Maspin increases extracellular plasminogen activator activity associated with corneal fibroblasts and myofibroblasts

Immune-related keratitis is a rare complication associated with nivolumab treatment in a patient with advanced colorectal cancer: A case report

BACKGROUND

Immunotherapy has been widely used to treat Colorectal cancer but has also observe some immune-related adverse effects. With proper treatment, most irAE can be solved and the effect of immunotherapy will not be affected by temporary immunosuppression. However, there are few reports about corneal irAE, and the current understanding of irAE is incomplete. Here we report a metastatic colorectal cancer case of immune-related keratitis caused by nivolumab and to explore the occurrence of immune-related keratitis.

CASE DESCRIPTION

Here we report the case of a 49-year-old man with mCRC who had no previous ocular disease but developed immune-related ulcerative keratitis after treatment with nivolumab. We summarize a large amount of literature to discuss the mechanism of immune-related keratitis. In addition, we conclude a method that may be used to detect the occurrence of immune keratitis, by monitoring MMPs and maspin in patients treated with nivolumab. We believe immune-related keratitis may be a rare complication of nivolumab in the treatment of mCRC. The effect of simple anti-infective therapy and repair-promoting drugs was not obvious, but the effect of glucocorticoid combined with autologous serum was significant.

CONCLUSION

The mechanism of immune-related keratitis is that nivolumab destroys the immune microenvironment and ACAID, and affects corneal healing. Patients who use nivolumab can prevent immune keratitis by testing MMPs and maspin. The occurrence of immune keratitis may be a good indicator of the efficacy of ICI, and further study can be done in the follow-up.

Human SMILE-Derived Stromal Lenticule Scaffold for Regenerative Therapy: Review and Perspectives

A transparent cornea is paramount for vision. Corneal opacity is one of the leading causes of blindness. Although conventional corneal transplantation has been successful in recovering patients’ vision, the outcomes are challenged by a global lack of donor tissue availability. Bioengineered corneal tissues are gaining momentum as a new source for corneal wound healing and scar management. Extracellular matrix (ECM)-scaffold-based engineering offers a new perspective on corneal regenerative medicine. Ultrathin stromal laminar tissues obtained from lenticule-based refractive correction procedures, such as SMall Incision Lenticule Extraction (SMILE), are an accessible and novel source of collagen-rich ECM scaffolds with high mechanical strength, biocompatibility, and transparency. After customization (including decellularization), these lenticules can serve as an acellular scaffold niche to repopulate cells, including stromal keratocytes and stem cells, with functional phenotypes. The intrastromal transplantation of these cell/tissue composites can regenerate native-like corneal stromal tissue and restore corneal transparency. This review highlights the current status of ECM-scaffold-based engineering with cells, along with the development of drug and growth factor delivery systems, and elucidates the potential uses of stromal lenticule scaffolds in regenerative therapeutics.

The fibrinolytic system in the cornea: A key regulator of corneal wound healing and biological defense

The cornea is a relatively unique tissue in the body in that it possesses specific features such as a lack of blood vessels that contribute to its transparency. The cornea is supplied with soluble blood components such as albumin, globulin, and fibrinogen as well as with nutrients, oxygen, and bioactive substances by diffusion from aqueous humor and limbal vessels as well as a result of its exposure to tear fluid. The healthy cornea is largely devoid of cellular components of blood such as polymorphonuclear leukocytes, monocytes-macrophages, and platelets. The location of the cornea at the ocular surface renders it susceptible to external insults, and its avascular nature necessitates the operation of healing and defense mechanisms in a manner independent of a direct blood supply. The fibrinolytic system, which was first recognized for its role in the degradation of fibrin clots in the vasculature, has also been found to contribute to various biological processes outside of blood vessels. Fibrinolytic factors thus play an important role in biological defense of the cornea. In this review, we address the function of the fibrinolytic system in corneal defense including wound healing and the inflammatory response.

Thrombin alters the synthesis and processing of CYR61/CCN1 in human corneal stromal fibroblasts and myofibroblasts through multiple distinct mechanisms

Purpose

Previous research in our laboratory indicated that prothrombin and other coagulation enzymes required to activate prothrombin to thrombin are synthesized by the cornea and that apoptotic human corneal stromal cells can provide a surface for prothrombin activation through the intrinsic and extrinsic coagulation pathways. The purpose of the work reported here is to study the role of thrombin activity in the regulation of matricellular protein Cyr61 (CCN1) produced by wounded phenotype human corneal stromal fibroblasts and myofibroblasts.

