Effects of BMP-2 and vitamin D3 on the osteogenic differentiation of adipose stem cells

Engineered 3D liver-tissue model with minispheroids formed by a bioprinting process supported with in situ electrical stimulation

Three-dimensional (3D) bioprinting, an effective technique for building cell-laden structures providing native extracellular matrix environments, presents challenges, including inadequate cellular interactions. To address these issues, cell spheroids offer a promising solution for improving their biological functions. Particularly, minispheroids with 50-100 μm diameters exhibit enhanced cellular maturation. We propose a one-step minispheroid-forming bioprinting process incorporating electrical stimulation (E-MS-printing). By stimulating the cells, minispheroids with controlled diameters were generated by manipulating the bioink viscosity and stimulation intensity. To validate its feasibility, E-MS-printing process was applied to fabricate an engineered liver model designed to mimic the hepatic lobule unit. E-MS-printing was employed to print the hepatocyte region, followed by bioprinting the central vein using a core-shell nozzle. The resulting constructs displayed native liver-mimetic structures containing minispheroids, which facilitated improved hepatic cell maturation, functional attributes, and vessel formation. Our results demonstrate a new potential 3D liver model that can replicate native liver tissues.

Osteogenic Differentiation of Human Adipose-Derived Stem Cells Seeded on a Biomimetic Spongiosa-like Scaffold: Bone Morphogenetic Protein-2 Delivery by Overexpressing Fascia

Human adipose-derived stem cells (hADSCs) have the capacity for osteogenic differentiation and, in combination with suitable biomaterials and growth factors, the regeneration of bone defects. In order to differentiate hADSCs into the osteogenic lineage, bone morphogenetic proteins (BMPs) have been proven to be highly effective, especially when expressed locally by route of gene transfer, providing a constant stimulus over an extended period of time. However, the creation of genetically modified hADSCs is laborious and time-consuming, which hinders clinical translation of the approach. Instead, expedited single-surgery gene therapy strategies must be developed. Therefore, in an in vitro experiment, we evaluated a novel growth factor delivery system, comprising adenoviral BMP-2 transduced fascia tissue in terms of BMP-2 release kinetics and osteogenic effects, on hADSCs seeded on an innovative biomimetic spongiosa-like scaffold. As compared to direct BMP-2 transduction of hADSCs or addition of recombinant BMP-2, overexpressing fascia provided a more uniform, constant level of BMP-2 over 30 days. Despite considerably higher BMP-2 peak levels in the comparison groups, delivery by overexpressing fascia led to a strong osteogenic response of hADSCs. The use of BMP-2 transduced fascia in combination with hADSCs may evolve into an expedited single-surgery gene transfer approach to bone repair.

In Vitro Prevascularization of Self-Assembled Human Bone-Like Tissues and Preclinical Assessment Using a Rat Calvarial Bone Defect Model

In vitro prevascularization has the potential to address the challenge of maintaining cell viability at the core of engineered constructs, such as bone substitutes, and to improve the survival of tissue grafts by allowing quicker anastomosis to the host microvasculature. The self-assembly approach of tissue engineering allows the production of biomimetic bone-like tissue constructs including extracellular matrix and living human adipose-derived stromal/stem cells (hASCs) induced towards osteogenic differentiation. We hypothesized that the addition of endothelial cells could improve osteogenesis and biomineralization during the production of self-assembled human bone-like tissues using hASCs. Additionally, we postulated that these prevascularized constructs would consequently improve graft survival and bone repair of rat calvarial bone defects. This study shows that a dense capillary network spontaneously formed in vitro during tissue biofabrication after two weeks of maturation. Despite reductions in osteocalcin levels and hydroxyapatite formation in vitro in prevascularized bone-like tissues (35 days of culture), in vivo imaging of prevascularized constructs showed an improvement in cell survival without impeding bone healing after 12 weeks of implantation in a calvarial bone defect model (immunocompromised male rats), compared to their stromal counterparts. Globally, these findings establish our ability to engineer prevascularized bone-like tissues with improved functional properties.

Effects of exogenous nerve growth factor on the expression of BMP-9 and VEGF in the healing of rabbit mandible fracture with local nerve injury

BACKGROUND

Mandibular fracture healing is a complex process involving nerves and growth factors. Nerve growth factor (NGF) not only facilitates the maintenance of sympathetic neurite growth but also stimulates other growth factors that can promote the essential osteogenesis and angiogenesis for fracture healing. Therefore, it is necessary to analyze the combined effects of NGF, bone morphogenic protein-9 (BMP-9), and vascular endothelial growth factor (VEGF) to accelerate the healing of mandible fractures.

METHODS

The models of mandible fracture with local nerve injury established in 48 rabbits were randomly divided into nerve growth factor group (NGF group), gelatin sponge group (GS group), blank group, and intact group. The recovery of nerve reflex was assessed by observing the number of rabbits with lower lip responses to acupuncture. The fracture healing was observed with visual and CBCT, and then callus tissues from the mandibular fracture area were collected for hematoxylin and eosin (HE) staining observation, and the expression of BMP-9 and VEGF in callus at different stages was detected by quantitative real-time PCR (qRT-PCR).

RESULTS

Needling reaction in the lower lip showed the number of animals with nerve reflex recovery was significantly higher in the NGF group than that in the GS and blank groups at the 2nd and 4th weeks after the operation. The combined results of macroscopic observation, CBCT examination, and histological analysis showed that a large number of osteoblasts and some vascular endothelial cells were found around the trabecular bone in the NGF group and the amount of callus formation and reconstruction was better than that in the GS group at the 2nd week after the operation. The qRT-PCR results indicated that the expression levels of BMP-9 and VEGF in the four groups reached the highest values at the 2nd week, while the expression levels of both in the NGF group were significantly higher than that in the GS group.

CONCLUSION

The exogenous NGF could accelerate the healing of mandible fractures. This work will provide a new foundation and theoretical basis for clarifying the mechanism of fracture healing, thereby promoting fracture healing and reducing the disability rate of patients.

Pleiotropic actions of Vitamin D in composite musculoskeletal trauma

Composite tissue injuries are the result of high energy impacts caused by motor vehicle accidents, gunshot wounds or blasts. These are highly traumatic injuries characterized by wide-spread, penetrating wounds affecting the entire musculoskeletal system, and are generally defined by frank volumetric muscle loss with concomitant segmental bone defects. At the tissue level, the breadth of damage to multiple tissue systems, and potential for infection from penetration, have been shown to lead to an exaggerated, often chronic inflammatory response with subsequent dysregulation of normal musculoskeletal healing mechanisms. Aside from the direct effects of inflammation on myogenesis and osteogenesis, frank muscle loss has been shown to directly impair fracture union and ultimately contribute to failed wound regeneration. Care for these injuries requires extensive surgical intervention and acute care strategies. However, often these interventions do not adequately mitigate inflammation or promote proper musculoskeletal injury repair and force amputation of the limb. Therefore, identification of factors that can promote tissue regeneration and mitigate inflammation could be key to restoring wound healing after composite tissue injury. One such factor that may directly affect both inflammation and tissue regeneration in response to these multi-tissue injuries may be Vitamin D. Beyond traditional roles, the pleiotropic and localized actions of Vitamin D are increasingly being recognized in most aspects of wound healing in complex tissue injuries - e.g., regulation of inflammation, myogenesis, fracture callus mineralization and remodeling. Conversely, pre-existing Vitamin D deficiency leads to musculoskeletal dysfunction, increased fracture risk or fracture non-unions, decreased strength/function and reduced capacity to heal wounds through increased inflammation. This Vitamin D deficient state requires acute supplementation in order to quickly restore circulating levels to an optimal level, thereby facilitating a robust wound healing response. Herein, the purpose of this review is to address the roles and critical functions of Vitamin D throughout the wound healing process. Findings from this review suggest that careful monitoring and/or supplementation of Vitamin D may be critical for wound regeneration in composite tissue injuries.

