JMJD3 activated hyaluronan synthesis drives muscle regeneration in an inflammatory environment

Exosomes derived from adipose-derived stem cells alleviate acute radiation-induced dermatitis through up-regulating hyaluronic acid synthase 1 expression

BACKGROUND

Acute radiation-induced dermatitis refers to skin lesions that usually appear within 90 days of the start of radiotherapy. Although various treatments are available, none have proven fully effective. Exosomes produced by adipose-derived stem cells play crucial roles in enhancing cell regeneration, promoting angiogenesis, regulating inflammation and remodeling the extracellular matrix. Hyaluronic acid, a major extracellular matrix component, is synthesized by hyaluronic acid synthase, with hyaluronic acid synthase 1 being particularly critical for skin repair. This study aimed to investigate whether exosomes derived from adipose-derived stem cells can protect against radiation-induced acute skin damage and to elucidate the underlying mechanisms involving hyaluronic acid synthase 1.

METHODS

Thirty-six male adult SD rats were randomly divided into a negative control group, an irradiation group (90 Gy), and a radiation + exosomes group (90 Gy + 100 ug exosomes). Three groups of fibroblasts were assigned: one for control, one for radiation (6 Gy), and one for radiation plus exosomes (6 Gy + 4 ug exosomes). The effect of ADSC-exos transplantation was evaluated using skin damage score, histopathological analysis, electron microscopy, immunohistochemical staining, immunofluorescence staining, and immunoblotting analysis. Furthermore, small interfering RNA-mediated knockdown of hyaluronic acid synthase 1 was performed to explore its regulatory role in the TGF-β/Smad2/3 signaling pathway.

RESULTS

After irradiation, the ADSC-exos intervention significantly increased the levels of stromal cell-derived factor-1, matrix metalloproteinases, transforming growth factor, basic fibroblast growth factor, platelet-derived growth factor, vascular endothelial growth factor, interleukin 10, interleukin 12, and reduced the expression of the pro-inflammatory factor interleukin 6. Notably, exosomes treatment markedly upregulated hyaluronic acid synthase 1 expression, and small interfering RNA-mediated knockdown of hyaluronic acid synthase 1 resulted in reduced phosphorylation of TGF-β/Smad2/3 signaling components, indicating that hyaluronic acid synthase 1 is a critical mediator of this pathway.

CONCLUSION

Exosomes derived from adipose-derived stem cells alleviate acute radiation-induced dermatitis by enhancing hyaluronic acid synthase 1 expression and activating the TGF-β/Smad2/3 pathway, thereby promoting skin regeneration and repair. These findings suggest that exosomes derived from adipose-derived stem cells may serve as a promising cell-free therapeutic strategy for the prevention and treatment of acute radiation-induced dermatitis.

Roles of Kdm6a and Kdm6b in Regulation of Mammalian Neural Regeneration

Epigenetic regulation of neuronal transcriptomic landscape is emerging to be a key coordinator of mammalian neural regeneration. The roles of two histone 3 lysine 27 (H3K27) demethylases, Kdm6a/b, in controlling neuroprotection and axon regeneration are investigated here. Deleting either Kdm6a or Kdm6b leads to enhanced sensory axon regeneration in the peripheral nervous system (PNS), whereas in the central nervous system (CNS), only deleting Kdm6a in retinal ganglion cells (RGCs) significantly enhances optic nerve regeneration. Moreover, both Kdm6a and Kdm6b function to regulate RGC survival but with different mechanisms. Mechanistically, Kdm6a regulates RGC regeneration via distinct pathway from that of Pten, and co-deleting Kdm6a and Pten results in long distance optic nerve regeneration passing the optic chiasm. In addition, RNA-seq profiling reveals that Kdm6a deletion switches the RGC transcriptomics into a developmental-like state and suppresses several known repressors of neural regeneration. Klf4 is identified as a direct downstream target of Kdm6a-H3K27me3 signaling in both sensory neurons and RGCs to regulate axon regeneration. These findings not only reveal different roles of Kdm6a and Kdm6b in regulation of neural regeneration and their underlying mechanisms, but also identify Kdm6a-mediated histone demethylation signaling as a novel epigenetic target for supporting CNS neural regeneration.

Nature-derived microneedles with metal-polyphenolic networks encapsulation for chronic soft tissue defects repair: Responding and remodeling the regenerative microenvironment

The treatment outcomes of traditional patches for chronic soft tissue defects (CSTDs) are unsatisfactory in clinical, owing to the lack of intrinsic bioactivities to orchestrate the intricate regenerative process. To tackle this deficiency, nature-derived microneedles (NMs) composed of silk methacrylate and snail mucus are developed in this study. The resultant NMs have excellent mechanical strength and biological adhesiveness, ensuring suture-free but reliable fixation on implanted site. To enhance the intrinsic bioactivities, metal-polyphenolic networks (MPNs) coordinated from copper (Cu) and curcumin (Cur) are designed and encapsulated into NMs. Cu-Cur MPNs harness the anti-oxidative and anti-inflammatory properties of Cur with the pro-angiogenic properties of Cu, targeting different negative aspects in CSTDs repair. Furthermore, the pH-responsive disassembly of Cu-Cur MPNs can respond to the acidic microenvironment, allowing for burst-free and on-demand drug delivery. Both in-vitro and in-vivo experiments demonstrate that NMs with Cu-Cur MPNs encapsulation (Cu-Cur-NMs) can restore redox homeostasis, reduce inflammatory response, and promote blood vessel formation, thus remodeling the regenerative microenvironment to greatly improve the repair quality of CSTDs. Therefore, the combined advantages of microneedles-based patch system and MPNs-based nanotherapeutic agent are explored for the first time, and our proposed Cu-Cur-NMs represent a multifunctional and promising device for CSTDs repair.

Regulation of histone H3K27 methylation in inflammation and cancer

Inflammation is a multifaceted defense mechanism of the immune system against infection. Chronic inflammation is intricately linked to all stages of tumorigenesis and is therefore associated with an elevated risk of developing serious cancers. Epigenetic mechanisms have the capacity to trigger inflammation as well as facilitate tumor development and transformation within an inflammatory context. They achieve this by dynamically modulating the expression of both pro-inflammatory and anti-inflammatory cytokines, which in turn sustains chronic inflammation. The aberrant epigenetic landscape reconfigures the transcriptional programs of inflammatory and oncogenic genes. This reconfiguration is pivotal in dictating the biological functions of both tumor cells and immune cells. Aberrant histone H3 lysine 27 site (H3K27) methylation has been shown to be involved in biological behaviors such as inflammation development, tumor progression, and immune response. The establishment and maintenance of this repressive epigenetic mark is dependent on the involvement of the responsible histone modifying enzymes enhancer of zeste homologue 2 (EZH2), jumonji domain containing 3 (JMJD3) and ubiquitously transcribed tetratricopeptide repeat gene X (UTX) as well as multiple cofactors. In addition, specific pharmacological agents have been shown to modulate H3K27 methylation levels, thereby modulating inflammation and carcinogenesis. This review comprehensively summarises the current characteristics and clinical significance of epigenetic regulation of H3K27 methylation in the context of inflammatory response and tumor progression.

Andrias davidianus Derived Glycosaminoglycans Direct Diabetic Wound Repair by Reprogramming Reparative Macrophage Glucolipid Metabolism

Harnessing cross-species regenerative cues to direct human regenerative potential is increasingly recognized as an excellent strategy in regenerative medicine, particularly for addressing the challenges of impaired wound healing in aging populations. The skin mucus of Andrias davidianus plays a critical role in self-protection and tissue repair, yet the fundamental regenerative factors and mechanisms involved remain elusive. Here, this work presents evidence that glycosaminoglycans (GAGs) derived from the skin secretion of Andrias davidianus (SAGs) serve as potent mediators of angiogenesis and inflammatory remodeling, facilitating efficient healing of diabetic wounds. Mechanistic studies reveal that SAGs promote macrophage polarization toward an anti-inflammatory and pro-regenerative phenotype (CD206+/Arg1+) via glucolipid metabolic reprogramming. This process suppresses excessive inflammation and enhances the expression of VEGF and IL-10 to create a facilitative microenvironment for tissue regeneration. Additionally, this work develops SAGs-GelMA composite microspheres that address multiple stages of wound healing, including rapid hemostasis, exudate control, and activation of endogenous regenerative processes. This engineered approach significantly improves the scarless healing of diabetic wounds by facilitating the recruitment and activation of reparative macrophages. The findings offer new insights into the regenerative mechanisms of Andrias davidianus and highlight the potential therapeutic application of SAGs in tissue repair.

