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

Effect of ethanol consumption during pregnancy and lactation on bone histomorphometry and in vitro osteogenic differentiation of bone marrow mesenchymal stem cells in maternal rats

This study aimed to evaluate the effect of maternal ethanol consumption during gestation and lactation on bone mass and osteogenic differentiation of mesenchymal stem cells of the bone marrow (BMMSCs) in rats. Thirteen adult Wistar rats were used. The rats were mated, and after confirmation of gestation, (day 0) they were distributed in two groups: the control group and the ethanol-treated group. From the ninth day of gestation, the rats of the ethanol and control groups were administered 40% alcoholic solution (4 g ethanol/kg) and distilled water, respectively, daily via gavage until the thirtieth day of lactation. The BMMSCs were extracted from the right femurs and tibiae and cultured using an osteogenic medium for 7, 14, and 21 days. The conversion of MTT to formazan crystals, alkaline phosphatase activity, and percentages of cells per field were analyzed. The number of mineralized nodules per field was examined, and quantification of the gene transcripts for osteopontin, osteocalcin, and BMP-2 was evaluated on day 21 by real-time RT-PCR. Morphometric evaluations of the percentage of trabecular bone and cortical thickness in the left femur and tibia were performed. The means were compared by the Student's t-test, and the differences were considered significant if p < 0.05. The BMMSCs of the rats that consumed ethanol during gestation and lactation, when subjected to osteogenic differentiation in vitro, demonstrated higher conversion of MTT to formazan, higher alkaline phosphatase activity, a higher percentage of cells per field, higher expression of BMP-2, and higher synthesis of mineralized nodules when compared to those of control rat cells. However, there was no significant difference in the percentage of trabecular bone or cortical thickness between both groups. Hence, the consumption of ethanol during pregnancy and lactation did not alter the trabecular and cortical bone tissues of the femur and tibia compared with that of pregnant and lactating control rats that did not consume alcohol, despite BMMSCs showing higher osteogenic differentiation under in vitro conditions.

Adenoviral delivery of adiponectin ameliorates osteogenesis around implants in ovariectomized rats

BACKGROUND

Adiponectin (APN) has been reported to promote bone formation. However, it is difficult to utilize a conventional method that administers sufficient APN to the implant site. The present study investigated the efficacy of an APN transgene to accelerate the implant osseointegration in ovariectomized (OVX) rats.

METHODS

In vitro, bone marrow stromal cells were transduced with reconstructed adenovirus (Ad-APN-EGFP) and osteoclast precursor RAW264.7 cells were co-cultured with the conditioned medium secreted by transduced bone marrow stromal cells. Tartrate-resistant acid phosphatase staining and bone slice resorption assay were performed to evaluate the activity of osteoclastogenesis. In vivo, Ad-APN-EGFP was administered into the bone defect prior to implant placement in OVX rats. At 7 and 28 days post implantation, the femurs were harvested and prepared for a real-time reverse transcriptase-polymerase chain reaction, hemotoxylin and eosin staining, immunohistochemical staining, micro-computed tomography analysis and biomechanical testing.

RESULTS

The results showed the formation and function of osteoclasts were significantly suppressed in vitro. Successful transgene expression was confirmed, and a significant increase of OCN, Runx2 and ALP expression was detected in the Ad-APN-EGFP group in vivo. Interestingly, we also found that the overexpression of APN decreased the expression level of potent adipogenic transcription factors such as PPARγ2 and C/EBP-α. At 28 days after implantation, the Ad-APN-EGFP group revealed a significantly increased osseointegration and implant stability in OVX rats compared to the control groups (Ad-EGFP and PBS groups).

CONCLUSIONS

APN via direct adenovirus-mediated gene transfer could ameliorate osseointegration surrounding titanium implants in OVX-related osteoporosis rats. Furthermore, it may be an effective strategy for promoting bone regeneration under osteoporotic conditions.

Mechanical strain promotes osteogenic differentiation of bone mesenchymal stem cells from ovariectomized rats via the phosphoinositide 3‑kinase/Akt signaling pathway

Osteoporosis has become an overwhelming public health problem worldwide. As an elementary physiological factor to regulate bone formation and regeneration, mechanical strain may be used as a non‑invasive intervention in osteoporosis prevention and treatment. However, little is known regarding the underlying mechanism. The aim of the current study was to investigate the effect of continuous mechanical strain (CMS) on osteogenic differentiation of bone mesenchymal stem cells (BMSCs) from ovariectomized rats (OVX BMSCs). In addition, involvement of the phosphatidylinositol 3‑kinase (PI3K)/Akt signaling pathway in biomechanical signal transduction and its function were evaluated. The results demonstrated that OVX BMSCs subjected to CMS exhibited higher alkaline phosphatase (ALP) activity and deeper staining at 24 and 48 h. In addition, CMS upregulated the mRNA expression levels of ALP, collagen type I, runt related transcription factor 2 (Runx2), as well as the protein expression level of Runx2 in a time‑dependent manner. The PI3K/Akt signaling pathway was rapidly activated by CMS, with its phosphorylation level reaching its maximum in a short duration and a large quantity of phosphorylated‑Akt remaining in the nucleus. Pre‑treatment with a selective blocker significantly blocked the strain‑induced activation of PI3K/Akt and reduced the commitment of OVX BMSCs into osteoblasts, demonstrating a dominated regulative effect of PI3K/Akt signaling in strain‑induced osteogenesis. These results indicated that CMS induced the early differentiation of OVX BMSCs towards an osteogenic phenotype by activating the PI3K/Akt signaling pathway.

