Sequential treatment with basic fibroblast growth factor and PTH is more efficacious than treatment with PTH alone for increasing vertebral bone mass and strength in osteopenic ovariectomized rats

Combined treatment of vitamin K and teriparatide on bone metabolism and biomechanics in rats with osteoporosis

Postmenopausal osteoporosis is a degenerative disease caused by lack of estrogen whereby bone degeneration exceeds bone formation, resulting in loss of bone mass. Various drugs have been utilized in an attempt to ameliorate bone strength in such patients. The aim of the present study was to compare the effects of vitamin K or teriparatide alone and combined on bone metabolism and biomechanics in rats with osteoporosis. The ovaries of rats were excised to construct a rat model of osteoporosis. Rats were subjected to oral intake of vitamin K or subcutaneous injection of teriparatide or both for 8 weeks. ELISA was used to detect the content of carboxylated-type of osteocalcin (Gla-OC) and C-telopeptide of type I collagen (CTX-I) in serum. Bone density of shaft of femur and metaphyseal bone was measured. Three-point bending test was performed to analyze the load-deformation curve of femur. Undecalcified sections of femur were stained with toluidine blue to measure bone histomorphometric static, dynamic and bone resorption parameters. Compared with monotherapy, vitamin K combined with teriparatide significantly increased serum Gla-OC level and the number of osteoblast, decreased serum CTX-I level, reduced the number of osteoclasts and increased bone density and strength. This study showed that the efficacy of vitamin K combined with teriparatide is better than that of monotherapy. This combined treatment can promote bone formation, inhibit bone degradation, and improve bone density and strength.

Immunolocalization of FGF-2 and VEGF in rat periodontal ligament during experimental tooth movement

Objective

This article aimed at identifying the expression of fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF) in the tension and pressure areas of rat periodontal ligament, in different periods of experimental orthodontic tooth movement.

Methods

An orthodontic force of 0.5 N was applied to the upper right first molar of 18 male Wistar rats for periods of 3 (group I), 7 (group II) and 14 days (group III). The counter-side first molar was used as a control. The animals were euthanized at the aforementioned time periods, and their maxillary bone was removed and fixed. After demineralization, the specimens were histologically processed and embedded in paraffin. FGF-2 and VEGF expressions were studied through immunohistochemistry and morphological analysis.

Results

The experimental side showed a higher expression of both FGF-2 and VEGF in all groups, when compared with the control side (P < 0.05). Statistically significant differences were also found between the tension and pressure areas in the experimental side.

Conclusion

Both FGF-2 and VEGF are expressed in rat periodontal tissue. Additionally, these growth factors are upregulated when orthodontic forces are applied, thereby suggesting that they play an important role in changes that occur in periodontal tissue during orthodontic movement.

Effects of the combination of vitamin K and teriparatide on the bone metabolism in ovariectomized rats

The purpose of the present study was to evaluate the combined effects of vitamin K (VK) and teriparatide (TPTD) on bone mineral density (BMD), mechanical strength and other parameters for bone metabolism using a rat ovariectomized osteoporosis model. Ovariectomized female Sprague-Dawley rats were administered with VK (an oral dose of 30 mg/kg/day), TPTD (a subcutaneous dose of 30 µg/kg, three times a week) or a combination for 8 weeks. Thereafter, serum levels of γ-carboxylated osteocalcin (Gla-OC) were quantitated by ELISA; BMD and mechanical strength were measured by computed tomography and biomechanical testing, respectively at the femoral metaphysis. Additionally, histomorphometry was performed using the toluidine blue-stained coronal sections of distal femur. The combination of VK and TPTD clearly increased the serum levels of Gla-OC (a specific marker for bone formation) and osteoblast surface (the number of osteoblasts attaching with the surface of cancellous bone), compared to VK or TPTD alone. In addition, the combination of the two agents improved the BMD and bone strength of the femur in the ovariectomized rats, compared to VK or TPTD alone. Taken together, these findings suggest that the treatment with VK and TPTD may have a therapeutic advantage over VK or TPTD monotherapy for postmenopausal osteoporosis, possibly by enhancing the bone formation through the actions on OC and osteoblasts.