Skeletal muscle stem cells modulate niche function in Duchenne muscular dystrophy mouse through YY1-CCL5 axis

Adult skeletal muscle stem cells (MuSCs) are indispensable for muscle regeneration and tightly regulated by macrophages (MPs) and fibro-adipogenic progenitors (FAPs) in their niche. Deregulated MuSC/MP/FAP interactions and the ensuing inflammation and fibrosis are hallmarks of dystrophic muscle. Here we demonstrate intrinsic deletion of transcription factor Yin Yang 1 (YY1) in MuSCs exacerbates dystrophic pathologies by altering composition and heterogeneity of MPs and FAPs. Further analysis reveals YY1 loss induces expression of immune genes in MuSCs, including C-C motif chemokine ligand 5 (Ccl5). Augmented CCL5 secretion promotes MP recruitment via CCL5/C-C chemokine receptor 5 (CCR5) crosstalk, which subsequently hinders FAP clearance through elevated Transforming growth factor-β1 (TGFβ1). Maraviroc-mediated pharmacological blockade of the CCL5/CCR5 axis effectively mitigates muscle dystrophy and improves muscle performance. Lastly, we demonstrate YY1 represses Ccl5 transcription by binding to its enhancer thus facilitating promoter-enhancer looping. Altogether, our study demonstrates the critical role of MuSCs in actively shaping their niche and provides novel insight into the therapeutic intervention of muscle dystrophy.

Metabolic regulation in adult and aging skeletal muscle stem cells

Adult stem cells maintain homeostasis and enable regeneration of most tissues. Quiescence, proliferation, and differentiation of stem cells and their progenitors are tightly regulated processes governed by dynamic transcriptional, epigenetic, and metabolic programs. Previously thought to merely reflect a cell's energy state, metabolism is now recognized for its critical regulatory functions, controlling not only energy and biomass production but also the cell's transcriptome and epigenome. In this review, we explore how metabolic pathways, metabolites, and transcriptional and epigenetic regulators are functionally interlinked in adult and aging skeletal muscle stem cells.

Endogenous Fe2+-triggered self-targeting nanomicelles for self-amplifying intracellular oxidative stress

BACKGROUND

Artesunate (ASA) acts as an •O₂- source through the breakdown of endoperoxide bridges catalyzed by Fe2+, yet its efficacy in ASA-based nanodrugs is limited by poor intracellular delivery.

METHODS

ASA-hyaluronic acid (HA) conjugates were formed from hydrophobic ASA and hydrophilic HA by an esterification reaction first, and then self-targeting nanomicelles (NM) were developed using the fact that the amphiphilic conjugates of ASA and HA are capable of self-assembling in aqueous environments.

RESULTS

These ASA-HA NMs utilize CD44 receptor-mediated transcytosis to greatly enhance uptake by breast cancer cells. Subsequently, endogenous Fe2+ from the tumor catalyzes the released ASA to produce highly toxic •O₂- radicals to kill tumor cells, although sustained tumor growth inhibition can be achieved via in vivo experiments.

CONCLUSIONS

Self-targeting NMs represent a promising strategy for enhancing ASA-based treatments, leveraging clinically approved drugs to expedite drug development and clinical research in oncology.

Report on the 6th Ottawa International Conference on Neuromuscular Disease & Biology - September 7-9, 2023, Ottawa, Canada

The 6th Ottawa International Conference in Neuromuscular Disease and Biology was held on September 7-9, 2023 in Ottawa, Canada. The goal of the conference was to assemble international experts in fundamental science, translational medicine and clinical neuromuscular disease research. Speakers provided attendees with updates on a wide range of topics related to neuromuscular disease and biology, including methods to identify novel diseases, recent developments in muscle, motor neuron and stem cell biology, expanded disease pathogenesis of known diseases, and exciting advances in therapy development. A summary of the major topics and results presented by these speakers is provided.

Caspase-Activated DNase localizes to cancer causing translocation breakpoints during cell differentiation

Caspase activated DNase (CAD) induced DNA breaks promote cell differentiation and therapy-induced cancer cell resistance. CAD targeting activity is assumed to be unique to each condition, as differentiation and cancer genesis are divergent cell fates. Here, we made the surprising discovery that a subset of CAD-bound targets in differentiating muscle cells are the same genes involved in the genesis of cancer-causing translocations. In muscle cells, a prominent CAD-bound gene pair is Pax7 and Foxo1a, the mismatched reciprocal loci that give rise to alveolar rhabdomyosarcoma. We show that CAD-targeted breaks in the Pax7 gene are physiologic to reduce Pax7 expression, a prerequisite for muscle cell differentiation. A cohort of these CAD gene targets are also conserved in early differentiating T cells and include genes that spur leukemia/lymphoma translocations. Our results suggest the CAD targeting of translocation prone oncogenic genes is non-pathologic biology and aligns with initiation of cell fate transitions.

Integrating Physical and Biochemical Cues for Muscle Engineering: Scaffolds and Graft Durability

Muscle stem cells (MuSCs) are essential for skeletal muscle regeneration, influenced by a complex interplay of mechanical, biochemical, and molecular cues. Properties of the extracellular matrix (ECM) such as stiffness and alignment guide stem cell fate through mechanosensitive pathways, where forces like shear stress translate into biochemical signals, affecting cell behavior. Aging introduces senescence which disrupts the MuSC niche, leading to reduced regenerative capacity via epigenetic alterations and metabolic shifts. Transplantation further challenges MuSC viability, often resulting in fibrosis driven by dysregulated fibro-adipogenic progenitors (FAPs). Addressing these issues, scaffold designs integrated with pharmacotherapy emulate ECM environments, providing cues that enhance graft functionality and endurance. These scaffolds facilitate the synergy between mechanotransduction and intracellular signaling, optimizing MuSC proliferation and differentiation. Innovations utilizing human pluripotent stem cell-derived myogenic progenitors and exosome-mediated delivery exploit bioactive properties for targeted repair. Additionally, 3D-printed and electrospun scaffolds with adjustable biomechanical traits tackle scalability in treating volumetric muscle loss. Advanced techniques like single-cell RNA sequencing and high-resolution imaging unravel muscle repair mechanisms, offering precise mapping of cellular interactions. Collectively, this interdisciplinary approach fortifies tissue graft durability and MuSC maintenance, propelling therapeutic strategies for muscle injuries and degenerative diseases.

The roles of hyaluronan in kidney development, physiology and disease

The hyaluronan (HA) matrix in the tissue microenvironment is crucial for maintaining homeostasis by regulating inflammatory signalling, endothelial-mesenchymal transition and cell migration. During development, covalent modifications and osmotic swelling of HA create mechanical forces that initiate midgut rotation, vascular patterning and branching morphogenesis. Together with its main cell surface receptor, CD44, HA establishes a physicochemical scaffold at the cell surface that facilitates the interaction and clustering of growth factors and receptors that is required for normal physiology. High-molecular-weight HA, tumour necrosis factor-stimulated gene 6, pentraxin 3 and CD44 form a stable pericellular matrix that promotes tissue regeneration and reduces inflammation. By contrast, breakdown of high-molecular-weight HA into depolymerized fragments by hyaluronidases triggers inflammatory signalling, leukocyte migration and angiogenesis, contributing to tissue damage and fibrosis in kidney disease. Targeting HA metabolism is challenging owing to its dynamic regulation and tissue-specific functions. Nonetheless, modulating HA matrix functions by targeting its binding partners holds promise as a therapeutic strategy for restoring tissue homeostasis and mitigating pathological processes. Further research in this area is warranted to enable the development of novel therapeutic approaches for kidney and other diseases characterized by dysregulated HA metabolism.

AGEs impair osteogenesis in orthodontic force-induced periodontal ligament stem cells through the KDM6B/Wnt self-reinforcing loop

BACKGROUND

Diabetes, occasionally diagnosed in orthodontic patients, can impede orthodontic tooth movement (OTM) by accumulating advanced glycation end products (AGEs) in the periodontium. This accumulation impairs the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) due to alterations in the force-loaded microenvironment, yet the underlying mechanisms remain elusive.