The osteoimmunomodulatory properties of MBG scaffold coated with amino functional groups

Mesoporous bioactive glass (MBG) is a good scaffold for bone regeneration. In this study, amino functionalized MBG (N-MBG) was used as a model scaffold to examine the effect of the scaffold to bone marrow stromal cells (BMSCs) and macrophages. The MTT results revealed that the proliferation of BMSCs from ovariectomized rabbits was enhanced by N-MBG. Compared to the control group, the expression of osteogenic genes was significantly enhanced by N-MBG, which was related to CaSR pathway. Meanwhile, the anti-inflammatory cytokines (interleukin-10 and arginase-1) were also upregulated by N-MBG stimulation compared with MBG. Furthermore, the amino functionalization of MBG resulted in an increase in the pH value of the material extract. Interestingly, the formation of TRAP⁺ multinuclear cells was inhibited by the slightly alkaline extract to a certain extent, which reasonably explained the increase in TRAP⁺ multinuclear cells after adjusting the pH value of N-MBG extract. In vivo, the areas of new bone formation in the maxillary sinus floor elevation were increased in the N-MBG/BMSCs group with less TRAP⁺ multinuclear cells compared with the MBG/BMSCs group. These findings provided valuable insight that the osteogenic ability of MBG scaffold could be enhanced by amino functionalization due to coordinate BMSCs and macrophages differentiation.

Effect of a local, one time, low-dose injection of zoledronic acid on titanium implant osseointegration in ovariectomized rats

INTRODUCTION

Local application of bisphosphonates has been proven to be safer than systemic administration to promote implant fixation. The objective of this study was to introduce such a simple, convenient and efficient method to enhance titanium (Ti) implant osseointegration in ovariectomized (OVX) rats.

MATERIAL AND METHODS

Twenty female Sprague-Dawley rats sequentially underwent bilateral ovariectomy and tibia implantation, and injection of 30 µg/implant zoledronic acid (ZOL) at the site of implantation was performed. At the end of the study, the tibiae, mandibles, femurs and vertebrae were harvested for dual energy X-ray absorptiometry, histology and micro-computed tomography examination.

RESULTS

Ovariectomized rats showed poor bone density, bone mass and trabecular microstructure. OVX + ZOL rats were characterized by significantly improved peri-implant bone area (1.72-fold), bone contact (2.30-fold), bone mineral density (1.57-fold) and bone mineral content (1.67-fold), as well as moderately increased bone volume to total volume ratio (1.34-fold), percentage osteointegration (1.54-fold), connectivity density (1.45-fold), and trabecular number (1.43-fold), but decreased trabecular separation (57.69%) when compared with the control levels (p < 0.05). No histological signs of jaw osteonecrosis were observed in the rats treated with ZOL, and there was no significant difference between the OVX group and OVX + ZOL group in the bone mass of the mandible, femur and 5^th lumbar vertebra (p > 0.05). In addition, the overproduction of osteoporosis-induced advanced glycation end-products (AGEs) was completely prevented by local treatment with 30 µg/implant ZOL.

CONCLUSIONS

A local, one time, low-dose injection of ZOL at the site of implantation is able to promote the osseointegration of Ti implants following postmenopausal osteoporosis, and this action may be partly mediated by inhibition of the osteoporosis-induced AGE overproduction in the bone marrow.

Effect of osteoporosis on fixation of osseointegrated implants in rats

The effect of osteoporosis on implant osseointegration has been widely investigated, whereas osteoporosis may also newly occur in patient with previously osseointegrated implant. This study was designed to investigate the effect of osteoporosis on implant fixation in rats after successful osseointegration had been obtained. Seventy female Sprague-Dawley rats were included, and each animal received two titanium implants in the distal metaphysis of femur bilaterally. Eight weeks later, ten rats were sacrificed to confirm the establishment of implant osseointegration. All left rats were randomly subjected to bilateral ovariectomy (OVX) or sham operation. Three, six, and twelve weeks later, implant osseointegration, peri-implant bone tissue, and biomechanical properties of implant were analyzed. Right femurs with implants were used for micro-CT and histological analysis, and left femurs with implants were used for biomechanical test. Micro-CT, histology, and biomechanical test confirmed the destructive effect of OVX on previously osseointegrated implant in rats; when compared to sham-operated rats, peri-implant bone volume, trabecular architecture, bone-to-implant contact ratio, as well as biomechanical parameters decreased progressively within 12 weeks. Results also indicated that the effect of OVX on undisturbed bone (proximal tibiae) was much stronger than that on peri-implant bone. Osteoporosis produced a progressive negative effect on previously osseointegrated implant in distal femora of rats during 12 weeks. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2426-2432, 2017.

[Efficacy of systemic administration of oxytocin on implant osseointegration in osteoporotic rats]

OBJECTIVE

This study investigated the effects of systemic administration of oxytocin (OT) in osteoporotic rats on implant osseointegration.

METHODS

Twenty rats were randomly assigned to the control and experimental groups. Initially, the rats underwent bilateral ovariectomy. After 12 weeks, an osteoporosis model was established. Each rat received an implant at the distal and middle femoral metaphysis. Simultaneously, systemic administration was conducted with one group receiving subcutaneous injection of OT (1 mg·kg⁻¹ per day), whereas the other group received placebo injection. After treatment for 4 weeks, another surgery was conducted to remove the thigh bones from the rats containing the implants for an eight-week observation. With the employment of micro-CT, histological observation and push-out test, osseointegration was evaluated. While the rats received thigh-bone removal surgery, another surgery was conducted to remove the tibia metaphysis from the rats of both groups to perform histological observation and micro-CT inspection.

