The PI3K-Akt pathway regulates calpain 6 expression, proliferation, and apoptosis

Retinoic acid enhances ovarian steroidogenesis by regulating granulosa cell proliferation and MESP2/STAR/CYP11A1 pathway

INTRODUCTION

Ovarian steroidogenesis not only affects the embryonic development and pregnancy outcome, but also associates with many diseases in mammals and women. Exploring the nutrients and mechanisms influencing ovarian steroidogenesis is critical to maintaining the optimal reproductive performance, as well as guaranteeing body health.

OBJECTIVES

This research aimed to explore the effect of retinol metabolism on ovarian steroidogenesis and the underlying mechanisms.

METHODS

Comparative transcriptomic analysis of ovaries from normal and low reproductive performance sows were performed to identify the main causes leading to low fertility. The metabolites regulating steroid hormones synthesis were investigated in ovarian granulosa cells. Gene interference, overexpression, dual-luciferase reporter assays, chromatin immunoprecipitation and transcriptome analysis were further conducted to explore the underlying mechanisms of Aldh1a1 mediating ovarian steroidogenesis.

RESULTS

Transcriptome analysis of ovaries from normal and low reproductive performance sows showed the significant differences in both retinol metabolism and steroid hormones synthesis, indicating retinol metabolism probably influenced steroid hormones synthesis. The related metabolite retinoic acid was furtherly proven a highly active and potent substance strengthening estrogen and progesterone synthesis in ovarian granulosa cells. For the first time, we revealed that retinoic acid synthesis in porcine and human ovarian granulosa cells was dominated by Aldh1a1, and required the assistance of Aldh1a2. Importantly, we demonstrated that Aldh1a1 enhanced the proliferation of ovarian granulosa cells by activating PI3K-Akt-hedgehog signaling pathways. In addition, Aldh1a1 regulated the expression of transcription factor MESP2, which targeted the transcription of Star and Cyp11a1 through binding to corresponding promoter regions.

CONCLUSION

Our data identified Aldh1a1 modulates ovarian steroidogenesis through enhancing granulosa cell proliferation and MESP2/STAR/CYP11A1 pathway. These findings provide valuable clues for improving ovarian health in mammals.

Novel insights into the progression and prognosis of the calpain family members in hepatocellular carcinoma: a comprehensive integrated analysis

Objectives: The goal of our bioinformatics study was to comprehensively analyze the association between the whole calpain family members and the progression and prognosis of hepatocellular carcinoma (HCC). Methods: The data were collected from The Cancer Genome Atlas (TCGA). The landscape of the gene expression, copy number variation (CNV), mutation, and DNA methylation of calpain members were analyzed. Clustering analysis was performed to stratify the calpain-related groups. The least absolute shrinkage and selection operator (LASSO)-based Cox model was used to select hub survival genes. Results: We found 14 out of 16 calpain members expressed differently between tumor and normal tissues of HCC. The clustering analyses revealed high- and low-risk calpain groups which had prognostic difference. We found the high-risk calpain group had higher B cell infiltration and higher expression of immune checkpoint genes HAVCR2, PDCD1, and TIGHT. The CMap analysis found that the histone deacetylase (HDAC) inhibitor trichostatin A and the PI3K-AKT-mTOR pathway inhibitors LY-294002 and wortmannin might have a therapeutic effect on the high-risk calpain group. The DEGs between calpain groups were identified. Subsequent univariate Cox analysis of each DEG and LASSO-based Cox model obtained a calpain-related prognostic signature. The risk score model of this signature showed good ability to predict the overall survival of HCC patients in TCGA datasets and external validation datasets from the Gene Expression Omnibus database and the International Cancer Genome Consortium database. Conclusion: We found that calpain family members were associated with the progression, prognosis, and drug response of HCC. Our results require further studies to confirm.

