Effects of cartilage oligomeric matrix protein on bone morphogenetic protein-2-induced differentiation of mesenchymal stem cells

Suppressing Chondrocyte Hypertrophy to Build Better Cartilage

Current clinical strategies for restoring cartilage defects do not adequately consider taking the necessary steps to prevent the formation of hypertrophic tissue at injury sites. Chondrocyte hypertrophy inevitably causes both macroscopic and microscopic level changes in cartilage, resulting in adverse long-term outcomes following attempted restoration. Repairing/restoring articular cartilage while minimizing the risk of hypertrophic neo tissue formation represents an unmet clinical challenge. Previous investigations have extensively identified and characterized the biological mechanisms that regulate cartilage hypertrophy with preclinical studies now beginning to leverage this knowledge to help build better cartilage. In this comprehensive article, we will provide a summary of these biological mechanisms and systematically review the most cutting-edge strategies for circumventing this pathological hallmark of osteoarthritis.

Silk-Inorganic Nanoparticle Hybrid Hydrogel as an Injectable Bone Repairing Biomaterial

Silk fibroin is regarded as a promising biomaterial in various areas, including bone tissue regeneration. Herein, Laponite^® (LAP), which can promote osteogenic differentiation, was introduced into regenerated silk fibroin (RSF) to prepare an RSF/LAP hybrid hydrogel. This thixotropic hydrogel is injectable during the operation process, which is favorable for repairing bone defects. Our previous work demonstrated that the RSF/LAP hydrogel greatly promoted the osteogenic differentiation of osteoblasts in vitro. In the present study, the RSF/LAP hydrogel was found to have excellent biocompatibility and significantly improved new bone formation in a standard rat calvarial defect model in vivo. Additionally, the underlying biological mechanism of the RSF/LAP hydrogel in promoting osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) was extensively explored. The results indicate that the RSF/LAP hydrogels provide suitable conditions for the adhesion and proliferation of BMSCs, showing good biocompatibility in vitro. With the increase in LAP content, the alkaline phosphatase (ALP) activity and mRNA and protein expression of the osteogenic markers of BMSCs improved significantly. Protein kinase B (AKT) pathway activation was found to be responsible for the inherent osteogenic properties of the RSF/LAP hybrid hydrogel. Therefore, the results shown in this study firmly suggest such an injectable RSF/LAP hydrogel with good biocompatibility (both in vitro and in vivo) would have good application prospects in the field of bone regeneration.

Osteogenic and Chondrogenic Potential of Periosteum-Derived Mesenchymal Stromal Cells: Do They Hold the Key to the Future?

The periosteum, with its outer fibrous and inner cambium layer, lies in a dynamic environment with a niche of pluripotent stem cells for their reparative needs. The inner cambium layer is rich in mesenchymal progenitors, osteogenic progenitors, osteoblasts, and fibroblasts in a scant collagen matrix environment. Their role in union and remodeling of fracture is well known. However, the periosteum as a source of mesenchymal stem cells has not been explored in detail. Moreover, with the continuous expansion of techniques, newer insights have been acquired into the roles and regulation of these periosteal cells. From a therapeutic standpoint, the periosteum as a source of tissue engineering has gained much attraction. Apart from its role in bone repair, analysis of the bone-forming potential of periosteum-derived stem cells is lacking. Hence, this article elucidates the role of the periosteum as a potential source of mesenchymal stem cells along with their capacity for osteogenic and chondrogenic differentiation for therapeutic application in the future.

A combined physicochemical approach towards human tenocyte phenotype maintenance

During in vitro culture, bereft of their optimal tissue context, tenocytes lose their phenotype and function. Considering that tenocytes in their native tissue milieu are exposed simultaneously to manifold signals, combination approaches (e.g. growth factor supplementation and mechanical stimulation) are continuously gaining pace to control cell fate during in vitro expansion, albeit with limited success due to the literally infinite number of possible permutations. In this work, we assessed the potential of scalable and potent physicochemical approaches that control cell fate (substrate stiffness, anisotropic surface topography, collagen type I coating) and enhance extracellular matrix deposition (macromolecular crowding) in maintaining human tenocyte phenotype in culture. Cell morphology was primarily responsive to surface topography. The tissue culture plastic induced the largest nuclei area, the lowest aspect ratio, and the highest focal adhesion kinase. Collagen type I coating increased cell number and metabolic activity. Cell viability was not affected by any of the variables assessed. Macromolecular crowding intensely enhanced and accelerated native extracellular matrix deposition, albeit not in an aligned fashion, even on the grooved substrates. Gene analysis at day 14 revealed that the 130 kPa grooved substrate without collagen type I coating and under macromolecular crowding conditions positively regulated human tenocyte phenotype. Collectively, this work illustrates the beneficial effects of combined physicochemical approaches in controlling cell fate during in vitro expansion.