RESULTS

The trabecular bone of tibial samples was intensive and formed woven mesh structure in the experimental group compared with the control group. In the experimental group, the relative bone volume/tissue volume surrounding the implant, the bone contact ratio, and the maximum push-out force of the implant were 0.35%±0.06%, 67.25%±9.06%, and (70.32±10.91) N, respectively, the corresponding values were 0.11%±0.02%, 43.25%±7.01% and (21.65±4.36) N in the control group, and the experimental group increased significantly compared with the control group (P<0.05).

CONCLUSIONS

Systemic administration of OT cannot only antagonize the negative effects of osteoporosis but can also promote implant healing and osseointegration of pure titanium implants.

The effect of oxytocin on osseointegration of titanium implant in ovariectomized rats

INTRODUCTION

Oxytocin (OT) was reported to control differentiation of human mesenchymal stem cells and reverse osteoporosis (OP). This study investigated the effect of systematical treatment of OT on implant osseointegration in ovariectomized (OVX) rats.

MATERIAL AND METHODS

Twenty female rats received bilateral ovariectomy. Twelve weeks later, all animals were randomly assigned to control or experimental group. Each rat received two implants at the distal femoral metaphysis. From the first postoperative day, rats in experiment group received subcutaneous injection of OT (1 mg/kg · d), while animals in control group received vehicle. Twelve weeks after implantation, specimens containing implants were harvested and evaluated by histology, micro-CT, and push-out test. Tibiae were also harvested to evaluate the effect of OT on intact bone tissue of OVX rats.

RESULTS

Compared with control, OT treatment increased the relative bone volume surrounding the implant by 2.2 times, the percent implant osseointegration by 0.62 times, and the maximum push-out force by 2.25 times. Increased bone mass was also observed in histological sections of distal femur with implant and intact bone tissue of the proximal tibiae.

CONCLUSION

Systemic administration of OT promoted peri-implant bone healing and osseointegration of titanium implant and recovered the negative effects of OP in undisturbed bone tissue partially.

Inhibition of the osteogenic differentiation of mesenchymal stem cells derived from the offspring of rats treated with caffeine during pregnancy and lactation

Caffeine is an alkaloid that is widely consumed due to its presence in drugs, coffee, tea, and chocolate. This compound passes to offspring through the placenta and milk; can cause teratogenic mutations; and reduces the formation, growth, and mass of bone. Because mesenchymal stem cells (MSCs) are responsible for generating the entire skeleton, we hypothesized that these cells are targets of caffeine. This study evaluated the osteogenic differentiation of MSCs derived from the offspring of rats treated with caffeine during pregnancy and lactation. Twenty-four adult Wistar rats were randomly divided into four groups, including one control group and three experimental groups treated with 25, 50, or 100 mg/kg of caffeine. At weaning, three 21-day-old pups from each dam in each group were euthanized for extraction of bone marrow cells for in vitro tests. Caffeine doses of 50 and 100 mg/kg significantly reduced the activity of alkaline phosphatase at 7, 14, and 21 days and the expression of collagen I at 21 days. However, the expression of gene transcripts for alkaline phosphatase, Runx-2, and bone sialoprotein, as well as the synthesis of mineralization nodules, decreased significantly in all groups treated with caffeine. The expression of osteocalcin was significantly reduced only in the group treated with 50 mg/kg caffeine. The caffeine that passes from the mother to the offspring during pregnancy and lactation reduces the osteogenic differentiation of MSCs. We propose that this reduction in the osteogenic potential of MSCs may be involved in the pathogenesis of osteopenia resulting from caffeine consumption.

Treatment study of distal femur for parathyroid hormone (1-34) and β-tricalcium phosphate on bone formation in critical size defects in rats

The objective of this study was to evaluate local bone formation following systemic administration of parathyroid hormone (1-34), a surgically implanted synthetic β-tricalcium phosphate bone biomaterial serving as a matrix to support new bone formation. Twelve weeks after bilateral ovariectomy, all rats underwent bone defect in the distal femurs, and β-tricalcium phosphate was implanted into critical sized defects. After defect operation, all animals were randomly divided into four groups and received following subcutaneous injections until death at four and eight weeks: sham rats (group ST); sham rats + parathyroid hormone, 30 µg/kg, three times a week (group SPT); OVX rats (group OT); and OVX rats + parathyroid hormone (group OPT). The distal femurs of rats were harvested for evaluation. The treatment group demonstrating the highest levels of new bone formation was the defects treated with parathyroid hormone as assessed by micro-computed tomography, biomechanical strength, and histological analysis for sham rats. Furthermore, parathyroid hormone showed a stronger effect on accelerating the degradation of β-tricalcium phosphate. Osteoporosis can limit the function of parathyroid hormone and/or β-tricalcium phosphate. The results from our study demonstrate that combination of parathyroid hormone and β-tricalcium phosphate brings better effect to bone tissue repair in non-osteoporosis and/or osteoporosis status.

