Characterization of human ethmoid sinus mucosa derived mesenchymal stem cells (hESMSCs) and the application of hESMSCs cell sheets in bone regeneration

Preparation, properties and in vitro osteogensis of self-reinforcing injectable hydrogel

As an attractive biomaterial for bone reconstruction, injectable biomaterials have many prominent characteristics such as good biocompatibility and bone-filling ability. However, there are weak as load-bearing scaffolds. In this study, polyvinyl alcohol (PVA) and bioactive glass (BAG) were interpenetrated into sodium alginate (SA) network to obtain self-enhanced injectable hydrogel. The optimum ratio of PVA/SA/BAG hydrogel was determined based on injectability, gelation time and chemical characterization. Results showed that the selected ratio had the shortest gelation time of 3.5min, and the hydrogel had a rough surface and good coagulation property. The hydrogel was capable of carrying 1kg of weight by mineralization for 14 d The compressive strength, compressive modulus, and fracture energy of the hydrogel reached 0.12MPa, 0.376MPa and 17.750kJ m-2, respectively. Meanwhile, the hydrogel had high moisture content and dissolution rate, and it was sensitive to temperature and ionic strength. Hydroxyapatite was generated on the hydrogel surface, and the hydrogel pores increased, and the pore size enlarged. The biocompatibility of PVA/SA/BAG hydrogel was analyzed using hemolysis and cytotoxicity assays. Results revealed its good biocompatibility with low hemolysis rate and no cytotoxicity to MC3T3-E1 cells. The hydrogel was also found to promote the differentiation of MC3T3-E1 cells with significantly increased in ALP activity and expression of relevant differentiation factors. In vitro mineralization assay showed an increase in calcium nodules and calcification area, indicating the ability of hydrogel to promote mineralization MC3T3-E1 cells. These findings indicated that PVA/SA/BAG hydrogel had potential uses in the field of irregular bone-defect repair due to its injectability, cytocompatibility, and tailorable functionality.

A composite membrane with microtopographical morphology to regulate cellular behavior for improved tissue regeneration

Tissue engineering scaffolds with specific surface topographical morphologies can regulate cellular behaviors and promote tissue repair. In this study, poly lactic(co-glycolic acid) (PLGA)/wool keratin composite guided tissue regeneration (GTR) membranes with three types of microtopographies (three groups each of pits, grooves and columns, thus nine groups in total) were prepared. Then, the effects of the nine groups of membranes on cell adhesion, proliferation and osteogenic differentiation were examined. The nine different membranes had clear, regular and uniform surface topographical morphologies. The 2 µm pit-structured membrane had the best effect on promoting the proliferation of bone marrow mesenchymal stem cells (BMSCs) and periodontal ligament stem cells (PDLSCs), while the 10 µm groove-structured membrane was the best for inducing osteogenic differentiation of BMSCs and PDLSCs. Then, we investigated the ectopic osteogenic, guided bone tissue regeneration and guided periodontal tissue regeneration effects of the 10 µm groove-structured membrane combined with cells or cell sheets. The 10 µm groove-structured membrane/cell complex had good compatibility and certain ectopic osteogenic effects, and the 10 µm groove-structured membrane/cell sheet complex promoted better bone repair and regeneration and periodontal tissue regeneration. Thus, the 10 µm groove-structured membrane shows potential to treat bone defects and periodontal disease. STATEMENT OF SIGNIFICANCE: PLGA/wool keratin composite GTR membranes with microcolumn, micropit and microgroove topographical morphologies were prepared by dry etching technology and the solvent casting method. The composite GTR membranes had different effects on cell behavior. The 2 µm pit-structured membrane had the best effect on promoting the proliferation of rabbit BMSCs and PDLSCs and the 10 µm groove-structured membrane was the best for inducing the osteogenic differentiation of BMSCs and PDLSCs. The combined application of a 10 µm groove-structured membrane and PDLSC sheet can promote better bone repair and regeneration as well as periodontal tissue regeneration. Our findings may have significant potential for guiding the design of future GTR membranes with topographical morphologies and clinical applications of the groove-structured membrane/cell sheet complex.

Periostin plays a key role in maintaining the osteogenic abilities of dental follicle stem cells in the inflammatory microenvironment

OBJECTIVE

This study aimed to explore the effect of periostin in the osteogenic abilities of dental follicle stem cells (DFSCs) and DFSC sheets in the inflammatory microenvironment.

DESIGN

DFSCs were isolated from dental follicles and identified. A lentiviral vector was used to knock down periostin in DFSCs. 250 ng/ml lipopolysaccharide from Porphyromonas gingivalis (P.g-LPS) was used to construct the inflammatory microenvironment. Osteogenic differentiation was evaluated by alizarin red staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot. The formation of extracellular matrix was assessed by qRT-PCR and immunofluorescence. The expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) were measured by western blot.

RESULTS

Knockdown of periostin inhibited osteogenic differentiation and promoted adipogenic differentiation of DFSCs. In an inflammatory microenvironment, knockdown of periostin attenuated the proliferation and osteogenic differentiation of DFSCs. Knockdown of periostin inhibited the formation of extracellular matrix collagen I (COL-I), fibronectin, and laminin in DFSC sheets, but did not affect the expression of osteogenesis-related markers alkaline phosphatase (ALP) and osteocalcin (OCN). In the inflammatory microenvironment, knocking down periostin inhibited the expression of OCN and OPG in DFSC sheets, and promoted the expression of RANKL.

CONCLUSION

Periostin played a key role in maintaining the osteogenic abilities of DFSCs and DFSC sheets in the inflammatory microenvironment and might be an important molecule in the process of DFSCs coping with inflammatory microenvironment and promoting periodontal tissues regeneration.

Application of mesenchymal stem cell sheet for regeneration of craniomaxillofacial bone defects

Bone defects are among the most common damages in human medicine. Due to limitations and challenges in the area of bone healing, the research field has turned into a hot topic discipline with direct clinical outcomes. Among several available modalities, scaffold-free cell sheet technology has opened novel avenues to yield efficient osteogenesis. It is suggested that the intact matrix secreted from cells can provide a unique microenvironment for the acceleration of osteoangiogenesis. To the best of our knowledge, cell sheet technology (CST) has been investigated in terms of several skeletal defects with promising outcomes. Here, we highlighted some recent advances associated with the application of CST for the recovery of craniomaxillofacial (CMF) in various preclinical settings. The regenerative properties of both single-layer and multilayer CST were assessed regarding fabrication methods and applications. It has been indicated that different forms of cell sheets are available for CMF engineering like those used for other hard tissues. By tackling current challenges, CST is touted as an effective and alternative therapeutic option for CMF bone regeneration.