Burst, Short, and Sustained Vitamin D3 Applications Differentially Affect Osteogenic Differentiation of Human Adipose Stem Cells

Incorporation of 1,25(OH)₂ vitamin D₃ (vitD₃) into tissue-engineered scaffolds could aid the healing of critical-sized bone defects. We hypothesize that shorter applications of vitD₃ lead to more osteogenic differentiation of mesenchymal stem cells (MSCs) than a sustained application. To test this, release from a scaffold was mimicked by exposing MSCs to exactly controlled vitD₃ regimens. Human adipose stem cells (hASCs) were seeded onto calcium phosphate particles, cultured for 20 days, and treated with 124 ng vitD₃, either provided during 30 min before seeding ([200 nM]), during the first two days ([100 nM]), or during 20 days ([10 nM]). Alternatively, hASCs were treated for two days with 6.2 ng vitD₃ ([10 nM]). hASCs attached to the calcium phosphate particles and were viable (~75%). Cell number was not affected by the various vitD₃ applications. VitD₃ (124 ng) applied over 20 days increased cellular alkaline phosphatase activity at Days 7 and 20, reduced expression of the early osteogenic marker RUNX2 at Day 20, and strongly upregulated expression of the vitD₃ inactivating enzyme CYP24. VitD₃ (124 ng) also reduced RUNX2 and increased CYP24 applied at [100 nM] for two days, but not at [200 nM] for 30 min. These results show that 20-day application of vitD₃ has more effect on hASCs than the same total amount applied in a shorter time span.

The Role of Vitamin D in Modulating Mesenchymal Stem Cells and Endothelial Progenitor Cells for Vascular Calcification

Vascular calcification, which involves the deposition of calcifying particles within the arterial wall, is mediated by atherosclerosis, vascular smooth muscle cell osteoblastic changes, adventitial mesenchymal stem cell osteoblastic differentiation, and insufficiency of the calcification inhibitors. Recent observations implied a role for mesenchymal stem cells and endothelial progenitor cells in vascular calcification. Mesenchymal stem cells reside in the bone marrow and the adventitial layer of arteries. Endothelial progenitor cells that originate from the bone marrow are an important mechanism for repairing injured endothelial cells. Mesenchymal stem cells may differentiate osteogenically by inflammation or by specific stimuli, which can activate calcification. However, the bioactive substances secreted from mesenchymal stem cells have been shown to mitigate vascular calcification by suppressing inflammation, bone morphogenetic protein 2, and the Wingless-INT signal. Vitamin D deficiency may contribute to vascular calcification. Vitamin D supplement has been used to modulate the osteoblastic differentiation of mesenchymal stem cells and to lessen vascular injury by stimulating adhesion and migration of endothelial progenitor cells. This narrative review clarifies the role of mesenchymal stem cells and the possible role of vitamin D in the mechanisms of vascular calcification.

Is Osteogenic Differentiation of Human Nucleus Pulposus Cells a Possibility for Biological Spinal Fusion?

OBJECTIVE

The purpose of this study was to investigate whether a simple, biologically robust method for inducing calcification of degenerate intervertebral discs (IVD) could be developed to provide an alternative treatment for patients requiring spinal fusion.

DESIGN

Nucleus pulposus (NP) cells isolated from 14 human IVDs were cultured in monolayer and exposed to osteogenic medium, 1,25-dihydroxyvitamin D₃ (VitD₃), parathyroid hormone (PTH), and bone morphogenic proteins (BMPs) 2/7 to determine if they could become osteogenic. Similarly explant cultures of IVDs from 11 patients were cultured in osteogenic media with and without prior exposure to VitD₃ and BMP-2. Osteogenic differentiation was assessed by alkaline phosphatase activity and areas of calcification identified by alizarin red or von Kossa staining. Expression of osteogenic genes during monolayer culture was determined using polymerase chain reaction and explant tissues assessed for BMP inhibitors. Human bone marrow-derived mesenchymal stromal cells (MSCs) were used for comparison.

RESULTS

Standard osteogenic media was optimum for promoting mineralization by human NP cells in monolayer. Some osteogenic differentiation was observed with 10 nM VitD₃, but none following application of PTH or BMPs. Regions of calcification were detected in 2 of the eleven IVD tissue explants, one cultured in osteogenic media and one with the addition of VitD₃ and BMP-2.

CONCLUSIONS

Human NP cells can become osteogenic in monolayer and calcification of the extracellular matrix can also occur, although not consistently. Inhibitory factors within either the cells or the extracellular matrix may hinder osteogenesis, indicating that a robust biological fusion at this time requires further optimization.

Osteogenic Differentiation of Adipose-Derived Stromal Cells: From Bench to Clinics

In addition to mesenchymal stem cells, adipose-derived stem/stromal cells (ASCs) are an attractive source for a large variety of cell-based therapies. One of their most important potential applications is related to the regeneration of bone tissue thanks to their capacity to differentiate in bone cells. However, this requires a proper control of their osteogenic differentiation, which depends not only on the initial characteristics of harvested cells but also on the conditions used for their culture. In this review, we first briefly describe the preclinical and clinical trials using ASCs for bone regeneration and present the quantitative parameters used to characterize the osteogenic differentiation of ASCs. We then focus on the soluble factors influencing the osteogenic differentiation of ACS, including the steroid hormones and various growth factors, notably the most osteoinductive ones, the bone morphogenetic proteins (BMPs). Impact statement Adipose-derived stromal/stem cells are reviewed for their use in bone regeneration.

Triiodothyronine Has No Enhancement Effect on the Osteogenic or Chondrogenic Differentiation of Equine Adipose Tissue Stem Cells

The effects of two concentrations of triiodothyronine (T3; 0.01 and 1,000 nM) on the osteogenic and chondrogenic differentiation abilities of equine adipose-derived mesenchymal stem cells (AD-MSCs) were evaluated. The osteogenic study evaluated the effect of T3 using alkaline phosphatase activity (ALP) assay; cell viability and density; and formation of mineralized nodules at Days 7, 14, and 21 in culture. The chondrogenic study tested the effect of T3 through ALP assay, mitochondrial metabolism, cell density, and periodic acid-Schiff-positive (PAS+) matrix percentage at Days 7 and 14. In both experiments, analysis of variance was used to compare averages through the Student-Newman-Keuls test. In the osteogenic study, no differences in any variable were detected between groups at Day 7. At Day 14, 0.01 nM T3 reduced cell density and the number of mineralized nodules despite the increase in ALP activity and mitochondrial metabolism (P < .05). ALP activity increased at 1,000 nM T3 concentration (P < .05). At Day 21, 0.01 nM T3 treatment increased ALP activity compared with control treatment (P < .05). At 1,000 nM concentration, T3 reduced mitochondrial metabolism and cell density (P < .05). In the chondrogenic study, the two T3 concentrations increased cell density compared with control treatment at Day 7. At Day 14, higher T3 concentration reduced mitochondrial metabolism, ALP activity, cell density, and PAS+ chondrogenic matrix percentage compared with control treatment (P < .05). Thus, T3 addition to equine AD-MSC cultures has no enhancement effect on osteogenic or chondrogenic differentiation and may, in fact, negatively affect cell density and matrix synthesis depending on hormone concentration and culture time.

