Stem cells
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
The oral mucosa undergoes daily insults, and stem cells in the epithelial basal cell layer regenerate gingiva tissue to maintain oral health. The Iroquois Homeobox 1 (IRX1) protein is expressed in the stem cell niches in human/mouse oral epithelium and mesenchyme under homeostasis. We found that Irx1+/– heterozygous (Het) mice have delayed wound closure, delayed morphological changes of regenerated epithelium, and defective keratinocyte proliferation and differentiation during wound healing. RNA-Seq analyses between WT and Irx1+/– mice at 3 days postinjury (dpi) found impaired epithelial migration and decreased keratinocyte-related genes upon injury. IRX1-expressing cells are found in the gingival epithelial basal cell layer, a stem cell niche for gingival maintenance. IRX1-expressing cells are also found in cell niches in the underlying stroma. IRX1 activates SOX9 in the transient amplifying layer to increase cell proliferation, and EGF signaling is activated to induce cell migration. Krt14CreERT lineage tracing experiments reveal defects in the stratification of the Irx1+/– HET mouse oral epithelium. IRX1 is primed at the base of the gingiva in the basal cell layer of the oral epithelium, facilitating rapid and scarless wound healing through activating SOX9 and the EGF signaling pathway.
Authors
Dan Su, Tadkamol Krongbaramee, Samuel Swearson, Yan Sweat, Mason Sweat, Fan Shao, Steven Eliason, Brad A. Amendt
Abstract
Aniridia is a rare congenital condition of abnormal eye development arising principally from heterozygous mutation of the PAX6 gene. Among the multiple complications arising in the eye, aniridia-associated keratopathy (AAK) is a severe vision-impairing condition of the cornea associated with a progressive limbal stem cell deficiency that lacks suitable treatment options. Current mouse models of aniridia do not accurately represent the onset and progression dynamics of human AAK, hindering therapy development. Here, we performed deep phenotyping of a haploinsufficient Pax6+/– small-eye (Sey) mouse model on the129Sey/SvImJ background, that exhibits key features of mild presentation at birth and progressive AAK with aging, mimicking human disease. The model exhibits a slowly progressing AAK phenotype and provides new insights into the disease including disturbed basal epithelial cell organization, function and marker expression, persistent postnatal lymphangiogenesis, disrupted corneal innervation patterns, and persisting yet altered limbal stem cell marker expression with age. The model recapitulates many of the known features of human disease, enabling investigation of underlying disease mechanisms and importantly, to access a well-defined temporal window for evaluating future therapeutics.
Authors
Dina Javidjam, Petros Moustardas, Mojdeh Abbasi, Ava Dashti, Yedizza Rautavaara, Neil Lagali
Abstract
Human periosteal skeletal stem cells (P-SSCs) are critical for cortical bone maintenance and repair. However, their in vivo identity, molecular characteristics, and specific markers remain unknown. Here, single-cell sequencing revealed human periosteum contains SSC clusters expressing known SSC markers, PDPN and PDGFRA. Notably, human P-SSCs, but not bone marrow SSCs (BM-SSCs), selectively expressed newly identified markers, LRP1 and CD13. These LRP1+CD13+ human P-SSCs were perivascular cells with high osteochondrogenic but minimal adipogenic potential. Upon transplantation into bone injuries in mice, they preserved self-renewal capability in vivo. Single-cell analysis of mouse periosteum further supported the preferential expression of LRP1 and CD13 in Prx1+ P-SSCs. When Lrp1 was conditionally deleted in Prx1-lineage cells, it led to severe bone deformity, short statue, and periosteal defects. By contrast, local treatment with a LRP1 agonist at the injury sites induced early P-SSC proliferation and bone healing. Thus, human and mouse periosteum contains unique osteochondrogenic stem cell subsets, and these P-SSCs express specific markers, LRP1 and CD13, with regulatory mechanism through LRP1 that enhances P-SSC function and bone repair.
