Biology subjects

Barker, T. H.

Publications and source records attributed to Barker, T. H..

3 recordsLinked to original sources

bioRxiv2021

Myeloid-mediated IL-1R signaling in immuno-responsive Thy-1 negative fibroblasts is critical for pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal disease with poorly defined pathogenic mechanism and no cure. It is characterized by chronic inflammation, myofibroblast accumulation, and aberrant extracellular matrix (ECM) remodeling. Fibrosis progression is considered to occur due to sustained aberrant fibroblast mechanotransduction: sensing "normal" soft tissue as stiff scarred tissue leading to the overproduction of ECM that then stiffens the microenvironment, thus reinforcing a progressive, stiffness-dependent fibrotic program. How chronic inflammation leads to aberrant mechanotransduction is not well understood. Thy-1 is a regulator of mechanotransduction in fibroblasts. Thy-1 expression is lost in fibroblastic foci, the active sites of fibrosis, although the mechanism of this loss is unknown. We demonstrate that in IPF tissue, the SMA+ fibroproliferative foci express the Type 1 IL-1 receptor (IL-1RI) and IL-1RI-deficient mice did not develop bleomycin-induced pulmonary fibrosis. Using ASC speck formation during inflammasome activation as a marker of mature IL-1{beta} release, we identified the immune compartment as the source of active IL-1{beta} during bleomycin-induced fibrosis. Furthermore, incubating mouse lung fibroblasts on soft (2kPa) hydrogels with IL-1{beta} was sufficient to reduce Thy-1 surface expression and induce v{beta}3 integrin activation. As expected, Thy-1 negative fibroblasts exhibited elevated v{beta}3 integrin activation but surprisingly, Thy-1 negative fibroblasts also expressed higher levels of IL-1RI, potentially linking the immuno-responsive and mechanosensitivity of this fibroblast subpopulation. Leveraging the non-resolving fibrosis that occurs in Thy-1-/- mice, we observed that crossing Thy-1-/- mice onto the IL-1RI-/- background was sufficient to reduce fibrosis. Together, these data indicate that Thy-1 negative fibroblasts are an immuno-responsive subpopulation that also display altered mechanotransduction, potentially serving as the link between the noted inflammation and aberrant mechanotransduction observed in IPF.

cell biology↗

bioRxiv2021

The combined influence of viscoelastic and adhesive cues on fibroblast spreading and focal adhesion formation

Tissue fibrosis is characterized by progressive extracellular matrix (ECM) stiffening and loss of viscoelasticity that ultimately results in reduced organ functionality. Cells bind to the ECM through integrins, where av integrin engagement in particular has been correlated with fibroblast activation into contractile myofibroblasts that drive fibrosis progression. There is a significant unmet need for in vitro hydrogel systems that deconstruct the complexity of native tissues to better understand the individual and combined effects of stiffness, viscoelasticity, and integrin engagement on fibroblast behavior. Here, we developed hyaluronic acid hydrogels with independently tunable cell-instructive properties (stiffness, viscoelasticity, ligand presentation) to address this challenge. Hydrogels with mechanics matching normal or fibrotic lung tissue were synthesized using a combination of covalent crosslinks and supramolecular interactions to tune viscoelasticity. Cell adhesion was mediated through incorporation of either RGD peptide or engineered fibronectin fragments promoting preferential integrin engagement via v{beta}3 or 5{beta}1. We showed that preferential v{beta}3 engagement enabled human lung fibroblasts to assume a myofibroblast-like phenotype on fibrosis-mimicking stiff elastic hydrogels with increased spreading, actin stress fiber organization, and focal adhesion maturation as indicated by paxillin organization. In contrast, preferential 5{beta}1 binding suppressed these metrics. Viscoelasticity, mimicking the mechanics of healthy tissue, largely curtailed fibroblast spreading and focal adhesion organization independent of adhesive ligand type, highlighting its role in preventing fibroblast activation. Together these results provide new insights into how mechanical and adhesive cues collectively guide disease-relevant cell behaviors.

bioengineering↗

bioRxiv2021

The Amot/Integrin protein complex transmits mechanical forces required for vascular expansion

Vascular development is a complex multistep process involving the coordination of cellular functions such as migration, proliferation and differentiation. Understanding the underlying mechanisms of these processes is of importance due to involvement of vessel expansion in various pathologies. How mechanical forces generated by cells and transmission of these physical forces control vascular development is poorly understood. Using an endothelial-specific genetic model in mice, we show that deletion of the scaffold protein, Angiomotin (Amot), inhibits migration and expansion of physical and pathological vascular network. We further show that Amot is required for tip cell migration and the extension of cellular filopodia. Exploiting in vivo and in vitro molecular approaches, we show that Amot binds talin and is essential for relaying forces between fibronectin and the cytoskeleton. Finally, we provide evidence that Amot is a novel component of the endothelial integrin adhesome and propose that Amot integrates spatial cues from the extra-cellular matrix in order to form a functional vascular network.

cell biology↗