METHODS

Bioinformatics analysis of GSE112122 identified alterations in the mechanical regulation of histone methylation enzyme Lysine Demethylase 6B (KDM6B). OTM models were established in healthy and Nicotinamide/ Streptozotocin-induced type II diabetic rats. The impact of AGEs on mechanically induced osteogenesis and its correlation with KDM6B were evaluated by assessing the therapeutic effects of periodontal ligament injections of the AGEs/RAGE inhibitor FPS-ZM1. To investigate transcriptomic changes, we extracted human PDLSCs, which were subjected to RNA sequencing following the overexpression of KDM6B. Experimental validation further identified potential self-reinforcing loops and their associated antioxidative mechanisms.

RESULTS

Mechanical forces upregulated KDM6B expression and function in PDLSCs, modulating extensive downstream osteogenesis-related transcriptional changes. Experiments with AGEs-treated and FPS-ZM1-treated samples demonstrated that AGEs impaired osteogenesis by compromising KDM6B mechanical responsiveness. A positive feedback loop between KDM6B and Wnt pathways was identified, inhibited by AGEs. This loop regulated superoxide dismutase 2 (SOD2), facilitating antioxidative stress and preventing stem cell ageing.

CONCLUSIONS

This study elucidates a novel mechanism by which AGEs influence the osteogenic process and antioxidative capacity of PDLSCs through the KDM6B/Wnt self-reinforcing loop under orthodontic force. Targeting the AGE/RAGE pathway or enhancing KDM6B may enhance orthodontic treatments for diabetic patients.

Manual Therapy Exerts Local Anti-Inflammatory Effects Through Neutrophil Clearance

Background: Manual therapy (MT) has been widely used in China to treat local tissue inflammation for a long time. However, there is a lack of scientific evidence for using MT in anti-inflammatory therapy, and its anti-inflammatory mechanism needs further clarification. Methods: We utilized MT to treat cardiotoxin (CTX) injury-induced skeletal muscle inflammation in C57BL6/J mice. We analyzed the underlying mechanism by integrating single-cell RNA sequencing (scRNA-seq) with molecular techniques. Hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining were used to assess skeletal muscle inflammation and muscle fiber cross-sectional area (CSA). scRNA-seq, immunofluorescence, and western blot were performed to determine cellular and molecular outcome changes. Results: Compared with CTX injury-induced skeletal muscle inflammatory mice, MT intervention significantly reduced proinflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α) expression levels; scRNA-seq detected that neutrophil numbers and activity were maximum proportions increased in injured skeletal muscle among macrophage, T cells, B cells, endothelial cells, fast muscle cells, fibroblasts, and skeletal muscle satellite cells; and S100A9 gene expression was supreme in neutrophils. However, after treatment with MT, S100A9 protein expression and the numbers and activity of Ly6g+/Mpo+ neutrophils were significantly inhibited, thus reducing the inflammatory cytokine levels and exerting an anti-inflammatory effect by early clearing neutrophils. Conclusion: MT can mitigate localized inflammation induced by injured skeletal muscle, achieved by decreasing S100A9 protein expression and clearing neutrophils in mice, which may help advance therapeutic strategies for skeletal muscle localized inflammation.

Platelet-Rich Plasma Promotes the Expansion of Human Myoblasts and Favors the In Vitro Generation of Human Muscle Reserve Cells in a Deeper State of Quiescence

Stem cell therapy holds significant potential for skeletal muscle repair, with in vitro-generated human muscle reserve cells (MuRCs) emerging as a source of quiescent myogenic stem cells that can be injected to enhance muscle regeneration. However, the clinical translation of such therapies is hampered by the need for fetal bovine serum (FBS) during the in vitro generation of human MuRCs. This study aimed to determine whether fresh allogeneic human platelet-rich plasma (PRP) combined or not with hyaluronic acid (PRP-HA) could effectively replace xenogeneic FBS for the ex vivo expansion and differentiation of human primary myoblasts. Cells were cultured in media supplemented with either PRP or PRP-HA and their proliferation rate, cytotoxicity and myogenic differentiation potential were compared with those cultured in media supplemented with FBS. The results showed similar proliferation rates among human myoblasts cultured in PRP, PRP-HA or FBS supplemented media, with no cytotoxic effects. Human myoblasts cultured in PRP or PRP-HA showed reduced fusion ability upon differentiation. Nevertheless, we also observed that human MuRCs generated from PRP or PRP-HA myogenic cultures, exhibited increased Pax7 expression and delayed re-entry into the cell cycle upon reactivation, indicating a deeper quiescent state of human MuRCs. These results suggest that allogeneic human PRP effectively replaces FBS for the ex vivo expansion and differentiation of human myoblasts and favors the in vitro generation of Pax7High human MuRCs, with important implications for the advancement of stem cell-based muscle repair strategies.

Multimodal smart systems reprogramme macrophages and remove urate to treat gouty arthritis

Gouty arthritis is a chronic and progressive disease characterized by high urate levels in the joints and by an inflammatory immune microenvironment. Clinical data indicate that urate reduction therapy or anti-inflammatory therapy alone often fails to deliver satisfactory outcomes. Here we have developed a smart biomimetic nanosystem featuring a 'shell' composed of a fusion membrane derived from M2 macrophages and exosomes, which encapsulates liposomes loaded with a combination of uricase, platinum-in-hyaluronan/polydopamine nanozyme and resveratrol. The nanosystem targets inflamed joints and promotes the accumulation of anti-inflammatory macrophages locally, while the uricase and the nanozyme reduce the levels of urate within the joints. Additionally, site-directed near-infrared irradiation provides localized mild thermotherapy through the action of platinum and polydopamine, initiating heat-induced tissue repair. Combined use of these components synergistically enhances overall outcomes, resulting in faster recovery of the damaged joint tissue.

Hyaluronic Acid Receptor-Mediated Nanomedicines and Targeted Therapy

Hyaluronic acid (HA) is a naturally occurring polysaccharide found in the extracellular matrix with broad applications in disease treatment. HA possesses good biocompatibility, biodegradability, and the ability to interact with various cell surface receptors. Its wide range of molecular weights and modifiable chemical groups make it an effective drug carrier for drug delivery. Additionally, the overexpression of specific receptors for HA on cell surfaces in many disease states enhances the accumulation of drugs at pathological sites through receptor binding. In this review, the modification of HA with drugs, major receptor proteins, and the latest advances in receptor-targeted nano drug delivery systems (DDS) for the treatment of tumors and inflammatory diseases are summarized. Furthermore, the functions of HA with varying molecular weights of HA in vivo and the selection of drug delivery methods for different diseases are discussed.

Roles of Kdm6a and Kdm6b in regulation of mammalian neural regeneration

Epigenetic regulation of neuronal transcriptomic landscape is emerging to be a key coordinator of mammalian neural regeneration. Here we investigated roles of two histone 3 lysine 27 (H3K27) demethylases Kdm6a/b in controlling neuroprotection and axon regeneration. Deleting either Kdm6a or Kdm6b led to enhanced sensory axon regeneration in PNS, whereas in the CNS only deleting Kdm6a in retinal ganglion cells (RGCs) significantly enhanced optic nerve regeneration. Moreover, both Kdm6a and Kdm6b functioned to regulate RGC survival but with different mechanisms. Mechanistically, Kdm6a regulates RGC regeneration via distinct pathway from that of Pten and co-deleting Kdm6a and Pten resulted in long distance optic nerve regeneration passing the optic chiasm. In addition, RNA-seq profiling revealed that Kdm6a deletion switched the RGC transcriptomics into a developmental-like state and suppressed several known repressors of neural regeneration. Klf4 was identified as a direct downstream target of Kdm6a-H3K27me3 signaling in both sensory neurons and RGCs to regulate axon regeneration. These findings not only revealed different roles of Kdm6a and Kdm6b in regulation of neural regeneration and their underlying mechanisms, but also identified Kdm6a-mediated histone demethylation signaling as a novel epigenetic target for supporting CNS neural regeneration.