Advanced glycation end products promote the progression of chronic kidney diseases by targeting calpain 6

Advanced glycation end products (AGEs) are produced by glycosylation or oxidation of proteins and lipids and are tightly involved in the chronic kidney disease (CKD) process. Calpain 6 (CAPN6) is a non-classical calpain that has been reported to be overexpressed in CKD. This study aimed to explore the effects of AGEs in CKD progress and their correlation with CAPN6. AGEs production was measured using ELISA. The CCK-8 assay was used to test cell proliferation. mRNA and protein levels were tested using qRT-PCR and western blot. The progress of glycolysis was tested by calculating the ATP and ECAR content in HK-2 cells. The expression of AGEs and CAPN6 was significantly increased in patients with CKD3, CKD4, and CKD5. AGEs treatment inhibited cell proliferation and glycolysis and accelerated apoptosis. Additionally, CAPN6 knockdown effectively reversed the effects of AGEs in HK-2 cells. In addition, overexpressed CAPN6 played similar role to AGEs, which suppressed cell proliferation and glycolysis and facilitated apoptosis. Moreover, the administration of 2-DG, a glycolysis inhibitor, counteracted the effects of CAPN6 silencing in HK-2 cells. Mechanistically, CAPN6 interacts with NF-κB and PDTC reduced CAPN6 expression in HK-2 cells. This investigation revealed that AGEs facilitate CKD development in vitro by modulating the expression of CAPN6.

The specific phagocytosis regulators could predict recurrence and therapeutic effect in thyroid cancer: A study based on bioinformatics analysis

BACKGROUND

Thyroid cancer (TC) is one of the growing cancers and is prone to recurrence. Meanwhile, in immunotherapy, antibody-dependent cellular phagocytosis (ADCP) phagocytosis related regulators (PRs) play an important role. This study aims to investigate the prognostic value of specific PRs in TC.

METHODS

The purpose of this study was to identify specific PRs in TC patients by retrieving RNA-seq and Clustered Regularly Interspaced Short Palindromic Repeats-cas9 data and an algorithm based on LASSO was used to construct the PRs-signature. Subsequently, prognosis value of PRs-signature for recurrence-free survival (RFS) was explored through various statistical analysis, including Cox regression analysis, Kaplan-Meier analysis, and receiver operating characteristic curve. Additionally, an analysis of immune cell content by risk group was conducted using CIBERSORT, single sample gene set enrichment analysis and MCP-counter algorithms, with a particular focus on the correlation between macrophages and specific PRs.

RESULTS

We identified 36 specific PRs, and a PRs-signature was constructed using 5-prognostic PRs (CAPN6, MUC21, PRDM1, SEL1L3, and CPQ). Receiver operating characteristic analysis showed that predictive power of PRs-signature was decent, and the PRs risk score as an independent prognostic factor was found to be correlated with RFS showed by multivariate cox regression analysis. Meanwhile, a lower RFS was observed in the high-risk group than in the low-risk group. The results of the 3 algorithms suggested that our PRs-signature may have certain significance for macrophage content and ADCP. Interestingly, the low-risk group had higher levels of mRNA expression than the high-risk group at PDCD1, CTLA4, and pro-inflammatory factors from macrophage.

CONCLUSION

For the purpose of prognostic management, this study developed a prediction model. And the cross-talk between certain PRs and TC patients was revealed in this study. Besides, the PRs-signature can predict the immunotherapy response, macrophage content, and ADCP status. TC patients will benefit from these developments by gaining insight into novel therapeutic strategies.

