The remarkable regeneration capability of skeletal muscle depends on coordinated proliferation and differentiation of satellite cells. The self-renewal of satellite cells is critical for long-term maintenance of muscle regeneration potential. Hypoxia profoundly affects the proliferation, differentiation, and self-renewal of cultured myoblasts. However, the physiological relevance of hypoxia and hypoxia signaling in satellite cells in vivo remains largely unknown. Here, we report that satellite cells are in an intrinsic hypoxic state in vivo and express hypoxia-inducible factor 2A (HIF2A). HIF2A promotes the stemness and long-term homeostatic maintenance of satellite cells by maintaining the quiescence, increasing the self-renewal and blocking the myogenic differentiation of satellite cells. HIF2A stabilization in satellite cells cultured under normoxia augmented their engraftment potential in regenerative muscle. Reversely, HIF2A ablation led to the depletion of satellite cells and the consequent regenerative failure in the long-term. In contrast, transient pharmacological inhibition of HIF2A accelerated muscle regeneration by increasing satellite cell proliferation and differentiation. Mechanistically, HIF2A induces the quiescence/self-renewal of satellite cells by binding the promoter of Spry1 gene and activating Spry1 expression. These findings suggest that HIF2A is a pivotal mediator of hypoxia signaling in satellite cells and may be therapeutically targeted to improve muscle regeneration.
Liwei Xie, Amelia Yin, Anna S. Nichenko, Aaron M. Beedle, Jarrod A. Call, Hang Yin
Spinocerebellar ataxia type 1 (SCA1) is an adult-onset neurodegenerative disease caused by a polyglutamine expansion in the protein ATXN1, which is involved in transcriptional regulation. Although symptoms appear relatively late in life, primarily from cerebellar dysfunction, pathogenesis begins early, with brain-wide transcriptional changes detectable as early as a week after birth in SCA1 knock-in mice. Given the importance of this postnatal period for cerebellar development, we asked whether this region might be developmentally altered by mutant ATXN1. We found that expanded ATXN1 stimulates the proliferation of postnatal cerebellar stem cells in SCA1 mice. These hyper-proliferating stem cells tended to differentiate into GABAergic inhibitory interneurons rather than astrocytes; this significantly increased the GABAergic inhibitory interneuron synaptic connections, disrupting cerebellar Purkinje cell function in a non-cell autonomous manner. We confirmed the increased basket cell-Purkinje cell connectivity in human SCA1 patients. Mutant ATXN1 thus alters the neural circuitry of the developing cerebellum, setting the stage for the later vulnerability of Purkinje cells to SCA1. We propose that other late-onset degenerative diseases may also be rooted in subtle developmental derailments.
Chandrakanth Reddy Edamakanti, Jeehaeh Do, Alessandro Didonna, Marco Martina, Puneet Opal
Dynamic interaction with the immune system profoundly regulates tumor cell dormancy. However, it is unclear how immunological cues trigger cancer cell–intrinsic signaling pathways for entering into dormancy. Here, we show that IFN-β treatment induced tumor-repopulating cells (TRC) to enter dormancy through an indolamine 2,3-dioxygenase/kynurenine/aryl hydrocarbon receptor/p27–dependent (IDO/Kyn/AhR/p27-dependent) pathway. Strategies to block this metabolic circuitry did not relieve dormancy, but led to apoptosis of dormant TRCs in murine and human melanoma models. Specifically, blocking AhR redirected IFN-β signaling to STAT3 phosphorylation through both tyrosine and serine sites, which subsequently facilitated STAT3 nuclear translocation and subsequent binding to the p53 promoter in the nucleus. Upregulation of p53 in turn disrupted the pentose phosphate pathway, leading to excessive ROS production and dormant TRC death. Additionally, in melanoma patients, high expression of IFN-β correlated with tumor cell dormancy. Identification of this mechanism for controlling TRC dormancy by IFN-β provides deeper insights into cancer-immune interaction and potential new cancer immunotherapeutic modalities.
Yuying Liu, Jiadi Lv, Jinyan Liu, Xiaoyu Liang, Xun Jin, Jing Xie, Le Zhang, Degao Chen, Roland Fiskesund, Ke Tang, Jingwei Ma, Huafeng Zhang, Wenqian Dong, Siqi Mo, Tianzhen Zhang, Feiran Cheng, Yabo Zhou, Qingzhu Jia, Bo Zhu, Yan Kong, Jun Guo, Haizeng Zhang, Zhuo-Wei Hu, Xuetao Cao, F. Xiao-Feng Qin, Bo Huang
Claudins, the integral tight junction (TJ) proteins that regulate paracellular permeability and cell polarity, are frequently dysregulated in cancer; however, their role in neoplastic progression is unclear. Here, we demonstrated that knockout of Cldn18, a claudin family member highly expressed in lung alveolar epithelium, leads to lung enlargement, parenchymal expansion, increased abundance and proliferation of known distal lung progenitors, the alveolar epithelial type II (AT2) cells, activation of Yes-associated protein (YAP), increased organ size, and tumorigenesis in mice. Inhibition of YAP decreased proliferation and colony-forming efficiency (CFE) of Cldn18–/– AT2 cells and prevented increased lung size, while CLDN18 overexpression decreased YAP nuclear localization, cell proliferation, CFE, and YAP transcriptional activity. CLDN18 and YAP interacted and colocalized at cell-cell contacts, while loss of CLDN18 decreased YAP interaction with Hippo kinases p-LATS1/2. Additionally, Cldn18–/– mice had increased propensity to develop lung adenocarcinomas (LuAd) with age, and human LuAd showed stage-dependent reduction of CLDN18.1. These results establish CLDN18 as a regulator of YAP activity that serves to restrict organ size, progenitor cell proliferation, and tumorigenesis, and suggest a mechanism whereby TJ disruption may promote progenitor proliferation to enhance repair following injury.
