Wound contraction is attenuated by fasudil inhibition of Rho-associated kinase

Spider-Silk-like Fiber Mat-Covered Polypropylene Warp-Knitted Hernia Mesh for Inhibition of Fibrosis under Dynamic Environment

Hernia surgery is a widely performed procedure, and the use of a polypropylene mesh is considered the standard approach. However, the mesh often leads to complications, including the development of scar tissue that wraps around the mesh and causes it to shrink. Consequently, there is a need to investigate the relationship between the mesh and scar formation as well as to develop a hernia mesh that can prevent fibrosis. In this study, three different commercial polypropylene hernia meshes were examined to explore the connection between the fabric structure and mechanical properties. In vitro dynamic culture was used to investigate the mechanism by which the mechanical properties of the mesh in a dynamic environment affect cell differentiation. Additionally, electrospinning was employed to create polycaprolactone spider-silk-like fiber mats to achieve mechanical energy dissipation in dynamic conditions. These fiber mats were then combined with the preferred hernia mesh. The results demonstrated that the composite mesh could reduce the activation of fibroblast mechanical signaling pathways and inhibit its differentiation into myofibroblasts in dynamic environments.

Pharmacotherapy of urethral stricture

Urethral stricture is characterized by the chronic formation of fibrous tissue, leading to the narrowing of the urethral lumen. Despite the availability of various endoscopic treatments, the recurrence of urethral strictures remains a common challenge. Postsurgery pharmacotherapy targeting tissue fibrosis is a promising option for reducing recurrence rates. Although drugs cannot replace surgery, they can be used as adjuvant therapies to improve outcomes. In this regard, many drugs have been proposed based on the mechanisms underlying the pathophysiology of urethral stricture. Ongoing studies have obtained substantial progress in treating urethral strictures, highlighting the potential for improved drug effectiveness through appropriate clinical delivery methods. Therefore, this review summarizes the latest researches on the mechanisms related to the pathophysiology of urethral stricture and the drugs to provide a theoretical basis and new insights for the effective use and future advancements in drug therapy for urethral stricture.

Modulating mechanobiology as a therapeutic target for synovial fibrosis to restore joint lubrication

OBJECTIVES

Fibroses are disorders linked to persistence of myofibroblasts due to biochemical (e.g., Transforming growth factor-β) and biophysical cues (e.g., a stiff microenvironment). In the context of osteoarthritis, fibrotic changes in the joint-lining synovium have been linked with disease progression. The objective of this study was to probe synovial fibroblast mechanobiology and how essential functions (i.e., lubrication) are altered in fibrotic environments.

DESIGN

Both ex vivo and in vitro synovium models were assessed for fibrotic and lubrication biomarkers to better understand the role of mechanobiology and lubrication. Additionally, in vitro, work on small molecules targeting mechanobiology was assessed.

RESULTS

Our results indicated that modulating mechanobiology could rescue the fibrotic phenotype instigated by stiffening microenvironment that resulted in altered lubricant expression. A small molecule therapeutic, fasudil, blocked ROCK-mediated contractility and this inhibition of the fibrotic mechano-response of synovial fibroblasts restored proper lubrication function, providing insight into mechanisms of disease progression as well as a new avenue for therapeutic development.

CONCLUSION

This study identifies synovial fibrosis as a condition that potentially has joint-wide deficits through inhibiting lubrication. Additionally, modulating mechanobiology (i.e., ROCK-mediated contractility) may pose a potential target for small molecule therapies that can be delivered to the joint space.

CLASSIFICATION

Applied Biological Sciences.

A high-salt diet promotes hypertrophic scarring through TRPC3-mediated mitochondrial Ca2+ homeostasis dysfunction

Diet High in salt content have been associated with cardiovascular disease and chronic inflammation. We recently demonstrated that transient receptor potential canonical 3 (TRPC3) channels regulate myofibroblast transdifferentiation in hypertrophic scars. Here, we examined how high salt activation of TRPC3 participates in hypertrophic scarring during wound healing. In vitro, we confirmed that high salt increased the TRPC3 protein expression and the marker of myofibroblast alpha smooth muscle actin (α-SMA) in wild-type mice (WT) primary cultured dermal fibroblasts but not Trpc3-/- mice. Activation of TRPC3 by high salt elevated cytosolic Ca2+ influx and mitochondrial Ca2+ uptake in dermal fibroblasts in a TRPC3-dependent manner. High salt activation of TRPC3 enhanced mitochondrial respiratory dysfunction and excessive ROS production by inhibiting pyruvate dehydrogenase action, that activated ROS-triggered Ca2+ influx and the Rho kinase/MLC pathway in WT mice but not Trpc3-/- mice. In vivo, a persistent high-salt diet promoted myofibroblast transdifferentiation and collagen deposition in a TRPC3-dependent manner. Therefore, this study demonstrates that high salt enhances myofibroblast transdifferentiation and promotes hypertrophic scar formation through enhanced mitochondrial Ca2+ homeostasis, which activates the ROS-mediated pMLC/pMYPT1 pathway. TRPC3 deficiency antagonizes high salt diet-induced hypertrophic scarring. TRPC3 may be a novel target for hypertrophic scarring during wound healing.

