Immunophysical analysis of corneal neovascularization: mechanistic insights and implications for pharmacotherapy

Local and Systemic Injections of Human Cord Blood Myeloid-Derived Suppressor Cells to Prevent Graft Rejection in Corneal Transplantation

Myeloid-derived suppressor cells (MDSCs) are therapeutic agents to prevent graft rejection in organ transplants by modulating inflammation. Herein, the immunosuppressive effect of human cord blood MDSCs on corneal allograft models was confirmed. CB-MDSCs were locally (subconjuctival, 5 × 10⁵) or systemically (intravenous, 1 × 10⁶) injected twice on days 0 and 7. A corneal transplantation model was established using C57BL/6 and BALB/c mice, and corneal graft opacity was measured to evaluate graft rejection up to 6 weeks. Results showed that graft survival in the MDSCs groups increased compared to vehicle groups after 42 days. Systemic and local MDSC administration inhibited the maturation (MHC-II^hi CD11c+) of dendritic cells (DCs) and the differentiation of interferon γ+ CD4+ Th1 in draining lymph nodes (LNs). However, vehicle groups increased the infiltration of CD3+ T cells and F4/80+ macrophages and produced prominent neovascular and lymphatic vessels into the graft site with increased mRNA expression of VEGF-A/C and VEGFR-1/R-3. Local MDSCs administration showed prominent anti-angiogenic/anti-lymphangiogenic effects even at lower MDSCs doses. Thus, CB-MDSCs could relatively suppress the infiltration of pathological T cells/macrophages into the corneas and the migration of mature DCs into draining LNs Therefore, ocular and systemic MDSCs administration showed therapeutic potential for preventing corneal allograft rejection.

Collagen as a Biomaterial for Skin and Corneal Wound Healing

The cornea and the skin are two organs that form the outer barrier of the human body. When either is injured (e.g., from surgery, physical trauma, or chemical burns), wound healing is initiated to restore integrity. Many cells are activated during wound healing. In particular, fibroblasts that are stimulated often transition into repair fibroblasts or myofibroblasts that synthesize extracellular matrix (ECM) components into the wound area. Control of wound ECM deposition is critical, as a disorganized ECM can block restoration of function. One of the most abundant structural proteins in the mammalian ECM is collagen. Collagen type I is the main component in connective tissues. It can be readily obtained and purified, and short analogs have also been developed for tissue engineering applications, including modulating the wound healing response. This review discusses the effect of several current collagen implants on the stimulation of corneal and skin wound healing. These range from collagen sponges and hydrogels to films and membranes.

Lifting the Veil: Characteristics, Clinical Significance, and Application of β-2-Microglobulin as Biomarkers and Its Detection with Biosensors

Because β-2-microglobulin (β₂M) is a surface protein that is present on most nucleated cells, it plays a key role in the human immune system and the kidney glomeruli to regulate homeostasis. The primary clinical significance of β₂M is in dialysis-related amyloidosis, a complication of end-stage renal disease caused by a gradual accumulation of β₂M in the blood. Therefore, the function of β₂M in kidney-related diseases has been extensively studied to evaluate its glomerular and tubular functions. Because increased β₂M shedding due to rapid cell turnover may indicate other underlying medical conditions, the possibility to use β₂M as a versatile biomarker rose in prominence across multiple disciplines for various applications. Therefore, this work has reviewed the recent use of β₂M to detect various diseases and its progress as a biomarker. While the use of state-of-the-art β₂M detection requires sophisticated tools, high maintenance, and labor cost, this work also has reported the use of biosensor to quantify β₂M over the past decade. It is hoped that a portable and highly efficient β₂M biosensor device will soon be incorporated in point-of-care testing to provide safe, rapid, and reliable test results.

Novel immunotherapeutic effects of topically administered ripasudil (K-115) on corneal allograft survival

Corneal allograft survival is mediated by the variety of immunological reactions and wound healing process. Our aim was to explore the effects of topical administration of ripasudil, a selective Rho-associated coiled-coil protein kinase inhibitor, on corneal allograft survival. Ripasudil was administered to mice thrice a day after allogeneic corneal transplantation. Corneal graft survival, opacity, neovascularization, re-epithelization, immune cell infiltration, and mRNA levels of angiogenic and pro-inflammatory factors in the grafted cornea and draining lymph nodes (dLNs) were evaluated with slit-lamp microscopy, immunohistochemistry, flow cytometry, and polymerase chain reaction. Graft survival was significantly prolonged with lower graft opacity and neovascularization scores in 0.4% and 2.0% ripasudil-treated groups, and mRNA levels of angiogenic and pro-inflammatory factors in ripasudil-treated grafted corneas were reduced. Moreover, 0.4% and 2.0% ripasudil reduced CD45⁺-infiltrated leukocyte frequency, Cd11b and Cd11c mRNA levels, and the frequencies of mature dendritic cells, IFNγ-, and IL-17- producing CD4⁺T cells in the dLNs of recipients. Re-epithelization rate of the grafted cornea was significantly higher in the 0.4% and 2.0% ripasudil groups than in the control. Topically applied ripasudil prolonged graft survival by downregulating neovascularization and inflammation factors, while promoting corneal re-epithelization, suggesting that ripasudil may be useful for suppressing immunological rejection in corneal transplantation.