A calpain-6/YAP axis in sarcoma stem cells that drives the outgrowth of tumors and metastases

Sarcomas include cancer stem cells, but how these cells contribute to local and metastatic relapse is largely unknown. We previously showed the pro-tumor functions of calpain-6 in sarcoma stem cells. Here, we use an osteosarcoma cell model, osteosarcoma tissues and transcriptomic data from human tumors to study gene patterns associated with calpain-6 expression or suppression. Calpain-6 modulates the expression of Hippo pathway genes and stabilizes the hippo effector YAP. It also modulates the vesicular trafficking of β-catenin degradation complexes. Calpain-6 expression is associated with genes of the G2M phase of the cell cycle, supports G2M-related YAP activities and up-regulated genes controlling mitosis in sarcoma stem cells and tissues. In mouse models of bone sarcoma, most tumor cells expressed calpain-6 during the early steps of tumor out-growth. YAP inhibition prevented the neoformation of primary tumors and metastases but had no effect on already developed tumors. It could even accelerate lung metastasis associated with large bone tumors by affecting tumor-associated inflammation in the host tissues. Our results highlight a specific mechanism involving YAP transcriptional activity in cancer stem cells that is crucial during the early steps of tumor and metastasis outgrowth and that could be targeted to prevent sarcoma relapse.

Calpain 6 inhibits autophagy in inflammatory environments: A preliminary study on myoblasts and a chronic kidney disease rat model

A non-classical calpain, calpain 6 (CAPN6), can inhibit skeletal muscle differentiation and regeneration. In the present study, the role of CAPN6 in the regulation of the autophagy of myoblasts in vitro was investigated. The underlying molecular events and the CAPN6 level in atrophic skeletal muscle in a rat model of chronic kidney disease (CKD) were also investigated. In vitro, CAPN6 was overexpressed, or knocked down, in rat L6 myoblasts to assess autophagy and related gene expression and co-localization. Subsequently, myoblasts were treated with a mixture of cytokines, and relative gene expression and autophagy were assessed. A rat model of CKD for muscle atrophy was established, and blood chemical level and the expression of CAPN6 in muscle were assessed. The data revealed that the knockdown of CAPN6 in rat myoblasts resulted in increased microtubule-associated protein 1 light chain 3 (LC3) levels, while its overexpression decreased LC3 levels and impaired autophagy. Additionally, it was observed that the co-localization of mammalian target of rapamycin (mTOR) and lysosomal-associated membrane protein 1 (LAMP1), a lysosomal marker, proteins was increased. In addition, mTOR, Raptor and α-tubulin (a marker of microtubules) increased in the CAPN6 overexpression group. However, inflammatory cytokines, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, interferon (INF)-γ and lipopolysaccharides upregulated CAPN6 expression, inhibited L6 myoblast autophagy and stabilized mTOR activity. Furthermore, the animal model successfully mimicked human disease as regards an increase in body weight, and a reduction in muscle mass, cross-sectional area and blood biomarker concentrations; a slight increase in CAPN6 mRNA and protein levels in muscles was observed. Finally, the data of the present study suggested that CAPN6 reduced autophagy via the maintenance of mTOR signaling, which may play a role in CKD-related muscle atrophy. However, future studies are required to determine whether CAPN6 may be used as an intervention target for CKD-related skeletal muscle atrophy.

CAPN6 in disease: An emerging therapeutic target (Review)

As a member of the calpain protein family, calpain6 (CAPN6) is highly expressed mainly in the placenta and embryos. It plays a number of important roles in cellular processes, such as the stabilization of microtubules, the main-tenance of cell stability, the control of cell movement and the inhibition of apoptosis. In recent years, various studies have found that CAPN6 is one of the contributing factors associated with the tumorigenesis of uterine tumors and osteosarcoma, and that CAPN6 participates in the development of tumors by promoting cell proliferation and angiogenesis, and by inhibiting apoptosis, which is mainly regulated by the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) pathway. Due to its abnormal cellular expression, CAPN6 has also been found to be associated with a number of diseases, such as white matter damage and muscular dystrophy. Therefore, CAPN6 may be a novel therapeutic target for these diseases. In the present review, the role of CAPN6 in disease and its possible use as a target in various therapies are discussed.

