Bone-like nodules formed by human bone marrow stromal cells: comparative study and characterization

The Development of Polylactic Acid/Multi-Wall Carbon Nanotubes/Polyethylene Glycol Scaffolds for Bone Tissue Regeneration Application

Composite electrospun fibers were fabricated to develop drug loaded scaffolds to promote bone tissue regeneration. Multi-wall carbon nanotubes (MWCNTs) were incorporated to polylactic acid (PLA) to strengthen electrospun nanofibers. To modulate drug release behavior, different ratios of hydrophilic polyethylene glycol (PEG) were added to composite fibers. Glass transition temperature (Tg) can be reduced by the incorporated PEG to enhance the ductility of the nanofibers. The SEM images and the MTT results demonstrated that composite fibers are suitable scaffolds for cell adhesion and proliferation. Dexamethasone (DEX), an osteogenic inducer, was loaded to PLA/MWCNT/PEG fibers. The surface element analysis performed by XPS showed that fluorine of DEX in pristine PLA fibers was much higher than those of the MWCNT-containing fibers, suggesting that the pristine PLA fibers mainly load DEX on their surfaces, whereas MWCNTs can adsorb DEX with evenly distribution in nanofibers. Drug release experiments demonstrated that the release profiles of DEX were manipulated by the ratio of PEG, and that the more PEG in the nanofibers, the faster DEX was released. When rat bone marrow stromal cells (rBMSCs) were seeded on these nanofibers, the Alizarin Red S staining and calcium quantification results demonstrated that loaded DEX were released to promote osteogenic differentiation of rBMSCs and facilitate mineralized tissue formation. These results indicated that the DEX-loaded PLA/MWCNT/PEG nanofibers not only enhanced mechanical strength, but also promoted osteogenesis of stem cells via the continuous release of DEX. The nanofibers should be a potential scaffold for bone tissue engineering application.

Cell Condensation Triggers the Differentiation of Osteoblast Precursor Cells to Osteocyte-Like Cells

Though the three-dimensional (3D) in vitro culture system has received attention as a powerful tool for conducting biological research, in vitro bone formation and osteocyte differentiation studies have mostly been based on results obtained using two-dimensional (2D) culture systems. Here, we introduced a rotatory culture system to fabricate 3D spheroids, using mouse osteoblast precursor cells. These spheroids, incubated for 2 days without chemical induction by osteogenic supplements, exhibited notably up-regulated osteocyte marker levels; osteoblast marker levels were down-regulated, as compared to those of the conventional 2D monolayer model. The cell condensation achieved with the 3D spheroid structure triggered a greater level of differentiation of osteoblast precursor cells into osteocyte-like cells than that observed during chemical induction. Our study might imply that osteoblasts proliferate and become condensed at the targeted bone remodeling site, because of which osteoblasts achieved the capability to differentiate into osteocytes in vivo.

Tough and Immunosuppressive Titanium-Infiltrated Exoskeleton Matrices for Long-Term Endoskeleton Repair

Although biodegradable membranes are essential for effective bone repair, severe loss of mechanical stability because of rapid biodegradation, soft tissue invasion, and excessive immune response remain intrinsically problematic. Inspired by the exoskeleton-reinforcing strategy found in nature, we have produced a Ti-infiltrated chitin nanofibrous membrane. The membrane employs vapor-phase infiltration of metals, which often occurs during metal oxide atomic layer deposition (ALD) on organic substrates. This metal infiltration manifests anomalous mechanical improvement and stable integration with chitin without cytotoxicity and immunogenicity. The membrane exhibits both impressive toughness (∼13.3 MJ·m^-3) and high tensile strength (∼55.6 MPa), properties that are often mutually exclusive. More importantly, the membrane demonstrates notably enhanced resistance to biodegradation, remaining intact over the course of 12 weeks. It exhibits excellent osteointegrative performance and suppresses the immune response to pathogen-associated molecular pattern molecules indicated by IL-1β, IL-6, and granulocyte-macrophage colony-stimulating factor expression. We believe the excellent chemico-biological properties achieved with ALD treatment can provide insight for synergistic utilization of the polymers and ALD in medical applications.

