Bone marrow stroma contains multipotential mesenchymal progenitor cells which can differentiate into osteoblastic cells; we refer to these cells as mesenchymal stem cells (MSCs). Basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) have been implicated in the osteogenic regulatory process by virtue of their mitogenic and differentiation activities, respectively. This study examines and compares the effects of bFGF and BMP-2 on dexamethasone (Dex)-dependent in vitro osteogenic differentiation of rat marrow-derived MSCs. A 6-day exposure to bFGF markedly stimulated cell growth and induced osteoblastic differentiation as shown by osteocalcin mRNA expression (day 14), bone nodule formation (day 18), and calcium deposition (day 18). These results indicate that bFGF enhances both mitogenic activity and osteogenic development of Dex-treated marrow MSCs. In contrast, BMP-2 did not induce osteogenesis as strongly as bFGF. Thus, exposure to BMP-2 slightly increased bone nodule number and calcium content compared with the control. Exposure of MSCs to both BMP-2 and bFGF induced expression of osteocalcin mRNA and mineralizing bone-like nodules as early as day 11 and resulted in enhancement of bone formation more markedly than either factor alone. Consistent with these results, porous calcium phosphate ceramic cubes implanted in vivo, which were loaded with MSCs pre-exposed to both bFGF and BMP-2, showed higher histologic score for bone formation than those with MSCs pre-exposed to either bFGF or BMP-2 alone. These data indicate that combined treatment with bFGF and BMP-2 synergistically enhances the osteogenic potency of bFGF in rat marrow MSC

Androgens are well known for their many functions in promoting sexual differentiation and the induction of the male phenotype. In the male, the two endogenous androgens most active in promoting these effects are testosterone and nonaromatizable 5a-dihydrotestosterone (DHT). They also play important roles in the regulation of bone metabolism. The direct effects of androgen on bone cells is suggested by the presence of androgen receptors (AR) on several human and rat established osteoblast cell lines as well as normal human osteoblast cells (HOB).1) Androgens increase rates of cellular proliferation and differentiation of osteoblasts, increase TGF-b levels, increase production of matrix proteins and inhibit osteoclast function.2,3) A role of androgens in skeletal regulation is substantiated by numerous studies in human and rodents, demonstrating that chemical or surgical castration, as well as untreated hypogonadism in men and androgen deficiency in women with hypopituitarism, lead to accelerated bone loss.2,4-7) Importantly, the deleterious effects of these conditions on bone can be reversed by treatment with androgens.One apparently unique effect of androgens is to increase periosteal bone formation in cortical bone, while estrogens depress it.8) This reflects a major gender difference in bone size, which is one of important factors determining the bone strength. A number of studies provide the proof of principle that androgens are osteoanabolic in rodents, women and men. Nonaromatizable DHT increased cortical bone volume and periosteal bone formation rates when administrated to ovariectomized rats.9) The synthetic anabolic steroids, such as nandrolone decanoate or stanozolol, have been shown to increase bone mass in postmenopausal women, possibly via stimulation of bone formation.10,11) Beneficial anabolic effects of androgens on bone in postmenopausal osteoporosis are well-documented in recent studies using combined testosterone and estrogen administration.12,13) On the other hand, bone resorption inhibitors such as estrogens, bisphosphonates, selective estrogen receptor modulators (SERMs) and calcitonin, which are still first line of treatment/prevention of osteoporosis, are not sufficient to restore bone mass for patients who have already lost a significant amount of bone. In addition, bone turnover rate differs from site to site; higher in the cancellous bone of vertebrae than in the cortical bone of the long bones. Therefore, osteoanabolic agents, which increase cortical/periosteal bone formation and bone mass of long bones, would address unmet need in the treatment of osteoporosis especially for patients with high risk of fractures. The osteoanabolic agents also complement the bone resorption inhibitors that target the cancellous bones, leading to a biomechanically favorable bone structure. 14)Despite the beneficial effects of androgens in therapies for osteoporosis, hypogonadism and other androgen deficient diseases, clinical use of them has been limited because of the undesirable virilizing (acne, hirsu...

The effect of local application of recombinant human basic fibroblast growth factor (rhbFGF) on fracture repair was examined using normal rats and streptozotocin-diabetic rats with impaired repairing ability. Immediately after fracturing the fibula, rhbFGF was applied by a single injection to the fracture site. Application of rhbFGF increased the volume and mineral content of callus in a dose-dependent manner in both normal and diabetic rats, and callus formation of diabetic rats was stimulated to levels similar to those in nontreated normal rats. The marked effect of rhbFGF on fracture repair was associated with an improvement in the mechanical properties of the healing fibula in both normal and diabetic rats. Immunohistochemical staining showed that endogenous bFGF was widely distributed in normal rats 1 and 3 weeks after fracture, especially in the soft callus and periosteum, whereas much less bFGF was detected in diabetic rats. Insulin treatment of diabetic rats restored the immunostaining for bFGF. These results demonstrate that bFGF is expressed during the early stage of fracture repair, and that the impaired fracture-repairing ability in diabetic rats is associated with reduced expression of bFGF at the fracture site. A single application of bFGF immediately after fracture not only facilitates the repair process in normal rats, but also recovers the impaired repairing ability in diabetic rats. These results suggest that local application of bFGF may facilitate bone union in patients with impaired as well as normal repairing ability.