Myofibroblast transdifferentiation of keratocytes results in slower migration and lower sensitivity to mesoscale curvatures

PDGFR-α shRNA encoded nanoparticle with epithelial mesenchymal transformation interfering for corneal scarring treatment

Maintaining the clarity of the cornea is crucial for optimal vision. Corneal scarring (CS), resulting from corneal inflammation, trauma, or surgery, can lead to a reduction in corneal transparency and visual impairment. While corneal transplantation is the primary method for restoring vision, the limited availability of corneal donor presents a significant challenge on a global scale. This study aimed to develop a non-viral gene complex utilizing gene silencing technology to deliver interfering fragments of the platelet-derived growth factor alpha receptor (PDGFR-α) to prevent CS. The hydrophilic segment of polyethylene glycol on the surface of the complex significantly improved its cellular safety as a delivery vehicle. The proton sponge effect of cationic carriers facilitates the escape of the target fragment from lysosomes and enables its entry into the cytoplasm for gene interference. In the TGF-β-induced epithelial-mesenchymal transition (EMT) cell model, it demonstrates remarkable capabilities in inhibiting cell fibrosis and migration. A mouse model was utilized to assess the gene complex's capacity to penetrate into the cornea and inhibit the production of corneal scar. This study highlights the significance of inhibiting the EMT process as a potential strategy for treating fibrosis, and has achieved technical success in intervening in corneal scarring.

Macromolecular crowding agent dependent extracellular matrix deposition and growth factor retention in human corneal fibroblast cultures

The major obstacle in the commercialisation and clinical translation of tissue engineered medicines is the required for the development of implantable tissue surrogates prolonged in vitro culture. Macromolecular crowding (MMC) enhances and accelerates extracellular matrix (ECM) deposition, thus offering an opportunity to bridge the gap between research and development in tissue engineered substitutes. However, the optimal MMC agent is still elusive. Herein, we first assessed the biophysical properties of the most widely used MMC agents [κλ carrageenan (κλ CR), λ carrageenan (λ CR) and Ficoll™ cocktail (FC)] and then assessed their effect in basic cell function, ECM deposition and growth factor retention in human corneal fibroblast (hCF) cultures. Dynamic light scattering analysis revealed that both CR macromolecules had significantly lower and higher zeta potential and hydrodynamic radius, respectively, than the FC. None of the MMC agents affected hCF morphology and all induced similar hCF viability, proliferation and metabolic activity. Electrophoresis and immunofluorescence analyses made apparent that at day 10 (longest time point assessed), the FC brought about the highest fibronectin and collagen types I, III, IV, V and VI deposition. Deposited ECM pattern analysis showed that at day 10, the FC induced the lowest lacunarity and normalised end points and the highest fractal dimension and % high density matrix. Further immunofluorescence analysis revealed no significant differences between the groups in vimentin, aldehyde dehydrogenase 3 family member A1, keratocan, paired box protein 6 and α-smooth muscle actin. Importantly, at day 10, the FC resulted in the highest growth factor retention (20 molecules). Our data clearly illustrate a MMC agent dependent cell response, with the FC having the highest positive effect in hCF cultures.

Analysis of Smad3 in the modulation of stromal extracellular matrix proteins in corneal scarring after alkali injury

Purpose

During ocular trauma, excessive proliferation and transdifferentiation of corneal stromal fibroblasts cause haze/fibrosis in the cornea. Transforming growth factor β (TGFβ) plays a key role in corneal fibrosis through the Smad signaling pathway. The aberrant activity of TGFβ signaling during ocular trauma (viz. mechanical, infectious, chemical, or surgically altered TGFβ/Smad signaling) leads to regulating the predominant expression of myogenic proteins and the extracellular matrix (ECM). We sought to investigate the functional role of Smad3 in corneal wound repair and stromal ECM assembly using Smad3+/+ wild-type and Smad3-/- deficient mice.

