Research
Abstract
Skeletal muscle regeneration in adults is predominantly driven by satellite cells. Loss of satellite cell pool and function leads to skeletal muscle wasting in many conditions and disease states. Here, we demonstrate that the levels of fibroblast growth factor-inducible 14 (Fn14) were increased in satellite cells after muscle injury. Conditional ablation of Fn14 in Pax7-expressing satellite cells drastically reduced their expansion and skeletal muscle regeneration following injury. Fn14 was required for satellite cell self-renewal and proliferation as well as to prevent precocious differentiation. Targeted deletion of Fn14 inhibited Notch signaling but led to the spurious activation of STAT3 signaling in regenerating skeletal muscle and in cultured muscle progenitor cells. Silencing of STAT3 improved proliferation and inhibited premature differentiation of Fn14-deficient satellite cells. Furthermore, conditional ablation of Fn14 in satellite cells exacerbated myopathy in the mdx mouse model of Duchenne muscular dystrophy (DMD) whereas its overexpression improved the engraftment of exogenous muscle progenitor cells into the dystrophic muscle of mdx mice. Altogether, our study highlights the crucial role of Fn14 in the regulation of satellite cell fate and function and suggests that Fn14 can be a potential molecular target to improve muscle regeneration in muscular disorders.
Authors
Meiricris Tomaz da Silva, Aniket S. Joshi, Ashok Kumar
Abstract
Somatic activating mutations in KRAS can cause complex lymphatic anomalies (CLAs). However, the specific processes that drive KRAS-mediated CLAs have yet to be fully elucidated. Here, we used single-cell RNA sequencing to construct an atlas of normal and KrasG12D-malformed lymphatic vessels. We identified six subtypes of lymphatic endothelial cells (LECs) in the lungs of adult wild-type mice (Ptx3, capillary, collecting, valve, mixed, and proliferating). To determine when the LEC subtypes were specified during development, we integrated our data with data from four stages of development. We found that proliferating and Ptx3 LECs were prevalent during early lymphatic development and that collecting and valve LECs emerged later in development. Additionally, we discovered that the proportion of Ptx3 LECs decreased as the lymphatic network matured but remained high in KrasG12D mice. We also observed that the proportion of collecting and valve LECs was lower in KrasG12D mice than in wild-type mice. Last, we found that immature lymphatic vessels in young mice were more sensitive to the pathologic effects of KrasG12D than mature lymphatic vessels in older mice. Together, our results expand the current model for the development of the lymphatic system and suggest that KRAS mutations impair the maturation of lymphatic vessels.
Authors
Lorenzo M. Fernandes, Danielle Griswold-Wheeler, Jeffrey D. Tresemer, Angelica Vallejo, Neda Vishlaghi, Benjamin Levi, Abigail Shapiro, Joshua P. Scallan, Michael T. Dellinger
Abstract
CD8+ T cells are critical for immune protection against severe COVID-19 during acute infection with SARS-CoV-2. However, the induction of antiviral CD8+ T cell responses varies substantially among infected people, and a better understanding of the mechanisms that underlie such immune heterogeneity is required for pandemic preparedness and risk stratification. In this study, we analyzed SARS-CoV-2-specific CD4+ and CD8+ T cell responses in relation to age, clinical status, and inflammation among patients infected primarily during the initial wave of the pandemic in France or Japan. We found that age-related contraction of the naive lymphocyte pool and systemic inflammation were associated with suboptimal SARS-CoV-2-specific CD4+ and, even more evidently, CD8+ T cell immunity in patients with acute COVID-19. No such differences were observed for humoral immune responses targeting the spike protein of SARS-CoV-2. We also found that the proinflammatory cytokine IL-18, concentrations of which were significantly elevated among patients with severe disease, suppressed the de novo induction and memory recall of antigen-specific CD8+ T cells, including those directed against SARS-CoV-2. These results potentially explain the vulnerability of older adults to infections that elicit a profound inflammatory response, exemplified by acute COVID-19.
Authors
Gaëlle Autaa, Laura Papagno, Takuto Nogimori, Andrea Boizard-Moracchini, Daniil Korenkov, Maeva Roy, Koichiro Suzuki, Yuji Masuta, Eoghann White, Sian Llewellyn-Lacey, Yasuo Yoshioka, Francesco Nicoli, David A. Price, Julie Dechanet-Merville, Takuya Yamamoto, Isabelle Pellegrin, Victor Appay
Abstract
Urinary obstruction causes injury to the renal medulla, impairing the ability to concentrate urine, and increasing the risk of progressive kidney disease. However, the regenerative capacity of the renal medulla after reversal of obstruction is poorly understood. To investigate this, we developed a mouse model of reversible urinary obstruction. Despite robust regeneration and complete histological recovery of the renal medulla, these mice exhibited a permanent defect in urinary concentrating capacity. However, there were lasting changes in the composition, organization, and transcriptional profiles of epithelial, endothelial, and interstitial cells. Persistent inflammatory responses were also seen in patients with renal stone disease, but there were also adaptive responses to the increasingly hypoxic environment of the renal medulla that only occurred after reversal of obstruction. These findings indicate that while partial repair occurs after reversal of urinary obstruction, there are lasting structural and functional changes across all major cellular compartments of the renal medulla. These changes reflect shared and distinct responses to different renal medullary injuries in humans and mice.
