TMCO1-mediated Ca2+ leak underlies osteoblast functions via CaMKII signaling

TMCO1 is upregulated in breast cancer and regulates the response to pro-apoptotic agents in breast cancer cells

The release of Ca2+ ions from endoplasmic reticulum calcium stores is a key event in a variety of cellular processes, including gene transcription, migration and proliferation. This release of Ca2+ often occurs through inositol 1,4,5-triphosphate receptors and the activity of these channels and the levels of stored Ca2+ in the endoplasmic reticulum are important regulators of cell death in cancer cells. A recently identified Ca2+ channel of the endoplasmic reticulum is transmembrane and coiled-coil domains 1 (TMCO1). In this study, we link the overexpression of TMCO1 with prognosis in node-positive basal breast cancer patients. We also identify interacting proteins of TMCO1, which include endoplasmic reticulum-resident proteins involved in Ca2+ regulation and proteins directly involved in nucleocytoplasmic transport. Interacting proteins included nuclear transport proteins and TMCO1 was shown to have both nuclear and endoplasmic reticulum localisation in MDA-MB-231 basal breast cancer cells. These studies also define a role for TMCO1 in the regulation of breast cancer cells in their sensitivity to BCL-2/MCL-1 inhibitors, analogous to the role of inositol 1,4,5-triphosphate receptors in the regulation of cell death pathways activated by these agents.

LMK-235 suppresses osteoclastogenesis and promotes osteoblastogenesis by inhibiting HDAC4

Osteoblasts and osteoclasts play an important role in maintaining the structural integrity of bone tissue, in which osteoclasts degrade bone structure and osteoblasts restore bone tissue. The imbalance of osteoblast and osteoclast function can lead to many bone-related diseases, such as osteoporosis and inflammatory osteolysis. The drug that can both promote bone formation and inhibit bone loss will be able to treat those diseases. In this study, it was found that LMK-235, an selective HDAC4/5 inhibitor, inhibited the differentiation and maturation of osteoclasts by regulating NF-κB and p-Smad2/3 signaling pathways via inhibition of HDAC4. At the same time, we found that LMK-235 promoted osteoblast mineralization by upregulating Runx2 expression via inhibition of HDAC4. In vivo, LMK-235 was able to alleviate lipopolysaccharide (LPS)-induced calvarial osteolysis and promote the repair of bone defects. Taken together, LMK-235 suppresses osteoclast differentiation and promotes osteoblast formation by inhibiting HDAC4. This may provide a valuable treatment for bone diseases caused by abnormal osteoclast bone resorption and osteoblast bone regeneration.

The role of calcium channels in osteoporosis and their therapeutic potential

Osteoporosis, a systemic skeletal disorder marked by diminished bone mass and compromised bone microarchitecture, is becoming increasingly prevalent due to an aging population. The underlying pathophysiology of osteoporosis is attributed to an imbalance between osteoclast-mediated bone resorption and osteoblast-mediated bone formation. Osteoclasts play a crucial role in the development of osteoporosis through various molecular pathways, including the RANK/RANKL/OPG signaling axis, cytokines, and integrins. Notably, the calcium signaling pathway is pivotal in regulating osteoclast activation and function, influencing bone resorption activity. Disruption in calcium signaling can lead to increased osteoclast-mediated bone resorption, contributing to the progression of osteoporosis. Emerging research indicates that calcium-permeable channels on the cellular membrane play a critical role in bone metabolism by modulating these intracellular calcium pathways. Here, we provide an overview of current literature on the regulation of plasma membrane calcium channels in relation to bone metabolism with particular emphasis on their dysregulation during the progression of osteoporosis. Targeting these calcium channels may represent a potential therapeutic strategy for treating osteoporosis.

mPPTMP195 nanoparticles enhance fracture recovery through HDAC4 nuclear translocation inhibition

Delayed repair of fractures seriously impacts patients' health and significantly increases financial burdens. Consequently, there is a growing clinical demand for effective fracture treatment. While current materials used for fracture repair have partially addressed bone integrity issues, they still possess limitations. These challenges include issues associated with autologous material donor sites, intricate preparation procedures for artificial biomaterials, suboptimal biocompatibility, and extended degradation cycles, all of which are detrimental to bone regeneration. Hence, there is an urgent need to design a novel material with a straightforward preparation method that can substantially enhance bone regeneration. In this context, we developed a novel nanoparticle, mPPTMP195, to enhance the bioavailability of TMP195 for fracture treatment. Our results demonstrate that mPPTMP195 effectively promotes the differentiation of bone marrow mesenchymal stem cells into osteoblasts while inhibiting the differentiation of bone marrow mononuclear macrophages into osteoclasts. Moreover, in a mouse femur fracture model, mPPTMP195 nanoparticles exhibited superior therapeutic effects compared to free TMP195. Ultimately, our study highlights that mPPTMP195 accelerates fracture repair by preventing HDAC4 translocation from the cytoplasm to the nucleus, thereby activating the NRF2/HO-1 signaling pathway. In conclusion, our study not only proposes a new strategy for fracture treatment but also provides an efficient nano-delivery system for the widespread application of TMP195 in various other diseases.

Activation of CaMKII/HDAC4 by SDF1 contributes to pulmonary arterial hypertension via stabilization Runx2

Stromal derived factor 1 (SDF1) has been shown to be involved in the pathogenesis of pulmonary artery hypertension (PAH). However, the detailed molecular mechanisms remain unclear. To address this, we utilized primary cultured rat pulmonary artery smooth muscle cells (PASMCs) and monocrotaline (MCT)-induced PAH rat models to investigate the mechanisms of SDF1 driving PASMCs proliferation and pulmonary arterial remodeling. SDF1 increased runt-related transcription factor 2 (Runx2) acetylation by Calmodulin (CaM)-dependent protein kinase II (CaMKII)-dependent HDAC4 cytoplasmic translocation, elevation of Runx2 acetylation conferred its resistance to proteasome-mediated degradation. The accumulation of Runx2 further upregulated osteopontin (OPN) expression, finally leading to PASMCs proliferation. Blocking SDF1, suppression of CaMKII, inhibition the nuclear export of HDAC4 or silencing Runx2 attenuated pulmonary arterial remodeling and prevented PAH development in MCT-induced PAH rat models. Our study provides novel sights for SDF1 induction of PASMCs proliferation and suggests that targeting SDF1/CaMKII/HDAC4/Runx2 axis has potential value in the management of PAH.