GBR membrane of novel poly (butylene succinate-co-glycolate) co-polyester co-polymer for periodontal application

In periodontics, osteoconductive biodegradable guided bone regeneration (GBR) membranes with acceptable physico-mechanical properties are required to fix alveolar bone defects. The objectives of the present study were to produce and characterize a novel co-polyester—poly (butylene succinate-co-glycolate) (PBSGL), and fabricate a PBSGL membrane by electrospinning. We then aimed to evaluate the in vitro effect of the glycolate ratio on the biocompatibility and osteogenic differentiation of mesenchymal stem cells (MSCs), and evaluate in vivo bone regeneration using these membranes in rabbit calvarial defects by histology. Increasing the glycolate ratio of electrospun PBSGL membranes resulted in better cell attachment, greater cell metabolic activity, and enhanced osteogenic potential at both transcriptional and translational levels. Histologic and histomorphometric evaluations revealed further that bone defects covered with fibers of higher glycolate ratios showed more bone formation, with no adverse inflammatory response. These results suggest that novel PBSGL electrospun nanofibers show great promise as GBR membranes for bone regeneration.

Physical and Biological Modification of Polycaprolactone Electrospun Nanofiber by Panax Ginseng Extract for Bone Tissue Engineering Application

Medicinal plants as a therapeutic agent with osteogenic properties can enhance fracture-healing process. In this study, the osteo-inductive potential of Asian Panax Ginseng root extract within electrospun polycaprolactone (PCL) based nanofibers has been investigated. Scanning electron microscopy images revealed that all nanofibers were highly porous and beadles with average diameter ranging from 250 to 650 nm. The incorporation of ginseng extract improved the physical characteristics (i.e., hydrophilicity) of PCL nanofibers, as well as the mechanical properties. Although ginseng extract increased the degradation rate of pure PCL nanofibers, the porous structure and morphology of fibers did not change significantly after 42 days. It was found that nanofibrous scaffolds containing ginseng extract had higher proliferation (up to ~1.5 fold) compared to the pristine PCL. The qRT-PCR analysis demonstrated the addition of ginseng extract into PCL nanofibers induced significant expression of osteogenic genes (Osteocalcin, Runx-2 and Col-1) in MSCs in a concentration dependent manner. Moreover, higher calcium content, alkaline phosphatase activity and higher mineralization of MSCs were observed compared to the pristine PCL fibers. Our results indicated the promising potential of ginseng extract as an additive to enhance osteo-inductivity, mechanical and physical properties of PCL nanofibers for bone tissue engineering application.

Effect of organic acids on calcium phosphate nucleation and osteogenic differentiation of human mesenchymal stem cells on peptide functionalized nanofibers

Carboxylate-rich organic acids play an important role in controlling the growth of apatite crystals and the extent of mineralization in the natural bone. The objective of this work was to investigate the effect of organic acids on calcium phosphate (CaP) nucleation on nanofiber microsheets functionalized with a glutamic acid peptide and osteogenic differentiation of human mesenchymal stem cells (hMSCs) seeded on the CaP-nucleated microsheets. High molecular weight poly(dl-lactide) (DL-PLA) was mixed with low molecular weight L-PLA conjugated with Glu-Glu-Gly-Gly-Cys peptide, and the mixture was electrospun to generate aligned nanofiber microsheets. The nanofiber microsheets were incubated in a modified simulated body fluid (mSBF) supplemented with different organic acids for nucleation and growth of CaP crystals on the nanofibers. Organic acids included citric acid (CA), hydroxycitric acid (HCA), tartaric acid (TART), malic acid (MA), ascorbic acid (AsA), and salicylic acid (SalA). HCA microsheets had the highest CaP content at 240 ± 10% followed by TART and CA with 225 ± 8% and 225 ± 10%, respectively. The Ca/P ratio and percent crystallinity of the nucleated CaP in TART microsheets was closest to that of stoichiometric hydroxyapatite. The extent of CaP nucleation and growth on the nanofiber microsheets depended on the acidic strength and number of hydrogen-bonding hydroxyl groups of the organic acids. Compressive modulus and degradation of the CaP nucleated microsheets were related to percent crystallinity and CaP content. Osteogenic differentiation of hMSCs seeded on the microsheets and cultured in osteogenic medium increased only for those microsheets nucleated with CaP by incubation in CA or AsA-supplemented mSBF. Further, only CA microsheets stimulated bone nodule formation by the seeded hMSCs.