Role of periosteum in alveolar bone regeneration comparing with collagen membrane in a buccal dehiscence model of dogs

To investigate the role of periosteum on the treatment of buccal dehiscence defects comparing with collagen membrane in canine model. Bilateral dehiscence-type defects at the buccal side on the distal root of the lower 3rd/4th premolars were created in six beagle dogs with a total of 24 defects and assigned into three groups: Group A: blood clot in an untreated defect; Group B: deproteinized bovine bone material (DBBM) covered with an absorbable membrane; Group C: DBBM covered with the periosteum. The structural parameters for trabecular architecture and vertical bone regeneration were evaluated. Histological and histomorphometric evaluation were carried out to observe new bone formation and mineralization in the graft site. Immunohistochemical analysis was performed to identify the expression of osteopontin (OPN) and osteocalcin (OCN) at postoperative 3 months. Group C achieved greater vertical alveolar bone gain than that of group A and group B. The periosteum-covered group showed significantly greater new bone formation and accelerated mineralization. The greater immunolabeling for OPN and OCN was observed in group C than in group A. Periosteal coverage has explicit advantages over collagen membranes for the quality and quantity of new bone regeneration in dehiscence defects repairing.

Cell Sheet Technology as an Engineering-Based Approach to Bone Regeneration

Bone defects that are congenital or the result of infection, malignancy, or trauma represent a challenge to the global healthcare system. To address this issue, multiple research groups have been developing novel cell sheet technology (CST)-based approaches to promote bone regeneration. These methods hold promise for use in regenerative medicine because they preserve cell-cell contacts, cell-extracellular matrix interactions, and the protein makeup of cell membranes. This review introduces the concept and preparation system of the cell sheet (CS), explores the application of CST in bone regeneration, highlights the current states of the bone regeneration via CST, and offers perspectives on the challenges and future research direction of translating current knowledge from the lab to the clinic.

Titania-Nanotube-Coated Titanium Substrates Promote Osteogenesis and Suppress Osteoclastogenesis via Integrin ανβ3

The balance of bone turnover mediated by osteoclastogenesis and osteogenesis implants that could suppress osteoclastogenesis and promote osteogenesis is an appropriate treatment strategy for osteoporosis patients. Titanium is one of the most applied materials in implants. In this study, titania nanotubes (Ti-NTs) were produced by anodization at 10, 40, and 60 V. We found that Ti-NTs were nontoxic to bone marrow mesenchymal stem cells (BMSCs). Ti-NTs suppressed osteoclast formation and function in a diameter dependent manner in vitro. Furthermore, Ti-NTs enhanced the activity of osteogenesis, expressions of osteogenesis-related marker genes were increased and β-Catenin pathway was active. Alkaline phosphatase (ALP) activity and matrix mineralization were also promoted in vitro. To explore the possible mechanisms, we performed a series of experiments to indicate the effects of Ti-NTs on cytoskeletal organization and integrin ανβ3 expression of osteoclasts and osteoblasts. The results demonstrated that 90-nm-diameter Ti-NTs could suppress the expression of integrin ανβ3 in osteoclast precursor cells. Interestingly, it revealed an opposite effect on BMSCs. Moreover, 90 nm-diameter Ti-NTs prevented ovariectomy (OVX)-induced bone loss. These findings indicated that Ti-NTs could inhibit osteoclastogenesis and enhance osteogenesis; it was mediated via regulation of integrin ανβ3─90 nm-diameter Ti-NT revealed a good biological ability especially suited for osteoporosis treatment.

Construction of biomimetic cell-sheet-engineered periosteum with a double cell sheet to repair calvarial defects of rats

Background

The periosteum plays a crucial role in the development and injury healing process of bone. The purpose of this study was to construct a biomimetic periosteum with a double cell sheet for bone tissue regeneration.

Methods

In vitro, the human amniotic mesenchymal stem cells (hAMSCs) sheet was first fabricated by adding 50 ​μg/ml ascorbic acid to the cell sheet induction medium. Characterization of the hAMSCs sheet was tested by general observation, microscopic observation, live/dead staining, scanning electron microscopy (SEM) and hematoxylin and eosin (HE) staining. Afterwards, the osteogenic cell sheet and vascular cell sheet were constructed and evaluated by general observation, alkaline phosphatase (ALP) staining, Alizarin Red S staining, SEM, live/dead staining and CD31 immunofluorescent staining for characterization. Then, we prepared the double cell sheet. In vivo, rat calvarial defect model was introduced to verify the regeneration of bone defects treated by different methods. Calvarial defects (diameter: 4 ​mm) were created of Sprague–Dawley rats. The rats were randomly divided into 4 groups: the control group, the osteogenic cell sheet group, the vascular cell sheet group and the double cell sheet group. Macroscopic, micro-CT and histological evaluations of the regenerated bone were performed to assess the treatment results at 8 weeks and 12 weeks after surgery.

Results

In vitro, hAMSCs sheet was successfully prepared. The hAMSCs sheet consisted of a large number of live hAMSCs and abundant extracellular matrix (ECM) that secreted by hAMSCs, as evidenced by macroscopic/microscopic observation, live/dead staining, SEM and HE staining. Besides, the osteogenic cell sheet and the vascular cell sheet were successfully prepared, which were verified by general observation, ALP staining, Alizarin Red S staining, SEM and CD31 immunofluorescent staining. In vivo, the macroscopic observation and micro-CT results both demonstrated that the double cell sheet group had better effect on bone regeneration than other groups. In addition, histological assessments indicated that large amounts of new bone had formed in the calvarial defects and more mature collagen in the double cell sheet group.

Conclusion

The double cell sheet could promote to repair calvarial defects of rats and accelerate bone regeneration.