The Role of H3K27me3-Mediated Th17 Differentiation in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a common chronic progressive inflammatory autoimmune disease. T helper 17 (Th17) cells are the major effector cells mediating AS inflammation. Histone 3 Lys 27 trimethylation (H3K27me3) is an inhibitory histone modification that silences gene transcription and plays an important role in Th17 differentiation. The objective of this study was to investigate the expression of H3K27me3 in patients with AS and to explore its epigenetic regulation mechanism of Th17 differentiation during AS inflammation. We collected serum samples from 45 patients with AS at various stages and 10 healthy controls to measure their Interleukin-17 (IL-17) levels using ELISA. A quantitative polymerase chain reaction was used to quantify the mRNA levels of RORc and the signaling molecules of the JAK2/STAT3 pathway, JMJD3, and EZH2. Additionally, Western blot analysis was performed to quantify the protein levels of H3K27me3, RORγt, JAK2, STAT3, JMJD3, and EZH2 in cell protein extracts. The results showed that H3K27me3 expression in peripheral blood mononuclear cells (PBMCs) was significantly lower in patients with active AS compared to both the normal control groups and those with stable AS. Moreover, a significant negative correlation was observed between H3K27me3 expression and the characteristic transcription factor of Th17 differentiation, RORγt. We also discovered that patients with active AS exhibited significantly higher levels of JMJD3, an inhibitor of H3K27 demethylase, compared to the normal control group and patients with stable AS, while the expression of H3K27 methyltransferase (EZH2) was significantly lower. These findings suggest that H3K27me3 may be a dynamic and important epigenetic modification in AS inflammation, and JMJD3/EZH2 regulates the methylation level of H3K27me3, which may be one of the key regulatory factors in the pathogenesis of AS. These findings contribute to our understanding of the role of epigenetics in AS and may have implications for the development of novel therapeutic strategies for AS.

Mechanical loading on cell-free polymer composite scaffold enhances in situ regeneration of fully functional Achilles tendon in a rabbit model

Traditional tendon engineering using cell-loaded scaffold has limited application potential due to the need of autologous cells. We hypothesize that potent mechanical loading can efficiently induce in situ Achilles tendon regeneration in a rabbit model by using a cell-free porous composite scaffold. In this study, melt-spinning was used to fabricate PGA (polyglycolic acid) and PLA (polylactic acid) filament fibers as well as non-woven PGA fibers. The PLA/PGA (4:2) filament fibers were further braided into a hybrid yarn，which was knitted into a PLA/PGA tubular mesh with potent mechanical property for sustaining natural tendon strain. The results showed that a complete cross-section of Achilles tendon created a model of full mechanical loading on the bridging scaffold, which could efficiently induce in situ tendon regeneration by promoting host cell infiltration, matrix production and tissue remodeling. Histologically, mechanical loading assisted in forming parallel aligned collagen fibers and tenocytes in a fashion similar to those of native tendon. Transmission electron microscope further demonstrated that mechanical strain induced collagen fibril development by increasing fibril diameter and forming bipolar structure, which resulted in enhanced mechanical properties. Interestingly, the synergistic effect between mechanical loading and hyaluronic acid modification was also observed on the induced tenogenic differentiation of infiltrated host fibroblasts. In conclusion, potent mechanical loading is the key inductive microenvironment for in situ tendon regeneration for this polymer-based composite scaffold with proper matrix modification, which may serve as a universal scaffold product for tendon regeneration.

Gasdermin D-mediated metabolic crosstalk promotes tissue repair

The establishment of an early pro-regenerative niche is crucial for tissue regeneration1,2. Gasdermin D (GSDMD)-dependent pyroptosis accounts for the release of inflammatory cytokines upon various insults3-5. However, little is known about its role in tissue regeneration followed by homeostatic maintenance. Here we show that macrophage GSDMD deficiency delays tissue recovery but has little effect on the local inflammatory milieu or the lytic pyroptosis process. Profiling of the metabolite secretome of hyperactivated macrophages revealed a non-canonical metabolite-secreting function of GSDMD. We further identified 11,12-epoxyeicosatrienoic acid (11,12-EET) as a bioactive, pro-healing oxylipin that is secreted from hyperactive macrophages in a GSDMD-dependent manner. Accumulation of 11,12-EET by direct supplementation or deletion of Ephx2, which encodes a 11,12-EET-hydrolytic enzyme, accelerated muscle regeneration. We further demonstrated that EPHX2 accumulated within aged muscle, and that consecutive 11,12-EET treatment rejuvenated aged muscle. Mechanistically, 11,12-EET amplifies fibroblast growth factor signalling by modulating liquid-liquid phase separation of fibroblast growth factors, thereby boosting the activation and proliferation of muscle stem cells. These data depict a GSDMD-guided metabolite crosstalk between macrophages and muscle stem cells that governs the repair process, which offers insights with therapeutic implications for the regeneration of injured or aged tissues.

Beyond the bulk: overview and novel insights into the dynamics of muscle satellite cells during muscle regeneration

Skeletal muscle possesses remarkable regenerative capabilities, fully recovering within a month following severe acute damage. Central to this process are muscle satellite cells (MuSCs), a resident population of somatic stem cells capable of self-renewal and differentiation. Despite the highly predictable course of muscle regeneration, evaluating this process has been challenging due to the heterogeneous nature of myogenic precursors and the limited insight provided by traditional markers with overlapping expression patterns. Notably, recent advancements in single-cell technologies, such as single-cell (scRNA-seq) and single-nucleus RNA sequencing (snRNA-seq), have revolutionized muscle research. These approaches allow for comprehensive profiling of individual cells, unveiling dynamic heterogeneity among myogenic precursors and their contributions to regeneration. Through single-cell transcriptome analyses, researchers gain valuable insights into cellular diversity and functional dynamics of MuSCs post-injury. This review aims to consolidate classical and new insights into the heterogeneity of myogenic precursors, including the latest discoveries from novel single-cell technologies.

IL-17 signaling pathway: A potential therapeutic target for reducing skeletal muscle inflammation

BACKGROUND

The interleukin-17 (IL-17) signaling pathway is intricately linked with immunity and inflammation; however, the association between the IL-17 signaling pathway and skeletal muscle inflammation remains poorly understood. The study aims to investigate the role of the IL-17 signaling pathway in skeletal muscle inflammation and to evaluate the therapeutic potential of anti-IL-17 antibodies in reducing muscle inflammation.

METHODS

A skeletal muscle inflammation model was induced by cardiotoxin (CTX) injection in C57BL6/J mice. Following treatment with an anti-IL-17 antibody, we conducted a comprehensive analysis integrating single-cell RNA sequencing (scRNA-seq), bioinformatics, enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and Western blot techniques to elucidate underlying mechanisms.

RESULTS

scRNA-seq analysis revealed a significant increase in neutrophil numbers and activity in inflamed skeletal muscle compared to other cell types, including macrophages, T cells, B cells, endothelial cells, fast muscle cells, fibroblasts, and skeletal muscle satellite cells. The top 30 differentially expressed genes within neutrophils, along with 55 chemokines, were predominantly enriched in the IL-17 signaling pathway. Moreover, the IL-17 signaling pathway exhibited heightened expression in inflamed skeletal muscle, particularly within neutrophils. Treatment with anti-IL-17 antibody resulted in the suppression of IL-17 signaling pathway expression, accompanied by reduced levels of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, as well as decreased numbers and activity of Ly6g+/Mpo+ neutrophils compared to CTX-induced skeletal muscle inflammation.

CONCLUSION

Our findings suggest that the IL-17 signaling pathway plays a crucial role in promoting inflammation within skeletal muscle. Targeting this pathway may hold promise as a therapeutic strategy for ameliorating the inflammatory micro-environment and reducing cytokine production.

Emerging role of Jumonji domain-containing protein D3 in inflammatory diseases

Jumonji domain-containing protein D3 (JMJD3) is a 2-oxoglutarate-dependent dioxygenase that specifically removes transcriptional repression marks di- and tri-methylated groups from lysine 27 on histone 3 (H3K27me2/3). The erasure of these marks leads to the activation of some associated genes, thereby influencing various biological processes, such as development, differentiation, and immune response. However, comprehensive descriptions regarding the relationship between JMJD3 and inflammation are lacking. Here, we provide a comprehensive overview of JMJD3, including its structure, functions, and involvement in inflammatory pathways. In addition, we summarize the evidence supporting JMJD3's role in several inflammatory diseases, as well as the potential therapeutic applications of JMJD3 inhibitors. Additionally, we also discuss the challenges and opportunities associated with investigating the functions of JMJD3 and developing targeted inhibitors and propose feasible solutions to provide valuable insights into the functional exploration and discovery of potential drugs targeting JMJD3 for inflammatory diseases.

