SATB2-Nanog axis links age-related intrinsic changes of mesenchymal stem cells from craniofacial bone

Regulation Mechanisms and Maintenance Strategies of Stemness in Mesenchymal Stem Cells

Stemness pertains to the intrinsic ability of mesenchymal stem cells (MSCs) to undergo self-renewal and differentiate into multiple lineages, while simultaneously impeding their differentiation and preserving crucial differentiating genes in a state of quiescence and equilibrium. Owing to their favorable attributes, including uncomplicated isolation protocols, ethical compliance, and ease of procurement, MSCs have become a focal point of inquiry in the domains of regenerative medicine and tissue engineering. As age increases or ex vivo cultivation is prolonged, the functionality of MSCs decreases and their stemness gradually diminishes, thereby limiting their potential therapeutic applications. Despite the existence of several uncertainties surrounding the comprehension of MSC stemness, considerable advancements have been achieved in the clarification of the potential mechanisms that lead to stemness loss, as well as the associated strategies for stemness maintenance. This comprehensive review provides a systematic overview of the factors influencing the preservation of MSC stemness, the molecular mechanisms governing it, the strategies for its maintenance, and the therapeutic potential associated with stemness. Finally, we underscore the obstacles and prospective avenues in present investigations, providing innovative perspectives and opportunities for the preservation and therapeutic utilization of MSC stemness.

Mesenchymal stem cells and dental implant osseointegration during aging: from mechanisms to therapy

Dental implants are widely used to replace missing teeth, providing patients with unparalleled levels of effectiveness, convenience, and affordability. The biological basis for the clinical success of dental implants is osseointegration. Bone aging is a high-risk factor for the reduced osseointegration and survival rates of dental implants. In aged individuals, mesenchymal stem cells (MSCs) in the bone marrow show imbalanced differentiation with a reduction in osteogenesis and an increase in adipogenesis. This leads to impaired osseointegration and implant failure. This review focuses on the molecular mechanisms underlying the dysfunctional differentiation of aged MSCs, which primarily include autophagy, transcription factors, extracellular vesicle secretion, signaling pathways, epigenetic modifications, microRNAs, and oxidative stress. Furthermore, this review addresses the pathological changes in MSCs that affect osseointegration and discusses potential therapeutic interventions to enhance osseointegration by manipulating the mechanisms underlying MSC aging.

Exosomes derived from mesenchymal stromal cells promote bone regeneration by delivering miR-182-5p-inhibitor

Exosomes, small extracellular vesicles that function as a key regulator of cell-to-cell communication, are emerging as a promising candidate for bone regeneration. Here, we aimed to investigate the effect of exosomes from pre-differentiated human alveolar bone-derived bone marrow mesenchymal stromal cells (AB-BMSCs) carrying specific microRNAs on bone regeneration. Exosomes secreted from AB-BMSCs pre-differentiated for 0 and 7 days were cocultured with BMSCs in vitro to investigate their effect on the differentiation of the BMSCs. MiRNAs from AB-BMSCs at different stages of osteogenic differentiation were analyzed. BMSCs seeded on poly-L-lactic acid(PLLA) scaffolds were treated with miRNA antagonist-decorated exosomes to verify their effect on new bone regeneration. Exosomes pre-differentiated for 7 days effectively promoted the differentiation of BMSCs. Bioinformatic analysis revealed that miRNAs within the exosomes were differentially expressed, including the upregulation of osteogenic miRNAs (miR-3182, miR-1468) and downregulation of anti-osteogenic miRNAs (miR-182-5p, miR-335-3p, miR-382-5p), causing activation of the PI3K/Akt signaling pathway. The treatment of BMSC-seeded scaffolds with anti-miR-182-5p decorated exosomes demonstrated enhanced osteogenic differentiation and efficient formation of new bone. In conclusion, Osteogenic exosomes secreted from pre-differentiated AB-BMSCs were identified and the gene modification of exosomes provides great potential as a bone regeneration strategy. DATA AVAILABILITY STATEMENT: Data generated or analyzed in this paper partly are available in the GEO public data repository(http://www.ncbi.nlm.nih.gov/geo).