Beiyun Zhou, Per Flodby, Jiao Luo, Dan R. Castillo, Yixin Liu, Fa-Xing Yu, Alicia McConnell, Bino Varghese, Guanglei Li, Nyam-Osor Chimge, Mitsuhiro Sunohara, Michael N. Koss, Wafaa Elatre, Peter Conti, Janice M. Liebler, Chenchen Yang, Crystal N. Marconett, Ite A. Laird-Offringa, Parviz Minoo, Kunliang Guan, Barry R. Stripp, Edward D. Crandall, Zea Borok
Tuberous sclerosis complex (TSC) is a dominantly inherited disease, caused by hyperactivation of the mTORC1 pathway and characterized by the development of hamartomas and benign tumors, also in the brain. Among the neurological manifestations associated with TSC, the tumor progression of static subependymal nodules (SENs) into subependymal giant cell astrocytomas (SEGAs) is one of the major causes of morbidity and shortened life expectancy. To date, mouse modeling has failed in reproducing these two lesions. Here we report that simultaneous hyperactivation of mTORC1 and Akt pathways by codeletion of Tsc1 and Pten, selectively in postnatal neural stem cells (pNSCs), is required for the formation of bona fide SENs and SEGAs. Notably, both lesions closely recapitulate the pathognomonic morphological and molecular features of the corresponding human abnormalities. The establishment of long-term expanding pNSC lines from mouse SENs and SEGAs made possible the identification of mTORC2 as one of the mediators conferring tumorigenic potential to SEGA pNSCs. Of note, in spite of concurrent Akt hyperactivation in mouse brain lesions, single mTOR inhibition by rapamycin was sufficient to strongly impair mouse SEGA growth. This study provides the first evidence that, concomitant with mTORC1 hyperactivation, sustained activation of Akt and mTORC2 in pNSCs is a mandatory step for the induction of SENs and SEGAs and, at the same time, makes available an unprecedented NSC-based in vivo/in vitro model to be exploited for identifying actionable targets in TSC.
Paola Zordan, Manuela Cominelli, Federica Cascino, Elisa Tratta, Pietro L. Poliani, Rossella Galli
Breast cancer cells with stem cell properties are key contributors to metastatic disease, and there remains a need to better understand and target these cells in human cancers. Here, we identified rare stem-like cells in patients’ tumors characterized by low levels of the proapoptotic molecule p53-upregulated modulator of apoptosis (PUMA) and showed that these cells play a critical role in tumor progression that is independent of clinical subtype. A signaling axis consisting of the integrin αvβ3, Src kinase, and the transcription factor Slug suppresses PUMA in these cells, promoting tumor stemness. We showed that genetic or pharmacological disruption of αvβ3/Src signaling drives PUMA expression, specifically depleting these stem-like tumor cells; increases their sensitivity to apoptosis; and reduces pulmonary metastasis, with no effect on primary tumor growth. Taken together, these findings point to PUMA as a key vulnerability of stem-like cells and suggest that pharmacological upregulation of PUMA via Src inhibition may represent a strategy to selectively target these cells in a wide spectrum of aggressive breast cancers.
Qi Sun, Jacqueline Lesperance, Hiromi Wettersten, Elaine Luterstein, Yoko S. DeRose, Alana Welm, David A. Cheresh, Jay S. Desgrosellier
Endothelial cells (ECs) are components of the hematopoietic microenvironment and regulate hematopoietic stem and progenitor cell (HSPC) homeostasis. Cytokine treatments that cause HSPC trafficking to peripheral blood are associated with an increase in dipeptidylpeptidase 4/CD26 (DPP4/CD26), an enzyme that truncates the neurotransmitter neuropeptide Y (NPY). Here, we show that enzymatically altered NPY signaling in ECs caused reduced VE-cadherin and CD31 expression along EC junctions, resulting in increased vascular permeability and HSPC egress. Moreover, selective NPY2 and NPY5 receptor antagonists restored vascular integrity and limited HSPC mobilization, demonstrating that the enzymatically controlled vascular gateway specifically opens by cleavage of NPY by CD26 signaling via NPY2 and NPY5 receptors. Mice lacking CD26 or NPY exhibited impaired HSPC trafficking that was restored by treatment with truncated NPY. Thus, our results point to ECs as gatekeepers of HSPC trafficking and identify a CD26-mediated NPY axis that has potential as a pharmacologic target to regulate hematopoietic trafficking in homeostatic and stress conditions.
