Biology subjects

Steward, N.

Publications and source records attributed to Steward, N..

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

A high-impact COL6A3 mutation alters the response of chondrocytes in neo-cartilage organoids to hyper-physiologic mechanical loading

ObjectivesThe etiology of osteoarthritis revolves around the interplay between genetic predisposition and perturbing environmental cues, such as mechanical stress. The pericellular matrix, with its hallmark proteins collagen type VI and fibronectin, surrounds chondrocytes and is critical in transducing the biomechanical cues. The objective is to study the functional effects of an OA disease-risk mutation in COL6A3 in interaction with hyper-physiological mechanical cues in a tailored human induced pluripotent stem cells (hiPSCs) derived cartilage organoid model. MethodTo identify pathogenic OA mutations exome sequencing in symptomatic OA patients was performed. To study functional effects, CRISPR-Cas9 genome engineering was used to introduce the mutation in our established human induced pluripotent stem cell-derived in-vitro neo-cartilage organoid model in interaction with hyper-physiological mechanical loading conditions. ResultsA high-impact mutation in COL6A3 was identified that resulted in significantly lower binding between the PCM proteins COLVI and fibronectin (FN) and provoked an osteoarthritic chondrocyte state. Moreover, aberrant function of the PCM, secondary to the COL6A3 mutation, abolished the initial stress responses marked particularly by upregulation of PTGS2 encoding cyclooxygenase-2 (COX-2), after hyper-physiological mechanical loading conditions. ConclusionThese findings demonstrate that ablating the characteristic transient COX-2 response after injurious mechanical cues may have a direct negative impact on chondrocyte health. What is already knownO_LIThe etiology of osteoarthritis revolves around the interplay between genetic predisposition and perturbing environmental cues, such as mechanical stress. C_LIO_LIThe pericellular matrix, with its hallmark proteins collagen type VI and fibronectin, surrounds the chondrocytes and is critical in transducing biomechanical cues from the extracellular matrix to chondrocytes henceforth it determines the chondrocyte mechanical environment. C_LIO_LIThe mechanical environment of the chondrocytes is a critical factor that influences chondrocyte health as it determines the balance between synthesis and degradation of the articular cartilage extracellular matrix. C_LI What this study addsO_LIA sustainable human induced pluripotent stem cell-derived in-vitro neo-cartilage organoid model that is tailored to study detailed biologic effects of mechanical cues to chondrocytes. C_LIO_LIAn OA disease-risk mutation in COL6A3 reduces the binding between collagen type VI to fibronectin and provoked an osteoarthritic chondrocyte state. C_LIO_LIUpon hyper-physiological mechanical loading, aberrant function of the pericellular matrix, secondary to the COL6A3 mutation, ablates the initial transient inflammatory response, characterized particularly by PTGS2 encoding cyclooxygenase-2 (COX-2). C_LI How this study might affect research practice or policyO_LIInhibiting COX-2, as an important transient inflammatory response after hyper-physiological mechanical cues, could worsen the loss of structural integrity of the cartilage in osteoarthritis patients. Henceforth, prescription of COX-2 inhibitors as pain treatment for OA patients should be reconsidered. C_LI

molecular biology↗

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↗

bioRxiv2019

Prospective Isolation of Chondroprogenitors from Human iPSCs Based on Cell Surface Markers Identified using a CRISPR-Cas9-Generated Reporter

Articular cartilage shows little or no capacity for intrinsic repair, generating a critical need for regenerative therapies for joint injuries and diseases such as osteoarthritis. Human induced pluripotent stem cells (hiPSCs) offer a promising cell source for cartilage tissue engineering and in vitro human disease modeling; however, heterogeneity and off-target differentiation remain a challenge. We used a CRISPR-Cas9-edited COL2A1-GFP knock-in reporter hiPSC line, coupled with a surface marker screen, to identify a novel chondroprogenitor population expressing CD146, CD166, and PDGFR{beta}, but not CD45. Under chondrogenic culture conditions, these triple positive chondroprogenitor cells demonstrated decreased heterogeneity as measured by single cell RNA sequencing, as well as more robust and homogenous matrix production with significantly higher chondrogenic gene expression. Overall, this study has identified a unique hiPSC-derived subpopulation of chondroprogenitors that are CD146+/CD166+/PDGFR{beta}+/CD45- and exhibit high chondrogenic potential, providing a purified cell source for cartilage tissue engineering or disease modeling studies.

cell biology↗

bioRxiv2018

Highly efficient chondrogenic differentiation of human iPSCs and purification via a reporter allele generated by CRISPR-Cas9 genome editing

The differentiation of human induced pluripotent stem cells (hiPSCs) to prescribed cell fates enables the engineering of patient-specific tissue types, such as hyaline cartilage, for applications in regenerative medicine, disease modeling, and drug screening. In many cases, however, these differentiation approaches are poorly controlled and generate heterogeneous cell populations. Here we demonstrate robust cartilaginous matrix production in three unique hiPSC lines using a highly efficient and reproducible differentiation protocol. To purify chondroprogenitors produced by this protocol, we engineered a COL2A1-GFP knock-in reporter hiPSC line by CRISPR-Cas9 genome editing. Purified chondroprogenitors demonstrated an improved chondrogenic capacity compared to unselected populations. The ability to enrich for chrondroprogenitors and generate homogenous matrix without contaminating cell types will be essential for regenerative and disease modeling applications.

cell biology↗