Multifunctional exosomes derived from bone marrow stem cells for fulfilled osseointegration

Bone marrow mesenchymal stem cells (BMSCs) have self-renewal, multi-directional differentiation potential, and immune regulation function and are widely used for de novo bone formation. However, the wide variation in individual amplification, the potential risk of cancer cell contamination, and the need for culture time significantly limit their widespread use clinically. Alternatively, numerous studies have shown that exosomes secreted by BMSCs in the nanoscale can also affect the functionality of endothelial cells (angiogenesis), macrophages (immunomodulation), and osteoblasts/osteoclasts (osteogenesis), which is a highly promising therapy for osseointegration with pronounced advantages (e.g., safety, high efficiency, and no ethical restrictions). The review aims to summarize the multifaceted effect of BMSCs-derived exosomes on osseointegration and provide reference and basis for rapid and qualified osseointegration.

The Emerging Role of Non-Coding RNAs in Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

Autologous bone marrow-derived mesenchymal stem cells (BMSCs) are more easily available and frequently used for bone regeneration in clinics. Osteogenic differentiation of BMSCs involves complex regulatory networks affecting bone formation phenomena. Non-coding RNAs (ncRNAs) refer to RNAs that do not encode proteins, mainly including microRNAs, long non-coding RNAs, circular RNAs, piwi-interacting RNAs, transfer RNA-derived small RNAs, etc. Recent in vitro and in vivo studies had revealed the regulatory role of ncRNAs in osteogenic differentiation of BMSCs. NcRNAs had both stimulatory and inhibitory effects on osteogenic differentiation of BMSCs. During the physiological condition, osteo-stimulatory ncRNAs are upregulated and osteo-inhibitory ncRNAs are downregulated. The opposite effects might occur during bone degenerative disease conditions. Intracellular ncRNAs and ncRNAs from neighboring cells delivered via exosomes participate in the regulatory process of osteogenic differentiation of BMSCs. In this review, we summarize the recent advances in the regulatory role of ncRNAs on osteogenic differentiation of BMSCs during physiological and pathological conditions. We also discuss the prospects of the application of modulation of ncRNAs function in BMSCs to promote bone tissue regeneration in clinics.

Roles of extracellular vesicles in the aging microenvironment and age-related diseases

Cellular senescence is a persistently hypoproliferative state with diverse stressors in a specific aging microenvironment. Senescent cells have a double-edged sword effect: they can be physiologically beneficial for tissue repair, organ growth, and body homeostasis, and they can be pathologically harmful in age-related diseases. Among the hallmarks of senescence, the SASP, especially SASP-related extracellular vesicle (EV) signalling, plays the leading role in aging transmission via paracrine and endocrine mechanisms. EVs are successful in intercellular and interorgan communication in the aging microenvironment and age-related diseases. They have detrimental effects on downstream targets at the levels of immunity, inflammation, gene expression, and metabolism. Furthermore, EVs obtained from different donors are also promising materials and tools for antiaging treatments and are used for regeneration and rejuvenation in cell-free systems. Here, we describe the characteristics of cellular senescence and the aging microenvironment, concentrating on the production and function of EVs in age-related diseases, and provide new ideas for antiaging therapy with EVs.

An arthroscopic technique for closure of perforations in temporomandibular joint retrodiscal tissues

The objective of this retrospective study was to introduce and evaluate an arthroscopic discopexy for closure of retrodiscal tissue perforations. A total of 112 patients (135 joints) receiving an arthroscopic discopexy for management of retrodiscal tissue perforations between January 2016 and September 2019 were included. Pre- and postoperative visual analogue scale (VAS) pain scores and maximum inter-incisal opening (MIO), as well as magnetic resonance imaging (MRI) data, were collected and analysed. Success was recorded when the disc position was >11 o'clock, VAS pain score <3, and MIO>25 mm. For patients with a condyle deformity, postoperative bone remodelling was also recorded. The VAS pain score decreased from 3.04 ± 2.66 preoperatively to 0.88 ± 1.13 at 12 months postoperatively (P < 0.001) and MIO increased from 33.90 ± 7.39 mm to 35.19 ± 6.14 mm (P = 0.029). MRI evaluation revealed that 133 discs were successfully repositioned back on top of the condyle. Among these, 11 joints were associated with either VAS pain score ≥3 or MIO ≤25 mm. Therefore, a success rate of 90.4% (122/135) was achieved at 12 months postoperative. Bone remodelling was detected in 72 joints. Arthroscopic discopexy is a minimally invasive and effective treatment for retrodiscal tissue perforations that achieves the purpose of simultaneously restoring the intra-articular structures and relieving clinical symptoms.