Short Pretreatment with Calcitriol Is Far Superior to Continuous Treatment in Stimulating Proliferation and Osteogenic Differentiation of Human Adipose Stem Cells

Objective

This study investigated whether short stimulation (30 minutes) of human adipose stem cells (hASCs) with 1,25-dihydroxyvitamin D₃ (calcitriol or 1,25-(OH)₂VitD₃), fitting within the surgical procedure time frame, suffices to induce osteogenic differentiation, and compared this with continuous treatment with 1,25-(OH)₂VitD₃.

Materials and Methods

In this experimental study, hASCs were pretreated with/without 10 nM calcitriol for 30 minutes, seeded on biphasic calcium phosphate (BCP), and cultured for 3 weeks with/without 1,25-(OH)₂VitD₃. Cell attachment was determined 30 minutes after cell seeding. AlamarBlue assay, alkaline phosphatase (ALP) assay, ALP staining, real-time polymerase chain reaction (PCR), and protein assay were used to evaluate the effect of short calcitriol pretreatment on proliferation and osteogenic differentiation of hASCs up to 3 weeks.

Results

Pretreatment with 1,25-(OH)₂VitD₃ enhanced the attachment of hASCs to BCP by 1.5-fold compared to nontreated cells and increased the proliferation by 3.5-fold at day 14, and 2.6-fold at day 21. In contrast, continuous treatment increased the proliferation by 1.7-fold only at day 14. After 2 weeks, ALP activity was increased by 18.5-fold when hASCs were pretreated with 1,25-(OH)₂VitD₃ for 30 minutes but increased only 2.6-fold when compared with its continuous counterpart. Moreover, after 14 days, pretreatment resulted in significant upregulation of the osteogenic markers RUNX2 and SPARC by 3.6-fold and 2.2-fold, respectively, while this was not observed upon continuous treatment. Finally, 30 minutes pretreatment of hASCs with 1,25-(OH)₂VitD₃ increased VEGF₁₈₉ expression, which may contribute to the process of angiogenesis.

Conclusion

This study is the first research showing that 30 minutes pretreatment of hASCs with 1,25-(OH)₂VitD₃, not only enhanced cell attachment to the scaffold at seeding time, but also promoted the proliferation and osteogenic differentiation of hASCs more strongly than continuous treatment, suggesting that short pre-treatment with 1,25-(OH)₂VitD₃ is a promising approach for the regeneration of bones in a one-step surgical procedure.

Vitamin D-conjugated gold nanoparticles as functional carriers to enhancing osteogenic differentiation

In an aging society, bone disorders such as osteopenia, osteoporosis, and degenerative arthritis cause serious public health problems. In order to solve these problems, researchers continue to develop therapeutic agents, increase the efficacy of developed therapeutic agents, and reduce side effects. Gold nanoparticles (GNPs) are widely used in tissue engineering applications as biosensors, drug delivery carriers, and bioactive materials. Their special surface property enables easy conjugation with ligands including functional groups such as thiols, phosphines, and amines. This creates an attractive advantage to GNPs for use in the bone tissue engineering field. However, GNPs alone are limited in their biological effects. In this study, we used thiol-PEG-vitamin D (SPVD) to conjugate vitamin D, an essential nutrient critical for maintaining normal skeletal homeostasis, to GNPs. To characterize vitamin D-conjugated GNPs (VGNPs), field emission transmission electron microscopy, energy dispersive X-ray spectroscopy, dynamic light scattering, and ultraviolet/visible absorption analysis were carried out. The developed VGNPs were well bound through the thiol groups between GNPs and vitamin D, and were fabricated in size of 60 nm. Moreover, to demonstrate VGNPs osteogenic differentiation effect, various assays were carried out through cell viability test, alkaline phosphatase assay, calcium deposition assay, real-time polymerase chain reaction, and immunofluorescence staining. As a result, the fabricated VGNPs were found to effectively enhance osteogenic differentiation of human adipose-derived stem cells (hADSCs) in vitro. Based on these results, VGNPs can be utilized as functional nanomaterials for bone regeneration in the tissue engineering field.

Revisiting the Advances in Isolation, Characterization and Secretome of Adipose-Derived Stromal/Stem Cells

Adipose-derived stromal/stem cells (ASCs) seems to be a promising regenerative therapeutic agent due to the minimally invasive approach of their harvest and multi-lineage differentiation potential. The harvested adipose tissues are further digested to extract stromal vascular fraction (SVF), which is cultured, and the anchorage-dependent cells are isolated in order to characterize their stemness, surface markers, and multi-differentiation potential. The differentiation potential of ASCs is directed through manipulating culture medium composition with an introduction of growth factors to obtain the desired cell type. ASCs have been widely studied for its regenerative therapeutic solution to neurologic, skin, wound, muscle, bone, and other disorders. These therapeutic outcomes of ASCs are achieved possibly via autocrine and paracrine effects of their secretome comprising of cytokines, extracellular proteins and RNAs. Therefore, secretome-derivatives might offer huge advantages over cells through their synthesis and storage for long-term use. When considering the therapeutic significance and future prospects of ASCs, this review summarizes the recent developments made in harvesting, isolation, and characterization. Furthermore, this article also provides a deeper insight into secretome of ASCs mediating regenerative efficacy.

Adipose-derived and bone marrow mesenchymal stem cells: a donor-matched comparison

Background

Adipose-derived stem cells (ASCs) have been introduced as an alternative to bone marrow mesenchymal stem cells (BMSCs) for cell-based therapy. However, different studies comparing ASCs and BMSCs have shown conflicting results. In fact, harvesting ASCs and BMSCs from different individuals might influence the results, making comparison difficult. Therefore, this study aimed to characterize donor-matched ASCs and BMSCs in order to investigate proliferation, differentiation potential and possible effects of donor variation on these mesenchymal stem cells (MSCs).

Methods

Human bone marrow and adipose tissue samples were obtained from nine donors aged 8–14. ASCs and BMSCs were isolated and characterized based on expression of surface markers using flow cytometry. The proliferation up to 21 days was investigated. Multi-lineage differentiation was induced using osteogenic, chondrogenic and adipogenic differentiation media. Alkaline phosphatase (ALP) activity was monitored and collagen type I formation was evaluated by immunofluorescence staining. In vitro multi-potency was studied using tissue-specific stains and lineage-specific gene expression. In addition, the osteogenic lineage was evaluated at protein level.

Results

Isolated ASCs and BMSCs from all donors demonstrated morphologic and immunophenotypic characteristics of MSCs, with expression of MSCs markers and negative expression of hematopoietic markers. Unlike BMSCs, ASCs showed high expression of CD49d and low expression of Stro-1. In general, ASCs showed significantly higher proliferation and adipogenic capacity with more lipid vesicle formation and expression of the adipogenesis-related genes than BMSCs. In contrast, BMSCs showed significantly higher osteogenic and chondrogenic capacity compared to ASCs. BMSCs had earlier and higher ALP activity, calcium deposition, and expression of the osteogenesis- and chondrogenesis-related genes and the osteogenesis-related protein osteopontin. Proliferation and differentiation capacity of ASCs and BMSCs varied significantly among the donors.

Conclusions

ASCs and BMSCs showed tissue-specific differentiation abilities, but with significant variation between donors. The similarities and differences in the properties of ASCs and BMSCs should be taken into consideration when planning stem cell-based therapy.