Positive feedback loops between fibroblasts and the mechanical environment contribute to dermal fibrosis

Dermal fibrosis is characterized by excessive deposition of extracellular matrix in the dermis and affects millions of people worldwide and causes limited movement, disfigurement and psychological distress in patients. Fibroblast dysfunction of plays a central role in the pathogenesis of dermal fibrosis and is controlled by distinct factors. Recent studies support the hypothesis that fibroblasts can drive matrix deposition and stiffening, which in turn can exacerbate the functional dysregulation of fibroblasts. Ultimately, through a positive feedback loop, uncontrolled pathological fibrosis develops. This review aims to summarize the phenomenon and mechanism of the positive feedback loop in dermal fibrosis, and discuss potential therapeutic targets to help further elucidate the pathogenesis of dermal fibrosis and develop therapeutic strategies. In this review, fibroblast-derived compositional and structural changes in the ECM that lead to altered mechanical properties are briefly discussed. We focus on the mechanisms by which mechanical cues participate in dermal fibrosis progression. The mechanosensors discussed in the review include integrins, DDRs, proteoglycans, and mechanosensitive ion channels. The FAK, ERK, Akt, and Rho pathways, as well as transcription factors, including MRTF and YAP/TAZ, are also discussed. In addition, we describe stiffness-induced biological changes in the ECM on fibroblasts that contribute to the formation of a positive feedback loop. Finally, we discuss therapeutic strategies to treat the vicious cycle and present important suggestions for researchers conducting in-depth research.

The Role of Myofibroblasts in Physiological and Pathological Tissue Repair

Myofibroblasts are the construction workers of wound healing and repair damaged tissues by producing and organizing collagen/extracellular matrix (ECM) into scar tissue. Scar tissue effectively and quickly restores the mechanical integrity of lost tissue architecture but comes at the price of lost tissue functionality. Fibrotic diseases caused by excessive or persistent myofibroblast activity can lead to organ failure. This review defines myofibroblast terminology, phenotypic characteristics, and functions. We will focus on the central role of the cell, ECM, and tissue mechanics in regulating tissue repair by controlling myofibroblast action. Additionally, we will discuss how therapies based on mechanical intervention potentially ameliorate wound healing outcomes. Although myofibroblast physiology and pathology affect all organs, we will emphasize cutaneous wound healing and hypertrophic scarring as paradigms for normal tissue repair versus fibrosis. A central message of this review is that myofibroblasts can be activated from multiple cell sources, varying with local environment and type of injury, to either restore tissue integrity and organ function or create an inappropriate mechanical environment.

Mechanotransduction in skin wound healing and scar formation: Potential therapeutic targets for controlling hypertrophic scarring

Hypertrophic scarring (HTS) is a major source of morbidity after cutaneous injury. Recent studies indicate that mechanical force significantly impacts wound healing and skin regeneration which opens up a new direction to combat scarring. Hence, a thorough understanding of the underlying mechanisms is essential in the development of efficacious scar therapeutics. This review provides an overview of the current understanding of the mechanotransduction signaling pathways in scar formation and some strategies that offload mechanical forces in the wounded region for scar prevention and treatment.

Mechanical stretch sustains myofibroblast phenotype and function in microtissues through latent TGF-β1 activation

Developing methods to study tissue mechanics and myofibroblast activation may lead to new targets for therapeutic treatments that are urgently needed for fibrotic disease. Microtissue arrays are a promising approach to conduct relatively high-throughput research into fibrosis as they recapitulate key biomechanical aspects of the disease through a relevant 3D extracellular environment. In early work, our group developed a device called the MVAS-force to stretch microtissues while enabling simultaneous assessment of their dynamic mechanical behavior. Here, we investigated TGF-β1-induced fibroblast to myofibroblast differentiation in microtissue cultures using our MVAS-force device through assessing α-SMA expression, contractility and stiffness. In doing so, we linked cell-level phenotypic changes to functional changes that characterize the clinical manifestation of fibrotic disease. As expected, TGF-β1 treatment promoted a myofibroblastic phenotype and microtissues became stiffer and possessed increased contractility. These changes were partially reversible upon TGF-β1 withdrawal under a static condition, while, in contrast, long-term cyclic stretching maintained myofibroblast activation. This pro-fibrotic effect of mechanical stretching was absent when TGF-β1 receptors were inhibited. Furthermore, stretching promoted myofibroblast differentiation when microtissues were given latent TGF-β1. Altogether, these results suggest that external mechanical stretch may activate latent TGF-β1 and, accordingly, might be a powerful stimulus for continued myofibroblast activation to progress fibrosis. Further exploration of this pathway with our approach may yield new insights into myofibroblast activation and more effective therapeutic treatments for fibrosis.

Netarsudil-related Eyelid Wound Dehiscence

An 81-year-old man with primary open-angle glaucoma on dorzolamide-timolol, bimatoprost and 0.02% netarsudil ophthalmic solution (Rhopressa), was found to have right lower lid basal cell carcinoma. The patient underwent Mohs surgery followed by repair of the right lower lid, with 3 episodes of wound dehiscence. When stopping netarsudil, appropriate granulation tissue was able to develop. While off netarsudil, the patient underwent Mohs resection of a left lower lid basal cell carcinoma, which was able to granulate well via secondary intention.

A story of fibers and stress: Matrix-embedded signals for fibroblast activation in the skin

Our skin is continuously exposed to mechanical challenge, including shear, stretch, and compression. The extracellular matrix of the dermis is perfectly suited to resist these challenges and maintain integrity of normal skin even upon large strains. Fibroblasts are the key cells that interpret mechanical and chemical cues in their environment to turnover matrix and maintain homeostasis in the skin of healthy adults. Upon tissue injury, fibroblasts and an exclusive selection of other cells become activated into myofibroblasts with the task to restore skin integrity by forming structurally imperfect but mechanically stable scar tissue. Failure of myofibroblasts to terminate their actions after successful repair or upon chronic inflammation results in dysregulated myofibroblast activities which can lead to hypertrophic scarring and/or skin fibrosis. After providing an overview on the major fibrillar matrix components in normal skin, we will interrogate the various origins of fibroblasts and myofibroblasts in the skin. We then examine the role of the matrix as signaling hub and how fibroblasts respond to mechanical matrix cues to restore order in the confusing environment of a healing wound.