Authors
Thitinee Vanichapol, Alex Gonzalez, Rachel Delgado, Maya Brewer, Kelly A. Clouthier, Anna A. Menshikh, William E. Snyder, Teebro Rahman, Veronika Sander, Haichun Yang, Alan Davidson, Mark Caestecker
Abstract
Chronic wounds have emerged as a tough clinical challenge. An improved understanding of wound healing mechanisms is paramount. Collagen XVII (COL17), a pivotal constituent of hemidesmosomes, holds considerable promise for regulating epidermal cell adhesion to the basement membrane, as well as for epidermal cell motility and self-renewal of epidermal stem cells. However, the precise role of COL17 in wound repair remains elusive, and the upstream regulatory mechanisms involved have not been fully elucidated. In this study, we delineated the temporal and spatial expression patterns of COL17 at the epidermal wound edge. Subsequently, we investigated the indispensable role of COL17 in keratinocyte activation and re-epithelialization during wound healing, demonstrating the restoration of the normal repair process by COL17 overexpression in diabetic wounds. Notably, we identified a key transcriptional signaling pathway for COL17, wherein PKM2 (Pyruvate kinase isozyme M2) promotes phosphorylation of STAT3, leading to its activation and subsequent induction of COL17 expression upon injury. Ultimately, by manipulating this pathway using the PKM2 nuclear translocator SAICAR, we revealed a promising therapeutic strategy for enhancing the healing of chronic wounds.
Authors
Yangdan Liu, Chia-kang Ho, Dongsheng Wen, Jiaming Sun, Yuxin Liu, Qing-Feng Li, Yifan Zhang, Ya Gao
Abstract
The impact of remdesivir on SARS-CoV-2 diversity and evolution in vivo has remained unclear. In this single-center, retrospective cohort study, we assessed SARS-CoV-2 diversification and diversity over time in a cohort of hospitalized patients who did or did not receive remdesivir. Whole genome sequencing was performed on 98 paired specimens collected from 49 patients before and after remdesivir administration. Genetic divergence between paired specimens was not significantly different from what was observed in paired specimens from patients who did not receive the drug. However, when comparing minority variants, several positions showed preferential diversification after remdesivir treatment, several of which were associated with different variants of concern. Most notably, remdesivir administration resulted in strong selection for a nonsynonymous mutation in nsp12, G671S, previously associated with enhanced viral fitness. This same mutation was found enriched in a second cohort of 143 inpatients with specimens collected after remdesivir administration compared to controls. Only one other mutation previously implicated in remdesivir resistance (nsp12:V792I) was found to be preferentially selected for after remdesivir administration. These data suggest that SARS-CoV-2 variants with enhanced replicative fitness may be selected for in the presence of antiviral therapy as an indirect means to overcome this selective pressure.
Authors
Ted Ling-Hu, Lacy M. Simons, Estefany Rios-Guzman, Alexandre M. Carvalho, Maria Francesca R. Agnes, Arghavan Alisoltanidehkordi, Egon A. Ozer, Ramon Lorenzo-Redondo, Judd F. Hultquist
Abstract
Surgery of the tracheobronchial tree carries high morbidity, with over half of the complications occurring at the anastomosis. Although fibroblasts are crucial in airway wound healing, the underlying cellular and molecular mechanisms in airway reconstruction remain unknown. We hypothesized that airway reconstruction initiates a surgery-induced stress (SIS) response, altering fibroblast communication within airway tissues. Using single-cell RNAseq, we analyzed native and reconstructed airways and identified five fibroblast subpopulations, each with distinct spatial distributions across anastomotic, submucosal, perichondrial, and paratracheal areas. During homeostasis, Adventitial and Airway fibroblasts (Adventitial Fb and Airway Fb, respectively) maintained tissue structure and created cellular niches by regulating ECM turnover. Under SIS, Perichondrial fibroblasts (PC-Fb) exhibited chondroprogenitor-like gene signatures, and Immune-recruiting fibroblasts (IR-Fb) facilitated cell infiltration. Cthrc1 activated fibroblasts (Cthrc1+ Fb), mainly derived from Adventitial Fb, primarily contributed to fibrotic scar formation and collagen production, mediated by TGFβ. Furthermore, repeated SIS created an imbalance in fibroblast states favoring emergence of CTHRC1+ Fb and leading to impaired fibroblasts-basal cell crosstalk. Collectively, these data identify PC, IR, and Cthrc1+ Fb as a signaling hub, with SIS emerging as a mechanism initiating airway remodeling after reconstruction that, if not controlled, may lead to complications such as stenosis or anastomotic breakdown.