Erythroid promoter confines FGF2 expression to the marrow after hematopoietic stem cell gene therapy and leads to enhanced endosteal bone formation

Fibroblast growth factor-2 (FGF2) has been demonstrated to be a promising osteogenic factor for treating osteoporosis. Our earlier study shows that transplantation of mouse Sca-1(+) hematopoietic stem/progenitor cells that are engineered to express a modified FGF2 leads to considerable endosteal/trabecular bone formation, but it also induces adverse effects like hypocalemia and osteomalacia. Here we report that the use of an erythroid specific promoter, β-globin, leads to a 5-fold decrease in the ratio of serum FGF2 to the FGF2 expression in the marrow cavity when compared to the use of a ubiquitous promoter spleen focus-forming virus (SFFV). The confined FGF2 expression promotes considerable trabeculae bone formation in endosteum and does not yield anemia and osteomalacia. The avoidance of anemia in the mice that received Sca1(+) cells transduced with FGF2 driven by the β-globin promoter is likely due to attenuation of high-level serum FGF2-mediated stem cell mobilization observed in the SFFV-FGF2 animals. The prevention of osteomalacia is associated with substantially reduced serum Fgf23/hypophosphatemia, and less pronounced secondary hyperparathyroidism. Our improved stem cell gene therapy strategy represents one step closer to FGF2-based clinical therapy for systemic skeletal augmentation.

β-Blocker and Other Analogous Treatments that Affect Bone Mass and Sympathetic Nerve Activity in Ovariectomized Rats

We investigated whether treatments with beta-blockers or other administrations that have similar actions to β-blockers, such as Chinese herbs or needling, were effective in treating osteoporosis induced by ovariectomy (OVX). Female Wister rats were divided into five groups: a sham-operated control group treated with vehicle (Sham, n = 8), an ovariectomized (OVX) group treated with vehicle (Model, n = 8), an OVX group administered with propranolol (Pro, n = 10), an OVX group administered an ethanol extract of Fructus Citri Sarcodactylis (Fcs, n = 9), and an OVX punctured at Sanyinjiao (SP-6) and Neiguan (PC-6) (Needling, n = 8). The treatment started when rats were 12 weeks old and continued for 24 weeks. Serum osteocalcin and urinary deoxypyridinoline (Dpd) levels were upregulated in rats in response to OVX, together with a significantly decreased BMD and trabecular bone area. The Pro, Fcs and Needling treatment improved the decreased BMD and the trabecular area, increased the trabecular number, lowered the trabecular separation to some extent as well as significantly depressed the urinary Dpd levels ( p < 0.05). The bone formation markers, such as the mineralizing surface, mineral apposition rate and bone formation rate were not significantly changed, along with a slightly higher trend of osteocalcin levels when compared with the Model rats. The slower heart rate and lower plasma NE levels in these therapeutic groups were also found. Our results suggested that propranolol, Fcs and needling on Sanyinjiao (SP-6) and Neiguan (PC-6) may improve the bone mass of OVX rats, and it provides an alternative and potential therapy for the prevention of postmenopausal osteoporosis.

Preventive and Therapeutic Effects of Acupuncture on Bone Mass in Osteopenic Ovariectomized Rats

