Biology subjects

Savadipour, A.

Publications and source records attributed to Savadipour, A..

5 recordsLinked to original sources

bioRxiv2024

PIEZO1-Mediated Mechanotransduction Regulates Collagen Synthesis on Nanostructured 2D and 3D Models of Fibrosis

Progressive fibrosis causes tissue malfunction and organ failure due to the pathologic accumulation of a collagen-rich extracellular matrix. In vitro models provide useful tools for deconstructing the roles of specific biomechanical or biological mechanisms involved in these processes and identifying potential therapeutic targets. In particular, recent studies have implicated cellular mechanosensing of substrate micro- and nanoscale architecture as a regulator of fibrosis. In this study, we investigated how the mechanosensitive ion channel PIEZO1 and intracellular mechanotransduction pathways influence fibrotic gene and protein expression in adipose-derived stem cells (hASCs). Specifically, we examined the role of PIEZO1 and the mechano-sensitive transcription factors YAP/TAZ in sensing aligned or non-aligned substrate architecture to regulate collagen formation. We utilized both 2D microphotopatterned substrates and 3D electrospun polycaprolactone (PCL) substrates to study the role of culture dimensionality. We found that PIEZO1 regulates collagen production in hASCs in a manner that is sensitive to substrate architecture. Activation of PIEZO1 induced significant morphological changes in hASCs, particularly when they were cultured on aligned substrates. While YAP translocated to the cytoplasm following PIEZO1 activation, depleting YAP and TAZ did not change collagen expression significantly downstream of PIEZO1 activation, implying that YAP/TAZ translocation out of the nucleus and increased collagen production may be independent outputs of PIEZO1 activation. Our studies demonstrate a role for PIEZO1 in cellular mechanosensing of substrate architecture and provide targetable pathways for treating fibrosis as well as for enhancing tissue-engineered and regenerative approaches for fibrous tissue repair.

bioengineering↗

bioRxiv2022

Modulation of TRPV4 Protects against Degeneration Induced by Sustained Loading and Promotes Matrix Synthesis in the Intervertebral Disc

While it is well-known that mechanical signals can either promote or disrupt intervertebral disc (IVD) homeostasis, the molecular mechanisms for transducing mechanical stimuli are not fully understood. The transient receptor potential vanilloid 4 (TRPV4) ion channel activated in isolated IVD cells initiates extracellular matrix (ECM) gene expression, while TRPV4 ablation reduces cytokine production in response to circumferential stretching. However, the role of TRPV4 on ECM maintenance during tissue-level mechanical loading remains unknown. Using an organ culture model, we modulated TRPV4 function over both short-(hours) and long-term (days) and evaluated IVDs response. Activating TRPV4 with the agonist GSK101 resulted in a Ca2+ flux propagating across the cells within the IVD. NF-{kappa}B signaling in the IVD peaked at 6 hours following TRPV4 activation that subsequently resulted in higher IL-6 production at 7 days. These cellular responses were concomitant with the accumulation of glycosaminoglycans and increased hydration in the nucleus pulposus that culminated in higher stiffness of the IVD. Sustained compressive loading of the IVD resulted in elevated NF-{kappa}B activity, IL-6 and VEGF-A production, and degenerative changes to the ECM. TRPV4 inhibition using GSK205 during loading mitigated the changes in inflammatory cytokines, protected against IVD degeneration, and but could not prevent ECM disorganization due to mechanical damage in the annulus fibrosus. These results indicate TRPV4 plays an important role in both short-and long-term adaptations of the IVD to mechanical loading. The modulation of TRPV4 may be a possible therapeutic for preventing load-induced IVD degeneration.

pathology↗

bioRxiv2021

Skeletal dysplasia-causing TRPV4 mutations suppress the hypertrophic differentiation of human iPSC-derived chondrocytes

Mutations in the TRPV4 ion channel can lead to a range of skeletal dysplasias. However, the mechanisms by which TRPV4 mutations lead to distinct disease severity remain unknown. Here, we use CRISPR-Cas9-edited human induced pluripotent stem cells (hiPSCs) harboring either the mild V620I or lethal T89I mutations to elucidate the differential effects on channel function and chondrogenic differentiation. We found that hiPSC-derived chondrocytes with the V620I mutation exhibited increased basal currents through TRPV4. However, both mutations showed more rapid calcium signaling with a reduced overall magnitude in response to TRPV4 agonist GSK1016790A compared to wildtype. There were no differences in overall cartilaginous matrix production, but the V620I mutation resulted in reduced mechanical properties of cartilage matrix later in chondrogenesis. mRNA sequencing revealed that both mutations upregulated several anterior HOX genes and downregulated antioxidant genes CAT and GSTA1 throughout chondrogenesis. BMP4 treatment upregulated several essential hypertrophic genes in WT chondrocytes; however, this hypertrophic maturation response was inhibited in mutant chondrocytes. These results indicate that the TRPV4 mutations alter BMP signaling in chondrocytes and prevent proper chondrocyte hypertrophy, as a potential mechanism for dysfunctional skeletal development. Our findings provide potential therapeutic targets for developing treatments for TRPV4-mediated skeletal dysplasias.