The translational potential of this article

We successfully constructed a biomimetic cell-sheet-engineered periosteum with a double cell sheet by a simple, low-cost and effective method. This biomimetic periosteum may be a promising therapeutic strategy for the treatment of bone defects, which may be used in clinic in the future.

hAMSC Sheet Promotes Repair of Rabbit Osteochondral Defects

Osteochondral lesion is clinically common disease, which has been recognized as one of the contributing factors of significant morbidity. Although current treatments have achieved good outcomes, some undesirable complications and failures are not uncommon. Cell sheet technology (CST), an innovative technology to harvest seed cells and preserve abundant ECM, has been widely used in various tissue regeneration. For osteochondral lesion, many studies focus on using CST to repair osteochondral lesion and have achieved good outcomes. In the previous study, we have demonstrated that hAMSC sheet had a positive effect on osteochondral lesion. Therefore, this study is aimed at comparing the effect of noninduced hAMSC sheet with chondrogenically induced hAMSC sheet on osteochondral lesion and cartilage regeneration.

Fabrication of oxidized sodium alginate-collagen heterogeneous bilayer barrier membrane with osteogenesis-promoting ability

Guided bone regeneration technique is an effective approach to repair bone defects, in which a barrier membrane is essential. However, the collagen barrier membranes commonly used lose stability quickly, leading to connective tissue invasion and failure of osteogenesis. Herein, we presented an oxidized sodium alginate (OSA)-collagen heterogeneous bilayer barrier membrane with well-controlled pore size and osteogenesis-promoting ability. The OSA crosslinking significantly improved the structural stability, compressive strength, swelling behavior, and slowed down the biodegradation rate of collagen membranes. Meanwhile, the collagen-based membranes exhibited superior cytocompatibility, osteogenesis-promotion, and barrier function against fibroblasts. Especially, the osteogenic differentiation was most promoted on the membrane with a large pore size (240-310 μm), while the barrier function was most improved on the membrane with a small pore size (30-60 μm). Then the above two membranes were combined together to obtain a heterogeneous bilayer membrane. This bilayer barrier membrane showed excellent osteogenesis-promoting ability in rats.

Optimization of a Tricalcium Phosphate-Based Bone Model Using Cell-Sheet Technology to Simulate Bone Disorders

Bone diseases such as osteoporosis, delayed or impaired bone healing, and osteoarthritis still represent a social, financial, and personal burden for affected patients and society. Fully humanized in vitro 3D models of cancellous bone tissue are needed to develop new treatment strategies and meet patient-specific needs. Here, we demonstrate a successful cell-sheet-based process for optimized mesenchymal stromal cell (MSC) seeding on a β-tricalcium phosphate (TCP) scaffold to generate 3D models of cancellous bone tissue. Therefore, we seeded MSCs onto the β-TCP scaffold, induced osteogenic differentiation, and wrapped a single osteogenically induced MSC sheet around the pre-seeded scaffold. Comparing the wrapped with an unwrapped scaffold, we did not detect any differences in cell viability and structural integrity but a higher cell seeding rate with osteoid-like granular structures, an indicator of enhanced calcification. Finally, gene expression analysis showed a reduction in chondrogenic and adipogenic markers, but an increase in osteogenic markers in MSCs seeded on wrapped scaffolds. We conclude from these data that additional wrapping of pre-seeded scaffolds will provide a local niche that enhances osteogenic differentiation while repressing chondrogenic and adipogenic differentiation. This approach will eventually lead to optimized preclinical in vitro 3D models of cancellous bone tissue to develop new treatment strategies.

A Review: Optimization for Poly(glycerol sebacate) and Fabrication Techniques for Its Centered Scaffolds

Poly(glycerol sebacate) (PGS), an emerging promising thermosetting polymer synthesized from sebacic acid and glycerol, has attracted considerable attention due to its elasticity, biocompatibility, and tunable biodegradation properties. But it also has some drawbacks such as harsh synthesis conditions, rapid degradation rates, and low stiffness. To overcome these challenges and optimize PGS performance, various modification methods and fabrication techniques for PGS-based scaffolds have been developed in recent years. Outlining the current modification approaches of PGS and summarizing the fabrication techniques for PGS-based scaffolds are of great importance to accelerate the development of new materials and enable them to be appropriately used in potential applications. Thus, this review comprehensively overviews PGS derivatives, PGS composites, PGS blends, processing for PGS-based scaffolds, and their related applications. It is envisioned that this review could instruct and inspire the design of the PGS-based materials and facilitate tissue engineering advances into clinical practice.

Effects of miR-672 on the angiogenesis of adipose-derived mesenchymal stem cells during bone regeneration

BACKGROUND

Sufficient vascular network plays an important role in the repair of bone defects. Bone morphogenetic protein 2 (BMP2) being a key regulator of angiogenesis has attracted the attention of researchers. In addition, evidence has suggested that BMP2 coordinates with microRNAs (miRNAs) to form intracellular networks regulating mesenchymal stem cells (MSCs) angiogenesis. Elucidating the underlying mechanisms that are regulating adipose-derived mesenchymal stem cells (ADSCs) angiogenesis might provide more effective method to enhance bone regeneration.

METHODS

We identified the specific miRNA in rat ADSCs during BMP2-induced angiogenesis and chose the most significant differentially expressed miRNA, miR-672. Three lentiviral system named Lenti-miR-672, Lenti-as-miR-672, and Lenti-miR-NC were transduced into the ADSCs individually. Then, the quantitative real-time polymerase chain reaction (qPCR), western blotting, and blood vessel formation analysis were performed to investigate the effects of miR-672 on ADSCs angiogenesis. Bioinformation platforms were used to screen the potential target of miR-672. Small interfering RNA (siRNA) against TIMP2 (si-TIMP2) mRNA were obtained from GenePharma, and then si-TIMP2 miRNA and miR-672 were co-transfected into ADSCs to detect the effects of TIMP2 on angiogenesis. Calcium phosphate cement (CPC) scaffolds that seeded the lentiviral-modified ADSCs were constructed to test the vascularized bone regeneration in vivo.

RESULTS

Our data showed that after the angiogenesis of ADSCs induced by BMP2, miR-672 was the most significantly upregulated miRNA. Overexpression of miR-672 promoted the angiogenesis of ADSCs, while knockdown of miR-672 repressed the angiogenesis of ADSCs. The bioinformation prediction showed that TIMP2 might be the one of miR-672' potential targets. TIMP2 protein expression was gradually decreased in ADSCs with overexpressed miR-672. And the angiogenic factors were upregulated in the ADSCs which were transduced with si-TIMP2. Then, the CPC scaffolds coupled the miR-672-modified ADSCs and showed the good potential in vascularized bone regeneration. The overexpressed miR-672 could greatly enhance the blood vessel volume and Microfil-labeled blood vessel numbers in newly formed bone.