Authors
Youngjae Jeong, Lorenzo R. Deveza, Laura Ortinau, Kevin Lei, John R. Dawson, Dongsu Park
Abstract
Fibrosis in the lung is thought to be driven by epithelial cell dysfunction and aberrant cell-cell interactions. Unveiling the molecular mechanisms of cellular plasticity and cell-cell interactions is imperative to elucidate lung regenerative capacity and aberrant repair in pulmonary fibrosis. By mining publicly available RNA-seq datasets, we identified loss of CCAAT enhancer-binding protein alpha (CEBPA) as a candidate contributor to idiopathic pulmonary fibrosis (IPF). We used conditional knockout mice, scRNA-seq, lung organoids, small-molecule inhibition and novel gene manipulation methods to investigate the role of CEBPA in lung fibrosis and repair. Long term (6 month+) of Cebpa loss in AT2 cells caused spontaneous fibrosis and increased susceptibility to bleomycin-induced fibrosis. Cebpa knockout in these mice significantly decreased AT2 cell numbers in the lung and reduced expression of surfactant homeostasis genes, while increasing inflammatory cell recruitment as well as upregulating S100a8/a9 in AT2 cells. In vivo treatment with an S100A8/A9 inhibitor alleviated experimental lung fibrosis. Restoring CEBPA expression in lung organoids ex vivo and during experimental lung fibrosis in vivo rescued CEBPA deficiency-mediated phenotypes. Our study establishes a direct mechanistic link between CEBPA repression, impaired AT2 cell identity, disrupted tissue homeostasis, and lung fibrosis.
Authors
Qi Tan, Jack H. Wellmerling, Shengren Song, Sara R. Dresler, Jeffrey A. Meridew, Kyoung M. Choi, Yong Li, Y.S. Prakash, Daniel J. Tschumperlin
Abstract
Despite epidermal turnover, the skin is host to a complex array of microbes including viruses, such as the human papillomavirus (HPV), which must infect and manipulate skin keratinocyte stem cells (KSC) to survive. This crosstalk between the virome and KSC populations remains largely unknown. Here, we investigated the effect of HPV8 on KSCs using various mouse models. We observed that the HPV8 early region gene E6 specifically caused Lrig1+ hair follicle junctional zone KSC proliferation and expansion, which would facilitate viral transmission. Within Lrig1+ KSCs specifically, HPV8 E6 bound intracellular p300 to phosphorylate the STAT3 transcriptional regulatory node. This induces ΔNp63 expression, resulting in KSC expansion into the overlying epidermis. HPV8 was associated with 70% of human actinic keratoses (AK). Together these results define the “hit and run” mechanism for HPV8 in human actinic keratosis as an expansion of KSCs, which lacks melanosome protection and is thus susceptible to sun-light-induced malignant transformation.
Authors
Huw J. Morgan, Carlotta Olivero, Boris Y. Shorning, Alex Gibbs, Alexandra L. Phillips, Lokapriya Ananthan, Annabelle Xiao Hui Lim, Licia Martuscelli, Cinzia Borgogna, Marco De Andrea, Martin Hufbauer, Richard G. Goodwin, Baki Akgül, Marisa Gariglio, Girish K. Patel
Abstract
Mesenchymal stem cells (MSCs) have demonstrated potent immunomodulatory properties that have shown promise in the treatment of autoimmune diseases, including rheumatoid arthritis (RA). However, the inherent heterogeneity of MSCs triggered conflicting therapeutic outcomes, raising safety concerns and limiting their clinical application. This study aimed to investigate the potential of extracellular vesicles derived from human gingival mesenchymal stem cells (GMSC-EVs) as a therapeutic strategy for RA. Through in vivo experiments using an experimental RA model, our results demonstrated that GMSC-EVs selectively homed to inflamed joints and recovered Treg and Th17 cells balance, resulting in the reduction of arthritis progression. Our investigations also uncovered miR-148a-3p as a critical contributor to the Treg/Th17 balance modulation via IKKB/NF-κB signaling orchestrated by GMSC-EVs, which was subsequently validated in a model of human xenograft versus host disease (xGvHD). Furthermore, we successfully developed a humanized animal model by utilizing synovial fibroblasts obtained from patients with RA (RASFs). We found that GMSC-EVs impeded the invasiveness of RASFs and minimized cartilage destruction, indicating their potential therapeutic efficacy in the context of RA patients. Overall, the unique characteristics, including reduced immunogenicity, simplified administration, and inherent ability to target inflamed tissues, position GMSC-EVs as a viable alternative for RA and other autoimmune diseases.