Adenoviral vector-mediated overexpression of osteoprotegerin accelerates osteointegration of titanium implants in ovariectomized rats

This study investigated the efficacy of human osteoprotegerin (hOPG) transgene to accelerate osteointegration of titanium implant in ovariectomized (OVX) rats. Bone marrow stromal cells transduced with Ad-hOPG-EGFP could sustainedly express hOPG. Osteoclast precursor RAW264.7 cells treated by the hOPG were examined by tartrate-resistant acid phosphatase (TRAP) staining and bone slice resorption assay. The results showed differentiation and function of osteoclasts were significantly suppressed by hOPG in vitro. Ad-hOPG-EGFP was locally administered to the bone defect prior to implant placement in OVX and sham rats. After 3, 7, 28 days of implantation, the femurs were harvested for molecular and histological analyses. Successful transgene expression was confirmed by western blot and cryosectioning. A significant reduction in TRAP+ numbers was detected in Ad-hOPG-EGFP group. Real-time reverse transcriptase-PCR examination revealed that hOPG transgene markedly diminished the expression of cathepsin K and receptor activator for nuclear factor-κ B ligand in vivo. The transgene hOPG modification revealed a marked increasing osteointegration and restored implant stability in OVX rats (P<0.01), compared with the control groups (Ad-EGFP or sterilized phosphate-buffered saline) 28 days after implantation. In conclusion, hOPG via direct adenovirus-mediated gene transfer could accelerate osteointegration of titanium implants in OVX rats. Osteoprotegerin gene therapy may be an effective strategy to osteointegration of implants under osteoporotic conditions.

Core–shell microspheres delivering FGF-2 and BMP-2 in different release patterns for bone regeneration

Sequential delivery of FGF-2 and BMP-2 efficiently bridged the bone defects and remodeled the bone graft.

In vitro proliferation and differentiation potential of bone marrow-derived mesenchymal stem cells from ovariectomized rats

Bone marrow-derived mesenchymal stem cells (BMMSCs) from the patients suffering from age-related osteoporosis were found to have numerous degeneration, such as decreased growth rate, impaired capacity of differentiating into local tissue, and repressed telomerase activity. However, it is not clear whether post-menopausal osteoporotic bone is either subject to such decline in cellular function. In the present study, bone marrow cells were harvested from ovariectomized (OVX) and Sham rats and cultured in vitro at 3 months post-surgery. MTT assay indicated that the proliferation potential of (OVX)BMMSCs was always higher than that of (Sham)BMMSCs, no matter cultured in basic, osteoblastic or adipogenic medium. Alkaline phosphatase activity assay, Alizarin red S staining, Oil red O staining and real-time RT-PCR analysis further demonstrated that bilateral ovariectomization positively influenced the osteoblastic and adipogenic differentiation potential of BMMSCs, this action may be partly mediated through up-regulation of osteoblastic special markers core binding factor a1, collagen type I and low-density lipoprotein receptor-related protein 5, as well as adipogenic special markers peroxisome proliferators activated receptor gamma, CCAAT/enhancer binding protein alpha and adipocyte lipid-binding protein 2. These results may hold great promise for using post-menopausal osteoporotic bone as an attractive autologous marrow source for tissue engineering and cell-based therapies.

New bone formation enhanced by ADSCs overexpressing hRunx2 during mandibular distraction osteogenesis in osteoporotic rabbits

Promoting new bone formation during distraction osteogenesis (DO) in elderly patients with osteoporosis is still a challenge. In this study, we investigated the effect of gene therapy using local Runt-related gene 2 on new bone formation during osteoporotic mandibular DO in rabbits. First, we successfully established a mandibular osteoporotic animal model by ovariectomizing rabbits. Second, the right mandibles of the osteoporotic rabbits were distracted after corticotomy. The distraction gap of the rabbits in Group A2 and B2 were injected with Adv-hRunx2-GFP-transfected adipose-derived stromal cells (ADSCs) and Adv-GFP-transfected ADSCs, respectively. Rabbits in Groups C2 (ovariectomized control) and D2 (sham surgery control) were injected with physiologic saline. New-generation bone tissue in the distraction gap was analyzed via plain radiographic examinations, micro-computed tomography, histological examinations, and biomechanical testing at weeks 3, 6, and 9 of the consolidation period. Results of above examinations showed that no ideal new bone formation was observed in Groups B2 and C2, but obvious ideal new bone formation was observed in Group A2 and D2. The results suggested that gene therapy using rhRunx2-modified ADSCs promoted new bone formation during osteoporotic mandibular DO and effectively compensated for the detrimental effects of systemic osteoporosis on new bone formation.

Optimization of release pattern of FGF-2 and BMP-2 for osteogenic differentiation of low-population density hMSCs

In the modern design, most delivery systems for bone regeneration focus on a single growth factor (GF) or a simple mixture of multiple GFs, overlooking the coordination of proliferation and osteogenesis induced by various factors. In this study, core-shell microspheres with poly-l-lactide core-poly(lactic-co-glycolic acid) shell were fabricated, and two GFs, basic fibroblast growth factor 2 (FGF-2) and bone morphogenetic protein 2 (BMP-2) were encapsulated into the core or/and shell. The effects of different release patterns (parallel or sequential manners) of FGF-2 and BMP-2 from these core-shell microspheres on the osteogenic differentiation of low-population density human mesenchymal stem cells (hMSCs) were investigated and the temporal organization of GF release was optimized. In vitro experiments suggested that induction of osteogenic differentiation of low-population density hMSCs by the sequential delivery of FGF-2 followed by BMP-2 from the core-shell microspheres (group S2) was much more efficient than that by the parallel release of the two factors from uniform microspheres (group U). The osteogenic induction by the sequential delivery of BMP-2 followed by FGF-2 from core-shell microspheres (group S1) was even worse than that from microspheres loaded with BMP-2 in both core and shell (group B), although comparable to the cases of parallel delivery of dual GFs (group P). This study showed the advantages of group S2 microspheres in inducing osteogenic differentiation of low-population density hMSCs and the necessity of time sequence studies in tissue engineering while multiple GFs are involved.