Myocardin‑related transcription factor A nuclear translocation contributes to mechanical overload‑induced nucleus pulposus fibrosis in rats with intervertebral disc degeneration

Previous studies have reported that the Ras homolog family member A (RhoA)/myocardin‑related transcription factor A (MRTF‑A) nuclear translocation axis positively regulates fibrogenesis induced by mechanical forces in various organ systems. The aim of the present study was to determine whether this signaling pathway was involved in the pathogenesis of nucleus pulposus (NP) fibrosis induced by mechanical overload during the progression of intervertebral disc degeneration (IVDD) and to confirm the alleviating effect of an MRTF‑A inhibitor in the treatment of IVDD. NP cells (NPCs) were cultured on substrates of different stiffness (2.9 and 41.7 KPa), which mimicked normal and overloaded microenvironments, and were treated with an inhibitor of MRTF‑A nuclear import, CCG‑1423. In addition, bipedal rats were established by clipping the forelimbs of rats at 1 month and gradually elevating the feeding trough, and in order to establish a long‑term overload‑induced model of IVDD, and their intervertebral discs were injected with CCG‑1423 in situ. Cell viability was determined by Cell Counting Kit‑8 assay, and protein expression was determined by western blotting, immunofluorescence and immunohistochemical staining. The results demonstrated that the viability of NPCs was not affected by the application of force or the inhibitor. In NPCs cultured on stiff matrices, MRTF‑A was mostly localized in the nucleus, and the expression levels of fibrotic proteins, including type I collagen, connective tissue growth factor and α‑smooth muscle cell actin, were upregulated compared with those in NPCs cultured on soft matrices. The levels of these proteins were reduced by CCG‑1423 treatment. In rats, 6 months of upright posture activated MRTF‑A nuclear‑cytoplasmic trafficking and fibrogenesis in the NP and induced IVDD; these effects were alleviated by CCG‑1423 treatment. In conclusion, the results of the present study demonstrated that the RhoA/MRTF‑A translocation pathway may promote mechanical overload‑induced fibrogenic activity in NP tissue and partially elucidated the molecular mechanisms underlying the occurrence of IVDD.

Deep Learning in Virtual Screening: Recent Applications and Developments

Drug discovery is a cost and time-intensive process that is often assisted by computational methods, such as virtual screening, to speed up and guide the design of new compounds. For many years, machine learning methods have been successfully applied in the context of computer-aided drug discovery. Recently, thanks to the rise of novel technologies as well as the increasing amount of available chemical and bioactivity data, deep learning has gained a tremendous impact in rational active compound discovery. Herein, recent applications and developments of machine learning, with a focus on deep learning, in virtual screening for active compound design are reviewed. This includes introducing different compound and protein encodings, deep learning techniques as well as frequently used bioactivity and benchmark data sets for model training and testing. Finally, the present state-of-the-art, including the current challenges and emerging problems, are examined and discussed.

Molecular Mechanisms of Leukocyte Migration and Its Potential Targeting-Lessons Learned From MKL1/SRF-Related Primary Immunodeficiency Diseases

Megakaryoblastic leukemia 1 (MKL1) deficiency is one of the most recently discovered primary immunodeficiencies (PIDs) caused by cytoskeletal abnormalities. These immunological “actinopathies” primarily affect hematopoietic cells, resulting in defects in both the innate immune system (phagocyte defects) and adaptive immune system (T-cell and B-cell defects). MKL1 is a transcriptional coactivator that operates together with serum response factor (SRF) to regulate gene transcription. The MKL/SRF pathway has been originally described to have important functions in actin regulation in cells. Recent results indicate that MKL1 also has very important roles in immune cells, and that MKL1 deficiency results in an immunodeficiency affecting the migration and function of primarily myeloid cells such as neutrophils. Interestingly, several actinopathies are caused by mutations in genes which are recognized MKL(1/2)-dependent SRF-target genes, namely ACTB, WIPF1, WDR1, and MSN. Here we summarize these and related (ARPC1B) actinopathies and their effects on immune cell function, especially focusing on their effects on leukocyte adhesion and migration. Furthermore, we summarize recent therapeutic efforts targeting the MKL/SRF pathway in disease.

Serum response factor-cofactor interactions and their implications in disease

Serum response factor (SRF), a member of the Mcm1, Agamous, Deficiens, and SRF (MADS) box transcription factor, is widely expressed in all cell types and plays a crucial role in the physiological function and development of diseases. SRF regulates its downstream genes by binding to their CArG DNA box by interacting with various cofactors. However, the underlying mechanisms are not fully understood, therefore attracting increasing research attention due to the importance of this topic. This review's objective is to discuss the new progress in the studies of the molecular mechanisms involved in the activation of SRF and its impacts in physiological and pathological conditions. Notably, we summarized the recent studies on the interaction of SRF with its two main types of cofactors belonging to the myocardin families of transcription factors and the members of the ternary complex factors. The knowledge of these mechanisms will create new opportunities for understanding the dynamics of many traits and disease pathogenesis especially, cardiovascular diseases and cancer that could serve as targets for pharmacological control and treatment of these diseases.

Rho-kinase (ROCK) Inhibitors - A Neuroprotective Therapeutic Paradigm with a Focus on Ocular Utility

BACKGROUND

Glaucoma is a progressive optic neuropathy causing visual impairment and Retinal Ganglionic Cells (RGCs) death gradually posing a need for neuroprotective strategies to minimize the loss of RGCs and visual field. It is recognized as a multifactorial disease, Intraocular Pressure (IOP) being the foremost risk factor. ROCK inhibitors have been probed for various possible indications, such as myocardial ischemia, hypertension, kidney diseases. Their role in neuroprotection and neuronal regeneration has been suggested to be of value in the treatment of neurological diseases, like spinal-cord injury, Alzheimer's disease and multiple sclerosis but recently Rho-associated Kinase inhibitors have been recognized as potential antiglaucoma agents.

