| Bone healing depends on three factors: osteoregenerative cells (mesenchymal stem cells, committed osteoblastic cells), osteoinductive proteins(growth factors) and the local environment(provided by carrier, matrix and native tissues). Tissue engineering with bioactive factors, such as bone morphogenetic proteins(BMPs),has the ability to cause a paradigm shift away from the utilisation of bone-grafting procedures currently employed in orthopedic surgery. BMPs are glycoproteins and belong to transforming growth factors beta(TGF-β) superfamily, induce the formation of cartilage and bone, play a vital role in embryonic development including brain and bone formation. Many kinds of materials of bone repair with bioactivity are developed when BMPs are recombined with different vectors in vitro, which have extensive application prospects and important signification. Now at least 20 kinds of BMPs are identified and are applied in the researchs of bone regeneration, dentale and the differentiation and growth of nephridium cells.BMP-2 is one of the most bioactive BMPs and most widely reseaching growth factors. It's most important biofunction is to induce the undifferentiation mesenchymal cells differentiation and proliferation into cartilage and new bone. The curative effect that derect and local application of BMP-2 as a bioactive protein isn't obvious because of the diffusion and immunoreaction of BMP-2. So we can transform the gene decoding BMP2 into the adaptive cells, the latter will excrete BMP2 continually and act on the target cells accoding autocrine or paracrine. This tecnology will overcome the shortcoming of the local application with exogenous cytokine. BMP-7, which is first derieved from bone matrix and its role is to adjust the formation of bone and cartilage, is a same protein named osteogenetic protein(OP-1), which is derieved from the extract of the cattle bone morphogenetic protein. BMP-7 has some characters of cell factors that make huge effect with a little dose, but actually it has some shortcomings such as degradetion with draining of body fluid, short half time period, no effect locating bony defect. It is necessary to find out a effective method instead, which can express BMP-7 steadily. The gene therapy will be a good option.The BMP-2 and -7's gene open reading frame encode a polypeptide including three peptides: signal peptide, propeptide and mature peptide. The polypeptide will form a matrue peptide with biofunction when the signal peptide and propeptide are digest by protease. Our study will clone the genes of BMP-2 and -7 from osteosarcoma cells with the technology of gene recombination and construct their expression vectors of eukarya. The eukarya expression vector pcDNA3.1(+) is used in our research.The results show that it is successful that the cloning mature peptide genes of BMP-2 and -7, and we get the recombination of BMP-2 and -7 in the eukarya expression vector. We compare cloning sequences with the entry sequence in Genebank, they are identical completely. These results will be applied in the osseous repair and cell differentiation and be the base of gene therapy using BMP-2 and BMP-7. |