[Expression of cartilage oligomeric matrix protein in the synovial chondromatosis of the temporomandibular joint]

OBJECTIVE

To detect the expression of cartilage oligomeric matrix protein (COMP) in the synovial chondromatosis of the temporomandibular joint (TMJSC), and to discuss the possible interactions between COMP, transforming growth factor (TGF)-β3, TGF-β1 and bone morphogenetic protein-2 (BMP-2) in the development of this neoplastic disease.

METHODS

Patients in Peking University School and Hospital of Stomatology from January 2011 to February 2020 were selected, who had complete medical records, TMJSC was verified histologically after operation. The expressions of COMP, TGF-β3, TGF-β1 and BMP-2 in the TMJSC of the temporomandibular joint were detected by immunohistochemistry and quantitative real-time PCR (RT-PCR) at the protein level and mRNA level respectively, compared with the normal synovial tissue of temporomandibular joint. The histological morphology, protein expression and distribution of TMJSC tissues were observed microscopically, and the positive staining proteins were counted and scored. SPSS 22.0 statistical software was used to analyze the expression differences between the related proteins in TMJSC tissue and the normal synovial tissue of temporomandibular joint and to compare their differences. P < 0.05 indicated that the difference was statistically significant.

RESULTS

Immunohistochemical results showed that the positive expression of COMP in TMJSC tissues was mostly found in synovial tissues and chondrocytes adjacent to synovial tissues, and the difference was statistically significant, compared with the normal temporomandibular joint synovial tissues. The positive expression of COMP was significantly different between recurrent TMJSC and non-recurrent ones. The positive expressions of TGF-β3, TGF-β1 and BMP-2 were higher than the normal synovial tissue, and were also mostly found in the synovial cells and adjacent chondrocytes, which was further confirmed by Western blot. According to the RT-PCR results, the expressions of COMP, TGF-β3, TGF-β1 and BMP-2 in TMJSC were higher than those in the normal synovial tissue.

CONCLUSION

The expression of COMP in TMJSC of temporomandibular joint increased significantly, compared with the normal synovial tissue. There may be interactions between COMP and cytokines related to the proliferation and differentiation, like TGF-β3, TGF-β1 and BMP-2, which may play a potential role in the pathogenesis of TMJSC.

ADAMTS7 degrades Comp to fuel BMP2-dependent osteogenic differentiation and ameliorate oncogenic potential in osteosarcomas

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents, with a high metastatic potential. Despite dramatic changes in OS treatments over the past decades, their efficiency still remains limited, with severe complications and adverse side effects. Key mechanisms underlining tumorigenesis, metastasis and chemotherapy resistance are currently lacking, in turn hindering any progress with respect to developing effective and safe therapeutic strategies against OS. Recently, ADAMTS7, a member of the disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family, was shown to be involved in osteogenic differentiation‐related pathological processes. ADAMTS7 promotes vascular calcification via disturbing the balance between osteogenic bone morphogenetic protein (BMP)2 (regulating osteogenic differentiation and bone formation during development) and its natural inhibitor cartilage oligomeric matrix protein (Comp). Hence, in the present study, we aimed to investigate the role of ADAMTS7 in the pathological process of OS. We first revealed that ADAMTS7 was decreased in OS tissues. Lower expression of ADAMTS7 was correlated with poor histological differentiation and an advanced clinical stage of OS. Through loss‐ and gain‐function analysis, we further revealed that ADAMTS7 attenuated cell proliferation, migration and invasion, at the same time as promoting the expression of osteogenic differentiation markers in two OS cell lines: MG63 and SAOS2. Moreover, Comp was responsible for the effects of ADAMTS7 on OS pathogenesis by reinforcing cell osteogenic differentiation mediated by BMP2 in vitro. In conclusion, ADAMTS7‐mediated degradation of Comp may provide a potential therapeutic target for the treatment of OS.

