Metformin mitigates adipogenesis of fibro-adipogenic progenitors after rotator cuff tears via activating mTOR/ULK1-mediated autophagy.

Muscular fatty infiltration is a common issue after rotator cuff tears (RCTs), which impair shoulder function. Females suffer a higher prevalence and a more severe degree of muscular fatty infiltration after RCT when compared with males, with the underlying mechanisms remaining unclear. Fibro-adipogenic progenitors (FAPs) are the primary source of muscular fatty infiltration following RCT. Our findings disclose that gender-specific disparities in muscular fatty infiltration are linked to mTOR/ULK1-mediated autophagy of FAPs. Decreased autophagic activity contributes to adipogenic differentiation in female FAPs after RCT. Furthermore, metformin could enhance mTOR/ULK1-mediated autophagic processes of FAPs, thereby alleviating fatty infiltration and improving shoulder functionality after RCT. Together, our study reveals that gender differences in muscular fatty infiltration arise from distinct autophagic activities. Metformin could be a promising noninvasive intervention to ameliorate muscular fatty infiltration of RCT.NEW & NOTEWORTHY The current study demonstrated that gender-specific disparities in muscular fatty infiltration are attributed to mTOR/ULK1-mediated autophagy of FAPs. Decreased autophagic activity contributes to adipogenic differentiation in female FAPs after RCT. Moreover, metformin could enhance mTOR/ULK1-mediated autophagic processes of FAPs, thereby alleviating fatty infiltration and improving shoulder functionality after RCT. Therefore, metformin could be a promising noninvasive intervention to ameliorate muscular fatty infiltration of RCT.

Higher House Dust Mite-Specific IgE Levels among Chronic Spontaneous Urticaria Patients May Implicate Higher Basophil Reactivity.

INTRODUCTION: Allergen-specific IgE (sIgE) sensitization exists in a considerable fraction of chronic spontaneous urticaria (CSU) patients. Basophils have been implicated in the pathogenesis of CSU. This paper aimed to explore the relationship between allergic sensitization and basophil reactivity in CSU and the possible underlying mechanism. METHODS: Basophil-enriched leukocytes were isolated from the peripheral blood of 76 CSU patients and 9 healthy controls. Basophil CD63 and FcεRIα (the alpha subunit of the high-affinity IgE receptor) expression in the blood samples with various house dust mite (HDM)-sIgE levels were determined by flow cytometry. Basophil reactivity and SHIP-1 (a molecule related to the IgE/FcεRI signaling pathway) expression were analyzed after stimulation with an HDM allergen or other stimuli. RESULTS: HDM-sIgEstrong positive (≥3.5 kU/L) CSU patients had a significantly higher mean percentage of basophil CD63 and higher baseline levels of FcεRIα expressed by basophils than HDM-sIgEnormal (<0.35 kU/L) CSU patients and healthy controls; the same went for total serum IgE. After stimulation with Dermatophagoides pteronyssinus peptidase 1 (Derp1) alone or together with Derp1-sIgE, the stimulation index of CD63 and levels of FcεRIα expressed by basophils in HDM-sIgEstrong positive CSU patients were significantly higher than those in HDM-sIgEnormal CSU patients and healthy controls. Significantly more SHIP-1 mRNA expression in HDM-sIgEstrong positive CSU patients was induced after the combined stimulation in comparison to other subjects. CONCLUSION: CSU patients with higher HDM-sIgE levels (≥3.5 kU/L) may have higher CD63 and FcεRIα expression on peripheral blood basophils. Peripheral blood basophils in these CSU patients are more responsive to HDM allergen stimulation. Higher HDM-sIgE levels among CSU patients may implicate higher basophil reactivity.

Single-cell RNA-seq reveals abnormal differentiation of keratinocytes and increased inflammatory differentiated keratinocytes in atopic dermatitis.

BACKGROUND: Atopic dermatitis (AD) is a chronic and recurrent inflammatory skin disease characterized by severe pruritus and eczematous lesions. Heterogeneity of AD has been reported among different racial groups according to clinical, molecular and genetic differences. OBJECTIVE: This study aimed to conduct an in-depth transcriptome analysis of AD in Chinese population. METHODS: We performed single-cell RNA sequencing (scRNA-seq) analysis of skin biopsies from five Chinese adult patients with chronic AD and from four healthy controls, combined with multiplexed immunohistochemical analysis in whole-tissue skin biopsies. We explored the functions of IL19 in vitro. RESULTS: ScRNA-seq analysis was able to profile a total of 87,853 cells, with keratinocytes (KCs) in AD manifesting highly expressed keratinocyte activation and pro-inflammatory genes. KCs demonstrated a novel IL19+ IGFL1+ subpopulation that increased in AD lesions. Inflammatory cytokines IFNG, IL13, IL26 and IL22 were highly expressed in AD lesions. In vitro, IL19 directly downregulated KRT10 and LOR in HaCaT cells and activated HaCaT cells to produce TSLP. CONCLUSION: Abnormal proliferation and differentiation of keratinocytes contribute immensely to the pathogenesis of AD, whereas AD chronic lesions have witnessed significant presence of IL19+ IGFL1+ KCs, which may be involved in the disruption of the skin barrier, the connection and magnification of Th2 and Th17 inflammatory responses, and mediation of skin pruritus. Furthermore, progressive activation of multiple immune axes dominated by Type 2 inflammatory reaction occur in AD chronic lesions.