Isolation, culture and induced differentiation of rabbit mesenchymal stem cells into osteoblasts

Mesenchymal stem cells (MSCs) may be easily isolated from the bone marrow, and possess multi-lineage differentiation potential and various therapeutic applications. The differentiation of MSCs into osteoblasts is a complex process that is regulated by multiple internal and external factors. In the present study, the differentiation of MSCs isolated from rabbit bone marrow into osteoblasts using different osteoblast inductive media in the presence of dexamethasone, bone morphogenetic protein 2 (BMP-2), 1,25-dihydroxyvitamin D3, transforming growth factor β (TGFβ), platelet lysate and cyclooxygenase 2 (COX2), respectively. Alkaline phosphatase (ALP) activity, mineralization, collagen type (Ct) I and osteocalcin activities, and the mRNA and protein expression levels of vascular endothelial growth factor (VEGF), BMP-2 and Ct II were measured during the differentiation process in MSCs treated with different inducers. Rabbit MSCs were successfully isolated and were observed to be predominantly circular in shape after culture for 24 h. Following subculture for 5 days, the cells demonstrated a spindle shape. ALP, Ct I and osteocalcin activities were higher in cells cultured in dexamethasone, BMP-2 and TGFβ compared with the activities in control cells. Following differentiation, the dexamethasone, BMP-2 and TGFβ groups demonstrated significantly enhanced mineralization of MSCs detected by Alizarin Red S staining. The mRNA and protein expression levels of VEGF, BMP-2 and Ct II were significantly increased in the same groups compared with the levels in the control group. In conclusion, rabbit MSCs were successfully isolated from bone marrow and differentiated into osteoblasts indicated by raised ALP, Ct I and osteocalcin activities, mineralization and expression of osteogenesis-inducing genes and proteins. The present study revealed that dexamethasone, BMP-2 and TGFβ have a positive effect on cell differentiation.

MicroRNA profiles of BMSCs induced into osteoblasts with osteoinductive medium

MicroRNA (miRNA) plays an important role in cell differentiation and functions as a regulator. Therefore, miRNA is important in the process of bone marrow mesenchymal stem cells (BMSCs) being induced into osteoblasts. In this study, mouse BMSCs were induced with osteoinductive medium, the indices related to osteoblastic differentiation were assayed, including alkaline phosphatase, the deposit of calcium and protein levels of osteocalcin. Using miRNA microarray and reverse transcription-quantitative polymerase chain reaction analyses, differentially expressed miRNAs in the cells, which were induced with osteoinductive medium, were selected and identified. The target genes of the differentially expressed miRNAs were then predicted using bioinformatics analysis. The results revealed that osteoinductive medium promoted osteoblastic differentiation of BMSCs, and let-7c-5p, miR-181c-3p, miR-3092-3p and miR-5132-3p were identified as differentially expressed miRNAs in the cells treated with osteoinductive medium for 14 and 21 days. Certain target genes and signal pathways related to osteoblastic differentiation of the four miRNAs were predicted. These findings indicated the four differently expressed miRNAs may be potential regulators of osteoblastic differentiation, providing a basis for further study on the regulation of miRNAs in the osteogenic differentiation of BMSCs.

Bone Tissue Engineering Strategies in Co-Delivery of Bone Morphogenetic Protein-2 and Biochemical Signaling Factors

Administration of bone morphogenetic protein-2 (BMP-2), which is commercially approved by the food and drug administration to damaged bone sites has been investigated for the purpose of bone tissue regeneration. BMP-2 can promote osteoblastic differentiation of mesenchymal stem cells as well as regeneration of bone formation in early phase. This review highlights various factors such as vitamin D, dexamethasone, platelet-derived growth factor, placental growth factor, BMP-7, and NEL-like protein-1 that enhance and stimulate angiogenesis, cell differentiation, and bone regeneration. These biochemical signals and growth factors (GFs) accelerate bone repair and remodeling either synergistically or individually. Delivery systems and scaffolds are used for sustained release of these cargo molecules and support at damaged bone sites. Compared with direct administration of BMP-2, current studies have demonstrated that a combination of multiple GFs and/or therapeutic chemical factors with delivery platforms synergistically facilitates bone regeneration. Therefore, in the future, multiple combinations of various GFs, chemicals, and materials could provide patients and surgeons with non-invasive treatment options without secondary surgery and pain. To the end, this review summarizes the biological functions and synergistic effects of dual administration modalities involving BMP-2 as well as recent developments in bone tissue engineering applications.

Ablation of the mammalian lectin galectin-8 induces bone defects in mice

Mice overexpressing galectin-8 [gal-8 transgenic (Tg)], a secreted mammalian lectin, exhibit enhanced bone turnover and reduced bone mass, similar to cases of postmenopausal osteoporosis. Here, we show that gal-8 knockout (KO) mice have increased bone mass accrual at a young age but exhibit accelerated bone loss during adulthood. These phenotypes can be attributed to a gal-8-mediated increase in receptor activator of NF-κB ligand (RANKL) expression that promotes osteoclastogenesis, combined with direct inhibition of osteoblast differentiation, evident by reduced bone morphogenetic protein (BMP) signaling, reduced phosphorylation of receptor regulated mothers against decapentaplegic homolog (R-SMAD) and reduced expression of osteoblast differentiation markers osterix, osteocalcin, runt-related transcription factor 2 (RUNX2), dentin matrix acidic phosphoprotein-1 (DMP1), and alkaline phosphatase. At the same time, gal-8 promotes expression of estrogen receptor α (ESR1). Accordingly, the rate of bone loss is accelerated in ovariectomized, estrogen-deficient gal-8 Tg mice, whereas gal-8 KO mice, having low levels of ESR1, are refractory to ovariectomy. Finally, gal-8 mRNA positively correlates with the mRNA levels of osteoclastogenic markers RANKL, tartrate-resistant acid phosphatase, and cathepsin K in human femurs. Collectively, these findings identify gal-8 as a new physiologic player in the regulation of bone mass.-Vinik, Y., Shatz-Azoulay, H., Hiram-Bab, S., Kandel, L., Gabet, Y., Rivkin, G., Zick, Y. Ablation of the mammalian lectin galectin-8 induces bone defects in mice.

WNT3A and the induction of the osteogenic differentiation in adipose tissue derived mesenchymal stem cells

Adipose tissue derived stem cells (ASCs) can easily be isolated, but the osteogenic differentiation potential is limited. To improve this differentiation potential, more investigations are required about signaling proteins for the induction of the osteogenic differentiation. This study focused on the WNT3A protein, because little is known about the canonical WNT signaling pathway and the osteogenic differentiation of ASCs. The alkaline phosphatase (ALP) activity was measured for the evaluation of the osteogenic differentiation. WNT3A and Dickkopf-related protein 1 (DKK1) were used for the activation and the inhibition of the canonical WNT signaling pathway, respectively. For control we manipulated the bone morphogenetic protein (BMP) pathway in ASCs with BMP2 and NOGGIN (BMP pathway inhibitor). WNT3A stimulated significantly the ALP activity in ASCs, while BMP2, DKK1 and NOGGIN did not induce highly the ALP activity in ASCs. Moreover, an osteogenic differentiation medium with dexamethasone and WNT3A increased the ALP activity, but the gene expression of osteoblast markers and the biomineralization after long-term cultures were not increased. In contrast, ASCs differentiated into adipocyte-like cells in all tested differentiation media. WNT3A did not repress the expression of the adipogenic transcription factor Peroxisome Proliferator-Activated Receptor Gamma (PPARG). In conclusion, WNT3A supports early stages such as the ALP activity, but it does neither improve later stages of the osteogenic differentiation nor it inhibits the genuine adipogenic differentiation of ASCs.