Pratibha Singh, Jonathan Hoggatt, Malgorzata M. Kamocka, Khalid S. Mohammad, Mary R. Saunders, Hongge Li, Jennifer Speth, Nadia Carlesso, Theresa A. Guise, Louis M. Pelus
Age-related changes in the hematopoietic compartment are primarily attributed to cell-intrinsic alterations in hematopoietic stem cells (HSCs); however, the contribution of the aged microenvironment has not been adequately evaluated. Understanding the role of the bone marrow (BM) microenvironment in supporting HSC function may prove to be beneficial in treating age-related functional hematopoietic decline. Here, we determined that aging of endothelial cells (ECs), a critical component of the BM microenvironment, was sufficient to drive hematopoietic aging phenotypes in young HSCs. We used an ex vivo hematopoietic stem and progenitor cell/EC (HSPC/EC) coculture system as well as in vivo EC infusions following myelosuppressive injury in mice to demonstrate that aged ECs impair the repopulating activity of young HSCs and impart a myeloid bias. Conversely, young ECs restored the repopulating capacity of aged HSCs but were unable to reverse the intrinsic myeloid bias. Infusion of young, HSC-supportive BM ECs enhanced hematopoietic recovery following myelosuppressive injury and restored endogenous HSC function in aged mice. Coinfusion of young ECs augmented aged HSC engraftment and enhanced overall survival in lethally irradiated mice by mitigating damage to the BM vascular microenvironment. These data lay the groundwork for the exploration of EC therapies that can serve as adjuvant modalities to enhance HSC engraftment and accelerate hematopoietic recovery in the elderly population following myelosuppressive regimens.
Michael G. Poulos, Pradeep Ramalingam, Michael C. Gutkin, Pierre Llanos, Katherine Gilleran, Sina Y. Rabbany, Jason M. Butler
In multiple sclerosis, the pathological interaction between autoreactive Th cells and mononuclear phagocytes in the CNS drives initiation and maintenance of chronic neuroinflammation. Here, we found that intrathecal transplantation of neural stem/precursor cells (NPCs) in mice with experimental autoimmune encephalomyelitis (EAE) impairs the accumulation of inflammatory monocyte-derived cells (MCs) in the CNS, leading to improved clinical outcome. Secretion of IL-23, IL-1, and TNF-α, the cytokines required for terminal differentiation of Th cells, decreased in the CNS of NPC-treated mice, consequently inhibiting the induction of GM-CSF–producing pathogenic Th cells. In vivo and in vitro transcriptome analyses showed that NPC-secreted factors inhibit MC differentiation and activation, favoring the switch toward an antiinflammatory phenotype. Tgfb2–/– NPCs transplanted into EAE mice were ineffective in impairing MC accumulation within the CNS and failed to drive clinical improvement. Moreover, intrathecal delivery of TGF-β2 during the effector phase of EAE ameliorated disease severity. Taken together, these observations identify TGF-β2 as the crucial mediator of NPC immunomodulation. This study provides evidence that intrathecally transplanted NPCs interfere with the CNS-restricted inflammation of EAE by reprogramming infiltrating MCs into antiinflammatory myeloid cells via secretion of TGF-β2.
Donatella De Feo, Arianna Merlini, Elena Brambilla, Linda Ottoboni, Cecilia Laterza, Ramesh Menon, Sundararajan Srinivasan, Cinthia Farina, Jose Manuel Garcia Manteiga, Erica Butti, Marco Bacigaluppi, Giancarlo Comi, Melanie Greter, Gianvito Martino
Extramedullary hematopoiesis (EMH) is induced during pregnancy to support rapid expansion of maternal blood volume. EMH activation requires hematopoietic stem cell (HSC) proliferation and mobilization, processes that depend upon estrogen receptor α (ERα) in HSCs. Here we show that treating mice with estradiol to model estradiol increases during pregnancy induced HSC proliferation in the bone marrow but not HSC mobilization. Treatment with the alternative ERα ligand 27-hydroxycholesterol (27HC) induced ERα-dependent HSC mobilization and EMH but not HSC division in the bone marrow. During pregnancy, 27HC levels increased in hematopoietic stem/progenitor cells as a result of CYP27A1, a cholesterol hydroxylase. Cyp27a1-deficient mice had significantly reduced 27HC levels, HSC mobilization, and EMH during pregnancy but normal bone marrow hematopoiesis and EMH in response to bleeding or G-CSF treatment. Distinct hematopoietic stresses thus induce EMH through different mechanisms. Two different ERα ligands, estradiol and 27HC, work together to promote EMH during pregnancy, revealing a collaboration of hormonal and metabolic mechanisms as well as a physiological function for 27HC in normal mice.
Hideyuki Oguro, Jeffrey G. McDonald, Zhiyu Zhao, Michihisa Umetani, Philip W. Shaul, Sean J. Morrison