The role of circulating metabolites and gut microbiome in hypertrophic scar: a two-sample Mendelian randomization study.

Hypertrophic scarring is a fibro-proliferative disorder caused by abnormal cutaneous wound healing. Circulating metabolites and the gut microbiome may be involved in the formation of these scars, but high-quality evidence of causality is lacking. To assess whether circulating metabolites and the gut microbiome contain genetically predicted modifiable risk factors for hypertrophic scar formation. Two-sample Mendelian randomization (MR) was performed using MR-Egger, inverse-variance weighting (IVW), Mendelian Randomization Pleiotropy RESidual Sum and Outlier, maximum likelihood, and weighted median methods. Based on the genome-wide significance level, genetically predicted uridine (P = 0.015, odds ratio [OR] = 1903.514, 95% confidence interval [CI] 4.280-846,616.433) and isovalerylcarnitine (P = 0.039, OR = 7.765, 95% CI 1.106-54.512) were positively correlated with hypertrophic scar risk, while N-acetylalanine (P = 0.013, OR = 7.98E-10, 95% CI 5.19E-17-0.012) and glycochenodeoxycholate (P = 0.021, OR = 0.021 95% CI 0.003-0.628) were negatively correlated. Gastranaerophilales and two unknown gut microbe species (P = 0.031, OR = 0.378, 95% CI 0.156-0.914) were associated with an decreased risk of hypertrophic scarring. Circulating metabolites and gut microbiome components may have either positive or negative causal effects on hypertrophic scar formation. The study provides new insights into strategies for diagnosing and limiting hypertrophic scarring.

Mechanical stretch preconditioned adipose-derived stem cells elicit polarization of anti-inflammatory M2-like macrophages and improve chronic wound healing.

Transplantation of adipose-derived stem cells (ASCs) is a promising option in the field of chronic wounds treatment. However, the effectiveness of ASCs therapies has been hampered by highly inflammatory environment in chronic wound areas. These problems could be partially circumvented using efficient approaches that boost the survival and anti-inflammatory capacity of transplanted ASCs. Here, by application of mechanical stretch (MS), we show that ASCs exhibits increased survival and immunoregulatory properties in vitro. MS triggers the secretion of macrophage colony stimulating factor (M-CSF) from ASCs, a chemokine that is linked to anti-inflammatory M2-like macrophages polarization. When the MS-ASCs were transplanted to chronic wounds, the wound area yields significantly faster closure rate and lower inflammatory mediators, largely due to macrophages polarization driven by transplanted MS-ASCs. Thus, our work shows that mechanical stretch can be harnessed to enhance ASCs transplantation efficiency in chronic wounds treatment.

Acellular dermal matrix-assisted tissue expansion for giant congenital melanocytic nevi of the extremities and trunk in pediatric patients.

BACKGROUND: Tissue expansion for treating giant congenital melanocytic nevi (GCMN) is a commonly employed surgical method. However, the procedure's efficacy is often hindered by anatomical and histological characteristics as well as blood supply, particularly in the extremities and trunk. Enhancing expansion efficiency while reducing complications is thus a topic to be investigated, especially for pediatric patients undergoing rapid physical and psychological development with higher risks of non-compliance to medical instructions. OBJECT: To explore the effectiveness of expansion in extremities and trunk by immobilizing the acellular dermal matrix (ADM) in the gravitational force zone of inflating expanders. METHODS: All patients involved in this research underwent ADM-assisted tissue expansion in either the extremities or trunk. ADM was fully flattened, securely fixed to the lower pole of the expander, and subsequently attached to the inner surface of the expanding flap. RESULTS: From 2021 to 2023, a total of nine pediatric patients with GCMN underwent the ADM-assisted tissue expansion. All patients achieved the desired expanding volume without experiencing petechiae, ecchymosis, or skin ulceration in the ADM-covered area. The process was well tolerated by all patients, with no reports of itching, pain, allergic reaction, or fever. During the flap transfer, the ADM was observed to be firmly adhered to the expanding flap with discernible capillary network. CONCLUSION: ADM-assisted tissue expansion demonstrates promise in augmenting expansion efficiency and reducing the time needed for surgical intervention in the extremities and trunk, thereby presenting significant clinical value for pediatric patients afflicted with GCMN.