Melatonin and Vitamin D Interfere with the Adipogenic Fate of Adipose-Derived Stem Cells

Adipose-derived stem cells (ADSCs) represent one of the cellular populations resident in adipose tissue. They can be recruited under certain stimuli and committed to become preadipocytes, and then mature adipocytes. Controlling stem cell differentiation towards the adipogenic phenotype could have a great impact on future drug development aimed at counteracting fat depots. Stem cell commitment can be influenced by different molecules, such as melatonin, which we have previously shown to be an osteogenic inducer. Here, we aimed at evaluating the effects elicited by melatonin, even in the presence of vitamin D, on ADSC adipogenesis assessed in a specific medium. The transcription of specific adipogenesis orchestrating genes, such as aP2, peroxisome proliferator-activated receptor γ (PPAR-γ), and that of adipocyte-specific genes, including lipoprotein lipase (LPL) and acyl-CoA thioesterase 2 (ACOT2), was significantly inhibited in cells that had been treated in the presence of melatonin and vitamin D, alone or in combination. Protein content and lipid accumulation confirmed a reduction in adipogenesis in ADSCs that had been grown in adipogenic conditions, but in the presence of melatonin and/or vitamin D. Our findings indicate the role of melatonin and vitamin D in deciding stem cell fate, and disclose novel therapeutic approaches against fat depots.

Suppression of osteoblast-related genes during osteogenic differentiation of adipose tissue derived stromal cells

Recent studies indicated a lower osteogenic differentiation potential of adipose tissue-derived stromal cells (ASCs) compared to bone marrow derived mesenchymal stromal cells. The aim of this study was to evaluate the effects of potent combinations of highly osteogenic bone morphogenetic proteins (BMPs) in order to enhance the osteogenic differentiation potential of ASCs. Human ASCs were cultured for 10 days in the presence of osteogenic medium consisting of dexamethasone, ß-glycerophosphate and ascorbat-2-phosphate (OM) supplemented with BMP-2, BMP-6, BMP-9+IGF-2 and BMP-2,-6,-9 (day 1+2: 50 ng/ml, days 3-6: 100 ng/ml, days 7-10: 200 ng/ml). The formation of the osteoblast phenotype was evaluated by quantification of osteoblast-related marker genes using real-time polymerase chain reaction (RT-PCR). Matrix mineralization was assessed by Alizarin Red S staining. Statistical analysis was carried out using the one-way analysis of variance (ANOVA) followed by the Scheffe's post hoc procedure. Osteogenic medium (OM) significantly increased the expression of alkaline phosphatase (ALP) and osteocalcin (p < 0.05) and led to a stable matrix mineralization. Under the influence of BMP-9+IGF-2 and BMP-2,-6,-9 the ALP expression further increased compared to ASCs cultured with OM only (p < 0.01). However, multiple osteogenic markers showed no change or decreased under the influence of OM and BMP combinations (p < 0.05). The current results indicate a restricted osteogenic differentiation potential of ASCs and suggest careful reconsideration of their use in bone tissue engineering applications.

1,25 dihydroxyvitamin D3 inhibits the proliferation of thyroid cancer stem-like cells via cell cycle arrest

BACKGROUND

An anti-proliferative effect of vitamin D has been reported in different carcinomas, including thyroid cancer. Cancer stem cells (CSCs), a very small fraction of cancer cells, are widely believed to be responsible for cancer initiation, relapse and metastasis.

OBJECTIVES

We addressed the question as to whether CSCs derived from the anaplastic thyroid carcinoma cell lines SW1736, C643, HTh74 and its doxorubicin- resistant subline HTh74R are also a target of vitamin D action.

METHODS

The effect of calcitriol on growth of HTh74, HTh74R, SW1736 and C643 cell lines was investigated by cell viability assays. In stem-enriched cells derived from thyro-spheres cell cycle analysis and apoptotic assays were performed. Furthermore, the role of calcitriol in the formation of cancer thyro-spheres and its putative differentiation-inducing effect were analysed.

RESULTS

CSCs isolated as thyro-spheres from all the four anaplastic thyroid carcinoma cells expressed vitamin D receptors as did their parental cells. Calcitriol inhibited proliferation of anaplastic thyroid carcinoma cells with a more pronounced effect on doxorubicin-resistant HTh74R cells, and it significantly reduced the capacity to form stem cell-derived spheres and decreased the size of these spheres that consist of CSCs and their progenitor cells. As revealed by cell cycle analysis, calcitriol induced G2/M phase arrest in thyro-sphere cells derived cells from HTh74, HTh74R and C643 but did not affect apoptosis. Finally, calcitriol altered morphology of CSCs.

CONCLUSION

Calcitriol inhibited the growth of CSCs derived from anaplastic thyroid cancer cells. It may also exert a pro-differentiation effect in thyroid CSCs.

Elastin-like-polypeptide based fusion proteins for osteogenic factor delivery in bone healing

Modern treatments of bone injuries and diseases are becoming increasingly dependent on the usage of growth factors to stimulate bone growth. Bone morphogenetic protein-2 (BMP-2), a potent osteogenic inductive protein, exhibits promising results in treatment models, but recently has had its practical efficacy questioned due to the lack of local retention, ectopic bone formation, and potentially lethal inflammation. Where a new delivery technique of the BMP-2 is necessary, here we demonstrate the viability of an elastin-like peptide (ELP) fusion protein containing BMP-2 for delivery of the BMP-2. This fusion protein retains the performance characteristics of both the BMP-2 and ELP. The fusion protein was found to induce osteogenic differentiation of mesenchymal stem cells as evidenced by the production of alkaline phosphatase and extracellular calcium deposits in response to treatment by the fusion protein. Retention of the ELPs inverse phase transition property has allowed for expression of the fusion protein within a bacterial host (such as Escherichia coli) and easy and rapid purification using inverse transition cycling. The fusion protein formed self-aggregating nanoparticles at human-body temperature. The data collected suggests the viability of these fusion protein nanoparticles as a dosage-efficient and location-precise noncytotoxic delivery vehicle for BMP-2 in bone treatment. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1029-1037, 2016.

Induced Pluripotent Stem Cells as a new Strategy for Osteogenesis and Bone Regeneration

Induced pluripotent stem (iPS) cells, possess high proliferation and differentiation ability, are now considered an attractive option for osteogenic differentiation and bone regeneration. In fact, recent discoveries have demonstrated that iPS cells can be differentiated into osteoblasts, suggesting that iPS cells have the potential to advance future bone regenerative therapies. Herein, we provide an overview of the recent findings on osteogenic characteristics and differentiation potential of iPS cells. In addition, we discuss current methods for inducing their specification towards osteogenic phenotype as well as in vivo evidence supporting the therapeutic benefit of iPS-derived osteoblasts. Finally, we describe recent findings regarding the use of iPS-derived cells for osteogenic differentiation and bone regeneration, which have indicated that these pluripotent cells represent an ideal tool for regenerative cell therapies and might contribute to the development of future bone tissue engineering.

Stem cells for reutilization in bone regeneration

Bone is one of the most transplanted tissues. While most bone defects heal spontaneously, critical size defects caused by major trauma/malignant tumor and osteonecrosis of femoral head in young adults pose a great challenge in treatment. While the golden standard in treating bone defects is autologous bone grafting, available bone for grafting is quite limited in an individual. To solve the dilemma, stem cell therapy has been tried as a new modality of treatment in lesions not amenable to autologous bone grafting. While successful results were reported from individual studies, the stem cell therapy is still not an established treatment modality for bone regeneration and needs further assessment. Our focus herein is to introduce stem cell sources that have been investigated so far and review the current status of stem cell reutilization for bone regeneration as well as suggesting future perspectives.

