Co-stimulation with bone morphogenetic protein-9 and FK506 induces remarkable osteoblastic differentiation in rat dedifferentiated fat cells

Enhanced bone formation of rat mandibular bone defects with collagen membranes loaded on bone morphogenetic protein-9

Background/purpose

Bone morphogenetic protein-9 (BMP-9) has demonstrated multiple advantages in promoting osteogenesis. Our previous findings have indicated that the use of an absorbable collagen membrane (ACM) as a carrier for growth factors is effective in stimulating bone regeneration. The objective of this study was to assess the synergistic impact of BMP-9 incorporated into ACM (ACM/BMP-9) on bone formation within rat mandibular bone defects.

Materials and methods

Circular bone defects of critical size were surgically induced on both sides of the rat mandibular bone, with subsequent random allocation into distinct groups: control, ACM alone, and ACM loaded with low (0.5 μg) or high (2.0 μg) concentrations of BMP-9. We conducted real-time in vivo micro-computerized tomography scans at the baseline and at 2, 4, and 6 weeks, and measured the volume of newly formed bone (NFB), bone mineral density (BMD) of NFB, and the closure percentage of the NFB area. Histological and histomorphometric analyses were performed at 6 weeks.

Results

Real-time assessment revealed notably higher levels of bone volume, BMD, and closure percentage in the NFB area for the groups treated with ACM/BMP-9 compared to the control and ACM groups. Within the high concentration of BMP-9 group, the volume and BMD of NFB exhibited a significant increase at 6 weeks compared to baseline. Histological examination confirmed the existence of osteoblasts, osteocytes, and blood vessels within the NFB.

Conclusion

Considering the limitations of this research, the real-time evaluation finding indicates that ACM/BMP-9 effectively promotes bone formation in critical-size mandibular defects in rats.

Low-Intensity Pulsed Ultrasound Promotes BMP9 Induced Osteoblastic Differentiation in Rat Dedifferentiated Fat Cells

Dedifferentiated fat cells (DFATs) isolated from mature adipocytes have a multilineage differentiation capacity similar to mesenchymal stem cells and are considered as promising source of cells for tissue engineering. Bone morphogenetic protein 9 (BMP9) and low-intensity pulsed ultrasound (LIPUS) have been reported to stimulate bone formation both in vitro and in vivo. However, the combined effect of BMP9 and LIPUS on osteoblastic differentiation of DFATs has not been studied. After preparing DFATs from mature adipose tissue from rats, DFATs were treated with different doses of BMP9 and/or LIPUS. The effects on osteoblastic differentiation were assessed by changes in alkaline phosphatase (ALP) activity, mineralization/calcium deposition, and expression of bone related genes; Runx2, osterix, osteopontin. No significant differences for ALP activity, mineralization deposition, as well as expression for bone related genes were observed by LIPUS treatment alone while treatment with BMP9 induced osteoblastic differentiation of DFATs in a dose dependent manner. Further, co-treatment with BMP9 and LIPUS significantly increased osteoblastic differentiation of DFATs compared to those treated with BMP9 alone. In addition, upregulation for BMP9-receptor genes was observed by LIPUS treatment. Indomethacin, an inhibitor of prostaglandin synthesis, significantly inhibited the synergistic effect of BMP9 and LIPUS co-stimulation on osteoblastic differentiation of DFATs. LIPUS promotes BMP9 induced osteoblastic differentiation of DFATs in vitro and prostaglandins may be involved in this mechanism.

Resveratrol Synergistically Promotes BMP9-Induced Osteogenic Differentiation of Mesenchymal Stem Cells

Background. Mesenchymal stem cells (MSCs) differentiate into osteocytes, adipocytes, and chondrocytes. Resveratrol and bone morphogenetic protein 9 (BMP9) are known osteogenic induction factors of MSCs, but the effect of both resveratrol and BMP9 on osteogenesis is unknown. Herein, we explored whether resveratrol cooperates with BMP9 to improve osteogenic induction. Methods. The osteogenic induction of resveratrol and BMP9 on C3H10T1/2 cells was evaluated by detecting the staining and activity of the early osteogenic marker alkaline phosphatase (ALP). In addition, the late osteogenic effect was measured by the mRNA and protein levels of osteogenic markers, such as osteopontin (OPN) and osteocalcin (OCN). To assess the bone formation function of resveratrol plus BMP9 in vivo, we transplanted BMP9-infected C3H10T1/2 cells into nude mice followed by intragastric injection of resveratrol. Western blot (WB) analysis was utilized to elucidate the mechanism of resveratrol plus BMP9. Results. Resveratrol not only enhanced osteogenic induction alone but also improved BMP9-induced ALP at 3, 5, and 7 d postinduction. Both the early osteogenic markers (ALP, Runx2, and SP7) and the late osteogenic markers (OPN and OCN) were significantly increased when resveratrol was combined with BMP9. The fetal limb explant culture further verified these results. The in vivo bone formation experiment, which involved transplanting BMP9-overexpressing C3H10T1/2 cells into nude mice, also confirmed that resveratrol synergistically enhanced the BMP9-induced bone formation function. Resveratrol phosphorylated adenosine monophosphate- (AMP-) activated protein kinase (AMPK) and stimulated autophagy, but these effects were abolished by inhibiting AMPK and Beclin1 using an inhibitor or siRNA. Conclusions. Resveratrol combined with BMP9 significantly improves the osteogenic induction of C3H10T1/2 cells by activating AMPK and autophagy.

