Single cell RNA seq of hepatic and renal p16 positive cells
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ABSTRACT: We performed the single cell RNA sequencing of mouse normal kidney, normal liver, and NASH-induced liver from p16-tdTomato mice. In order to enrich p16 positive cells, we independently sorted the non-separated cells (including both of p16 positive and negative cells) and p16 positive cells alone through tdTomato intensity by FACS. By obtaining 13,876 single cell transcripts, after the graph-based clustering and marker genes defined cell type classification, we identified the heterogeneity of in vivo p16-positive cells which dispersedly existed in renal cells and non-parenchymal hepatic cells. Differential expressing genes (DEGs) comparisons for each cell type were feasible to study the in vivo p16 dependent transcriptomic pattern change. Finally, we verified several cell type specific senescence-like phenotypes which were previously found on in vitro cellular senescence, and also identified the p16-related subpopulation which might involve in NASH progression and renal damage response.
Project description:The accumulation of senescent cells promotes aging, but a molecular mechanism that senescent cells use to evade immune clearance and accumulate remains to be elucidated. Here, we report that p16-positive senescent cells upregulate the immune checkpoint protein programmed death-ligand 1 (PD-L1) to accumulate in aging and chronic inflammation. p16-mediated inhibition of CDK4/6 promotes PD-L1 stability in senescent cells via the downregulation of ubiquitin-dependent degradation. p16 expression in infiltrating macrophages induces an immunosuppressive environment that can contribute to an increased burden of senescent cells. Treatment with immunostimulatory anti-PD-L1 antibody enhances the cytotoxic T cell activity and leads to the elimination of p16, PD-L1-positive cells. Our study uncovers a molecular mechanism of p16-dependent regulation of PD-L1 protein stability in senescent cells and reveals the potential of PD-L1 as a target for treating senescence-mediated age-associated diseases.
Project description:The accumulation of senescent cells promotes aging, but a molecular mechanism that senescent cells use to evade immune clearance and accumulate remains to be elucidated. Here, we report that p16-positive senescent cells upregulate the immune checkpoint protein programmed death-ligand 1 (PD-L1) to accumulate in aging and chronic inflammation. p16-mediated inhibition of CDK4/6 promotes PD-L1 stability in senescent cells via the downregulation of ubiquitin-dependent degradation. p16 expression in infiltrating macrophages induces an immunosuppressive environment that can contribute to an increased burden of senescent cells. Treatment with immunostimulatory anti-PD-L1 antibody enhances the cytotoxic T cell activity and leads to the elimination of p16, PD-L1-positive cells. Our study uncovers a molecular mechanism of p16-dependent regulation of PD-L1 protein stability in senescent cells and reveals the potential of PD-L1 as a target for treating senescence-mediated age-associated diseases.
Project description:Advancing age is the greatest risk factor for Alzheimer’s Disease (AD), as most AD patients are age 65 and older. However, the mechanistic contribution of aging to AD is unclear. Cellular senescence, one of the major hallmarks of aging, is recently implicated as an aggravator of AD pathogenesis. The critical senescence regulator p16 is increased in neurons of AD patients and mouse models. Eliminating p16-expressing senescent cells attenuates AD pathologies in AD mouse models. However, what p16 does in post-mitotic neurons and how p16 contributes to AD pathogenesis remains unknown. As clinical trials continually fail to improve cognitive decline in AD patients, it is increasingly important to develop a better human cell-based model system to advance our understanding of the impact of aging in AD pathogenesis. Induced pluripotent stem cell (iPSC) technology has revolutionized human disease modeling, enabling differentiation to relevant brain cell types for the study of AD pathogenesis in a human cell-based culture environment. AD iPSC-derived neurons exhibit higher levels of Amyloid beta secretion and tau phosphorylation compared to non-demented control iPSC-derived neurons. Nevertheless, iPSC-derived neurons are “fetal-like” and fail to recapitulate the aging process in AD pathogenesis. Thus, we have developed a robust human iPSC-based neuron model to investigate the contribution of p16 expression to cellular senescence and AD pathogenesis. We found that inducible p16 expression leads to senescence phenotypes in AD as well as non-demented control iPSC-derived neurons. The impact of p16 and induced senescence in neurons on the cellular pathologies of AD is investigated. Our study provides a novel approach to investigate aging-associated cellular changes that potentially influence AD patient-derived differentiated neurons to age and become more permissive to AD pathogenesis in culture.
Project description:p16 and p21 act as tumor suppressors through induction of cellular senescence. However, senescence-independent roles of these CDK inhibitors are not known. To identify the mechanism responsible for the failure of Mo-MDSCs (monocytic myeloid-derived suppressor cells) infiltration into tumor allografts in p16/p21-double knockout (DKO) mice, we searched for chemokine receptors that were highly expressed in Mo- but not PMN-MDSCs (polymorphonuclear myeloid-derived suppressor cells) and were downregulated in p16/p21-DKO as compared to WT Mo-MDSCs. Ccr2, Ccr5, and Cx3cr1 were identified by RNA-seq analysis.