Adipose-Derived Stem Cells for Tissue Engineering and Regenerative Medicine Applications

Adipose-derived stem cells (ASCs) are a mesenchymal stem cell source with properties of self-renewal and multipotential differentiation. Compared to bone marrow-derived stem cells (BMSCs), ASCs can be derived from more sources and are harvested more easily. Three-dimensional (3D) tissue engineering scaffolds are better able to mimic the in vivo cellular microenvironment, which benefits the localization, attachment, proliferation, and differentiation of ASCs. Therefore, tissue-engineered ASCs are recognized as an attractive substitute for tissue and organ transplantation. In this paper, we review the characteristics of ASCs, as well as the biomaterials and tissue engineering methods used to proliferate and differentiate ASCs in a 3D environment. Clinical applications of tissue-engineered ASCs are also discussed to reveal the potential and feasibility of using tissue-engineered ASCs in regenerative medicine.

Super pharmacological levels of calcitriol (1,25-(OH)2D3) inhibits mineral deposition and decreases cell proliferation in a strain dependent manner in chicken mesenchymal stem cells undergoing osteogenic differentiation in vitro

The biologically active form of vitamin D₃, calcitriol (1,25-(OH)₂D₃), plays a key role in mineral homeostasis and bone formation and dietary vitamin D₃ deficiency is a major cause of bone disorders in poultry. Supplementary dietary cholecalciferol (25-hydroxyvitamin D, 25-OH), the precursor of calcitriol, is commonly employed to combat this problem; however, dosage must be carefully determined as excess dietary vitamin D can cause toxicity resulting in a decrease in bone calcification, hypercalcinemia and renal failure. Despite much research on the therapeutic administration of dietary vitamin D in humans, the relative sensitivity of avian species to exogenous vitamin D has not been well defined. In order to determine the effects of exogenous 1,25-(OH)₂D₃ during avian osteogenesis, chicken bone marrow-derived mesenchymal stem cells (BM-MSCs) were exposed to varying doses of 1,25-(OH)₂D₃ during in vitro osteogenic differentiation and examined for markers of early proliferation and osteogenic induction. Similar to humans and other mammals, poultry BM-MSCs were found to be highly sensitive to exogenous 1,25-(OH)₂D₃ with super pharmacological levels exerting significant inhibition of mineralization and loss of cell proliferation in vitro. Strain related differences were apparent, with BM-MCSs derived from layers strains showing a higher level of sensitivity to 1,25-(OH)₂D₃ than those from broilers. These data suggest that understanding species and strain specific sensitivities to 1,25-(OH)₂D₃ is important for optimizing bone health in the poultry industry and that use of avian BM-MSCs are a useful tool for examining underlying effects of genetic variation in poultry.

Self-assembly of dual drug-delivery coating for synergistic bone regeneration

Bone regeneration for the treatment of bone diseases represents a major clinical need.

Nanoplex-Mediated Codelivery of Fibroblast Growth Factor and Bone Morphogenetic Protein Genes Promotes Osteogenesis in Human Adipocyte-Derived Mesenchymal Stem Cells

This study highlights the importance of transfection mediated coordinated bone morphogenetic protein 2 (BMP-2) and fibroblast growth factor 2 (FGF-2) signaling in promoting osteogenesis. We employed plasmids independently encoding BMP-2 and FGF-2 complexed with polyethylenimine (PEI) to transfect human adipose derived mesenchymal stem cells (hADMSCs) in vitro. The nanoplexes were characterized for size, surface charge, in vitro cytotoxicity, and transfection ability in hADMSCs. A significant enhancement in BMP-2 protein secretion was observed on day 7 post-transfection of hADMSCs with PEI nanoplexes loaded with both pFGF-2 and pBMP-2 (PEI/(pFGF-2+pBMP-2)) versus transfection with PEI nanoplexes of either pFGF-2 alone or pBMP-2 alone. Osteogenic differentiation of transfected hADMSCs was determined by measuring osteocalcin and Runx-2 gene expression using real time polymerase chain reactions. A significant increase in the expression of Runx-2 and osteocalcin was observed on day 3 and day 7 post-transfection, respectively, by cells transfected with PEI/(pFGF-2+pBMP-2) compared to cells transfected with nanoplexes containing pFGF-2 or pBMP-2 alone. Alizarin Red staining and atomic absorption spectroscopy revealed elevated levels of calcium deposition in hADMSC cultures on day 14 and day 30 post-transfection with PEI/(pFGF-2+pBMP-2) compared to other treatments. We have shown that codelivery of pFGF-2 and pBMP-2 results in a significant enhancement in osteogenic protein synthesis, osteogenic marker expression, and subsequent mineralization. This research points to a new clinically translatable strategy for achieving efficient bone regeneration.

GATA4 negatively regulates osteoblast differentiation by downregulation of Runx2

Osteoblasts are specialized mesenchymal cells that are responsible for bone formation. In this study, we examine the role of GATA4 in osteoblast differentiation. GATA4 was abundantly expressed in preosteoblast cells and gradually down-regulated during osteoblast differentiation. Overexpression of GATA4 in osteoblastic cells inhibited alkaline phosphatase activity and nodule formation in osteogenic conditioned cell culture system. In addition, overexpression of GATA4 attenuated expression of osteogenic marker genes, including Runx2, alkaline phosphatase, bone sialoprotein, and osteocalcin, all of which are important for osteoblast differentiation and function. Overexpression of GATA4 attenuated Runx2 promoter activity, whereas silencing of GATA4 increased Runx2 induction. We found that GATA4 interacted with Dlx5 and subsequently decreased Dlx5 binding activity to Runx2 promoter region. Our data suggest that GATA4 acts as a negative regulator in osteoblast differentiation by downregulation of Runx2. [BMB Reports 2014; 47(8): 463-468]

Bone morphogenetic protein-2 and vascular endothelial growth factor in bone tissue regeneration: new insight and perspectives

The study of bone tissue regeneration in orthopaedic diseases has stimulated great interest among bone tissue engineering specialists and orthopaedic surgeons. Combinations of biomaterials, growth factors and stem cells for repairing bone have been much studied and researched, yet remain a challenge for both scientists and clinicians pursuing regenerative medicine. The purpose of this review was to elucidate the role of sequential release of bone morphogenetic protein-2 and vascular endothelial growth factor in producing better outcomes in the field of bone tissue regeneration.

Synergistic and sequential effects of BMP-2, bFGF and VEGF on osteogenic differentiation of rat osteoblasts

In the present study, the effects of bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) on regulation of rat osteoblast (ROB) maturation in vitro were investigated. It was found that the proliferation, differentiation and mineralization of ROBs were all dose-dependently increased at particular times in the case of treatment with only one growth factor. To investigate the effects of combined treatment, ROBs were treated with either a single application of a relatively high dose of each growth factor, or binary/triple combined applications of relatively low doses of the growth factors. Osteogenic differentiation was significantly promoted in the triple combination treatment of BMP-2, VEGF and bFGF compared with the single or binary combination treatments. The optimal timing of the triple combination to enhance osteogenesis was also tested. When bFGF and VEGF were added in the early stage, and BMP-2 and VEGF were added in the late stage, osteogenic differentiation of ROBs could be enhanced more effectively. These results could be used to construct bone tissue engineering scaffolds that release growth factors sequentially.