Synergistic Effects of Kartogenin and Transforming Growth Factor-β3 on Chondrogenesis of Human Umbilical Cord Mesenchymal Stem Cells In Vitro

OBJECTIVE

To explore the effect of kartogenin (KGN) on proliferation and chondrogenic differentiation of human umbilical cord mesenchymal stem cells (hUCMSC) in vitro, and the synergistic effects of KGN and transforming growth factor (TGF)-β3 on hUCMSC.

METHODS

Human umbilical cord mesenchymal stem cells were isolated and cultured. Then the differentiation properties were identified by flow cytometry analysis. HUCMSC were divided into four groups: control group, KGN group, TGF-β3 group, and TK group (with TGF-β3 and KGN added into the medium simultaneously). Cells in all groups were induced for 21 days using the suspension ball culture method. Hematoxylin and eosin, immunofluorescence, and Alcian blue staining were used to analyze chondrogenic differentiation. Real-time reverse transcriptase polymerase chain reaction was performed to investigate genes associated with chondrogenic differentiation.

RESULT

Hematoxylin and eosin staining showed that cells in the TGF-β3 group and the TK group had formed cartilage-like tissue after 21 days of culture. The results of immunofluorescence and Alcian blue staining showed that compared with the control group, cells in the KGN and TGF-β3 groups demonstrated increased secretion of aggrecan after 21 days of culture. In addition, cells in the group combining KGN with TGF-β3 (5.587 ± 0.27, P < 0.01) had more collagen II secretion than cells in the TGF-β3 alone group (2.86 ± 0.141, P < 0.01) or the KGN group (1.203 ± 0.215, P < 0.01). The expression of aggrecan (2.468 ± 0.097, P < 0.05) and SRY-Box 9 (4.08 ± 0.13, P < 0.05) in cells in the group combining KGN with TGF-β3 was significantly higher than those in the TGF-β3 group (2.216 ± 0.09, 3.02 ± 0.132, P < 0.05).'

CONCLUSION

The combination of KGN and TGF-β3 had synergistic effects and induced hUCMSC chondrogenesis. This could represent a new approach for clinical application and studies on cartilage repair and regeneration.

Combinatorial Screening of Nanoclay-Reinforced Hydrogels: A Glimpse of the "Holy Grail" in Orthopedic Stem Cell Therapy?

Despite the promise of hydrogel-based stem cell therapies in orthopedics, a significant need still exists for the development of injectable microenvironments capable of utilizing the  regenerative potential of donor cells. Indeed, the quest for biomaterials that can direct stem cells into bone without the need of external factors has been the "Holy Grail" in orthopedic stem cell therapy for decades. To address this challenge, we have utilized a combinatorial approach to screen over 63 nanoengineered hydrogels made from alginate, hyaluronic acid, and two-dimensional nanoclays. Out of these combinations, we have identified a biomaterial that can promote osteogenesis in the absence of well-established differentiation factors such as bone morphogenetic protein 2 (BMP2) or dexamethasone. Notably, in our "hit" formulations we observed a 36-fold increase in alkaline phosphate (ALP) activity and a 11-fold increase in the formation of mineralized matrix, compared to the control hydrogel. This induced osteogenesis was further supported by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy. Additionally, the Montmorillonite-reinforced hydrogels exhibited high osteointegration as evident from the relatively stronger adhesion to the bone explants as compared to the control. Overall, our results demonstrate the capability of combinatorial and nanoengineered biomaterials to induce bone regeneration through osteoinduction of stem cells in a natural and differentiation-factor-free environment.

BMP7-overexpressing bone marrow-derived mesenchymal stem cells (BMSCs) are more effective than wild-type BMSCs in healing fractures