Osteoinductive potential of recombinant BMP-9 in bone defects of mice treated with antiresorptive agents

The aim of the present study was to investigate the effects of recombinant human (rh)BMP-9 on bone regenerative potential in a mouse model of antibody-mediated antiresorptive therapy (AMART). A monoclonal anti-murine receptor activator of nuclear factor-kappa B ligand (RANKL) antibody (mAb) was used to create an AMART model in mice. rhBMP-9 combined with collagen membrane was implanted in calvarial defects in mAb-treated mice. After 4 weeks, the bone formative potential in the defects was evaluated by micro-computed tomography and histological approaches. The groups implanted with rhBMP-9-containing collagen membranes demonstrated substantial osteopromotive potential, with significantly greater new bone volume (Sham + BMP-9 group; 0.86 ± 0.29 mm³ and mAb + BMP-9 group; 0.64 ± 0.16 mm³) than control PBS-membranes (Sham + PBS group; 0.44 ± 0.29 mm³ and mAb + PBS group; 0.24 ± 0.12 mm³) in both sham and mAb-treated mice. In line with in vivo study, bone marrow cells isolated from both sham and mAb-treated mice confirmed greater osteogenic potential upon stimulation with rhBMP-9 in vitro. These findings suggest for the first time that local rhBMP-9 administration might be a strategy to accelerate bone regeneration in the context of AMART.

Effect of interleukin-1β on bone morphogenetic protein-9-induced osteoblastic differentiation of human periodontal ligament fibroblasts

Bone morphogenetic protein-9 (BMP-9) has been shown to potently induce osteoblastic differentiation of periodontal ligament fibroblasts (PDLFs) and may be a candidate therapeutic agent for periodontal tissue healing/regeneration, but the effect of the inflammatory environment of periodontitis on such approaches is unclear. We investigated whether interleukin-1β (IL-1β) affected BMP-9-mediated osteoblastic differentiation of human (h) PDLFs. IL-1β suppressed BMP-9-induced osteogenic differentiation of hPDLFs, as evidenced by reduced alkaline phosphatase (ALP) activity and mineralization, and the downregulated expression of BMP-9-mediated bone-related genes, RUNX2, SP7, IBSP, and SPP1. In hPDLFs, with or without BMP-9, IL-1β increased the protein expression of activin A, a BMP-9 antagonist, and decreased follistatin protein, an antagonist of activin A. Similarly, IL-1β upregulated the expression of the activin A gene and downregulated that of the follistatin gene. Notably, follistatin re-established BMP-9-induced ALP activity suppressed by IL-1β. Activin A inhibited the expression of BMP-9-responsive genes and BMP-9-induced ALP activity, while follistatin re-established them. Finally, extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and nuclear factor-kappa B (NF-κB) inhibition significantly blocked IL-1β-induced activin A gene expression. Our data indicate that IL-1β inhibits BMP-9-induced osteoblastic differentiation of hPDLFs, possibly by promoting activin A production via the ERK1/2, p38, and NF-κB pathways.

Identification of key genes and pathways of BMP-9-induced osteogenic differentiation of mesenchymal stem cells by integrated bioinformatics analysis

Background

The purpose of present study was to identify the differentially expressed genes (DEGs) associated with BMP-9-induced osteogenic differentiation of mesenchymal stem cells (MSCs) by using bioinformatics methods.

Methods

Gene expression profiles of BMP-9-induced MSCs were compared between with GFP-induced MSCs and BMP-9-induced MSCs. GSE48882 containing two groups of gene expression profiles, 3 GFP-induced MSC samples and 3 from BMP-9-induced MSCs, was downloaded from the Gene Expression Omnibus (GEO) database. Then, DEGs were clustered based on functions and signaling pathways with significant enrichment analysis. Pathway enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) demonstrated that the identified DEGs were potentially involved in cytoplasm, nucleus, and extracellular exosome signaling pathway.

Results

A total of 1967 DEGs (1029 upregulated and 938 downregulated) were identified from GSE48882 datasets. R/Bioconductor package limma was used to identify the DEGs. Further analysis revealed that there were 35 common DEGs observed between the samples. GO function and KEGG pathway enrichment analysis, among which endoplasmic reticulum, protein export, RNA transport, and apoptosis was the most significant dysregulated pathway. The result of protein-protein interaction (PPI) network modules demonstrated that the Hspa5, P4hb, Sec61a1, Smarca2, Pdia3, Dnajc3, Hyou1, Smad7, Derl1, and Surf4 were the high-degree hub nodes.