The Effects of MiR-320 on the Proliferation and Differentiation of Human Alveolar Bone-Derived Mesenchymal Stem Cells

Alveolar bone-derived mesenchymal stem cells (AB-BMSCs) have a biological morphology and antigen phenotype similar to those of BMSCs. However, the intrinsic characteristics of AB-BMSCs and their underlying mechanisms, in which the involvement of micro(mi)RNAs has been reported, remain unknown. This study shows that miR-320c expression was significantly suppressed during osteoblastic differentiation of human AB-BMSCs. The overexpression of miR-320c markedly decreased cellular proliferation, intracellular activity of alkaline phosphatase (ALP) and formation of calcium nodules; mRNA levels of osteogenesis-related genes were significantly reduced compared to those in control cells. Calcium nodule formation in miR-320c-knockdown cells was significantly increased, and HOXA10, Runx2, and BGP mRNA levels were significantly increased compared to those in control cells. These results indicate that miR-320c suppresss the proliferation and osteogenic differentiation of AB-BMSCs, in part by decreasing ALP activity, cellular proliferation, mineralization, and expression of several osteogenesis-related genes. These results lay the basic foundation for the elucidation of the molecular mechanisms of alveolar bone reconstruction.

SATB2 induction of a neural crest mesenchyme-like program drives melanoma invasion and drug resistance

Recent genomic and scRNA-seq analyses of melanoma demonstrated a lack of recurrent genetic drivers of metastasis, while identifying common transcriptional states correlating with invasion or drug resistance. To test whether transcriptional adaptation can drive melanoma progression, we made use of a zebrafish mitfa:BRAFV600E;tp53-/- model, in which malignant progression is characterized by minimal genetic evolution. We undertook an overexpression-screen of 80 epigenetic/transcriptional regulators and found neural crest-mesenchyme developmental regulator SATB2 to accelerate aggressive melanoma development. Its overexpression induces invadopodia formation and invasion in zebrafish tumors and human melanoma cell lines. SATB2 binds and activates neural crest-regulators, including pdgfab and snai2. The transcriptional program induced by SATB2 overlaps with known MITF^lowAXL^high and AQP1⁺NGFR1^high drug-resistant states and functionally drives enhanced tumor propagation and resistance to Vemurafenib in vivo. In summary, we show that melanoma transcriptional rewiring by SATB2 to a neural crest mesenchyme-like program can drive invasion and drug resistance in autochthonous tumors.

MicroRNA-31 regulates dental epithelial cell proliferation by targeting Satb2

MicroRNAs (miRNAs) exhibit strong potential clinical application owing to their extensive regulation and flexible delivery properties. MicroRNA-31 (miR-31) is an evolutionarily conserved miRNA expressed during tooth development, and it is highly expressed in mouse incisor epithelium. The specific role of miR-31 in odontogenesis has not been elucidated comprehensively, and the aim of the present study was to investigate its activity. Our results showed that miR-31 suppressed LS8 cell proliferation by inhibiting the cell cycle at the G1/S transition. Mutation of Special AT-rich sequence-binding protein 2 (SATB2) gene is responsible for human SATB2-associated syndrome (SAS), which is often accompanied by dental abnormities. Here, it was identified as a direct target of miR-31 in LS8 cells and a promoter of cell proliferation. The expression and distribution of SATB2 in mouse molars and incisors were explored using immunofluorescence, which showed strong signals in the nuclei of incisor epithelial cells and weak signals in the cytoplasm of molar epithelial cells. Moreover, rescue experiments demonstrated that Satb2 could mitigate the inhibitory effect of miR-31 on cell proliferation by promoting the expression of CDK4. Collectively, our results suggested that miR-31 regulates dental epithelial cell proliferation by targeting Satb2, highlighting the biological importance of miR-31 in odontogenesis.