Osteoinductive activity of photobiomodulation in an organotypic bone model

Photobiomodulation (PBM) is a technique that harnesses non-ionizing light at specific wavelengths, triggering the modulation of metabolic pathways, engendering favourable biological outcomes that reduce inflammation and foster enhanced tissue healing and regeneration. PBM holds significant promise for bone tissue applications due to its non-invasive nature and ability to stimulate cellular activity and vascularization within the healing framework. Notwithstanding, the impact of PBM on bone functionality remains largely undisclosed, particularly in the absence of influencing factors such as pathologies or regenerative therapies. This study aims to investigate the potential effects of PBM using red (660 nm) (RED) and near-infrared (808 nm) (NIR) wavelengths within an ex vivo bone culture system - the organotypic embryonic chicken femur model. A continuous irradiation mode was used, administering a total energy dose of 1.0 J, at an intensity of 100 mW for 10 s, which was repeated four times over the course of the 11-day culture period. The primary focus is on characterizing the expression of pivotal osteoblastic genes, the maturation and deposition of collagen, and the formation of bone mineral. Exposing femora to both RED and NIR wavelengths led to a notable increase in the expression of osteochondrogenic transcription factors (i.e., SOX9 and RUNX2), correlating with enhanced mineralization. Notably, NIR irradiation further elevated the expression of bone matrix-related genes and fostered enhanced deposition and maturation of fibrillar collagen. This study demonstrates that PBM has the potential to enhance osteogenic functionality within a translational organotypic bone culture system, with the NIR wavelength showing remarkable capabilities in augmenting the formation and maturation of the collagenous matrix.

Role of a novel circRNA-CGNL1 in regulating pancreatic cancer progression via NUDT4-HDAC4-RUNX2-GAMT-mediated apoptosis

BACKGROUND

Pancreatic cancer (PC) is an extremely malignant tumor with low survival rate. Effective biomarkers and therapeutic targets for PC are lacking. The roles of circular RNAs (circRNAs) in cancers have been explored in various studies, however more work is needed to understand the functional roles of specific circRNAs. In this study, we explore the specific role and mechanism of circ_0035435 (termed circCGNL1) in PC.

METHODS

qRT-PCR analysis was performed to detect circCGNL1 expression, indicating circCGNL1 had low expression in PC cells and tissues. The function of circCGNL1 in PC progression was examined both in vitro and in vivo. circCGNL1-interacting proteins were identified by performing RNA pulldown, co-immunoprecipitation, GST-pulldown, and dual-luciferase reporter assays.

RESULTS

Overexpressing circCGNL1 inhibited PC proliferation via promoting apoptosis. CircCGNL1 interacted with phosphatase nudix hydrolase 4 (NUDT4) to promote histone deacetylase 4 (HDAC4) dephosphorylation and subsequent HDAC4 nuclear translocation. Intranuclear HDAC4 mediated RUNX Family Transcription Factor 2 (RUNX2) deacetylation and thereby accelerating RUNX2 degradation. The transcription factor, RUNX2, inhibited guanidinoacetate N-methyltransferase (GAMT) expression. GAMT was further verified to induce PC cell apoptosis via AMPK-AKT-Bad signaling pathway.

CONCLUSIONS

We discovered that circCGNL1 can interact with NUDT4 to enhance NUDT4-dependent HDAC4 dephosphorylation, subsequently activating HDAC4-RUNX2-GAMT-mediated apoptosis to suppress PC cell growth. These findings suggest new therapeutic targets for PC.

Epigenetic Regulation of Autophagy in Bone Metabolism

The skeletal system is crucial for supporting bodily functions, protecting vital organs, facilitating hematopoiesis, and storing essential minerals. Skeletal homeostasis, which includes aspects such as bone density, structural integrity, and regenerative processes, is essential for normal skeletal function. Autophagy, an intricate intracellular mechanism for degrading and recycling cellular components, plays a multifaceted role in bone metabolism. It involves sequestering cellular waste, damaged proteins, and organelles within autophagosomes, which are then degraded and recycled. Autophagy's impact on bone health varies depending on factors such as regulation, cell type, environmental cues, and physiological context. Despite being traditionally considered a cytoplasmic process, autophagy is subject to transcriptional and epigenetic regulation within the nucleus. However, the precise influence of epigenetic regulation, including DNA methylation, histone modifications, and non-coding RNA expression, on cellular fate remains incompletely understood. The interplay between autophagy and epigenetic modifications adds complexity to bone cell regulation. This article provides an in-depth exploration of the intricate interplay between these two regulatory paradigms, with a focus on the epigenetic control of autophagy in bone metabolism. Such an understanding enhances our knowledge of bone metabolism-related disorders and offers insights for the development of targeted therapeutic strategies.

Biomimetic Structural Protein Based Magnetic Responsive Scaffold for Enhancing Bone Regeneration by Physical Stimulation on Intracellular Calcium Homeostasis

The bone matrix has distinct architecture and biochemistry which present a barrier to synthesizing bone-mimetic regenerative scaffolds. To mimic the natural structures and components of bone, biomimetic structural decellularized extracellular matrix (ECM)/regenerated silk fibroin (RSF) scaffolds incorporated with magnetic nanoparticles (MNP) are prepared using a facile synthetic methodology. The ECM/RSF/MNP scaffold is a hierarchically organized and interconnected porous structure with silk fibroin twined on the collagen nanofibers. The scaffold demonstrates saturation magnetization due to the presence of MNP, along with good cytocompatibility. Moreover, the β-sheet crystalline domain of RSF and the chelated MNP could mimic the deposition of hydroxyapatite and enhance compressive modulus of the scaffold by ≈20%. The results indicate that an external static magnetic field (SMF) with a magnetic responsive scaffold effectively promotes cell migration, osteogenic differentiation, neogenesis of endotheliocytes in vitro, and new bone formation in a critical-size femur defect rat model. RNA sequencing reveals that the molecular mechanisms underlying this osteogenic effect involve calsequestrin-2-mediated Ca2+ release from the endoplasmic reticulum to activate Ca2+ /calmodulin/calmodulin-dependent kinase II signaling axis. Collectively, bionic magnetic scaffolds with SMF stimulation provide a potent strategy for bone regeneration through internal structural cues, biochemical composition, and external physical stimulation on intracellular Ca2+ homeostasis.

Osteoblast-lineage calcium/calmodulin-dependent kinase 2 delta and gamma regulates bone mass and quality

Bone regulates its mass and quality in response to diverse mechanical, hormonal, and local signals. The bone anabolic or catabolic responses to these signals are often received by osteocytes, which then coordinate the activity of osteoblasts and osteoclasts on bone surfaces. We previously established that calcium/calmodulin-dependent kinase 2 (CaMKII) is required for osteocytes to respond to some bone anabolic cues in vitro. However, a role for CaMKII in bone physiology in vivo is largely undescribed. Here, we show that conditional codeletion of the most abundant isoforms of CaMKII (delta and gamma) in mature osteoblasts and osteocytes [Ocn-cre:Camk2d/Camk2g double-knockout (dCKO)] caused severe osteopenia in both cortical and trabecular compartments by 8 wk of age. In addition to having less bone mass, dCKO bones are of worse quality, with significant deficits in mechanical properties, and a propensity to fracture. This striking skeletal phenotype is multifactorial, including diminished osteoblast activity, increased osteoclast activity, and altered phosphate homeostasis both systemically and locally. These dCKO mice exhibited decreased circulating phosphate (hypophosphatemia) and increased expression of the phosphate-regulating hormone fibroblast growth factor 23. Additionally, dCKO mice expressed less bone-derived tissue nonspecific alkaline phosphatase protein than control mice. Consistent with altered phosphate homeostasis, we observed that dCKO bones were hypo-mineralized with prominent osteoid seams, analogous to the phenotypes of mice with hypophosphatemia. Altogether, these data reveal a fundamental role for osteocyte CaMKIIδ and CaMKIIγ in the maintenance of bone mass and bone quality and link osteoblast/osteocyte CaMKII to phosphate homeostasis.