Conclusion

Taken above, using integrated bioinformatical analysis, we have identified DEGs candidate genes and pathways in BMP-9 induced MSCs, which could improve our understanding of the key genes and pathways for BMP-9-induced osteogenic of MSCs.

Enhanced bone formation of calvarial bone defects by low-intensity pulsed ultrasound and recombinant human bone morphogenetic protein-9: a preliminary experimental study in rats

OBJECTIVES

The aim of this study was to evaluate the combined effects of recombinant human bone morphogenetic protein - 9 (rhBMP-9) loaded onto absorbable collagen sponges (ACS) and low-intensity pulsed ultrasound (LIPUS) on bone formation in rat calvarial defects.

MATERIALS AND METHODS

Circular calvarial defects were surgically created in 18 Wistar rats, which were divided into LIPUS-applied (+) and LIPUS-non-applied (-) groups. The 36 defects in each group received ACS implantation (ACS group), ACS with rhBMP-9 (rhBMP-9/ACS group), or surgical control (control group), yielding the following six groups: ACS (+/-), rhBMP-9/ACS (+/-), and control (+/-). The LIPUS-applied groups received daily LIPUS exposure starting immediately after surgery. At 4 weeks, animals were sacrificed and their defects were investigated histologically and by microcomputed tomography.

RESULTS

Postoperative clinical healing was uneventful at all sites. More new bone was observed in the LIPUS-applied groups compared with the LIPUS-non-applied groups. Newly formed bone area (NBA)/total defect area (TA) in the ACS (+) group (46.49 ± 7.56%) was significantly greater than that observed in the ACS (-) (34.31 ± 5.68%) and control (-) (31.13 ± 6.74%) groups (p < 0.05). The rhBMP-9/ACS (+) group exhibited significantly greater bone volume, NBA, and NBA/TA than the rhBMP-9/ACS (-) group (2.46 ± 0.65 mm³ vs. 1.76 ± 0.44 mm³, 1.25 ± 0.31 mm² vs. 0.88 ± 0.22 mm², and 62.80 ± 11.87% vs. 42.66 ± 7.03%, respectively) (p < 0.05). Furthermore, the rhBMP-9/ ACS (+) group showed the highest level of bone formation among all groups.

CONCLUSION

Within their limits, it can be concluded that LIPUS had osteopromotive potential and enhanced rhBMP-9-induced bone formation in calvarial defects of rats.

CLINICAL RELEVANCE

The use of rhBMP-9 with LIPUS stimulation can be a potential bone regenerative therapy for craniofacial/peri-implant bone defects.

A collagen-based hydrogel containing tacrolimus for bone tissue engineering

Bone tissue engineering aims to develop bone graft structure that can heal bone defects without using autografts or allografts. The current study was conducted to promote bone regeneration using a collagen type I hydrogel containing tacrolimus. For this purpose, different amounts of tacrolimus (10 μg/ml, 100 μg/ml, and 1000 μg/ml) were loaded into the hydrogel. The resulting drug-loaded hydrogels were characterized for their porosity, swelling capacity, weight loss, drug release, blood compatibility, and cell proliferation (MTT). For functional analysis, the developed hydrogel surrounded by a film made of gelatin and polycaprolactone (PCL) was administrated in the calvarias defect of Wistar rats. The results indicated that the hydrogel has a porosity of 89.2 ± 12.5% and an appropriate swelling, drug release, and blood compatibility behavior. The in vitro results indicated that the collagen hydrogel containing 1000 μg tacrolimus was adequate in terms of cell proliferation. Finally, in vivo studies provided some evidence of the potential of the developed hydrogel for bone healing.

FK506 Induces Ligand-Independent Activation of the Bone Morphogenetic Protein Pathway and Osteogenesis

Osteoinductive bone morphogenetic proteins (BMPs), including BMP-2, have a unique capability of mediating bone formation both in orthotopic and ectopic locations. Immunosuppresive macrolides have been shown to potentiate BMP-2 activity through FKBP12, but these have yet to translate to effective osteoinductive therapies. Herein, we show the osteogenic activity of FK506 as a stand-alone agent in direct comparison to BMP-2 both in vitro and in vivo. FK506 was capable of producing stand-alone alkaline phosphatase induction in C2C12 cells comparable to that seen with rhBMP-2. FK506 treatment activated the BMP receptor, as shown by increased pSmad1/5 levels, and produced significantly higher mRNA levels of the early response genes in BMP and TGF-β pathways. Additionally, the FK506 induction of alkaline phosphatase was shown to be resistant to Noggin treatment. In vivo osteogenic activity of FK506 was tested by local delivery on a collagen sponge in an ectopic subcutaneous implantation model in the rat. Dose responses of FK506 showed increasing levels of ectopic mineralization comparable to the mineral volume produced by BMP-2 delivery. These findings suggest that the use of FK506 can enhance osteoblastic differentiation in vitro and can induce mineralization when delivered locally in vivo.