Insulin impedes osteogenesis of BMSCs by inhibiting autophagy and promoting premature senescence via the TGF-β1 pathway

The dysfunction of bone marrow stromal cells (BMSCs) may be a core factor in Type 2 diabetes mellitus (T2DM) associated osteoporosis. However, the underlying mechanism is not well understood. Here, we delineated the critical role of insulin impeding osteogenesis of BMSCs in T2DM. Compared with BMSCs from healthy people (H-BMSCs), BMSCs from T2DM patient (DM-BMSCs) showed decreased osteogenic differentiation and autophagy level, and increased senescent phenotype. H-BMSCs incubated in hyperglycemic and hyperinsulinemic conditions similarly showed these phenotypes of DM-BMSCs. Notably, enhanced TGF-β1 expression was detected not only in DM-BMSCs and high-glucose and insulin-treated H-BMSCs, but also in bone callus of streptozocin-induced diabetic rats. Moreover, inhibiting TGF-β1 signaling not only enhanced osteogenic differentiation and autophagy level of DM-BMSCs, but also delayed senescence of DM-BMSCs, as well as promoted mandible defect healing of diabetic rats. Finally, we further verified that it was TGF-β receptor II (TβRII), not TβRI, markedly increased in both DM-BMSCs and insulin-treated H-BMSCs. Our data revealed that insulin impeded osteogenesis of BMSCs by inhibiting autophagy and promoting premature senescence, which it should be responsible for T2DM-induced bone loss, at least in part. These findings suggest that inhibiting TGF-β1 pathway may be a potential therapeutic target for T2DM associated bone disorders.

Age-dependent role of SIRT6 in jawbone via regulating senescence and autophagy of bone marrow stromal cells

Age-related jawbone loss directly impact the function of oral cavity resulted from tooth loss, implant failure, and jaw fracture. Numerous evidences show that age-related senescence of bone marrow stromal cells (BMSCs) play a critical role in bone loss, but little attention has been paid to jawbone. Here, we delineated the critical role of sirtuin family protein 6 (SIRT6) in senescence, autophagy, and osteogenesis of BMSCs from jawbones. Radiography analysis showed less jawbone quality in elderly than young people. We also showed that SIRT6 expression decreased in bone tissue and BMSCs from the elderly by immunochemical staining. BMSCs from the elderly exhibited decreased osteogenic differentiation and inclined senescence which these phenotypes could be simulated by SIRT6 knockdown. Furthermore, accompanied with the inhibition of SIRT6, the autophagy level and ostogenesis of BMSCs was also decreased. However, using rapamycin, an autophagy activator, could rescue these adverse effects of BMSCs caused by SIRT6 inhibition. Mechanistically, SIRT6 regulated the autophagy and osteogenesis of BMSCs by activating AKT-mTOR pathway, at least in part. Finally, a decreased jawbone quality was shown in SIRT6 haploinsufficiency mice by Wnt1 specific tissue knockdown (Wnt1-Cre;SIRT6^fl/+) model. Taken together, our data revealed that SIRT6 adjusted senescence and osteogenesis of BMSCs via altering autophagy level, and associated with age-related bone loss. SIRT6 could be as a promising therapeutic target for age-related osteoporosis of jawbone.

microRNA-31 inhibition partially ameliorates the deficiency of bone marrow stromal cells from cleidocranial dysplasia

BACKGROUND

Cleidocranial dysplasia (CCD) in humans is an autosomal-dominant skeletal dysplasia caused by heterozygous mutations of the runt-related transcription factor 2 (RUNX2) and significantly increases the risk of osteoporosis. Increasing evidence demonstrates that the dysfunction of bone marrow stromal cells from CCD patients (BMSCs-CCD) contributes to the bone deficiency, but the characteristics of BMSCs-CCD and the mechanisms that underlie their properties remain undefined.