ER Ca2+ overload activates the IRE1α signaling and promotes cell survival

BACKGROUND

Maintaining homeostasis of Ca²⁺ stores in the endoplasmic reticulum (ER) is crucial for proper Ca²⁺ signaling and key cellular functions. Although Ca²⁺ depletion has been known to cause ER stress which in turn activates the unfolded protein response (UPR), how UPR sensors/transducers respond to excess Ca²⁺ when ER stores are overloaded remain largely unclear.

RESULTS

Here, we report for the first time that overloading of ER Ca²⁺ can directly sensitize the IRE1α-XBP1 axis. The overloaded ER Ca²⁺ in TMCO1-deficient cells can cause BiP dissociation from IRE1α, promote the dimerization and stability of the IRE1α protein, and boost IRE1α activation. Intriguingly, attenuation of the over-activated IRE1α-XBP1s signaling by a IRE1α inhibitor can cause a significant cell death in TMCO1-deficient cells.

CONCLUSIONS

Our data establish a causal link between excess Ca²⁺ in ER stores and the selective activation of IRE1α-XBP1 axis, underscoring an unexpected role of overload of ER Ca²⁺ in IRE1α activation and in preventing cell death.

RCN2 promotes Nasopharyngeal carcinoma progression by curbing Calcium flow and Mitochondrial apoptosis

OBJECTIVE

Evidence suggests that calcium release from the endoplasmic reticulum (ER) can be induced to cause calcium overload, which in turn can trigger mitochondrial-dependent apoptosis. Dysregulation of systemic calcium homeostasis and changing levels of calcium-binding proteins have been shown to be associated with the malignant behavior of tumors. However, the precise molecular mechanism underlying Nasopharyngeal carcinoma (NPC) remains uncertain.

METHODS

Reticulocalbin (RCN2) expression in NPC was assessed using GEO database, western blot analysis and qRT-PCR. Apoptosis was assessed using flow cytometric analysis and the expression levels of apoptosis-related proteins were determined using western blot analysis. Intracellular calcium ion concentrations were measured using fluorescence imaging. The findings from these analyses were validated in vitro using nude mice models. Luciferase and ChIP assays were used to measure transcriptional regulation. Clinical significance was evaluated using tissue microarray analysis (n=150).

RESULTS

Our results showed that RCN2 promotes malignancy by causing Ca2+ flow imbalance, which leads to the initiation of the stress-mediated mitochondrial apoptosis pathway. We demonstrate that calreticulin (CALR) resides primarily in the endoplasmic reticulum and interacts with RCN2. Moreover, the transcription factors YY1 and homeobox protein goosecoid (GSC) both contribute to the initiation of RCN2 transcription by directly binding to the predicted promoter region of RCN2. Finally, high expression of RCN2 combined with high expression of GSC and YY1 may serve as an important clinical biomarker of poor prognosis in patients with NPC.

CONCLUSION

YY1 and GSC are upstream regulators of RCN2, involved in mitochondrial calcium overload and stress-induced mitochondrial apoptosis. Thus, they can play significant role in the malignant development of NPCs.

HDAC4 in cancer: A multitasking platform to drive not only epigenetic modifications

Controlling access to genomic information and maintaining its stability are key aspects of cell life. Histone acetylation is a reversible epigenetic modification that allows access to DNA and the assembly of protein complexes that regulate mainly transcription but also other activities. Enzymes known as histone deacetylases (HDACs) are involved in the removal of the acetyl-group or in some cases of small hydrophobic moieties from histones but also from the non-histone substrate. The main achievement of HDACs on histones is to repress transcription and promote the formation of more compact chromatin. There are 18 different HDACs encoded in the human genome. Here we will discuss HDAC4, a member of the class IIa family, and its possible contribution to cancer development.

PVA/pectin composite hydrogels inducing osteogenesis for bone regeneration

Hydrogels composed from biomolecules have gained great interests as biomaterials for tissue engineering. However, their poor mechanical properties limit their application potential. Here, we synthesized a series of tough composite hydrogels from poly (vinyl alcohol) (PVA) and pectin for bone tissue engineering. With a balance of scaffold stiffness and pore size, PVA-Pec-10 hydrogel enhanced adhesion and proliferation of osteoblasts. The hydrogel significantly promoted osteogenesis in vitro by improving the alkaline phosphates (ALP) activity and calcium biomineralization, as well as upregulating the expressions of osteoblastic genes. The composite hydrogel also accelerated the bone healing process in vivo after transplantation into the femoral defect. Additionally, our study demonstrated that pectin and its Ca²⁺ crosslinking network play a crucial role of inducing osteogenesis through regulating the Ca²⁺/CaMKII and BMP-SMAD1/5 signaling. The optimized structure composition and multifunctional properties make PVA-Pec hydrogel highly promising to serve as a candidate for bone tissue regeneration.

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Recoverable PVA-Pec hydrogel is prepared by the freezing-thawing process.

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PVA-Pec-10 hydrogel display well attachment and osteogenesis capacity.

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PVA-Pecl-10 hydrogel enhanced osteogenesis by Ca²⁺/CaMKII and BMP-SMAD1/5 signaling.

Nanocarrier-Assisted Delivery of Metformin Boosts Remodeling of Diabetic Periodontal Tissue via Cellular Exocytosis-Mediated Regulation of Endoplasmic Reticulum Homeostasis

Endoplasmic reticulum (ER) dysfunction is a potential contributor to the impaired repair capacity of periodontal tissue in diabetes mellitus (DM) patients. Restoring ER homeostasis is thus critical for successful regenerative therapy of diabetic periodontal tissue. Recent studies have shown that metformin can modulate DM-induced ER dysfunction, yet its mechanism remains unclear. Herein, we show that high glucose elevates the intracellular miR-129-3p level due to exocytosis-mediated release failure and subsequently perturbs ER calcium homeostasis via downregulating transmembrane and coiled-coil domain 1 (TMCO1), an ER Ca²⁺ leak channel, in periodontal ligament stem cells (PDLSCs). This results in the degradation of RUNX2 via the ubiquitination-dependent pathway, in turn leading to impaired PDLSCs osteogenesis. Interestingly, metformin could upregulate P2X7R-mediated exosome release and decrease intracellular miR-129-3p accumulation, which restores ER homeostasis and thereby rescues the impaired PDLSCs. To further demonstrate the in vivo effect of metformin, a nanocarrier for sustained local delivery of metformin (Met@HALL) in periodontal tissue is developed. Our results demonstrate that compared to controls, Met@HALL with enhanced cytocompatibility and pro-osteogenic activity could boost the remodeling of diabetic periodontal tissue in rats. Collectively, our findings unravel a mechanism of metformin in restoring cellular ER homeostasis, enabling the development of a nanocarrier-mediated ER targeting strategy for remodeling diabetic periodontal tissue.