Superior bone-inducing potential of rhBMP9 compared to rhBMP2

Recombinant human bone morphogenic protein (rhBMP) 9 has recently been reported to have more osteopromotive potential in vitro when compared to rhBMP2. The aim of the present study was to investigate the bone-inducing potential of rhBMP2 and rhBMP9. We compared rhBMP2, rhBMP7, and rhBMP9 at five different concentrations and showed convincingly that rhBMP9 possesses much greater potential for osteoblast differentiation even at 20 times lower concentrations in vitro. We further show that Noggin, an inhibitor for rhBMP2-induced osteogenesis, did not alter rhBMP9-induced osteogenesis. Thereafter, we show for the first time that rhBMP9 loaded onto atelo-collagen membranes is osteoinductive and has greater potential to form ectopic bone formation when compared to rhBMP2 even at four times lower doses. Similarly new bone formation of rhBMP2 and 9 when loaded on deproteinized bovine bone mineral (DBBM) was investigated in a rabbit calvarial defect. At 8 weeks, both rhBMP2 and rhBMP9 induced significantly higher new bone formation when compared to DBBM alone samples. Interestingly, once again four times lower dose of rhBMP9 group induced comparable or even greater levels of new bone height and new bone area when compared to the rhBMP2 group. The present study revealed that (1) rhBMP9 is capable of inducing ectopic new bone formation in vivo and (2) up to four times lower doses of rhBMP9 may be utilized to regenerate same-size bone defects when compared to rhBMP2. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1561-1574, 2018.

Transdifferentiation of adipocytes to osteoblasts: potential for orthopaedic treatment

OBJECTIVES

As both adipocytes and osteoblasts originate from the same pool of mesenchymal stem cells, increasing clinical evidence has emerged of the plasticity between the two lineages. For instance, the downregulation of osteoblast differentiation and upregulation of adipogenesis are common features of conditions such as multiple myeloma, obesity and drug-induced bone loss in diabetes mellitus. However, despite in-vitro and in-vivo observations of adipocyte transdifferentiation into osteoblasts, little is known of the underlying mechanisms.

KEY FINDINGS

This review summarises the current knowledge of this particular transdifferentiation process whereby the Wnt/β-catenin signalling pathway and Runx2 overexpression have been postulated to play a critical role.

SUMMARY

Furthermore, due to the possibility of a novel therapy in the treatment of bone conditions, a number of agents with the potential to induce adipo-to-osteoblast transdifferentiation have been investigated such as all-trans retinoic acid, bone morphogenetic protein-9 and vascular endothelial growth factor.

Bone healing capabilities of recombinant human bone morphogenetic protein-9 (rhBMP-9) with a chitosan or collagen carrier in rat calvarial defects

The aim of this study was to examine the effects of recombinant human BMP-9 (rhBMP-9) with chitosan sponge (ChiS) or absorbable collagen sponge (ACS) on bone formation in rat calvarial defects. The defects were treated by one of the following implantations: ChiS, rhBMP-9/ChiS, ACS, rhBMP-9/ACS and no implantation. The animals were euthanized at 8 weeks for histological evaluation. The percentage of defect closure (DC) in the rhBMP-9/ACS group was significantly greater than that in the ACS group. The rhBMP-9/ACS group demonstrated the highest level of DC among all the groups. The newly formed bone area (NBA) and NBA/total area in the ChiS-implanted groups and in the rhBMP-9/ACS group were significantly greater compared with those in the ACS group. It can be concluded that rhBMP-9/ACS has a potential to induce bone formation in rat calvarial defects. Further studies are required to elucidate the mechanism of bone formation induced by rhBMP-9.

Osteogenic potency of dedifferentiated fat cells isolated from elderly people with osteoporosis

Mature adipocytes are the major cell type in adipose tissue. This study aimed to explore the osteogenic potency of dedifferentiated fat cells obtained from osteoporotic patients (opDFATs) in vitro and in vivo. Mature adipocytes and adipose-derived stem cells (opASCs) were harvested from subcutaneous adipose tissue. Mature adipocytes were dedifferentiated to produce opDFATs by the ceiling culture method. OpDFATs were osteogenically induced in vitro with opASCs as a control. Cell growth, alkaline phosphatase (ALPase) activity and cell mineralization were determined, and expression levels of osteogenesis-specific genes (collagen I, osteocalcin and bone sialoprotein) were analyzed using quantitative reverse transcription polymerase chain reaction. After 14 days, the opDFATs were combined with a poly(lactide-co-glycolide)-β-tricalcium phosphate porous scaffold after being suspended in collagen I gel and implanted into nude mice for 4 weeks prior to histological analysis. Unilocular lipid droplets in mature adipocytes gradually split into smaller droplets and disappeared from the cytoplasm. Mature adipocytes dedifferentiated to opDFATs and cell morphology changed from spherical to elongated. High levels of ALPase and cell mineralization were observed in opDFATs by staining. No significant differences were found between the growth curves, ALPase activity, cell mineralization and expression levels of osteogenesis-specific genes between opDFATS and opASCs. After implantation for 4 weeks, new bone tissue was observed histologically in the opDFATs-based biocomposite. OpDFATs are implicated as a novel type of seed cell for bone tissue engineering based on their osteogenic potency and higher abundance in adipose tissue compared with opASCs.