EVIDENCE SYNTHESIS

Rho-Kinase is a serine/threonine kinase with a kinase domain which is constitutively active and is involved in the regulation of smooth muscle contraction and stress fibre formation. Two isoforms of Rho-Kinase, ROCK-I (ROCK β) and ROCK-II (ROCK α) have been identified. ROCK II plays a pathophysiological role in glaucoma and hence the inhibitors of ROCK may be beneficial to ameliorate the vision loss. These inhibitors decrease the intraocular pressure in the glaucomatous eye by increasing the aqueous humour outflow through the trabecular meshwork pathway. They also act as anti-scarring agents and hence prevent post-operative scarring after the glaucoma filtration surgery. Their major role involves axon regeneration by increasing the optic nerve blood flow which may be useful in treating the damaged optic neurons. These drugs act directly on the neurons in the central visual pathway, interrupting the RGC apoptosis and therefore serve as a novel pharmacological approach for glaucoma neuroprotection.

CONCLUSION

Based on the results of high-throughput screening, several Rho kinase inhibitors have been designed and developed comprising of diverse scaffolds exhibiting Rho kinase inhibitory activity from micromolar to subnanomolar ranges. This diversity in the scaffolds with inhibitory potential against the kinase and their SAR development will be intricated in the present review. Ripasudil is the only Rho kinase inhibitor marketed to date for the treatment of glaucoma. Another ROCK inhibitor AR-13324 has recently passed the clinical trials whereas AMA0076, K115, PG324, Y39983 and RKI-983 are still under trials. In view of this, a detailed and updated account of ROCK II inhibitors as the next generation therapeutic agents for glaucoma will be discussed in this review.

Mechanotransduction in Wound Healing and Fibrosis

Skin injury is a common occurrence and mechanical forces are known to significantly impact the biological processes of skin regeneration and wound healing. Immediately following the disruption of the skin, the process of wound healing begins, bringing together numerous cell types to collaborate in several sequential phases. These cells produce a multitude of molecules and initiate multiple signaling pathways that are associated with skin disorders and abnormal wound healing, including hypertrophic scars, keloids, and chronic wounds. Studies have shown that mechanical forces can alter the microenvironment of a healing wound, causing changes in cellular function, motility, and signaling. A better understanding of the mechanobiology of cells in the skin is essential in the development of efficacious therapeutics to reduce skin disorders, normalize abnormal wound healing, and minimize scar formation.

Evasion of apoptosis by myofibroblasts: a hallmark of fibrotic diseases

Organ fibrosis is a lethal outcome of autoimmune rheumatic diseases such as systemic sclerosis. Myofibroblasts are scar-forming cells that are ultimately responsible for the excessive synthesis, deposition and remodelling of extracellular matrix proteins in fibrosis. Advances have been made in our understanding of the mechanisms that keep myofibroblasts in an activated state and control myofibroblast functions. However, the mechanisms that help myofibroblasts to persist in fibrotic tissues remain poorly understood. Myofibroblasts evade apoptosis by activating molecular mechanisms in response to pro-survival biomechanical and growth factor signals from the fibrotic microenvironment, which can ultimately lead to the acquisition of a senescent phenotype. Growing evidence suggests that myofibroblasts and senescent myofibroblasts, rather than being resistant to apoptosis, are actually primed for apoptosis owing to concomitant activation of cell death signalling pathways; these cells are poised to apoptose when survival pathways are inhibited. This knowledge of apoptotic priming has paved the way for new therapies that trigger apoptosis in myofibroblasts by blocking pro-survival mechanisms, target senescent myofibroblast for apoptosis or promote the reprogramming of myofibroblasts into scar-resolving cells. These novel strategies are not only poised to prevent progressive tissue scarring, but also have the potential to reverse established fibrosis and to regenerate chronically injured tissues.

Aberrant mechanosensing in injured intervertebral discs as a result of boundary-constraint disruption and residual-strain loss

In fibrous tissues, pre-stressed boundary constraints at bone interfaces instil residual strain throughout the tissue, even when unloaded. For example, internal swelling pressures in the central nucleus pulposus of the intervertebral disc generate pre-strain in the outer annulus fibrosus. With injury and depressurization, these residual strains are lost. Here, we show that the loss of residual strains in the intervertebral disc alters the microenvironment and instigates aberrant tissue remodelling and the adoption of atypical cellular phenotypes. By using puncture surgery of the annulus fibrosus in rabbits, ex vivo puncture experiments, and electrospun nanofibrous scaffolds recapitulating evolving boundary constraints, we show that the loss of residual strain promotes short-term apoptosis and the emergence of a fibrotic phenotype, that local fibre organization and cellular contractility mediate this process, and that the aberrant cellular changes could be abrogated by targeting the cell-mechanosensing machinery with small molecules. Our findings indicate that injury to dense connective tissues under pre-strain alters boundary constraints and residual strain, leading to aberrant mechanosensing, which in turn promotes disease progression.

A Novel Rabbit Model for Benign Biliary Stricture Formation and the Effects of Medication Infusions on Stricture Formation

BACKGROUND

Benign biliary stricture (BBS) is highly refractory. Currently, there is no effective strategy for prevention of BBS recurrence. The aim of this study is to establish a novel BBS rabbit model and to investigate the efficacy of biliary infusion with anti-proliferative medications for treating BBS.

METHOD

A BBS model was established via surgical injury and biliary infection. The biliary infusion tube was inserted into the common bile duct via the stump of cystic duct after cholecystectomy. Biliary infusions with Rapamycin, Pirfenidone and Fasudil were performed daily during the 4 weeks following the surgery. The wall thickness and luminal area of the bile duct were assessed.

RESULTS

All rabbits formed BBS after surgery. The mortality rate was 13% (8/60) and tube withdrawal rate was 4% (2/48). The thickness of the bile duct wall was significantly reduced; whereas the luminal area of the bile duct was dramatically enlarged in the Rapamycin or the Pirfenidone treated group, compared to the saline treated group. Furthermore, the local treatment significantly decreased the levels of proliferation makers, including PCNA, Collagen I and fibrogenic mediators, including ACTA2 and TGF-beta.

