Bone anabolic effects of subcutaneous treatment with basic fibroblast growth factor alone and in combination with estrogen in osteopenic ovariectomized rats

17β-Estradiol alleviates intervertebral disc degeneration by inhibiting NF-κB signal pathway

AIM

To investigate the effect of 17β-Estradiol (E2) on intervertebral disc degeneration (IVDD) and the related mechanism.

MATERIALS AND METHODS

Immunohistochemistry was used to detect the expression of estrogen receptor β (ERβ) within intervertebral discs of humans and rats. After that, rat IVDD model was established by needle puncture and bilateral ovariectomy. Then, the serum E2 level was detected by enzyme linked immunosorbent assay, and the degree of IVDD was evaluated by X-ray, magnetic resonance imaging, hematoxylin and eosin staining, and Safranin O-Fast Green staining. Finally, we used immunohistochemistry and immunofluorescence staining to determine the effect of E2 on nuclear factor kappa-B (NF-κB) signal pathway both in vivo and in vitro.

KEY FINDINGS

We identified that IVDD was associated with lower levels of ERβ and ERβ levels were inversely correlated with IVDD. The histological staining and radiological results showed that E2 supplement could alleviate IVDD progression. Additionally, immunohistochemistry staining demonstrated that E2 could inhibit nucleus pulposus cell (NPC) apoptosis, matrix metalloproteinases (MMPs) synthesis, and degradation of extracellular matrix (ECM) by inhibiting the activation of NF-κB signal pathway. Furthermore, immunofluorescence staining showed that the above effects of E2 on the NF-κB signal pathway could be blocked by the estrogen receptor antagonist ICI182780 in vitro. Finally, inhibition of NF-κB signal pathway by BAY11-7082 could reduce MMPs synthesis and ECM degradation of NPCs.

SIGNIFICANCE

Collectively, these findings indicated that E2 could effectively ameliorate IVDD by inhibiting NPC apoptosis via inhibition of NF-κB signal pathway.

Opposing effects of Sca-1(+) cell-based systemic FGF2 gene transfer strategy on lumbar versus caudal vertebrae in the mouse

Our previous work showed that a Sca-1⁺ cell-based FGF2 therapy was capable of promoting robust increases in trabecular bone formation and connectivity on the endosteum of long bones. Past work reported that administration of FGF2 protein promoted bone formation in red marrow but not in yellow marrow. The issue as to whether the Sca-1⁺ cell-based FGF2 therapy is effective in yellow marrow is highly relevant to its clinical potential for osteoporosis, as most red marrows in a person of an advanced age, are converted to yellow marrows. Accordingly, this study sought to compare the osteogenic effects of this stem cell-based FGF2 therapy on red marrow-filled lumbar vertebrae with those on yellow marrow-filled caudal vertebrae of young adult W⁴¹/W⁴¹ mice. The Sca-1⁺ cell-based FGF2 therapy drastically increased trabecular bone formation in lumbar vertebrae, but the therapy not only did not promote bone formation but instead caused substantial loss of trabecular bone in caudal vertebrae. The lack of an osteogenic response was not due to insufficient engraftment of FGF2-expressing Sca-1⁺ cells or inadequate FGF2 expression in caudal vertebrae. Previous studies have demonstrated that recipient mice of this stem cell-based FGF2 therapy developed secondary hyperparathyroidism and increased bone resorption. Thus, the loss of bone mass in caudal vertebrae might in part be due to an increase in resorption without a corresponding increase in bone formation. In conclusion, the Sca-1⁺ cell-based FGF2 therapy is osteogenic in red marrow but not in yellow marrow.