The influence of 1α.25-dihydroxyvitamin d3 coating on implant osseointegration in the rabbit tibia

Objectives

This study aims to evaluate bone response to an implant surface modified by 1α,25-dihydroxyvitamin D3 [1.25-(OH)₂D₃] in vivo and the potential link between 1.25-(OH) 2D3 surface concentration and bone response.

Material and Methods

Twenty-eight implants were divided into 4 groups (1 uncoated control, 3 groups coated with 1.25-(OH)₂D₃ in concentrations of 10^-8, 10^-7 and 10^-6 M respectively), placed in the rabbit tibia for 6 weeks. Topographical analyses were carried out on coated and uncoated discs using interferometer and atomic-force-microscope (AFM). Twenty-eight implants were histologically observed (bone-to-implant-contact [BIC] and new-bone-area [NBA]).

Results

The results showed that the 1.25-(OH)₂D₃ coated implants presented a tendency to osseointegrate better than the non-coated surfaces, the differences were not significant (P > 0.05).

Conclusions

The effect of 1.25-(OH)₂D₃ coating to implants suggested possible dose dependent effects, however no statistical differences could be found. It is thought that the base substrate topography (turned) could not sustain sufficient amount of 1.25-(OH)₂D₃ enough to present significant biologic responses. Thus, development a base substrate that can sustain 1.25-(OH)₂D₃ for a long period is necessary in future studies.

Effect of the timing of surgery on the fracture healing process and the expression levels of vascular endothelial growth factor and bone morphogenetic protein-2

The aim of the present study was to observe the effect of varying the timing of surgery on the fracture healing process and the expression levels of vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP)-2 in rats. A total of 192 rats underwent closed femur fracture modelling. The rats underwent open reduction and internal fixation surgery 1, 3, 5, 7, 11 and 14 days subsequent to the fracture occurring. Immunohistochemical staining and analysis of the VEGF and BMP-2 expression levels were simultaneously conducted on bone from the fracture site of the rats on various days. The VEGF and BMP-2 expression levels at the fracture sites were higher and were maintained for a longer period of time in the 7- and 11-day surgery groups than in the other surgery groups and the rats that did not undergo surgery. The 5-day surgery group demonstrated a greater intensity in BMP-2 expression compared with the remaining surgery groups; however, no significant differences were identified between 1-day surgery and non surgery groups. In the 3-day surgery group, the expression levels VEGF and BMP-2 were low at each stage of the fracture-healing process and were lower compared with those observed in the non-surgery group. The timing of the surgical procedures affected the VEGF and BMP-2 expression levels at the fracture sites of the experimental rats and, the optimal time for performing surgery was identified to be within the first two weeks. However, surgery may not be conducive to fracture healing if it is performed within the first few days following fracture.

Tissue engineering bone using autologous progenitor cells in the peritoneum

Despite intensive research efforts, there remains a need for novel methods to improve the ossification of scaffolds for bone tissue engineering. Based on a common phenomenon and known pathological conditions of peritoneal membrane ossification following peritoneal dialysis, we have explored the possibility of regenerating ossified tissue in the peritoneum. Interestingly, in addition to inflammatory cells, we discovered a large number of multipotent mesenchymal stem cells (MSCs) in the peritoneal lavage fluid from mice with peritoneal catheter implants. The osteogenic potential of these peritoneal progenitor cells was demonstrated by their ability to easily infiltrate decalcified bone implants, produce osteocalcin and form mineralized bone in 8 weeks. Additionally, when poly(l-lactic acid) scaffolds loaded with bone morphogenetic protein-2 (a known osteogenic differentiation agent) were implanted into the peritoneum, signs of osteogenesis were seen within 8 weeks of implantation. The results of this investigation support the concept that scaffolds containing BMP-2 can stimulate the formation of bone in the peritoneum via directed autologous stem and progenitor cell responses.

Mesopattern of immobilised bone morphogenetic protein-2 created by microcontact printing and dip-pen nanolithography influence C2C12 cell fate

Making meso matter: bone morphogenetic protein-2 (BMP-2) mesopattern created by dip-pen nanolithography and microcontact printing were applied to cell differentiation.

Exogenously added BMP-6, BMP-7 and VEGF may not enhance the osteogenic differentiation of human adipose stem cells

In the present study bone morphogenetic protein (BMP)-6 alone or in synergy with BMP-7 and vascular endothelial growth factor (VEGF) were tested with human adipose stem cells (hASCs) seeded on cell culture plastic or 3D bioactive glass. Osteogenic medium (OM) was used as a positive control for osteogenic differentiation. The same growth factor groups were also tested combined with OM. None of the growth factor treatments could enhance the osteogenic differentiation of hASCs in 3D- or 2D-culture compared to control or OM. In 3D-culture OM promoted significantly total collagen production, whereas in 2D-culture OM induced high total ALP activity and mineralization compared to control and growth factors groups, but also high cell proliferation. In this study, hASCs did not respond to exogenously added growth although various parameters of the study set-up may have affected these findings contradictory to the previous literature.

The in vitro and in vivo treatment effects of overexpressed lentiviral vector-mediated human BMP2 gene in the femoral bone marrow stromal cells of osteoporotic rats

This study aimed to compare the treatment effects of lentiviral vector-mediated hBMP2 which was overexpressed in the femoral bone marrow stromal cells of osteoporotic rats through genetic infection in vitro and in vivo. Comparison of the two transgenic effects may be crucial to determining the lentivirus infection method to be used. Following a comparison of the rat bone marrow stromal cells (rBMSCs) in osteoporotic (MSCs OVX) and normal (MSCs CON) groups, the lentiviral vector-mediated human bone morphogenetic protein 2 (hBMP2), which overexpressed the BMSCs of osteoporotic rats in vitro (rBMSCs in OE group), was constructed. The osteogenic ability in the overexpressed (OE) group was then compared to that of the MSCs CON. The rBMSCs in the OE group (transplants of genetic infection in vitro) and the lentivirus-containing solution (injected material of genetic infection in vivo) were injected into the femurs. The treatment effect of each group was compared via bone mineral density (BMD) and bone histomorphometry. The hBMP2-modified osteoporosis rBMSCs formed by genetic infection in vitro (n=7) had an ameliorated treatment effect on the femur as compared to that of the in vivo (n=7) (BMD: 0.315 vs. 0.19 g/cm2, P<0.01; bone histomorphometry: For bone trabeculars (Tb.Ar/T.Ar): 0.301 vs. 0.114, P<0.01; for trabecular thickness (Tb.Th): 43.54 vs. 21.39 µm, P<0.01; for trabecular separation (Tb.Sp): 115.7 vs. 304.87 µm, P<0.01). The results showed that the treatment effects of osteoporotic rBMSCs on local osteoporosis performed by genetic infection were improved in vitro as compared to those in vivo.