Anoctamin 1 controls bone resorption by coupling Cl- channel activation with RANKL-RANK signaling transduction

Osteoclast over-activation leads to bone loss and chloride homeostasis is fundamental importance for osteoclast function. The calcium-activated chloride channel Anoctamin 1 (also known as TMEM16A) is an important chloride channel involved in many physiological processes. However, its role in osteoclast remains unresolved. Here, we identified the existence of Anoctamin 1 in osteoclast and show that its expression positively correlates with osteoclast activity. Osteoclast-specific Anoctamin 1 knockout mice exhibit increased bone mass and decreased bone resorption. Mechanistically, Anoctamin 1 deletion increases intracellular Cl^- concentration, decreases H⁺ secretion and reduces bone resorption. Notably, Anoctamin 1 physically interacts with RANK and this interaction is dependent upon Anoctamin 1 channel activity, jointly promoting RANKL-induced downstream signaling pathways. Anoctamin 1 protein levels are substantially increased in osteoporosis patients and this closely correlates with osteoclast activity. Finally, Anoctamin 1 deletion significantly alleviates ovariectomy induced osteoporosis. These results collectively establish Anoctamin 1 as an essential regulator in osteoclast function and suggest a potential therapeutic target for osteoporosis.

TMCO1 expression promotes cell proliferation and induces epithelial-mesenchymal transformation in human gliomas

Transmembrane and coiled-coil domains 1 (TMCO1) is a recently discovered transmembrane protein of endoplasmic reticulum (ER), which plays a critical role in maintaining calcium homeostasis. TMCO1 dysfunction has been proved to be closely related to a variety of human diseases, including glaucoma, deformities, mental retardation and tumorigenesis. However, the role of TMCO1 in gliomas remains unclear. The purpose of this study was to detect the role of TMCO1 in the pathogenesis and progression of gliomas. This study demonstrated that TMCO1 was upregulated in gliomas and its overexpression predicted poor prognosis. We also revealed that the expression of TMCO1 was associated with the World Health Organization (WHO) grade of gliomas. Knockdown of TMCO1 inhibited the proliferation and induced apoptosis of U87 and U251 cells. In addition, TMCO1 induced GBM cell migration and invasion by promoting epithelial-mesenchymal transition (EMT). These date collectively proved the crucial role of TMCO1 as a novel prognostic factor and underlying therapeutic target for glioma patients.

Cellular stress signaling and the unfolded protein response in retinal degeneration: mechanisms and therapeutic implications

Background

The retina, as part of the central nervous system (CNS) with limited capacity for self-reparation and regeneration in mammals, is under cumulative environmental stress due to high-energy demands and rapid protein turnover. These stressors disrupt the cellular protein and metabolic homeostasis, which, if not alleviated, can lead to dysfunction and cell death of retinal neurons. One primary cellular stress response is the highly conserved unfolded protein response (UPR). The UPR acts through three main signaling pathways in an attempt to restore the protein homeostasis in the endoplasmic reticulum (ER) by various means, including but not limited to, reducing protein translation, increasing protein-folding capacity, and promoting misfolded protein degradation. Moreover, recent work has identified a novel function of the UPR in regulation of cellular metabolism and mitochondrial function, disturbance of which contributes to neuronal degeneration and dysfunction. The role of the UPR in retinal neurons during aging and under disease conditions in age-related macular degeneration (AMD), retinitis pigmentosa (RP), glaucoma, and diabetic retinopathy (DR) has been explored over the past two decades. Each of the disease conditions and their corresponding animal models provide distinct challenges and unique opportunities to gain a better understanding of the role of the UPR in the maintenance of retinal health and function.

Method

We performed an extensive literature search on PubMed and Google Scholar using the following keywords: unfolded protein response, metabolism, ER stress, retinal degeneration, aging, age-related macular degeneration, retinitis pigmentosa, glaucoma, diabetic retinopathy.

Results and conclusion

We summarize recent advances in understanding cellular stress response, in particular the UPR, in retinal diseases, highlighting the potential roles of UPR pathways in regulation of cellular metabolism and mitochondrial function in retinal neurons. Further, we provide perspective on the promise and challenges for targeting the UPR pathways as a new therapeutic approach in age- and disease-related retinal degeneration.

iASPP suppresses Gp78-mediated TMCO1 degradation to maintain Ca2+ homeostasis and control tumor growth and drug resistance

Accumulating preclinical and clinical evidence has supported a central role for alterations in Ca²⁺ homeostasis in the development of cancer. TMCO1 protein is an identified Ca²⁺-channel protein, while its roles in cancer remain obscure. Here, we found that TMCO1 is increased in colon cancer tissues. In addition, it is a substrate of E3 ligase Gp78. Enhanced oncogene iASPP stabilizes TMCO1 by competitively binding with Gp78. Inhibition of iASPP-TMCO1 sensitizes cancer cells’ response to Ca²⁺-induced apoptosis. This study has improved our fundamental understanding of the Ca²⁺ homeostasis in cancer cells. iASPP-TMCO1 axis may present a promising therapeutic target that can combine the conventional drugs to reinforce Ca²⁺-dependent apoptosis.

Ca²⁺ release from the endoplasmic reticulum (ER) is an essential event in the modulation of Ca²⁺ homeostasis, which is coordinated by multiple biological processes, ranging from cell proliferation to apoptosis. Deregulated Ca²⁺ homeostasis is linked with various cancer hallmarks; thus, uncovering the mechanisms underlying Ca²⁺ homeostasis dynamics may lead to new anticancer treatment strategies. Here, we demonstrate that a reported Ca²⁺-channel protein TMCO1 (transmembrane and coiled-coil domains 1) is overexpressed in colon cancer tissues at protein levels but not at messenger RNA levels in colon cancer. Further study revealed that TMCO1 is a substrate of ER-associated degradation E3 ligase Gp78. Intriguingly, Gp78-mediated TMCO1 degradation at K186 is under the control of the iASPP (inhibitor of apoptosis-stimulating protein of p53) oncogene. Mechanistically, iASPP robustly reduces ER Ca²⁺ stores, mainly by competitively binding with Gp78 and interfering with Gp78-mediated TMCO1 degradation. A positive correlation between iASPP and TMCO1 proteins is further validated in human colon tissues. Inhibition of iASPP-TMCO1 axis promotes cytosolic Ca²⁺ overload–induced apoptotic cell death, reducing tumor growth both in vitro and in vivo. Thus, iASPP-TMCO1 represents a promising anticancer treatment target by modulating Ca²⁺ homeostasis.