Hydrogel biomaterials that stiffen and soften on demand reveal that skeletal muscle stem cells harbor a mechanical memory

Muscle stem cells (MuSCs) are specialized cells that reside in adult skeletal muscle poised to repair muscle tissue. The ability of MuSCs to regenerate damaged tissues declines markedly with aging and in diseases such as Duchenne muscular dystrophy, but the underlying causes of MuSC dysfunction remain poorly understood. Both aging and disease result in dramatic increases in the stiffness of the muscle tissue microenvironment from fibrosis. MuSCs are known to lose their regenerative potential if cultured on stiff plastic substrates. We sought to determine whether MuSCs harbor a memory of their past microenvironment and if it can be overcome. We tested MuSCs in situ using dynamic hydrogel biomaterials that soften or stiffen on demand in response to light and found that freshly isolated MuSCs develop a persistent memory of substrate stiffness characterized by loss of proliferative progenitors within the first three days of culture on stiff substrates. MuSCs cultured on soft hydrogels had altered cytoskeletal organization and activity of Rho and Rac guanosine triphosphate hydrolase (GTPase) and Yes-associated protein mechanotransduction pathways compared to those on stiff hydrogels. Pharmacologic inhibition identified RhoA activation as responsible for the mechanical memory phenotype, and single-cell RNA sequencing revealed a molecular signature of the mechanical memory. These studies highlight that microenvironmental stiffness regulates MuSC fate and leads to MuSC dysfunction that is not readily reversed by changing stiffness. Our results suggest that stiffness can be circumvented by targeting downstream signaling pathways to overcome stem cell dysfunction in aged and disease states with aberrant fibrotic tissue mechanics.

The Impact of Sciatic Nerve Injury on Extracellular Matrix of Lower Limb Muscle and Thoracolumbar Fascia: An Observational Study

Peripheral nerve injury (PNI) is a complex clinical challenge resulting in functional disability. Neurological recovery does not always ensure functional recovery, as extracellular matrix (ECM) alterations affect muscle function. This study evaluates hyaluronan (HA) and collagen concentration in the gastrocnemius muscle and thoracolumbar fascia (TLF) in unilateral lower limb PNI rats to explore systemic ECM alterations following PNI and their impacts on functional recovery. Eighteen 8-week-old male Sprague-Dawley rats were divided into experimental (n = 12 left sciatic nerve injury) and control (n = 6) groups. After six weeks, motor function was evaluated. Muscle and TLF samples were analysed for HA and collagen distribution and concentrations. SFI and gait analysis confirmed a functional deficit in PNI rats 6 weeks after surgery. HA concentration in both sides of the muscles decreased by approximately one-third; both sides showed significantly higher collagen concentration than healthy rats (12.74 ± 4.83 µg/g), with the left (32.92 ± 11.34 µg/g) significantly higher than the right (20.15 ± 7.03 µg/g). PNI rats also showed significantly lower HA (left: 66.95 ± 20.08 µg/g; right: 112.66 ± 30.53 µg/g) and higher collagen (left: 115.89 ± 28.18 µg/g; right: 90.43 ± 20.83 µg/g) concentrations in both TLF samples compared to healthy rats (HA: 167.18 ± 31.13 µg/g; collagen: 47.51 ± 7.82 µg/g), with the left TLF more affected. Unilateral lower limb PNI induced HA reduction and collagen accumulation in both the lower limb muscles and the TLF, potentially exacerbating motor function impairment and increasing the risk of low back dysfunctions.

Mechanobiology of Hyaluronan: Connecting Biomechanics and Bioactivity in Musculoskeletal Tissues

Hyaluronan (HA) plays well-recognized mechanical and biological roles in articular cartilage and synovial fluid, where it contributes to tissue structure and lubrication. An understanding of how HA contributes to the structure of other musculoskeletal tissues, including muscle, bone, tendon, and intervertebral discs, is growing. In addition, the use of HA-based therapies to restore damaged tissue is becoming more prevalent. Nevertheless, the relationship between biomechanical stimuli and HA synthesis, degradation, and signaling in musculoskeletal tissues remains understudied, limiting the utility of HA in regenerative medicine. In this review, we discuss the various roles and significance of endogenous HA in musculoskeletal tissues. We use what is known and unknown to motivate new lines of inquiry into HA biology within musculoskeletal tissues and in the mechanobiology governing HA metabolism by suggesting questions that remain regarding the relationship and interaction between biological and mechanical roles of HA in musculoskeletal health and disease.

Characterization of perivascular alveolar epithelial stem cells and their niche in lung homeostasis and cancer

Lung alveolar structure and function are maintained by subsets of alveolar type II stem cells (AT2s), but there is a need for characterization of these subsets and their associated niches. Here, we report a CD44high subpopulation of AT2s characterized by increased expression of genes that regulate immune signaling even during steady-state homeostasis. Disruption of one of these immune regulatory transcription factor STAT1 impaired the stem cell function of AT2s. CD44high cells were preferentially located near macro- blood vessels and a supportive niche constituted by LYVE1+ endothelial cells, adventitial fibroblasts, and accumulated hyaluronan. In this microenvironment, CD44high AT2 cells were more responsive to transformation by KRAS than general AT2 cells. Moreover, after bacterial lung injury, there was a significant increase of CD44high AT2s and niche components distributed throughout the lung parenchyma. Taken together, CD44high AT2 cells and their perivascular niche regulate tissue homeostasis and tumor formation.

The bioengineering application of hyaluronic acid in tissue regeneration and repair

The multifaceted role of hyaluronic acid (HA) across diverse biomedical disciplines underscores its versatility in tissue regeneration and repair. HA hydrogels employ different crosslinking including chemical (chitosan, collagen), photo- initiation (riboflavin, LAP), enzymatic (HRP/H2O2), and physical interactions (hydrogen bonds, metal coordination). In biophysics and biochemistry, HA's signaling pathways, primarily through CD44 and RHAMM receptors, modulate cell behavior (cell migration; internalization of HA), inflammation, and wound healing. Particularly, smaller HA fragments stimulate inflammatory responses through toll-like receptors, impacting macrophages and cytokine expression. HA's implications in oncology highlight its involvement in tumor progression, metastasis, and treatment. Elevated HA in tumor stroma impacts apoptosis resistance and promotes tumor growth, presenting potential therapeutic targets to halt tumor progression. In orthopedics, HA's presence in synovial fluid aids in osteoarthritis management, as its supplementation alleviates pain, enhances synovial fluid's viscoelastic properties, and promotes cartilage integrity. In ophthalmology, HA's application in dry eye syndrome addresses symptoms by moisturizing the eyes, replenishing tear film deficiencies, and facilitating wound healing. Intravitreal injections and hydrogel-based systems offer versatile approaches for drug delivery and vitreous humor replacement. For skin regeneration and wound healing, HA hydrogel dressings exhibit exceptional properties by promoting moist wound healing and facilitating tissue repair. Integration of advanced regenerative tools like stem cells and solubilized amnion membranes into HA-based systems accelerates wound closure and tissue recovery. Overall, HA's unique properties and interactions render it a promising candidate across diverse biomedical domains, showcasing immense potentials in tissue regeneration and therapeutic interventions. Nevertheless, many detailed cellular and molecular mechanisms of HA and its applications remain unexplored and warrant further investigation.