Polydopamine-assisted osteoinductive peptide immobilization of polymer scaffolds for enhanced bone regeneration by human adipose-derived stem cells

Immobilization of osteoinductive molecules, including growth factors or peptides, on polymer scaffolds is critical for improving stem cell-mediated bone tissue engineering. Such molecules provide osteogenesis-stimulating signals for stem cells. Typical methods used for polymeric scaffold modification (e.g., chemical conjugation or physical adsorption), however, have limitations (e.g., multistep, complicated procedures, material denaturation, batch-to-batch inconsistency, and inadequate conjugation) that diminish the overall efficiency of the process. Therefore, in this study, we report a biologically inspired strategy to prepare functional polymer scaffolds that efficiently regulate the osteogenic differentiation of human adipose-derived stem cells (hADSCs). Polymerization of dopamine (DA), a repeated motif observed in mussel adhesive protein, under alkaline pH conditions, allows for coating of a polydopamine (pDA) layer onto polymer scaffolds. Our study demonstrates that predeposition of a pDA layer facilitates highly efficient, simple immobilization of peptides derived from osteogenic growth factor (bone morphogenetic protein-2; BMP-2) on poly(lactic-co-glycolic acid) (PLGA) scaffolds via catechol chemistry. The BMP-2 peptide-immobilized PLGA scaffolds greatly enhanced in vitro osteogenic differentiation and calcium mineralization of hADSCs using either osteogenic medium or nonosteogenic medium. Furthermore, transplantation of hADSCs using pDA-BMP-2-PLGA scaffolds significantly promoted in vivo bone formation in critical-sized calvarial bone defects. Therefore, pDA-mediated catechol functionalization would be a simple and effective method for developing tissue engineering scaffolds exhibiting enhanced osteoinductivity. To the best of our knowledge, this is the first study demonstrating that pDA-mediated surface modification of polymer scaffolds potentiates the regenerative capacity of human stem cells for healing tissue defect in vivo.

Osteogenic potential of adult stem cells from human maxillary sinus membrane by Simvastatin in vitro: preliminary report

Objectives

The objective of this study is to determine the adequate concentration and to evaluate the osteogenic potential of simvastatin in human maxillary sinus membrane-derived stem cells (hSMSC).

Materials and Methods

Mesenchymal stem cells derived from the human maxillary sinus membrane were treated with various concentrations of simvastatin. The adequate concentration of simvastatin for osteogenic induction was determined using bone morphogenetic protein (BMP-2). The efficacy of osteogenic differentiation of simavastatin was verified using osteocalcin mRNA, and the mineralization efficacy of hSMSCs and simvastatin treatment was compared with alkaline phosphatase and von Kossa staining.

Results

Expression of BMP-2 mRNA and protein was observed after three days and was dependent on the concentration of simvastatin. Expression of osteocalcin mRNA was observed after three days in the 1.0 µM simvastatin-treated group. Mineralization was observed after three days in the simvastatin-treated group.

Conclusion

These results suggest that simvastatin induces the osteogenic potential of mesenchymal stem cells derived from the human maxillary sinus membrane mucosa.

The roles of bone morphogenetic proteins and their signaling in the osteogenesis of adipose-derived stem cells

Large-size bone defects can severely compromise both aesthetics and musculoskeletal functions. Adipose-derived stem cells (ASCs)-based bone tissue engineering has recently become a promising treatment strategy for the above situation. As robust osteoinductive cytokines, bone morphogenetic proteins (BMPs) are commonly used to promote the osteogenesis of ASCs. In this process, BMP signaling plays a pivotal role. However, it remains ambiguous how the pleiotrophic BMPs are involved in the commitment of ASCs along osteogenesis instead of other lineages, such as adipogenesis. BMP receptor type-IB, extracellular signal-regulated kinase, and Wnt5a appear to be the main switches controlling the in vitro osteogenic commitment of ASCs. Tumor necrosis factor-alpha, an acute inflammatory cytokine, is reported to play an important role in mediating osteogenic commitment of ASCs in vivo. In addition, various active agents and methods have been used to enhance and accelerate the osteogenesis of ASCs through promoting BMP signaling. In this review, we summarize the current knowledge on the roles of BMPs and their signaling in the osteogenesis of ASCs in vitro and in vivo.

Efeito in vitro da triiodotironina sob o potencial osteogênico reduzido de células-tronco mesenquimais do tecido adiposo de ratas ovariectomizadas e com osteoporose

OBJETIVO: Avaliar se a triiodotironina (T3) aumenta a diferenciação osteogênica das células-tronco mesenquimais do tecido adiposo (CTM-TA) de ratas adultas ovariectomizadas e com osteoporose e compará-lo ao de ratas adultas e jovens sem osteoporose. MATERIAIS E MÉTODOS: CTM-TA foram cultivadas em meio osteogênico e distribuídas em sete grupos: 1) CTM-TA de ratas jovens sem osteoporose; 2) CTM-TA de ratas adultas sem osteoporose; 3) CTM-TA de ratas adultas com osteoporose e 4, 5, 6 e 7) CTM-TA de ratas adultas com osteoporose tratadas com T3 (0,01 nM, 1 nM, 100 nM e 1.000 nM). AVALIARAM-SE: atividade da fosfatase alcalina, conversão do dimetiltiazol (MTT), porcentagem de nódulos de mineralização, celularidade e quantificação de transcriptos gênicos para colágeno I, osteocalcina, osteopontina e Bmp-2. RESULTADOS: Independente da dose, T3 reduziu a conversão do MTT, a atividade da fosfatase, a porcentagem de células e a expressão de colágeno I em pelo menos uma das doses e dos períodos estudados (p < 0,05). Mas o tratamento com T3 não alterou o número de nódulos de mineralização e a expressão de osteopontina e Bmp-2 em culturas de CTM-TA de ratas adultas com osteoporose (p > 0,05). CONCLUSÃO: T3 apresenta efeitos negativos sobre alguns fatores envolvidos na diferenciação osteogênica de CTM-TA, sem, no entanto, reduzir a formação de nódulos de mineralização e a expressão de proteínas ósseas.

Effects of different serum conditions on osteogenic differentiation of human adipose stem cells in vitro

INTRODUCTION

Currently, human adipose stem cells (hASCs) are differentiated towards osteogenic lineages using culture medium supplemented with L-ascorbic acid 2-phosphate (AsA2-P), dexamethasone (Dex) and beta-glycerophosphate (β-GP). Because this osteogenic medium (OM1) was initially generated for the differentiation of bone marrow-derived mesenchymal stem cells, the component concentrations may not be optimal for the differentiation of hASCs. After preliminary screening, two efficient osteogenic media (OM2 and OM3) were chosen to be compared with the commonly used osteogenic medium (OM1). To further develop the culture conditions towards clinical usage, the osteo-inductive efficiencies of OM1, OM2 and OM3 were compared using human serum (HS)-based medium and a defined, xeno-free medium (RegES), with fetal bovine serum (FBS)-based medium serving as a control.

METHODS

To compare the osteo-inductive efficiency of OM1, OM2 and OM3 in FBS-, HS- and RegES-based medium, the osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity, mineralization, and expression of osteogenic marker genes (runx2A, DLX5, collagen type I, osteocalcin, and ALP).

RESULTS

In HS-based medium, the ALP activity increased significantly by OM3, and mineralization was enhanced by both OM2 and OM3, which have high AsA2-P and low Dex concentrations. ALP activity and mineralization of hASCs was the weakest in FBS-based medium, with no significant differences between the OM compositions due to donor variation. However, the qRT-PCR data demonstrated significant upregulation of runx2A mRNA under osteogenic differentiation in FBS- and HS-based medium, particularly by OM3 under FBS conditions. Further, the expression of DLX5 was greatly stimulated by OM1 to 3 on day 7 when compared to control. The regulation of collagen type I, ALP, and osteocalcin mRNA was modest under induction by OM1 to 3. The RegES medium was found to support the proliferation and osteogenic differentiation of hASCs, but the composition of the RegES medium hindered the comparison of OM1, OM2 and OM3.

CONCLUSIONS

Serum conditions affect hASC proliferation and differentiation significantly. The ALP activity and mineralization was the weakest in FBS-based medium, although osteogenic markers were upregulated on mRNA level. When comparing the OM composition, the commonly used OM1 was least effective. Accordingly, higher concentration of AsA2-P and lower concentration of Dex, as in OM2 and OM3, should be used for the osteogenic differentiation of hASCs in vitro.