CBX4-dependent regulation of HDAC3 nuclear translocation reduces Bmp2-induced osteoblastic differentiation and calcification in adamantinomatous craniopharyngioma

BACKGROUND

Calcification of adamantinomatous craniopharyngioma (ACP) often causes problems with tumor resection, leading to a high incidence of deadly complications and tumor recurrence. Histone acetyltransferase (HAT) and histone deacetylase (HDAC) are 2 key enzymes that regulate histone acetylation and play important roles in tumor development. However, the roles of HAT and HDAC in the calcification and osteoblastic differentiation of ACP are not known.

METHODS

In this study, primary cells were isolated from ACP tissues, and calcification was induced with bone morphogenetic protein 2 (Bmp2). HDAC3 expression was assessed in 12 tissue samples by Western blotting and immunohistochemistry. ACP calcification was assessed by Alizarin red staining. A luciferase reporter assay was performed to examine the interaction between miR-181b and the 3'-untranslated region of the polycomb chromobox 4 (CBX4) gene.

RESULTS

Our results showed that the expression of HDAC3 was increased in the calcified ACP samples, but inhibition of HDAC3 promoted ACP cell calcification and osteoblastic differentiation. Mechanistically, HDAC3 nuclear translocation was suppressed by Bmp2, leading to Runx2 protein expression and Osterix, osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) mRNA expression. In addition, this process was suppressed by CBX4, which stabilized the nuclear localization of HDAC3. miR-181b, the expression of which was increased in Bmp2-induced ACP cells, directly targeted and decreased CBX4 expression and inhibited the nuclear localization of HDAC3.

CONCLUSIONS

Our results demonstrate that Bmp2 increases miR-181b levels to directly target and inhibit CBX4 expression, leading to a reduction in the CBX4-dependent regulation of HDAC3 nuclear translocation, which results in Runx2 activation/osteoblastic differentiation and calcium deposition in ACP. Further studies targeting these cascades may contribute to therapeutic interventions used for recurrent ACP. Video Abstract.

Role of histone modification in the occurrence and development of osteoporosis

Osteoporosis is a systemic degenerative bone disease characterized by low bone mass and damage to bone microarchitecture, which increases bone fragility and susceptibility to fracture. The risk of osteoporosis increases with age; with the aging of the global population, osteoporosis is becoming more prevalent, adding to the societal healthcare burden. Histone modifications such as methylation, acetylation, ubiquitination, and ADP-ribosylation are closely related to the occurrence and development of osteoporosis. This article reviews recent studies on the role of histone modifications in osteoporosis. The existing evidence indicates that therapeutic targeting of these modifications to promote osteogenic differentiation and bone formation may be an effective treatment for this disease.

ORF3a of SARS-CoV-2 promotes lysosomal exocytosis-mediated viral egress

Viral entry and egress are important determinants of virus infectivity and pathogenicity. β-coronaviruses, including the COVID-19 virus SARS-CoV-2 and mouse hepatitis virus (MHV), exploit the lysosomal exocytosis pathway for egress. Here, we show that SARS-CoV-2 ORF3a, but not SARS-CoV ORF3a, promotes lysosomal exocytosis. SARS-CoV-2 ORF3a facilitates lysosomal targeting of the BORC-ARL8b complex, which mediates trafficking of lysosomes to the vicinity of the plasma membrane, and exocytosis-related SNARE proteins. The Ca²⁺ channel TRPML3 is required for SARS-CoV-2 ORF3a-mediated lysosomal exocytosis. Expression of SARS-CoV-2 ORF3a greatly elevates extracellular viral release in cells infected with the coronavirus MHV-A59, which itself lacks ORF3a. In SARS-CoV-2 ORF3a, Ser171 and Trp193 are critical for promoting lysosomal exocytosis and blocking autophagy. When these residues are introduced into SARS-CoV ORF3a, it acquires the ability to promote lysosomal exocytosis and inhibit autophagy. Our results reveal a mechanism by which SARS-CoV-2 interacts with host factors to promote its extracellular egress.

The role of TRPV channels in osteoporosis

As the world's population ages, the treatment of osteoporosis is a major problem to be addressed. The cause of osteoporosis remains unclear. Ca²⁺ is not only an important component of bones but also plays a key role in osteoporosis treatment. Transient receptor potential vanilloid (TRPV) channels are one of the TRP channel families that is widely distributed in various organs, playing an important role in the physiological regulation of the human body. Bone formation and bone absorption may require Ca²⁺ transport via TRPV channels. It has been proven that the TRPV subtypes 1, 2, 4, 5, 6 (TRPV1, TRPV2, TRPV4, TRPV5, TRPV6) may affect bone metabolism balance through selective regulation of Ca²⁺. They significantly regulate osteoblast/osteoclast proliferation, differentiation and function. The purpose of this review is to explore the mechanisms of TRPV channels involved in regulation of the differentiation of osteoblasts and osteoclasts, as well as to discuss the latest developments in current researches, which may provide new clues and directions for an in-depth study of osteoporosis and other related bone metabolic diseases.

Role of K+ and Ca2+-Permeable Channels in Osteoblast Functions

Bone-forming cells or osteoblasts play an important role in bone modeling and remodeling processes. Osteoblast differentiation or osteoblastogenesis is orchestrated by multiple intracellular signaling pathways (e.g., bone morphogenetic proteins (BMP) and Wnt signaling pathways) and is modulated by the extracellular environment (e.g., parathyroid hormone (PTH), vitamin D, transforming growth factor β (TGF-β), and integrins). The regulation of bone homeostasis depends on the proper differentiation and function of osteoblast lineage cells from osteogenic precursors to osteocytes. Intracellular Ca²⁺ signaling relies on the control of numerous processes in osteoblast lineage cells, including cell growth, differentiation, migration, and gene expression. In addition, hyperpolarization via the activation of K⁺ channels indirectly promotes Ca²⁺ signaling in osteoblast lineage cells. An improved understanding of the fundamental physiological and pathophysiological processes in bone homeostasis requires detailed investigations of osteoblast lineage cells. This review summarizes the current knowledge on the functional impacts of K⁺ channels and Ca²⁺-permeable channels, which critically regulate Ca²⁺ signaling in osteoblast lineage cells to maintain bone homeostasis.