Comparison of the effects of recombinant human bone morphogenetic protein-2 and -9 on bone formation in rat calvarial critical-size defects

OBJECTIVES

Among bone morphogenetic protein (BMP) family members, BMP-2 and BMP-9 have demonstrated potent osteoinductive potential. However, in vivo differences in their potential for bone regeneration remain unclear. The present study aimed to compare the effects of recombinant human (rh) BMP-2 and rhBMP-9 on bone formation in rat calvarial critical-size defects (CSD).

MATERIALS AND METHODS

Twenty-eight Wistar rats surgically received two calvarial defects bilaterally in each parietal bone. Defects (n = 56) were allocated into four groups: absorbable collagen sponge (ACS) alone, rhBMP-2 with ACS (rhBMP-2/ACS), rhBMP-9/ACS, or sham surgery (control), on the condition that the treatments of rhBMP-2/ACS and rhBMP-9/ACS, or the same treatments were not included in the same animal. Animals were sacrificed at 2 and 8 weeks post-surgery. The calvarial defects were analyzed for bone volume (BV) by micro-computed tomography and for percentages of defect closure (DC/DL), newly formed bone area (NBA/TA), bone marrow area (BMA/NBA), adipose tissue area (ATA/NBA), central bone height (CBH), and marginal bone height (MBH) by histomorphometric analysis.

RESULTS

The BV in the rhBMP-2/ACS group (5.44 ± 3.65 mm³, n = 7) was greater than the other groups at 2 weeks post-surgery, and the rhBMP-2/ACS and rhBMP-9/ACS groups (18.17 ± 2.51 and 16.30 ± 2.46 mm³, n = 7, respectively) demonstrated significantly greater amounts of BV compared with the control and ACS groups (6.02 ± 2.90 and 9.30 ± 2.75 mm³, n = 7, respectively) at 8 weeks post-surgery. The rhBMP-2/ACS and rhBMP-9/ACS groups significantly induced new bone formation compared to the control and ACS groups at 8 weeks post-surgery. However, there were no statistically significant differences found between the rhBMP-2/ACS and rhBMP-9/ACS groups in any of the histomorphometric parameters. The ATA/NBA in the rhBMP-2/ACS group (9.24 ± 3.72%, n = 7) was the highest among the treatment groups at 8 weeks post-surgery.

CONCLUSIONS

Within the limits of this study, it can be concluded that rhBMP-2/ACS induced a slight early increase in new bone formation at 2 weeks and that rhBMP-9/ACS provided comparable new bone formation to rhBMP-2/ACS with less adipose tissues after a healing period of 8 weeks in rat CSD.

CLINICAL RELEVANCE

RhBMP-9/ACS treatment provided new bone formation with less adipose tissues compared with rhBMP-2/ACS.

Absorbable collagen sponges loaded with recombinant bone morphogenetic protein 9 induces greater osteoblast differentiation when compared to bone morphogenetic protein 2

The use of growth factors for the regeneration of soft and hard tissues has been utilized extensively in dental medicine over the past decade. Recently our group found that recombinant human bone morphogenetic protein 9 (rhBMP9) was more osteopromotive than recombinant human bone morphogenetic protein 2 (rhBMP2) when combined with a deprotenized bovine bone mineral bone grafting material. The aim of the present in vitro study was to evaluate the regenerative potential of an absorbable collagen sponge(ACS) specifically designed for extraction socket healing loaded with rhBMP9 when compared to rhBMP2. The adsorption and release kinetics of rhBMP2 and rhBMP9 were first investigated by enzyme-linked immunosorbent assay quantification. Then, the cellular effects of stromal cell line (ST2) preosteoblasts were investigated utilizing four groups including rhBMP2 and rhBMP9 at both low(10 ng/ml) and high(100 ng/ml) concentrations loaded onto ACS. Cellular attachment(8 hours) and proliferation(1, 3, and 5 days) as well as osteoblast differentiation were investigated by real-time polymerase chain reaction (PCR) at 3 and 14 days, alkaline phosphatase (ALP) activity at 7 days, and alizarin red staining at 14 days. ACS fully adsorbed both rhBMP2 and rhBMP9 that were slowly released up to 10 days. Although neither rhBMP2 nor rhBMP9 had any effects on cell attachment or proliferation, pronounced effects were observed on osteoblast differentiation. ALP activity was increased seven-fold with rhBMP2-high, whereas a marked 10-fold and 20-fold increase was observed with rhBMP9-low and high loaded to ACS, respectively. Furthermore, mRNA levels of collagen1, ALP, bone sialoprotein, and osteocalcin were all significantly higher for rhBMP9 when compared to control or rhBMP2 groups. Alizarin red staining further confirmed that rhBMP9-low and high demonstrated marked increases in mineralization potential when compared to rhBMP2-high. The results demonstrate the marked effect of rhBMP9 on osteoblast differentiation when combined with ACS in comparison to rhBMP2 at doses as much as 10 times lower. Further in vivo studies are necessary to investigate whether the regenerative potential is equally as potent.

