Lysine-Specific Demethylase 1 (LSD1) epigenetically controls osteoblast differentiation

Discovery of TCP-(MP)-caffeic acid analogs as a new class of agents for treatment of osteoclastic bone loss

Inhibition of LSD1 was proposed as promising and attractive therapies for treating osteoporosis. Here, we synthesized a series of novel TCP-(MP)-Caffeic acid analogs as potential LSD1 inhibitors to assess their inhibitory effects on osteoclastogenesis by using TRAP-staining assay and try to explore the preliminary SAR. Among them, TCP-MP-CA (11a) demonstrated osteoclastic bone loss both in vitro and in vivo, showing a significant improvement in the in vivo effects compared to the LSD1 inhibitor GSK-LSD1. Additionally, we elucidated a mechanism that 11a and its precursor that 11e directly bind to LSD1/CoREST complex through FAD to inhibit LSD1 demethylation activity and influence its downstream IκB/NF-κB signaling pathway, and thus regulate osteoclastic bone loss. These findings suggested 11a or 11e as potential novel candidates for treating osteoclastic bone loss, and a concept for further development of TCP-(MP)-Caffeic acid analogs for therapeutic use in osteoporosis clinics.

Unlocking the potential of histone modification in regulating bone metabolism

Bone metabolism plays a crucial role in maintaining normal bone tissue homeostasis and function. Imbalances between bone formation and resorption can lead to osteoporosis, osteoarthritis, and other bone diseases. The dynamic and complex process of bone remodeling is driven by various factors, including epigenetics. Histone modification, one of the most important and well-studied components of epigenetic regulation, has emerged as a promising area of research in bone metabolism. Different histone proteins and modification sites exert diverse effects on osteogenesis and osteoclastogenesis. In this review, we summarize recent progress in understanding histone modifications in bone metabolism, including specific modification sites and potential regulatory enzymes. Comprehensive knowledge of histone modifications in bone metabolism could reveal new therapeutic targets and treatment strategies for bone diseases.

Lysine-specific demethylase 1 (LSD1) participate in porcine early embryonic development by regulating cell autophagy and apoptosis through the mTOR signaling pathway

Lysine-specific demethylase 1 (LSD1) stands as the pioneering histone demethylase uncovered, proficient in demethylating H3K4me1/2 and H3K9me1/2, thereby governing transcription and participating in cell apoptosis, proliferation, or differentiation. Nevertheless, the complete understanding of LSD1 during porcine early embryonic development and the underlying molecular mechanism remains unclear. Thus, we investigated the mechanism by which LSD1 plays a regulatory role in porcine early embryos. This study revealed that LSD1 inhibition resulted in parthenogenetic activation (PA) and in vitro fertilization (IVF) embryo arrested the development, and decreased blastocyst quality. Meanwhile, H3K4me1/2 and H3K9me1/2 methylase activity was increased at the 4-cell embryo stage. RNA-seq results revealed that autophagy related biological processes were highly enriched through GO and KEGG pathway analyses when LSD1 inhibition. Further studies showed that LSD1 depletion in porcine early embryos resulted in low mTOR and p-mTOR levels and high autophagy and apoptosis levels. The LSD1 deletion-induced increases in autophagy and apoptosis could be reversed by addition of mTOR activators. We further demonstrated that LSD1 inhibition induced mitochondrial dysfunction and mitophagy. In summary, our research results indicate that LSD1 may regulate autophagy and apoptosis through the mTOR pathway and affect early embryonic development of pigs.

Synergistic Interaction between Polysaccharide-Based Extracellular Matrix and Mineralized Osteoblast-Derived EVs Promotes Bone Regeneration via miRNA-mRNA Regulatory Axis

Extracellular vesicles (EVs) derived from bone progenitor cells are advantageous as cell-free and non-immunogenic cargo delivery vehicles. In this study, EVs are isolated from MC3T3-E1 cells before (GM-EVs) and after mineralization for 7 and 14 days (DM-EVs). It was observed that DM-EVs accelerate the process of differentiation in recipient cells more prominently. The small RNA sequencing of EVs revealed that miR-204-5p, miR-221-3p, and miR-148a-3p are among the highly upregulated miRNAs that have an inhibitory effect on the function of mRNAs, Sox11, Timp3, and Ccna2 in host cells, which is probably responsible for enhancing the activity of osteoblastic genes. To enhance the bioavailability of EVs, they are encapsulated in a chitosan-collagen composite hydrogel that serves as a bioresorbable extracellular matrix (ECM). The EVs-integrated scaffold (DM-EVs + Scaffold) enhances bone regeneration in critical-sized calvarial bone defects in rats within 8 weeks of implantation by providing the ECM cues. The shelf life of DM-EVs + Scaffold indicates that the bioactivity of EVs and their cargo in the polymer matrix remains intact for up to 30 days. Integrating mineralized cell-derived EVs into an ECM represents a bioresorbable matrix with a cell-free method for promoting new bone formation through the miRNA-mRNA regulatory axis.