Project description:Senescent cells are in a state of permanent cell cycle arrest, which is mediated by the Cyclin Dependent Kinase (CDK)4/6 inhibitor p16. During ageing, p16-expressing (P16pos) cells accumulate in tissues and promote multiple age-related pathologies, including neurodegenerative diseases. We evaluated the accumulation and the phenotype of senescent cells in the aged brain with a transgenic reporter mouse (p16-3MR), which allows for isolation of P16poscells. First, we showed that the number of P16pos cells is significantly increased in old brains. Second, using bulk RNAseq, we demonstrated that P16pos cells express high levels of inflammatory and lysosomal genes. Third, using single-cell RNAseq, we identified P16pos brain cells as being primarily microglia. Interestingly, the transcriptional profile of P16pos microglia cells is distinct from cell type signatures associated with senescence or defined microglia populations. Taken together, our study provides evidence for the accumulation of a novel P16pos microglia population in the aging brain, which could result in loss of tissue homeostasis and contribute to brain dysfunction.
Project description:PTPRD is a tumor suppressor of glioma that is frequently co-deleted with CDKN2A/p16. We show that Ptprd and p16 cooperate to promote gliomagenesis in the RCAS PDGFB / Nestin tv-A glioma mouse model. We found unique gene expression changes within tumor cells of Ptprd+/-p16-/- vs. Ptprd+/+p16-/- and Ptprd-/-p16-/- tumor cells. Neonatal mice were injected with RCAS PDGFB GFP. At symptoms, or at 12 weeks post injection, GFP+DAPI- tumor cells were sorted for RNA extraction and hybridization on Affymetrix microarrays. The mouse strain used was a mixed background of C57/BL6 and FVB/N. Ptprd mice were from Uetani et al. 2000 and p16/Nestin-tvA mice were from Tchouganouva et al. 2007.
Project description:PTPRD is a tumor suppressor of glioma that is frequently co-deleted with CDKN2A/p16. We show that Ptprd and p16 cooperate to promote gliomagenesis in the RCAS PDGFB / Nestin tv-A glioma mouse model. We found unique gene expression changes within tumor cells of Ptprd+/-p16-/- vs. Ptprd+/+p16-/- and Ptprd-/-p16-/- tumor cells.
Project description:Head and neck squamous cell carcinomas are heterogeneous neoplasms that show clinical and biological differences in association with the human papillomavirus (HPV). To provide adequate therapeutic strategies, biological and clinical characterization is essential to stratify patients based on prognostic and predictive factors. Reports on HNSCC are scarce in Mexico, thus in the present study, we analyze 414 cases of HNSCC, including those of the oropharynx (OPSCC), larynx (LASCC), and oral cavity (OCSCC). We determined the presence of HPV and p16 expression. Global expression profiles were analyzed with Affymetrix HTA 2.0 microarray in 25 selected cases HPV+/p16+ versus HPV-/p16-. In our study we analyze 25 samples derived from HNSCC patients. 18 samples were HPV-/p16- and 7 HPV+/p16+. We compared the HPV-/p16- versus the HPV+/p16+ and identified differentially expressed RNAs with a fold change greater than 1.5 or less than -1.5. These data were used to obtain 98 genes that are differentially expressed in absence of HPV. The present study offers information regarding clinical and molecular characteristics of HNSCC, both associated and unassociated with HPV, in Mexican patients.
Project description:Background: Senescent hepatocytes accumulate in parallel with fibrosis progression during NASH. The mechanisms that enable progressive expansion of nonreplicating cell populations and the significance of that process in determining NASH outcomes are unclear. Many types of senescing cells upregulate the THBD-PAR-1 signaling axis to remain viable. Vorapaxar, an FDA-approved PAR-1 inhibitor, blocks the activity of that pathway. We used vorapaxar to determine if and how THBD-PAR1 signaling promotes fibrosis progression in NASH. Methods: We evaluated the THBD-PAR1 pathway in liver biopsies from NAFLD patient cohorts with a spectrum of liver fibrosis. Chow fed mice were treated with viral vectors to over-express p16 specifically in hepatocytes and induce replicative senescence. Effects on the THBD-PAR-1 axis and regenerative capacity were assessed; the transcriptome of p16 over-expressing hepatocytes was characterized and we examined how conditioned medium from senescent but viable (dubbed ‘undead’) hepatocytes reprograms hepatic stellate cells. A genetically obese mouse model of NASH with little liver fibrosis, and a diet-induced mouse model of NASH with advanced fibrosis were treated with vorapaxar to determine effects on hepatocyte senescence and liver damage. Results: Inducing senescence up-regulates the THBD-PAR1 signaling axis in hepatocytes and induces their expression of fibrogenic factors, including hedgehog ligands. Hepatocyte THBD-PAR1 signaling increases in NAFLD and supports sustained hepatocyte senescence that limits effective liver regeneration and promotes maladaptive repair. Inhibiting PAR-1 signaling with vorapaxar interrupts this process, reduces the burden of ‘undead’ senescent cells, and safely improves NASH and fibrosis despite ongoing lipotoxic stress Conclusion: The THBD-PAR1 signaling axis is a novel therapeutic target for NASH because blocking this pathway prevents accumulation of senescing but viable hepatocytes that generate factors that promote maladaptive liver repair.