Comparative study of osteogenic differentiation potential of mesenchymal stem cells derived from bone marrow and adipose tissue of osteoporotic female rats

Osteoporosis causes reduction of osteogenic differentiation of mesenchymal stem cells (MSCs) from bone marrow and adipose tissue. This study was designed to compare the osteogenic potential of bone marrow mesenchymal stem cells (BMMSCs) and adipose-derived stem cells (ADSCs) of ovariectomized (OVX) rats. MSC were harvested from bone marrow and inguinal fat pads of six OVX rats. The limitations of this report are that cells from different animals were pooled for the purpose of the experiments that were carried out in this study. At 7, 14 and 21 d of osteogenic differentiation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion, alkaline phosphatase activity and gene expression for collagen I, osteocalcin, bone sialoprotein, osteopontin and bone morphogenetic protein-2 bone morphogenetic protein-2 (BMP-2) were analyzed. At 21 d, percentage of cells per field and percentage of mineralized nodule were analyzed. The data were subjected to analysis of variance, and the means were compared by Student-Newman-Keuls test. The cells, regardless of group, showed phenotypic characteristics consistent with stem cells. MTT conversion, alkaline phosphatase activity, percentage of mineralized nodule and expression of collagen I, osteocalcin and BMP-2 of ADSCs from OVX rats were higher when compared to BMMSCs from OVX rats in at least one of the evaluated periods (p<0.05). However, bone sialoprotein and osteopontin expression were smaller than those observed in BMMSCs for all evaluated periods (p<0.05). It was concluded that the ADSCs from OVX rats have higher osteogenic potential when compared to BMMSCs from OVX rats. This result suggests that the treatment of osteoporosis with autologous ADSCs may be more efficient.

Effects of glucocorticoid receptor antagonist, RU486, on the proliferative and differentiation capabilities of bone marrow mesenchymal stromal cells in ovariectomized rats

Glucocorticoids (GCs) potentially regulate the proliferation, differentiation, and premature senescence of bone marrow mesenchymal stem/stromal cells (MSCs). In the present study we investigated the effects mediated by endogenous GCs and the effects of an antagonist of the glucocorticoid receptor, RU486, on the proliferative and differentiation capabilities of MSCs using an ovariectomized (OVX) animal model. Following ovariectomy and a decrease in systemic estradiol levels, the serum concentration of corticosterone is significantly increased in OVX rats. Compared to sham-operated controls, the total superoxide dismutase (SOD) activity in serum of OVX rats and the proliferation of their MSCs are significantly reduced. Furthermore, the osteogenic differentiation capabilities of OVX rat MSCs are significantly decreased, while adipogenic capabilities tend to increase. Subcutaneous administration of RU486 effectively increases the population and proliferative capacity of the MSCs in OVX rats. RU486 treatment also improves osteogenic capabilities and down-regulates adipogenic capabilities of MSCs. These results strongly indicate that the elevated levels of endogenous GCs induced by estrogen depletion might accelerate the premature senescence of MSCs and reduce their proliferative and osteogenic differentiation capabilities, while the blockage of the effects of endogenous GCs may restore their capabilities. These responses could potentially be developed to protect the capabilities of MSCs from oxidative stress-induced premature senescence and extend their lifespan in patients with advancing age and estrogen depletion.

Curculigoside promotes osteogenic differentiation of bone marrow stromal cells from ovariectomized rats

OBJECTIVES

Curculigoside, a natural compound isolated from the medicinal plant Curculigo orchioides has been reported to prevent bone loss in ovariectomized rats. However, the underlying molecular mechanisms are largely unknown. This study investigated the effects of curculigoside on proliferation and osteogenic differentiation of bone marrow stromal cells (BMSCs).

METHODS

The toxicity, proliferation and osteogenic differentiation of BMSCs cultured with various concentrations (0 as control, 10, 100 and 500 µm) of curculigoside were measured by viability assay, MTT analysis, alkaline phosphatase (ALP) activity assay, alizarin red staining and mineralization assay, real-time PCR analysis on osteogenic genes including ALP, type I collagen (Col I), osteocalcin (OCN) and osteoprotegerin (OPG), runt-related transcription factor 2 (Runx2), as well as OPG enzyme-linked immunosorbent assay.

KEY FINDINGS

No significant cytotoxicity was observed for BMSCs after supplementation with curculigoside. The proliferation of BMSCs was enhanced after administration of curculigoside, especially 100 µm curculigoside. Moreover, the osteogenic gene expression was significantly enhanced with 100 µm curculigoside treatment. Importantly, curculigoside significantly increased OPG secretion.

CONCLUSIONS

The data indicate that curculigoside could promote BMSC proliferation and induce osteogenic differentiation of BMSCs. The most profound response was observed with 100 µm curculigoside. These findings may be valuable for understanding the mechanism of the effect of curculigoside on bone, especially in relation to osteoporosis.

Effect of therapeutic ultrasound on human periodontal ligament cells for dental and periodontal tissue engineering

The objective of this study was to investigate whether low intensity pulsed ultrasound (LIPUS) has anabolic effects on human periodontal ligament (PDL) cells. The PDL cells were plated in 48-well plates and cultured at 37°C in an atmosphere of 5% CO2 in air, in a humidified incubator until confluent. The cells were divided into three groups including control, 5 min and 10 min ultrasound application. The LIPUS was applied using a 2.5 transducer that produces an incident intensity of 30 mW/cm2 of the transducer's surface area. The results from the quantitative polymerase chain reaction (PCR) indicates that expression levels of alkaline phosphatase (ALP),cyclin D1 (CYC), nucleostemin (NCT) were increased after four weeks of 10 minutes of daily ultrasound treatment. The increased ALP/DNA by LIPUS shows a time dependent pattern with the highest activity occurring after four weeks of treatment. These results demonstrate that LIPUS has an anabolic effect on PDL cells and suggest that LIPUS may enhance the pluripotent characteristics of PDL cells as indicated by the up-regulation of NCT, a stem marker. These results also may explain the potential role of LIPUS in periodontal tissue regeneration.