CONCLUSION

BMP2 could promote the angiogenesis of ADSCs through stimulating the expression of miR-672 in ADSCs. miR-672 acted as a positive regulator on the angiogenesis of ADSCs, and incorporating the miR-672-modified ADSCs in the CPC could significantly promote the vascularization and the bone regeneration.

Silk-based hybrid microfibrous mats as guided bone regeneration membranes

LAPONITE® (LAP) nanoplatelets were incorporated within a regenerated silk fibroin (RSF) microfibrous mat via electrospinning, which exhibited better cell adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs) than the pristine RSF ones.

Recent advances in light-induced cell sheet technology

Various stimuli have been applied to harvest complete cell sheets, including temperature, magnetic, pH, and electrical stimuli. Cell sheet technology is a convenient and efficient approach with beneficial effects for tissue regeneration and cell therapy. Lights of different wavelengths, such as ultraviolet (UV), visible light, and near infrared ray (NIR) light, were confirmed to aid in fabricating a cell sheet. Changes in the wettability, potential, or water content of the culturing surfaces that occur under light illumination induce conformational changes in the adhesive proteins or collagens, which then leads to cell sheet detachment. However, the current approaches face several limitations, as few standards for safe light illumination have been proposed to date, and require a careful control of the wavelength, power, and irradiation time. Future studies should aim at generating new materials for culturing and releasing cell sheets rapidly and effectively.

Tissue engineering using a combined cell sheet technology and scaffolding approach

Cell sheet technology has remained quite popular among tissue engineering techniques over the last several years. Meanwhile, there is an apparent trend in modern scientific research towards combining different approaches and strategies. Accordingly, a large body of work has arisen where cell sheets are used not as separate structures, but in combination with scaffolds as supporting constructions. The aim of this review is to analyze the intersection of these two vast areas of tissue engineering described in the literature mainly within the last five years. Some practical and technical details are emphasized to provide information that can be useful in research design and planning. The first part of the paper describes the general issues concerning the use of combined technology, its advantages and limitations in comparison with those of other tissue engineering approaches. Next, the detailed literature analysis of in vivo studies aimed at the regeneration of different tissues is performed. A significant part of this section concerns bone regeneration. In addition to that, other connective tissue structures, including articular cartilage and fibrocartilage, ligaments and tendons, and some soft tissues are discussed. STATEMENT OF SIGNIFICANCE: This paper describes the intersection of two technologies used in designing of tissue-engineered constructions for regenerative medicine: cell sheets as extracellular matrix-rich structures and supporting scaffolds as essentials in tissue engineering. A large number of reviews are devoted to each of these scientific problems. However, the solution of complex problems of tissue engineering requires an integrated approach that includes both three-dimensional scaffolds and cell sheets. This manuscript serves as a description of advantages and limitations of this method, its use in regeneration of bones, connective tissues and soft tissues and some other details.

Polyhedral Oligomeric Silsesquioxane-Incorporated Gelatin Hydrogel Promotes Angiogenesis during Vascularized Bone Regeneration

Many approaches have been made toward the development of scaffolds with good biocompatibility and appreciable physicochemical properties to facilitate stem cell adhesion, osteogenic differentiation, and vascularization in tissue engineering. Nowadays, vascularization is a main bottleneck in tissue engineering strategies that is needed to be overcome and developed. Herein, we construct a series of polyhedral oligomeric silsesquioxane (POSS)-modified porous gelatin hydrogels with different POSS concentrations from 0 to 5 wt %, defined as X% POSS hydrogels (X = 0, 1, 2, 3, 4, 5) to support vascularized bone repair. The introduction of POSS into gelatin effectively promoted adhesive protein adsorption and integrin α5β1 expression, subsequently leading to enhanced adhesion of both rat bone marrow mesenchymal stem cells and human umbilical vein endothelial cells (HUVECs). In vitro experiments further demonstrated that POSS-containing hybrid hydrogels more effectively support the angiogenic tube and network formation in HUVECs than the 0% POSS hydrogel. Besides, POSS-containing hybrid hydrogels showed desirable performance as a sustained release system of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2), and they further accelerated vascular network establishment and the formation of a new bone in defect regions. When the hydrogels were implanted into critical-sized rat calvarial defects in vivo, the VEGF/BMP-2-coupled 3% POSS group gained a higher blood vessel volume in the bone defect regions (5.49 ± 0.35 mm³) than the 3% POSS group (3.12 ± 0.20 mm³) and the 0% POSS group (1.57 ± 0.25 mm³), suggesting that the 3% POSS hydrogel with VEGF/BMP-2 would expedite vascularization. Based on these evaluations, our results indicated that the POSS-incorporated gelatin hydrogel would provide a promising bone graft scheme in potential clinical application of large bone defect repair.

Effect of Bifunctional β Defensin 2-Modified Scaffold on Bone Defect Reconstruction

Bone tissue engineering has emerged as an effective alternative treatment to the problem of bone defect. To repair a bone defect, antibiosis and osteogenesis are two essential aspects of the repair process. By searching the literature and performing exploratory experiments, we found that β defensin 2 (BD2), with bifunctional properties of antibiosis and osteogenesis, was a feasible alternative for traditional growth factors. The antimicrobial ability of BD2 against Staphylococcus aureus and Escherichia coli was studied by the spread plate and live/dead staining methods (low effective concentration of 20 ng/mL). BD2 was also demonstrated to enhance osteogenesis, with higher messenger RNA (mRNA) and protein expression of the osteogenic markers collagen I (Col1), runt-related transcription factor 2 (Runx2), osteopontin (Opn), and osteocalcin (Ocn) in vitro (1.5-2.5-fold increase compared with the control group in the most effective concentration group), which was consistent with the alkaline phosphatase (ALP) and alizarin red S (ARS) staining results. We implanted poly(sebacoyl diglyceride) (PSeD) combined with BD2 and rat bone tissue-derived mesenchymal stem cells (rBMSCs) under the back skin of rats and found that the inflammatory response was significantly lower with this combination than with the PSeD/rBMSCs scaffold without BD2 and the pure PSeD group and was similar to the control group. Importantly, when assessed in a critical-sized in vivo rat 8 m diameter calvaria defect model, a scaffold we developed combining bifunctional BD2 with porous organic polymer displayed an osteogenic effect that was 160-200% greater than the control group. The in vivo study results revealed a significant osteogenic response and antimicrobial effect and were consistent with the in vitro results. In summary, BD2 displayed a great potential of simultaneously promoting bone regeneration and preventing infection and could provide a viable alternative to traditional growth factors applied in bone defect repair.