Identification and Functional Annotation of Genes Related to Bone Stability in Laying Hens Using Random Forests

Skeletal disorders, including fractures and osteoporosis, in laying hens cause major welfare and economic problems. Although genetics have been shown to play a key role in bone integrity, little is yet known about the underlying genetic architecture of the traits. This study aimed to identify genes associated with bone breaking strength and bone mineral density of the tibiotarsus and the humerus in laying hens. Potentially informative single nucleotide polymorphisms (SNP) were identified using Random Forests classification. We then searched for genes known to be related to bone stability in close proximity to the SNPs and identified 16 potential candidates. Some of them had human orthologues. Based on our findings, we can support the assumption that multiple genes determine bone strength, with each of them having a rather small effect, as illustrated by our SNP effect estimates. Furthermore, the enrichment analysis showed that some of these candidates are involved in metabolic pathways critical for bone integrity. In conclusion, the identified candidates represent genes that may play a role in the bone integrity of chickens. Although further studies are needed to determine causality, the genes reported here are promising in terms of alleviating bone disorders in laying hens.

Vascular endothelial growth factor on Runt-related transcript factor-2 in aortic valve cells

BACKGROUND

Calcific aortic valve disease is associated with ageing and high mortality. However, no effective pharmacological treatment has been developed. Vascular endothelial growth factor (VEGF) and its receptor are overexpressed in the calcified aortic valve tissue. However, the role of VEGF in calcific aortic valve disease pathogenesis and its underlying mechanisms remain unclear.

MATERIALS AND METHODS

Runt-related transcription factor 2 expression and calcium-related signalling were investigated in porcine valvular interstitial cells with or without human VEGF-A recombinant protein (VEGF₁₆₅ , 1-100 ng/mL) treatment and/or calmodulin-dependent kinase II (CaMKII) inhibitor (KN93, 10 µmol/L) and inositol triphosphate receptor inhibitor (2-aminoethyldiphenyl borate, 30 µmol/L) for 5 days.

RESULTS

VEGF₁₆₅ -treated cells had higher Runt-related transcription factor 2 expression and CaMKII/ adenosine 3',5'-monophosphate response element-binding protein (CREB) signalling activation than did control cells. KN93 reduced Runt-related transcription factor 2 expression and CREB phosphorylation in VEGF₁₆₅ -treated cells. The 2-aminoethyldiphenyl borate also reduced Runt-related transcription factor 2 expression in VICs treated with VEGF₁₆₅ .

CONCLUSION

VEGF upregulated Runt-related transcription factor 2 expression in VICs by activating the IP3R/CaMKII/CREB signalling pathway.

A comprehensive overview of the complex world of the endo- and sarcoplasmic reticulum Ca2+-leak channels

Inside cells, the endoplasmic reticulum (ER) forms the largest Ca²⁺ store. Ca²⁺ is actively pumped by the SERCA pumps in the ER, where intraluminal Ca²⁺-binding proteins enable the accumulation of large amount of Ca²⁺. IP₃ receptors and the ryanodine receptors mediate the release of Ca²⁺ in a controlled way, thereby evoking complex spatio-temporal signals in the cell. The steady state Ca²⁺ concentration in the ER of about 500 μM results from the balance between SERCA-mediated Ca²⁺ uptake and the passive leakage of Ca²⁺. The passive Ca²⁺ leak from the ER is often ignored, but can play an important physiological role, depending on the cellular context. Moreover, excessive Ca²⁺ leakage significantly lowers the amount of Ca²⁺ stored in the ER compared to normal conditions, thereby limiting the possibility to evoke Ca²⁺ signals and/or causing ER stress, leading to pathological consequences. The so-called Ca²⁺-leak channels responsible for Ca²⁺ leakage from the ER are however still not well understood, despite over 20 different proteins have been proposed to contribute to it. This review has the aim to critically evaluate the available evidence about the various channels potentially involved and to draw conclusions about their relative importance.

The coupling of reduced type H vessels with unloading-induced bone loss and the protection role of Panax quinquefolium saponin in the male mice

Unloading-induced bone loss is a critical complication characterized by the imbalance of bone formation and resorption induced by long-term confinement in bed or spaceflight. CD31^hiEmcn^hi (type H) vessel is a specific subtype of capillary, which was coupled with osteogenesis. However, the change of type H vessel and its contributions to the unloading-induced bone loss remains undisclosed. Herein, we found that bone formation and the number of type H vessels were synchronously reduced in the hindlimb-unloading (HU) mice. Panax quinquefolium saponin (PQS) could increase bone mass, osteoblast function and the number of type H vessels in the HU mice. In vitro, PQS treatment accelerated HMECs migration, augmented the total tube loops and increased the secretion of VEGF and Noggin. Primary osteoblasts function was obviously increased when treated with supernatant from PQS-treated HMECs. These effects of PQS were substantially counteracted when VEGF and Noggin in HMECs were knocked down by siRNA. These results demonstrated that unloading-induced bone loss is coupled with reduction of type H vessels and PQS performs preventive function via promoting type H vessel angiogenesis, which is closely associated with endothelial cell-derived VEGF and Noggin.

Breast cancer exosomes contribute to pre-metastatic niche formation and promote bone metastasis of tumor cells

Rationale: Breast cancer preferentially develops osteolytic bone metastasis, which makes patients suffer from pain, fractures and spinal cord compression. Accumulating evidences have shown that exosomes play an irreplaceable role in pre-metastatic niche formation as a communication messenger. However, the function of exosomes secreted by breast cancer cells remains incompletely understood in bone metastasis of breast cancer. Methods: Mouse xenograft models and intravenous injection of exosomes were applied for analyzing the role of breast cancer cell-derived exosomes in vivo. Effects of exosomes secreted by the mildly metastatic MDA231 and its subline SCP28 with highly metastatic ability on osteoclasts formation were confirmed by TRAP staining, ELISA, microcomputed tomography, histomorphometric analyses, and pit formation assay. The candidate exosomal miRNAs for promoting osteoclastogenesis were globally screened by RNA-seq. qRT-PCR, western blot, confocal microscopy, and RNA interfering were performed to validate the function of exosomal miRNA. Results: Implantation of SCP28 tumor cells in situ leads to increased osteoclast activity and reduced bone density, which contributes to the formation of pre-metastatic niche for tumor cells. We found SCP28 cells-secreted exosomes are critical factors in promoting osteoclast differentiation and activation, which consequently accelerates bone lesion to reconstruct microenvironment for bone metastasis. Mechanistically, exosomal miR-21 derived from SCP28 cells facilitates osteoclastogenesis through regulating PDCD4 protein levels. Moreover, miR-21 level in serum exosomes of breast cancer patients with bone metastasis is significantly higher than that in other subpopulations. Conclusion: Our results indicate that breast cancer cell-derived exosomes play an important role in promoting breast cancer bone metastasis, which is associated with the formation of pre-metastatic niche via transferring miR-21 to osteoclasts. The data from patient samples further reflect the significance of miR-21 as a potential target for clinical diagnosis and treatment of breast cancer bone metastasis.