Role of epigenetic regulatory mechanisms in age-related bone homeostasis imbalance

Alterations to the human organism that are brought about by aging are comprehensive and detrimental. Of these, an imbalance in bone homeostasis is a major outward manifestation of aging. In older adults, the decreased osteogenic activity of bone marrow mesenchymal stem cells and the inhibition of bone marrow mesenchymal stem cell differentiation lead to decreased bone mass, increased risk of fracture, and impaired bone injury healing. In the past decades, numerous studies have reported the epigenetic alterations that occur during aging, such as decreased core histones, altered DNA methylation patterns, and abnormalities in noncoding RNAs, which ultimately lead to genomic abnormalities and affect the expression of downstream signaling osteoporosis treatment and promoter of fracture healing in older adults. The current review summarizes the impact of epigenetic regulation mechanisms on age-related bone homeostasis imbalance.

Epigenetic regulators controlling osteogenic lineage commitment and bone formation

Bone formation and homeostasis are controlled by environmental factors and endocrine regulatory cues that initiate intracellular signaling pathways capable of modulating gene expression in the nucleus. Bone-related gene expression is controlled by nucleosome-based chromatin architecture that limits the accessibility of lineage-specific gene regulatory DNA sequences and sequence-specific transcription factors. From a developmental perspective, bone-specific gene expression must be suppressed during the early stages of embryogenesis to prevent the premature mineralization of skeletal elements during fetal growth in utero. Hence, bone formation is initially inhibited by gene suppressive epigenetic regulators, while other epigenetic regulators actively support osteoblast differentiation. Prominent epigenetic regulators that stimulate or attenuate osteogenesis include lysine methyl transferases (e.g., EZH2, SMYD2, SUV420H2), lysine deacetylases (e.g., HDAC1, HDAC3, HDAC4, HDAC7, SIRT1, SIRT3), arginine methyl transferases (e.g., PRMT1, PRMT4/CARM1, PRMT5), dioxygenases (e.g., TET2), bromodomain proteins (e.g., BRD2, BRD4) and chromodomain proteins (e.g., CBX1, CBX2, CBX5). This narrative review provides a broad overview of the covalent modifications of DNA and histone proteins that involve hundreds of enzymes that add, read, or delete these epigenetic modifications that are relevant for self-renewal and differentiation of mesenchymal stem cells, skeletal stem cells and osteoblasts during osteogenesis.

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.

Protein arginine methyltransferases PRMT1, PRMT4/CARM1 and PRMT5 have distinct functions in control of osteoblast differentiation

Osteogenic differentiation of mesenchymal cells is controlled by epigenetic enzymes that regulate post-translational modifications of histones. Compared to acetyl or methyltransferases, the physiological functions of protein arginine methyltransferases (PRMTs) in osteoblast differentiation remain minimally understood. Therefore, we surveyed the expression and function of all nine mammalian PRMT members during osteoblast differentiation. RNA-seq gene expression profiling shows that Prmt1, Prmt4/Carm1 and Prmt5 represent the most prominently expressed PRMT subtypes in mouse calvarial bone and MC3T3 osteoblasts as well as human musculoskeletal tissues and mesenchymal stromal cells (MSCs). Based on effects of siRNA depletion, it appears that PRMT members have different functional effects: (i) loss of Prmt1 stimulates and (ii) loss of Prmt5 decreases calcium deposition of mouse MC3T3 osteoblasts, while (iii) loss of Carm1 is inconsequential for calcium deposition. Decreased Prmt5 suppresses expression of multiple genes involved in mineralization (e.g., Alpl, Ibsp, Phospho1) consistent with a positive role in osteogenesis. Depletion of Prmt1, Carm1 and Prmt5 has intricate but modest time-dependent effects on the expression of a panel of osteoblast differentiation and proliferation markers but does not change mRNA levels for select epigenetic regulators (e.g., Ezh1, Ezh2, Brd2 and Brd4). Treatment with the Class I PRMT inhibitor GSK715 enhances extracellular matrix mineralization of MC3T3 cells, while blocking formation of H3R17me2a but not H4R3me2a marks. In sum, Prmt1, Carm1 and Prmt5 have distinct biological roles during osteoblast differentiation, and different types histone H3 and H4 arginine methylation may contribute to the chromatin landscape during osteoblast differentiation.