Transient 100 nM dexamethasone treatment reduces inter- and intraindividual variations in osteoblastic differentiation of bone marrow-derived human mesenchymal stem cells

The development of in vitro culturing techniques for osteoblastic differentiation of human mesenchymal stem cells (hMSC) is important for cell biology research and the development of tissue-engineering applications. Dexamethasone (Dex) is a commonly used supplement, but the optimal use of Dex treatment is still unclear. By adjusting the timing of Dex supplementation, the negative effects of long-term Dex treatment could be overcome. Transient Dex treatment could contribute toward minimizing broad donor variation, which is a major challenge. We compared the two most widely used Dex concentrations of 10 and 100 nM as transient or continuous treatment and studied inter- and intraindividual variations in osteoblastic differentiation of hMSC. Characterized bone marrow-derived hMSC from 17 female donors of different age groups were used. During osteoblastic induction, the cells were treated with 10 or 100 nM Dex either transiently for different time periods or continuously. Differentiation was evaluated by measuring alkaline phosphatase (ALP) activity and staining for ALP, von Kossa, collagen type I, and osteocalcin. Cell proliferation, cell viability, and apoptosis were also monitored. The strongest osteoblastic differentiation was observed when 100 nM Dex was present for the first week. In terms of inter- and intraindividual coefficients of variations, transient treatment with 100 nM Dex was superior to the other culture conditions and showed the lowest variations in all age groups. This study demonstrates that the temporary presence of 100 nM Dex during the first week of induction culture promotes hMSC osteoblastic differentiation and reduces inter- and intraindividual variations. With this protocol, we can reproducibly produce functional osteoblasts in vitro from the hMSC of different donor populations.

Effects of osteogenic differentiation inducers on in vitro expanded adult mesenchymal stromal cells

PURPOSE

For bone regeneration therapy using stem cells, well-defined ex vivo protocols to expand mesenchymal stromal cells (MSC), as well as assays to show their potential differentiation into the osteogenic lineage, are needed. Aim of this study was to analyze the role of the biochemical osteogenic inducers, i.e. ascorbic acid, dexamethasone, and ß-glycerophosphate, employed in the current protocols for osteogenic differentiation of MSC in vitro, to address the requirements for reliable differentiation systems.

METHODS

MSC were isolated from the bone marrow of donors (46-73 years of age) undergoing total hip replacement, and expanded in vitro. At confluence, MSC were cultured under four different conditions: α-MEM plus serum (basal medium or C1), basal medium plus ascorbate (C2), basal medium plus ascorbate and dexamethasone (C3), or basal medium plus ascorbate, dexamethasone and ß-glycerophosphate (C4). Morphology, proliferation, mineralization, alkaline phosphatase, collagen and expression of bone-related genes of MSC under the different media were analyzed at fixed time points.

RESULTS

MSC proliferation and the number of colony forming units were increased by ascorbic acid, whereas dexamethasone enhanced the proportion of ALP-positive CFU and was critical for mineral deposition. Runx-2 and type I collagen gene expression decreased along with additive-induced MSC differentiation, i.e. from C1 to C4, while ALP and osteocalcin were differently regulated.

CONCLUSION

Our findings support the role of different inducers on the sequential stages of MSC expansion and osteogenic differentiation in vitro, suggesting the addition of DEX following proliferation to ensure mineralization, as an index of in vivo osteogenic potency of human mesenchymal cells.

The enhanced performance of bone allografts using osteogenic-differentiated adipose-derived mesenchymal stem cells

Adipose tissue was only recently considered as a potential source of mesenchymal stem cells (MSCs) for bone tissue engineering. To improve the osteogenicity of acellular bone allografts, adipose MSCs (AMSCs) and bone marrow MSCs (BM-MSCs) at nondifferentiated and osteogenic-differentiated stages were investigated in vitro and in vivo. In vitro experiments demonstrated a superiority of AMSCs for proliferation (6.1±2.3 days vs. 9.0±1.9 days between each passage for BM-MSCs, respectively, P<0.001). A significantly higher T-cell depletion (revealed by mixed lymphocyte reaction, [MLR]) was found for AMSCs (vs. BM-MSCs) at both non- and differentiated stages. Although nondifferentiated AMSCs secreted a higher amount of vascular endothelial growth factor [VEGF] in vitro (between 24 and 72 h of incubation at 0.1-21% O(2)) than BM-MSCs (P<0.001), the osteogenic differentiation induced a significantly higher VEGF release by BM-MSCs at each condition (P<0.001). After implantation in the paraspinal muscles of nude rats, a significantly higher angiogenesis (histomorphometry for vessel development (P<0.005) and VEGF expression (P<0.001)) and osteogenesis (as revealed by osteocalcin expression (P<0.001) and micro-CT imagery for newly formed bone tissue (P<0.05)) were found for osteogenic-differentiated AMSCs in comparison to BM-MSCs after 30 days of implantation. Osteogenic-differentiated AMSCs are the best candidate to improve the angio-/osteogenicity of decellularized bone allografts.

