Spatial and temporal gene expression in chondrogenesis during fracture healing and the effects of basic fibroblast growth factor
ABSTRACT Chondrogenesis is an essential component of endochondral fracture healing, though the molecular and cellular events by which it is regulated have not been fully elucidated. In this study, we used a rat model of closed fracture healing to determine the spatial and temporal expression of genes for cartilage-specific collagens. Furthermore, to determine the effects of basic fibroblast growth factor (bFGF) on chondrogenesis in fracture healing, we injected 100 μg recombinant human bFGF into the fracture site immediately after fracture.In normal calluses, pro-(II) collagen mRNA (COL2A1) was detected in proliferative chondrocytes beginning on day 4 after the fracture, and pro-(X) collagen mRNA (COL10A1) in hypertrophic chondrocytes beginning on day 7. In FGF-injected calluses, the cartilage enlarged in size significantly. On day 14, both COL2A1-and COL10A1-expressing cells were more widely distributed, and the amounts of COL2A1 and COL10A1 mRNAs were both approximately 2-fold increased when compared with uninjected fractures. Temporal patterns of expression for these genes were, however, identical to those found in normal calluses. The number of proliferating cell nuclear antigen-positive cells was increased in the non-cartilaginous area in the bFGF-injected calluses by day 4.The present molecular analyses demonstrate that a single injection of bFGF enhances the proliferation of chondroprogenitor cells in fracture callus, and thus contributes to the formation of a larger cartilage. However, maturation of chondrocytes and replacement of the cartilage by osseous tissue are not enhanced by exogenous bFGF, and this results in the prolonged cartilaginous callus phase. We conclude that, in the healing of closed fractures of long bones, exogenous bFGF has a capacity to enlarge the cartilaginous calluses, but not to induce more rapid healing. © 2001 Orthopaedic Research Society. Punlished by Elsevier Science Ltd. All rights reserved.
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- "In closed long bone fracture, where the fracture is more likely unstable and endochondral ossification plays very important roles in its healing, FGFs can stimulate the expansion of cartilaginous callus, thus may have no or even harmful effects on the fracture healing. However, in osteotomy or stabilized fractures where the cartilaginous callus formation is very limited or absent, FGF can stimulate the proliferation of MSCs and osteoblasts, promote osteoblastic differentiation, and can lead to accelerated bone regeneration and better quality of the healed fracture (Nakajima et al., 2007, 2001b). There are 22 FGFs found so far; however, majority of them have not been studied carefully for their potential roles in fracture healing or bone regeneration. "
ABSTRACT: Fibroblast growth factor (FGF)/FGF (FGFR) signaling is an important pathway involved in skeletal development. Missense mutations in FGFs and FGFRs were found clinically to cause multiple congenital skeleton diseases including chondrodysplasia, craniosynostosis, syndromes with dysregulated phosphate metabolism. FGFs/FGFRs also have crucial roles in bone fracture repair and bone regeneration. Understanding the molecular mechanisms for the role of FGFs/FGFRs in the regulation of skeletal development, genetic skeletal diseases, and fracture healing will ultimately lead to better treatment of skeleton diseases caused by mutations of FGFs/FGFRs and fracture. This review summarizes the major findings on the role of FGF signaling in skeletal development, genetic skeletal diseases and bone healing, and discusses issues that remain to be resolved in applying FGF signaling-related measures to promote bone healing. This review has also provided a perspective view on future work for exploring the roles and action mechanisms of FGF signaling in skeletal development, genetic skeletal diseases, and fracture healing.Journal of Cellular Physiology 12/2012; 227(12):3731-43. DOI:10.1002/jcp.24083 · 3.87 Impact Factor
Gene Therapy Applications, 08/2011; , ISBN: 978-953-307-541-9
- "MLV-based retroviral FGF-2 vectors were also tested for enhancement of fracture repair. FGF-2 has been proposed to function through cell proliferation, and recombinant FGF therapy had demonstrated increased callus size (Nakajima et al., 2001). FGF-2 gene therapy stimulated proliferation of periosteal and adjacent cells of the soft callus but did not lead to the development of hard callus or accelerate bony bridging (unpublished data). "
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- "However, due to the lack of mechanical testing, the equivalent union rate does not necessarily mean that quality of osseous healing is the same in the DM and control groups. We have previously shown that basic FGF-injected fracture calluses exhibited a lower bone union rate compared to controls due to enhanced cartilage formation  . "
ABSTRACT: Most studies have focused on the association between diabetes mellitus (DM) and impaired osseous healing, but there is also evidence that diabetes impairs cartilage formation during fracture healing. To investigate the molecular mechanisms by which diabetes affects endochondral ossification, experiments were performed in a model of rat closed fracture healing complicated with diabetes. Diabetic rats were created by a single intravenous injection of streptozotocin (STZ), while controls were treated with vehicle alone. Fractures were made 2 weeks after STZ injection. Animals were killed at 4, 7, 10, 14, 21, 28 and 42 days following fracture, and samples were subject to radiographic, histological and molecular analyses. In the DM group, a significantly smaller cartilaginous callus was formed compared with controls throughout healing, with the cartilage area being reduced rapidly after day 14. When the bone union rate was evaluated radiographically on day 28, DM calluses exhibited a lower rate than controls. However, when evaluated on day 42, both groups showed an equivalent union rate. Cellular proliferation of chondroprogenitor cells and proliferating chondrocytes in soft calluses of the DM group was significantly reduced during early stages of healing (days 4 and 7), but no longer reduced thereafter. Moreover, expression levels of collagen type II, type X and osteopontin (OPN) were constantly low in the DM group. These results show the molecular basis for diminished cartilage formation and delayed union in fracture healing of the STZ-induced diabetic rats.Bone 09/2008; 43(5):832-9. DOI:10.1016/j.bone.2008.07.246 · 4.46 Impact Factor