Osteoinductive Dental Pulp Stem Cell-Derived Extracellular Vesicle-Loaded Multifunctional Hydrogel for Bone Regeneration

Stem cell-derived extracellular vesicles (EVs) show great potential for promoting bone tissue regeneration. However, normal EVs (Nor-EVs) have a limited ability to direct tissue-specific regeneration. Therefore, it is necessary to optimize the osteogenic capacity of EV-based systems for repairing extensive bone defects. Herein, we show that hydrogels loaded with osteoinductive dental pulp stem cell-derived EVs (Ost-EVs) enhanced bone tissue remodeling, resulting in a 2.23 ± 0.25-fold increase in the expression of bone morphogenetic protein 2 (BMP2) compared to the hydrogel control group. Moreover, Ost-EVs led to a higher expression of alkaline phosphatase (ALP) (1.88 ± 0.16 of Ost-EVs relative to Nor-EVs) and the formation of orange-red calcium nodules (1.38 ± 0.10 of Ost-EVs relative to Nor-EVs) in vitro. RNA sequencing revealed that Ost-EVs showed significantly high miR-1246 expression. An ideal hydrogel implant should also adhere to surrounding moist tissues. In this study, we were drawn to mussel-inspired adhesive modification, where the hydrogel carrier was crafted from hyaluronic acid (HA) and polyethylene glycol derivatives, showcasing impressive tissue adhesion, self-healing capabilities, and the ability to promote bone growth. The modified HA (mHA) hydrogel was also responsive to environmental stimuli, making it an effective carrier for delivering EVs. In an ectopic osteogenesis animal model, the Ost-EV/hydrogel system effectively alleviated inflammation, accelerated revascularization, and promoted tissue mineralization. We further used a rat femoral condyle defect model to evaluate the in situ osteogenic ability of the Ost-EVs/hydrogel system. Collectively, our results suggest that Ost-EVs combined with biomaterial-based hydrogels hold promising potential for treating bone defects.

Epigenetic integration of signaling from the regenerative environment

Skeletal muscle has an extraordinary capacity to regenerate itself after injury due to the presence of tissue-resident muscle stem cells. While these muscle stem cells are the primary contributor to the regenerated myofibers, the process occurs in a regenerative microenvironment where multiple different cell types act in a coordinated manner to clear the damaged myofibers and restore tissue homeostasis. In this regenerative environment, immune cells play a well-characterized role in initiating repair by establishing an inflammatory state that permits the removal of dead cells and necrotic muscle tissue at the injury site. More recently, it has come to be appreciated that the immune cells also play a crucial role in communicating with the stem cells within the regenerative environment to help coordinate the timing of repair events through the secretion of cytokines, chemokines, and growth factors. Evidence also suggests that stem cells can help modulate the extent of the inflammatory response by signaling to the immune cells, demonstrating a cross-talk between the different cells in the regenerative environment. Here, we review the current knowledge on the innate immune response to sterile muscle injury and provide insight into the epigenetic mechanisms used by the cells in the regenerative niche to integrate the cellular cross-talk required for efficient muscle repair.

Chromatin organization of muscle stem cell

The proper functioning of skeletal muscles is essential throughout life. A crucial crosstalk between the environment and several cellular mechanisms allows striated muscles to perform successfully. Notably, the skeletal muscle tissue reacts to an injury producing a completely functioning tissue. The muscle's robust regenerative capacity relies on the fine coordination between muscle stem cells (MuSCs or "satellite cells") and their specific microenvironment that dictates stem cells' activation, differentiation, and self-renewal. Critical for the muscle stem cell pool is a fine regulation of chromatin organization and gene expression. Acquiring a lineage-specific 3D genome architecture constitutes a crucial modulator of muscle stem cell function during development, in the adult stage, in physiological and pathological conditions. The context-dependent relationship between genome structure, such as accessibility and chromatin compartmentalization, and their functional effects will be analysed considering the improved 3D epigenome knowledge, underlining the intimate liaison between environmental encounters and epigenetics.

Going Full TeRM: The Seminal Role of Tissue-Resident Macrophages in Organ Remodeling during Pregnancy and Lactation

During pregnancy and lactation, the uterus and mammary glands undergo remarkable structural changes to perform their critical reproductive functions before reverting to their original dormant state upon childbirth and weaning, respectively. Underlying this incredible plasticity are complex remodeling processes that rely on coordinated decisions at both the cellular and tissue-subunit levels. With their exceptional versatility, tissue-resident macrophages play a variety of supporting roles in these organs during each stage of development, ranging from maintaining immune homeostasis to facilitating tissue remodeling, although much remains to be discovered about the identity and regulation of individual macrophage subsets. In this study, we review the increasingly appreciated contributions of these immune cells to the reproductive process and speculate on future lines of inquiry. Deepening our understanding of their interactions with the parenchymal or stromal populations in their respective niches may reveal new strategies to ameliorate complications in pregnancy and breastfeeding, thereby improving maternal health and well-being.

Skeletal muscle niche, at the crossroad of cell/cell communications

Skeletal muscle is composed of a variety of tissue and non-tissue resident cells that participate in homeostasis. In particular, the muscle stem cell niche is a dynamic system, requiring direct and indirect communications between cells, involving local and remote cues. Interactions within the niche must happen in a timely manner for the maintenance or recovery of the homeostatic niche. For instance, after an injury, pro-myogenic cues delivered too early will impact on muscle stem cell proliferation, delaying the repair process. Within the niche, myofibers, endothelial cells, perivascular cells (pericytes, smooth muscle cells), fibro-adipogenic progenitors, fibroblasts, and immune cells are in close proximity with each other. Each cell behavior, membrane profile, and secretome can interfere with muscle stem cell fate and skeletal muscle regeneration. On top of that, the muscle stem cell niche can also be modified by extra-muscle (remote) cues, as other tissues may act on muscle regeneration via the production of circulating factors or the delivery of cells. In this review, we highlight recent publications evidencing both local and remote effectors of the muscle stem cell niche.

Lysine methylation signaling in skeletal muscle biology: from myogenesis to clinical insights

Lysine methylation signaling is well studied for its key roles in the regulation of transcription states through modifications on histone proteins. While histone lysine methylation has been extensively studied, recent discoveries of lysine methylation on thousands of non-histone proteins has broadened our appreciation for this small chemical modification in the regulation of protein function. In this review, we highlight the significance of histone and non-histone lysine methylation signaling in skeletal muscle biology, spanning development, maintenance, regeneration, and disease progression. Furthermore, we discuss potential future implications for its roles in skeletal muscle biology as well as clinical applications for the treatment of skeletal muscle-related diseases.

Immune-microenvironment modulatory polyurethane-hyaluronic acid hybrid hydrogel scaffolds for diabetic wound treatment

The healing of wounds in diabetic patients is a huge challenge issue in clinical medicine due to the disordered immune. Recruiting endogenous cells to play a role in the early stage and timely reducing inflammation to promote healing in the middle or late of injuring are both prerequisites for effective treatment. Here, inspired by natural extracellular matrix, three-dimensional porous polyurethane-hyaluronic acid hybrid hydrogel scaffolds (PUHA) were prepared to repair diabetic wound through activate cell immunity by moderate foreign body reaction, provide cell adhesion growth extracellular matrix of hyaluronic acid (HA) and exhibit anti-inflammatory effect of polyurethane (PU). The interaction between PU and HA alters the compact PU hydrogel into macroporous PUHA hydrogel scaffolds with super-swelling, elastic mechanical properties, and controllable degradation, which are suitable for endogenous cells infiltration, growth and immune activation. Additionally, incorporating with RGD, PUHA hydrogel scaffolds with bioactive physicochemical features can evidently reduce the inflammation and modulate the polarization of macrophage apparently both in vitro and in vivo, mainly through downregulation of cytokine-cytokine receptor interaction genes, leading to reprogramming immune-microenvironment and rapid diabetic wound healing. This method of gathering cells initially and intervening immune-microenvironment in time provides an expected way to design biomaterials for chronic wound healing.

Upregulation of lysine-specific demethylase 6B aggravates inflammatory pain through H3K27me3 demethylation-dependent production of TNF-α in the dorsal root ganglia and spinal dorsal horn in rats

AIMS

Lysine-specific demethylase 6B (KDM6B) serves as a key mediator of gene transcription. It regulates expression of proinflammatory cytokines and chemokines in variety of diseases. Herein, the role and the underlying mechanisms of KDM6B in inflammatory pain were studied.

METHODS

The inflammatory pain was conducted by intraplantar injection of complete Freund's adjuvant (CFA) in rats. Immunofluorescence, Western blotting, qRT-PCR, and chromatin immunoprecipitation (ChIP)-PCR were performed to investigate the underlying mechanisms.

RESULTS

CFA injection led to upregulation of KDM6B and decrease in the level of H3K27me3 in the dorsal root ganglia (DRG) and spinal dorsal horn. The mechanical allodynia and thermal hyperalgesia following CFA were alleviated by the treatment of intrathecal injection of GSK-J4, and by microinjection of AAV-EGFP-KDM6B shRNA in the sciatic nerve or in lumbar 5 dorsal horn. The increased production of tumor necrosis factor-α (TNF-α) following CFA in the DRGs and dorsal horn was inhibited by these treatments. ChIP-PCR showed that CFA-induced increased binding of nuclear factor κB with TNF-α promoter was repressed by the treatment of microinjection of AAV-EGFP-KDM6B shRNA.