Local drug delivery for enhancing fracture healing in osteoporotic bone

Fragility fractures can cause significant morbidity and mortality in patients with osteoporosis and inflict a considerable medical and socioeconomic burden. Moreover, treatment of an osteoporotic fracture is challenging due to the decreased strength of the surrounding bone and suboptimal healing capacity, predisposing both to fixation failure and non-union. Whereas a systemic osteoporosis treatment acts slowly, local release of osteogenic agents in osteoporotic fracture would act rapidly to increase bone strength and quality, as well as to reduce the bone healing period and prevent development of a problematic non-union. The identification of agents with potential to stimulate bone formation and improve implant fixation strength in osteoporotic bone has raised hope for the fast augmentation of osteoporotic fractures. Stimulation of bone formation by local delivery of growth factors is an approach already in clinical use for the treatment of non-unions, and could be utilized for osteoporotic fractures as well. Small molecules have also gained ground as stable and inexpensive compounds to enhance bone formation and tackle osteoporosis. The aim of this paper is to present the state of the art on local drug delivery in osteoporotic fractures. Advantages, disadvantages and underlying molecular mechanisms of different active species for local bone healing in osteoporotic bone are discussed. This review also identifies promising new candidate molecules and innovative approaches for the local drug delivery in osteoporotic bone.

Active-resisted stance modulates regional bone mineral density in humans with spinal cord injury

OBJECTIVE

In people with spinal cord injury (SCI), active-resisted stance using electrical stimulation of the quadriceps delivered a therapeutic stress to the femur (∼150% of body weight) and attenuated bone mineral density (BMD) decline. In standard densitometry protocols, BMD is averaged over the entire bone cross-section. An asymmetric adaptation to mechanical load may be masked by non-responding regions. The purpose of this study was to test a novel method to assess regional BMD of the femur in individuals with SCI. We hypothesize that there will be regional bone-sparing changes as a result of active-resisted stance.

DESIGN

Mixed cross-sectional and longitudinal.

SETTING

Research laboratory.

PARTICIPANTS

Twelve individuals with SCI and twelve non-SCI controls.

INTERVENTION

Individuals with SCI experienced active-resisted stance or passive stance for up to 3 years.

OUTCOME MEASURES

Peripheral quantitative computed tomography images from were partitioned so that femur anatomic quadrants could be separately analyzed.

RESULTS

Over 1.5 years, the slope of BMD decline over time was slower at all quadrants for the active-resisted stance limbs. At >2 years of training, BMD was significantly higher for the active-resisted stance group than for the passive stance group (P = 0.007). BMD was preferentially spared in the posterior quadrants of the femur with active-resisted stance.

CONCLUSIONS

A regional measurement technique revealed asymmetric femur BMD changes between passive stance and active-resisted stance. Future studies are now underway to better understand other regional changes in BMD after SCI.

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.

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.

Controlled release of heparin-binding growth factors using heparin-containing particulate systems for tissue regeneration

The strategy of growth factor delivery to specific sites for therapeutic applications has been considered an essential process in biomedical fields despite some obstacles, such as a non-controlled release with initial burst. This article focuses on particulate systems using heparin for the controlled delivery of heparin-binding growth factors (HBGFs), an emerging area in the tissue engineering field. Since heparin has been widely utilized for growth factor delivery due to its electrostatic nature and specific affinity with HBGFs, heparin-containing polymeric particulates can be utilized as functional carriers to deliver growth factors in a controlled manner. In particular, examples of the HBGF delivery systems containing heparin, perspectives and potential applications are described and discussed.

Expression and synthesis of bone morphogenetic proteins by osteoclasts: a possible path to anabolic bone remodeling

Skeletal remodeling is a finely orchestrated process coupling bone formation to bone resorption. The dynamics of coupling is regulated by the microenvironment at the bone remodeling site, which in turn is influenced by the intercellular communication between cells like osteoclasts and osteoblasts. Understanding the dynamics of coupling is important in devising new therapeutic approaches to the treatment of skeletal diseases characterized by disturbances in the bone remodeling process. In this study, we report the localization of bone morphogenetic proteins (BMPs) in osteoclasts generated from primary cocultures of bone marrow cells from mouse femur and tibia with mouse calvarial osteoblasts, using immunocytochemistry and in situ hybridization. Positive staining was seen in osteoclasts for BMP-2, -4, -6, and -7. Real-time PCR was used to quantitatively confirm the expression of transcripts for BMP-2, BMP-4, and BMP-6 mRNA in murine osteoclasts. Finally, the presence of BMP-2, -4, -6, and-7 proteins was confirmed in osteoclast lysates by Western blotting. Overall, our data suggest a possible direct role for osteoclasts in promoting bone formation via expression and synthesis of BMPs, which then would play an important role in promoting the recruitment, proliferation, and differentiation of osteoblasts at bone resorption sites.