Mechanical stiffness promotes skin fibrosis via Piezo1-Wnt2/Wnt11-CCL24 positive feedback loop.

Skin fibrosis is characterized by the excessive accumulation of extracellular matrix (ECM) caused by fibrotic disorders of the skin. In recent years, ECM stiffness has emerged as a prominent mechanical cue that precedes skin fibrosis and drives its progression by promoting fibroblasts activation. However, how stiffness influences fibroblasts activation for skin fibrosis progression remains unknown. Here, we report a positive feedback loop mediated by the mechanosensitive ion channel Piezo1 and aberrant tissue mechanics in driving skin fibrosis. Piezo1 is upregulated in fibrotic skin in both humans and mice. Piezo1 knockdown dermal fibroblasts lose their fibroproliferative phenotypes despite being grown on a stiffer substrate. We show that Piezo1 acts through the Wnt2/Wnt11 pathway to mechanically induce secretion of C-C motif chemokine ligand 24 (CCL24, also known as eotaxin-2), a potent cytokine associated with fibrotic disorders. Importantly, adeno-associated virus (AAV)-mediated Piezo1 knockdown ameliorated the progression of skin fibrosis and skin stiffness in mice. Overall, increased matrix stiffness promotes skin fibrosis through the inflammatory Piezo1-Wnt2/Wnt11-CCL24 pathway. In turn, a stiffer skin microenvironment increases Piezo1 expression to exacerbate skin fibrosis aggression. Therefore, targeting Piezo1 represents a strategy to break the positive feedback loop between fibroblasts mechanotransduction and aberrant tissue mechanics in skin fibrosis.

Mechanical stiffness promotes skin fibrosis through FAPα-AKT signaling pathway.

BACKGROUND: Myofibroblasts contribute to the excessive production, remodeling and cross-linking of the extracellular matrix that characterizes the progression of skin fibrosis. An important insight into the pathogenesis of tissue fibrosis has been the discovery that increased matrix stiffness during fibrosis progression is involved in myofibroblast activation. However, mechanistic basis for this phenomenon remains elusive. OBJECTIVE: To explore the role of fibroblast activation protein-α (FAPα) in mechanical stiffness-induced skin fibrosis progression. METHODS: RNA-seq was performed to compare differential genes of mouse dermal fibroblasts (MDFs) grown on low or high stiffness plates. This process identified FAPα, which is a membrane protein usually overexpressed in activated fibroblasts, as a suitable candidate. In vitro assay, we investigate the role of FAPα in mechanical stiffness-induced MDFs activation and downstream pathway. By establishing mouse skin fibrosis model and intradermally administrating FAPα adeno-associated virus (AAV) or a selective Fap inhibitor FAPi, we explore the role of FAPα in skin fibrosis in vivo. RESULTS: We show that FAPα, a membrane protein highly expressed in myofibroblasts of skin fibrotic tissues, is regulated by increased matrix stiffness. Genetic deletion or pharmacological inhibition of FAPα significantly inhibits mechanical stiffness-induced activation of myofibroblasts in vitro. Mechanistically, FAPα promotes myofibroblast activation by stimulating the PI3K-Akt pathway. Furthermore, we showed that administration of the inhibitor FAPi or FAPα targeted knockdown ameliorated the progression of skin fibrosis. CONCLUSION: Taken together, we identify FAPα as an important driver of mechanical stiffness-induced skin fibrosis and a potential therapeutic target for the treatment of skin fibrosis.

Dynamics of cutaneous atmospheric oxygen uptake in response to mechanical stretch revealed by optical fiber microsensor.

