miR-486-5p Attenuates Steroid-Induced Adipogenesis and Osteonecrosis of the Femoral Head Via TBX2/P21 Axis.

Enhanced adipogenic differentiation of mesenchymal stem cells (MSCs) is considered as a major risk factor for steroid-induced osteonecrosis of the femoral head (SOFNH). The role of microRNAs during this process has sparked interest. miR-486-5p expression was down-regulated significantly in femoral head bone tissues of both SONFH patients and rat models. The purpose of this study was to reveal the role of miR-486-5p on MSCs adipogenesis and SONFH progression. The present study showed that miR-486-5p could significantly inhibit adipogenesis of 3T3-L1 cells by suppressing mitotic clonal expansion (MCE). And upregulated expression of P21, which was caused by miR-486-5p mediated TBX2 decrease, was responsible for inhibited MCE. Further, miR-486-5p was demonstrated to effectively inhibit steroid-induced fat formation in the femoral head and prevented SONFH progression in a rat model. Considering the potent effects of miR-486-5p on attenuating adipogenesis, it seems to be a promising target for the treatment of SONFH.

MiR-601-induced BMSCs senescence accelerates steroid-induced osteonecrosis of the femoral head progression by targeting SIRT1.

BACKGROUND: The imbalance between osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is not only the primary pathological feature but also a major contributor to the pathogenesis of steroid-induced osteonecrosis of the femoral head (SONFH). Cellular senescence is one of the main causes of imbalanced BMSCs differentiation. The purpose of this study was to reveal whether cellular senescence could participate in the progression of SONFH and the related mechanisms. METHODS: The rat SONFH model was constructed, and rat BMSCs were extracted. Aging-related indicators were detected by SA-ß-Gal staining, qRT-PCR and Western Blot experiments. Using H2O2 to construct a senescent cell model, and overexpressing and knocking down miR-601 and SIRT1 in hBMSCs, the effect on BMSCs differentiation was explored by qRT-PCR, Western Blot experiment, oil red O staining (ORO), alizarin red staining (ARS), and luciferase reporter gene experiment. A rat SONFH model was established to test the effects of miR-601 and metformin in vivo. RESULTS: The current study showed that glucocorticoids (GCs)-induced BMSCs senescence, which caused imbalanced osteogenesis and adipogenesis of BMSCs, was responsible for the SONFH progression. Further, elevated miR-601 caused by GCs was demonstrated to contribute to BMSCs senescence through targeting SIRT1. In addition, the anti-aging drug metformin was shown to be able to alleviate GCs-induced BMSCs senescence and SONFH progression. CONCLUSIONS: Considering the role of BMSCs aging in the progression of SONFH, this provides a new idea for the prevention and treatment of SONFH.

Evaluating the reliability of the lateral femoral condyle measuring methods by different modalities for patients with lateral patellar dislocation.

BACKGROUND: A variety of measurement methods and imaging modalities are in use to quantify the morphology of lateral femoral condyle (LFC), but the most reliable method remains elusive in patients with lateral patellar dislocation (LPD). The purpose of this study was to determine the intra- and inter-observer reliability of different measurement methods for evaluating the morphology of LFC on different imaging modalities in patients with LPD. METHODS: Seventy-three patients with LPD were included. Four parameters for quantifying the morphology of LFC were retrospectively measured by three observers on MRI, sagittal CT image, conventional radiograph (CR), and three-dimensional CT (3D-CT). The intra-class correlation coefficient was calculated to determine the intra- and inter-observer reliability. Bland-Altman analysis was conducted to identify the bias between observers. RESULTS: The lateral femoral condyle index (LFCI) showed better intra- and inter-observer reliability on MRI and 3D-CT than on CR and sagittal CT images. The mean difference in the LFCI between observers was lowest on 3D-CT (0.047), higher on MRI (0.053), and highest on sagittal CT images (0.062). The LFCI was associated with the lateral femoral condyle ratio (ρ = 0.422, P = 0.022), lateral condyle index (r = 0.413, P = 0.037), and lateral femoral condyle distance (r = 0.459, P = 0.014). The LFCI could be reliably measured by MRI and 3D-CT. CONCLUSION: The LFCI could be reliably measured by MRI and 3D-CT. The LFCI was associated with both the height and length of LFC and could serve as a comprehensive parameter for quantifying the morphology of LFC in patients with LPD.