Effects of FGF-2 release from a hydrogel polymer on bone mass and microarchitecture

Bone substitutes are widely used for filling and restoring bone defects. Among them, methacrylic polymers are employed in load-bearing bones to seal hip prostheses. Incorporation of growth factors into a polymer device could be a way to enhance bone growth. In the present study, we evaluated the capacity of poly(2-hydroxyethyl methacrylate) - pHEMA - copolymerized with 2-vinyl pyrrolidone - VP - to release proteins. Fibroblast growth factor-2 (FGF-2) was incorporated into cylinders of p(HEMA-co-VP). FGF-2 release was studied by ELISA in vitro and cylinders were implanted in the femoral condyle of white New Zealand rabbits. After 2 months post-surgery, FGF-2 was able to enhance bone formation by increasing bone volume; this effect was evidenced by an increase in trabecular number and bone gain was mainly in the form of woven bone. At 3 months post-surgery, no difference could be evidenced between animals receiving vehicle or FGF-2. Animals receiving vehicle exhibited bone mass higher than at 2 months and woven bone was replaced by mature bone with a lamellar matrix. The hydrogel polymer allowed the release of FGF-2, which in return enhanced bone regeneration soon after surgery but the effect vanished rapidly.

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.

Effects of basic fibroblast growth factor and a prostaglandin E2 receptor subtype 4 agonist on osteoblastogenesis and adipogenesis in aged ovariectomized rats

bFGF stimulates osteo- and adipogenesis concurrently at skeletal sites with red but not with fatty marrow, whereas a PGE2 receptor subtype 4 agonist has bone anabolic effects at both skeletal sites and decreases adipose tissue within red and fatty marrow.

INTRODUCTION

Basic fibroblast growth factor (bFGF) stimulates osteogenesis at skeletal sites with hematopoietic but not with fatty marrow. The prostaglandin E2 (PGE2) receptor subtype 4 agonist (EP4A) stimulates osteogenesis at the former skeletal sites, but its effects at fatty marrow sites are unknown. In addition, both bFGF and PGE2 through the EP4 receptor have also been implicated in adipogenesis. However, their specific effects on bone marrow adipogenesis and the inter-relationship with osteogenesis have never been studied in vivo.

MATERIALS AND METHODS

Female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated and maintained for 1 yr after surgery. OVX rats were then injected daily with bFGF or with EP4A SC for 3 wk. The osteo- and adipogenic effects of these agents were assessed by histomorphometry and by determining changes in expression of genes associated with these events by real-time PCR in the lumbar and caudal vertebrae, bones with a predominance of hematopoietic and fatty marrow, respectively. Expression of FGFR1-4 and the EP4 receptor were also evaluated by real-time PCR and immunocytochemistry.

RESULTS

bFGF and EP4A stimulated bone formation at skeletal sites with hematopoietic marrow, but only the later anabolic agent is also effective at fatty marrow sites. The diminished bone anabolic effect of bFGF at the fatty marrow site was not caused by a lack of cell surface receptors for the growth factor at this site. Interestingly, whereas EP4A decreased fatty marrow area and the number of adipocytes, bFGF increased osteogenesis and adipogenesis within the bone marrow.

CONCLUSIONS

bFGF can stimulate osteogenesis and bone marrow adipogenesis concurrently at red marrow sites, but not at fatty marrow sites. In contrast, EP4A stimulates bone formation at skeletal sites with hematopoietic and fatty marrow and simultaneously decreased fatty marrow area and the number of adipocytes in the bone marrow, suggesting that osteogenesis occurs at the expense of adipogenesis.