Human mesenchymal stem cell proliferation and osteogenic differentiation during long-term ex vivo cultivation is not age dependent

Mesenchymal stem cells (MSCs) are of major clinical interest for the development of cell-based strategies to treat musculoskeletal diseases including critical-size bone defects caused by trauma, degenerative disorders, or infections. Elderly people mainly suffer from critical-size bone defects from the rising incidence of trauma, osteoporosis, and arthroplasties. In this study we investigated the influence of donor age on proliferation and osteogenic differentiation in long-term ex vivo cultures of primary human MSCs from patients in different age groups. Fifteen patients (8 men/7 women) comprised three age groups: (I) <50 years, (II) 50-65 years, and (III) >65 years. MSCs harvested from bone marrow derived from routine surgical procedures were isolated and cultured in standard medium over eight passages. Osteogenic differentiation was induced by dexamethasone (10 nM), ascorbic acid (300 μM), and β-glycerophosphate (3.5 mM). Osteogenic differentiation capacity of MSCs was quantified by alkaline phosphatase (ALP) activity, fluorescence-activated cell sorting (FACS) analysis of the surface markers CD9, CD90, CD54, CD166, CD105, CD44, and CD73, and RT-PCR for Coll I and II, Cbfa 1, ALP, OC, BSP1, and GAPDH genes characterized the phenotypic changes during monolayer expansion. In vitro chondrogenic differentiation was analyzed by immunohistochemistry and RT-PCR. Progenitor cells could be expanded in the long term from all bone marrow donations. FACS single staining analysis from MSCs showed no significant difference between the age groups. The surface antigen CD166 was predominantly found in all cell cultures independently of differentiation stage. Comparison of expanded and differentiated MSCs within a single age group showed that undifferentiated MSCs had higher CD44 levels. Osteogenic stimulation of MSCs was confirmed by measuring ALP activity. The highest ALP activity was found in probands of the age group >65 years. Additionally, we observed a tendency toward male-specific ALP increase during differentiation. Osteogenic marker gene expression in MSCs was detected by RT-PCR. No significant expression differences were detected between the three donor age groups. Micromass culture of MSCs resulted histologically and immunohistologically in a chondrogenic phenotype. Elderly osteoprogenitor cell donors are a highly clinically relevant patient population. In summary, cultivation leads to a reduced osteogenic differentiation capacity regardless of age. Because donor age does not affect osteogenic differentiation potential, it should not be used as an exclusion criterion for autologous transplantation of human adult MSCs.

The Src inhibitor dasatinib accelerates the differentiation of human bone marrow-derived mesenchymal stromal cells into osteoblasts

Background

The proto-oncogene Src is an important non-receptor protein tyrosine kinase involved in signaling pathways that control cell adhesion, growth, migration and differentiation. It negatively regulates osteoblast activity, and, as such, its inhibition is a potential means to prevent bone loss. Dasatinib is a new dual Src/Bcr-Abl tyrosine kinase inhibitor initially developed for the treatment of chronic myeloid leukemia. It has also shown promising results in preclinical studies in various solid tumors. However, its effects on the differentiation of human osteoblasts have never been examined.

Methods

We evaluated the effects of dasatinib on bone marrow-derived mesenchymal stromal cells (MSC) differentiation into osteoblasts, in the presence or absence of a mixture of dexamethasone, ascorbic acid and β-glycerophosphate (DAG) for up to 21 days. The differentiation kinetics was assessed by evaluating mineralization of the extracellular matrix, alkaline phosphatase (ALP) activity, and expression of osteoblastic markers (receptor activator of nuclear factor kappa B ligand [RANKL], bone sialoprotein [BSP], osteopontin [OPN]).

Results

Dasatinib significantly increased the activity of ALP and the level of calcium deposition in MSC cultured with DAG after, respectively, 7 and 14 days; it upregulated the expression of BSP and OPN genes independently of DAG; and it markedly downregulated the expression of RANKL gene and protein (decrease in RANKL/OPG ratio), the key factor that stimulates osteoclast differentiation and activity.