CONCLUSION

We have established a novel animal model for BBS formation. We have further demonstrated that biliary infusion with Rapamycin or Pirfenidone limits the biliary strictures through inhibiting the proliferation of the bile duct wall in this model. This may represent a new avenue for preventing biliary restenosis.

Microcontact printing of polydopamine on thermally expandable hydrogels for controlled cell adhesion and delivery of geometrically defined microtissues

Scaffold-free harvest of microtissue with a defined structure has received a great deal of interest in cell-based assay and regenerative medicine. In this study, we developed thermally expandable hydrogels with spatially controlled cell adhesive patterns for rapid harvest of geometrically controlled microtissue. We patterned polydopamine (PD) on to the hydrogel via microcontact printing (μCP), in linear shapes with widths of 50, 100 and 200μm. The hydrogels facilitated formation of spatially controlled strip-like microtissue of human dermal fibroblasts (HDFBs). It was possible to harvest and translocate microtissues with controlled widths of 61.4±14.7, 104.3±15.6, and 186.6±22.3μm from the hydrogel to glass substrates by conformal contact upon expansion of the hydrogel in response to a temperature change from 37 to 4°C, preserving high viability, extracellular matrix, and junction proteins. Microtissues were readily translocated in vivo to the subcutaneous tissue of mouse. The microtissues were further utilized as a simple assay model for monitoring of contraction in response to ROCK1 inhibitor. Collectively, micro-sized patterning of PD on the thermally expandable hydrogels via μCP holds promise for the development of microtissue harvesting systems that can be employed to ex vivo tissue assay and cell-based therapy.

STATEMENT OF SIGNIFICANCE

Harvest of artificial tissue with controlled cellular arrangement independently from external materials has been widely studied in cell-based assay and regenerative medicine. In this study, we developed scaffold-free harvest system of microtissues with anisotropic arrangement and controlled width by exploiting thermally expandable hydrogels with cell-adhesive patterns of polydopamine formed by simple microcontact printing. Cultured strips of human dermal fibroblasts on the hydrogels were rapidly delivered to various targets ranging from flat coverglass to mice subcutaneous tissue by thermal expansion of the hydrogel at 4°C for 10min. These were further utilized as a drug screening model responding to ROCK1 inhibitor, which imply its versatile applicability.

Effects of the Rho-Kinase Inhibitor Y-27632 on Extraocular Muscle Surgery in Rabbits

Purpose

To evaluate the effect of the Rho-kinase inhibitor Y-27632 on postoperative inflammation and adhesion following extraocular muscle surgery in rabbits.

Methods

The superior rectus muscle reinsertion was performed on both eyes of 8 New Zealand white rabbits. After reinsertion, the rabbits received subconjunctival injections of the Rho-kinase inhibitor and saline on each eye. To assess acute and late inflammatory changes, Ki-67, CD11β+, and F4/80 were evaluated and the sites of muscle reattachment were evaluated for a postoperative adhesion score and histopathologically for collagen formation.

Results

F4/80 antibody expression was significantly different in the Rho-kinase inhibitor-injected group at both postoperative day 3 and week 4 (p = 0.038, 0.031). However, Ki-67 and CD11β+ were not different the between two groups. The difference in the SRM/conjunctiva adhesion score between the two groups was also significant (p = 0.034). Conclusion. Intraoperative subconjunctival injection of the Rho-kinase inhibitor may be effective for adjunctive management of inflammation and fibrosis in rabbit eyes following extraocular muscle surgery.

Establishment of in vitro model of corneal scar pathophysiology

Corneal scarring is the major source of permanent blindness worldwide. The complex pathophysiology of corneal scarring is not comprehensibly understood as it involves the interaction of a constellation of pro-fibrotic cytokines influencing several signaling pathways involved in corneal scar development. In the present study, an attempt has been made to generate a relatively simple in vitro corneal scar model using primary corneal keratocytes by exogenously providing an optimized dose of combination of cytokines (TGF-β1, IL-6, and IL-8) involved in scar formation in situ. Data obtained from gene and protein expression analysis depicted enhanced ECM production with discrete expression of myofibroblast specific markers. The protein-protein interactions associated these proteins to various pathways involved in wound healing, cellular migration, and cytoskeletal remodeling justifying high relevance to in vivo scar formation. Hence the developed model can be used to acquire understanding about corneal scar pathophysiology and thus might be useful for designing the treatment modalities and efficacies for controlling scar formation.

Intrahepatic upregulation of MRTF-A signaling contributes to increased hepatic vascular resistance in cirrhotic rats with portal hypertension

BACKGROUND

Portal hypertension in cirrhosis is mediated, in part, by increased intrahepatic resistance, reflecting massive structural changes associated with fibrosis and intrahepatic vasoconstriction. Activation of the Rho/MRTF/SRF signaling pathway is essential for the cellular regulatory network of fibrogenesis. The aim of this study was to investigate MRTF-A-mediated regulation of intrahepatic fibrogenesis in cirrhotic rats.

METHODS

Portal hypertension was induced in rats via an injection of CCl₄ oil. Hemodynamic measurements were obtained using a polyethylene PE-50 catheter and pressure transducers. Expression of hepatic fibrogenesis was measured using histological staining. Expression of protein was measured using western blotting.

RESULTS

Upregulation of MRTF-A protein expression in the livers of rats with CCl₄-induced cirrhosis was relevant to intrahepatic resistance and hepatic fibrogenesis in portal hypertensive rats with increased modeling time. Inhibition of MRTF-A by CCG-1423 decelerated hepatic fibrosis, decreased intrahepatic resistance and portal pressure, and alleviated portal hypertension.

CONCLUSION

Increased intrahepatic resistance in rats with CCl₄-induced portal hypertension is associated with an upregulation of MRTF-A signaling. Inhibition of this pathway in the liver can decrease hepatic fibrosis and intrahepatic resistance, as well as reduce portal pressure in cirrhotic rats with CCl₄-induced portal hypertension.