Bone fractures are a worldwide public health concern. Previous studies have demonstrated that bone morphogenetic protein-7 (BMP7) gene transfer or mesenchymal stem cells (MSCs) transplantation may be a promising novel therapeutic approach. Therefore, the aim of the present study was to observe the effect of bone BMP7 transfer to MSCs on fracture healing. Bone marrow-derived MSCs (BMSCs) from New Zealand white rabbits were isolated and identified using flow cytometry. A recombinant BMP7 overexpressing adenovirus vector (Adv) was constructed and transfected into BMSCs. The expression of BMP7 was detected by reverse transcription-polymerase chain reaction, immunofluorescence and western blotting. The present study additionally investigated the effect of BMP7 on the differentiation capacity of BMSCs. Finally, tissue-engineered bone was created with support material to verify the effect of BMP7-BMSCs on fracture healing. The results demonstrated that the expression of BMP7 was increased at the mRNA and protein levels in BMSCs following transfection with BMP7 overexpressing Adv. The results additionally demonstrated that the expression of BMP7 enhanced the differentiation capacity of bone marrow mesenchymal stem cells and had a promotional effect on fracture healing. Overall, these data suggest that Adv-BMP7 is useful for introducing foreign genes into BMSCs and will be a powerful gene therapy tool for bone regeneration and other tissue engineering applications in the future.

Transcriptome analyses reveal molecular mechanisms that regulate endochondral ossification in amphibian Bufo gargarizans during metamorphosis

BACKGROUND

A developmental transition from aquatic to terrestrial existence is one of the most important events in the evolution of terrestrial vertebrates. Amphibian metamorphosis is a classic model to study this transition. The development of the vertebrate skeleton can reflect its evolutionary history. Endochondral ossification serves a vital role in skeletal development. Thus, we sought to unravel molecular mechanisms that regulate endochondral ossification during Bufo gargarizans metamorphosis.

METHODS

The alizarin red-alcian blue double staining method was used to visualize the skeletal development of B. gargarizans during metamorphosis. RNA sequencing (RNA-seq) was used to explore the transcriptome of B. gargarizans in four key developmental stages during metamorphosis. Real-time quantitative PCR (RT-qPCR) was used to validate the expression patterns of endochondral ossification related genes.

RESULTS

Endochondral ossification increased gradually in skeletal system of B. gargarizans during metamorphosis. A total of 137,264 unigenes were assembled and 44,035 unigenes were annotated. 10,352 differentially expressed genes (DEGs) were further extracted among four key developmental stages. In addition, 28 endochondral ossification related genes were found by searching for DEG libraries in B. gargarizans. Of the 28 genes, 10 genes were validated using RT-qPCR.

CONCLUSIONS

The exquisite coordination of the 28 genes is essential for regulation of endochondral ossification during B. gargarizans metamorphosis.

GENERAL SIGNIFICANCE

The present study will not only provide an invaluable genomic resource and background for further research of endochondral ossification in amphibians but will also aid in enhancing our understanding of the evolution of terrestrial vertebrates.

TET2 Loss Dysregulates the Behavior of Bone Marrow Mesenchymal Stromal Cells and Accelerates Tet2-/--Driven Myeloid Malignancy Progression

TET2 is a methylcytosine dioxygenase that regulates cytosine hydroxymethylation. Although there are extensive data implicating a pivotal role of TET2 in hematopoietic stem/progenitor cells (HSPCs), the importance of TET2 in bone marrow mesenchymal stromal cells (BMSCs) remains unknown. In this study, we show that loss of TET2 in BMSCs increases cell proliferation and self-renewal and enhances osteoblast differentiation potential of BMSCs, which may in turn alter their behavior in supporting HSPC proliferation and differentiation. In addition, Tet2 loss alters BMSCs in promoting Tet2-deficiency-mediated myeloid malignancy progression. Tet2 loss in BMSCs also dysregulates hydroxylation of 5-methylcytosine (5mC) and the expression of genes that are key for BMSC proliferation and osteoblast differentiation, leading to alteration of biological characteristics in vivo. These results highlight the critical role of TET2 in the maintenance of BMSC functions and osteoblast differentiation and provide evidence that dysregulation of epigenetic modifiers in BMSCs contributes to the progression of myeloid malignancies.

Cartilage oligomeric matrix protein improves in vivo cartilage regeneration and compression modulus by enhancing matrix assembly and synthesis

Cartilage oligomeric matrix protein (COMP), an abundant cartilage extracellular matrix protein, plays an important role in mesenchymal chondrogenesis. To test our hypothesis that COMP could promote tissue engineering cartilage regeneration as well as improve cartilaginous mechanical properties, COMP gene transfected rabbit bone marrow mesenchymal stem cells (BMSCs) were used for chondrogenic differentiation in vitro and were implanted with biphasic scaffolds into osteochondral defects of New Zealand white rabbit trochlear grooves for cartilage regeneration in vivo. In vitro, over expressed COMP could enhance the chondrogenic differentiation and ECM secretion of BMSCs. After euthanasia at 12 weeks post implantation, macroscopic observation, histological staining, mechanical tests and micro-CT were performed for the assessment of repaired cartilage. Overexpression of COMP leads to more newly formed hyaline cartilage and significantly improved mechanical property. These results demonstrated the significant role of COMP in the cartilage regeneration in vivo and offered inspiring advantage of COMP in the application of tissue engineering.