Authors
Jazmin Calyeca, Zakarie Hussein, Zheng Hong Tan, Lumei Liu, Sayali Dharmadhikari, Kimberly M. Shontz, Tatyana A. Vetter, Christopher K. Breuer, Susan D. Reynolds, Tendy Chiang
Abstract
Endometriosis is a chronic gynecological disease that affects 1 in 10 reproductive-aged women. Most studies investigate established disease; however, the initiation and early events in endometriotic lesion development remain poorly understood. Our study used neutrophils from human menstrual effluent from subjects with and without endometriosis for immunophenotyping, and a mouse model of endometriosis and a mouse endometriosis cell line to determine the role of neutrophils in the initiating events of endometriosis, including attachment and survival of minced endometrial pieces. In menstrual effluent from women with endometriosis, the ratio of aged and pro-angiogenic neutrophils increased compared to controls, indicating a potentially permissive pro-inflammatory microenvironment. In our endometriosis mouse model, knocking-down neutrophil recruitment with α-CXCR2 into the peritoneum decreased endometrial tissue adhesion—supported by decreased levels of myeloperoxidase and neutrophil elastase in both developing lesions and peritoneal fluid. Fibrinogen was identified as the preferred substrate for endometrial cell adhesion in an in vitro adhesion assay and in developing lesions in vivo. Together, aged and pro-angiogenic neutrophils and their secretions likely promote attachment and formation of endometriotic lesions by releasing neutrophil extracellular traps and upregulating fibrinogen expression as a provisional matrix to establish attachment and survival in the development of endometriosis lesions.
Authors
Taylor R. Wilson, Kurt R. Peterson, Stephanie A. Morris, Damaris Kuhnell, Susan Kasper, Katherine A. Burns
Abstract
Aortic dissection or rupture is a major cause of mortality in vascular Ehlers-Danlos Syndrome (vEDS), a connective tissue disorder caused by heterozygous mutations in the COL3A1 gene. C57BL6/J (BL6) mice carrying the Col3a1 G938D/+ mutation recapitulate the vEDS vascular phenotype and die suddenly of aortic rupture/dissection. However, 129S6/SvEvTac (129) mice expressing the same Col3a1 G938D/+ mutation show near-complete life-long protection from vascular rupture. To identify genetic modifiers of vascular risk in vEDS, we performed genome-wide genotyping of intercrossed BL6/129 vEDS mice stratified by survival and identified a significant protective locus encompassing a variant in Map2k6, encoding Mitogen-Activated Protein Kinase Kinase 6 (M2K6), a p38-activating kinase. Genetic ablation of Map2k6 rendered previously protected 129 vEDS mice susceptible to aortic rupture, in association with reduced protein phosphatase 1 activity and increased PKC and ERK phosphorylation. Accelerated vascular rupture in vEDS mice treated with a pharmacological inhibitor of p38 was rescued by concomitant ERK antagonism, supporting an opposing role for ERK and p38 in the modification of aortic rupture risk in vEDS. These results suggest that pharmacologic strategies aimed at mimicking the effect of this natural protective pathway may improve prevention of aortic rupture risk in vEDS.
Authors
Caitlin J. Bowen, Rebecca Sorber, Juan F. Calderon Giadrosic, Jefferson J. Doyle, Graham Rykiel, Zachary Burger, Xiaoyan Zhang, Wendy A. Espinoza Camejo, Nicole K. Anderson, Simone Sabnis, Chiara Bellini, Elena MacFarlane, Harry C. Dietz
Abstract
Hereditary angioedema is an autosomal dominant disorder caused by defects in C1-esterase inhibitor (C1-INH), resulting in poorly controlled activation of the kallikrein-kinin system and bradykinin overproduction. C1-INH is a heavily glycosylated protein in the serine protease inhibitor (SERPIN) family, yet the role of these glycosylation sites remains unclear. To elucidate the functional impact of N-glycosylation in the SERPIN domain of C1-INH, we engineered four sets consisting of 26 variants at or near the N-linked sequon (NXS/T). Among these, six are reported in HAE patients and five are known C1-INH variants without accessible clinical histories. We systematically evaluated their expression, structure and functional activity with C1¯s, FXIIa and kallikrein. Our findings showed that of the eleven reported variants, seven are deleterious. Deleting N at the three naturally occurring N-linked sequons (N238, N253 and N352) results in pathologic consequences. Altering these sites by substituting N to A disrupts N-linked sugar attachment but preserves protein expression or function. Further, an additional N-linked sugar generated at N272 impairs C1-INH function. These findings highlight the importance of N-linked sequons in modulating the expression and function of C1-INH. Insights gained from identifying the pathological consequences of N-glycan variants should assist in defining more tailored therapy.
Authors
Zhen Ren, John Bao, Shuangxia Zhao, Nicola Pozzi, H. Wedner, John P. Atkinson
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