G-protein coupled receptor 5C (GPRC5C) is required for osteoblast differentiation and responds to EZH2 inhibition and multiple osteogenic signals

Osteoblast differentiation is epigenetically suppressed by the H3K27 methyltransferase EZH2, and induced by the morphogen BMP2 and transcription factor RUNX2. These factors also regulate distinct G protein coupled receptors (GPRCs; e.g., PTH1R, GPR30/GPER1). Because GPRCs transduce many physiological stimuli, we examined whether BMP2 or EZH2 inhibition (i.e., GSK126) regulates other GPRC genes in osteoblasts. RNA-seq screening of >400 mouse GPRC-related genes showed that many GPRCs are downregulated during osteogenic differentiation. The orphan receptor GPRC5C, along with a small subset of other GPRCs, is induced by BMP2 or GSK126 during Vitamin C dependent osteoblast differentiation, but not by all-trans retinoic acid. ChIP-seq analysis revealed that GSK126 reduces H3K27me3 levels at the GPRC5C gene locus in differentiating MC3T3-E1 osteoblasts, consistent with enhanced GPRC5C mRNA expression. Loss of function analyses revealed that shRNA-mediated depletion of GPRC5C decreases expression of bone markers (e.g., BGLAP and IBSP) and mineral deposition in response to BMP2 or GSK126. GPRC5C mRNA was found to be reduced in the osteopenic bones of KLF10 null mice which have compromised BMP2 signaling. GPRC5C mRNA is induced by the bone-anabolic activity of 17β-estradiol in trabecular but not cortical bone following ovariectomy. Collectively, these findings suggest that GPRC5C protein is a key node in a pro-osteogenic axis that is normally suppressed by EZH2-mediated H3K27me3 marks and induced during osteoblast differentiation by GSK126, BMP2, and/or 17β-estradiol. Because GPRC5C protein is an understudied orphan receptor required for osteoblast differentiation, identification of ligands that induce GPRC5C signaling may support therapeutic strategies to mitigate bone-related disorders.

Atf7ip Inhibits Osteoblast Differentiation via Negative Regulation of the Sp7 Transcription Factor

Epigenetic modifications are critical for cell differentiation and growth. As a regulator of H3K9 methylation, Setdb1 is implicated in osteoblast proliferation and differentiation. The activity and nucleus localization of Setdb1 are regulated by its binding partner, Atf7ip. However, whether Atf7ip is involved in the regulation of osteoblast differentiation remains largely unclear. In the present study, we found that Atf7ip expression was upregulated during the osteogenesis of primary bone marrow stromal cells and MC3T3-E1 cells, and was induced in PTH-treated cells. The overexpression of Atf7ip impaired osteoblast differentiation in MC3T3-E1 cells regardless of PTH treatment, as measured by the expression of osteoblast differentiation markers, Alp-positive cells, Alp activity, and calcium deposition. Conversely, the depletion of Atf7ip in MC3T3-E1 cells promoted osteoblast differentiation. Compared with the control mice, animals with Atf7ip deletion in the osteoblasts (Oc-Cre;Atf7ip^f/f) showed more bone formation and a significant increase in the bone trabeculae microarchitecture, as reflected by μ-CT and bone histomorphometry. Mechanistically, Atf7ip contributed to the nucleus localization of Setdb1 in MC3T3-E1, but did not affect Setdb1 expression. Atf7ip negatively regulated Sp7 expression, and through specific siRNA, Sp7 knockdown attenuated the enhancing role of Atf7ip deletion in osteoblast differentiation. Through these data, we identified Atf7ip as a novel negative regulator of osteogenesis, possibly via its epigenetic regulation of Sp7 expression, and demonstrated that Atf7ip inhibition is a potential therapeutic measure for enhancing bone formation.

Crucial Role of Lysine-Specific Histone Demethylase 1 in RANKL-Mediated Osteoclast Differentiation

Epigenetic regulators are involved in osteoclast differentiation. This study proposes that the inhibitors of epigenetic regulators could be effective in the treatment of osteoporosis. This study identified GSK2879552, a lysine-specific histone demethylase 1 (LSD1) inhibitor, as a candidate for the treatment of osteoporosis from epigenetic modulator inhibitors. We investigate the function of LSD1 during RANKL-induced osteoclast formation. LSD1 small-molecule inhibitors effectively inhibit the RANKL-induced osteoclast differentiation in a dose-dependent manner. LSD1 gene knockout in macrophage cell line Raw 264.7 also inhibits RANKL-mediated osteoclastogenesis. LSD1-inhibitor-treated primary macrophage cells and LSD1 gene knockout Raw 264.7 cells failed to show actin ring formation. LSD1 inhibitors prevent the expression of RANKL-induced osteoclast-specific genes. They also downregulated the protein expression of osteoclast-related markers in osteoclastogeneses, such as Cathepsin K, c-Src, and NFATc1. Although LSD1 inhibitors were shown to reduce the in vitro demethylation activity of LSD1, they did not modulate the methylation of Histone 3 K4 and K9 during osteoclastogenesis. The ovariectomy (OVX)-induced osteoporosis model revealed that GSK2879552 slightly restores OVX-induced cortical bone loss. LSD1 can be employed as a positive regulator to promote osteoclast formation. Hence, inhibition of LSD1 activities is a potential target for preventing bone diseases characterized by excessive osteoclast activities.