This study was designed to (1) test the preventive and therapeutic effects of acupuncture on osteopenia in ovariectomized (OVX) rats, and (2) assess whether treatment of different acupuncture points causes different effects on tibiae, femora or lumbar spines. Thirty-five female Sprague-Dawley rats were divided into four groups: Sham (sham-operated, non-acupuncture); Model (OVX, non-acupuncture); Acp-A [OVX, bilateral needling of points Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6)]; and Acp-B (OVX, bilateral needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23)). Operations were performed at 8 weeks of age, 1 week later the study was started and continued for 16 weeks. Ovariectomy resulted in decreased bone mineral density (BMD) compared to the sham group over time, and Acp-A tended to have higher BMD than the other OVX groups, especially for tibiae. In addition, the bone ash weight of the Acp groups tended to be heavier than the model group. Deoxypyridinoline, the urinary marker of bone resorption, also appeared to be decreased in both acupuncture groups. Similarly, microarchitecture and bone morphometry of lumbar vertebrae and tibiae, such as bone volume, trabecular thickness, trabecular number, mineralizing surface, bone formation rate, mineral apposition rate, number of nodes and number of node-terminus struts, also showed the same improvement in the acupuncture groups as compared to the model control group. Our findings showed that acupuncture may prevent the development of osteopenia in rats induced by ovariectomy. Needling of Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6) seems more effective than needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23) in bone anabolic regulation.

Endosseous implant anchorage is critically dependent on mechanostructural determinants of peri-implant bone trabeculae

Low bone mass is highly prevalent among patients receiving endosseous implants. In turn, the implantation prognosis in low-density skeletal sites is poor. However, little is known about the mechanostructural determinants of implant anchorage. Using metabolic manipulations that lead to low bone density and to its rescue, we show here that anchorage is critically dependent on the peri-implant bone (PIB). Titanium implants were inserted horizontally into the proximal tibial metaphysis of adult rats 6 weeks after orchiectomy (ORX) or sham ORX. Systemic intermittent administration of human parathyroid hormone (1-34) [iahPTH(1-34)] or vehicle commenced immediately thereafter for 6 weeks. The bone-implant apparatus was then subjected to image-guided failure assessment, which assesses biomechanical properties and microstructural deformation concomitantly. Anchorage failure occurred mainly in PIB trabeculae, 0.5 to 1.0 mm away from the implant. Mechanically, the anchorage performed poorly in ORX-induced low-density bone, attributable mainly to decreased trabecular number. iahPTH(1-34) rescued the PIB density and implant mechanical function by augmenting trabecular thickness (Tb.Th). However, implant biomechanical properties in low-density bone were relatively insensitive to implant surface treatment that affected only the osseointegration (%bone-implant contact). These results support a model wherein anchorage failure involves buckling of the weakest trabecular struts followed by sequential failure of the stronger trabeculae. Treatment with iahPTH(1-34) induced thicker struts, which were able to delay and even prevent failure of individual elements, thus implicating trabecular thickness as a prime target for enhancing implant anchorage by systemic bone anabolic therapy.

In vitro and in vivo evidence for stimulation of bone resorption by an EP4 receptor agonist and basic fibroblast growth factor: Implications for their efficacy as bone anabolic agents

Prostaglandin E2 receptor subtype 4 agonists (EP4A) and basic fibroblast growth factor (FGF2) stimulate bone formation, but their effects on bone resorption are controversial. To provide additional insight into the skeletal effects of EP4A and FGF2, their regulation of expression of genes associated with bone formation and resorption in aged ovariectomized (OVX) rats and in cultured mouse bone marrow cells was determined. RNA was isolated from lumbar vertebrae of OVX rats (16 months of age) treated daily for 3 weeks with FGF2 or EP4A and processed for quantitative real time-PCR analyses. mRNA expression for the receptor activator of NF-kappaB ligand (RANKL) and cathepsin K (CTSK), but not osteoprotegerin (OPG), were upregulated by both FGF2 and EP4A. Addition of FGF2 and EP4A to the medium of cultured mouse bone marrow cells increased the formation of tartrate resistant acid phosphatase (TRAP) positive cells, upregulated the expression of RANKL and CTSK, and downregulated expression for OPG. EP4A also increased the formation of actin rings, an indicator of osteoclast activation, in a dose dependent manner in osteoclasts cultured on bone slices and triggered the formation of pits as revealed by a pitting assay. Gene expression for osterix (OSX) and IGF-2, genes associated with bone formation, was significantly greater in FGF2-treated OVX rats compared with EP4A-treated OVX rats. These findings at the molecular level are consistent with previous tissue-level histomorphometric findings, and at the doses tested, support the contention that FGF2 has a stronger bone anabolic effect than EP4A. The results of these in vivo and in vitro analyses clarify the effects of FGF2 and EP4A on bone formation and resorption, and provide insight into differences in the efficacy of two potential bone anabolic agents for restoration of lost bone mass in the osteopenic, estrogen-deplete skeleton.