Recombinant human bone morphogenetic protein (rhBMP)9 induces osteoblast differentiation when combined with demineralized freeze-dried bone allografts (DFDBAs) or biphasic calcium phosphate (BCP)

OBJECTIVES

Recently, recombinant human bone morphogenetic protein 9 (rhBMP9) has been characterized as one of the most osteogenic growth factors among the 15 human BMPs. The aim of the present study was to investigate the effects of rhBMP9 in comparison to the clinically utilized rhBMP2 on in vitro cell behavior when combined with two bone graft materials including demineralized freeze-dried bone allografts (DFDBAs) and biphasic calcium phosphate (BCP).

MATERIALS AND METHODS

The absorption and release kinetics of rhBMPs from DFDBA and BCP were investigated by ELISA. Moreover, murine bone stromal ST2 cell behavior was investigated on DFDBA or BCP seeded on (1) graft only, (2) rhBMP2 (10 ng/ml), (3) rhBMP2 (100 ng/ml), (4) rhBMP9 (10 ng/ml), and (5) rhBMP9 (100 ng/ml). The effects of rhBMPs on DFDBA and BCP were assessed for cell adhesion, proliferation, and osteoblast differentiation by alkaline phosphatase (ALP) activity, alizarin red staining, and real-time PCR for genes encoding Runx2, ALP, and bone sialoprotein (BSP).

RESULTS

While both BMPs were gradually released from DFDBA and BCP over time, significantly higher adsorption was observed on BCP when compared to DFDBA. Cell attachment and proliferation was higher on BCP with little influence of either rhBMP2/9. Despite rhBMPs having relatively no effect on cell attachment/proliferation, a pronounced and marked effect was observed on osteoblast differentiation for both rhBMP2/9. Interestingly, it was observed that rhBMP9 induced significantly higher ALP activity, alizarin red staining, and messenger RNA (mRNA) levels of ALP and BSP when compared to rhBMP2. Our results also revealed higher differentiation for rhBMP2/9 with BCP when compared to DFDBA most likely as a result of higher growth factor adsorption.

CONCLUSION

While both rhBMP2/9 combined with DFDBA or BCP induced osteoblast differentiation, rhBMP9 induced greater osteoblast differentiation when compared to rhBMP2.

CLINICAL RELEVANCE

rhBMP9 may be a recombinant growth factor with higher potential to induce new bone formation when compared to rhBMP2. Further in vivo studies are necessary to characterize its regenerative potential in various animal models.

Osteogenic potential of recombinant human bone morphogenetic protein-9/absorbable collagen sponge (rhBMP-9/ACS) in rat critical size calvarial defects

OBJECTIVES

It has been reported that bone morphogenetic protein (BMP)-9 has potent osteoinductive properties among the BMP family by adenovirus-transfection experiments. We very recently reported that absorbable collagen sponge (ACS) as a carrier for recombinant human (rh) BMP-9, compared with chitosan sponge, was suitable for inducing bone healing/regeneration by BMP-9 in a rat calvarial defect model. The aim of this study was to evaluate different doses of rhBMP-9/ACS on new bone formation in rat critical size calvarial defects.

MATERIALS AND METHODS

Bilateral calvarial defects (n = 32) were surgically created in 16 wistar rats and randomly filled with one of the following materials: (1) absorbable collagen sponge (ACS) alone; (2) 1 μg-rhBMP-9/ACS (L-rhBMP-9/ACS); (3) 5 μg-rhBMP-9/ACS (H-rhBMP-9/ACS); and (4) blank defects (control). The animals were sacrificed 8 weeks postsurgery for radiographic and histomorphometric analyses.

RESULTS

Bone volume and defect closure were statistically higher in the rhBMP-9/ACS-implanted (L-rhBMP-9/ACS and H-rhBMP-9/ACS) groups when compared with ACS-alone group (p < 0.05). Furthermore, defects filled with H-rhBMP-9/ACS showed the highest levels of newly formed bone area (NBA) and NBA/total defect area among all groups. No significant differences in any of the radiographic and histometric parameters could be observed between both concentrations of rhBMP-9.

CONCLUSIONS

Within the limits of this study, it can be concluded that rhBMP-9/ACS-induced bone formation can be reached with as little as 1 μg/site in rat critical size calvarial defects.

