Inhibition of Rho kinase (ROCK) impairs cytoskeletal contractility in human Müller glial cells without effects on cell viability, migration, and extracellular matrix production

The epiretinal membrane is a fibrocontractile tissue that forms on the inner surface of the retina, causing visual impairment ranging from mild to severe, and even retinal detachment. Müller glial cells actively participate in the formation of this membrane. Current research is constantly seeking for new therapeutic approaches that aim to prevent or treat cellular dysfunctions involved in the progression of this common fibrosis condition. The Rho GTPases signaling pathway regulates several processes associated with the epiretinal membrane, such as cell proliferation, migration, and contraction. Rho kinase (ROCK), an effector of the RhoA GTPase, is an interesting potential therapeutic target. This study aimed to evaluate the effects of a ROCK inhibitor (Y27632) on human Müller cells viability, growth, cytoskeletal organization, expression of extracellular matrix components, myofibroblast differentiation, migration, and contractility. Müller cells of the MIO-M1 lineage were cultured and treated for different periods with the inhibitor. Viability was evaluated by MTT assay and trypan blue exclusion method, and growth was evaluated by growth curve and BrdU incorporation assay. The actin cytoskeleton was stained with fluorescent phalloidin, intermediate filaments and microtubules were analyzed with immunofluorescence for vimentin and α-tubulin. Gene and protein expression of collagens I and V, laminin and fibronectin were evaluated by rt-PCR and immunofluorescence. Chemotactic and spontaneous cell migration were studied by transwell assay and time-lapse observation of live cells, respectively. Cell contractility was assessed by collagen gel contraction assay. The results showed that ROCK inhibition by Y27632 did not affect cell viability, but decreased cell growth and proliferation after 72 h. There was a change in cell morphology and organization of F-actin, with a reduction in the cell body, disappearance of stress fibers and formation of long, branched cell extensions. Microtubules and vimentin filaments were also affected, possibly because of F-actin alterations. The inhibitor also reduced gene expression and immunoreactivity of smooth muscle α-actin, a marker of myofibroblasts. The expression of extracellular matrix components was not affected by the inhibitor. Chemotactic cell migration showed no significant changes, while cell contractility was substantially reduced. No spontaneous migration of MIO-M1 cells was observed. In conclusion, pharmacological inhibition of ROCK in Müller cells could be a potentially promising approach to treat epiretinal membranes by preventing cell proliferation, contractility and transdifferentiation, without affecting cell viability.

Biomarkers Profile in Provoked Versus Unprovoked Deep Venous Thrombosis

Venous thromboembolism (VTE), including deep venous thrombosis (DVT) and pulmonary embolism (PE), represents a substantial healthcare challenge. Provoked and unprovoked DVT cases carry distinct risks and treatment considerations. Recognizing the limitations of this classification, molecular markers may enhance diagnostic precision and guide anticoagulation therapy duration relying on patient history and risk factors. This preliminary, open-label, prospective cohort study was conducted including 15 patients (10 provoked DVT and 5 unprovoked DVT) and a control group of healthy plasmatic subjects. Plasma levels of 9 biomarkers were measured at diagnosis (baseline, day 0, and D0) and after 30 days (day 30-D30). Patient demographics, clinical data, and biomarker concentrations were analyzed. Serum concentrations of D-dimer, von Willebrand factor, C-reactive protein, and Anti-Xa were elevated in DVT groups at D0 compared to controls. No significant differences were observed between the provoked and unprovoked groups on the day of diagnosis and 30 days later. Over 30 days, the provoked group exhibited significant biomarker changes related to temporal assessment. No significant differences were noted in the biomarker profile between provoked and unprovoked DVT groups. This study is indicative of the concept of individualized thrombosis assessment and subsequent treatment for VTE. Larger cohorts are warranted to validate these findings and further define the most appropriate use of the molecular markers.

Blockade of the TGF-β pathway by galunisertib inhibits the glial-mesenchymal transition in Müller glial cells

Aging increases the risks for developing fibrocontractile membranes on the retina, which causes significant macular distortion, as in the idiopathic epiretinal membrane (iERM). Retinal Müller glial cells are components of these membranes and may play a key role in the iERM pathogenesis. The transforming growth factor-β (TGF-β) induces Müller cell transdifferentiation into myofibroblast, reducing glial cell markers (glutamine synthetase, GS, and glial fibrillary acidic protein, GFAP) and increasing α-smooth muscle actin (α-SMA). Our aim was to investigate the effect of the TGF-β inhibitor galunisertib (LY2157299) on the glial-mesenchymal transition and contraction of Müller cells. MIO-M1 human Müller cells were treated with TGF-β1 (10 ng/mL), galunisertib (5, 10 and 20 μM) and TGF-β1+galunisertib for 24h and 48h. Galunisertib cytotoxicity was analyzed by MTT and trypan blue, and TGF-β1 blockade by phospho-SMAD3 immunofluorescence. Caspase-3 (cell death indicator), GS, GFAP and α-SMA expression was examined by immunofluorescence, Western blotting, and qPCR analysis. Cell contractility was determined by collagen gel contraction assay with Müller cells incorporated. Galunisertib did not show cytotoxicity at the concentrations evaluated and maintained the Müller cells phenotype, ensuring the GS expression. Galunisertib inhibited the TGF-β1 pathway by decreasing phospho-SMAD3 immunoreactivity, attenuated the α-SMA expression, and prevented the contraction of Müller cells in collagen gel. Although more studies are needed, in vitro assays suggest that galunisertib may be a potential candidate to attenuate the formation of fibrocontractile membranes and prevent retinal detachment and consequent loss of vision.

Cellular components of the idiopathic epiretinal membrane

Idiopathic epiretinal membrane (iERM) is a fibrocellular proliferation on the inner surface of the retina, which leads to decreased visual acuity and even central visual loss. As iERM is associated to advanced age and posterior vitreous detachment, a higher prevalence is expected with increasing life expectancy and aging of the global population. Although various cell types of retinal and extra-retinal origin have been described in iERMs (Müller glial cells, astrocytes, hyalocytes, retinal pigment epithelium cells, myofibroblasts, and fibroblasts), myofibroblasts have a central role in collagen production and contractile activity. Thus, myofibroblast differentiation is considered a key event for the iERM formation and progression, and fibroblasts, Müller glial cells, hyalocytes, and retinal pigment epithelium have been identified as myofibroblast precursors. On the other side, the different cell types synthesize growth factors, cytokines, and extracellular matrix, which have a crucial role in ERM pathogenesis. In the present review, the major cellular components and their functions are summarized, and their possible roles in the iERM formation are discussed. By exploring in detail the cellular and molecular aspects of iERM, we seek to contribute for better understanding of this fibrotic disease and the origin of myofibroblasts, which may eventually drive to more targeted therapeutic approaches.