Expression of recombinant BMP-7 gene increased ossification activity in the rabbit bone mesenchymal stem cells.

OBJECTIVE: The mesenchymal stem cells (MSCs), which were distributed in the bone marrow stroma, become ideal progenitor cells in bone tissue engineering because of their convenient isolation, small injury when obtained, and strong osteogenic capacity. The osteogenic differentiation of MSCs, which is indicated by the increased alkaline phosphatase (ALP) activity and the enhanced accumulation of collagen, could be induced by a strong osteogenic capacity biological factor termed bone morphogenetic protein-7 (BMP-7). Although the chemically synthesized BMP-7 was widely applied to study the osteogenic differentiation of MSCs, transferring and expressing BMP-7 gene in target cells is more desirable, especially for gene therapy, given the advantages and convenience on the stable expression of BMP-7. The aim of this study was to determine whether recombinant BMP-7-expressing MSCs would induce bone formation in vitro. MATERIALS AND METHODS: BMP-7 gene was cloned from human placental tissue to construct a recombinant eukaryotic expression plasmid carrying BMP-7 gene by conjugating with eukaryotic expression vector pcDNA3.1. MSCs were isolated from rabbit bone marrow and cultured in vitro. Then they were divided into 3 groups: pcDNA3.1-BMP-7-transfected, pcDNA3.1-transfected, and untransfected. Human healthy fresh placental tissue was provided by the Department of Gynaecology and Obstetrics, Second Affiliated Hospital of Harbin Medical University. Written informed consent was obtained from the women. One healthy male New Zealand rabbit was provided by the Laboratory Animal Center, Harbin Medical University. RESULTS: A significant increase of ALP activity was detected in the supernatant of pcDNA3.1-BMP-7 transfected MSCs, and the enhanced collagen accumulation, which was inferred by the increased hydroxyproline content and RT-PCR. CONCLUSIONS: These results implied that BMP-7 gene was expressed in MSCs sufficiently and was involved in inducing differentiation of MSCs into osteoblast.

Expressing osteogenic growth peptide in the rabbit bone mesenchymal stem cells increased alkaline phosphatase activity and enhanced the collagen accumulation.

OBJECTIVES: The multipotent mesenchymal stem cells (MSCs) were distributed in the bone marrow stroma, and could generate all of the different skeletal cell lineages. The osteogenic differentiation of MSCs, which is indicated by the increased alkaline phosphatase (ALP) activity and the enhanced accumulation of collagen, could be induced by a tetradecapeptide termed osteogenic growth peptide (OGP). It has been hypothesized that the OGP induces the osteogenic differentiation of MSCs probably through regulating the fibroblast growth factor signaling pathways. Although the chemically synthesized OGP was widely applied to study the osteogenic differentiation of MSCs, transferring and expressing OGP gene in target cells is more desirable, especially for gene therapy, given the advantages and convenience on the stable expression of OGP. MATERIALS AND METHODS: In this study, we attempt to test the effect of OGP gene transfection; we constructed a eukaryotic expression vector, pcDNA3.1-OGP, which contained the OGP-coding DNA fragment. Subsequently, the vector was transfected into the rabbit MSCs. RESULTS: A significant increase of ALP activity was detected in the supernatant of pcDNA3.1-OGP transfected MSCs, and the enhanced collagen accumulation, which was inferred by the increased hydroxyproline content and RT-PCR. CONCLUSIONS: These results implied that transfecting the OGP-expressing vectors into MSCs might induce the osteogenic differentiation of MSCs.