Methods

Corneal injury was introduced with the topical application of an alkali-soaked 2-mm filter disc on the central cornea in the Smad3+/+ (C57BL/6J) and Smad3-/- (129-Smad3tm1Par/J) mouse strains. Slit-lamp and stereo microscopy were used for clinical assessment and corneal haze grading in live animals. Hematoxylin and eosin and Masson's trichrome staining were used to study comparative morphology and collagen level alterations between the groups. Real-time qRT-PCR, western blot, and immunohistochemistry were used to measure changes in profibrotic genes at the mRNA and protein levels.

Results

Slit-lamp clinical exams and stereo microscopy detected notably less opaque cornea in the eyes of Smad3-/- compared with Smad3+/+ mice at 3 weeks (p<0.01) in live animals. Corneal tissue sections of Smad3-/- mice showed significantly fewer α-smooth muscle actin-positive cells compared with those of the Smad3+/+ animals (p<0.05). The corneas of the Smad3-/- mice showed significantly lower mRNA levels of pro-fibrotic genes, α-smooth muscle actin, fibronectin, and collagen I (p<0.05, p<0.01, and p<0.001). In addition, the matrix metalloproteinase and tissue inhibitors of metalloproteinase levels were significantly increased (p<0.001) in the corneal tissue during alkali injury in both Smad3+/+ wild-type and Smad3-/- deficient mice.

Conclusions

The significant changes in profibrotic genes and stromal ECM proteins revealed a direct role of Smad3 in stromal ECM proteins and TGFβ/Smad-driven wound healing. Smad3 appears to be an attractive molecular target for limiting abnormal stroma wound healing to treat corneal fibrosis in vivo.

Crosstalk among miR-29, α-SMA, and TGFβ1/β3 in melatonin-induced exosome (Mel-prExo) treated human limbal mesenchymal stem cells (hLMSCs): An insight into scarless healing of the cornea

Inflammatory mediators that infiltrate the corneal stroma after corneal infections, trauma or refractive surgery can trigger the transformation of corneal keratocytes into myofibroblasts, resulting in highly irregular collagen deposition and subsequently corneal scarring. Mesenchymal stem cells (MSCs) can be used as therapeutic agents to regenerate corneal and conjunctival tissue damage, regulate inflammation, and reduce the development of limbal stem cell failure. The use of MSC-derived exosomes as a cell-free therapeutic vector is a novel therapeutic approach. This study aimed to assess the effect of exosomes obtained from melatonin (Mel)-treated human limbal mesenchymal stem cells (hLMSCs) on naïve hLMSCs and to determine their influence on the antifibrotic and pro-regenerative pathways involved in corneal scarring. hLMSCs were treated with varying concentrations of Mel, followed by isolation and characterization of the procured exosomes (Mel-prExos). These exosomes were added to the cell culture media of naïve hLMSCs to examine their antifibrotic and pro-regenerative effects. The expression of miR-155, miR-29, TGFβ1, TGFβ3, PPARγ, and α-SMA miRNAs and genes were compared between Mel-treated hLMSCs and Mel-prExo-treated hLMSCs by using real-time PCR. We found that at 1 μM Mel and in the presence of Mel-prExos, TGFβ1 was expressed 0.001-fold, while TGFβ3 was expressed 0.6-fold. miR-29 expression was increased 38-fold in the control-Exo group compared to that in the control group. Changes in TGFβ1/β3 and α-SMA expression are associated with miR-29 and miR-155. This approach could prove beneficial for ocular surface tissue engineering applications.