Recent advances in cell sheet technology for bone and cartilage regeneration: from preparation to application

Bone defects caused by trauma, tumour resection, infection and congenital deformities, together with articular cartilage defects and cartilage-subchondral bone complex defects caused by trauma and degenerative diseases, remain great challenges for clinicians. Novel strategies utilising cell sheet technology to enhance bone and cartilage regeneration are being developed. The cell sheet technology has shown great clinical potential in regenerative medicine due to its effective preservation of cell-cell connections and extracellular matrix and its scaffold-free nature. This review will first introduce several widely used cell sheet preparation systems, including traditional approaches and recent improvements, as well as their advantages and shortcomings. Recent advances in utilising cell sheet technology to regenerate bone or cartilage defects and bone-cartilage complex defects will be reviewed. The key challenges and future research directions for the application of cell sheet technology in bone and cartilage regeneration will also be discussed.

Rat sinus mucosa- and periosteum-derived exosomes accelerate osteogenesis

Guided bone regeneration (GBR) is commonly used for alveolar bone augmentation. The paracrine mechanism in the field of bone tissue engineering has been emphasized in recent years and exosomes are considered to have the potential of promoting osteogenesis. We aimed to study the influence of sinus mucosa and periosteum on bone regeneration through paracrine stimulation, especially via exosomes, and compare the differences between them. Here, we report that conditioned medium (CM) from sinus mucosa-derived cells (SMCs) and periosteum-derived cells (PCs) and the isolated exosomes enhanced the proliferation, migration and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs) in vitro. A rat model of femoral bone defects was used to demonstrate that the exosomes derived from SMCs (SMC-Exos) and PCs (PC-Exos) can accelerate bone formation in vivo. Furthermore, we present a preliminary discussion of the possible functional components involved in the effects of SMC-Exos and PC-Exos on bone regeneration. In conclusion, these results demonstrated that the sinus mucosa and periosteum can accelerate osteogenesis through paracrine effects and the exosomes play important roles in this process.

Effects of combined menaquinone-4 and PTH1-34 treatment on osetogenesis and angiogenesis in calvarial defect in osteopenic rats

PURPOSE

The aim of this study was to evaluate the effect of combining human parathyroid hormone (1-34) (PTH_1-34; PTH) and menaquinone-4 (MK-4) on calvarial bone defect repair in osteopenic rats.

METHODS

Fourteen week olds were subject to craniotomy for the establishment of osteopenic animal models fed through a chronically low-protein diet. After that, critical calvarial defect model was established and all rats were randomly divided into four groups: sham, MK-4, PTH, and PTH + MK-4. The animals received MK-4 (30 mg/kg/day), PTH_1-34 (60 μg/kg, three times a week), or PTH_1-34 (60 μg/kg, three times a week) plus MK-4 (30 mg/kg/day) for 8 weeks, respectively. Serum γ-carboxylated osteocalcin (Gla-OC) levels, histological and immunofluorescent labeling were employed to evaluate the bone formation and mineralization in calvarial bone defect. In addition, Microfil perfusion, immunohistochemical, and micro-CT suggested enhanced angiogenesis and bone formation in calvarial bone healing.

RESULTS

In this study, treatment with either PTH_1-34 or MK-4 promoted bone formation and vascular formation in calvarial bone defects compared with the sham group. In addition, combined treatment of PTH_1-34 plus MK-4 increased serum level of Gla-OC, improved vascular number and vascular density, and enhanced bone formation in calvarial bone defect in osteopenic conditions as compared with monotherapy.

CONCLUSIONS

In summary, this study indicated that PTH_1-34 plus MK-4 combination therapy accelerated bone formation and angiogenesis in calvarial bone defects in presence of osteopenia.

Mesenchymal stem cell sheets: a new cell-based strategy for bone repair and regeneration

Mesenchymal stem cells (MSCs), a class of adult stem cells, are considered a promising source for bone regeneration. Although combining MSCs with biomaterial scaffolds offers an interesting clinical strategy for bone tissue engineering, the presence of the scaffolds could induce an undesirable effect on cell-cell interactions. Moreover, before the application of scaffold materials in bone tissue reconstruction, cells must be manipulated with proteolytic enzymes, such as trypsin or dispase that degrade extracellular matrix (ECM) molecules and cell surface proteins, which can result in the cell damage and loss of cellular activity. Therefore, the development of alternative strategies for bone regeneration is required to solve these problems. Recently, a novel tissue engineering technology named 'cell sheet' has been efficaciously utilized in the regeneration of bone, corneal, cardiac, tracheal and periodontal ligament-like tissues. The cell sheet is a layer of cells, which contains intact ECM and cell surface proteins such as growth factor receptors, ion channels and cell-to-cell junction proteins. MSC sheets can be easily fabricated by layering the recovered cell sheets without any scaffolds or complicated manipulation. This review summarizes the current state of the literature regarding the use of MSCs to produce cell sheets and assesses their applicability in bone tissue regeneration and repair.

In situ bone regeneration enabled by a biodegradable hybrid double-network hydrogel

The biodegradable hybrid double-network hydrogel for stem cell-enhanced bone regeneration.

Evaluation of Mesenchymal Stem Cell Sheets Overexpressing BMP-7 in Canine Critical-Sized Bone Defects

The aim of this study was to investigate the in vitro osteogenic capacity of bone morphogenetic protein 7 (BMP-7) overexpressing adipose-derived (Ad-) mesenchymal stem cells (MSCs) sheets (BMP-7-CS). In addition, BMP-7-CS were transplanted into critical-sized bone defects and osteogenesis was assessed. BMP-7 gene expressing lentivirus particles were transduced into Ad-MSCs. BMP-7, at the mRNA and protein level, was up-regulated in BMP-7-MSCs compared to expression in Ad-MSCs. Osteogenic and vascular-related gene expressions were up-regulated in BMP-7-CS compared to Ad-MSCs and Ad-MSC sheets. In a segmental bone-defect model, newly formed bone and neovascularization were enhanced with BMP-7-CS, or with a combination of BMP-7-CS and demineralized bone matrix (DBM), compared to those in control groups. These results demonstrate that lentiviral-mediated gene transfer of BMP-7 into Ad-MSCs allows for stable BMP-7 production. BMP-7-CS displayed higher osteogenic capacity than Ad-MSCs and Ad-MSC sheets. In addition, BMP-7-CS combined with demineralized bone matrix (DBM) stimulated new bone and blood vessel formation in a canine critical-sized bone defect. The BMP-7-CS not only provides BMP-7 producing MSCs but also produce osteogenic and vascular trophic factors. Thus, BMP-7-CS and DBM have therapeutic potential for the treatment of critical-sized bone defects and could be used to further enhance clinical outcomes during bone-defect treatment.

