Biology subjects

Kondaiah, P.

Publications and source records attributed to Kondaiah, P..

6 recordsLinked to original sources

bioRxiv2025

Stromal LOX/FAK/beta catenin pathway locks mammary fibroblasts into a tumor-promoting myCAF state

BackgroundCancer-associated fibroblasts (CAFs) sustain tumor progression, yet the soluble cues that maintain their myofibroblast (myCAF) state are poorly defined. Transforming growth factor beta (TGF-{beta}) is a canonical CAF activator. This study aims to identify TGF-{beta}-induced secreted mediators that reinforce the myCAF phenotype in breast cancer and map the downstream signaling cascade. Methods and ResultsSecretome profiling of primary patient-derived myCAFs and human mammary fibroblasts (HMF3s) engineered to over-express TGF-{beta}1 revealed 20 extracellular-matrix remodelers shared exclusively by both activated states; lysyl oxidase (LOX) was the top-ranked hit. LOX knockdown abrogated TGF-{beta}-driven -smooth-muscle actin (-SMA) induction, collagen-gel contraction and migration in HMF3s, and reduced constitutive -SMA and {beta}-catenin in myCAFs. Mechanistically, TGF-{beta} upregulated LOX, which activated focal-adhesion kinase (FAK), leading to p38 MAPK- and Akt-mediated Ser9 phosphorylation (inactivation) of GSK3{beta} and consequent {beta}-catenin stabilization. In HCC1806-luciferase orthotopic xenografts, CAFs accelerated tumor growth, whereas LOX-deficient CAFs lost this pro-tumoral effect. ConclusionLOX is a pivotal autocrine effector of TGF-{beta} that locks breast CAFs into a pro-tumoral myCAF state through a LOX/FAK/GSK3{beta}/{beta}-catenin axis. Targeting stromal LOX may disrupt CAF activation and curb breast cancer progression.

cancer biology↗

bioRxiv2025

Mechanotransduction and Biophysical Regulation of Fibroblast Plasticity Under Prolonged Shear Stress

Complex interactions between mechanical stimuli and biochemical signaling shape the evolving fibrotic milieu. Fibroblasts contribute to this process, transitioning into myofibroblasts on stiffer substrates, and under low shear in 3D environments. The time-dependent effects of prolonged physiological shear stress on fibroblasts however remain poorly understood. We demonstrate that sustained shear stress (1.2 Pa) over 12 hours induces a temporal cascade of signaling and biophysical changes, driving fibroblast trans-differentiation into myofibroblasts. Cells adopt a spindle-shaped morphology under shear, actively remodeling through actin and -SMA to form elongated stress fibers. Myofibroblasts exhibit increased vinculin and zyxin expression in mature adhesions that remain elevated post-shear. Traction stresses progressively increased over the shear duration and persisted for 12 hours after the removal of the stimulus, indicating mechanical memory. Post-shear, deadhesion strengths increased significantly, accompanied by shifts in gene expressions governing extracellular matrix homeostasis. Prolonged shear enhanced MSD, directionality, and migration speed, all crucial for effective tissue repair. Finally, we demonstrate temporal changes in the biochemical gene expressions mediating the shear-induced remodeling of the extracellular matrix, cytoskeleton, and focal adhesions during the myofibroblast transition. These findings provide insights into the mechanobiological factors driving fibroblast-to-myofibroblast transitions which may inform the development of mechano-therapeutic strategies.

bioengineering↗

bioRxiv2022

Cell adhesion strength and tractions are mechano-diagnostic features of cellular invasiveness

The adhesion of cells to substrates occurs via integrin clustering and binding to the actin cytoskeleton. Oncogenes modify anchorage-dependent mechanisms in cells during cancer progression. Fluid shear devices provide a label-free, non-invasive way to characterize cell-substrate interactions and heterogeneities in the cell populations. We quantified the critical adhesion strengths of MCF7, MDAMB-231, A549, HPL1D, HeLa, and NIH3T3 cells using a custom fluid shear device. The detachment response was sigmoidal for each cell type. A549 and MDAMB-231 cells had significantly lower adhesion strengths at {tau}50 than their non-invasive counterparts, HPL1D and MCF7. Detachment dynamics was inversely correlated with cell invasion potentials. A theoretical model, based on {tau}50 values and the distribution of cell areas on substrates, provided good fits to data from de-adhesion experiments. Quantification of cell tractions, using the Reg-FTTC method on 10 kPa polyacrylamide gels, showed highest values for invasive, MDAMB-231 and A549, cells compared to non-invasive cells. Immunofluorescence studies show differences in vinculin distributions: non-invasive cells have distinct vinculin puncta, whereas invasive cells have more dispersed distributions. The cytoskeleton in non-invasive cells was devoid of well-developed stress fibers, and had thicker cortical actin bundles in the boundary. These correlations in adhesion strengths with cell invasiveness, demonstrated here, may be useful in cancer diagnostics and other pathologies featuring misregulation in adhesion.