Fasudil inhibits proliferation and collagen synthesis and induces apoptosis of human fibroblasts derived from urethral scar via the Rho/ROCK signaling pathway

Fasudil has shown antifibrotic effects in various fibrotic diseases. However, its effects on human urethral fibroblasts are unknown. This study evaluated the effects of fasudil on cellular proliferation, migration, apoptosis, and collagen synthesis in human fibroblasts derived from urethral scar tissues. Human urethral scar fibroblasts were cultured by explant and incubated for 24 h or 48 h with fasudil (12.5, 25, 50 µmol/L) with or without transforming growth factor β1 (TGF-β1, 10 ng/mL), or left untreated (control). Cell proliferation and migration was determined by MTT assay and Transwell chambers, respectively. Apoptosis was measured by flow cytometry. Levels of α-smooth muscle actin (α-SMA), myosin light-chain phosphatase (MLCP), LIM domain kinase 1 (LIMK1), phospho-cofilin (p-cofilin), collagen I, and collagen III were determined by Western blot. Compared with the control group, TGF-β1 was associated with a significant increase in urethral fibroblast proliferation and migration, and α-SMA, MLCP, LIMK1, p-cofilin, collagen I, and collagen III levels. Compared with the control group, fasudil (with or without TGF-β1), significantly and negatively correlated, in a dose-dependent manner, with the proliferation and migration of urethral fibroblasts, as well as α-SMA, MLCP, LIMK1, p-cofilin, collagen I, and collagen III levels. Moreover, fasudil significantly induced apoptosis of fibroblasts induced by TGF-β1. Higher concentrations of fasudil (50 μmol/L) were associated with greater cell apoptosis without TGF-β1 stimulation compared with the normal control group. Fasudil, with or without TGF-β1 stimulation, may inhibit human urethral fibroblasts proliferation, migration, apoptosis, and collagen synthesis via the Rho/ROCK signaling pathway.

Myofibroblast repair mechanisms post-inflammatory response: a fibrotic perspective

INTRODUCTION

Fibrosis is a complex chronic disease characterized by a persistent repair response. Its pathogenesis is poorly understood but it is typically the result of chronic inflammation and maintained with the required activity of transforming growth factor-β (TGFβ) and extracellular matrix (ECM) tension, both of which drive fibroblasts to transition into a myofibroblast phenotype.

FINDINGS

As the effector cells of repair, myofibroblasts migrate to the site of injury to deposit excessive amounts of matrix proteins and stimulate high levels of contraction. Myofibroblast activity is a decisive factor in whether a tissue is properly repaired by controlled wound healing or rendered fibrotic by deregulated repair. Extensive studies have documented the various contributing factors to an abrogated repair response. Though these fibrotic factors are known, very little is understood about the opposing antifibrotic molecules that assist in a successful repair, such as prostaglandin E2 (PGE₂) and ECM retraction. The following review will discuss the general development of fibrosis through the transformation of myofibroblasts, focusing primarily on the prominent profibrotic pathways of TGFβ and ECM tension and antifibrotic pathways of PGE₂ and ECM retraction.

CONCLUSIONS

The idea is to understand the ways in which the cell, after an injury and inflammatory response, normally controls its repair mechanisms through its homeostatic regulators so as to mimic them therapeutically to control abnormal pathways.

Myofibroblasts

Myofibroblasts are activated in response to tissue injury with the primary task to repair lost or damaged extracellular matrix. Enhanced collagen secretion and subsequent contraction - scarring - are part of the normal wound healing response and crucial to restore tissue integrity. Due to myofibroblasts ability to repair but not regenerate, accumulation of scar tissue is always associated with reduced organ performance. This is a fair price to pay by the body for not falling apart. Whereas myofibroblasts typically vanish after successful repair, dysregulation of the normal repair process can lead to persistent myofibroblast activation, for instance by chronic inflammation or mechanical stress in the tissue. Excessive repair leads to the accumulation of stiff collagenous ECM contractures - fibrosis - with dramatic consequences for organ function. The clinical need to terminate detrimental myofibroblast activities has stimulated researchers to answer a number of essential questions: where do myofibroblasts come from, what are the factors leading to their activation, how do we discriminate myofibroblasts from other cells, what is the molecular basis for their contractile activity, and how can we stop or at least control them? This article reviews the current state of the myofibroblast literature by emphasizing their role in ocular repair and fibrosis. It appears that although the eye is quite an extraordinary organ, ocular myofibroblasts behave or misbehave just like their siblings in other organs.

Tissue Transglutaminase, Not Lysyl Oxidase, Dominates Early Calcium-Dependent Remodeling of Fibroblast-Populated Collagen Lattices

Cell-populated collagen gels have provided significant insight into the cellular contractile mechanisms and cell-matrix interactions that are necessary for compacting and remodeling extant matrix. Nevertheless, little research has been devoted towards determining how cells entrench these deformations that contribute to establishing a preferred mechanical state. To this end, we examined the roles of two covalent matrix cross-linkers, i.e. tissue transglutaminase and lysyl oxidase, during global remodeling of the free-floating fibroblast-populated collagen lattice. Inhibition of tissue transglutaminase resulted in a reduced rate of compaction compared to controls during early remodeling (up to 2 days). In contrast, inhibition of lysyl oxidase did not alter the early compaction of these lattices, but it reduced the compaction after 2 days of culture. Acute inhibition of different contractile mechanisms suggested further that calcium-dependent contractility may have dominated during the initial remodeling of the collagen lattice before giving way to calcium-independent contractility at later times. In summary, these findings suggest that early remodeling of the free-floating collagen lattice is facilitated by calcium-dependent cell contraction while entrenchment is dominated by a tissue transglutaminase-mediated cross-linking of the extant matrix. As remodeling continues, however, lysyl oxidase increases its contribution, perhaps by consolidating de novo collagen fibrils into fibers to continue the remodeling while the cells transition to a more sustained, calcium-independent contractility. These results promise to influence future tissue engineering studies as well as computational simulations aimed at understanding matrix remodeling in complex in vivo situations.

