Project description:Finite replicative potential is a defining feature of non-transformed somatic cells, first established by Leonard Hayflick in vitro using WI-38 human lung fibroblasts. Once proliferative capacity is exhausted due to telomere shortening, cells enter into a state called replicative senescence, which can be avoided through ectopic expression of telomerase reverse transcriptase (hTERT). As WI-38 cells approach replicative arrest, molecular pathways linked to mechanotransduction are induced, including YAP signaling, but the potential interplay between replicative lifespan and the mechanical environment of the cell remains unexplored. Here, we investigate the influence of mechanosensation on the trajectory towards replicative arrest taken by WI-38 cells by growing cells on substrates of varying stiffnesses. Matrix softening slowed proliferation, altered cellular phenotypes, and shortened proliferative lifespan while hTERT expression abrogated or reduced these responses. Our analyses of bulk and single-cell RNA-sequencing and ATAC-sequencing revealed the emergence of a unique G1 transcriptional state on soft substrates, characterized by an AP-1 transcription factor program, which failed to manifest with hTERT expression. Together, these findings reveal how the mechanical environment alters WI-38 cell proliferative lifespan and dictates unique paths towards growth arrest.
Project description:Finite replicative potential is a defining feature of non-transformed somatic cells, first established by Leonard Hayflick in vitro using WI-38 human lung fibroblasts. Once proliferative capacity is exhausted due to telomere shortening, cells enter into a state called replicative senescence, which can be avoided through ectopic expression of telomerase reverse transcriptase (hTERT). As WI-38 cells approach replicative arrest, molecular pathways linked to mechanotransduction are induced, including YAP signaling, but the potential interplay between replicative lifespan and the mechanical environment of the cell remains unexplored. Here, we investigate the influence of mechanosensation on the trajectory towards replicative arrest taken by WI-38 cells by growing cells on substrates of varying stiffnesses. Matrix softening slowed proliferation, altered cellular phenotypes, and shortened proliferative lifespan while hTERT expression abrogated or reduced these responses. Our analyses of bulk and single-cell RNA-sequencing and ATAC-sequencing revealed the emergence of a unique G1 transcriptional state on soft substrates, characterized by an AP-1 transcription factor program, which failed to manifest with hTERT expression. Together, these findings reveal how the mechanical environment alters WI-38 cell proliferative lifespan and dictates unique paths towards growth arrest.
Project description:Finite replicative potential is a defining feature of non-transformed somatic cells, first established by Leonard Hayflick in vitro using WI-38 human lung fibroblasts. Once proliferative capacity is exhausted due to telomere shortening, cells enter into a state called replicative senescence, which can be avoided through ectopic expression of telomerase reverse transcriptase (hTERT). As WI-38 cells approach replicative arrest, molecular pathways linked to mechanotransduction are induced, including YAP signaling, but the potential interplay between replicative lifespan and the mechanical environment of the cell remains unexplored. Here, we investigate the influence of mechanosensation on the trajectory towards replicative arrest taken by WI-38 cells by growing cells on substrates of varying stiffnesses. Matrix softening slowed proliferation, altered cellular phenotypes, and shortened proliferative lifespan while hTERT expression abrogated or reduced these responses. Our analyses of bulk and single-cell RNA-sequencing and ATAC-sequencing revealed the emergence of a unique G1 transcriptional state on soft substrates, characterized by an AP-1 transcription factor program, which failed to manifest with hTERT expression. Together, these findings reveal how the mechanical environment alters WI-38 cell proliferative lifespan and dictates unique paths towards growth arrest.
Project description:Finite replicative potential is a defining feature of non-transformed somatic cells, first established by Leonard Hayflick in vitro using WI-38 human lung fibroblasts. Once proliferative capacity is exhausted due to telomere shortening, cells enter into a state called replicative senescence, which can be avoided through ectopic expression of telomerase reverse transcriptase (hTERT). As WI-38 cells approach replicative arrest, molecular pathways linked to mechanotransduction are induced, including YAP signaling, but the potential interplay between replicative lifespan and the mechanical environment of the cell remains unexplored. Here, we investigate the influence of mechanosensation on the trajectory towards replicative arrest taken by WI-38 cells by growing cells on substrates of varying stiffnesses. Matrix softening slowed proliferation, altered cellular phenotypes, and shortened proliferative lifespan while hTERT expression abrogated or reduced these responses. Our analyses of bulk and single-cell RNA-sequencing and ATAC-sequencing revealed the emergence of a unique G1 transcriptional state on soft substrates, characterized by an AP-1 transcription factor program, which failed to manifest with hTERT expression. Together, these findings reveal how the mechanical environment alters WI-38 cell proliferative lifespan and dictates unique paths towards growth arrest.