Methods

Stromal cells from human donor corneas were converted to defined wounded phenotype fibroblasts and myofibroblasts with fetal bovine serum, followed by basic fibroblast growth factor (bFGF) and transforming growth factor beta-1 (TGFβ-1), respectively, and stimulated with varying concentrations (0-10.0 units (U)/ml) of thrombin from 1-7 h. Cyr61 transcript levels were determined using reverse transcriptase-PCR (RT-PCR) and quantitative PCR (qPCR) while protein forms were analyzed using western blot data. Protease activities were characterized via protease class-specific inhibitors and western blot analysis. Thrombin activity was quantified using the fluorogenic peptide Phe-Pro-Arg-AFC. Protease-activated receptor (PAR) agonist peptides-1 and -4 were used to determine whether cells increased Cyr61 through PAR signaling pathways. The PAR-1 antagonist SCH 79797 was used to block the thrombin cleavage of the receptor. PCR data were analyzed using MxPro software and western blot data were analyzed using Image Lab™ and Image J software. Student t test and one- and two-way ANOVA (with or without ranking, depending on sample distribution), together with Dunnett's test or Tukey comparison tests for post-hoc analysis, were used to determine statistical significance.

Results: Full-length Cyr61 is expressed by human corneal stromal fibroblasts and myofibroblasts and is significantly upregulated by active thrombin stimulation at the message (p<0.03) and protein (p<0.03) levels for fibroblasts and myofibroblasts. Inhibition by the allosteric thrombin-specific inhibitor hirudin prevented the thrombin-associated increase in the Cyr61 protein expression, indicating that the proteolytic activity of thrombin is required for the increase of the Cyr61 protein level. PAR-1 agonist stimulation of fibroblasts and myofibroblasts significantly increased cell-associated Cyr61 protein levels (p<0.04), and PAR-1 antagonist SCH 79797 significantly inhibited the thrombin stimulated increase of Cyr61 in fibroblasts but not in myofibroblasts. In the fibroblast and myofibroblast conditioned media, Cyr61 was detected as the full-length 40 kDa protein in the absence of thrombin, and mainly at 24 kDa in the presence of thrombin at ≥0.5 U/ml, using an antibody directed toward the internal linker region between the von Willebrand factor type C and thrombospondin type-1 domains. Although known to undergo alternative splicing, Cyr61 that is synthesized by corneal fibroblasts and myofibroblasts is not alternatively spliced in response to thrombin stimulation nor is Cyr61 directly cleaved by thrombin to generate its 24 kDa form; instead, Cyr61 is proteolytically processed into 24 kDa N- and 16 kDa C-terminal fragments by a thrombin activated leupeptin-sensitive protease present in conditioned media with activity distinct from the proteolytic activity of thrombin.

Conclusions

In cultured human corneal stromal fibroblasts and myofibroblasts, thrombin regulates Cyr61 through two mechanisms: 1) thrombin increases the Cyr61 expression at the message and protein levels, and 2) thrombin increases the activation of a leupeptin-sensitive protease that stimulates the cleavage of Cyr61 into N- and C-terminal domain populations in or near the thrombospondin type-1 domain. Generation of Cyr61 peptides during corneal injury stimulation may reveal additional functions of the protein, which modulate corneal wound healing activities or decrease activities of the full-length Cyr61 form.

Keratocyte biology

The study of corneal stromal keratocytes is motivated by its strong association with corneal health and visual function. They play a dominant role in the maintenance of corneal homeostasis and transparency through the production of collagens, proteoglycans and corneal crystallins. Trauma-induced apoptosis of keratocytes and replacement by fibroblasts and myofibroblasts disrupt the stromal matrix organization, resulting in corneal haze formation and vision loss. It is, therefore, important to understand the biology and behaviours of keratocytes and the associated stromal cell types (like fibroblasts, myofibroblasts, stromal stem cells) in wound healing, corneal pathologies (including keratoconus, keratitis, endothelial disorders) as well as different ophthalmic situations (such as collagen crosslinking/photodynamic treatment, keratoplasty and refractive surgery, and topical medications). The recent development of ex vivo propagation of keratocytes and stromal stem cells, and their translational applications, either via stromal injection or incorporated in bioscaffold, have been shown to restore the corneal transparency and regenerate native stromal tissue in animal models of corneal haze and other disorders.