The effects of combined human parathyroid hormone (1-34) and zoledronic acid treatment on fracture healing in osteoporotic rats

Ovariectomized (OVX) rats with tibial fracture received vehicle, ZA, PTH, or ZA plus PTH treatment for 4 and 8 weeks. Bone metabolism, callus formation, and the mass of undisturbed bone tissue were evaluated by serum analysis, histology, immunohistochemistry, radiography, micro-computerized tomography, and biomechanical test.

INTRODUCTION

Previous studies have demonstrated the effect of ZA or PTH on osteoporotic fracture healing. However, reports about effects of ZA plus PTH on callus formation of osteoporotic fracture were limited. This study was designed to investigate the impact of combined treatment with ZA and PTH on fracture healing in OVX rats.

METHODS

Twelve weeks after bilateral ovariectomy, all rats underwent unilateral transverse osteotomy on tibiae. Animals then randomly received vehicle, ZA (1.5 μg/kg weekly), PTH (60 μg/kg, three times a week), or ZA plus PTH until death at 4 and 8 weeks. The blood and bilateral tibiae of rats were harvested for evaluation.

RESULTS

All treatments increased callus formation and strength other than the control; ZA + PTH showed the strongest effects on percent bone volume (BV/TV), trabecular thickness, total fluorescence-marked callus area, and biomechanical strength. Additionally, inhibited RANKL and enhanced osteoprotegerin expression were observed in the ZA + PTH group. But no difference in bone mineral density and BV/TV of the contralateral tibiae was observed between treated groups.

CONCLUSION

Findings in this study suggested an additive effect of ZA and PTH on fracture healing in OVX rats, and this additive effect was specific to callus formation, not to undisturbed bone tissue.

Osteogenic differentiation of human mesenchymal stem cells cultured with dexamethasone, vitamin D3, basic fibroblast growth factor, and bone morphogenetic protein-2

PURPOSE

Human mesenchymal stem cells (hMSCs) are pursued for cell-based therapies of bone defects. Successful use of hMSCs will require them to be osteogenically differentiated before transplantation. This study was intended to determine the optimal combination(s) of supplements needed for inducing osteogenesis in hMSCs.

METHODS

The hMSCs were cultured with combinations of β-glycerophosphate, dexamethasone (Dex), vitamin D3 (Vit-D3), basic fibroblast growth factor (bFGF), and bone morphogenetic protein-2 (BMP-2) to assess cell growth and osteogenesis. Osteogenic responses of the supplements were evaluated by alkaline phosphatase (ALP) activity, mineralization, and gene expression of ALP, Runx2, bone sialoprotein, and osteonectin. Adipogenesis was characterized based on Oil Red O staining, gene expression of peroxisome proliferator-activated receptor γ2, and adipocyte protein-2.

RESULTS

Dex was found to be essential for mineralization of hMSCs. Cultures treated with Dex (100 nM), Vit-D3 (10/50 nM), and BMP-2 (500 ng/mL) demonstrated maximal calcification and up-regulation of ALP and bone sialoprotein expression. However, adipogenesis was up-regulated in parallel with osteogenesis in these cultures, as evident by the presence of lipid droplets and significant up-regulation of peroxisome proliferator-activated receptor γ2 and adipocyte protein-2 expression. An optimal condition was obtained at Dex (10 nM) and BMP-2 (500 ng/mL) for mineralization without increasing adipogenesis-related markers. The bFGF mitigated osteogenesis and enhanced adipogenesis. Vit-D3 appears essential for calcification only in the presence of bFGF.

CONCLUSION

Treatment of hMSCs with appropriate supplements at optimal doses results in robust osteogenic differentiation with minimal adipogenesis. These findings could be used in the cultivation of hMSCs for cell-based strategies for bone regeneration.

In vitro osteogenic induction of human gingival fibroblasts for bone regeneration

Background And Objective:

Periodontitis is an inflammatory disease causing bone loss, and is a primary cause of tooth loss. Gingival fibroblasts are readily available with minimal donor site morbidity and may be ideal for tissue engineering efforts in regenerating lost alveolar bone. Dexamethasone (Dex) is commonly employed for in vitro osteogenic induction of a variety of cells, but its effect on human gingival fibroblasts (HGF) is still controversial. Therefore, the aim of our study was to investigate the osteogenic differentiation of HGF following Dex treatment.

Methods:

Cultured HGFs were exposed to osteogenic medium containing a wide range of Dex concentrations (0.01-10 µM). The osteogenic phenotype was assessed based on changes in alkaline phosphatase (ALP) activity, the mRNA expression of selected extracellular matrix proteins critical for mineralization and the extent of extracellular mineralization (Von Kossa staining and Ca-content).

Results:

All assays showed a consistent and maximal osteogenic effect of Dex on HGF at 0.1 and 0.5 µM (weeks 3 and 4), as evidenced by significant osteopontin and osteocalcin expression and mineralization. Longer cultures (week 4) also yielded positive osteogenic effect of Dex at 0.01 µM. Moreover, ALP activity was significantly stimulated at 0.1 and 0.5 µM Dex initially after one week, but ALP was subsequently reduced under Dex. Higher Dex concentrations caused down regulation of osteogenic effects observed at the optimal (0.1-0.5 µM) concentrations.