CLINICAL RELEVANCE

RhBMP-9 could be a potential therapeutic growth factor for future bone regenerative procedures.

Potential differentiation ability of gingiva originated human mesenchymal stem cell in the presence of tacrolimus

The aim of the present study is to evaluate the potential differentiation ability of gingiva originated human mesenchymal stem cell in the presence of tacrolimus. Tacrolimus-loaded poly(lactic-co-glycolic acid) microspheres were prepared using electrospraying technique. In vitro release study of tacrolimus-loaded poly(lactic-co-glycolic acid) microspheres was performed in phosphate-buffered saline (pH 7.4). Gingiva-derived stem cells were isolated and incubated with tacrolimus or tacrolimus-loaded microspheres. Release study of the microspheres revealed prolonged release profiles of tacrolimus without any significant initial burst release. The microsphere itself did not affect the morphology of the mesenchymal stem cells, and cell morphology was retained after incubation with microspheres loaded with tacrolimus at 1 μg/mL to 10 μg/mL. Cultures grown in the presence of microspheres loaded with tacrolimus at 1 μg/mL showed the highest mineralization. Alkaline phosphatase activity increased with an increase in incubation time. The highest expression of pSmad1/5 was achieved in the group receiving tacrolimus 0.1 μg/mL every third day, and the highest expression of osteocalcin was achieved in the group receiving 1 μg/mL every third day. Biodegradable poly(lactic-co-glycolic acid)-based microspheres loaded with tacrolimus promoted mineralization. Microspheres loaded with tacrolimus may be applied for increased osteoblastic differentiation.

Chimeric Allografts Induced by Short-Term Treatment With Stem Cell-Mobilizing Agents Result in Long-Term Kidney Transplant Survival Without Immunosuppression: A Study in Rats

Transplant tolerance allowing the elimination of lifelong immunosuppression has been the goal of research for 60 years. The induction of mixed chimerism has shown promise and has been extended successfully to large animals and to the clinic; however, it remains cumbersome and requires heavy early immunosuppression. In this study, we reported that four injections of AMD3100, a CXCR4 antagonist, plus eight injections of low-dose FK506 (0.05 mg/kg per day) in the first week after kidney transplantation extended survival, but death from renal failure occurred at 30-90 days. Repeating the same course of AMD3100 and FK506 at 1, 2 and 3 mo after transplant resulted in 92% allograft acceptance (n = 12) at 7 mo, normal kidney function and histology with no further treatment. Transplant acceptance was associated with the influx of host stem cells, resulting in a hybrid kidney and a modulated host immune response. Confirmation of these results could initiate a paradigm shift in posttransplant therapy.

Nanoparticulate Mineralized Collagen Scaffolds and BMP-9 Induce a Long-Term Bone Cartilage Construct in Human Mesenchymal Stem Cells

Engineering the osteochondral junction requires fabrication of a microenvironment that supports both osteogenesis and chondrogenesis. Multiphasic scaffold strategies utilizing a combination of soluble factors and extracellular matrix components are ideally suited for such applications. In this work, the contribution of an osteogenic nanoparticulate mineralized glycosaminoglycan scaffold (MC-GAG) and a dually chondrogenic and osteogenic growth factor, BMP-9, in the differentiation of primary human mesenchymal stem cells (hMSCs) is evaluated. Although 2D cultures demonstrate alkaline phosphatase activity and mineralization of hMSCs induced by BMP-9, MC-GAG scaffolds do not demonstrate significant differences in the collagen I expression, osteopontin expression, or mineralization. Instead, BMP-9 increases expression of collagen II, Sox9, aggrecan (ACAN), and cartilage oligomeric protein. However, the hypertrophic chondrocyte marker, collagen X, is not elevated with BMP-9 treatment. In addition, histologic analyses demonstrate that while BMP-9 does not increase mineralization, BMP-9 treatment results in an increase of sulfated glycosaminoglycans. Thus, the combination of BMP-9 and MC-GAG stimulates chondrocytic and osteogenic differentiation of hMSCs.

Effects of tacrolimus on morphology, proliferation and differentiation of mesenchymal stem cells derived from gingiva tissue

Tacrolimus is a 23-membered macrolide lactone with potent immunosuppressive activity that is effective in the prophylaxis of organ rejection following kidney, heart and liver transplantation. Tacrolimus also exerts a variety of actions on bone metabolism. The aim of the present study was to evaluate the effects of different concentrations of tacrolimus on the morphology and viability of human stem cells derived from the gingiva. Gingival-derived stem cells were grown in the presence of tacrolimus at final concentrations ranging from 0.001 to 100 µg/ml. The morphology of the cells was viewed under an inverted microscope and the cell viability was analyzed using Cell Counting kit-8 (CCK-8) on days 1, 3, 5 and 7. Alizarin Red S staining was used to assess mineralization of treated cells. The control group showed spindle-shaped, fibroblast-like morphology and the shapes of the cells in 0.001, 0.01, 0.1, 1 and 10 µg/ml tacrolimus were similar to those of the control group. All groups except the 100 µg/ml group showed increased cell proliferation over time. Cultures grown in the presence of tacrolimus at 0.001, 0.01, 0.1, 1 and 10 µg/ml were not identified to be significantly different compared with the control at days 1, 3 and 5 using the CCK-8 assays. Increased mineralized deposits were noted with increased incubation time. Treatment with tacrolimus from 0.001 to 1 µg/ml led to an increase in mineralization compared with the control group. Within the limits of this study, tacrolimus at the tested concentrations (ranging from 0.001 to 10 µg/ml) did not result in differences in the viability of stem cells derived from gingiva; however it did enhance osteogenic differentiation of the stem cells.