Conclusions

Our results suggest a dual role for dasatinib in both (i) stimulating osteoblast differentiation leading to a direct increase in bone formation, and (ii) downregulating RANKL synthesis by osteoblasts leading to an indirect inhibition of osteoclastogenesis. Thus, dasatinib is a potentially interesting candidate drug for the treatment of osteolysis through its dual effect on bone metabolism.

In vitro osteogenesis assays: influence of the primary cell source on alkaline phosphatase activity and mineralization

In trabecular bone fracture repair in vivo, osteogenesis occurs through endochondral ossification under hypoxic conditions, or through woven bone deposition in the vicinity of blood vessels. In vitro osteogenesis assays are routinely used to test osteoblastic responses to drugs, hormones, and biomaterials for bone and cartilage repair applications. These cell culture models recapitulate events that occur in woven bone synthesis, and are carried out using primary osteoblasts, osteoblast precursors such as bone marrow-derived mesenchymal stromal cells (BMSCs), or various osteoblast cell lines. With time in culture, cell differentiation is typically assessed by examining levels of alkaline phosphatase activity (an early osteoblast marker) and by evaluating the assembly of a collagen (type I)-containing fibrillar extracellular matrix that mineralizes. In this review, we have made a comparative analysis of published osteogenic assays using calvarial cells, calvaria-derived cell lines, and bone marrow stromal cells. In all of these cell types, alkaline phosphatase activity shows similar progression over time using a variety of osteogenic and mineralizing media conditions; however, levels of alkaline phosphatase activity are not proportional to observed mineralization levels.

In vitro behaviour of adult mesenchymal stem cells seeded on a bioactive glass ceramic in the SiO(2)-CaO-P(2)O(5) system

This work describes the evaluation of a glass ceramic (55S41C4P-1300) as a potential substrate for bone tissue engineering. For that purpose, the capacity of mesenchymal stem cells (MSCs), isolated from rabbit bone marrow, to adhere, proliferate and differentiate into osteoblast (OBs) with or without 55S41C4P-1300 was investigated. Two types of culture medium, i.e. growth medium (GM) and osteogenic medium (OM), were evaluated. The bioactive 55S41C4P-1300, containing pseudowollastonite, wollastonite, tricalcium phosphate and crystoballite as crystalline phases, was obtained by heat treatment of a sol-gel glass (55SiO(2), 41CaO, 4P(2)O(5) (mol.%)) at 1300 degrees C. The results showed that the MSCs adhered, spread, proliferated and produced mineralized extracellular matrix on 55S41C4P-1300 regardless of the culture medium used. As the same time, they showed an osteoblastic phenotype, and this phenomenon was accompanied by the gradual diminution of the marker CD90 expression. The 55S41C4P-1300 was able to induce the differentiation of MSCs into OBs in the same way as OM without glass ceramic. This effect increased with the combination of 55S41C4P-1300 with OM. The glass ceramic evaluated in this work is bioactive, cytocompatible and capable of promoting the differentiation of MSCs into OBs. For that reason, it could be regarded as a suitable matrix in tissue engineering for bone tissue regeneration.

Distraction osteogenesis of the lower extremity in patients with achondroplasia/hypochondroplasia treated with transplantation of culture-expanded bone marrow cells and platelet-rich plasma

BACKGROUND

Longer treatment period in distraction osteogenesis (DO) of the lower extremity leads to more frequent complications. We have developed a new technique of transplantation of culture-expanded bone marrow cells (BMCs) and platelet-rich plasma (PRP) during DO to accelerate new bone formation. To assess the efficacy of this cell therapy, retrospective comparative study was conducted between the bones treated with BMC and PRP and the bones treated without BMC and PRP during DO in patients with achondroplasia (ACH) and hypochondroplasia (HCH).

METHODS

Fifty-six bones in 20 patients (ACH, 16; HCH, 4) that were lengthened in our hospital were divided into 2 groups. Twenty-four bones (femora, 12; tibiae, 12) in 11 patients (boys, 7; girls, 4) were treated with BMC and PRP transplantation (BMC-PRP group), whereas 32 bones (femora, 14; tibiae, 18) in 9 patients (boys, 3; girls, 6) did not undergo additional cell therapy (control group). The parameters, including the age at operation, the increase in length, and the healing index, were compared between the 2 groups. The clinical outcome was also compared between the femoral and tibial lengthenings.