Lysine specific demethylase 1 is a molecular driver and therapeutic target in sarcoma

Sarcomas are a diverse group of tumors with numerous oncogenic drivers, and display varied clinical behaviors and prognoses. This complexity makes diagnosis and the development of new and effective treatments challenging. An incomplete understanding of both cell of origin and the biological drivers of sarcomas complicates efforts to develop clinically relevant model systems and find new molecular targets. Notably, the histone lysine specific demethylase 1 (LSD1) is overexpressed in a number of different sarcomas and is a potential therapeutic target in these malignancies. With the ability to modify histone marks, LSD1 is a key player in many protein complexes that epigenetically regulate gene expression. It is a largely context dependent enzyme, having vastly different and often opposing roles depending on the cellular environment and which interaction partners are involved. LSD1 has been implicated in the development of many different types of cancer, but its role in bone and soft tissue sarcomas remains poorly understood. In this review, we compiled what is known about the LSD1 function in various sarcomas, to determine where knowledge is lacking and to find what theme emerge to characterize how LSD1 is a key molecular driver in bone and soft tissue sarcoma. We further discuss the current clinical landscape for the development of LSD1 inhibitors and where sarcomas have been included in early clinical trials.

CircRNA AFF4 induced by KDM1A promotes osteogenic differentiation through FNDC5/Irisin pathway

Background

Circular RNA (circ) AFF4 was documented to regulate osteogenesis but the underlying mechanism remains to be elucidated. The preliminary study showed that circ_AFF4 may promote osteogenesis via FNDC5/Irisin. Furthermore, the online prediction tool indicated the interaction of circ_AFF4, insulin-like growth factor-2 mRNA-binding protein 3 (IGF2BP3), FNDC5 and lysine (K)-specific demethylase 1 A (KDM1A). Therefore, this study aims to elucidate the relationships of KDM1A, circ_AFF4, IGF2BP3 and FNDC5/Irisin during osteogenesis.

Methods

The alkaline phosphatase (ALP) activities and osteogenic-related factors were determined using ALP and alizarin red S (ARS) staining, real-time quantitative PCR(RT-qPCR) and western blot. Immunoprecipitation (RIP), pull-down assay and fluorescence in situ hybridization (FISH) were used to examine the interactions among circ_AFF4/IGF2BP3/FNDC5. A mouse in vivo model was utilized to further confirm the regulatory effect on bone formation.

Results

Circ_AFF4 and KDM1A expression levels were increased during osteoinduction of BM-MSCs. Knockdown of circ_AFF4 and KDM1A significantly suppressed BM-MSC osteogenesis. We also proved that KDM1A directly bound to circ_AFF4 and FNDC5 promoter and induced circ_AFF4 and FNDC5 expression. Furthermore, circ_AFF4 enhanced the stability of FNDC5 by generating a circ_AFF4, IGF2BP3 and FNDC5 RNA-protein complex, and thereby induced Irisin and osteogenesis. The in vitro data was confirmed with in vivo model.

Conclusion

These findings elucidate that KDM1A induces circ_AFF4, which promotes promote osteogenesis via IGF2BP3. This study indicates that circ_AFF4 may potentially represent a critical therapeutic target for the diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00557-7.

Oncogenic roles of LINC01234 in various forms of human cancer

Abnormal expression of long non-coding RNAs (lncRNAs) plays an essential role in various malignant neoplasia. As a newly identified lncRNA, LINC01234 is abnormally expressed in several types of cancers and promotes the development of cancers. Accumulating evidence indicates that overexpression of LINC01234 is associated with poor clinical outcomes. Moreover, LINC01234 modulates many cellular events as a putative proto-oncogene, including proliferation, migration, invasion, apoptosis, cell cycle progression, and EMT. In terms of molecular mechanism, LINC01234 regulates gene expression by acting as ceRNA, participating in signaling pathways, interacting with proteins and other molecules, and encoding polypeptide. It reveals that LINC01234 may serve as a potential biomarker for cancer diagnosis, treatment, and prognosis. This review summarizes the expression pattern, biological function, and molecular mechanism of LINC01234 in human cancer and discusses its potential clinical utility.