METHODS

The clinical manifestations of three CCD patients were collected and the mutations of RUNX2 were analyzed. The properties of proliferation, osteogenesis, stemness, and senescence of BMSCs-CCD were compared with that of BMSCs from healthy donors. The expression of microRNA-31 ( miR-31) between BMSCs-CCD and BMSCs was measured and lentivirus-carried miR-31 inhibitor was used to determine the role of miR-31 in BMSCs-CCD both in vitro and in vivo. The molecular mechanisms underlying RUNX2-miR31 and miR-31 targeting stemness and senescence of BMSCs-CCD were also explored.

RESULTS

We identified two mutation sites of RUNX2 via exome sequencing from 2 of 3 Chinese CCD patients with typical clinical presentations. Compared with BMSCs from healthy donors, BMSCs-CCD displayed significantly attenuated proliferation, osteogenesis and stemness, and enhanced senescence. Meanwhile, miR-31 knockdown could ameliorate these deficiency phenotypes of BMSCs-CCD by regulating SATB2, BMI1, CDKN, and SP7. Mechanistically, RUNX2 directly repressed miR-31 expression, and therefore RUNX2 haploinsufficiency in CCD leading to miR-31 upregulation contributed to the deficiency of BMSCs-CCD. miR-31 inhibition in BMSCs-CCD showed enhanced osteogenesis through heterotopic subcutaneous implantation in the nude mice.

CONCLUSIONS

Our results show the functional deficiencies of BMSCs-CCD and a potential role of miR-31 in BMSCs-CCD deficiencies. The application of miR-31 inhibitor in BMSCs-CCD might lend hope for developing BMSC-based therapeutic approaches against CCD-associated skeletal diseases.

Decrease of MiR-31 induced by TNF-α inhibitor activates SATB2/RUNX2 pathway and promotes osteogenic differentiation in ethanol-induced osteonecrosis

PURPOSE

Suppressed osteogenic differentiation is considered a main cause of ethanol-induced osteonecrosis. Tumor necrosis factor α (TNF-α) and miR-31 have been reported to be involved in the osteogenic induction. This study aimed to explore a possible molecular mechanism regulating osteogenic differentiation in ethanol-induced osteonecrosis bone marrow stromal stem cells (BMSCs).

METHODS

Alizarin red staining was used to examine the level of mineralization in osteogenic differentiation process. Alkaline phosphatase assay was applied to the validation of ALP level which was essential to bone mineralization. The level of osteogenesis markers was determined by western blot assay, whereas the fluctuations of messenger RNA levels were tested by quantitative real-time polymerase chain reaction. Microarray analysis was conducted to identify differentially expressed genes, because the possible target relationship was predicted and validated by miRBase and luciferase reporter assay, respectively. Colony forming unit of fibroblast assay was used to observe the proliferation of BMSCs.

RESULTS

BMSCs from patients with ethanol-induced osteonecrosis exhibited weaker osteogenic differentiation and proliferation abilities. TNF-α inhibitor added in the osteogenic medium significantly enhanced the osteogenic differentiation ability and BMSCs proliferation ability. TNF-α by regulating miR-31 downregulated the expressions of RUNX2 and SATB2, two contributors of osteoblast differentiation, further suppressed osteogenic differentiation. On the contrary, TNF-α inhibitor could promote osteogenic differentiation in BMSCs from patients with ethanol-induced osteonecrosis.

CONCLUSION

TNF-α inhibitor could downregulate miR-31 expressions, which directly promoted SATB2 and RUNX2 expressions and enhanced osteogenic differentiation of BMSCs from patients with ethanol-induced osteonecrosis.

