecular thickness[(0.297±0.005) mm], trabecular number [(1.663±0.032) mm], bone volume fraction[(59.832±2.187)%] and bone mineral density[(0.586±0.014) g/cm 3] of the experimental group were the greatest, while trabecular separation[(0.399±0.051) mm] of the experimental group was the smallest. There was statistical difference between each group( P < 0.05); HE staining and VEGF immunohistochemistry showed that the vessels and chondrocytes formed earlier and were more in the experimental group than that in the blank group. In 8 weeks, the new callus joined into one piece under the microscope in the experimental group, and the bone marrow cavity was re-canalized with a large number of red blood cells. Conclusion:Studies have shown that BMSCs transfected with rrPDGF-BB gene can promote the formation of callus in the distraction area of rats, shorten the mineralisation time of new callus, and promote the maturation of new bone in the area of distraction osteogenesis.