MET promotes the proliferation and differentiation of myoblasts.

The receptor tyrosine kinase MET plays a vital role in skeletal muscle development and in postnatal muscle regeneration. However, the effect of MET on myogenesis of myoblasts has not yet been fully understood. This study aimed to investigate the effects of MET on myogenesis in vivo and in vitro. Decreased myonuclei and down-regulated expression of myogenesis-related markers were observed in Met p.Y1232C mutant heterozygous mice. To explore the effects of MET on myoblast proliferation and differentiation, Met was overexpressed or interfered in C2C12 myoblast cells through the lentiviral transfection. The Met overexpression cells exhibited promotion in myoblast proliferation, while the Met deficiency cells showed impediment in proliferation. Moreover, myoblast differentiation was enhanced by the stable Met overexpression, but was impaired by Met deficiency. Furthermore, this study demonstrated that SU11274, an inhibitor of MET kinase activity, suppressed myoblast differentiation, suggesting that MET regulated the expression of myogenic regulatory factors (MRFs) and of desmin through the classical tyrosine kinase pathway. On the basis of the above findings, our work confirmed that MET promoted the proliferation and differentiation of myoblasts, deepening our understanding of the molecular mechanisms underlying muscle development.

A novel ZRS variant causes preaxial polydactyly type I by increased sonic hedgehog expression in the developing limb bud.

PURPOSE: Preaxial polydactyly (PPD) is a common congenital hand malformation classified into four subtypes (PPD I-IV). Variants in the zone of polarizing activity regulatory sequence (ZRS) within intron 5 of the LMBR1 gene are linked to most PPD types. However, the genes responsible for PPD I and the underlying mechanisms are unknown. METHODS: A rare large four-generation family with isolated PPD I was subjected to genome-wide genotyping and sequence analysis. In vitro and in vivo functional studies were performed in Caco-2 cells, 293T cells, and a knockin transgenic mouse model. RESULTS: A novel g.101779T>A (reference sequence: NG_009240.2; position 446 of the ZRS) variant segregates with all PPD I-affected individuals. The knockin mouse with this ZRS variant exhibited PPD I phenotype accompanying ectopic and excess expression of Shh. We confirmed that HnRNP K can bind the ZRS and SHH promoters. The ZRS mutant enhanced the binding affinity for HnRNP K and upregulated SHH expression. CONCLUSION: Our results identify the first PPD I disease-causing variant. The variant leading to PPD I may be associated with enhancing SHH expression mediated by HnRNP K. This study adds to the ZRS-associated syndromes classification system for PPD and clarifies the underlying molecular mechanisms.

Melatonin prevents bone destruction in mice with retinoic acid-induced osteoporosis.