Skin expands and regenerates in response to mechanical stretch. This important homeostasis process is critical for skin biology and can be exploited to generate extra skin for reconstructive surgery. Atmospheric oxygen uptake is important in skin homeostasis. However, whether and how cutaneous atmospheric oxygen uptake changes during mechanical stretch remains unclear, and relevant research tools to quantify oxygen flux are limited. Herein, we used the scanning micro-optrode technique (SMOT), a non-invasive self-referencing optical fiber microsensor, to achieve real-time measurement of cutaneous oxygen uptake from the atmosphere. An in vivo mechanical stretch-induced skin expansion model was established, and an in vitro Flexcell Tension system was used to stretch epidermal cells. We found that oxygen influx of skin increased dramatically after stretching for 1 to 3 days and decreased to the non-stretched level after 7 days. The enhanced oxygen influx of stretched skin was associated with increased epidermal basal cell proliferation and impaired epidermal barrier. In conclusion, mechanical stretch increases cutaneous oxygen uptake with spatial-temporal characteristics, correlating with cell proliferation and barrier changes, suggesting a fundamental mechanistic role of oxygen uptake in the skin in response to mechanical stretch. Optical fiber microsensor-based oxygen uptake detection provides a non-invasive approach to understand skin homeostasis.

Mixotrophic culture of Chaetoceros sp. and the synergistic carbon and energy metabolism.

This research studied the metabolic mechanism of the mixotrophic Chaetoceros sp. The results showed this alga had the highest cell density and growth rate of 47.72 × 105 cells mL-1 and 0.41 d-1, respectively, with a maximum dry weight of 2.90 g/L, when compared to photoautotrophic and photoheterotrophic modes. Compared to photoheterotrophy, transcriptomics results showed the Rubisco, PGK, and GAPDH related genes were separately up-regulated by 1.03, 2.36, and 1.36 times in CBB cycle in mixotrophic mode, suggesting intermediate metabolites of EMP and PPP can enter the chloroplast via transporter proteins, or membrane permeation, and feedback inhibition regulates the reduction of multiple reactions in CBB cycle. Chaetoceros sp. achieves high biomass by utilizing ATP and carbon structures from EMP and PPP pathways, and the addition of NaHCO3 leads to an up-regulation of CBB cycle for the mixotrophic alga, resulting in higher biomass compared to the photoheterotrophic mode.

Mechanical stiffness promotes skin fibrosis through Piezo1-mediated arginine and proline metabolism.

The increased mechanics of fibrotic skin tissue continuously regulate fibroblast functions such as survival and differentiation. Although all these processes consume metabolites, it is unclear whether and how cells adapt their metabolic activity to increased matrix stiffness. Here, we show that transferring mouse dermal fibroblasts from soft to stiff substrates causes an up-regulation of arginine and proline metabolism. Increased matrix stiffness stimulates the expression and activity of key metabolic enzymes, leading to the synthesis of L-proline, a major source of collagen. In addition, the novel mechanosensitive channel Piezo1 was identified as a key regulator of arginine and proline metabolism in fibroblasts under increased stiffness. Consistently, targeting Piezo1 to dermal fibroblasts in vivo effectively reduces fibrosis and arginine-proline metabolism in mouse skin. Therefore, mechanical stiffness is a critical environmental cue for fibroblast metabolism and skin fibrosis progression.

Mixotrophy, a more promising culture mode: Multi-faceted elaboration of carbon and energy metabolism mechanisms to optimize microalgae culture.

Some mixotrophic microalgae appear to exceed the sum of photoautotrophy and heterotrophy in terms of biomass production. This paper mainly reviews the carbon and energy metabolism of microalgae to reveal the synergistic mechanisms of the mixotrophic mode from multiple aspects. It explains the shortcomings of photoautotrophic and heterotrophic growth, highlighting that the mixotrophic mode is not simply the sum of photoautotrophy and heterotrophy. Specifically, microalgae in mixotrophic mode can be divided into separate parts of photoautotrophic and heterotrophic cultures, and the synergistic parts of photoautotrophic culture enhance aerobic respiration and heterotrophic culture enhance the Calvin cycle. Additionally, this review argues that current deficiencies in mixotrophic culture can be improved by uncovering the synergistic mechanism of the mixotrophic mode, aiming to increase biomass growth and improve quality. This approach will enable the full utilization of advantagesin various fields, and provide research directions for future microalgal culture.