Endothelial Microparticles are Associated to Pathogenesis of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by obliteration of alveolar architecture, resulting in declining lung function and ultimately death. Pathogenic mechanisms remain unclear but involve a concomitant accumulation of scar tissue together with myofibroblasts activation. Microparticles (MPs) have been investigated in several human lung diseases as possible pathogenic elements, prognosis markers and therapeutic targets. We postulated that levels and cellular origins of circulating MPs might serve as biomarkers in IPF patients and/or as active players of fibrogenesis. Flow cytometry analysis showed a higher level of Annexin-V positive endothelial and platelet MPs in 41 IPF patients compared to 22 healthy volunteers. Moreover, in IPF patients with a low diffusing capacity of the lung for carbon monoxide (DL_CO<40%), endothelial MPs (EMPs) were found significantly higher compared to those with DL_CO>40% (p = 0.02). We then used EMPs isolated from endothelial progenitor cells (ECFCs) extracted from IPF patients or controls to modulate normal human lung fibroblast (NHLF) properties. We showed that EMPs did not modify proliferation, collagen deposition and myofibroblast transdifferentiation. However, EMPs from IPF patients stimulated migration capacity of NHLF. We hypothesized that this effect could result from EMPs fibrinolytic properties and found indeed higher plasminogen activation potential in total circulating MPs and ECFCs derived MPs issued from IPF patients compared to those isolated from healthy controls MPs. Our study showed that IPF is associated with an increased level of EMPs in the most severe patients, highlighting an active process of endothelial activation in the latter. Endothelial microparticles might contribute to the lung fibroblast invasion mediated, at least in part, by a fibrinolytic activity.

The role of hepatocyte growth factor in corneal wound healing

Hepatocyte growth factor (HGF) is a glycoprotein produced by mesenchymal cells and operates as a key molecule for tissue generation and renewal. During corneal injury, HGF is primarily secreted by stromal fibroblasts and promotes epithelial wound healing in a paracrine manner. While this mesenchymal-epithelial interaction is well characterized in various organs and the cornea, the role of HGF in corneal stromal and endothelial wound healing is understudied. In addition, HGF has been shown to play an anti-fibrotic role by inhibiting myofibroblast generation and subsequent production of a disorganized extracellular matrix and tissue fibrosis. Therefore, HGF represents a potential therapeutic tool in numerous organs in which myofibroblasts are responsible for tissue scarring. Corneal fibrosis can be a devastating sequela of injury and can result in corneal opacification and retrocorneal membrane formation leading to severe vision loss. In this article, we concisely review the available literature regarding the role of HGF in corneal wound healing. We highlight the influence of HGF on cellular behaviors in each corneal layer. Additionally, we suggest the possibility that HGF may represent a therapeutic tool for interrupting dysregulated corneal repair processes to improve patient outcomes.

Mesenchymal stem cell therapy for retro-corneal membrane - A clinical challenge in full-thickness transplantation of biosynthetic corneal equivalents

Artificial corneas (keratoprostheses) and biosynthetic collagen-based corneal equivalents are surgical implants designed to ease the global burden of corneal blindness. However, keratoprostheses in many cases fail due to development of fibrous retro-corneal membranes (RCM). Fibrous membranes which develop in the anterior chamber after prosthesis implantation do so on a matrix of fibrin. This study investigated fibrin deposition and RCM formation after full-thickness collagen-based hydrogel implants and compared them with syngeneic and allogeneic corneal grafts in mice. Fibrin cleared from the anterior chamber within 14 days in both allo- and syn-grafts but, persisted in hydrogel implants and developed into dense retro-corneal membrane (RCM) which were heavily infiltrated by activated myofibroblasts. In contrast, the number of CD11b⁺ macrophages infiltrating the initial deposition of fibrin in the anterior chamber (AC) after hydrogel implantation was markedly reduced compared to syn- and allo-grafts. Inoculation of mesenchymal stem cells prior to collagen gel implant promoted clearance of gel-associated fibrin from the anterior chamber. We propose that a failure of macrophage-mediated clearance of fibrin may be the cause of RCM formation after collagen-based hydrogel implants and that mesenchymal stem cell therapy promotes clearance of fibrin and prevents RCM formation.