BACKGROUND: The protective effect of melatonin against bone metabolism imbalance in osteoporosis (OP) induced by drugs such as retinoic acid (RA) is unclear. The aim of this study was to explore the role of melatonin in bone destruction based on a mouse model. METHODS: RA-induced OP model mice were established. To assess the effect of melatonin on these mice, micro-CT was used to characterize the trabecular structure of normal mice and those treated with RA (model), RA + low-dose melatonin (Mlt-L), RA + high-dose melatonin (Mlt-H), and RA + alendronate sodium (positive control). The shape of the trabecular bone, the length and diameter of the femoral head and the height and diameter of vertebra(L1) of each group were also measured and the number of osteoclasts was determined by Tartrate-resistant acid phosphatase (TRACP) staining. Meanwhile, the expression of alkaline phosphatase (ALP) was evaluated by immunohistochemistry assays. The differences between groups in terms of liver and kidney oxidation-related indexes and serum and urinary indicators related to bone metabolism were also analyzed. Furthermore, qRT-PCR and western blotting were used to evaluate the effect of melatonin on osteogenic and osteoclastic differentiation in MC3T3-E1 and RAW264.7 cells, respectively. RESULTS: RA induction led to a decrease in the amount and density of trabecular bone, a decrease in the length and diameter of the femur and height, diameter of the vertebra (L1), a decrease in bone mass and density and the expression of ALP, and an increase in the number of osteoclasts. Melatonin treatment alleviated these effects induced by RA, increasing the amount of trabecular bone in OP mice, improving the microstructure of the femur and vertebra(L1) and increasing bone mass bone density and the expression of ALP, as well as decreasing the number of osteoclasts. Additionally, blood and urinary bone metabolism-related indicators showed that melatonin promoted bone formation and inhibited bone resorption. Determination of oxidant and antioxidant biomarkers in the livers and kidneys of the mice revealed that melatonin promoted the antioxidant level and suppressed the level of oxidant molecules in these organs. In vitro, RA promoted osteoclasts and inhibit osteogenesis by increasing oxidative stress levels in the RAW264.7 and MC3T3-E1 cells, but melatonin reversed this effect. Melatonin may, therefore, play a role in the ERK/SMAD and NF-κB pathways. CONCLUSIONS: Melatonin can alleviate bone loss in RA-induced OP model mice, repair the trabecular microstructure, and promote bone formation. These effects may be related to reducing oxidation levels in vivo and vitro through the ERK/SMAD and NF-κB pathways.

MTNR1B loss promotes chordoma recurrence by abrogating melatonin-mediated ß-catenin signaling repression.

Chordoma is an extremely rare malignant bone tumor with a high rate of relapse. While cancer stem cells (CSCs) are closely associated with tumor recurrence, which depend on its capacity to self-renew and induce chemo-/radioresistance, whether and how CSCs participate in chordoma recurrence remains unclear. The current study found that tumor cells in recurrent chordoma displayed more dedifferentiated CSC-like properties than those in corresponding primary tumor tissues. Meanwhile, MTNR1B deletion along with melatonin receptor 1B (MTNR1B) down-regulation was observed in recurrent chordoma. Further investigation revealed that activation of Gαi2 by MTNR1B upon melatonin stimulation could inhibit SRC kinase activity via recruiting CSK and SRC, increasing SRC Y530 phosphorylation, and decreasing SRC Y419 phosphorylation. This subsequently suppressed ß-catenin signaling and stemness via decreasing ß-catenin p-Y86/Y333/Y654. However, MTNR1B loss in chordoma mediated increased CSC properties, chemoresistance, and tumor progression by releasing melatonin's repression of ß-catenin signaling. Clinically, MTNR1B deletion was found to correlate with patients' survival. Together, our study establishes a novel convergence between melatonin and ß-catenin signaling pathways and reveals the significance of this cross talk in chordoma recurrence. Besides, we propose that MTNR1B is a potential biomarker for prediction of chordoma prognosis and selection of treatment options, and chordoma patients might benefit from targeting MTNR1B/Gαi2/SRC/ß-catenin axis.

Melatonin-mediated miR-526b-3p and miR-590-5p upregulation promotes chondrogenic differentiation of human mesenchymal stem cells.

Bone marrow-derived mesenchymal stem cells (BMSCs), with inherent chondrogenic differentiation potential appear to be ideally suited for therapeutic use in cartilage regeneration. Accumulating evidence has demonstrated that melatonin can promote chondrogenic differentiation in human BMSCs. However, little is known about the mechanism. MicroRNAs (miRNAs) have been shown to regulate the differentiation of BMSCs, but their roles in melatonin-promoted chondrogenic differentiation have not been characterized. Here, we demonstrate that melatonin promoted chondrogenic differentiation of human BMSCs via upregulation of miR-526b-3p and miR-590-5p. Mechanistically, the elevated miR-526b-3p and miR-590-5p enhanced SMAD1 phosphorylation by targeting SMAD7. Additionally, administration of miR-526b-3p mimics or miR-590-5p mimics successfully promoted the chondrogenic differentiation of human BMSCs. Collectively, our study suggests that modification of BMSCs using melatonin or miRNA transduction could be an effective therapy for cartilage damage and degeneration.