Conclusion:

Under appropriate osteogenic conditioning, Dex treated HGFs could be a potential source of cells for cell-based therapy for periodontal bone regeneration.

Thrombospondin-1 prevents excessive ossification in cartilage repair tissue induced by osteogenic protein-1

This study investigated the effect of thrombospondin-1 (TSP-1) on the formation of cartilage repair tissue in combination with stimulation by osteogenic protein-1 (OP-1). In miniature pigs, articular cartilage lesions in the femoral trochlea were treated by the microfracture technique and either received no further treatment (MFX), or were treated by additional application of recombinant osteogenic protein-1 (MFX+OP-1), recombinant TSP-1 (MFX+TSP-1), or a combination of both proteins (MFX+TSP-1+OP-1). Six and 26 weeks after surgery, the repair tissue and the degree of endochondral ossification were assessed by histochemical and immunohistochemical methods detecting collagen types I, II, X, TSP-1, and CD31. Microfracture treatment merely induced the formation of inferior fibrocartilaginous repair tissue. OP-1 stimulated chondrogenesis, but also induced chondrocyte hypertrophy, characterized by synthesis of collagen type X, and excessive bone formation. Application of TSP-1 inhibited inadvertant endochondral ossification, but failed to induce chondrogenesis. In contrast, the simultaneous application of both TSP-1 and OP-1 induced and maintained a permanent, nonhypertrophic chondrocyte-like phenotype within cartilage repair tissue. The data of this study demonstrate that OP-1 and TSP-1 complement each other in a functional manner. While OP-1 induces chondrogenesis of the ingrowing cells, TSP-1 prevents their further hypertrophic differentiation and prevents excessive endochondral ossification within the lesions.

Systemic treatment with strontium ranelate promotes tibial fracture healing in ovariectomized rats

Systemic treatment with strontium ranelate (SR) was performed on ovariectomized (OVX) rats with fractured tibiae. Callus quality was assessed by radiographic, histological, micro-computerized tomography, and biomechanical examinations at 4 and 8 weeks after fracture. Results revealed that systemic applied SR promoted osteoporotic fracture healing.

INTRODUCTION

Several studies have demonstrated the dual effect of SR on osteoporotic and undisturbed bone. However, reports of their effect on osteoporotic fracture healing are limited. This study was designed to investigate the effects of SR on bone regeneration in OVX rats with fractured tibiae.

METHODS

Three months after being OVX, female Sprague-Dawley rats accepted bilateral osteotomy on proximal tibiae fixed with intramedullary wires and were divided into two groups: OVX and OVX + SR (625 mg/kg/day). Callus quality was evaluated at 4 and 8 weeks postfracture.

RESULTS

Compared with OVX group, SR treatment significantly increased bone formation, BMD, biomechanical strength, and improved microstructural properties of the callus. The ultimate load was increased by 211.0% and 61.4% (p<0.01), and the total bone volume of callus by 74.8% and 79.3% (p<0.01) at 4 and 8 weeks postfracture, respectively. SR treatment also promoted healing progress with increased osteogenesis at 4 weeks; more mature and tightly arranged woven or lamellar bone at 8 weeks across the fracture gap in histological analysis.

CONCLUSION

This study suggests that systemic treatment with strontium ranelate could promote tibial fracture healing in OVX rats.

Strontium ranelate treatment enhances hydroxyapatite-coated titanium screws fixation in osteoporotic rats

Increased bone turnover with excessive bone resorption and decreased bone formation is known to impair implant fixation. Strontium ranelate is well known as an effective antiosteoporotic agent by its dual effect of antiresorbing and bone-forming activity. This study was designed to evaluate the effect of systemic strontium ranelate (SR) treatment on fixation of hydroxyapatite (HA)-coated titanium screws in ovariectomized (OVX) rats. Twelve weeks after being OVX (n=30) or sham (n=10) operated, 40 female Sprague-Dawley rats received unilateral implants in the proximal tibiae. The OVX rats were randomly divided into the following groups: OVX, OVX+SRL ("L" refers to low SR dose of 500 mg/kg/day), OVX+SRH ("H" refers to high SR dose of 1000 mg/kg/day).Twelve weeks after treatment, bone blocks with implants were evaluated with micro-CT and biomechanical push-out tests. Compared to OVX animals, SR treatment increased the bone volume ratio by 51.5% and 1.1-fold, the percentage osteointegration by 1.0-fold and 1.9-fold in micro-CT evaluation, and the maximal force by 1.9-fold and 3.3-fold in biomechanical push-out test, for the low and high dose of SR, respectively. Significant correlation between micro-CT and biomechanical properties demonstrated that trabecular parameters played an important role in predicting the biomechanical properties of implant fixation. Our findings suggest that SR treatment can dose-dependently improve HA-coated screw fixation in OVX rats and facilitate the stability of the implant in the osteoporotic bone.

Stem cell antigen-1+ cell-based bone morphogenetic protein-4 gene transfer strategy in mice failed to promote endosteal bone formation

BACKGROUND

This study assessed whether a Sca-1+ cell-based ex vivo gene transfer strategy, which has been shown to promote robust endosteal bone formation with a modified fibroblast growth factor-2 (FGF2) gene, can be extended to use with bone morphogenetic protein (BMP)2/4 hybrid gene.