RESULTS

Bone marrow cells (average number, +/- SD, 3.2 +/- 1.37 x 10 cells) and PRP (average platelet concentration +/- SD, 2.36 +/- 0.57 x 10 cells/muL) were transplanted. Although there were no significant differences in the age at operation and the length gained between the 2 groups, the average healing index of the BMC-PRP group (27.1 +/- 6.89 d/cm) was significantly lower than that of the control group (36.2 +/- 10.4 d/cm) (P = 0.0005). The femoral lengthening showed significantly faster healing than did the tibial lengthening in the BMC-PRP group (P = 0.0092).

CONCLUSIONS

Transplantation of BMC and PRP shortened the treatment period by accelerating new bone regeneration during DO of the lower extremity in patients with ACH and HCH, especially in the femoral lengthening.

Hydrogel effects on bone marrow stromal cell response to chondrogenic growth factors

The aim of this study was to investigate the effects of alginate and agarose on the response of bone marrow stromal cells (BMSCs) to chondrogenic stimuli. Rat BMSCs were expanded in monolayer culture with or without FGF-2 supplementation. Cells were then seeded in 2% alginate and agarose gels and cultured in media with or without TGF-beta1 or dexamethasone (Dex). Sulfated glycosaminoglycans (sGAGs), collagen type II, and aggrecan were expressed in all groups that received TGF-beta1 treatment during hydrogel culture. Expansion of rat BMSCs in the presence of FGF-2 increased production of sGAG in TGF-beta1-treated groups over those cultures that were treated with TGF-beta1 alone in alginate cultures. However, in agarose, cells exposed to FGF-2 during expansion produced less sGAG within TGF-beta1-supplemented groups over those cultures treated with TGF-beta1 alone. Dex was required for optimal matrix synthesis in both hydrogels, but was found to decrease cell viability in agarose constructs. These results indicate that the response of BMSCs to a chondrogenic growth factor regimen is scaffold dependent.

In vitro osteogenesis from human skin-derived precursor cells

Embryonic tissue and organ development are initiated from three embryonic germ layers: ectoderm (skin and neuron), mesoderm (blood, bone, muscle, cartilage and fat) and endoderm (respiratory and digestive tract). In former times, it was believed that cell types in each germ layer are specific and do not cross from one to another throughout life. A new finding is that one tissue lineage can differentiate across to another tissue lineage, and this is termed transdifferentiation. We were interested in studying the transdifferentiation of skin-derived precursor cells (ectoderm layer) to osteoblastic cells (mesoderm layer). Human skin-derived precursor cells (hSKP) were isolated and induced into an osteoblastic lineage using osteogenic induction medium (alpha-MEM plus 10% fetal bovine serum supplemented with ascorbic acid, beta-glycerophosphate and dexamethasone). The specific characteristics of osteoblastic cells, including the expression of enzyme alkaline phosphatase, the deposition of mineral and the expression of osterix, bone sialoprotein and osteocalcin, were detected only from the inductive group. The results in our study show that SKP from human skin are a practically available source for osteogenesis. The samples are easily obtainable for autologous use with a high expansion capacity.

Human hemarthrosis-derived progenitor cells can differentiate into osteoblast-like cells in vitro

We hypothesized that intraarticular osteochondral fracture-induced hemarthrosis could be a useful cell source for bone regeneration, as it is thought to contain osteoprogenitor cells derived from bone marrow. Therefore, we investigated whether human hemarthrosis-derived cells have the potential to differentiate into osteoblast-like cells in vitro. We aspirated hemarthrosis from patients suffering from osteochondral fractures of knee joints, and cultured hemarthrosis-derived cells in a medium supplemented with dexamethasone, beta-glycerophosphate, and ascorbic acid, or without them as control. The morphology of the treated cells appeared to be cuboidal shape, differing from spindle-like shape observed in the control. Matrix mineralization was observed only in the treated culture. Alkaline phosphatase activity and gene expression of alkaline phosphatase, parathyroid hormone receptor, osteopontin, and osteocalcin were up-regulated compared with the control. These studies demonstrate that human hemarthrosis-derived cells can differentiate into osteoblast-like cells, i.e., they contain osteoprogenitor cells and are a useful cell source for bone regeneration.