Treatment of experimental renal osteodystrophy with pamidronate

We evaluated the effects of the bisphosphonate pamidronate on bone histomorphometry, structure and strength in male rats with uninephrectomy or with chronic renal disease induced by 5/6 nephrectomy. In rats with chronic renal disease the plasma urea, phosphate and parathyroid hormone levels were significantly increased compared to rats with a uninephroctomy and none of these parameters was affected by pamidronate treatment. In the femoral midshaft, chronic renal disease reduced cortical bone mineral density and content. No difference was observed in the breaking load of the femoral midshaft. In the distal femur, a high-turnover renal osteodystrophy was found but pamidronate suppressed this bone turnover and increased bone mineral content. Treatment had no effect on chronic disease-induced augmentation of osteoid volume or fibroblast surface. These studies show that in this model of stage 3 renal disease, pamidronate increased mineral content in the femoral midshaft and distal metaphysis primarily by adding bone to endocortical and trabecular surfaces but did not reduce osteitis fibrosa.

Concepts of scaffold-based tissue engineering--the rationale to use solid free-form fabrication techniques

A paradigm shift is taking place in orthopaedic and reconstructive surgery from using medical devices and tissue grafts to a tissue engineering approach that uses biodegradable scaffolds combined with cells or biological molecules to repair and/or regenerate tissues. One of the potential benefits offered by solid free-form fabrication technology (SFF) is the ability to create scaffolds with highly reproducible architecture and compositional variation across the entire scaffold, due to its tightly controlled computer-driven fabrication. In this review, we define scaffold properties and attempt to provide some broad criteria and constraints for scaffold design in bone engineering.We also discuss the application-specific modifications driven by surgeon's requirements in vitro and/or in vivo. Next, we review the current use of SFF techniques in scaffold fabrication in the context of their clinical use in bone regeneration. Lastly, we comment on future developments in our groups, such as the functionalization of novel composite scaffolds with combinations of growth factors; and more specifically the promising area of heparan sulphate polysaccaride immobilization within the bone tissue engineering arena.

Sca-1+ Hematopoietic Cell–based Gene Therapy with a Modified FGF-2 Increased Endosteal/Trabecular Bone Formation in Mice

This study assessed the feasibility of using an ex vivo stem cell antigen-1-positive (Sca-1(+)) cell-based systemic fibroblast growth factor-2 (FGF-2) gene therapy to promote endosteal bone formation. Sca-1(+) cells were used because of their ability to home to, and engraft into, the bone marrow cavity. The human FGF-2 gene was modified to increase protein secretion and stability by adding the bone morphogenic protein (BMP)-2/4 hybrid signal sequence and by mutating two key cysteines. Retro-orbital injection of Sca-1(+) cells transduced with a Moloney leukemia virus (MLV)-based vector expressing the modified FGF-2 gene into sub-lethally irradiated W(41)/W(41) recipient mice resulted in long-term engraftment, more than 100-fold elevation in serum FGF-2 level, increased serum bone-formation markers, and massive endosteal bone formation. In recipient mice showing very high serum FGF-2 levels (>2,000 pg/ml), this enhanced endosteal bone formation was so robust that the marrow space was filled with bony tissues and insufficient calcium was available for the mineralization of all the newly formed bone, which led to secondary hyperparathyroidism and osteomalacia. These adverse effects appeared to be dose related. In conclusion, this study provided compelling test-of-principle evidence for the feasibility of using an Sca-1(+) cell-based ex vivo systemic FGF-2 gene therapy strategy to promote endosteal bone formation.