Biomimetic Viruslike and Charge Reversible Nanoparticles to Sequentially Overcome Mucus and Epithelial Barriers for Oral Insulin Delivery

Nanoparticles (NPs) for oral delivery of peptide/protein drugs are largely limited due to the coexistence of intestinal mucus and epithelial barriers. Sequentially overcoming these two barriers is intractable for a single nanovehicle due to the requirements of different or even contradictory surface properties of NPs. To solve this dilemma, a mucus-penetrating virus-inspired biomimetic NP with charge reversal ability (P-R8-Pho NPs) was developed by densely coating poly(lactic- co-glycolic acid) NPs with cationic octa-arginine (R8) peptide and specific anionic phosphoserine (Pho). The small size (81.81 nm) and viruslike neutral charged surface (-2.39 mV) of the biomimetic NPs achieved rapid mucus penetration, which was almost equal to that of the conventional PEGylated mucus-penetrating nanoparticles. The hydrolysis of surface-anchored anionic Pho was achieved by intestinal alkaline phosphatase, which led to the turnover of ζ potential to positive (+7.37 mV). This timely charge reversal behavior also exposed cationic R8 peptide and induced efficient cell-penetrating peptide (CPP)-mediated cellular uptake and transepithelial transport on Caco-2/E12 cocultured cell model. What's more, P-R8-Pho NPs showed excellent stability in simulated gastrointestinal conditions and enhanced absorption in intestine in vivo. Finally, oral administration of insulin-loaded P-R8-Pho NPs enabled to induce a preferable hypoglycemic effect and a 1.9-fold higher oral bioavailability was achieved compared with single CPP-modified P-R8 NPs on diabetic rats. The combinative application of biomimetic mucus-penetrating strategy and enzyme-responsive charge reversal strategy in a single nanovehicle could sequentially overcome mucus and epithelial barriers, thus showing great potential for the oral peptide/protein delivery.

Biomimetic Tissue-Engineered Bone Substitutes for Maxillofacial and Craniofacial Repair: The Potential of Cell Sheet Technologies

Maxillofacial defects are complex lesions stemming from various etiologies: accidental, congenital, pathological, or surgical. A bone graft may be required when the normal regenerative capacity of the bone is exceeded or insufficient. Surgeons have many options available for bone grafting including the "gold standard" autologous bone graft. However, this approach is not without drawbacks such as the morbidity associated with harvesting bone from a donor site, pain, infection, or a poor quantity and quality of bone in some patient populations. This review discusses the various bone graft substitutes used for maxillofacial and craniofacial repair: allografts, xenografts, synthetic biomaterials, and tissue-engineered substitutes. A brief overview of bone tissue engineering evolution including the use of mesenchymal stem cells is exposed, highlighting the first clinical applications of adipose-derived stem/stromal cells in craniofacial reconstruction. The importance of prevascularization strategies for bone tissue engineering is also discussed, with an emphasis on recent work describing substitutes produced using cell sheet-based technologies, including the use of thermo-responsive plates and the self-assembly approach of tissue engineering. Indeed, considering their entirely cell-based design, these natural bone-like substitutes have the potential to closely mimic the osteogenicity, osteoconductivity, osteoinduction, and osseointegration properties of autogenous bone for maxillofacial and craniofacial reconstruction.

[Application of cell sheet technology in bone and cartilage tissue engineering]

Objective

To review the progress of cell sheet technology and its application in bone and cartilage engineering.

Methods

The recent literature concerning the cell sheet technology used in treatment of bone and cartilage defects was extensively reviewed and summarized.

Results

Cell sheet built through many different ways can protect extracellular matrix from proteolytic enzymes. As a three-dimensional structure, cell sheet can repair bone and cartilige defects via folding, wrapping scaffold, or be created by the layering of individual cell sheets.

Conclusion

The cell sheet technology would have a very broad prospects in bone and cartilage tissue engineering in future.

Bone regeneration with osteogenic matrix cell sheet and tricalcium phosphate: An experimental study in sheep

AIM

To determine the effects of a cell sheet created from sheep bone marrow and tricalcium phosphate (TCP) on osteogenesis.

METHODS

Bone marrow cells were harvested from a sheep and cultured in a minimal essential medium (MEM) containing ascorbic acid phosphate (AscP) and dexamethasone (Dex). After 2 wk, the formed osteogenic matrix cell sheet was lifted from the culture dish using a scraper. Additionally, harvested bone marrow cells were cultured in MEM only as a negative control group, and in MEM with AscP, Dex, and β-glycerophosphate as a positive control group. For in vitro evaluation, we measured the alkaline phosphatase (ALP) activity and osteocalcin (OC) content in the media of the cultured cells from each group. For in vivo analysis, a porous TCP ceramic was used as a scaffold. We prepared an experimental group comprising TCP scaffolds wrapped with the osteogenic matrix cell sheets and a control group consisting of the TCP scaffold only. The constructs were implanted subcutaneously into athymic rats and the cell donor sheep, and bone formation was confirmed by histology after 4 wk.

RESULTS

In the in vitro part, the mean ALP activity was 0.39 ± 0.03 mg/well in the negative control group, 0.67 ± 0.04 mg/well in the sheet group, and 0.65 ± 0.07 mg/well in the positive control group. The mean OC levels were 1.46 ± 0.33 ng/well in the negative control group, 3.92 ± 0.16 ng/well in the sheet group, and 4.4 ± 0.47 ng/well in the positive control group, respectively. The ALP activity and OC levels were significantly higher in the cell sheet and positive control groups than in the negative control group (P < 0.05). There was no significant difference in ALP activity or OC levels between the cell sheet group and the positive control group (P > 0.05). TCP constructs wrapped with cell sheets prior to implantation showed bone formation, in contrast to TCP scaffolds alone, which exhibited poor bone formation when implanted, in the subcutaneous layer both in athymic rats and in the sheep.