STATEMENT OF SIGNIFICANCE

The manuscript addresses the potential value of bone marrow-derived mesenchymal stem cell therapy for retro-corneal membrane (RCM) formation in full-thickness transplantation of biosynthetic corneal equivalents. This work reports the pathophysiological changes in the anterior chamber of the mouse eye following full-thickness recombinant human cross-linked collagen-based hydrogel implants in which persistent fibrin promotes the development of dense RCM. Furthermore, pre-treatment with mesenchymal stem cells reduces RCM formation and enhances corneal transparency.

Identification of novel peptide motifs in the serpin maspin that affect vascular smooth muscle cell function

Maspin is a non-inhibitory member of the serpin family that affects cell behaviours related to migration and survival. We have previously shown that peptides of the isolated G α-helix (G-helix) domain of maspin show bioactivity. Migration, invasion, adhesion and proliferation of vascular smooth muscle cells (VSMC) are important processes that contribute to the build-up of atherosclerotic plaques. Here we report the use of functional assays of these behaviours to investigate whether other maspin-derived peptides impact directly on VSMC; focusing on potential anti-atherogenic properties. We designed 18 new peptides from the structural moieties of maspin above ten amino acid residues in length and considered them beside the existing G-helix peptides. Of the novel peptides screened those with the sequences of maspin strand 4 and 5 of beta sheet B (S4B and S5B) reduced VSMC migration, invasion and proliferation, as well as increasing cell adhesion. A longer peptide combining these consecutive sequences showed a potentiation of responses, and a 7-mer contained all essential elements for functionality. This is the first time that these parts of maspin have been highlighted as having key roles affecting cell function. We present evidence for a mechanism whereby S4B and S5B act through ERK1/2 and AMP-activated protein kinase (AMPK) to influence VSMC responses.

TGF-β2 promotes RPE cell invasion into a collagen gel by mediating urokinase-type plasminogen activator (uPA) expression

Transforming growth factor-beta (TGF-β) is one of the main epithelial-mesenchymal transition (EMT)-inducing factors. In general, TGF-β-induced EMT promotes cell migration and invasion. TGF-β also acts as a potent regulator of pericellular proteolysis by regulating the expression and secretion of plasminogen activators. Urokinase-type plasminogen activator (uPA) is a serine protease that binds to its cell surface receptor (uPAR) with high affinity. uPA binding to uPAR stimulates uPAR's interaction with transmembrane proteins, such as integrins, to regulate cytoskeletal reorganization and cell migration, differentiation and proliferation. However, the influence of TGF-β and the uPA/uPAR system on EMT in retinal pigment epithelial (RPE) cells is still unclear. The purpose of this study was to determine the effect of TGF-β2, which is the predominant isoform in the retina, and the uPA/uPAR system on RPE cells. In this study, we first examined the effect of TGF-β2 and/or the inhibitor of uPA (u-PA-STOP(®)) on the proliferation of a human retinal pigment epithelial cell line (ARPE-19 cells). Treatment with TGF-β2 or u-PA-STOP(®) suppressed cell proliferation. Combination treatment of TGF-β2 and u-PA-STOP(®) enhanced cell growth suppression. Furthermore, western blot analysis, fibrin zymography and real-time reverse transcription PCR showed that that TGF-β2 induced EMT in ARPE-19 cells and that the expression of uPA and uPAR expression was up-regulated during EMT. The TGF-β inhibitor SB431542 suppressed TGF-β2-stimulated uPA expression and secretion but did not suppress uPAR expression. Furthermore, we seeded ARPE-19 cells onto Transwell chambers and allowed them to invade the collagen matrix in the presence of TGF-β2 alone or with TGF-β2 and u-PA-STOP(®). TGF-β2 treatment induced ARPE-19 cell invasion into the collagen gel. Treatment with a combination of TGF-β2 and the uPA inhibitor strongly inhibited ARPE-19 cell invasion compared with treatment with TGF-β2 alone. Furthermore, the interaction between uPA and ARPE-19 cells was analyzed using a surface plasmon biosensor system. The binding of uPA to ARPE-19 cells was observed. In addition, TGF-β2 significantly promoted the binding activity of uPA to ARPE-19 cells in a time-dependent or cell-number-dependent fashion. These results indicate that TGF-β-induced EMT-associated phenotype changes in ARPE-19 cells and the invasiveness of ARPE-19 cells into a collagen gel matrix are mediated, at least in part, by uPA.