Expression, purification and characterization of TMCO1 for structural studies

Transmembrane and coiled-coil domains 1 (TMCO1) has a highly conserved amino acid sequence among species, indicating a critical role of TMCO1 in cell physiology. The deficiency of TMCO1 in humans is associated with cerebrofaciothoracic dysplasia (CFTD), glaucoma, osteogenesis and the occurrence of cancer. TMCO1 was recently identified as an endoplasmic reticulum (ER) Ca²⁺ load-activated Ca²⁺ (CLAC) release channel, which prevents ER Ca²⁺ overload and maintains calcium homeostasis in the ER. However, the structural basis of the molecular function of TMCO1 channel remains elusive. To determine the structure of TMCO1, we screened the expression of TMCO1 in Escherichia coli and insect cell expression systems. TMCO1 from Dictyostelium discoideum (DdTMCO1) was successfully expressed in Escherichia coli with a high yield. The pure recombinant protein was obtained by affinity chromatography and size exclusion chromatography. The solution NMR of DdTMCO1 in DPC micelles showed three α-helical transmembrane regions.

miR-214 stimulated by IL-17A regulates bone loss in patients with ankylosing spondylitis

OBJECTIVE

Bone loss is common in AS, and miR-214 plays an important role in regulating bone formation. The aim of this study was to investigate the effect of miR-214, the production of which is stimulated by IL-17A, on bone loss in AS.

METHODS

Peripheral blood was obtained from 32 patients with AS and 24 healthy controls. Levels of IL-17A, soluble RANK ligand (RANKL) and osteoprotegerin in serum were evaluated by ELISA, and the relative level of miR-214 in serum was detected by real-time quantitative PCR. In addition, we assessed the relationship between levels of miR-214, IL-17A and bone loss in primary murine osteoblasts and mouse bone marrow cells.

RESULTS

The expression of RANKL and miR-214 in osteoblasts was increased following stimulation by IL-17A, and osteoblasts stimulated by IL-17A promoted the expression of miR-214 in osteoclasts and the activity of osteoclasts. We showed that osteoblast-derived miR-214 could be transferred to osteoclasts and could then regulate their activity. The levels of IL-17A and miR-214 were much higher in the serum of patients with AS than in that of healthy controls, and the relative level of miR-214 was positively correlated with the level of IL-17A in the serum and synovial fluid of the patients with AS, not healthy controls. The level of miR-214 in the serum of AS patients has potential diagnostic value.

CONCLUSION

The production of miR-214 in osteoblasts is stimulated by IL-17A. It is an important inhibitor of bone formation in AS, and the serum level of miR-214 might be of potential diagnostic value for AS.

An ER translocon for multi-pass membrane protein biogenesis

Membrane proteins with multiple transmembrane domains play critical roles in cell physiology, but little is known about the machinery coordinating their biogenesis at the endoplasmic reticulum. Here we describe a ~ 360 kDa ribosome-associated complex comprising the core Sec61 channel and five accessory factors: TMCO1, CCDC47 and the Nicalin-TMEM147-NOMO complex. Cryo-electron microscopy reveals a large assembly at the ribosome exit tunnel organized around a central membrane cavity. Similar to protein-conducting channels that facilitate movement of transmembrane segments, cytosolic and luminal funnels in TMCO1 and TMEM147, respectively, suggest routes into the central membrane cavity. High-throughput mRNA sequencing shows selective translocon engagement with hundreds of different multi-pass membrane proteins. Consistent with a role in multi-pass membrane protein biogenesis, cells lacking different accessory components show reduced levels of one such client, the glutamate transporter EAAT1. These results identify a new human translocon and provide a molecular framework for understanding its role in multi-pass membrane protein biogenesis.

N-(3-oxododecanoyl)-homoserine lactone regulates osteoblast apoptosis and differentiation by mediating intracellular calcium

Pseudomonas aeruginosa (P. aeruginosa) is associated with periapical periodontitis. The lesions are characterized by a disorder in osteoblast metabolism. Quorum sensing molecular N-(3-oxododecanoyl)-homoserine lactone (AHL) is secreted by P. aeruginosa and governs the expression of numerous virulence factors. AHL can trigger intracellular calcium ([Ca²⁺]_i) fluctuations in many host cells. However, it is unclear whether AHL can regulate osteoblast metabolism by affecting [Ca²⁺]_i changes or its spatial correlation. We explored AHL-induced apoptosis and differentiation in pre-osteoblastic MC3T3-E1 cells and evaluated [Ca²⁺]_i mobilization using several extraction methods. The spatial distribution pattern of [Ca²⁺]_i among cells was investigated by Moran's I, an index of spatial autocorrelation. We found that 30 μM and 50 μM AHL triggered opposing osteoblast fates. At 50 μM, AHL inhibited osteoblast differentiation by promoting mitochondrial-dependent apoptosis and negatively regulating osteogenic marker genes, including Runx2, Osterix, bone sialoprotein (Bsp), and osteocalcin (OCN). In contrast, prolonged treatment with 30 μM AHL promoted osteoblast differentiation concomitantly with cell apoptosis. The elevation of [Ca²⁺]_i levels in osteoblasts treated with 50 μM AHL was spatially autocorrelated, while no such phenomenon was observed in 30 μM AHL-treated osteoblasts. The blocking of cell-to-cell spatial autocorrelation in the osteoblasts provoked by 50 μM AHL significantly inhibited apoptosis and partially restored differentiation. Our observations suggest that AHL affects the fate of osteoblasts (apoptosis and differentiation) by affecting the spatial correlation of [Ca²⁺]_i changes. Thus, AHL acts as a double-edged sword for osteoblast function.

Alendronate loaded graphene oxide functionalized collagen sponge for the dual effects of osteogenesis and anti-osteoclastogenesis in osteoporotic rats

Graphene Oxide (GO)-related hydrogels have been extensively studied in hard tissue repair, because GO can not only enhance the mechanical properties of polymers but also promote osteogenic differentiation of mesenchymal stem cells. However, simple GO-related hydrogels are not ideal for the repair of osteoporotic bone defects as the overactive osteoclasts in osteoporosis. Alendronate (Aln) is known to inhibit osteoclasts and may bind to GO through covalent connection. Therefore, delivering Aln in GO-related hydrogels may be effective to repair osteoporotic bone defects. Here, we developed a control-released system which is constructed by collagen (Col)-GO sponges loaded with Aln (Col-GO-Aln) for osteoporotic bone defect repair. In vitro, Col-GO-Aln sponges prolonged the release period of Aln, and the sponge containing 0.05% (w/v) GO released Aln faster than sponge with 0.2% GO. Furthermore, tartrate-resistant acid phosphatase (TRAP) and F-actin staining demonstrated that Col-GO-Aln sponges effectively inhibited osteoclastogenesis of monocyte-macrophages. In vivo, micro-CT scan showed that the volume of newborn bone in defect site by 0.05% GO sponge was nearly three times larger than that of other groups. Moreover, the CT and histological examinations of rat femur proved that Col-GO-Aln sponges decreased the number of osteoclasts and suppressed the systemic bone loss in osteoporotic rats. These findings reveal that the application of GO as carriers of anti-osteoporosis drugs is a viable treatment for osteoporosis. The results also underscore the potential of GO-related hydrogels with Aln-releasing capacity for bone regeneration in osteoporosis.