Quantitative phosphoproteomic analysis of signaling downstream of the prostaglandin e2/g-protein coupled receptor in human synovial fibroblasts: potential antifibrotic networks

The Prostaglandin E2 (PGE2) signaling mechanism within fibroblasts is of growing interest as it has been shown to prevent numerous fibrotic features of fibroblast activation with limited evidence of downstream pathways. To understand the mechanisms of fibroblasts producing tremendous amounts of PGE2 with autocrine effects, we apply a strategy of combining a wide-screening of PGE2-induced kinases with quantitative phosphoproteomics. Our large-scale proteomic approach identified a PKA signal transmitted through phosphorylation of its substrates harboring the R(R/X)X(S*/T*) motif. We documented 115 substrates, of which 72 had 89 sites with a 2.5-fold phosphorylation difference in PGE2-treated cells than in untreated cells, where approximately half of such sites were defined as being novel. They were compiled by networking software to focus on highlighted activities and to associate them with a functional readout of fibroblasts. The substrates were associated with a variety of cellular functions including cytoskeletal structures (migration/motility), regulators of G-protein coupled receptor function, protein kinases, and transcriptional/translational regulators. For the first time, we extended the PGE2 pathway into an elaborate network of interconnecting phosphoproteins, providing vital information to a once restricted signalosome. These data provide new insights into eicosanoid-initiated cell signaling with regards to the regulation of fibroblast activation and the identification of new targets for evidenced-based pharmacotherapy against fibrosis.

Novel Rho/MRTF/SRF inhibitors block matrix-stiffness and TGF-β-induced fibrogenesis in human colonic myofibroblasts

BACKGROUND

Ras homolog gene family, member A (RhoA)/Rho-associated coiled-coil forming protein kinase signaling is a key pathway in multiple types of solid organ fibrosis, including intestinal fibrosis. However, the pleiotropic effects of RhoA/Rho-associated coiled-coil forming protein kinase signaling have frustrated targeted drug discovery efforts. Recent recognition of the role of Rho-regulated gene transcription by serum response factor (SRF) and its transcriptional cofactor myocardin-related transcription factor A (MRTF-A) suggest a novel locus for pharmacological intervention.

METHODS

Because RhoA signaling is mediated by both physical and biochemical stimuli, we examined whether pharmacological inhibition of RhoA or the downstream transcription pathway of MRTF-A/SRF could block intestinal fibrogenesis in 2 in vitro models.

RESULTS

In this study, we demonstrate that inhibition of RhoA signaling blocks both matrix-stiffness and transforming growth factor beta-induced fibrogenesis in human colonic myofibroblasts. Repression of alpha-smooth muscle actin and collagen expression was associated with the inhibition of MRTF-A nuclear localization. CCG-1423, a first-generation Rho/MRTF/SRF pathway inhibitor, repressed fibrogenesis in both models, yet has unacceptable cytotoxicity. Novel second-generation inhibitors (CCG-100602 and CCG-203971) repressed both matrix-stiffness and transforming growth factor beta-mediated fibrogenesis as determined by protein and gene expression in a dose-dependent manner.

CONCLUSIONS

Targeting the Rho/MRTF/SRF mechanism with second-generation Rho/MRTF/SRF inhibitors may represent a novel approach to antifibrotic therapeutics.

Linking phenotype to kinase: identification of a novel benzoxaborole hinge-binding motif for kinase inhibition and development of high-potency rho kinase inhibitors

Benzoxaboroles are a novel class of drug-like compounds that have been rich sources of novel inhibitors for various enzymes and of new drugs. While examining benzoxaborole activity in phenotypic screens, our attention was attracted by the (aminomethylphenoxy)benzoxaborole family, which potently inhibited Toll-like receptor-stimulated cytokine secretion from leukocytes. After considering their structure-activity relationships and the central role of kinases in leukocyte biology, we performed a kinome-wide screen to investigate the members of the (aminomethylphenoxy)benzoxaborole family. This technique identified Rho-activated kinase (ROCK) as a target. We showed competitive behavior, with respect to ATP, and then determined the ROCK2-drug cocrystal structure. The drug occupies the ATP site in which the oxaborole moiety provides hydrogen bond donors and acceptors to the hinge, and the aminomethyl group interacts with the magnesium/ATP-interacting aspartic acid common to protein kinases. The series exhibits excellent selectivity against most of the kinome, with greater than 15-fold selectivity against the next best member of the AGC protein kinase subfamily. Medicinal chemistry efforts with structure-based design resulted in a compound with a Ki of 170 nM. Cellular studies revealed strong enzyme inhibition rank correlation with suppression of intracellular phosphorylation of a ROCK substrate. The biochemical potencies of these compounds also translated to functional activity, causing smooth muscle relaxation in rat aorta and guinea pig trachea. The series exhibited oral availability and one member reduced rat blood pressure, consistent with ROCK's role in smooth muscle contraction. Thus, the benzoxaborole moiety represents a novel hinge-binding kinase scaffold that may have potential for therapeutic use.

Rho-kinase inhibitors offer a new approach in the treatment of glaucoma

INTRODUCTION

Primary open-angle glaucoma (POAG) is a leading cause for worldwide blindness and is characterized by progressive optic nerve damage. The etiology of POAG is unknown, but elevated intraocular pressure (IOP) and advanced age have been identified as risk factors. IOP reduction is the only known treatment for glaucoma. Recently, drugs that inhibit rho-associated protein kinase (ROCK) have been studied in animals and people for their ability to lower IOP and potentially treat POAG. ROCK inhibitors lower IOP through a trabecular mechanism and may represent a new therapeutic paradigm for the treatment of POAG.