Variable Responses to Corneal Grafts: Insights from Immunology and Systems Biology

Corneal grafts interact with their hosts via complex immunobiological processes that sometimes lead to graft failure. Prediction of graft failure is often a tedious task due to the genetic and nongenetic heterogeneity of patients. As in other areas of medicine, a reliable prediction method would impact therapeutic decision-making in corneal transplantation. Valuable insights into the clinically observed heterogeneity of host responses to corneal grafts have emerged from multidisciplinary approaches, including genomics analyses, mechanical studies, immunobiology, and theoretical modeling. Here, we review the emerging concepts, tools, and new biomarkers that may allow for the prediction of graft survival.

Protective Effect of TLR4 Ablation against Corneal Neovascularization following Chemical Burn in a Mouse Model

PURPOSE

To determine whether Toll-like receptor 4 knockout protects mice from corneal neovascularization following chemical injury compared to wild-type (WT) mice.

METHODS

A chemical burn (75% silver nitrate, 25% potassium nitrate) was created under anesthesia in the central right cornea of 32 WT and 31 Toll-like receptor 4 knockout mice. Corneal neovascularization was evaluated at 3, 4, 6, 8, 10, and 35 days after injury using digital photography, fluorescein angiography, gelatin perfusion with fluorescence vascular imaging, immunofluorescence staining, and molecular analysis.

RESULTS

There was no significant between-group difference in relative corneal burn area at 10 days after injury (39.0 ± 2.4% vs. 38.8 ± 9.8%, respectively). Neovascularization was detected in all corneas in vivo and perfusion was detected by fluorescence vascular imaging, reaching maximum area on day 10. The relative area of neovascularization was significantly smaller in the knockout than the WT mice on days 6 (33.3 ± 4.2% vs. 46.8 ± 7.4%, respectively, p = 0.005) and 8 (36.6 ± 1.1% vs. 52.2 ± 6.4%, respectively, p = 0.027), although neovascularization was intensive in both groups. In line with the immunostaining findings of angiogenesis and inflammatory infiltration of damaged corneas, molecular analysis (performed on day 3) revealed elevated expression levels of angiogenesis-related genes (vascular endothelial growth factor, VEGFR2, VEGFR1) and inflammation-related genes (CD45 and TGFβ1) in the WT mice. The knockout mice had higher TNF-α expression than the WT mice.

CONCLUSION

In a mouse corneal chemical burn model, lack of Toll-like receptor 4 expression did not completely inhibit angiogenesis, but did have a relative effect to reduce neovascularization as compared to the WT.

Comparison of the inhibitory effect of different doses of subconjunctival bevacizumab application in an experimental model of corneal neovascularization

AIM

To evaluate the inhibitory effect of subconjunctival bevacizumab as single- and multiple-dose application, and compare their effects on corneal neovascularization in a rat model.

METHODS

Thirty adult Sprague-Dawley rats were used in this experimental study. The central cornea of the rats was cauterized chemically. The rats were randomly enrolled into three groups. All groups received subconjunctival injections. In Group 1 (control group, n=10), 0.05 mL 0.9% NaCl solution was injected on the first day. In Group 2 (single-dose group, n=10), 0.05 mL bevacizumab (1.25 mg) was injected on the first day. In Group 3 (multiple-dose group, n=10), four doses of 0.05 mL bevacizumab (1.25 mg) were injected on the first, third, fifth and seventh day. Slit-lamp examination of all rats was performed at the third and ninth day. Digital images of the corneas were taken and analyzed using image analysis software to calculate corneal neovascularization area. All rats were sacrificed on the tenth day. In corneal sections, the number of blood vessels, state of inflammation and collagen formation was evaluated histopathologically.

RESULTS

In Group 3, corneal edema grades were significantly lower than Group 1 and Group 2 (P=0.02, and P=0.035, respectively). The mean percentage of neovascularized corneal area in Group 3 was significantly lower than Group 2 (P=0.005). On histopathological examination, Group 2 and Group 3 showed significantly less number of blood vessels than Group 1 (P=0.005, and P=0.001, respectively). Additionally, Group 3 showed significantly less number of blood vessels compared to Group 2 (P=0.019). Inflammation and edema grades were significantly lower in Group 3 compared to Group 1 (P=0.001).

CONCLUSION

Subconjunctival bevacizumab injection is effective in inhibition of newly formed corneal neovascularization. The multiple-dose bevacizumab treatment seems to be more effective compared to single-dose treatment.