Rare coding variants in MAPK7 predispose to adolescent idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is a complex genetic disorder characterized by three-dimensional spinal curvatures, affecting 2%-3% of school age children, yet the causes underlying AIS are not well understood. Here, we first conducted a whole-exome sequencing and linkage analysis on a three-generation Chinese family with autosomal-dominant (AD) AIS, and then performed targeted sequencing in a discovery cohort comprising 20 AD AIS families and 86 simplex patients, and finally identified three disease-associated missense variants (c.886G> A, c.1943C> T, and c.1760C> T) in the MAPK7 gene (encoding mitogen-activated protein kinase 7). Genotyping of the three rare variants in a Chinese replication cohort comprising 1,038 simplex patients and 1,841 controls showed that their combined allele frequency was significantly over-represented in patients as compared with controls (2.0% [41/2,076] vs. 0.7% [27/3,682]; odds ratio = 2.7; P = 2.8 × 10-5 ). In vitro, we demonstrated that the three MAPK7 mutants disrupted nuclear translocation in cellular models, which is necessary for the normal function of MAPK7. In vivo, we also conducted CRISPR/Cas9-mediated deletion of mapk7 in zebrafish recapitulating the characteristic phenotype of idiopathic scoliosis. Taken together, our findings suggest that rare coding variants in MAPK7 predispose to AIS, providing clues to understanding the mechanisms of AIS.

Melatonin reversed tumor necrosis factor-alpha-inhibited osteogenesis of human mesenchymal stem cells by stabilizing SMAD1 protein.

Tumor necrosis factor-alpha (TNFα) plays a pivotal role in inflammation-related osteoporosis through the promotion of bone resorption and suppression of bone formation. Numerous drugs have been produced to treat osteoporosis by inhibiting bone resorption, but they offer few benefits to bone formation, which is what is needed by patients with severe bone loss. Melatonin, which can exert both anti-inflammatory and pro-osteogenic effects, shows promise in overcoming TNFα-inhibited osteogenesis and deserves further research. This study demonstrated that melatonin rescued TNFα-inhibited osteogenesis of human mesenchymal stem cells and that the interactions between SMURF1 and SMAD1 mediated the crosstalk between melatonin signaling and TNFα signaling. Additionally, melatonin treatment was found to downregulate TNFα-induced SMURF1 expression and then decrease SMURF1-mediated ubiquitination and degradation of SMAD1 protein, leading to steady bone morphogenetic protein-SMAD1 signaling activity and restoration of TNFα-impaired osteogenesis. Thus, melatonin has prospects for treating osteoporosis caused by inflammatory factors due to its multifaceted functions on regulation of bone formation, bone resorption, and inflammation. Further studies will focus on unveiling the specific mechanisms by which melatonin downregulates SMURF1 expression and confirming the clinical therapeutic value of melatonin in the prevention and therapy of bone loss associated with inflammation.

Interspinous spacers versus posterior lumbar interbody fusion for degenerative lumbar spinal diseases: a meta-analysis of prospective studies.