Systemically administered bone morphogenetic protein-6 restores bone in aged ovariectomized rats by increasing bone formation and suppressing bone resorption

Although recombinant human bone morphogenetic proteins (BMPs) are used locally for treating bone defects in humans, their systemic effect on bone augmentation has not been explored. We have previously demonstrated that demineralized bone (DB) from ovariectomized (OVX) rats cannot induce bone formation when implanted ectopically at the subcutaneous site. Here we showed in vitro that 17beta-estradiol (E2) specifically induced expression of Bmp6 mRNA in MC3T3-E1 preosteoblastic cells and that bone extracts from OVX rats lack BMPs. Next we demonstrated that 125I-BMP-6 administered systemically accumulated in the skeleton and also restored the osteoinductive capacity of ectopically implanted DB from OVX rats. BMP-6 applied systemically to aged OVX rats significantly increased bone volume and mechanical characteristics of both the trabecular and cortical bone, the osteoblast surface, serum osteocalcin and osteoprotegerin levels, and decreased the osteoclast surface, serum C-telopeptide, and interleukin-6. E2 was significantly less effective, and was not synergistic with BMP-6. Animals that discontinued BMP-6 therapy maintained bone mineral density gains for another 12 weeks. BMP-6 increased in vivo the bone expression of Acvr-1, Bmpr1b, Smad5, alkaline phosphatase, and collagen type I and decreased expression of Bmp3 and BMP antagonists, chordin and cerberus. These results show, for the first time, that systemically administered BMP-6 restores the bone inductive capacity, microarchitecture, and quality of the skeleton in osteoporotic rats.

Selected extraskeletal effects of systemic treatment with basic fibroblast growth factor in ovariectomized rats

Basic fibroblast growth factor (bFGF) is a pleiotropic mitogen with a potent bone-forming effect, rendering it a potential osteoporosis therapy. This study examined selected extraskeletal effects of bFGF in ovariectomized rats, a well-established model of human postmenopausal osteopenia, to more fully characterize side effects associated with bFGF treatment. Five-month-old, osteopenic, ovariectomized rats were injected subcutaneously with vehicle or bFGF (1 mg/kg) daily for 3 weeks. Hematologic and biochemical analyses were performed; and kidneys, livers, and proximal tibiae were examined histologically and histomorphometrically. bFGF administration resulted in anemia that was due to a shift toward granulocyte production in the bone marrow. Increased granulocyte production was also observed in the liver of bFGF-treated rats, which exhibited a markedly increased number and area of hematopoietic foci. bFGF administration also caused mild glomerular hypertrophy that was not attended by significant biochemical evidence of glomerular dysfunction. The bone anabolic effect of subcutaneous bFGF administration was confirmed in the proximal tibia, and was associated with a significant decrease in urine fractional excretion of calcium in bFGF-treated rats. Though bFGF strongly stimulates bone formation at osteopenic skeletal sites, its extraskeletal effects may restrict the long-term use of bFGF in its current form as an osteoporosis therapy.

Basic fibroblast growth factor improves trabecular bone connectivity and bone strength in the lumbar vertebral body of osteopenic rats