Recent advances in strategies to target the behavior of macrophages in wound healing.

Chronic wounds and scar formation are widespread due to limited suitable remedies. The macrophage is a crucial regulator in wound healing, controlling the onset and termination of inflammation and regulating other processes related to wound healing. The current breakthroughs in developing new medications and drug delivery methods have enabled the accurate targeting of macrophages in oncology and rheumatic disease therapies through clinical trials. These successes have cleared the way to utilize drugs targeting macrophages in various disorders. This review thus summarizes macrophage involvement in normal and pathologic wound healing. It further details the targets available for macrophage intervention and therapeutic strategies for targeting the behavior of macrophages in tissue repair and regeneration.

Stem cell therapy combined with controlled release of growth factors for the treatment of sphincter dysfunction.

Sphincter dysfunction often occurs at the end of tubule organs such as the urethra, anus, or gastroesophageal sphincters. It is the primary consequence of neuromuscular impairment caused by trauma, inflammation, and aging. Despite intensive efforts to recover sphincter function, pharmacological treatments have not achieved significant improvement. Cell- or growth factor-based therapy is a promising approach for neuromuscular regeneration and the recovery of sphincter function. However, a decrease in cell retention and viability, or the short half-life and rapid degradation of growth factors after implantation, remain obstacles to the translation of these therapies to the clinic. Natural biomaterials provide unique tools for controlled growth factor delivery, which leads to better outcomes for sphincter function recovery in vivo when stem cells and growth factors are co-administrated, in comparison to the delivery of single therapies. In this review, we discuss the role of stem cells combined with the controlled release of growth factors, the methods used for delivery, their potential therapeutic role in neuromuscular repair, and the outcomes of preclinical studies using combination therapy, with the hope of providing new therapeutic strategies to treat incontinence or sphincter dysfunction of the urethra, anus, or gastroesophageal tissues, respectively.

Repositioning of experimentally validated anti-breast cancer peptides to target FAK-PAX complex to halt the breast cancer progression: a biomolecular simulation approach.

FAK (focal adhesin kinase), a tyrosine kinase, plays an imperative role in cell-cell communication, particularly in cell signaling systems. It is a multi-functional signaling protein, which integrates and transduces signals into cancer cells through growth factor receptors or integrin and its interaction with Paxillin (PAX). The molecular processes by which FAK promotes the development and progression of cancer have progressively established the possible relationship between FAK-PAX complex in many types of cancer. The interaction of FAX and PAX is very important in breast cancer and thus acts as an essential biomarker for drugs, vaccines or peptide inhibitor designing. In this regard, computational approaches, particularly peptide designing to target the binding interface of the interacting partners, would greatly assist the design of peptide inhibitors against various cancer. Accordingly, in this present study, we screened 236 experimentally validated anti-breast cancer peptides using computational drugs repositioning approach to design peptides targeting the FAK-PAX complex. Using protein-peptide docking the binding site for the HP1 was confirmed and a total of 236 anti-breast cancer peptides were screened. Among the 236, only 12 peptides reported a docking score better than the control. From these 12, Magainin with the docking score - 103.8 ± 10.3 kcal/mol, NRC-07 with the docking score - 100.8 ± 16.5 kcal/mol, and Indolicidin with the docking score - 101.7 ± 3.9 kcal/mol, peptides potentially inhibit the FAX-PAX binding. Calculation of protein's motion and FEL revealed the binding and inhibitory behavior. Moreover, binding free energy (MM/GBSA) confirmed that Magainin exhibited the total binding energy - 53.28 kcal/mol, NRC-07 possessed the TBE - 44.16 kcal/mol, and Indolicidin reported the TBE of - 40.48 kcal/mol, thus explaining the inhibitory potential of these peptides. In conclusion, these peptides exhibit strong inhibitory potential and could abrogate the FAK-PAX complex in in vitro models and thus may relieve the burden of breast cancer.