PURPOSE: Our aim is to evaluate the safety and effectiveness of interspinous spacers versus posterior lumbar interbody fusion (PLIF) for degenerative lumbar spinal diseases. METHODS: A comprehensive literature search was performed using PubMed, Web of Science and Cochrane Library through September 2015. Included studies were performed according to eligibility criteria. Data of complication rate, post-operative back visual analogue scale (VAS) score, Oswestry Disability Index (ODI) score, estimated blood loss (EBL), operative time, length of hospital stay (LOS), range of motion (ROM) at the surgical, proximal and distal segments were extracted and analyzed. RESULTS: Ten studies were selected from 177 citations. The pooled data demonstrated the interspinous spacers group had a lower estimated blood loss (weighted mean difference [WMD]: -175.66 ml; 95 % confidence interval [CI], -241.03 to -110.30; p < 0.00001), shorter operative time (WMD: -55.47 min; 95%CI, -74.29 to -36.65; p < 0.00001), larger range of motion (ROM) at the surgical segment (WMD: 3.97 degree; 95%CI, -3.24 to -1.91; p < 0.00001) and more limited ROM at the proximal segment (WMD: -2.58 degree; 95%CI, 2.48 to 5.47; p < 0.00001) after operation. Post-operative back VAS score, ODI score, length of hospital stay, complication rate and ROM at the distal segment showed no difference between the two groups. CONCLUSIONS: Our meta-analysis suggested that interspinous spacers appear to be a safe and effective alternative to PLIF for selective patients with degenerative lumbar spinal diseases. However, more randomized controlled trials (RCT) are still needed to further confirm our results.

Multifunctional Composite Scaffold with Nanosilver, Graphene Oxide, and Macrophage Membrane Vesicles for Sequential Treatment of Infected Bone Defects.

The management of infected bone defects poses a significant clinical challenge, and current treatment modalities exhibit various limitations. This study focuses on the development of a multifunctional composite scaffold comprising nanohydroxyapatite/polyethyleneglycol diacrylate matrix, silver nanoparticles, graphene oxide (GO), sodium alginate, and M2-type macrophage membrane vesicles (MVs) to enhance the healing of infected bone defects. The composite scaffold demonstrates several key features: first, it releases sufficient quantities of silver ions to effectively eliminate bacteria; second, the controlled release of MVs leads to a notable increase in M2-type macrophages, thereby significantly mitigating the inflammatory response. Additionally, GO acts synergistically with nanohydroxyapatite to enhance osteoinductive activity, thereby fostering bone regeneration. Through meticulous in vitro and in vivo investigations, the composite scaffold exhibits broad-spectrum antimicrobial effects, robust immunomodulatory capabilities, and enhanced osteoinductive activity. This multifaceted composite scaffold presents a promising approach for the sequential treatment of infected bone defects, addressing the antimicrobial, immunomodulatory, and osteogenic aspects. This study introduces innovative perspectives and offers new and effective treatment alternatives for managing infected bone defects.

LncRNA DGCR5-encoded polypeptide RIP aggravates SONFH by repressing nuclear localization of ß-catenin in BMSCs.

The differentiation fate of bone marrow mesenchymal stem cells (BMSCs) affects the progression of steroid-induced osteonecrosis of the femoral head (SONFH). We find that lncRNA DGCR5 encodes a 102-amino acid polypeptide, RIP (Rac1 inactivated peptide), which promotes the adipogenic differentiation of BMSCs and aggravates the progression of SONFH. RIP, instead of lncRNA DGCR5, binds to the N-terminal motif of RAC1, and inactivates the RAC1/PAK1 cascade, resulting in decreased Ser675 phosphorylation of ß-catenin. Ultimately, the nuclear localization of ß-catenin decreases, and the differentiation balance of BMSCs tilts toward the adipogenesis lineage. In the femoral head of rats, overexpression of RIP causes trabecular bone disorder and adipocyte accumulation, which can be rescued by overexpressing RAC1. This finding expands the regulatory role of lncRNAs in BMSCs and suggests RIP as a potential therapeutic target.

Corrigendum to "Melatonin Reverses the Loss of Stemness Induced by TNF-α in Human Bone Marrow Mesenchymal Stem Cells through Upregulation of YAP Expression".

[This corrects the article DOI: 10.1155/2019/6568394.].

Pyridine Detection Using Supramolecular Organic Frameworks Incorporating Cucurbit[10]uril.