Suppressed Akt/GSK-3ß/ß-catenin signaling contributes to excessive adipogenesis of fibro-adipogenic progenitors after rotator cuff tears.

Muscular fatty infiltration is a common and troublesome pathology after rotator cuff tears (RCT), which mainly derives from fibro-adipogenic progenitors (FAPs). Compared to the RCT, fatty infiltration is not so severe in Achilles tendon tears (ATT). The knowledge of why fatty infiltration is more likely to occur after RCT is limited. In this study, more severe fatty infiltration was verified in supraspinatus than gastrocnemius muscles after tendon injury. Additionally, we revealed higher adipogenic differentiation ability of RCT-FAPs in vitro. Activation of Akt significantly stimulated GSK-3ß/ß-catenin signaling and thus decreased PPARγ expression and adipogenesis of RCT-FAPs, while the inhibition effect was attenuated by ß-catenin inhibitor. Furthermore, Wnt signaling activator BML-284 limited adipogenesis of RCT-FAPs, alleviated muscular fatty infiltration, and improved parameters in gait analysis and treadmill test for RCT model. In conclusion, our study demonstrated that suppressed Akt/GSK-3ß/ß-catenin signaling increased PPARγ expression and thus contributed to excessive adipogenesis in RCT-FAPs. Modulation of Akt/GSK-3ß/ß-catenin signaling ameliorated excessive fatty infiltration of rotator cuff muscles and improved shoulder function after RCT.

An Atopic Dermatitis-Like Mouse Model by Alternate Epicutaneous Application of Dinitrofluorobenzene and an Extract of Dermatophagoides Farinae.

Several studies have tried to establish mice models of atopic dermatitis (AD) through the allergen of Dermatophagoides farinae (Df). However, there are no typical skin lesions after epicutaneous application of an extract of Df (DfE) on BALB/c mice. Dinitrofluorobenzene (DNFB) is a common hapten that brings about contact dermatitis. Skin dysfunction induced by DNFB may be a way to enhance the effects of DfE on mice skin. Thus, we hypothesized that alternate epicutaneous application of DNFB and DfE could induce AD-like skin lesions on BALB/c mice. To test this hypothesis, we alternately applied the DNFB and DfE to the back skin of BALB/c mice for 8 weeks. Changes in mice skin lesions and the frequency of scratching behavior were recorded. The variation of Th1-related cytokines (interferon-γ [IFN-γ] and interleukin two [IL-2]) and Th2-related cytokines (IL-4 and IL-13) was detected in serum and lesional skin. Eventually, the BALB/c mice developed severe erythema, erosion, scarring, and excoriation on the entire back, showing a high frequency of scratching behavior. In addition, Th2 cells' dominant cytokines appeared in both serum and lesional skin. Those results indicate that alternating epicutaneous exposure to DNFB and DfE can produce AD-like models with typical clinical features and Th2-type immune responses in BALB/c mice. This model could be valuable for studying the pathogenesis of AD and developing novel therapeutic agents for it.

Allergen-specific immunotherapy induces monocyte-derived dendritic cells but attenuates their maturation and cytokine production in the lesional skin of an atopic dermatitis mouse model.

Atopic dermatitis (AD) is a common inflammatory skin disease, but current treatments for AD are mostly limited to the alleviation of symptoms and inhibition of inflammation. Allergen-specific immunotherapy (ASIT) is the only curative approach for allergic diseases and could be a promising way to cure AD. Although ASIT has been gradually applied to patients with AD, there are still few studies on its efficacy evaluation and mechanisms. Based on our previous established AD mouse model by dinitrofluorobenzene and an extract of Dermatophagoides farina, we performed ASIT on this AD model through subcutaneous injection of Dermatophagoides farina extracts to evaluate the efficacy of ASIT and study its underlying mechanisms. Our results showed that ASIT could not only alleviate skin lesions and scratching behaviors of AD mice but also inhibit their Th2-type immune responses. Furthermore, ASIT could increase the infiltration of monocyte-derived dendritic cells in skin lesions but attenuated their maturation and production of interleukin 1α and interleukin 12/23 p40. As immature and semi-mature dendritic cells preferentially induce tolerance, accumulation but inhibition of maturation of monocyte-derived dendritic cells after ASIT may indicate a novel mechanism of ASIT and a potential therapeutic target for AD.