CONCLUSIONS

These results suggest that upregulated KDM6B via facilitating TNF-α expression in the DRG and spinal dorsal horn aggravates inflammatory pain.

The transcriptional regulator KLF15 is necessary for myoblast differentiation and muscle regeneration by activating FKBP5

Successful muscle regeneration following injury is essential for functional homeostasis of skeletal muscles. Krüppel-like factor 15 (KLF15) is a metabolic transcriptional regulator in the muscles. However, little is known regarding its function in muscle regeneration. Here, we examined microarray datasets from the Gene Expression Omnibus database, which indicated downregulated KLF15 in muscles from patients with various muscle diseases. Additionally, we found that Klf15 knockout (Klf15KO) impaired muscle regeneration following injury in mice. Furthermore, KLF15 expression was robustly induced during myoblast differentiation. Myoblasts with KLF15 deficiency showed a marked reduction in their fusion capacity. Unbiased transcriptome analysis of muscles on day 7 postinjury revealed downregulated genes involved in cell differentiation and metabolic processes in Klf15KO muscles. The FK506-binding protein 51 (FKBP5), a positive regulator of myoblast differentiation, was ranked as one of the most strongly downregulated genes in the Klf15KO group. A mechanistic search revealed that KLF15 binds directly to the promoter region of FKBP5 and activates FKBP5 expression. Local delivery of FKBP5 rescued the impaired muscle regeneration in Klf15KO mice. Our findings reveal a positive regulatory role of KLF15 in myoblast differentiation and muscle regeneration by activating FKBP5 expression. KLF15 signaling may be a novel therapeutic target for muscle disorders associated with injuries or diseases.

Intravenous Injection of Sodium Hyaluronate Diminishes Basal Inflammatory Gene Expression in Equine Skeletal Muscle

Following strenuous exercise, skeletal muscle experiences an acute inflammatory state that initiates the repair process. Systemic hyaluronic acid (HA) is injected to horses routinely as a joint anti-inflammatory. To gain insight into the effects of HA on skeletal muscle, adult Thoroughbred geldings (n = 6) were injected with a commercial HA product weekly for 3 weeks prior to performing a submaximal exercise test. Gluteal muscle (GM) biopsies were obtained before and 1 h after exercise for gene expression analysis and HA localization. The results from RNA sequencing demonstrate differences in gene expression between non-injected controls (CON; n = 6) and HA horses. Prior to exercise, HA horses contained fewer (p < 0.05) transcripts associated with leukocyte activity and cytokine production than CON. The performance of exercise resulted in the upregulation (p < 0.05) of several cytokine genes and their signaling intermediates, indicating that HA does not suppress the normal inflammatory response to exercise. The transcript abundance for marker genes of neutrophils (NCF2) and macrophages (CD163) was greater (p < 0.05) post-exercise and was unaffected by HA injection. The anti-inflammatory effects of HA on muscle are indirect as no differences (p > 0.05) in the relative amount of the macromolecule was observed between the CON and HA fiber extracellular matrix (ECM). However, exercise tended (p = 0.10) to cause an increase in ECM size suggestive of muscle damage and remodeling. The finding was supported by the increased (p < 0.05) expression of CTGF, TGFβ1, MMP9, TIMP4 and Col4A1. Collectively, the results validate HA as an anti-inflammatory aid that does not disrupt the normal post-exercise muscle repair process.

Generation of a MyoD knock-in reporter mouse line to study muscle stem cell dynamics and heterogeneity

Myoblast determination protein 1 (MyoD) dynamics define the activation status of muscle stem cells (MuSCs), aiding in muscle tissue regeneration after injury. However, the lack of experimental platforms to monitor MyoD dynamics in vitro and in vivo has hampered the investigation of fate determination and heterogeneity of MuSCs. Herein, we report a MyoD knock-in (MyoD-KI) reporter mouse expressing tdTomato at the endogenous MyoD locus. Expression of tdTomato in MyoD-KI mice recapitulated the endogenous MyoD expression dynamics in vitro and during the early phase of regeneration in vivo. Additionally, we showed that tdTomato fluorescence intensity defines MuSC activation status without immunostaining. Based on these features, we developed a high-throughput screening system to assess the effects of drugs on the behavior of MuSCs in vitro. Thus, MyoD-KI mice are an invaluable resource for studying the dynamics of MuSCs, including their fate decisions and heterogeneity, and for drug screening in stem cell therapy.

The Efficacy of New Zealand Greenshell™ Mussel Powder Supplementation in Supporting Muscle Recovery Following Eccentric Exercise-Induced Muscle Damage in Healthy, Untrained Adult Males

Unaccustomed eccentric exercise results in muscle damage limiting physical performance for several days. This study investigated if Greenshell™ mussel (GSM) powder consumption expedited muscle recovery from eccentric exercise-induced muscle damage (EIMD). Methods: Twenty untrained adult men were recruited into a double-blind, placebo-controlled, cross-over study and were randomly assigned to receive the GSM powder or placebo treatment first. Participants consumed their allocated intervention for four weeks then completed a bench-stepping exercise that induced muscle damage to the eccentrically exercised leg. Muscle function, soreness and biomarkers of muscle damage, oxidative stress and inflammation were measured before exercise, immediately after exercise and 24, 48 and 72 h post exercise. GSM powder promoted muscle function recovery, significantly improving (p < 0.05) isometric and concentric peak torque at 48 h and 72 h post exercise, respectively. Participants on the GSM treatment had faster dissipation of soreness, with significant treatment × time interactions for affective (p = 0.007) and Visual Analogue Scale-assessed pain (p = 0.018). At 72 h, plasma creatine kinase concentrations in the GSM group were lower (p < 0.05) compared with the placebo group. This study provides evidence for GSM powder being effective in supporting muscle recovery from EIMD.

Bidirectional regulation of postmitotic H3K27me3 distributions underlie cerebellar granule neuron maturation dynamics

The functional maturation of neurons is a prolonged process that extends past the mitotic exit and is mediated by the chromatin-dependent orchestration of gene transcription programs. We find that expression of this maturation gene program in mouse cerebellar granule neurons (CGNs) requires dynamic changes in the genomic distribution of histone H3 lysine 27 trimethylation (H3K27me3), demonstrating a function for this chromatin modification beyond its role in cell fate specification. The developmental loss of H3K27me3 at promoters of genes activated as CGNs mature is facilitated by the lysine demethylase and ASD-risk gene, Kdm6b. Interestingly, inhibition of the H3K27 methyltransferase EZH2 in newborn CGNs not only blocks the repression of progenitor genes but also impairs the induction of mature CGN genes, showing the importance of bidirectional H3K27me3 regulation across the genome. These data demonstrate that H3K27me3 turnover in developing postmitotic neurons regulates the temporal coordination of gene expression programs that underlie functional neuronal maturation.

KDM6B protects T-ALL cells from NOTCH1-induced oncogenic stress

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematopoietic neoplasm resulting from the malignant transformation of T-cell progenitors. While activating NOTCH1 mutations are the dominant genetic drivers of T-ALL, epigenetic dysfunction plays a central role in the pathology of T-ALL and can provide alternative mechanisms to oncogenesis in lieu of or in combination with genetic mutations. The histone demethylase enzyme KDM6A (UTX) is also recurrently mutated in T-ALL patients and functions as a tumor suppressor. However, its gene paralog, KDM6B (JMJD3), is never mutated and can be significantly overexpressed, suggesting it may be necessary for sustaining the disease. Here, we used mouse and human T-ALL models to show that KDM6B is required for T-ALL development and maintenance. Using NOTCH1 gain-of-function retroviral models, mouse cells genetically deficient for Kdm6b were unable to propagate T-ALL. Inactivating KDM6B in human T-ALL patient cells by CRISPR/Cas9 showed KDM6B-targeted cells were significantly outcompeted over time. The dependence of T-ALL cells on KDM6B was proportional to the oncogenic strength of NOTCH1 mutation, with KDM6B required to prevent stress-induced apoptosis from strong NOTCH1 signaling. These studies identify a crucial role for KDM6B in sustaining NOTCH1-driven T-ALL and implicate KDM6B as a novel therapeutic target in these patients.

