Biology subjects

Kureel, S. K.

Publications and source records attributed to Kureel, S. K..

3 recordsLinked to original sources

bioRxiv2022

Rejuvenating Senescent Cells and Organisms with Only Ultrasound

The presence of an appreciable number of senescent cells causes age-related pathologies as their removal by genetic or pharmacological means, as well as possibly by exercise, improves outcome in animal models. An alternative to depleting such cells would be to rejuvenate them to promote their return to a replicative state. Means to do so have not been explored, but here we report that treatment of non-growing senescent cells with low-frequency ultrasound (LFU) rejuvenates the cells. Notably, we find 15 characteristics of senescent cells that are reversed by LFU, including decreased cell and organelle motility. Mechanistically, LFU causes Ca2+ entry that precedes dramatic increases in autophagy and an inhibition of mTORC1 signaling and the movement of Sirtuin1 from the nucleus to cytoplasm. Also, there is inhibition of SASP secretion, as well as {beta}-galactosidase expression, telomere length is increased, while nuclear 5mc, H3K9me3, {gamma}H2AX, nuclear p53, ROS and mitoROS levels are all restored to normal levels. Repeated LFU treatments enables expansion of primary cells and stem cells beyond normal replicative limits without altering their phenotype. The rejuvenation process is enhanced by co-treatment with rapamycin or Rho kinase inhibition but is inhibited by blocking Sirtuin1 or Piezo1 activity. We further optimized the LFU treatment parameters to increase mouse lifespan and healthspan. These results suggest that mechanically-induced pressure waves alone can reverse senescence and aging effects at the cellular and organismal level, providing a non-pharmacological way to treat the effects of aging. One-Sentence SummaryLow frequency ultrasound is sufficient to rejuvenate senescent cells by activating autophagy in aged mice to improve healthspan.

physiology↗

bioRxiv2021

Substrate stiffness controls the cell cycle of human mesenchymal stem cells via cellular traction

The microenvironment of human mesenchymal stem cells (hMSCs) regulates their self-renewal and differentiation properties. Previously it was shown that hMSCs remained quiescent on soft (0.25 kPa) polyacrylamide (PA) gels but re-entered into cell cycle on a stiff (7.5 kPa) gel. However, how cells behave on intermediate stiffness and what intracellular factors transmit mechanical changes to cell interior thereby regulating cell cycle remained unknown. In this work we demonstrated that PA gels between 1 and 5 kPa act as a mechanical switch in regulating cell cycle of hMSCs. By experiments on cell-cycle exit and re-entry, we found that hMSCs demonstrated a sharp transition from quiescence to proliferation between 1 and 5 kPa. Further studies with ROCK inhibitor Y-27632 revealed that contractile proteins, but not cell spread area, accounts for the sensitivity of hMSCs towards substrate stiffness and hence correlates with their changes in cell cycle. These observations therefore suggest that substrate stiffness regulates hMSC proliferation through contractile forces as generated by cellular contractile proteins in a unique pattern which is distinct from other cell types as studied. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=182 SRC="FIGDIR/small/469207v1_ufig1.gif" ALT="Figure 1"> View larger version (83K): org.highwire.dtl.DTLVardef@a4fff3org.highwire.dtl.DTLVardef@9fb415org.highwire.dtl.DTLVardef@e7d633org.highwire.dtl.DTLVardef@9fba04_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2018

Soft Substrate Maintains Proliferative and Multi-lineage Potential of Human Mesenchymal Stem Cells on Long Term Expansion

Human mesenchymal stem cells (hMSCs), when cultured on tissue culture plate (TCP) for in vitro expansion, they spontaneously lose their proliferative capacity and multi-lineage differentiation potential. They also lose their distinct spindle morphology and become large and flat. After a certain number of population doubling, they enter into permanent cell cycle arrest, called senescence. This is a major roadblock for clinical use of hMSCs which demands large number of cells. A cell culture system is needed which can maintain the stemness of hMSCs over long term passages yet simple to use. In this study, we explore the role of substrate rigidity in maintaining stemness. hMSCs were serially passaged on TCP and 5 kPa poly-acrylamide gel for 20 population doubling. It was found that while on TCP, cell growth reached a plateau at cumulative population doubling (CPD) = 12.5, on 5 kPa gel, they continue to proliferate linearly till we monitored (CPD = 20). We also found that while on TCP, late passage MSCs lost their adipogenic potential, the same was maintained on soft gel. Cell surface markers related to MSCs were also unaltered. We demonstrated that this maintenance of stemness was correlated with delay in onset of senescence, which was confirmed by {beta}-gal assay and by differential expression of vimentin, Lamin A and Lamin B. As preparation of poly-acrylamide gel is a simple, well established, and well standardized protocol, we believe that this system of cell expansion will be useful in therapeutic and research applications of hMSCs.\n\nOne Sentence SummaryhMSCs retain their stemness when expanded in vitro on soft polyacrylamide gel coated with collagen by delaying senescence.\n\nSignificance StatementFor clinical applications, mesenchymal stem cells (MSCs) are required in large numbers. As MSCs are available only in scarcity in vivo, to fulfill the need, extensive in vitro expansion is unavoidable. However, on expansion, they lose their replicative and multi-lineage differentiation potential and become senescent. A culture system that can maintain MSC stemness on long-term expansion, without compromising the stemness, is need of the hour. In this paper, we identified polyacrylamide (PAA) hydrogel of optimum stiffness that can be used to maintain stemness of MSCs during in vitro long term culture. Large quantity of MSCs thus grown can be used in regenerative medicine, cell therapy, and in treatment of inflammatory diseases.

bioengineering↗