Project description:Targeting senescent cells for therapeutic purposes is gaining momentum across various organ systems. However, concerns about potential off-target effects have been raised. Previous studies have shown that removing senescent cells expressing high levels of p16 (p16high) can hinder processes like wound healing. Here, we identify a distinct senescent cell population during dermal wound healing characterized by high expression level of p21 (p21high) using the p21-Cre mouse model. Using a standard cutaneous injury model, we find that eliminating p21high cells can expedite wound closure, in contrast to the effects of removing p16high cells. Through Xenium, a single cell spatial imaging platform, we show that p21high cells are distinct from p16high cells, with p21high cells mainly comprising fibroblasts, immune cells, keratinocytes, and endothelial cells with a pro-inflammatory profile. Moreover, inhibition of NF-kB signaling specifically from p21high cells partially contributes to the accelerated wound healing rates. These findings highlight the heterogeneity of senescent cells during wound healing responses within the skin and likely in other conditions.
Project description:Targeting senescent cells for therapeutic purposes is gaining momentum across various organ systems. However, concerns about potential off-target effects have been raised. Previous studies have shown that removing senescent cells expressing high levels of p16 (p16high) can hinder processes like wound healing. Here, we identify a distinct senescent cell population during dermal wound healing characterized by high expression level of p21 (p21high) using the p21-Cre mouse model. Using a standard cutaneous injury model, we find that eliminating p21high cells can expedite wound closure, in contrast to the effects of removing p16high cells. Through Xenium, a single cell spatial imaging platform, we show that p21high cells are distinct from p16high cells, with p21high cells mainly comprising fibroblasts, immune cells, keratinocytes, and endothelial cells with a pro-inflammatory profile. Moreover, inhibition of NF-kB signaling specifically from p21high cells partially contributes to the accelerated wound healing rates. These findings highlight the heterogeneity of senescent cells during wound healing responses within the skin and likely in other conditions.
Project description:Cells expressing features of cellular senescence, including upregulation of p21 and p16, appear transiently following tissue injury, yet the properties of these cells or how they contrast with age-induced senescent cells remains unclear. Using skeletal fracture as a model of acute injury, we identified rapidly-appearing senescent-like cells, marked by p21 expression, that negatively affected fracture healing. p21+ callus cells, which consisted predominantly of neutrophils and osteochondroprogenitors, existed as transient cells specific to injury and expressed high levels of senescence-associated factors known to impair bone formation and induce paracrine senescence. Targeted genetic clearance of p21+ cells suppressed senescence-associated signatures within the fracture callus and accelerated fracture healing. By contrast, p21+ cell clearance did not alter bone loss due to aging; conversely, p16+ cell clearance, known to alleviate skeletal aging, did not affect fracture healing. Together, our findings establish contextual roles of senescent/senescent-like cells that may be leveraged for therapeutic opportunities.
Project description:Cellular senescence is a permanent state of cell cycle arrest that protects the organism from tumorigenesis and regulates tissue integrity upon damage and during tissue remodeling. However, accumulation of senescent cells in tissues during aging contributes to age-related pathologies. A deeper understanding of the mechanisms regulating the viability of senescent cells is therefore required. Here we show that the CDK inhibitor p21 (CDKN1A) maintains the viability of DNA damage-induced senescent cells.
Project description:Cellular senescence is a stress response that imposes stable cell-cycle arrest in damaged cells, preventing their propagation in tissues. However, long-term presence of senescent cells might promote tissue degeneration and malignant transformation via secreted pro-inflammatory and matrix-remodeling factors. These factors lead to immune-cell recruitment and senescent-cell clearance. Senescent cells accumulate in tissues in advanced age. The extent of immune-system involvement in regulating age-related accumulation of senescent cells, and its consequences, are unknown. Here we show that mice with impaired cell cytotoxicity exhibit both higher senescent-cell tissue burden and chronic inflammation. They suffer from multiple age-related disorders and significantly lower survival. Strikingly, pharmacological elimination of senescent-cells by ABT-737 partially alleviates accelerated aging phenotype in these mice. In progeroid mice, impaired cell cytotoxicity further promotes senescent-cell accumulation and shortens lifespan. ABT-737 administration during the second half of life of these progeroid mice abrogates senescence signature and increases median survival. Our findings shed new light on mechanisms governing senescent-cell presence in aging, and could motivate new strategies for regenerative medicine.