Recently, basic fibroblast growth factor (bFGF) has been found to increase trabecular bone mass and connectivity in the proximal tibial metaphyses (PTM) in osteopenic rats. The purpose of this study was to determine the bone anabolic effects of bFGF in the lumbar vertebral body (LVB), a less loaded skeletal site with a lower rate of bone turnover than the PTM. Six-month old female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated and untreated for 8 weeks to induce osteopenia. Then group 1 (sham) and group 2 (OVX) were treated subcutaneously (s.c.) with vehicle, and OVXed groups 3 and 4 were treated s.c. with PTH [hPTH (1-34) at 40 microg/kg, 5x/week] and bFGF (1 mg/kg, 5x/week), respectively, for 8 weeks. At sacrifice, the fifth LVB was removed, subjected to micro-CT for determination of trabecular bone structure and then processed for histomorphometry to assess bone turnover. The sixth LVB was used for mechanical compression testing (MTS, Bionix 858). The data were analyzed with the Kruskal-Wallis test followed by post-hoc testing as needed. After 16 weeks of estrogen deficiency, there were significant reductions in vertebral trabecular bone volume and trabecular thickness. Treatment with either bFGF or hPTH (1-34) increased BV/TV in OVX animals. Human PTH (1-34)-treated animals had significant increases in trabecular (48%) and cortical thickness (30%) and bone strength [maximum load (53%) and work to failure (175%)] compared to OVX + Vehicle animals. Treatment of osteopenic rats with bFGF increased bone volume (15%), trabecular thickness (13%), maximum load (45%) and work to failure (140%) compared to OVX + Vehicle animals (all P <0.05). Basic FGF increased trabecular bone volume in the lumbar vertebral body of osteopenic rats by restoring trabecular number, thickness and connectivity density. Also, bFGF improved bone mechanical properties (maximum force and work to failure) compared to the OVX + Vehicle group. Therefore, increasing the number, thickness and connections of the trabeculae contributes to increased bone strength in this small animal model of osteoporosis.

[The more efficacious acupoints of Zusanli and Sanyinjiao than that of non-acupoints on bone mass in osteopenic ovariectomized rats]

OBJECTIVE

To clarify whether the acupoints of Zusanli (ST36) and Sanyinjiao (SP6) have specific actions other than non-acupoints to bone.

METHODS

Forty Sprague-Dawley female rats were divided into five groups: Sham operated (sham) group; Ovariectomized (OVX, model) group; non-acupuncture group; OVX, needling on Zusanli and Sanyinjiao (Acp-A) group; OVX, needling on the reverse sides of Zusanli and Sanyinjiao (Acp-B) group; OVX, periostineal stimulation on the same height as points of Zusanli and Sanyinjiao (Acp-C) group. The experiment was continued for 23 weeks and then all animals were sacrificed.

RESULTS

OVX had a significantly higher body weight and lower bone mineral density (BMD) on the lumbar vertebrae, total femora and tibiae than sham rats, however, Acp-A showed a higher BMD compared with the other OVX groups. On the other hand, bone weights, bone strength and bone morphometry such as trabecular volume, trabecular separation, labeled width and bone formation rate also showed the same improvements in Acp-A as compared to the other OVX rats.

CONCLUSION

The stimulation on Zusanli and Sanyinjiao specifically prevented the development of osteopenic rats compared with non-acupoints.

Effects of basic fibroblast growth factor on osteoclasts and osteoclast-like cells

Mouse marrow, which contains osteoblast and osteoclast precursors, was grown in the presence of calcitriol and/or basic fibroblast growth factor (FGF-2). RAW 264.7 cells were differentiated into osteoclast-like cells in the presence of receptor activator of NF-kappaB-Ligand (RANK-L) and/or FGF-2. FGF-2 alone supported osteoclastogenesis in mouse marrow cultures, but not by RAW 264.7 cells alone. Although FGF-2 supported low levels of osteoclastogenesis in mouse marrow cultures, it strongly inhibited the high levels of osteoclastogenesis triggered by calcitriol. Adding excess recombinant-RANK-L to the cultures did not relieve this inhibition. After mouse marrow osteoclasts were differentiated, FGF-2 dose-dependently inhibited bone resorptive activity. FGF-2 increased the tendency of RAW 264.7 osteoclast-like cells to fuse into very large giant cells and induced reorganizations of the actin cytoskeleton in mature, RANK-L-induced RAW 264.7 osteoclast-like cells. These results suggest that FGF-2 has both direct and indirect effects on osteoclast formation and bone resorption.