TIM-3 Expression Is Downregulated on Human NK Cells in Response to Cancer Targets in Synergy with Activation

Among natural killer (NK) cell receptors, the T-cell immunoglobulin and mucin-containing domain (TIM-3) has been associated with both inhibitory and activating functions, depending on context and activation pathway. Ex vivo and in vitro, expression of TIM-3 is inducible and depends on activation stimulus. Here, we report that TIM-3 expression can be downregulated on NK cells under specific conditions. When NK cells are exposed to cancer targets, they synergize with stimulation conditions to induce a substantial decrease in TIM-3 expression on their surface. We found that such downregulation occurs following prior NK activation. Downregulated TIM-3 expression correlated to lower cytotoxicity and lower interferon gamma (IFN-γ) expression, fueling the notion that TIM-3 might function as a benchmark for human NK cell dysfunction.

Transcriptomics and Prognosis Analysis to Identify Critical Biomarkers in Invasive Breast Carcinoma

OBJECTIVE

Invasive breast cancer (BRCA) is one of the prevalent types of invasive tumors with high mortality worldwide. Due to the lack of effective treatment to control the recurrence of distant metastases, the prognosis of BRCA is still very unsatisfactory. We aimed to find some biomarkers by bioinformatics analysis for survival prediction.

METHODS

Differentially expressed genes (DEGs) were screened out based on tumor group and normal group. Then, the weighted gene correlation network analysis (WGCNA) was employed to identify the clinically associated gene sets. Meanwhile, the enrichment analyses were performed for the functional annotation of the critical genes. The Kaplan Meier analysis calculated the essential genes' prognostic value.

RESULTS

After threshold screening, 1655 DEGs were obtained for subsequent analysis. 51 out of 1655 DEGs were significantly associated with BRCA patients' estrogen receptor status via WGCNA. Three genes (FABP7, CXCL3, and LOC284578) out of the 51 genes were associated with overall survival, and 3 genes were relapse-free survival associated. Finally, we obtained 5 essential prognostic associated genes (FABP7, CXCL3, LOC284578, CAPN6, and NRG2), which could be used as prognostic factors for BRCA.

CONCLUSION

Our findings obtained a gene module associated with BRCA clinical trait and several key genes that acted as essential components in the prognostic of cancer, which may improve its treatment.

miR-449a: a potential therapeutic agent for cancer

MicroRNAs (miRNAs) have been reported to be associated with cancer progression and carcinogenesis. They are small, highly conserved, noncoding RNA molecules consisting of 19-25 nucleotides. By binding to complementary binding sites within the 3'-untranslated region of target mRNAs, miRNAs inhibit the translation of mRNAs or promote their degradation. miRNAs play critical roles in cancer initiation and development by functioning either as oncogenes or as tumor suppressors. Similarly, several studies have shown that miRNAs are involved in regulating various biological processes, including apoptosis, proliferation, cellular differentiation, signal transduction, and carcinogenesis. Among miRNAs, one that may be of particular interest in cancer biology is miR-449a, which has been reported to inhibit tumor growth, invasion, and metastasis, and to promote apoptosis and differentiation through the transforming growth factor-β activated kinase 1, NOTCH, nuclear factor-κB/P65/vascular endothelial growth factor, retinoblastoma-E2F, mitogen-activated protein kinase signaling pathways, WNT-β-catenin signaling, tumor protein P53, and androgen receptor signaling pathways. The miR-449 cluster is located in the second intron of CDC20B on chromosome 5q11.2, a region that has been identified as a susceptibility locus in cancer, and the abnormal expression of miR-449a may be related to the occurrence and development of tumors. As one example, miR-449a has been reported to be involved in the development of carcinoma and may be a potential prognostic indicator. On the basis of the putative pathogenetic relationships between cancer and miR-449a, we consider that miR-449a has the potential to serve as a therapeutic agent for the treatment of some types of cancer. In this review, the role of miR-449a in tumorigenesis and its mechanism of action are explored. Furthermore, its potential as a therapeutic agent in cancer treatment is considered.