Dedifferentiated fat cells: A cell source for regenerative medicine

The identification of an ideal cell source for tissue regeneration remains a challenge in the stem cell field. The ability of progeny cells to differentiate into other cell types is important for the processes of tissue reconstruction and tissue engineering and has clinical, biochemical or molecular implications. The adaptation of stem cells from adipose tissue for use in regenerative medicine has created a new role for adipocytes. Mature adipocytes can easily be isolated from adipose cell suspensions and allowed to dedifferentiate into lipid-free multipotent cells, referred to as dedifferentiated fat (DFAT) cells. Compared to other adult stem cells, the DFAT cells have unique advantages in their abundance, ease of isolation and homogeneity. Under proper condition in vitro and in vivo, the DFAT cells have exhibited adipogenic, osteogenic, chondrogenic, cardiomyogenc, angiogenic, myogenic, and neurogenic potentials. In this review, we first discuss the phenomena of dedifferentiation and transdifferentiation of cells, and then dedifferentiation of adipocytes in particular. Understanding the dedifferentiation process itself may contribute to our knowledge of normal growth processes, as well as mechanisms of disease. Second, we highlight new developments in DFAT cell culture and summarize the current understanding of DFAT cell properties. The unique features of DFAT cells are promising for clinical applications such as tissue regeneration.

Application of Green Tea Catechin for Inducing the Osteogenic Differentiation of Human Dedifferentiated Fat Cells in Vitro

Despite advances in stem cell biology, there are few effective techniques to promote the osteogenic differentiation of human primary dedifferentiated fat (DFAT) cells. We attempted to investigate whether epigallocatechin-3-gallate (EGCG), the main component of green tea catechin, facilitates early osteogenic differentiation and mineralization on DFAT cells in vitro. DFAT cells were treated with EGCG (1.25-10 μM) in osteogenic medium (OM) with or without 100 nM dexamethasone (Dex) for 12 days (hereafter two osteogenic media were designated as OM(Dex) and OM). Supplementation of 1.25 μM EGCG to both the media effectively increased the mRNA expression of collagen 1 (COL1A1) and runt-related transcription factor 2 (RUNX2) and also increased proliferation and mineralization. Compared to OM(Dex) with EGCG, OM with EGCG induced earlier expression for COL1A1 and RUNX2 at day 1 and higher mineralization level at day 12. OM(Dex) with 10 μM EGCG remarkably hampered the proliferation of the DFAT cells. These results suggest that OM(without Dex) with EGCG might be a preferable medium to promote proliferation and to induce osteoblast differentiation of DFAT cells. Our findings provide an insight for the combinatory use of EGCG and DFAT cells for bone regeneration and stem cell-based therapy.

Potential roles of bone morphogenetic protein (BMP)-9 in human liver diseases

Bone morphogenetic proteins (BMP-2 to BMP-15) belong to the Transforming Growth Factor (TGF)-β superfamily and, besides their well-documented roles during embryogenesis and bone formation, some of them have recently been described to be involved in the pathogenesis of different organs, including the liver. The role of BMPs in liver damage responses including hepatocellular carcinoma (HCC) development has only begun to be addressed and strong evidence supports the concept of a pro-tumorigenic role of BMP signaling in HCC cells. BMP-9 (also termed Growth and Differentiation Factor (GDF)-2) represents the most recently discovered member of the BMP family. We have previously demonstrated that in HCC patient samples BMP-9 expression was positively associated with the tumor seize (“T stage”) and that it enhanced cell migration and induced epithelial to mesenchymal transition (EMT) in HCC cells in vitro. In another study we recently found that BMP-9 promotes growth in HCC cells, but not in non-transformed hepatocytes. Published as well as unpublished results obtained with primary hepatocytes support the concept of a dual function of BMP-9 in the liver: while in primary, non-malignant cells BMP-9 stabilizes the epithelial phenotype and inhibits proliferation, in HCC cells it induces cell growth and the acquisition of a migratory phenotype. In this review article we summarize current knowledge about BMPs in liver diseases, with special focus on the role of BMP-9 in HCC development and progression, that may provide new clues for a better understanding of the contribution of BMP-signaling to chronic liver diseases.