[EXPERIMENTAL STUDY ON OSTEOGENIC ACTIVITY OF RABBIT BONE MARROW MESENCHYMAL STEM CELLS INDUCED BY KLD-12...

To investigate the effect of KLD-12 polypeptide complexed with recombinant human bone morphogenetic protein 2 (rhBMP-2) on osteogenic activity of rabbit bone marrow mesechymal stem cells (BMSCs).

Bone marrow was harvested from 3-month-old New Zealand white rabbit, and density gradient method was used to isolate and culture BMSCs. The third generation BMSCs were used for three-dimensional culture of KLD-12 polypetide/rhBMP-2 in vitro (experimental group) and KLD-12 polypeptide (control group). The morphology of the cells in the gel was observed by inverted phase contrast microscope at 7 days; alkaline phosphatase (ALP) and osteocalcin protein content were dectected at 3, 7, 10, 14, and 21 days; collagen type I immunofluorescence staining was done and real-time fluorescent quantitative PCR was performed to detect the relative expression of collagen type I and osteocalcin gene at 14 days.

Under the inverted phase contrast microscope, the BMSCs in the gel of the experimental group and the control group showed circular growth, and the distribution was uniform at 7 days. There was no significant difference in the expressions of ALP and osteocalcin protein content between 2 groups at 3 and 7 days (P>0.05); the above indexes in experimental group were significantly higher than those in the control group at 10-21 days (P<0.05). Laser scanning confocal microscope observation showed that immunofluorescence staining for collagen type I was positive in the experimental group, and the expression was higher than that in the control group at 14 days. Real-time fluorescence quantitative PCR detection showed that the collagen type I and osteocalcin gene expressions were significantly higher than those in the control group (t=15.902, P=0.000; t=12.998, P=0.000).

BMSCs can normally grow and proliferate in the KLD-12 polypeptide, and KLD-12 polypeptide/rhBMP-2 has good biological activity to induce BMSCs differentiation into osteoblasts.