Mechanical Stretch Triggers Epithelial-Mesenchymal Transition in Keratinocytes Through Piezo1 Channel.

The epithelial-mesenchymal transition (EMT) process has emerged as a central regulator of embryonic development, tissue repair and tumor malignancy. In recent years, researchers have specifically focused on how mechanical signals drive the EMT program in epithelial cells. However, how epithelial cells specifically leverage mechanical force to control the EMT process remains unclear. Here, we show that the bona fide mechanically activated cation channel Piezo1 plays a critical role in the EMT. The Piezo1 is expressed in human primary epidermal keratinocytes (HEKs) and is responsible for the mechanical stretch-induced Ca2+ concentration. Inhibition of Piezo1 activation by the inhibitor GsMTx4 or by siRNA-mediated Piezo1 knockdown influenced the morphology and migration of HEKs. Moreover, Piezo1 activity also altered EMT-correlated markers expression in response to mechanical stretch. We propose that the mechanically activated cation channel Piezo1 is an important determinant of mechanical force-induced EMT in keratinocytes and might play similar roles in other epithelial cells.

Mechanical stretch promotes hypertrophic scar formation through mechanically activated cation channel Piezo1.

Hypertrophic scar (HS) formation is a skin fibroproliferative disease that occurs following a cutaneous injury, leading to functional and cosmetic impairment. To date, few therapeutic treatments exhibit satisfactory outcomes. The mechanical force has been shown to be a key regulator of HS formation, but the underlying mechanism is not completely understood. The Piezo1 channel has been identified as a novel mechanically activated cation channel (MAC) and is reportedly capable of regulating force-mediated cellular biological behaviors. However, the mechanotransduction role of Piezo1 in HS formation has not been investigated. In this work, we found that Piezo1 was overexpressed in myofibroblasts of human and rat HS tissues. In vitro, cyclic mechanical stretch (CMS) increased Piezo1 expression and Piezo1-mediated calcium influx in human dermal fibroblasts (HDFs). In addition, Piezo1 activity promoted HDFs proliferation, motility, and differentiation in response to CMS. More importantly, intradermal injection of GsMTx4, a Piezo1-blocking peptide, protected rats from stretch-induced HS formation. Together, Piezo1 was shown to participate in HS formation and could be a novel target for the development of promising therapies for HS formation.

EZH2 Regulates the Correlation between Skin Regeneration and the Duration of Mechanical Stretch.

It has been widely recognized that mechanical stretch can regulate the fate of stem cells (SCs). Previous research has shown that short-term mechanical stretch induces SC proliferation by activating the predominant transcription factor YAP, and YAP is a critical modulator in controlling epidermal proliferation. However, our study finds that after this phase, cell growth arrest appears, which is induced by long-term mechanical stretch. In the interfollicular epidermal SCs undergoing long-term mechanical stretch in vivo and in vitro, the level of H3K27me3 and its histone methyltransferase EZH2 are significantly elevated with suppressed expression of the target genes of YAP. EZH2 forms repressive H3K27me3 that suppresses gene transcription. Small-molecule inhibitor of EZH2 rescues significantly the cell growth arrest in interfollicular epidermal SCs induced by long-term mechanical stretch, thus promoting epidermal proliferation in vivo again. These findings reveal that there is an unexpected correlation between SC proliferation and the duration of mechanical stretch regulated by EZH2. This study of long-term mechanical stretch that induces cell growth arrest provides a strategy for clinical translation to promote skin regeneration.

Correction to: Galangin inhibits hypertrophic scar formation via ALK5/Smad2/3 signaling pathway.

In the original article, Figs. 3b, 4a, c and 5d were published incorrectly. The correct version of the figures are provided in this correction.

