The mitochondria regulation of stem cell aging

Mitophagy induction improves salivary gland stem/progenitor cell function by reducing senescence after irradiation

BACKGROUND AND PURPOSE

Patients undergoing radiotherapy for head and neck cancer often experience a decline in their quality of life due to the co-irradiation of salivary glands. Radiation-induced cellular senescence is a key factor contributing to salivary gland dysfunction. Interestingly, mitochondrial dysfunction and cellular senescence have been reported to be strongly interconnected and thus implicated in several aging-related diseases. This study aims to investigate the role of mitochondrial dysfunction in senescence induction in salivary gland stem/progenitor cells after irradiation.

MATERIALS AND METHODS

A dose of 7 Gy photons was used to irradiate mouse salivary gland organoids. Senescent markers and mitochondrial function were assessed using rt-qPCR, western blot analysis, SA-β-Gal staining and flow cytometry analysis. Mitochondrial dynamics-related proteins were detected by western blot analysis while Mdivi-1 and MFI8 were used to modulate the mitochondrial fission process. To induce mitophagy, organoids were treated with Urolithin A and PMI and subsequently stem/progenitor cell self-renewal capacity was assessed as organoid forming efficiency.

RESULTS

Irradiation led to increased senescence and accumulation of dysfunctional mitochondria. This was accompanied by a strong downregulation of mitochondrial fission-related proteins and mitophagy-related genes. After irradiation, treatment with the mitophagy inducer Urolithin A attenuated the senescent phenotype and improved organoid growth and stem/progenitor cell self-renewal capacity.

CONCLUSION

This study shows the important interplay between senescence and mitochondrial dysfunction after irradiation. Importantly, activation of mitophagy improved salivary gland stem/progenitor cell function thereby providing a novel therapeutic strategy to restore the regenerative capacity of salivary glands following irradiation.

Mitochondrial permeability transition regulator, cyclophilin D, is transcriptionally activated by C/EBP during adipogenesis

Age-related bone loss is associated with decreased bone formation, increased bone resorption, and accumulation of bone marrow fat. During aging, differentiation potential of bone marrow stromal (a.k.a. mesenchymal stem) cells (BMSCs) is shifted toward an adipogenic lineage and away from an osteogenic lineage. In aged bone tissue, we previously observed pathological opening of the mitochondrial permeability transition pore (MPTP) which leads to mitochondrial dysfunction, oxidative phosphorylation uncoupling, and cell death. Cyclophilin D (CypD) is a mitochondrial protein that facilitates opening of the MPTP. We found earlier that CypD is downregulated during osteogenesis of BMSCs leading to lower MPTP activity and, thus, protecting mitochondria from dysfunction. However, during adipogenesis, a fate alternative to osteogenesis, the regulation of mitochondrial function and CypD expression is still unclear. In this study, we observed that BMSCs have increased CypD expression and MPTP activity, activated glycolysis, and fragmented mitochondrial network during adipogenesis. Adipogenic C/EBPα acts as a transcriptional activator of expression of the CypD gene, Ppif, during this process. Inflammation-associated transcription factor NF-κB shows a synergistic effect with C/EBPα inducing Ppif expression. Overall, we demonstrated changes in mitochondrial morphology and function during adipogenesis. We also identified C/EBPα as a transcriptional activator of CypD. The synergistic activation of CypD by C/EBPα and the NF-κB p65 subunit during this process suggests a potential link between adipogenic signaling, inflammation, and MPTP gain-of-function, thus altering BMSC fate during aging.

Mitochondria pleiotropism in stem cell senescence: Mechanisms and therapeutic approaches

Aging is a complex biological process characterized by a progressive decline in cellular and tissue function, ultimately leading to organismal aging. Stem cells, with their regenerative potential, play a crucial role in maintaining tissue homeostasis and repair throughout an organism's lifespan. Mitochondria, the powerhouses of the cell, have emerged as key players in the aging process, impacting stem cell function and contributing to age-related tissue dysfunction. Here are discuss the mechanisms through which mitochondria influence stem cell fate decisions, including energy production, metabolic regulation, ROS signalling, and epigenetic modifications. Therefore, this review highlights the role of mitochondria in driving stem cell senescence and the subsequent impact on tissue function, leading to overall organismal aging and age-related diseases. Finally, we explore potential anti-aging therapies targeting mitochondrial health and discuss their implications for promoting healthy aging. This comprehensive review sheds light on the critical interplay between mitochondrial function, stem cell senescence, and organismal aging, offering insights into potential strategies for attenuating age-related decline and promoting healthy longevity.