miR-449a promotes liver cancer cell apoptosis by downregulation of Calpain 6 and POU2F1

Our previous study shows that Calpain 6 (CAPN6) expression is regulated by PI3K-Akt in liver cancer through POU2F1 and CAPN6 which promote cell proliferation and inhibit apoptosis of liver cancer cells. microRNAs (miRNAs) plays important roles in regulation of gene expression. However, whether miRNAs regulates CAPN6 expression and its cellular function is still unknown. This study aims to investigate how miRNAs regulate liver cancer apoptosis through POU2F1-CAPN6. It was verified that POU2F1 could promote cell proliferation and inhibit apoptosis through CAPN6. Using methods of bioinformatics, miR-449a was predicted as a potential regulator of both CAPN6 and POU2F1. It was verified that CAPN6 and POU2F1 were the target genes of miR-449a by luciferase assay. CAPN6 and POU2F1 protein and mRNA levels decreased in liver cancer cells with miR-449a overexpression using western blot and real time RT-PCR assays. miR-449a expression was lower in liver cancer tissues compared with their normal ones, so did the cells. Overexpression of miR-449a inhibited cell proliferation, induced G1 phase arrest and cell apoptosis in liver cancer. Further research demonstrated that miR-449a inhibited cancer cell proliferation and induced apoptosis via suppressing both POU2F1 and CAPN6. The study indicated that miR-449a functions as a tumor inhibitor in liver cancer by decreasing POU2F1 and CAPN6 expression in liver cancer.

Decreased calpain 6 expression is associated with tumorigenesis and poor prognosis in HNSCC

Calpains are a family of intracellular cysteine proteases involved in various biological processes. Previously, the family was identified to have abnormal expression in several types of malignant tumor. Calpain 6 was less well known; however, it was recently identified to be involved in the carcinogenesis of certain types of malignant tumor. However, the expression of calpain 6 in head and neck squamous cell carcinoma (HNSCC) remains unclear. A total of six datasets from the Gene Expression Omnibus (GEO) was analyzed and an association between calpain 6 expression levels and HNSCC was identified, with the expression of calpain 6 observed to be significantly decreased in HNSCC (P<0.01). However, the expression of calpain 6 may vary between distinct tumor stages of HNSCC. Furthermore, calpain 6 expression was positively associated with the survival rate in patients with HNSCC (P<0.05), with increased expression of calpain 6 associated with an improved survival outcome. Calpain 6 expression was analyzed using an HNSCC tissue microarray and these results were consistent with the statistical analysis of the bioinformatics data from the GEO, indicating that calpain 6 may be a tumor suppressor protein in HNSCC.

The Mechanism by Which Amentoflavone Improves Insulin Resistance in HepG2 Cells

Background: The aim of this study was to explore the mechanism by which amentoflavone (AME) improves insulin resistance in a human hepatocellular liver carcinoma cell line (HepG2). Methods: A model of insulin resistant cells was established in HepG2 by treatment with high glucose and insulin. The glucose oxidase method was used to detect the glucose consumption in each group. To determine the mechanism by which AME improves insulin resistance in HepG2 cells, enzyme-linked immunosorbent assay (ELISA) and western blotting were used to detect the expression of phosphatidyl inositol 3-kinase (PI3K), Akt, and pAkt; the activity of the enzymes involved in glucose metabolism; and the levels of inflammatory cytokines. Results: Insulin resistance was successfully induced in HepG2 cells. After treatment with AME, the glucose consumption increased significantly in HepG2 cells compared with the model group (MG). The expression of PI3K, Akt, and pAkt and the activity of 6-phosphofructokinas (PFK-1), glucokinase (GCK), and pyruvate kinase (PK) increased, while the activity of glycogen synthase kinase-3 (GSK-3), phosphoenolpyruvate carboxylase kinase (PEPCK), and glucose-6-phosphatase (G-6-Pase) as well as the levels of interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), and C reactive protein (CRP) decreased. Conclusions: The mechanism by which treatment with AME improves insulin resistance in HepG2 cells may involve the PI3K-Akt signaling pathway, the processes of glucose oxygenolysis, glycogen synthesis, gluconeogenesis and inflammatory cytokine expression.