Mechanical stretch promotes tumoricidal M1 polarization via the FAK/NF-κB signaling pathway.

Macrophages (Mφs) can be used as a part of cell-based cancer immunotherapy. However, they may be hampered by a failure to effectively and stably regulate their polarization state to enhance their tumoricidal effects. In this work, mechanical stretch (MS), as a biology-free modulatory method, was shown to enhance M1 polarization and tumoricidal effects. By using an in vitro Flexcell Tension system, we found that murine Mφ RAW264.7 cells showed higher M1 polarization-related mRNA expression and cytokine release after MS. Further molecular analyses found that focal adhesion kinase and NF-κB activation occurred in the MS-induced M1 polarization. Coculture of MS-preconditioned Mφ with B16F10 skin melanoma cells in vitro showed that the proliferation of B16F10 cells decreased, whereas caspase-3-induced apoptosis increased. Importantly, the injection of MS-preconditioned Mφ into murine skin melanomas in vivo impeded tumor growth; lesions were characterized by increased amounts of M1 Mφ, decreased tumor cell proliferation, and increased tumor cell apoptosis in the tumor microenvironment. Together, our results suggest that MS could be used as a simple preconditioning approach to prepare tumoricidal M1 Mφ for cancer immunotherapy.-Shan, S., Fang, B., Zhang, Y., Wang, C., Zhou, J., Niu, C., Gao, Y., Zhao, D., He, J., Wang, J., Zhang, X., Li, Q. Mechanical stretch promotes tumoricidal M1 polarization via the FAK/NF-κB signaling pathway.

Alisol A attenuates high-fat-diet-induced obesity and metabolic disorders via the AMPK/ACC/SREBP-1c pathway.

Obesity and its associated metabolic disorders such as diabetes, hepatic steatosis and chronic heart diseases are affecting billions of individuals. However there is no satisfactory drug to treat such diseases. In this study, we found that alisol A, a major active triterpene isolated from the Chinese traditional medicine Rhizoma Alismatis, could significantly attenuate high-fat-diet-induced obesity. Our biochemical detection demonstrated that alisol A remarkably decreased lipid levels, alleviated glucose metabolism disorders and insulin resistance in high-fat-diet-induced obese mice. We also found that alisol A reduced hepatic steatosis and improved liver function in the obese mice model.In addition, protein expression investigation revealed that alisol A had an active effect on AMPK/ACC/SREBP-1c pathway. As suggested by the molecular docking study, such bioactivity of alisol A may result from its selective binding to the catalytic region of AMPK.Therefore, we believe that Alisol A could serve as a promising agent for treatment of obesity and its related metabolic diseases.

The effects of mechanical stretch on the biological characteristics of human adipose-derived stem cells.

Adipose-derived stem cells (ADSCs) are a subset of mesenchymal stem cells (MSCs), which have promised a vast therapeutic potential in tissue regeneration. Recent studies have demonstrated that combining stem cells with mechanical stretch may strengthen the efficacy of regenerative therapies. However, the exact influences of mechanical stretch on MSCs still remain inconclusive. In this study, human ADSCs (hADSCs) were applied cyclic stretch stimulation under an in vitro stretching model for designated duration. We found that mechanical stretch significantly promoted the proliferation, adhesion and migration of hADSCs, suppressing cellular apoptosis and increasing the production of pro-healing cytokines. For differentiation of hADSCs, mechanical stretch inhibited adipogenesis, but enhanced osteogenesis. Long-term stretch could promote ageing of hADSCs, but did not alter the cell size and typical immunophenotypic characteristics. Furthermore, we revealed that PI3K/AKT and MAPK pathways might participate in the effects of mechanical stretch on the biological characteristics of hADSCs. Taken together, mechanical stretch is an effective strategy for enhancing stem cell behaviour and regulating stem cell fate. The synergy between hADSCs and mechanical stretch would most likely facilitate tissue regeneration and promote the development of stem cell therapy.