The promyelotic leukemia zinc finger promotes osteoblastic differentiation of human mesenchymal stem cells as an upstream regulator of CBFA1

Ossification of the posterior longitudinal ligament of the spine (OPLL) is the leading cause of myelopathy in Japan and is diagnosed by ectopic bone formation in the paravertebral ligament. OPLL is a systemic high bone mass disease with a strong genetic background. To detect genes relevant to the pathogenesis of OPLL, we performed a cDNA microarray analysis of systematic gene expression profiles during the osteoblastic differentiation of ligament cells from OPLL patients (OPLL cells), patients with a disorder called ossification of yellow ligament (OYL), and non-OPLL controls together with human mesenchymal stem cells (hMSCs) after stimulating them with osteogenic differentiation medium (OS). Twenty-four genes were up-regulated during osteoblastic differentiation in OPLL cells. Zinc finger protein 145 (promyelotic leukemia zinc finger or PLZF) was one of the highly expressed genes during osteoblastic differentiation in all the cells examined. We investigated the roles of PLZF in the regulation of osteoblastic differentiation of hMSCs and C2C12 cells. Small interfering RNA-mediated gene silencing of PLZF resulted in a reduction in the expression of osteoblast-specific genes such as the alkaline phosphatase, collagen 1A1 (Col1a1), Runx2/core-binding factor 1 (Cbfa1), and osteocalcin genes, even in the presence of OS in hMSCs. The expression of PLZF was unaffected by the addition of bone morphogenetic protein 2 (BMP-2), and the expression of BMP-2 was not affected by PLZF in hMSCs. In C2C12 cells, overexpression of PLZF increased the expression of Cbfa1 and Col1a1; on the other hand, the overexpression of CBFA1 did not affect the expression of Plzf. These findings indicate that PLZF plays important roles in early osteoblastic differentiation as an upstream regulator of CBFA1 and thereby might participate in promoting the ossification of spinal ligament cells in OPLL patients.

Sclerostin promotes the apoptosis of human osteoblastic cells: a novel regulation of bone formation

A null mutation in the SOST gene is associated with sclerosteosis, an inherited disorder characterized by a high bone mass phenotype. The protein product of the SOST gene, sclerostin, is a bone morphogenetic protein (BMP) antagonist that decreases osteoblast activity and reduces the differentiation of osteoprogenitors. We sought to delineate the mechanism by which sclerostin modulated osteoblastic function by examining the effects of the protein on differentiating cultures of human mesenchymal stem cells (hMSC). Sclerostin significantly decreased alkaline phosphatase (ALP) activity and the proliferation of hMSC cells. In addition, hMSC cells treated with sclerostin displayed a marked increase in caspase activity. Elevated levels of fragmented histone-associated DNA in these cells were detected by ELISA and by TUNEL staining. Other BMP antagonists including noggin, Chordin, Gremlin, and Twisted gastrulation did not affect caspase activity. The sclerostin-mediated increase in caspase activity was blocked by caspase-1 and caspase-3 inhibitors. Sclerostin-induced changes in ALP activity and the survival of hMSC cells were partially restored by BMP-6, suggesting the involvement of additional growth factors. These findings show that sclerostin selectively controls the apoptosis of bone cells. The ability of sclerostin to interact with important growth factors such as BMPs likely serves as the basis by which it modulates the survival of osteoblasts. By making these growth factors unavailable for cell function, sclerostin promotes the apoptosis of bone cells, providing a novel level of control in the regulation of bone formation.

In vitro growth and osteoblastic differentiation of human bone marrow stromal cells supported by autologous plasma

Autologous bone marrow stromal cells have been proposed as an adjuvant in the treatment of bone nonunion. This cell therapy requires the establishment of culture conditions that permit the rapid expansion of these cells ex vivo while retaining their potential for further differentiation. Several culture models have been proposed, all of them using fetal calf serum (FCS) as a source of growth factors. This is problematic for subsequent autologous implantation because of possible disease transmission. Here we report the establishment and characterization of a cell culture system in which standard FCS has been replaced by autologous plasma recovered from bone marrow (APM). Short-term cultures of human bone marrow stromal (HBMS) cells grown in mineralizing conditions with APM exhibited a significantly higher number of ALP-positive colonies than those grown with FCS, indicating an enhanced ability of APM to recruit osteoprogenitor cells for culture. Analyses of long-term cultures showed that the use of APM did not affect cell proliferation as cell number at confluence and proliferation rate were similar whether primary cultures had been maintained with APM or FCS. In first-passage cultures, an osteoblastic differentiation was observed in both cases as the cells expressed ALP and formed mineralized bone-like nodules. We noted that the age of donor had a negative effect on the number of osteoprogenitor cells recruited for culture. This effect had an impact on proliferation rate in primary cultures performed with APM, although the cell number obtained after expansion remained independent of age. Our study shows that proliferative capacity and osteoblastic differentiation potential of HBMS cells are maintained when cultured with APM. Thus, this cell culture system could provide a new and safer tool to elaborate an autologous cell therapy designed to enhance osteogenesis.