Tumor Necrosis Factor Alpha and Insulin-Like Growth Factor 1 Induced Modifications of the Gene Expression Kinetics of Differentiating Skeletal Muscle Cells

Introduction

TNF-α levels are increased during muscle wasting and chronic muscle degeneration and regeneration processes, which are characteristic for primary muscle disorders. Pathologically increased TNF-α levels have a negative effect on muscle cell differentiation efficiency, while IGF1 can have a positive effect; therefore, we intended to elucidate the impact of TNF-α and IGF1 on gene expression during the early stages of skeletal muscle cell differentiation.

Methodology/Principal Findings

This study presents gene expression data of the murine skeletal muscle cells PMI28 during myogenic differentiation or differentiation with TNF-α or IGF1 exposure at 0 h, 4 h, 12 h, 24 h, and 72 h after induction. Our study detected significant coregulation of gene sets involved in myoblast differentiation or in the response to TNF-α. Gene expression data revealed a time- and treatment-dependent regulation of signaling pathways, which are prominent in myogenic differentiation. We identified enrichment of pathways, which have not been specifically linked to myoblast differentiation such as doublecortin-like kinase pathway associations as well as enrichment of specific semaphorin isoforms. Moreover to the best of our knowledge, this is the first description of a specific inverse regulation of the following genes in myoblast differentiation and response to TNF-α: Aknad1, Cmbl, Sepp1, Ndst4, Tecrl, Unc13c, Spats2l, Lix1, Csdc2, Cpa1, Parm1, Serpinb2, Aspn, Fibin, Slc40a1, Nrk, and Mybpc1. We identified a gene subset (Nfkbia, Nfkb2, Mmp9, Mef2c, Gpx, and Pgam2), which is robustly regulated by TNF-α across independent myogenic differentiation studies.

Conclusions

This is the largest dataset revealing the impact of TNF-α or IGF1 treatment on gene expression kinetics of early in vitro skeletal myoblast differentiation. We identified novel mRNAs, which have not yet been associated with skeletal muscle differentiation or response to TNF-α. Results of this study may facilitate the understanding of transcriptomic networks underlying inhibited muscle differentiation in inflammatory diseases.

Capn4 contributes to tumour growth and metastasis of hepatocellular carcinoma by activation of the FAK-Src signalling pathways

Calpain small subunit 1 (Capn4) has been identified as a major gene that promotes metastasis of hepatocellular carcinoma (HCC). However, the mechanism by which Capn4 promotes progression of HCC is not understood. In this study, we found that Capn4 expression was increased in highly metastatic HCC cell lines and in tumour tissue from HCC patients compared to healthy patient tissue. Over-expression of Capn4 in HCC cells enhanced tumour cell growth in vitro and increased invasiveness, tumourigenicity and lung metastasis in vivo. Protein microarray analyses showed that expression of multiple proteins was regulated by Capn4. Interestingly, Capn4 was found to physically associate with FAK and promoted hyperactivity of the FAK-Src signalling pathway via increased phosphorylation of specific tyrosine residues of FAK, Src and p130Cas. Knock-down of Capn4 expression suppressed the malignant behaviour of HCC cells and inhibited the FAK-Src signalling pathway. Furthermore, Capn4-mediated invasion and metastasis of HCC cells required up-regulation of matrix metalloproteinase-2 (MMP2) through activation of this signalling pathway. Our clinical data revealed that Capn4 expression correlated well with the levels of phospho-FAK, and over-expression of both Capn4 and phospho-FAK correlates with the poorest survival outcomes in HCC. In conclusion, our data showed that Capn4 can contribute to HCC growth and metastasis via activation of the FAK-Src signalling pathway and MMP2.