METHODS

Sublethally irradiated recipient mice were transplanted with lentiviral (LV)-BMP2/4-transduced Sca-1+ cells. Bone parameters were monitored by pQCT and microCT. Gene expression was assessed by the real-time reverse transcriptase-polymerase chain reaction.

RESULTS

Recipient mice of LV-BMP2/4-transduced Sca-1+ cells yielded high engraftment and increased BMP4 mRNA levels in marrow cells; but exhibited only insignificant increases in serum and bone alkaline phosphatase activity compared to control mice. pQCT and microCT analyses of femurs showed that, with the exception of small changes in trabecular bone mineral density and cortical bone mineral content in LV-BMP2/4 mice, there were no differences in measured bone parameters between mice of the LV-BMP2/4 group and controls. The lack of large endosteal bone formation effects with the BMP4 strategy could not be attributed to ineffective engraftment or expansion of BMP4-expressing Sca-1+ cells, an inability of the transduced cells to secrete active BMP4 proteins, or to use of the LV-based vector.

CONCLUSIONS

Sca-1+ cell-based BMP4 ex vivo strategy did not promote robust endosteal bone formation, raising the possibility of intrinsic differences between FGF2- and BMP4-based strategies in their ability to promote endosteal bone formation. It emphasizes the importance of choosing an appropriate bone growth factor gene for delivery by this Sca-1+ cell-based ex vivo systemic gene transfer strategy to promote bone formation.

Anabolic effects of low-intensity pulsed ultrasound on human gingival fibroblasts

OBJECTIVE

Low-intensity pulsed ultrasound (LIPUS) demonstrated anabolic effects on cementoblasts, odontoblasts, and periodontal ligament cells. However, LIPUS effect on human gingival fibroblasts (HGF) remains to be investigated. Therefore, we evaluated the in vitro effects of LIPUS on HGF proliferation and differentiation to test its feasibility for periodontal therapy.

DESIGN

LIPUS treatment (1.5MHz, 30mW/cm(2)) was applied to HGF in the experimental groups after 24-h of culture (5 or 10min/day for 28 days) and omitted in the control. Changes in HGF activities were evaluated in response to LIPUS treatment in dose-dependent (5 and 10min) and time-dependent (weeks 1-4) manner. The effects of LIPUS on HGF cell viability (MTT), proliferation (total DNA content and growth pattern), alkaline phosphatase (ALP) activity, and gene expression by reverse-transcriptase polymerase chain reaction (RT-PCR) were determined.

RESULTS

Cell viability remained unchanged after LIPUS treatment during the 4 weeks of treatment as compared to the untreated control group which ensured a safe biological response. Both LIPUS treatments (5-10min/day) did not yield any significant changes in the proliferation, and expression of proliferating cell nuclear antigen (PCNA) and collagen-I (COL-I). Conversely, LIPUS treatment enhanced osteogenic differentiation potential of HGF as determined by significant up-regulation of specific ALP activity and osteopontin (OPN) expression, with optimum effect following 3 weeks of 5min/day LIPUS treatment.

CONCLUSION

LIPUS treatment at 30mW/cm(2) selectively enhanced HGF differentiation but not proliferation. The ability of LIPUS to enhance HGF differentiation is promising for its application in cell-based periodontal therapy.

Effect of combined local treatment with zoledronic acid and basic fibroblast growth factor on implant fixation in ovariectomized rats

Osteoporosis is a skeletal disorder characterized by low bone mass and deterioration of bone microarchitecture resulting in bone fragility, which impairs fixation of the implants. Zoledronic acid (ZOL) is a potential inhibitor of osteoclast-mediated bone resorption and basic fibroblast growth factor (bFGF) is a growth factor that stimulates osteoblast-mediated bone formation, and these drugs could enhance fixation of implants under osteoporotic conditions. In this study, 40 ovariectomized (OVX) rats were randomly divided into 4 groups (n=10 for each group) and underwent bilateral tibiae implantation using hydroxyapatite (HA)-coated titanium implant: Control group (distilled water immersing before implantation), ZOL group (1 mg/ml of ZOL immersing), bFGF group (20 microg/ml of bFGF immersing), and ZOL+bFGF group (1 mg/ml of ZOL and 20 microg/ml of bFGF immersing). At 3 months after implantation, all animal were sacrificed and the tibiae were harvested for histology, micro-CT examinations and biomechanical testing. Bone area and contact, determined by histomorphometric analysis, were 2.7-fold and 1.8-fold in the ZOL-treated implants, 1.9-fold and 1.8-fold in the bFGF-treated implants, 3.6-fold and 2.3-fold in the both-treated implants compared with controls (p<0.01). Such significant effects were further confirmed by microstructure parameters, the bone volume ratio and the percentage osteointegration were significantly increased by ZOL treatment (3.0-fold and 1.8-fold), bFGF treatment (1.2-fold and 1.9-fold) and ZOL+bFGF treatment (3.3-fold and 2.7-fold) (p<0.001). In addition, push-out test showed that the maximum force and the corresponding interfacial shear strength of the implants treated by ZOL, bFGF and ZOL+bFGF was 8.4-fold and 8.6-fold, 3.8-fold and 3.7-fold, 10.8-fold and 10.7-fold of the control levels, respectively (p<0.05). The combined treatment was better than either treatment alone for force, but was not different from ZOL alone for interfacial strength. The significant correlation between biomechanical and micro-CT parameters demonstrates the role of microstructure assessments in predicting mechanical fixation of implants (p<0.01). Our study suggests that locally applied ZOL or bFGF may improve implant fixation in the ovariectomized rats, and that combined treatment has more beneficial effects on osseointegration, peri-implant bone formation and maximum force than either intervention alone.