bioengineering↗

bioRxiv2021

Substrate stiffness modulates integrin α5 expression and ECM-associated gene expression in fibroblasts

Biomaterials, like polydimethylsiloxane (PDMS), are soft, biocompatible, and tuneable, which makes them useful to delineate specific substrate factors that regulate the complex landscape of cell-substrate interactions. We used a commercial formulation of PDMS to fabricate substrates with moduli 40 kPa, 300 kPa, and 1.5 MPa, and cultured HMF3S fibroblasts on them. Gene expression analysis was performed by RT-PCR and Western blotting. Cellular and nuclear morphologies were analyzed using confocal imaging, and MMP-2 and MMP-9 activities were determined with gelatin zymography. Results, comparing mechanotransduction on PDMS substrates with control petridishes, show that substrate stiffness modulates cell morphologies and proliferations. Cell nuclei were rounded on compliant substrates and correlated with increased tubulin expression. Proliferations were higher on stiffer substrates with cell cycle arrest on softer substrates. Integrin 5 expression decreased on lower stiffness substrates, and correlated with inefficient TGF-{beta} activation. Changes to the activated state of the fibroblast on higher stiffness substrates were linked to altered TGF-{beta} secretion. Collagen I, collagen III, and MMP-2 expression levels were lower on compliant PDMS substrates as compared to stiffer ones; there was little MMP-9 activity on substrates. These results demonstrate critical feedback mechanisms between substrate stiffness and ECM regulation by fibroblasts which is highly relevant in diseases like tissue fibrosis.

bioengineering↗

bioRxiv2019

Stress fiber growth and remodeling determines cellular morphomechanics under uniaxial cyclic stretch

Stress fibers in the cytoskeleton are essential in maintaining cellular shape, and influence their adhesion and migration. Cyclic uniaxial stretching results in cellular reorientation orthogonal to the applied stretch direction via a strain avoidance reaction; the mechanistic cues in cellular mechanosensitivity to this response are currently underexplored. We show stretch induced stress fiber lengthening, their realignment and increased cortical actin in fibroblasts stretched over varied amplitudes and durations. Higher amounts of actin and alignment of stress fibers were accompanied with an increase in the effective elastic modulus of cells. Microtubules did not contribute to the measured stiffness or reorientation response but were essential to the nuclear reorientation. We modeled stress fiber growth and reorientation dynamics using a nonlinear, orthotropic, fiber-reinforced continuum representation of the cell. The model predicts the observed fibroblast morphology and increased cellular stiffness under uniaxial cyclic stretch. These studies are important in exploring the differences underlying mechanotransduction and cellular contractility under stretch.

biophysics↗

bioRxiv2018

Correlation between the aberrant human testicular germ-cell gene expression and disruption of spermatogenesis leading to male infertility

Spermatogenesis is characterized by sequential gene-expression at precise stages in progression of differentiation of the germ cells. Any alteration in expression of the critical genes is responsible for arrest of spermatogenesis associated with infertility. Inspite of advances the differential gene expression accompanying spermatogenesis, the corresponding regulatory mechanisms and their correlation to human infertility have not been clearly established. This study aims to identify the gene expression pattern of the human testicular germ cells from the patients either with obstructive azoospermia with complete intra-testicular spermatogenesis or non-obstructive azoospermia with spermatogenesis arrested at different stages and correlate the same to infertility. The testicular transcriptomes of 3 OA and 8 NOA patients and pooled testicular RNA (commercial source) were analyzed for their differential gene expression to identify potential regulators of spermatogenesis and the results were further validated in all of the 44 patients clinically diagnosed with azoospermia undergoing sperm retrieval surgery over the study period and 4 control samples included in this study. Analyses of the differential transcriptome led to identification of genes enriched in a specific testicular cell type and subsequently, several regulators of the diploid-double-diploid-haploid transitions in the human spermatogenesis were identified. Perturbations in the expression of these genes were identified as the potential causes of the spermatogenic arrest seen in azoospermia and thus the potential mediators of human male infertility. Another interesting observation was the increased autophagy in the testes of patients with non-obstructive azoospermia. The present study suggests that the regulation of the diploid-double-diploid-haploid transition is multigenic with the tandem alteration of several genes resulting in infertility. In conclusion, this study identified some of the genetic regulators controlling spermatogenesis using comparative transcriptome analyses of testicular tissues from azoospremic individuals and showed how alterations in several genes results in disruption of spermatogenesis and subsequent infertility. This study also provides interesting insights into the gene expression patterns of the Indian population that were not available earlier.

genomics↗