CONCLUSION

This technique for preparing highly osteoinductive TCP may promote regeneration in large bone defects.

Poly (fumaroyl bioxirane) maleate: A potential functional scaffold for bone regeneration

Proper scaffolds combined with mesenchymal stem cells (MSCs) represent a promising strategy for repairing bone defects. In a previous study, poly (fumaroyl bioxirane) maleate (PFM), a newly developed functional polymer with numerous functional groups, exhibited excellent biocompatibility and enhanced the alkaline phosphatase (ALP) activity of osteoblasts in vitro. Here, to provide further and comprehensive insight into the application of PFM in bone tissue engineering, we investigated the osteoinductive potential of PFM cultured with rat adipose-derived mesenchymal stem cells (rADSCs). The results showed that PFM resulted in greater proliferation of rADSCs and that the PFM substrate had stronger osteoinductivity than PLGA and the control, as indicated by the significant upregulation of osteogenesis-related genes, proteins and calcium mineralization in vitro. Next, PFM was combined with rADSCs to repair a critical-sized calvarial defect in rats. Compared to the PLGA scaffold, the PFM scaffold significantly promoted new bone formation and exhibited excellent effects in repairing rat calvarial defects. In conclusion, PFM possesses strong osteoinductivity, which could markedly enhance bone regeneration, suggesting that PFM could serve as a promising and effective optimization method for traditional scaffolds in bone regeneration.

Effects of miR-146a on the osteogenesis of adipose-derived mesenchymal stem cells and bone regeneration

Increasing evidence has indicated that bone morphogenetic protein 2 (BMP2) coordinates with microRNAs (miRNAs) to form intracellular networks regulating mesenchymal stem cells (MSCs) osteogenesis. This study aimed to identify specific miRNAs in rat adipose-derived mesenchymal stem cells (ADSCs) during BMP2-induced osteogenesis, we selected the most significantly down-regulated miRNA, miR-146a, to systematically investigate its role in regulating osteogenesis and bone regeneration. Overexpressing miR-146a notably repressed ADSC osteogenesis, whereas knocking down miR-146a greatly promoted this process. Drosophila mothers against decapentaplegic protein 4 (SMAD4), an important co-activator in the BMP signaling pathway, was miR-146a’s direct target and miR-146a exerted its repressive effect on SMAD4 through interacting with 3′-untranslated region (3′-UTR) of SMAD4 mRNA. Furthermore, knocking down SMAD4 attenuated the ability of miR-146a inhibitor to promote ADSC osteogenesis. Next, transduced ADSCs were incorporated with poly(sebacoyl diglyceride) (PSeD) porous scaffolds for repairing critical-sized cranial defect, the treatment of miR-146a inhibitor greatly enhanced ADSC-mediated bone regeneration with higher expression levels of SMAD4, Runt-related transcription factor 2 (Runx2) and Osterix in newly formed bone. In summary, our study showed that miR-146a negatively regulates the osteogenesis and bone regeneration from ADSCs both in vitro and in vivo.

Improved osseointegrating functionality of cell sheets on anatase TiO2 nanoparticle surfaces

Bone marrow mesenchymal stem cell sheets (BMSC sheets) have been reported as a powerful tool for bioengineering applications in accelerating osseointegration.

In vitro osteogenic induction of bone marrow mesenchymal stem cells with a decellularized matrix derived from human adipose stem cells and in vivo implantation for bone regeneration

Tissue engineering technology that adopts mesenchymal stem cells combined with scaffolds presents a promising strategy for tissue regeneration.

PEGylated poly(glycerol sebacate)-modified calcium phosphate scaffolds with desirable mechanical behavior and enhanced osteogenic capacity

Calcium phosphate (CaP) scaffolds have been widely used as bone graft substitutes, but undesirable mechanical robustness and bioactivity greatly hamper its availability in clinic application. To address these issues, PEGylated poly (glycerol sebacate) (PEGS), a hydrophilic elastomer, was used to modify a model calcium phosphate cement (CPC) scaffold for bone regeneration in this study. The PEGS pre-polymer with PEG content from 0% to 40% was synthesized and was subsequently coated onto the pre-fabricated CPC scaffolds by facile infiltration and thermal-crosslink process. Compression strength and toughness of the CPC/PEGS composite scaffold (defined as CPX/Y, X referred to the PEG content in PEGS and Y referred to PEGS amount in final scaffold) were effectively tailored with increasing coating amount and PEG content, and CPX/Y exhibited an optimal compressive strength of 3.82MPa and elongation at break of 13.20%, around 5-fold and 3-fold enhancement compared to the CPC. In vitro cell experiment with BMSCs as model indicated that coating and PEG-modified synchronously facilitated cell attachment and proliferation in a dose-dependent manner. Particularly, osteogenic differentiation of BMSCs on PEGS/CPC scaffold was strongly enhanced, especially for CP20/18. Further in vivo experiments confirmed that PEGS/CPC induced promoted osteogenesis in striking contrast to CPC and PGS/CPC. Collectively, hybrids scaffolds (around 18% coating amount and PEG content from 20% to 40%) with the combination of enhanced mechanical behavior and up-regulated cellular response were optimized and PEGS/CaP scaffolds can be deemed as a desirable option for bone tissue engineering.

STATEMENT OF SIGNIFICANCE

Insufficient mechanical robustness and bioactivity still limit the availability of calcium phosphate (CaP) scaffolds in clinic application. Herein, calcium phosphate cement (CPC) scaffold, as a model CaP-matrix material, was modified with PEGylated PGS (PEGS) polymers by facile infiltration and thermal-crosslink process. Such biomimetic combination of PEGS and CaP-matrix porous scaffold was first explored, without affecting its porous structure. In this study, CPC scaffold was endowed with robust mechanical behavior and promoted bioactivity by simultaneously optimizing the amount of polymer-coating and the PEG content in PGS. In rat critical-sized calvarial defects repairing, osteogenic efficacy of PEGS/CPC further demonstrated the potential for application in bone tissue regeneration. The design concept proposed in this study might provide new insights into the development of future tissue engineering materials.