Project description:Treating recurrent GBM is a clinical challenge due to its highly resistant and aggressive nature. In order to develop new therapeutic targets for recurrent GBM a better understanding of its molecular landscape is necessary. Here we used a cellular model, developed in our lab which generates paired primary and recurrent samples from GBM cell lines and primary patient samples hence allowing us to compare the molecular differences between the two populations. Total RNA seq analysis of parent and recurrent population of two cell lines and one patient sample revealed a significant upregulation of Extracellular matrix interaction in recurrent population. Since matrix stiffness plays a pivotal role in cell-ECM interaction and downstream signaling, we developed a system that mimicked the brain like substrate stiffness by using collagen coated polyacrylamide-based substrate whose stiffness can be modified from normal brain (0.5kPa) to tumorigenic (10kPa). Using these substrates, we were able to capture the morphological and physiological differences between parent and recurrent GBM which were not evident on plastic surfaces (~1 GPa). On 0.5kPa, unlike circular parent cells, recurrent GBM cells showed two morphologies (circular and elongated). The recurrent cells growing on 0.5kPa also showed higher proliferation, invasion, migration and in-vivo tumorigenicity in orthotropic GBM mouse model, compared to parent cells. Furthermore, recurrent cells exhibited elevated velocity irrespective of substrate stiffness, which indicated that recurrent cells may possess inherent differential mechanosignalling ability which was reflected by higher expression of ECM proteins like Collagen IVA, MMP2 and MMP9. Moreover, mice brain injected with recurrent cells grown on 0.5kPa substrate showed higher Young’s modulus values suggesting that recurrent cells conditioned on 0.5kPa make the surrounding ECM stiffer. Importantly, inhibition of EGFR signaling, that is amplified with tissue stiffening in GBM resulted in decreased invasion, migration and proliferation in 0.5kPa recurrent cells, but interestingly survival remained unaffected, highlighting the importance of mimicking the physiological stiffness of the brain mimicking clinical scenario. Total RNA seq analysis of parent and recurrent cells grown on plastic and 0.5kPa substrate identified PLEKHA7 as significantly upregulated gene specifically in 0.5kPa recurrent sample. Higher protein expression of PLEKHA7 in recurrent GBM as compared to primary GBM was validated in patient biopsies. Accordingly, PLEKHA7 knockdown reduced invasion and survival of recurrent GBM cells. Together, these data provides a model system that captures the differential mechanosensing signals of primary and recurrent GBM cells and identifies a novel potential target specific for recurrent GBM.
Project description:In vitro cultures of primary cardiac fibroblasts (CFs), the major extracellular matrix (ECM)-producing cells of the heart, are used to determine molecular mechanisms of cardiac fibrosis. However, the supraphysiologic stiffness of tissue culture polystyrene (TCPS) automatically triggers the conversion of CFs into an activated myofibroblast-like state, and serial passage of the cells results in the induction of replicative senescence. These dramatic phenotypic switches confound interpretation of experimental data obtained with cultured CFs. In an attempt to circumvent TCPS-induced activation and senescence of CFs, we utilized poly (ethylene glycol) (PEG) hydrogels as cell culture platforms with low and high stiffness formulations to mimic healthy and fibrotic cardiac ECM, respectively. As hypothesized, low hydrogel stiffness converted activated CFs into a quiescent state with reduced abundance of a-smooth muscle actin (a-SMA)-containing stress fibers. Unexpectedly, lower substrate stiffness concomitantly augmented CF senescence, marked by elevated senescence-associated b-galactosidase (SA-b-Gal) activity and increased expression of p16 and p21, which are cyclin-dependent kinase (CDK) inhibitors and markers of senescence. Using dynamically stiffening hydrogels with phototunable crosslinking capabilities, we demonstrate that substrate-induced CF senescence is partially reversible. RNA-sequencing analysis revealed widespread transcriptional reprogramming of CFs cultured on low stiffness hydrogels, with a dramatic reduction in the expression of profibrotic genes encoding ECM proteins, and an attendant increase in expression of NF-kB-responsive inflammatory genes that typify the senescence-associated secretory phenotype (SASP). Our findings further demonstrate that alterations in matrix stiffness profoundly impact CF cell state transitions, and suggest mechanisms by which CFs change phenotype in vivo depending on the stiffness of the myocardial microenvironment to which they are exposed.
Project description:Mechanical feedback from the tumor microenvironment regulates an array of processes underlying cancer biology. Routine culture and adaptation of cancer cell lines to unnaturally rigid plastic or glass substrates leads to profound changes in their growth, metastatic potential and potentially chemotherapeutic response. Microarray studies were conducted to probe the impact of substratum stiffness on the regulation of genetic pathways in mammary tumor cells, and immortalized cancer cell lines, that modulate sensitivity and resistance towards clinically-approved chemotherapeutics We used microarrays to detail the global programme of gene expression underlying cellular response to substrates of different mechanical stiffness.