Osteogenic Response of Bone Marrow Stromal Cells from Normal and Ovariectomized Rats Treated with a Low Dose of Basic Fibroblast Growth Factor

Basic fibroblast growth factor (bFGF) is a potent mitogen that exhibits stimulatory effects on bone tissue regeneration. To gain further insight into the potential of bFGF for systemic therapy in osteoporosis, we investigated the responsiveness of bone marrow stromal cells (BMSCs) explanted from 7-month-old normal and ovariectomized (OVX) rats that were intravenously treated with a low dose of bFGF (25 microg/kg) for 2 weeks. The BMSCs were obtained using femoral aspiration and maintained in an osteogenic medium. The amount of cells recovered from bFGF-treated rats was lower than that from saline-treated rats, and proliferation of the cells was markedly less for the bFGF-treated rats. The BMSCs from the bFGF-treated rats also showed lower levels of specific alkaline phosphatase (ALP) activity (ALP/deoxyribonucleic acid) and mineralization. Expression of the extracellular matrix proteins critical for mineralization, in particular osteopontin, was greater for bFGF-treated cells from both types of animals in the first week of culture, after which the expression of all markers significantly declined. Dual energy x-ray absorptiometry analyses of the tibiae showed an increase in bone mineral density after bFGF treatment only for OVX rats. We conclude that osteoprogenitor cells were depleted from the marrow of bFGF-treated rats, most likely because of the stimulatory effect of bFGF on bone formation.

A comparative study of the bone-restorative efficacy of anabolic agents in aged ovariectomized rats

INTRODUCTION

The study was designed to compare the bone anabolic effects of basic fibroblast growth factor (bFGF), a selective agonist for prostaglandin E receptor subtype EP4, and parathyroid hormone (PTH) in aged ovariectomized (OVX) rats with severe cancellous osteopenia.

METHODS

Groups of aged OVX rats were maintained untreated for 1 year postovariectomy (15 months of age) to develop severe tibial cancellous osteopenia. These animals were then treated with bFGF or the EP4 agonist (EP4) for 3 weeks. Other groups of aged OVX rats were treated with EP4 or PTH alone for 11 weeks, or sequentially with bFGF or EP4 for 3 weeks followed by PTH for 8 weeks. Cancellous and cortical bone histomorphometry were performed in the right proximal tibial metaphysis and tibial diaphysis respectively.

RESULTS

Treatment with bFGF for 3 weeks markedly increased serum osteocalcin, osteoid volume, and osteoblast and osteoid surfaces to a greater extent than EP4. Basic FGF, but not EP4 or PTH, induced formation of osteoid islands within bone marrow. EP4 stimulated cancellous bone turnover, but failed to restore lost cancellous bone in the severely osteopenic proximal tibia after 11 weeks of treatment. In contrast, EP4, much like PTH, increased cortical bone mass in the tibial diaphysis by stimulating both periosteal and endocortical bone formation. Treatment of aged OVX rats with PTH alone tended to partially reverse the severe tibial cancellous osteopenia, whereas sequential treatment with bFGF and PTH increased tibial cancellous bone mass to near the level of vehicle-treated control rats. These findings indicate that bFGF had the strongest stimulatory effect on cancellous bone formation, and was the only anabolic agent to induce formation of osteoid islands within the bone marrow of the severely osteopenic proximal tibia. Therefore, bFGF may be more effective for the reversal of severe cancellous osteopenia. PTH and EP4 increased cortical bone mass to nearly the same extent, but cancellous bone mass was greater by two-fold in PTH-treated OVX rats than in EP4-treated OVX rats.

CONCLUSION

These findings in aged OVX rats suggest that PTH is more efficacious than EP4 for augmentation of cancellous bone in the severely osteopenic, estrogen-deplete skeleton.

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.