Authors
Jingrong Chen, Xiaoyi Shi, Yanan Deng, Junlong Dang, Yan Liu, Jun Zhao, Liang Rongzhen, Donglan Zeng, Wenbin Wu, Yiding Xiong, Jia Yuan, Ye Chen, Julie Wang, Weidong Lin, Xiangfang Chen, Weishan Huang, Nancy Olsen, Yunfeng Pan, Qing-Ling Fu, Song Guo Zheng
Abstract
Inherited retinal dystrophies (IRDs) are progressive diseases leading to vision loss. Mutation in the eyes shut homolog (EYS) gene is one of the most frequent causes of IRD. However, the mechanism of photoreceptor cell degeneration by mutant EYS has not been fully elucidated. Here, we generated retinal organoids from induced pluripotent stem cells (iPSCs) derived from patients with EYS-associated retinal dystrophy (EYS-RD). In photoreceptor cells of RD organoids, both EYS and G protein–coupled receptor kinase 7 (GRK7), one of the proteins handling phototoxicity, were not in the outer segment, where they are physiologically present. Furthermore, photoreceptor cells in RD organoids were vulnerable to light stimuli, and especially to blue light. Mislocalization of GRK7, which was also observed in eys-knockout zebrafish, was reversed by delivering control EYS into photoreceptor cells of RD organoids. These findings suggest that avoiding phototoxicity would be a potential therapeutic approach for EYS-RD.
Authors
Yuki Otsuka, Keiko Imamura, Akio Oishi, Kazuhide Asakawa, Takayuki Kondo, Risako Nakai, Mika Suga, Ikuyo Inoue, Yukako Sagara, Kayoko Tsukita, Kaori Teranaka, Yu Nishimura, Akira Watanabe, Kazuhiro Umeyama, Nanako Okushima, Kohnosuke Mitani, Hiroshi Nagashima, Koichi Kawakami, Keiko Muguruma, Akitaka Tsujikawa, Haruhisa Inoue
Abstract
Recently, skeletal stem cells were shown to be present in the epiphyseal growth plate (epiphyseal skeletal stem cells, epSSCs), but their function in connection with linear bone growth remains unknown. Here, we explore the possibility that modulating the number of epSSCs can correct differences in leg length. First, we examined regulation of the number and activity of epSSCs by Hedgehog (Hh) signaling. Both systemic activation of Hh pathway with Smoothened agonist (SAG) and genetic activation of Hh pathway by Patched1 (Ptch1) ablation in Pthrp-creER Ptch1fl/fl tdTomato mice promoted proliferation of epSSCs and clonal enlargement. Transient intra-articular administration of SAG also elevated the number of epSSCs. When SAG-containing beads were implanted into the femoral secondary ossification center of 1 leg of rats, this leg was significantly longer 1 month later than the contralateral leg implanted with vehicle-containing beads, an effect that was even more pronounced 2 and 6 months after implantation. We conclude that Hh signaling activates growth plate epSSCs, which effectively leads to increased longitudinal growth of bones. This opens therapeutic possibilities for the treatment of differences in leg length.
Authors
Dana Trompet, Anastasiia D. Kurenkova, Baoyi Zhou, Lei Li, Ostap Dregval, Anna P. Usanova, Tsz Long Chu, Alexandra Are, Andrei A. Nedorubov, Maria Kasper, Andrei S. Chagin
Abstract
Dysostosis multiplex is a major cause of morbidity in Hurler syndrome (mucopolysaccharidosis type IH [MPS IH], OMIM #607014) because currently available therapies have limited success in its prevention and reversion. Unfortunately, the elucidation of skeletal pathogenesis in MPS IH is limited by difficulties in obtaining bone specimens from pediatric patients and poor reproducibility in animal models. Thus, the application of experimental systems that can be used to dissect cellular and molecular mechanisms underlying the skeletal phenotype of MPS IH patients and to identify effective therapies is highly needed. Here, we adopted in vitro/in vivo systems based on patient-derived bone marrow stromal cells to generate cartilaginous pellets and bone rudiments. Interestingly, we observed that heparan sulphate accumulation compromised the remodeling of MPS IH cartilage into other skeletal tissues and other critical aspects of the endochondral ossification process. We also noticed that MPS IH hypertrophic cartilage was characterized by dysregulation of signaling pathways controlling cartilage hypertrophy and fate, extracellular matrix organization, and glycosaminoglycan metabolism. Our study demonstrates that the cartilaginous pellet–based system is a valuable tool to study MPS IH dysostosis and to develop new therapeutic approaches for this hard-to-treat aspect of the disease. Finally, our approach may be applied for modeling other genetic skeletal disorders.
Authors
Samantha Donsante, Alice Pievani, Biagio Palmisano, Melissa Finamore, Grazia Fazio, Alessandro Corsi, Andrea Biondi, Shunji Tomatsu, Rocco Piazza, Marta Serafini, Mara Riminucci
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