A physical impregnation method is presented in this study, providing a facile approach to encapsulating functional guest molecules (GMs) into robust crystalline supramolecular organic frameworks incorporating cucurbit[10]uril (Q[10]-SOF). As Q[10]-SOF has high evaporated pyridine affinity under normal atmospheric pressure, pyridine molecules in this method were successfully encapsulated into the nanospace formed by GMs and Q[10]-SOF while retaining their crystal framework, morphology, and high stability. GMs@Q[10]-SOF solid materials were found to respond to pyridine, being suitable to be used as solid sensors. Notably, Q[10]-SOF loading with pyrene exhibited a unique response to pyridine along with dramatic fluorescence quenching; loading with dansyl chloride exhibited a unique response to pyridine along with significant fluorescence enhancement, having a quick response within 60 s. Our findings represent a critical advancement in the design of pyridine detection and adsorption for commercial gas identification and sensing.

Exosomal miR-100-5p inhibits osteogenesis of hBMSCs and angiogenesis of HUVECs by suppressing the BMPR2/Smad1/5/9 signalling pathway.

BACKGROUND: Nontraumatic osteonecrosis of the femoral head (NONFH) is a common, progressive, and refractory orthopaedic disease. Decreased osteogenesis and angiogenesis are considered the main factors in the pathogenesis of NONFH. We aimed to figure out whether exosomes and exosomal miRNA from necrotic bone tissues of patients with NONFH are involved in the pathogenesis of NONFH and reveal the underlying mechanisms. METHODS: RT-PCR and western blotting (WB) were used to detect the expression of osteogenic, adipogenic, and angiogenic markers. ALP staining and Alizarin Red S (ARS) staining were used to evaluate osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBMSCs). Oil Red O staining was performed to assess the adipocyte deposition. A tube formation assay was used to study angiogenesis of human umbilical vascular endothelial cells (HUVECs). H&E staining and immunohistochemistry (IHC) staining were used to detect the effect of the NONFH exosomes in vivo. MicroRNA sequencing was conducted to identify potential regulators in the NONFH exosomes. The target relationship between miR-100-5p and BMPR2 was predicted and confirmed by a dual luciferase reporter assay and WB. RESULTS: The NONFH exosomes reduced the osteogenic differentiation of hBMSCs and angiogenesis of HUVECs. In addition, the injection of the NONFH exosomes caused thinning and disruption of bone trabeculae in the femoral heads of rats. MiR-100-5p expression was upregulated in the NONFH exosomes and inhibited the osteogenesis of hBMSCs and angiogenesis of HUVECs by targeting BMPR2 and suppressing the BMPR2/SMAD1/5/9 signalling pathway. Silencing miR-100-5p expression rescued the reduction in osteogenesis and angiogenesis caused by the NONFH exosomes by activating the BMPR2/SMAD1/5/9 signalling pathway. CONCLUSION: The NONFH exosomal miR-100-5p can lead to NONFH-like damage by targeting BMPR2 and suppressing the BMPR2/SMAD1/5/9 signalling pathway, which may be involved in the pathophysiological mechanisms of nontraumatic osteonecrosis of the femoral head (NONFH).

Targeting miR-18a sensitizes chondrocytes to anticytokine therapy to prevent osteoarthritis progression.

Inflammation participates in the development of OA and targeting inflammatory signaling pathways is a potential strategy for OA treatment. IL-1ß is one of the most important inflammatory factors to trigger the activation of NF-κB signaling and accelerate OA progression, whereas OA patients could hardly benefit from inhibiting IL-1ß in clinic, suggesting the importance to further explore the details of OA inflammation. We here showed that expression of miR-18a in chondrocytes was specifically induced in response to IL-1ß in vitro as well as in rat model of OA during which NF-κB signaling was involved, and that nuclear-translocated p65 directly upregulated miR-18a expression at transcriptional level. Further, increased miR-18a mediated hypertrophy of chondrocytes, resulting in OA degeneration, by targeting TGFß1, SMAD2, and SMAD3 and subsequently leading to repression of TGF-ß signaling. And the level of serum miR-18a was positively correlated to severity of OA. Interestingly, other than IL-1ß, pro-inflammation cytokines involving TNFα could also remarkably upregulate miR-18a via activating NF-κB signaling and subsequently induce chondrocytes hypertrophy, suggesting a pivotal central role of miR-18a in inflammatory OA progression. Thus, our study revealed a novel convergence of NF-κB and TGF-ß signaling mediated by miR-18a, and a novel mechanism underlying inflammation-regulated OA dependent of NF-κB/miR-18a/TGF-ß axis. Notably, in vivo assay showed that targeting miR-18a sensitized OA chondrocytes to IL-1ß inhibitor as targeting IL-1ß and miR-18a simultaneously had much stronger inhibitory effects on OA progression than suppressing IL-1ß alone. Therefore, the diagnostic and therapeutic potentials of miR-18a for OA were also revealed.