Both hPTH(1-34) and bFGF increase trabecular bone mass in osteopenic rats but they have different effects on trabecular bone architecture

Osteoporosis is a syndrome of excessive skeletal fragility that results from both the loss of trabecular bone mass and trabecular bone connectivity. Recently, bFGF has been found to increase trabecular bone mass in osteoporotic rats. The purpose of this study was to compare how trabecular bone architecture, bone cell activity, and strength are altered by two different bone anabolic agents, bFGF and hPTH(1-34), in an osteopenic rat model.

MATERIALS AND METHODS

Six-month-old female Sprague-Dawley rats (n = 74) were ovariectomized (OVX) or sham-operated (sham) and maintained untreated for 2 months. Then OVX rats were subcutaneously injected with basic fibroblast factor (bFGF; 1 mg/kg, 5 days/week), human parathyroid hormone [hPTH(1-34); 40 microg/kg, 5 days/week], or vehicle for 60 days (days 60-120). Sham-operated and one group of OVX animals were injected with vehicle. Biochemical markers of bone turnover (urinary deoxypyridinoline cross-links; Quidel Corp., San Diego, CA, USA) and serum osteocalcin (Biomedical Technologies, Stroughton, MA, USA) were obtained at study days 0, 60, 90, and 120 and analyzed by ELISA. At death, the right proximal tibial metaphysis was removed, and microcomputed tomography was performed for trabecular bone structure and processed for histomorphometry to assess bone cell activity. The left proximal tibia was used for nanoindentation/mechanical testing of individual trabeculae. The data were analyzed with Kruskal Wallis and post hoc testing as needed.

RESULTS

Ovariectomy at day 60 resulted in about a 50% loss of trabecular bone volume compared with sham-treated animals. By day 120 post-OVX, OVX + vehicle treated animals had decreased trabecular bone volume, connectivity, number, and high bone turnover compared with sham-operated animals [p < 0.05 from sham-, hPTH(1-34)-, and bFGF-treated groups]. Treatment of OVX animals with bFGF and hPTH(1-34) both increased trabecular bone mass, but hPTH(1-34) increased trabecular thickness and bFGF increased trabecular number and connectivity. Histomorphometry revealed increased mineralizing surface and bone formation rate in both bFGF and hPTH(1-34) animals. However, osteoid volume was greater in bFGF-treated animals compared with both the hPTH(1-34) and OVX + vehicle animals (p < 0.05). Nanoindentation by atomic force microscope was performed on approximately 20 individual trabeculae per animal (three animals per group) and demonstrated that elastic modulus and hardness of the trabeculae in bFGF-treated animals were similar to that of the hPTH-treated and sham + vehicle-treated animals.

CONCLUSION

Both hPTH(1-34) and bFGF are anabolic agents in the osteopenic female rat. However, hPTH(1-34) increases trabecular bone volume primarily by thickening existing trabeculae, whereas bFGF adds trabecular bone mass through increasing trabecular number and trabecular connectivity. These results suggest the possibility of sequential treatment paradigms for severe osteoporosis.

Angiogenesis and marrow stromal cell fates: roles in bone strength

In vivo osteogenic responses to anabolic stimuli--whether pharmacological or mechanical--are invariably accompanied by neovascularization. Microvascular endothelial-mesenchymal interactions have emerged that provide mechanistic insight into the roles of angiogenesis in the osteoanabolic response; these interactions resemble the epithelial-mesenchymal signaling that controls tissue morphogenesis during prenatal development. Microvascular smooth muscle cells called pericytes function as multipotent mesenchymal progenitors that contribute to bone, fat, cartilage and smooth muscle formation throughout life. This abbreviated overview recounts progress made in the past decade that highlights the physiological contributions of angiogenesis to bone formation and bone strength. It highlights the need to support research that details the mechanisms whereby angiogenesis, metabolic milieu and mechanical stimuli interact to control marrow stromal cell fate during the postnatal developmental process of aging and the disease processes of musculoskeletal frailty.