Project description:Cellular senescence is characterized by an irreversible cell cycle arrest and a pro-inflammatory senescence-associated secretory phenotype (SASP), which is a major contributor to aging and age-related diseases. Clearance of senescent cells has been shown to improve brain function in mouse models of neurodegenerative diseases. However, it is still unknown whether senescent cell clearance alleviates cognitive dysfunction during the aging process. To investigate this, we first conducted single-nuclei and single-cell RNA-seq in the hippocampus from young and aged mice. We observed an age-dependent increase in p16Ink4a senescent cells, which was more pronounced in microglia and oligodendrocyte progenitor cells and characterized by a SASP. We then aged INK-ATTAC mice, in which p16Ink4a-positive senescent cells can be genetically eliminated upon treatment with the drug AP20187 and treated them either with AP20187 or with the senolytic cocktail Dasatinib and Quercetin. We observed that both strategies resulted in a decrease in p16Ink4a exclusively in the microglial population, resulting in reduced microglial activation and reduced expression of SASP factors. Importantly, both approaches significantly improved cognitive function in aged mice. Our data provide proof-of-concept for senolytic interventions’ being a potential therapeutic avenue for alleviating age-associated cognitive impairment.
Project description:Defective fibroblast migration cause delayed wound healing (WH) and chronic skin lesions. Autologous micrograft (AMG) therapies have recently emerged as a new effective treatment able to improve wound healing capacity. However, the molecular mechanisms connecting their beneficial outcomes with the wound healing process are still unrevealed. Here, we show that AMG modulates primary fibroblast migration and accelerates skin re-epithelialization without affecting cell proliferation. We demonstrate that AMG is enriched in a pool of WH-associated growth factors that may provide the initiation signal for faster endogenous wound healing response. This, in turn leads to increased cell migration rate by elevating activity of ERK and subsequent activation of matrix metalloproteinase expression and their extracellular enzymatic activity. Moreover, AMG-treated wounds showed increased granulation tissue formation and organized collagen content. Overall, we shed light on AMG molecular mechanism supporting its potential to trigger highly improved wound healing process.
Project description:Poorly healing diabetic wounds are characterized by diminished collagen production and impaired angiogenesis. HoxD3, a homeobox transcription factor that promotes angiogenesis and collagen synthesis, is up-regulated during normal wound repair whereas its expression is diminished in poorly healing wounds of the genetically diabetic (db/db) mouse. To determine whether restoring expression of HoxD3 would accelerate diabetic wound healing, we devised a novel method of gene transfer, which incorporates HoxD3 plasmid DNA into a methylcellulose film that is placed on wounds created on db/db mice. The HoxD3 transgene was expressed in endothelial cells, fibroblasts, and keratinocytes of the wounds for up to 10 days. More importantly, a single application of HoxD3 to db/db mice resulted in a statistically significant acceleration of wound closure compared to control-treated wounds. Furthermore, we also observed that the HoxD3-mediated improvement in diabetic wound repair was accompanied by increases in mRNA expression of the HoxD3 target genes, Col1A1 and beta 3-integrin leading to enhanced angiogenesis and collagen deposition in the wounds. Although HoxD3-treated wounds also show improved re-epithelialization as compared to control db/db wounds, this effect was not due to direct stimulation of keratinocyte migration by HoxD3. Finally, we show that despite the dramatic increase in collagen synthesis and deposition in HoxD3-treated wounds, these wounds showed normal remodeling and we found no evidence of abnormal wound healing. These results indicate that HoxD3 may provide a means to directly improve collagen deposition, angiogenesis and closure in poorly healing diabetic wounds.