FoxD3-regulated microRNA-137 suppresses tumour growth and metastasis in human hepatocellular carcinoma by targeting AKT2

microRNAs, frequently deregulated in human cancer, have been implicated in the progression of hepatocarcinogenesis. Here, we show that microRNA (miR)-137 is significantly down-regulated in hepatocellular carcinoma (HCC). Its decreased expression is associated with vein invasion, incomplete Involucrum, and distant metastasis. Multivariate analysis suggests that miR-137 is an independent indicator for poor survival. We next show that over-expression of miR-137 suppresses cell proliferation, migration and invasion in vitro. Conversely, miR-137 inhibition promotes HCC cell growth. We also identify AKT2 as a key target of miR-137 in this context. Statistical data reveal a reverse correlation of AKT2 and miR-137 expression in HCC patients. Silencing of AKT2 phenotypically copied miR-137-induced phenotypes, whereas re-expression of AKT2 reversed the suppressive effects of miR-137. Further investigations showed that miR-137 exerted its anti-tumour activity via inhibiting the AKT2/mTOR pathway. Moreover, we demonstrate that FoxD3 directly binds to the promoter of miR-137 and activates its transcription. In vivo studies confirm that FoxD3-regulated miR-137 inhibited HCC growth and metastasis via targeting AKT2. Together, our findings indicate that miR-137 is a valuable biomarker for HCC prognosis and the FoxD3/miR-137/AKT2 regulatory network plays an important role in HCC progression.

Runx2 promotes both osteoblastogenesis and novel osteoclastogenic signals in ST2 mesenchymal progenitor cells

We profiled the global gene expression of a bone marrow-derived mesenchymal pluripotent cell line in response to Runx2 expression. Besides osteoblast differentiation, Runx2 promoted the osteoclastogenesis of co-cultured splenocytes. This was attributable to the upregulation of many novel osteoclastogenic genes and the downregulation of anti-osteoclastogenic genes.

INTRODUCTION

In addition to being a master regulator for osteoblast differentiation, Runx2 controls osteoblast-driven osteoclastogenesis. Previous studies profiling gene expression during osteoblast differentiation had limited focus on Runx2 or paid little attention to its role in mediating osteoblast-driven osteoclastogenesis.

METHODS

ST2/Rx2(dox), a bone marrow-derived mesenchymal pluripotent cell line that expresses Runx2 in response to Doxycycline (Dox), was used to profile Runx2-induced gene expression changes. Runx2-induced osteoblast differentiation was assessed based on alkaline phosphatase staining and expression of classical marker genes. Osteoclastogenic potential was evaluated by TRAP staining of osteoclasts that differentiated from primary murine splenocytes co-cultured with the ST2/Rx2(dox) cells. The BeadChip™ platform (Illumina) was used to interrogate genome-wide expression changes in ST2/Rx2(dox) cultures after treatment with Dox or vehicle for 24 or 48 h. Expression of selected genes was also measured by RT-qPCR.

RESULTS

Dox-mediated Runx2 induction in ST2 cells stimulated their own differentiation along the osteoblast lineage and the differentiation of co-cultured splenocytes into osteoclasts. The latter was attributable to the stimulation of osteoclastogenic genes such as Sema7a, Ltc4s, Efnb1, Apcdd1, and Tnc as well as the inhibition of anti-osteoclastogenic genes such as Tnfrsf11b (OPG), Sema3a, Slco2b1, Ogn, Clec2d (Ocil), Il1rn, and Rspo2.

CONCLUSION

Direct control of osteoblast differentiation and concomitant indirect control of osteoclast differentiation, both through the activity of Runx2 in pre-osteoblasts, constitute a novel mechanism of coordination with a potential crucial role in coupling bone formation and resorption.