A minimal physical model for curvotaxis driven by curved protein complexes at the cell's leading edge

Cells often migrate on curved surfaces inside the body, such as curved tissues, blood vessels, or highly curved protrusions of other cells. Recent in vitro experiments provide clear evidence that motile cells are affected by the curvature of the substrate on which they migrate, preferring certain curvatures to others, termed "curvotaxis." The origin and underlying mechanism that gives rise to this curvature sensitivity are not well understood. Here, we employ a "minimal cell" model which is composed of a vesicle that contains curved membrane protein complexes, that exert protrusive forces on the membrane (representing the pressure due to actin polymerization). This minimal-cell model gives rise to spontaneous emergence of a motile phenotype, driven by a lamellipodia-like leading edge. By systematically screening the behavior of this model on different types of curved substrates (sinusoidal, cylinder, and tube), we show that minimal ingredients and energy terms capture the experimental data. The model recovers the observed migration on the sinusoidal substrate, where cells move along the grooves (minima), while avoiding motion along the ridges. In addition, the model predicts the tendency of cells to migrate circumferentially on convex substrates and axially on concave ones. Both of these predictions are verified experimentally, on several cell types. Altogether, our results identify the minimization of membrane-substrate adhesion energy and binding energy between the membrane protein complexes as key players of curvotaxis in cell migration.

Regulation of Corneal Stromal Cell Behavior by Modulating Curvature Using a Hydraulically Controlled Organ Chip Array

Curvature is a critical factor in cornea mechanobiology, but its impact on phenotypic alterations and extracellular matrix remodeling of cornea stroma remains unclear. In this work, we investigated how curvature influences the corneal stroma using a hydraulically controlled curvature array chip. The responses of stromal cells to low, medium, and high curvatures were observed by preparing three phenotypes of corneal stromal cells: corneal keratocytes, fibroblasts, and myofibroblasts. Keratocytes exhibited phenotypic alterations in response to curvature changes, notably including a decrease in ALDH3 expression and an increase in α-SMA expression. For focal adhesion, corneal fibroblast and myofibroblasts showed enhanced vinculin localization in response to curvature, while corneal keratocytes presented reduced vinculin expression. For cell alignment and ECM expression, most stromal cells under all curvatures showed a radially organized f-actin and collagen fibrils. Interestingly, for corneal fibroblast under medium curvature, we observed orthogonal cell alignment, which is linked to the unique hoop and meridional stress profiles of the curved surface. Furthermore, lumican expression was upregulated in corneal keratocytes, and keratocan expression was increased in corneal fibroblasts and myofibroblasts due to curvature. These results demonstrate that curvature influences both the phenotype of corneal stromal cells and the structural organization of corneal stroma tissue without any external stimuli. This curvature-dependent behavior of corneal stromal cells presents potential opportunities for creating therapeutic strategies for corneal shape dysfunctions.

The Dual-Mode Transition of Myofibroblasts Derived from Hepatic Stellate Cells in Liver Fibrosis

Hepatic stellate cells (HSCs) are the key promoters of liver fibrosis. In response to liver-fibrosis-inducing factors, HSCs express alpha smooth muscle actin (α-SMA) and obtain myofibroblast phenotype. Collagen secretion and high expression of α-SMA with related high cell tension and migration limitation are the main characteristics of myofibroblasts. How these two characteristics define the role of myofibroblasts in the initiation and progression of liver fibrosis is worth exploring. From this perspective, we explored the correlation between α-SMA expression and collagen secretion in myofibroblasts and the characteristics of collagen deposition in liver fibrosis. Based on a reasonable hypothesis and experimental verification, we believe that the myofibroblast with the α-SMAhighcollagenhigh model do not effectively explain the initial stage and progression characteristics of liver fibrosis. Therefore, we propose a myofibroblast dual-mode transition model in fibrotic liver (DMTM model). In the DMTM model, myofibroblasts have dual modes. Myofibroblasts obtain enhanced α-SMA expression, accompanied by collagen expression inhibition in the high-concentration region of TGF-β. At the edge of the TGF-β positive region, myofibroblasts convert to a high-migration and high-collagen secretion phenotype. This model reasonably explains collagen deposition and expansion in the initial stage of liver fibrosis.