Growth factor delivery for bone tissue repair: an update

Growth factors (GFs) are endogenous proteins capable of acting on cell-surface receptors and directing cellular activities involved in the regeneration of new bone tissue. The specific actions and long-term effects of GFs on bone-forming cells have resulted in exploration of their potential for clinical bone repair. The concerted efforts have led to the recent approval of two GFs, bone morphogenetic protein-2 and osteogenic protein-1, for clinical bone repair, and human parathryroid hormone (1-34) for augmentation of systemic bone mass. This review provides a selective summary of recent (2001-2004) attempts for GF delivery in bone tissue regeneration. First, a summary of non-human primate studies involving local regeneration and repair is provided, with special emphasis on the range of biomaterials used for GF delivery. Next, efforts to administer GFs for systemic augmentation of bone tissue are summarised. Finally, an alternative means of GF delivery, namely the delivery of genes coding for osteogenic proteins, rather than the delivery of the proteins, is summarised from rodent models. To conclude, future avenues of research considered promising to enhance the clinical application of GFs are discussed.

Effects of FGF-2/-9 in calvarial bone cell cultures: differentiation stage-dependent mitogenic effect, inverse regulation of BMP-2 and noggin, and enhancement of osteogenic potential

Systemically administered fibroblast growth factors (FGFs) show anabolic effects on bone formation in animals, whereas in vitro cell culture studies have demonstrated that FGFs block mineralized bone nodule formation. These apparently contradictory outcomes indicate that the nature of FGF action is complex and that the biological effect of FGFs may depend on the differentiation stage of osteoblasts, interaction with other cytokines, or the length and mode of exposure to factors. Thus, we have utilized primary calvarial bone cell populations at different maturation phases to determine their responses to 2, FGF-9, and BMP-2, the factors expressed in bone. FGF-2 and FGF-9 stimulated proliferation of the cell populations consisting of more mature osteoblasts, but not those with undifferentiated precursor cells. Continuous treatment with FGF-2/-9 inhibited expression of several osteoblast marker genes and mineralization. However, brief pretreatment with FGF-2/-9 or sequential treatment with FGF-2/-9 followed by BMP-2 led to marked stimulation of mineralization, suggesting that FGFs enhance the intrinsic osteogenic potential. Furthermore, FGF-2 and FGF-9 increased expression of other osteogenic factors BMP-2 and TGFbeta-1. Meanwhile, blocking endogenous FGF signaling, using a virally transduced dominant-negative FGF receptor (FgfR), resulted in drastically reduced expression of the BMP-2 gene, demonstrating for the first time that endogenous FGF/FgfR signaling is a positive upstream regulator of the BMP-2 gene in calvarial osteoblasts. In contrast, expression of a BMP antagonist noggin was inhibited by FGF-2 and FGF-9. Thus, collective data from this study suggest that FGF/FgfR signaling enhances the intrinsic osteogenic potential by selectively expanding committed osteogenic cell populations as well as inversely regulating BMP-2 and noggin gene expression.

Comparison ofin VitroMineralization by Murine Embryonic and Adult Stem Cells Cultured in an Osteogenic Medium

Nearly half a million bone-grafting procedures occurred in the United States in the year 2000. Tissue-engineered bone substitutes may mitigate difficulties associated with current grafting options. Embryonic stem cells (ESCs) could be a potential cell source for bone substitutes; however, direct comparisons between ESCs and other cell sources are lacking. Here we provide a direct, long-term, in vitro comparison of mineralization processes in adult, marrow-derived, mesenchymal stem cells (MSCs) and ESCs from the 129/Sv+c/+p mouse strain. MSCs were observed to grow at a slower rate than ESCs. MSCs expressed seven times more alkaline phosphatase (AP) per cell than did ESCs and immediately showed type I collagen and osteocalcin production. ESCs also produced type I collagen and osteocalcin, but production was delayed. Mineral deposition by ESCs was nearly 50 times higher than by MSCs. Spectroscopic analysis showed the calcium-to-phosphorus ratio (Ca:P) of the ESC mineral (1.26:1) to be significantly higher than that of the MSCs (0.29:1), but still 25% lower than hydroxyapatite (1.67:1). Addition of basic fibroblast growth factor significantly inhibited AP expression, mineral deposition, and Ca:P ratios in MSCs and had little effect on ESCs. These functional characteristics may assist with cell selection for purposes of bone tissue engineering.