Comparison the Effects of BMP-4 and BMP-7 on Articular Cartilage Repair with Bone Marrow Mesenchymal Stem Cells

Abstract

To compare the potential effects of bone morphogenetic proteins 4 and 7 (BMP-4 and BMP-7) on the chondrogenic differentiation of mesenchymal stem cells(MSCs) for articular cartilage regeneration in vitro and in vivo.In the in-vitro experiment, MSCs were derived from bone marrow. The chondrogenic effects of BMP-4 and BMP-7 were compared at the gene expression level. In the in-vivo experiment, full-thickness cartilage defects (diameter = 4 mm, thickness =3 mm) in the patellar grooves of male New Zealand white rabbits were chosen as model of in-situ cartilage repair. MSCs were treated with BMP4(group II) / BMP7 (group III) in a bilayer collagen scaffold (n=11/group). Full-thickness cartilage defects without treatment was regarded as a control (group I) (n=11). The rabbits were sacrificed at 6 and 12 weeks after operation. The repaired tissues were processed for histology and for mechanical test.In-vitro study showed increased expression levels of cartilage-related genes after MSCs were treated with BMP4 or BMP7 in culture medium. In-vivo study showed both BMP4 and BMP7 group increased new cartilage formation at 6 and 12 weeks than that of control group. BMP4 group had the largest amounts of cartilage tissue, which restored larger surface area of the cartilage defects. Moreover, BMP4 group had higher ICRS histological scores and more type II collagen in the neo-cartilage matrix than those in other two groups (p<0.05). The Young’s modulus of the repaired tissue in group III can reach 30% of normal hyaline cartilage tissue, which were significantly higher than group II and group I (p<0.05).Our data indicate that both BMP4 and BMP7 may induce MSCs chondrogenesis and increase the expression of cartilagerelated genes. BMP-4 is more potent than BM7 in inducing chondrogenesis, and more inclined to form the hyaline cartilage in vivo.KeywordsMesenchymal stem cellsBone Morphogenetic Proteins 4Bone Morphogenetic Proteins 7cartilage repairtissue engineering