Comparison of Osteogenesis between Adipose-Derived Mesenchymal Stem Cells and Their Sheets on Poly-ε-Caprolactone/β-Tricalcium Phosphate Composite Scaffolds in Canine Bone Defects

Multipotent mesenchymal stem cells (MSCs) and MSC sheets have effective potentials of bone regeneration. Composite polymer/ceramic scaffolds such as poly-ε-caprolactone (PCL)/β-tricalcium phosphate (β-TCP) are widely used to repair large bone defects. The present study investigated the in vitro osteogenic potential of canine adipose-derived MSCs (Ad-MSCs) and Ad-MSC sheets. Composite PCL/β-TCP scaffolds seeded with Ad-MSCs or wrapped with osteogenic Ad-MSC sheets (OCS) were also fabricated and their osteogenic potential was assessed following transplantation into critical-sized bone defects in dogs. The alkaline phosphatase (ALP) activity of osteogenic Ad-MSCs (O-MSCs) and OCS was significantly higher than that of undifferentiated Ad-MSCs (U-MSCs). The ALP, runt-related transcription factor 2, osteopontin, and bone morphogenetic protein 7 mRNA levels were upregulated in O-MSCs and OCS as compared to U-MSCs. In a segmental bone defect, the amount of newly formed bone was greater in PCL/β-TCP/OCS and PCL/β-TCP/O-MSCs/OCS than in the other groups. The OCS exhibit strong osteogenic capacity, and OCS combined with a PCL/β-TCP composite scaffold stimulated new bone formation in a critical-sized bone defect. These results suggest that the PCL/β-TCP/OCS composite has potential clinical applications in bone regeneration and can be used as an alternative treatment modality in bone tissue engineering.

Hydrogel as a bioactive material to regulate stem cell fate

The encapsulation of stem cells in a hydrogel substrate provides a promising future in biomedical applications. However, communications between hydrogels and stem cells is complicated; various factors such as porosity, different polymer types, stiffness, compatibility and degradation will lead to stem cell survival or death. Hydrogels mimic the three-dimensional extracellular matrix to provide a friendly environment for stem cells. On the other hand, stem cells can sense the surroundings to make the next progression, stretching out, proliferating or just to remain. As such, understanding the correlation between stem cells and hydrogels is crucial. In this Review, we first discuss the varying types of the hydrogels and stem cells, which are most commonly used in the biomedical fields and further investigate how hydrogels interact with stem cells from the perspective of their biomedical application, while providing insights into the design and development of hydrogels for drug delivery, tissue engineering and regenerative medicine purpose. In addition, we compare the results such as stiffness, degradation time and pore size as well as peptide types of hydrogels from respected journals. We also discussed most recently magnificent materials and their effects to regulate stem cell fate.

•

Hydrogels as Extracellular Matrix (ECM) mimics stem cells proliferation and differentiation.

•

Discuss how hydrogels interact with stem cells from the perspective of their biomedical applications.

•

Recent magnificent materials and their effects to regulate stem cells fate.

Electrospun silk fibroin/poly(lactide-co-ε-caprolactone) nanofibrous scaffolds for bone regeneration

Background

Tissue engineering has become a promising therapeutic approach for bone regeneration. Nanofibrous scaffolds have attracted great interest mainly due to their structural similarity to natural extracellular matrix (ECM). Poly(lactide-co-ε-caprolactone) (PLCL) has been successfully used in bone regeneration, but PLCL polymers are inert and lack natural cell recognition sites, and the surface of PLCL scaffold is hydrophobic. Silk fibroin (SF) is a kind of natural polymer with inherent bioactivity, and supports mesenchymal stem cell attachment, osteogenesis, and ECM deposition. Therefore, we fabricated hybrid nanofibrous scaffolds by adding different weight ratios of SF to PLCL in order to find a scaffold with improved properties for bone regeneration.

Methods

Hybrid nanofibrous scaffolds were fabricated by blending different weight ratios of SF with PLCL. Human adipose-derived stem cells (hADSCs) were seeded on SF/PLCL nanofibrous scaffolds of various ratios for a systematic evaluation of cell adhesion, proliferation, cytotoxicity, and osteogenic differentiation; the efficacy of the composite of hADSCs and scaffolds in repairing critical-sized calvarial defects in rats was investigated.

Results

The SF/PLCL (50/50) scaffold exhibited favorable tensile strength, surface roughness, and hydrophilicity, which facilitated cell adhesion and proliferation. Moreover, the SF/PLCL (50/50) scaffold promoted the osteogenic differentiation of hADSCs by elevating the expression levels of osteogenic marker genes such as BSP, Ocn, Col1A1, and OPN and enhanced ECM mineralization. In vivo assays showed that SF/PLCL (50/50) scaffold improved the repair of the critical-sized calvarial defect in rats, resulting in increased bone volume, higher trabecular number, enhanced bone mineral density, and increased new bone areas, compared with the pure PLCL scaffold.

Conclusion

The SF/PLCL (50/50) nanofibrous scaffold facilitated hADSC proliferation and osteogenic differentiation in vitro and further promoted new bone formation in vivo, suggesting that the SF/PLCL (50/50) nanofibrous scaffold holds great potential in bone tissue regeneration.

A regulatory loop containing miR-26a, GSK3β and C/EBPα regulates the osteogenesis of human adipose-derived mesenchymal stem cells

Elucidating the molecular mechanisms responsible for osteogenesis of human adipose-derived mesenchymal stem cells (hADSCs) will provide deeper insights into the regulatory mechanisms of this process and help develop more efficient methods for cell-based therapies. In this study, we analysed the role of miR-26a in the regulation of hADSC osteogenesis. The endogenous expression of miR-26a increased during the osteogenic differentiation. The overexpression of miR-26a promoted hADSC osteogenesis, whereas osteogenesis was repressed by miR-26a knockdown. Additionally, miR-26a directly targeted the 3′UTR of the GSK3β, suppressing the expression of GSK3β protein. Similar to the effect of overexpressing miR-26a, the knockdown of GSK3β promoted osteogenic differentiation, whereas GSK3β overexpression inhibited this process, suggesting that GSK3β acted as a negative regulator of hADSC osteogenesis. Furthermore, GSK3β influences Wnt signalling pathway by regulating β-catenin, and subsequently altered the expression of its downstream target C/EBPα. In turn, C/EBPα transcriptionally regulated the expression of miR-26a by physically binding to the CTDSPL promoter region. Taken together, our data identified a novel feedback regulatory circuitry composed of miR-26a, GSK3β and C/EBPα, the function of which might contribute to the regulation of hADSC osteogenesis. Our findings provided new insights into the function of miR-26a and the mechanisms underlying osteogenesis of hADSCs.