AREAS COVERED

Exploring the place that ROCK inhibitors may occupy in our treatment of POAG requires a thorough understanding of pathophysiology and treatment. This article summarizes current research on the incidence, proposed etiologies and mechanisms of action for this drug class. ROCK inhibitor research is presented and considered in light of the current standard of pharmacologic care.

EXPERT OPINION

ROCK inhibitors alter the cell shape and extracellular matrix (ECM) of the trabecular meshwork. Preclinical studies demonstrate that these drugs have the potential to become a new therapy for glaucoma. However, ROCK inhibitors can affect multiple cell types, and their utility can be proven only after clinical studies in patients.

The mechanical environment modulates intracellular calcium oscillation activities of myofibroblasts

Myofibroblast contraction is fundamental in the excessive tissue remodeling that is characteristic of fibrotic tissue contractures. Tissue remodeling during development of fibrosis leads to gradually increasing stiffness of the extracellular matrix. We propose that this increased stiffness positively feeds back on the contractile activities of myofibroblasts. We have previously shown that cycles of contraction directly correlate with periodic intracellular calcium oscillations in cultured myofibroblasts. We analyze cytosolic calcium dynamics using fluorescent calcium indicators to evaluate the possible impact of mechanical stress on myofibroblast contractile activity. To modulate extracellular mechanics, we seeded primary rat subcutaneous myofibroblasts on silicone substrates and into collagen gels of different elastic modulus. We modulated cell stress by cell growth on differently adhesive culture substrates, by restricting cell spreading area on micro-printed adhesive islands, and depolymerizing actin with Cytochalasin D. In general, calcium oscillation frequencies in myofibroblasts increased with increasing mechanical challenge. These results provide new insight on how changing mechanical conditions for myofibroblasts are encoded in calcium oscillations and possibly explain how reparative cells adapt their contractile behavior to the stresses occurring in normal and pathological tissue repair.

Strategies Demonstrating Efficacy in Reducing Wound Contraction In Vivo

SIGNIFICANCE

Scarring continues to present a significant clinical problem. Wound contraction leads to scarring and is mediated by myofibroblasts and contractile forces across the wound bed. Contracture formation can have a significant impact on the quality of life of the patient, particularly where function and appearance are affected.

RECENT ADVANCES

Novel tissue-engineered matrices, cell-based therapies, and medicinal therapeutics have shown significant reduction in wound contraction in in-vivo models, particularly at early time points. These have been accompanied in many cases by reduced numbers of myofibroblasts, and in some by increased angiogenesis and improved neodermal architecture.

CRITICAL ISSUES

There are no animal models that replicate all aspects of wound healing as seen in patients. Therefore, information obtained from in vivo studies should be assessed critically. Additional studies, in particular those that seek to elucidate the mechanisms by which novel therapies reduce contraction, are needed to gain sufficient confidence to move into clinical testing.

FUTURE DIRECTIONS

The use of knockout mouse models in particular has generated significant advances in knowledge of the mechanisms behind myofibroblast conversion and other factors involved in generating tension across the wound. Medicinal therapeutics and tissue-engineering approaches that seek to disrupt/alter these pathways hold much promise for future development and translation to clinical practice.

A Paradigm of Fibroblast Activation and Dermal Wound Contraction to Guide the Development of Therapies for Chronic Wounds and Pathologic Scars

SIGNIFICANCE

Delayed wound healing and pathologic scarring are abnormal processes that can be thought of as occurring on a wound healing continuum, where insufficient wound contraction leads to nonhealing wounds, and overexuberant wound contraction leads to scarring. Chronic nonhealing wounds, including diabetic foot wounds, decubitus ulcers, and venous stasis ulcers, affect millions of people annually in the United States and costs billions of dollars. Similarly, pathologic scaring affects more than 40 million Americans annually and also costs billions of dollars.

CRITICAL ISSUES

While there are multiple factors that contribute to chronic nonhealing wounds and pathologic scars, a derangement in wound contraction is common to both. In this article, we will present a paradigm of dermal wound contraction, derived from clinical observations and basic science evidence, which pertains to chronic nonhealing wounds and pathologic scars.

RECENT ADVANCES

We will review how select therapies currently under investigation and in development fit the paradigm.

FUTURE DIRECTIONS

The paradigm will facilitate translational research and enable the development of future innovative therapies.

Mechanical aspects of lung fibrosis: a spotlight on the myofibroblast

Contractile myofibroblasts are responsible for the irreversible alterations of the lung parenchyma that hallmark pulmonary fibrosis. In response to lung injury, a variety of different precursor cells can become activated to develop myofibroblast features, most notably formation of stress fibers and expression of α-smooth muscle actin. Starting as an acute and beneficial repair process, myofibroblast secretion of collagen and contraction frequently becomes excessive and persists. The result is accumulation of stiff scar tissue that obstructs and ultimately destroys lung function. In addition to being a consequence of myofibroblast activities, the stiffened tissue is also a major promoter of the myofibroblast. The mechanical properties of scarred lung and fibrotic foci promote myofibroblast contraction and differentiation. One essential element in this detrimental feed-forward loop is the mechanical activation of the profibrotic growth factor transforming growth factor-β1 from stores in the extracellular matrix. Interfering with myofibroblast contraction and integrin-mediated force transmission to latent transforming growth factor-β1 and matrix proteins are here presented as possible therapeutic strategies to halt fibrosis.

Soft tissue mechanotransduction in wound healing and fibrosis

Recent evidence suggests that mechanical forces can significantly impact the biologic response to injury. Integrated mechanical and chemical signaling networks have been discovered that enable physical cues to regulate disease processes such as pathologic scar formation. Distinct molecular mechanisms control how tensional forces influence wound healing and fibrosis. Conceptual frameworks to understand cutaneous repair have expanded beyond traditional cell-cytokine models to include dynamic interactions driven by mechanical force and the extracellular matrix. Strategies to manipulate these biomechanical signaling networks have tremendous therapeutic potential to reduce scar formation and promote skin regeneration.