The effects of transplantation of osteoblastic cells with bone morphogenetic protein (BMP)/carrier complex on bone repair

We investigated the effects of transplantation of osteoblastic cells with a bone morphogenetic protein (BMP)/carrier complex on bone repair by in vitr o and in vivo experiments. Poly-D,L-lactic-co-glycolic acid/gelatin sponge (PGS) was used as a carrier for cell transplantation. In the in vitro exper iments, three cell types, C3H10T1/2 cells, MC3T3-E1 cells, and primary oste oblastic cells, isolated from newborn rat calvariae (ROB cells), were cultu red for 2 weeks on PGS alone or PGS containing BMP-2 (PGS/BMP). C3H10T1/2 c ells cultured on PGS/BMP expressed several markers related to differentiati on of both osteoblasts and chondrocytes, such as alkaline phosphatase (ALP) activity and mRNAs for osteocalcin and aggrecan, whereas the cells culture d on PGS alone expressed no such markers. MC3T3-E1 cells cultured on PGS/BM P exhibited a more ALP-positive cells than those cultured on PGS alone. PGS /BMP promoted ROB cell differentiation into both osteoblasts and chondrocyt es. In the in vivo experiments, we transplanted ROB cells, which had been c ultured on PGS alone or PGS/BMP in vitro for 2 weeks, into bone defects cre ated in rat calvariae. Transplantation of ROB cells cultured on PGS alone g enerated, little new bone. Transplantation of ROB cells cultured on PGS, wh ich absorbed a low dose (10 ng) of rhBMP-2,; induced significantly higher b one mineral content than PGS/BMP alone, although application of a high dose (1 mug) of rhBMP-2 induced no difference in bone mineral content between t ransplantation of PGS/BMP with or without ROB cells. These results show tha t transplantation of osteoblastic cells after induction of osteoblast matur ation in vitro by cultivation on PGS/BMP is a potent technique for cell the rapy of bone repair. (C) 2001 by Elsevier Science Inc. All rights reserved.