The footprint of the ageing stroma in older patients with breast cancer

Background

Tumours are not only composed of malignant cells but also consist of a stromal micro-environment, which has been shown to influence cancer cell behaviour. Because the ageing process induces accumulation of senescent cells in the body, this micro-environment is thought to be different in cancers occurring in old patients compared with younger patients. More specifically, senescence-related fibroblastic features, such as the senescence-associated secretory profile (SASP) and the induction of autophagy, are suspected to stimulate tumour growth and progression.

Methods

We compared gene expression profiles in stromal fields of breast carcinomas by performing laser capture microdissection of the cancer-associated stroma from eight old (aged ≥80 years at diagnosis) and nine young (aged <45 years at diagnosis) patients with triple-negative breast cancer. Gene expression data were obtained by microarray analysis (Affymetrix). Differential gene expression and gene set enrichment analysis (GSEA) were performed.

Results

Differential gene expression analysis showed changes reminiscent of increased growth, de-differentiation and migration in stromal samples of older versus younger patients. GSEA confirmed the presence of a SASP, as well as the presence of autophagy in the stroma of older patients.

Conclusions

We provide the first evidence in humans that older age at diagnosis is associated with a different stromal micro-environment in breast cancers. The SASP and the presence of autophagy appear to be important age-induced stromal features.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0871-0) contains supplementary material, which is available to authorized users.

The Signaling Pathways Involved in Chondrocyte Differentiation and Hypertrophic Differentiation

Chondrocytes communicate with each other mainly via diffusible signals rather than direct cell-to-cell contact. The chondrogenic differentiation of mesenchymal stem cells (MSCs) is well regulated by the interactions of varieties of growth factors, cytokines, and signaling molecules. A number of critical signaling molecules have been identified to regulate the differentiation of chondrocyte from mesenchymal progenitor cells to their terminal maturation of hypertrophic chondrocytes, including bone morphogenetic proteins (BMPs), SRY-related high-mobility group-box gene 9 (Sox9), parathyroid hormone-related peptide (PTHrP), Indian hedgehog (Ihh), fibroblast growth factor receptor 3 (FGFR3), and β-catenin. Except for these molecules, other factors such as adenosine, O₂ tension, and reactive oxygen species (ROS) also have a vital role in cartilage formation and chondrocyte maturation. Here, we outlined the complex transcriptional network and the function of key factors in this network that determine and regulate the genetic program of chondrogenesis and chondrocyte differentiation.

Enhancing the Gelation and Bioactivity of Injectable Silk Fibroin Hydrogel with Laponite Nanoplatelets

Regenerated silk fibroin (RSF) of Bombyx mori silk fiber is a promising natural material for bone defect repair. However, a lack of specific integrin and growth factor for osteoinduction significantly hinders its application in this area. In this study, the role of Laponite nanoplatelet (LAP), a bioactive clay that can promote osteoblast growth, in the formation of RSF hydrogel, as well as the various properties of RSF/LAP hybrid hydrogel, was closely investigated. The results indicate that LAP could serve as a medium to accelerate hydrophobic interaction among the RSF molecules and a disruptor to limit the growth of β-sheet domain during the gelation of RSF. Rheological measurement suggests that the RSF/LAP hydrogel is injectable as it displays thixotropy in the room temperature. Proliferation and differentiation results of the primary osteoblasts encapsulated in hydrogel show that RSF/LAP hydrogel can promote the cell proliferation and enhance the osteogenic differentiation. The transcript levels for alkaline phosphatase, osteocalcin, osteopontin, and collagen type I osteogenic markers obviously improve with RSF/LAP hydrogel compared to the controls at 14 days, especially with the higher contents of LAP. Overall, the results suggest that the RSF/LAP hydrogel have great potential to be utilized as an injectable biomaterial for irregular bone defect repair.