From crosslinking strategies to biomedical applications of hyaluronic acid-based hydrogels: A review

Hyaluronic acid (HA) is not only a natural anionic polysaccharide with excellent biocompatibility, biodegradability, and moisturizing effect, but also an essential factor that can affect angiogenesis, inflammation, cell behavior, which has a wide range of applications in the biomedical field. Among them, HA-based hydrogels formed by various physical or chemical crosslinking strategies are particularly striking. They not only retain the physiological function of HA, but also have the skeleton function of hydrogel, which further expands the application of HA. However, HA-based natural hydrogels generally have problems such as insufficient mechanical strength and susceptibility to degradation by hyaluronidase, which limits their application to a certain extent. To solve such problems, researchers have prepared a variety of HA-based multifunctional hydrogels with remarkable properties in recent years by adopting various structural modification methods or novel crosslinking strategies, as well as introducing functionally reactive molecules or moieties, which have extended the application scope. This manuscript systematically introduced common crosslinking strategies of HA-based hydrogels and highlighted the development of novel HA-based hydrogels in anticancer drug delivery, cartilage repair, three-dimensional cell culture, skin dressing and other fields. We hope to provide some references for the subsequent development of HA-based hydrogels in the biomedical field.

Therapeutic role of adipose-derived mesenchymal stem cells-derived extracellular vesicles in rats with obstructive sleep apnea hypopnea syndrome

Background

Obstructive sleep apnea hypopnea syndrome (OSAHS) is an underestimated sleep disorder that leads to multiple organ damages, including lung injury (LI). This paper sought to analyze the molecular mechanism of extracellular vesicles (EVs) from adipose-derived mesenchymal stem cells (ADSCs) in OSAHS-induced lung injury (LI) via the miR-22-3p/histone lysine demethylase 6 B (KDM6B)/high mobility group AT-hook 2 (HMGA2) axis.

Methods

ADSCs and ADSCs-EVs were separated and characterized. Chronic intermittent hypoxia (CIH) was used to mimic OSAHS-LI, followed by ADSCs-EVs treatment and hematoxylin and eosin staining, TUNEL, ELISA, and assays of inflammation and oxidative stress (MPO/ROS/MDA/SOD). The CIH cell model was established and treated with ADSCs-EVs. Cell injury was assessed by the assays of MTT, TUNEL, ELISA, and others. Levels of miR-22-3p, KDM6B, histone H3 trimethylation at lysine 27 (H3K27me3), and HMGA2 were determine by RT-qPCR or Western blot analysis. The transfer of miR-22-3p by ADSCs-EVs was observed by fluorescence microscopy. Gene interactions were analyzed by dual-luciferase assay or chromatin immunoprecipitation.

Results

ADSCs-EVs effectively alleviated OSAHS-LI by reducing lung tissue injury, apoptosis, oxidative stress, and inflammation. In vitro, ADSCs-EVs increased cell viability and reduced apoptosis, inflammation and oxidative stress. ADSCs-EVs delivered enveloped miR-22-3p into pneumonocytes to upregulate miR-22-3p expression, inhibit KDM6B expression, increase H3K27me3 levels on the HMGA2 promoter, and decrease HMGA2 mRNA levels. Overexpression of KDM6B or HMGA2 attenuated the protective role of ADSCs-EVs in OSAHS-LI.

Conclusion

ADSCs-EVs transferred miR-22-3p to pneumonocytes and reduced apoptosis, inflammation, and oxidative stress through KDM6B/HMGA2, mitigating OSAHS-LI progression.

Exosomal miRNAs-mediated macrophage polarization and its potential clinical application

Macrophages are highly heterogeneous and plastic immune cells that play an important role in the fight against pathogenic microorganisms and tumor cells. After different stimuli, macrophages can polarize to the M1 phenotype to show a pro-inflammatory effect and the M2 phenotype to show an anti-inflammatory effect. The balance of macrophage polarization is highly correlated with disease progression, and therapeutic approaches to reprogram macrophages by targeting macrophage polarization are feasible. There are a large number of exosomes in tissue cells, which can transmit information between cells. In particular, microRNAs (miRNAs) in the exosomes can regulate the polarization of macrophages and further affect the progression of various diseases. At the same time, exosomes are also effective "drug" carriers, laying the foundation for the clinical application of exosomes. This review describes some pathways involved in M1/M2 macrophage polarization and the effects of miRNA carried by exosomes from different sources on the polarization of macrophages. Finally, the application prospects and challenges of exosomes/exosomal miRNAs in clinical treatment are also discussed.

Marine‐Derived Hydrogels for Biomedical Applications

Marine organisms provide novel and broad sources for the preparations and applications of biomaterials. Since the urgent requirement of bio‐hydrogels to mimic tissue extracellular matrix (ECM), the natural biomacromolecule hydrogels derived from marine sources have received increasing attention. Benefiting from their outstanding bioactivity and biocompatibility, many attempts have been made to reconstruct ECM components by applying marine‐derived natural hydrogels. Moreover, marine hydrogels have been successfully applied in biomedicine by means of microfluidics, electrospray, and bioprinting. In this review, the classification and characteristics of marine‐derived hydrogels are summarized. In particular, their role in the development of biomaterials is also introduced. Then, the recent advances in bio‐fabrication strategies for various hydrogel materials are focused upon. Besides, the influences of hydrogel types on their functions in biomedical applications are discussed in depth. Finally, critical reflections on the limitations and future development of marine‐derived hydrogels are presented.

Metabolic regulation of stress erythropoiesis, outstanding questions, and possible paradigms

Steady state erythropoiesis produces new erythrocytes at a constant rate to replace the senescent cells that are removed by macrophages in the liver and spleen. However, infection and tissue damage disrupt the production of erythrocytes by steady state erythropoiesis. During these times, stress erythropoiesis is induced to compensate for the loss of erythroid output. The strategy of stress erythropoiesis is different than steady state erythropoiesis. Stress erythropoiesis generates a wave of new erythrocytes to maintain homeostasis until steady state conditions are resumed. Stress erythropoiesis relies on the rapid proliferation of immature progenitor cells that do not differentiate until the increase in serum Erythropoietin (Epo) promotes the transition to committed progenitors that enables their synchronous differentiation. Emerging evidence has revealed a central role for cell metabolism in regulating the proliferation and differentiation of stress erythroid progenitors. During the initial expansion stage, the immature progenitors are supported by extensive metabolic changes which are designed to direct the use of glucose and glutamine to increase the biosynthesis of macromolecules necessary for cell growth and division. At the same time, these metabolic changes act to suppress the expression of genes involved in erythroid differentiation. In the subsequent transition stage, changes in niche signals alter progenitor metabolism which in turn removes the inhibition of erythroid differentiation generating a bolus of new erythrocytes to alleviate anemia. This review summarizes what is known about the metabolic regulation of stress erythropoiesis and discusses potential mechanisms for metabolic regulation of proliferation and differentiation.

Extracellular matrix: Brick and mortar in the skeletal muscle stem cell niche

The extracellular matrix (ECM) is an interconnected macromolecular scaffold occupying the space between cells. Amongst other functions, the ECM provides structural support to tissues and serves as a microenvironmental niche that conveys regulatory signals to cells. Cell-matrix adhesions, which link the ECM to the cytoskeleton, are dynamic multi-protein complexes containing surface receptors and intracellular effectors that control various downstream pathways. In skeletal muscle, the most abundant tissue of the body, each individual muscle fiber and its associated muscle stem cells (MuSCs) are surrounded by a layer of ECM referred to as the basal lamina. The core scaffold of the basal lamina consists of self-assembling polymeric laminins and a network of collagens that tether proteoglycans, which provide lateral crosslinking, establish collateral associations with cell surface receptors, and serve as a sink and reservoir for growth factors. Skeletal muscle also contains the fibrillar collagenous interstitial ECM that plays an important role in determining tissue elasticity, connects the basal laminae to each other, and contains matrix secreting mesenchymal fibroblast-like cell types and blood vessels. During skeletal muscle regeneration fibroblast-like cell populations expand and contribute to the transitional fibronectin-rich regenerative matrix that instructs angiogenesis and MuSC function. Here, we provide a comprehensive overview of the role of the skeletal muscle ECM in health and disease and outline its role in orchestrating tissue regeneration and MuSC function.