developmental biology↗

bioRxiv2020

Osteoarthritis: articular chondrocyte inflammatory signaling leads to enhanced gene expression and function of mechanotransduction channel Piezo1 as a pathogenic feedforwardmechanism

Osteoarthritis (OA) is a painful and debilitating condition of synovial joints without any disease-modifying therapies (1, 2). We previously identified mechanosensitive PIEZO channels, PIEZO1 and PIEZO2, both expressed in articular cartilage, to function in chondrocyte mechanotransduction in response to injury (3, 4). We therefore asked whether interleukin-1-mediated inflammatory signaling, as occurs in OA, influences Piezo gene expression and channel function, thus indicative of maladaptive reprogramming that can be rationally targeted. Primary porcine chondrocyte culture and human osteoarthritic cartilage tissue were studied. We found that interleukin-1 (IL-1) upregulated Piezo1 in porcine chondrocytes. Piezo1 expression was significantly increased in human osteoarthritic cartilage. Increased Piezo1 expression in chondrocytes resulted in a feed-forward pathomechanism whereby increased function of Piezo1 induced excess intracellular Ca2+, at baseline and in response to mechanical deformation. Elevated resting state Ca2+ in turn rarefied the F-actin cytoskeleton and amplified mechanically-induced deformation-microtrauma. As intracellular substrates of this novel OA-related inflammatory pathomechanism, in porcine articular chondrocytes exposed to IL-1 we discovered that enhanced Piezo1 expression depended on p38 MAP-kinase and transcription factors HNF4 and ATF2/CREBP1. CREBP1 directly bound to the proximal PIEZO1 gene promoter. In ensemble, these signaling and genetic re-programming events represent a novel and detrimental Ca2+-driven feed-forward mechanism that can be rationally targeted to stem the progression of OA. Significance StatementOsteoarthritis affecting weight-bearing joints is a global health problem, causing loss of mobility and enormous healthcare costs. Disease-modifying approaches are lacking. Here, we report a new cellular mechanism of inflammatory signaling in chondrocytes, the cellular substrate of cartilage. We show how osteoarthritis-relevant levels of interleukin-1 reprogram articular chondrocytes so that they become more susceptible to mechanical trauma, which chondrocytes sense via Piezo1/2 mechanosensitive ion channels. We uncover that IL-1 enhances gene expression of Piezo1 in primary articular chondrocytes underlying Piezo1 gain-of-function. We elucidate the new signaling pathway, from membrane to nucleus, including transcription factors that enhance Piezo1-expression. We also define detrimental effects of gain-of-function of Piezo1, for mechanotransduction and at-rest, that suggest this new reprogramming mechanism to contribute to osteoarthritis pathogenesis.

molecular biology↗

bioRxiv2020

A synthetic mechanogenetic gene circuit for autonomous drug delivery in engineered tissues

Mechanobiologic signals regulate cellular responses under physiologic and pathologic conditions. Using synthetic biology and tissue engineering, we developed a mechanically-responsive bioartificial tissue that responds to mechanical loading to produce a pre-programmed therapeutic biologic drug. By deconstructing the signaling networks induced by activation of the mechanically-sensitive ion channel transient receptor potential vanilloid 4 (TRPV4), we created synthetic TRPV4-responsive genetic circuits in chondrocytes. We engineered these cells into living tissues that respond to mechanical loading by producing the anti-inflammatory biologic drug, interleukin-1 receptor antagonist. Chondrocyte TRPV4 is activated by osmotic loading and not direct cellular deformation, suggesting tissue loading is transduced into an osmotic signal that activates TRPV4. Either osmotic or mechanical loading of tissues transduced with TRPV4-responsive circuits protected constructs from inflammatory degradation by interleukin-1. This synthetic mechanobiology approach was used to develop a mechanogenetic system to enable long-term, autonomously regulated drug delivery driven by physiologically-relevant loading.

synthetic biology↗