Ohwia caudata aqueous extract attenuates doxorubicin-induced mitochondrial dysfunction in Wharton's jelly-derived mesenchymal stem cells

Mitochondrial dysfunction has been linked to many diseases, including organ degeneration and cancer. Wharton's jelly-derived mesenchymal stem cells provide a valuable source for stem cell-based therapy and represent an emerging therapeutic approach for tissue regeneration. This study focused on screening the senomorphic properties of Ohwia caudata aqueous extract as an emerging strategy for preventing or treating mitochondrial dysfunction in stem cells. Wharton's jelly-derived mesenchymal stem cells were incubated with 0.1 μM doxorubicin, for 24 h to induce mitochondrial dysfunction. Next, the cells were treated with a series concentration of Ohwia caudata aqueous extract (25, 50, 100, and 200 μg/mL) for another 24 h. In addition, an untreated control group and a doxorubicin-induced mitochondrial dysfunction positive control group were maintained under the same conditions. Our data showed that Ohwia caudata aqueous extract markedly suppressed doxorubicin-induced mitochondrial dysfunction by increasing Tid1 and Tom20 expression, decreased reactive oxygen species production, and maintained mitochondrial membrane potential to promote mitochondrial stability. Ohwia caudata aqueous extract retained the stemness of Wharton's jelly-derived mesenchymal stem cells and reduced the apoptotic rate. These results indicate that Ohwia caudata aqueous extract protects Wharton's jelly-derived mesenchymal stem cells against doxorubicin-induced mitochondrial dysfunction and can potentially prevent mitochondrial dysfunction in other cells. This study provides new directions for the medical application of Ohwia caudata.

The role of metabolism in cellular quiescence

Cellular quiescence is a dormant, non-dividing cell state characterized by significant shifts in physiology and metabolism. Quiescence plays essential roles in a wide variety of biological processes, ranging from microbial sporulation to human reproduction and wound repair. Moreover, when the regulation of quiescence is disrupted, it can drive cancer growth and compromise tissue regeneration after injury. In this Review, we examine the dynamic changes in metabolism that drive and support dormant and transiently quiescent cells, including spores, oocytes and adult stem cells. We begin by defining quiescent cells and discussing their roles in key biological processes. We then examine metabolic factors that influence cellular quiescence in both healthy and disease contexts, and how these could be leveraged in the treatment of cancer.

Mitochondria as biological targets for stem cell and organismal senescence

Organismal aging is impacted by the deterioration of tissue turnover mechanisms due, in part, to the decline in stem cell function. This decline can be related to mitochondrial dysfunction and underlying energetic defects that, in concert, help drive biological aging. Thus, mitochondria have been described as a potential interventional target to hinder the loss of stem cell robustness, and subsequently, decrease tissue turnover decline and age-associated pathologies. In this review, we focused our analysis on the most recent literature on mitochondria and stem cell aging and discuss the potential benefits of targeting mitochondria in preventing stem cell dysfunction and thus influencing aging.

Cellular senescence, rejuvenation and potential immortality

Ageing, death, and potential immortality lie at the heart of biology, but two seemingly incompatible paradigms coexist in different research communities and have done since the nineteenth century. The universal senescence paradigm sees senescence as inevitable in all cells. Damage accumulates. The potential immortality paradigm sees some cells as potentially immortal, especially unicellular organisms, germ cells and cancerous cells. Recent research with animal cells, yeasts and bacteria show that damaged cell constituents do in fact build up, but can be diluted by growth and cell division, especially by asymmetric cell division. By contrast, mammalian embryonic stem cells and many cancerous and 'immortalized' cell lines divide symmetrically, and yet replicate indefinitely. How do they acquire their potential immortality? I suggest they are rejuvenated by excreting damaged cell constituents in extracellular vesicles. If so, our understanding of cellular senescence, rejuvenation and potential immortality could be brought together in a new synthesis, which I call the cellular rejuvenation hypothesis: damaged cell constituents build up in all cells, but cells can be rejuvenated either by growth and cell division or, in 'immortal' cell lines, by excreting damaged cell constituents. In electronic supplementary material, appendix, I outline nine ways in which this hypothesis could be tested.

Coenzyme Q homeostasis in aging: Response to non-genetic interventions

Coenzyme Q (CoQ) is a key component for many essential metabolic and antioxidant activities in cells in mitochondria and cell membranes. Mitochondrial dysfunction is one of the hallmarks of aging and age-related diseases. Deprivation of CoQ during aging can be the cause or the consequence of this mitochondrial dysfunction. In any case, it seems clear that aging-associated CoQ deprivation accelerates mitochondrial dysfunction in these diseases. Non-genetic prolongevity interventions, including CoQ dietary supplementation, can increase CoQ levels in mitochondria and cell membranes improving mitochondrial activity and delaying cell and tissue deterioration by oxidative damage. In this review, we discuss the importance of CoQ deprivation in aging and age-related diseases and the effect of prolongevity interventions on CoQ levels and synthesis and CoQ-dependent antioxidant activities.