Unique regulation of SOST, the sclerosteosis gene, by BMPs and steroid hormones in human osteoblasts

SOST, a novel bone morphogenetic protein (BMP) antagonist and negative regulator of bone formation, is expressed in osteogenic cells. Null mutations in the SOST gene are associated with the sclerosteosis phenotype typified by high bone mass. We sought to delineate the pathways involved in the regulation of SOST expression in human osteoblastic cells. We evaluated the effects of bone growth factors and hormones on the RNA levels of SOST and the BMP antagonists, noggin and gremlin. Parathyroid hormone (PTH), transforming growth factor-beta1 (TGF-beta1), fibroblast growth factors 1 and 2 (FGF1, FGF2), and insulin-like growth factor-1 (IGF-1) had negligible effects on SOST expression in human osteoblasts. In comparison, BMPs-2, 4, and 6 induced the message levels of SOST in a time- and dose-dependent manner. The levels of noggin and, to a lesser extent, gremlin were also increased by BMPs. BMP's stimulatory effects on SOST were further enhanced by retinoic acid or 1,25-dihydroxyvitamin D3. In contrast, dexamethasone (DEX) blocked the effects of the BMPs on SOST and gremlin, but not on noggin. Retinoic acid and 1,25-dihydroxyvitamin D3 did not affect the BMP-enhanced expression of gremlin or noggin. The steroids did not affect the endogenous levels of the BMP antagonists. These findings show that the levels of SOST are modulated by BMPs and the interactions of the BMPs with steroid hormones in human osteoblasts. These effects differed markedly from that of noggin or gremlin, suggesting that there is an exquisite regulation of the expressions of BMP antagonists in cells of the osteoblast lineage.

Studies on bone marrow stromal cells affinity of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate)

The objective of this study is to investigate the biocompatibility of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) with bone marrow stromal cells in vitro. The adsorption of fibronectin on the material was studied by enzyme-linked immunosorbent assay. After bone marrow stromal cells were seeded and cultured on PHBHHx, their proliferation was investigated by MTT. Differentiation of the cells was assessed by measuring alkaline phosphatase activity and by histochemical assay. The wettability and thermal property of PHBHHx films were also studied by contact angle goniometer, thermogravimetry and differential scanning calorimetry, respectively. The results show that bone marrow stromal cells can attach, proliferate and differentiate into osteoblasts on PHBHHx films. These results suggest that PHBHHx has good affinity with bone marrow stromal cells and may have potential applications in bone tissue engineering.

Hydrocortisone increases the rate of differentiation of cultured human osteoblasts

Reduced bone formation is the main finding in glucocorticoid-induced osteoporosis. The aim of this study was to determine whether differentiation of cultured human osteoblasts is inhibited by high concentrations of hydrocortisone. We measured the levels of mRNAs for three markers of cellular differentiation, type 1 collagen (COL1), alkaline phosphatase (ALP), and osteocalcin (OC), in four lines of human osteoblasts from female donors cultured with doses of hydrocortisone from 0 microM to 4 microM. The change in ALP/COL1 mRNA ratio over a given time was used to determine the average rate of differentiation of the cells in a culture. Although basal expression profiles and their changes with time were different for the different cell lines, all cell lines showed a dose-dependent rise in the rate of increase of ALP mRNA relative to COL1 mRNA. However, increase in OC mRNA with time, seen here only in young donor hOBs, was significantly inhibited by 4 microM hydrocortisone, indicating that hydrocortisone can inhibit OC expression while promoting cellular differentiation. The data suggest that increasing concentrations of glucocorticoid, including concentrations similar to plasma levels in patients receiving oral glucocorticoid therapy, increase the rate of cellular differentiation.