Collagen type II suppresses articular chondrocyte hypertrophy and osteoarthritis progression by promoting integrin ß1-SMAD1 interaction.

Hypertrophic differentiation is not only the terminal process of endochondral ossification in the growth plate but is also an important pathological change in osteoarthritic cartilage. Collagen type II (COL2A1) was previously considered to be only a structural component of the cartilage matrix, but recently, it has been revealed to be an extracellular signaling molecule that can significantly suppress chondrocyte hypertrophy. However, the mechanisms by which COL2A1 regulates hypertrophic differentiation remain unclear. In our study, a Col2a1 p.Gly1170Ser mutant mouse model was constructed, and Col2a1 loss was demonstrated in homozygotes. Loss of Col2a1 was found to accelerate chondrocyte hypertrophy through the bone morphogenetic protein (BMP)-SMAD1 pathway. Upon interacting with COL2A1, integrin ß1 (ITGB1), the major receptor for COL2A1, competed with BMP receptors for binding to SMAD1 and then inhibited SMAD1 activation and nuclear import. COL2A1 could also activate ITGB1-induced ERK1/2 phosphorylation and, through ERK1/2-SMAD1 interaction, it further repressed SMAD1 activation, thus inhibiting BMP-SMAD1-mediated chondrocyte hypertrophy. Moreover, COL2A1 expression was downregulated, while chondrocyte hypertrophic markers and BMP-SMAD1 signaling activity were upregulated in degenerative human articular cartilage. Our study reveals novel mechanisms for the inhibition of chondrocyte hypertrophy by COL2A1 and suggests that the degradation and decrease in COL2A1 might initiate and promote osteoarthritis progression.

Melatonin Reverses the Loss of Stemness Induced by TNF-α in Human Bone Marrow Mesenchymal Stem Cells through Upregulation of YAP Expression.

Mesenchymal stem cells (MSCs) are promising candidates for tissue regeneration and disease treatment. However, long-term in vitro culture results in loss of MSC stemness. The inflammation that occurs at stem cell transplant sites (such as that resulting from TNF-α) is a contributing factor for stem cell treatment failure. Currently, there is little evidence regarding the protective role of melatonin with regard to the negative effects of TNF-α on the stemness of MSCs. In this study, we report a melatonin-based method to reduce the inflammatory effects on the stemness of bone marrow mesenchymal stem cells (BMMSCs). The results of colony formation assays, Alizarin red staining, western blotting, and reverse transcription-polymerase chain reactions suggest that melatonin can reverse the inflammatory damage caused by TNF-α treatment in the third, seventh, and tenth generations of primary BMMSCs (vs. control and the TNF-α-treated group). Meanwhile, a detailed analysis of the molecular mechanisms showed that the melatonin receptor and YAP signaling pathway are closely related to the role that melatonin plays in negative inflammatory effects against BMMSCs. In addition, in vivo experiments showed that melatonin could reverse the damage caused by TNF-α on bone regeneration by BMMSCs in nude mice. Overall, our results suggest that melatonin can reverse the loss of stemness caused by inflammatory factor TNF-α in BMMSCs. Our results also provide a practical strategy for the application of BMMSCs in tissue engineering and cell therapy.