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Alendronate-loading graphene oxide modified collagen sponge (Col-GO-Aln) exhibit a sustained drug delivery.

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Col-GO-Aln sponge showed active anti-osteoclastogenesis and osteogenesis ability in vitro and in situ repair.

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Col-GO-Aln sponge achieved a potential systemic resistance to bone loss in osteoporotic rats.

Bromodomain Protein BRD4 Accelerates Glucocorticoid Dysregulation of Bone Mass and Marrow Adiposis by Modulating H3K9 and Foxp1

Glucocorticoid provokes bone mass loss and fatty marrow, accelerating osteoporosis development. Bromodomain protein BRD4, an acetyl–histone-binding chromatin reader, regulates stem cell and tissue homeostasis. We uncovered that glucocorticoid inhibited acetyl Lys-9 at the histone 3 (H3K9ac)-binding Runx2 promoter and decreased osteogenic differentiation, whereas bromodomain protein 4 (BRD4) and adipocyte formation were upregulated in bone-marrow mesenchymal progenitor cells. BRD4 knockdown improved H3K9ac occupation at the Runx2 promoter and osteogenesis, but attenuated glucocorticoid-mediated adipocyte formation together with the unaffected H3K9ac-binding PPARγ2 promoter. BRD4 regulated epigenome related to fatty acid metabolism and the forkhead box P1 (Foxp1) pathway, which occupied the PPARγ2 promoter to modulate glucocorticoid-induced adipocytic activity. In vivo, BRD4 inhibitor JQ-1 treatment mitigated methylprednisolone-induced suppression of bone mass, trabecular microstructure, mineral acquisition, and osteogenic differentiation. Foxp1 signaling, marrow fat, and adipocyte formation in glucocorticoid-treated skeleton were reversed upon JQ-1 treatment. Taken together, glucocorticoid-induced H3K9 hypoacetylation augmented BRD4 action to Foxp1, which steered mesenchymal progenitor cells toward adipocytes at the cost of osteogenic differentiation in osteoporotic skeletons. BRD4 inhibition slowed bone mass loss and marrow adiposity. Collective investigations convey a new epigenetic insight into acetyl histone reader BRD4 control of osteogenesis and adipogenesis in skeleton, and highlight the remedial effects of the BRD4 inhibitor on glucocorticoid-induced osteoporosis.

Development of a decellularized porcine bone matrix for potential applications in bone tissue regeneration

Aim: The objectives of this study were to develop a new decellularized bone matrix (DBM) and to investigate its effect on the in vitro cell behavior of human bone marrow-derived mesenchymal stem cells (hMSCs), compared with porous β-tricalcium phosphate (β-TCP) scaffolds. Materials & methods: Triton X-100 and deoxycholate sodium solution, combining DNase I and RNase, were used to decellularize porcine bones. The DBM were then characterized by DNA contents and matrix components. hMSCs were then seeded on the DBM and β-TCP scaffolds to study cell behavior. Results: Results showed that most porcine cells were removed and the matrix components of the DBM were maintained. Cell culture results showed that DBM promoted cell attachment and proliferation of hMSCs but did not significantly promote the gene expression of osteogenic genes, compared with β-TCP scaffolds. Conclusion: DBM has similar function on cell behavior to β-TCP scaffolds that have promising potential in bone tissue regeneration.

Alteration of calcium signalling in cardiomyocyte induced by simulated microgravity and hypergravity

Objectives

Cardiac Ca²⁺ signalling plays an essential role in regulating excitation‐contraction coupling and cardiac remodelling. However, the response of cardiomyocytes to simulated microgravity and hypergravity and the effects on Ca²⁺ signalling remain unknown. Here, we elucidate the mechanisms underlying the proliferation and remodelling of HL‐1 cardiomyocytes subjected to rotation‐simulated microgravity and 4G hypergravity.

Materials and Methods

The cardiomyocyte cell line HL‐1 was used in this study. A clinostat and centrifuge were used to study the effects of microgravity and hypergravity, respectively, on cells. Calcium signalling was detected with laser scanning confocal microscopy. Protein and mRNA levels were detected by Western blotting and real‐time PCR, respectively. Wheat germ agglutinin (WGA) staining was used to analyse cell size.

Results

Our data showed that spontaneous calcium oscillations and cytosolic calcium concentration are both increased in HL‐1 cells after simulated microgravity and 4G hypergravity. Increased cytosolic calcium leads to activation of calmodulin‐dependent protein kinase II/histone deacetylase 4 (CaMKII/HDAC4) signalling and upregulation of the foetal genes ANP and BNP, indicating cardiac remodelling. WGA staining indicated that cell size was decreased following rotation‐simulated microgravity and increased following 4G hypergravity. Moreover, HL‐1 cell proliferation was increased significantly under hypergravity but not rotation‐simulated microgravity.

Conclusions

Our study demonstrates for the first time that Ca²⁺/CaMKII/HDAC4 signalling plays a pivotal role in myocardial remodelling under rotation‐simulated microgravity and hypergravity.

Polymeric sheet actuators with programmable bioinstructivity

Stem cells can be conceptualized as computational processors capable of sensing, processing, and converting environmental information (input) to yield a specific differentiation pathway (output). In this study, we employ a temperature-controlled polymer sheet actuator to interpret and transfer information, controlled by the material’s programming, to mesenchymal stem cells. The cell’s interpretation of mechanical, thermal, and biochemical signaling is shown to be dependent on the actuator’s activity, utilized to accelerate differentiation toward bone cells, further elucidating the role of microenvironmental parameters on mammalian cells. Our method provides a unique approach to processing two discrete stimuli into one biochemical signal, calcium ions, providing a basis for the logical control of the flow of biological signals and the design of cellular functions.

Stem cells are capable of sensing and processing environmental inputs, converting this information to output a specific cell lineage through signaling cascades. Despite the combinatorial nature of mechanical, thermal, and biochemical signals, these stimuli have typically been decoupled and applied independently, requiring continuous regulation by controlling units. We employ a programmable polymer actuator sheet to autonomously synchronize thermal and mechanical signals applied to mesenchymal stem cells (MSCs). Using a grid on its underside, the shape change of polymer sheet, as well as cell morphology, calcium (Ca²⁺) influx, and focal adhesion assembly, could be visualized and quantified. This paper gives compelling evidence that the temperature sensing and mechanosensing of MSCs are interconnected via intracellular Ca²⁺. Up-regulated Ca²⁺ levels lead to a remarkable alteration of histone H3K9 acetylation and activation of osteogenic related genes. The interplay of physical, thermal, and biochemical signaling was utilized to accelerate the cell differentiation toward osteogenic lineage. The approach of programmable bioinstructivity provides a fundamental principle for functional biomaterials exhibiting multifaceted stimuli on differentiation programs. Technological impact is expected in the tissue engineering of periosteum for treating bone defects.