MicroRNA-31a-5p from aging BMSCs links bone formation and resorption in the aged bone marrow microenvironment

The alteration of age‐related molecules in the bone marrow microenvironment is one of the driving forces in osteoporosis. These molecules inhibit bone formation and promote bone resorption by regulating osteoblastic and osteoclastic activity, contributing to age‐related bone loss. Here, we observed that the level of microRNA‐31a‐5p (miR‐31a‐5p) was significantly increased in bone marrow stromal cells (BMSCs) from aged rats, and these BMSCs demonstrated increased adipogenesis and aging phenotypes as well as decreased osteogenesis and stemness. We used the gain‐of‐function and knockdown approach to delineate the roles of miR‐31a‐5p in osteogenic differentiation by assessing the decrease of special AT‐rich sequence‐binding protein 2 (SATB2) levels and the aging of BMSCs by regulating the decline of E2F2 and recruiting senescence‐associated heterochromatin foci (SAHF). Notably, expression of miR‐31a‐5p, which promotes osteoclastogenesis and bone resorption, was markedly higher in BMSCs‐derived exosomes from aged rats compared to those from young rats, and suppression of exosomal miR‐31a‐5p inhibited the differentiation and function of osteoclasts, as shown by elevated RhoA activity. Moreover, using antagomiR‐31a‐5p, we observed that, in the bone marrow microenvironment, inhibition of miR‐31a‐5p prevented bone loss and decreased the osteoclastic activity of aged rats. Collectively, our results reveal that miR‐31a‐5p acts as a key modulator in the age‐related bone marrow microenvironment by influencing osteoblastic and osteoclastic differentiation and that it may be a potential therapeutic target for age‐related osteoporosis.

A Prognostic Nomogram for Postoperative Bone Remodeling in Patients with ADDWoR

This study aimed to establish an effective prognostic nomogram for predicting the probability of postoperative bone remodeling of patients with anterior disc displacement without reduction (ADDWoR). The nomogram was based on a retrospective study on patients underwent surgical approaches for ADDWoR at Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University from January, 2007 to January, 2017. A multivariate logistic regression analysis was used to develop variables suitable for probability estimation model. The predictive accuracy and discriminative ability were determined by ROC (AUC-index) and calibration curve. Results were validated using bootstrap resampling with all statistical tests two-sided. 1110 patients were included in the analysis. The probability of postoperative bone remodeling in ADDWoR was 0.51. Six independent prognostic factors including age of onset, nocturnal bruxism, disc morphology, BMD, Wilkes’ classification, and postoperative splint therapy were integrated to construct the nomogram. The probability estimation model showed good discrimination in both internal and external validation with AUC-index of 0.84. The calibration curves for probability of postoperative bone remodeling showed optimal agreement with actual observation. In conclusion, a nomogram was established to provide individual prediction of postoperative bone remodeling for patients with ADDWoR treated by arthroscopy surgery.

Estrogen regulates stemness and senescence of bone marrow stromal cells to prevent osteoporosis via ERβ-SATB2 pathway

Decline of pluripotency in bone marrow stromal cells (BMSCs) associated with estrogen deficiency leads to a bone formation defect in osteoporosis. Special AT-rich sequence binding protein 2 (SATB2) is crucial for maintaining stemness and osteogenic differentiation of BMSCs. However, whether SATB2 is involved in estrogen-deficiency associated-osteoporosis is largely unknown. In this study, we found that estrogen mediated pluripotency and senescence of BMSCs, primarily through estrogen receptor beta (ERβ). BMSCs from the OVX rats displayed increased senescence and weaker SATB2 expression, stemness, and osteogenic differentiation, while estrogen could rescue these phenotypes. Inhibition of ERβ or ERα confirmed that SATB2 was associated with ERβ in estrogen-mediated pluripotency and senescence of BMSCs. Furthermore, estrogen mediated the upregulation of SATB2 through the induction of ERβ binding to estrogen response elements (ERE) located at -488 of the SATB2 gene. SATB2 overexpression alleviated senescence and enhanced stemness and osteogenic differentiation of OVX-BMSCs. SATB2-modified BMSCs transplantation could prevent trabecular bone loss in an ovariectomized rat model. Collectively, our study revealed the role of SATB2 in stemness, senescence, and osteogenesis of OVX-BMSCs. These results indicate that estrogen prevents osteoporosis by promoting stemness and osteogenesis, and inhibiting senescence of BMSCs through an ERβ-SATB2 pathway. Therefore, SATB2 is a novel anti-osteoporosis target gene.