Nicotinamide inhibits corneal endothelial mesenchymal transition and accelerates wound healing

Ocular inoculation of toad venom: toxic cataract and proteomic profiling

Purpose

To report a singular case of cataract caused by toad venom inoculation and to scrutinize the pathological mechanisms through proteomic sequencing of the lens specimen.

Methods

A young Chinese male presented with progressively deteriorating vision in his right eye subsequent to a history of toad venom inoculation. He was diagnosed with a toxic cataract, and underwent phacoemulsification cataract surgery. Anterior capsule, nucleus, and cortex specimens from the patient (designated as PT_CAP, PT_PHACO, and PT_CTX, respectively) and age-related cataract controls (C_CAP, C_PHACO, and C_CTX, respectively) were collected and subjected to 4D label-free quantitative proteomics.

Results

A multitude of differentially expressed proteins (DEPs) were identified in the patient's lens compared to those in the controls. Specifically, a total of 204 DEPs were identified in PT_CAP compared to C_CAP, with MYH6, MYL2, MYL3, STAT1, and ANK1 among the foremost regulated DEPs. The DEPs of PT_CAP were principally affiliated with functions including "transportation of small molecules," "regulation of metal ion transport," and "import into cell." A sum of 109 DEPs were delineated in PT_CTX compared to C_CTX, with TPM1 among the top-10 downregulated DEPs. Ninety-five DEPs were pinpointed in PT_PHACO compared to C_PHACO, with hexokinase among the top 10 downregulated DEPs. These proteins were ascertained to be linked with Na+/K+-ATPase activity.

Conclusion

This study introduced the first documented case of toxic cataract caused by toad venom inoculation. Proteomic sequencing indicated a correlation between cataract and alterations in Na+/K+-ATPase activity, providing insights for the clinical management of ocular toad venom inoculation in subsequent cases.

Verteporfin combined with ROCK inhibitor promotes the restoration of corneal endothelial cell dysfunction in rats

Corneal endothelial cells (CECs) dysfunction frequently results in a hazy, edematous cornea due to corneal endothelial decompensation and is a major cause of corneal blindness. Drug interventions provide a less invasive alternative to corneal transplantation surgery. However, endothelial-to-mesenchymal transition (EndMT) limits CECs function. Rho-kinase (ROCK) inhibitors, shown in numerous studies to be an adjunctive therapy for CECs dysfunction, cannot completely reverse pathological EndMT caused by inflammatory environmental damage. Verteporfin (VP) is an inhibitor of Yes-associated protein (YAP) and has significant inhibitory effects on cell fibrosis and mesenchymal transition. Here, we explored VP's utility in mitigating EndMT during ROCK inhibitors treatment of corneal endothelial dysfunction. We surgically constructed a rat model of CECs injury and studied VP and ROCK inhibitors' effects on EndMT, cell proliferation, and corneal edema using RNA-Seq sequencing, immunofluorescence, optical coherence tomography, and qPCR. The results indicated that YAP expression in human fetal CECs was higher than in adults and decreased with age in rats. Moreover, YAP expression in human CECs was negatively correlated with functional genes, such as AQP1 and ATP1A1. VP effectively reversed EndMT and accelerated corneal hydration regression. However, it inhibited CECs proliferation. We also confirmed that the optimal ratio of VP combined with Y-27632 (ROCK inhibitor) was 1:1, promoting CECs proliferation and reversing EndMT by down-regulating transcription factors downstream of TGF-β signaling, thereby increasing CECs functional and intercellular adhesion proteins. These combined effects promote corneal endothelial damage repair, providing a new treatment strategy.

SIRT1 Activation Suppresses Corneal Endothelial-Mesenchymal Transition via the TGF-β/Smad2/3 Pathway

Endothelial-mesenchymal transition (EnMT) is the transversion of endothelial cells to mesenchymal cells under certain physiological or pathological conditions. When EnMT occurs in the corneal endothelium, corneal endothelial cells (CECs) lose their normal function and thus cannot maintain corneal clarity. Studies have shown that the mechanism of EnMT in CECs involves the transforming growth factor-β (TGF-β) signaling pathway, and one of the important inhibitors of the TGF-β/Smad2/3 pathway is sirtuin-1 (SIRT1). In this study, we used a rat model of corneal endothelium injury and TGF-β1-treated human CECs to induce EnMT, aiming to explore whether SIRT1 activation inhibits corneal EnMT in vivo and in vitro. SIRT1 was activated and suppressed using resveratrol (RSV) and EX527, respectively. The endothelial markers and mesenchymal markers were measured by immunofluorescence and Western blot assays. Co-immunoprecipitation was used to detect the interaction between SIRT1 and Smad2/3. The results showed that after mechanical injury, the group treated with RSV-activated SIRT1 regained corneal transparency and recovered from edema faster than the control group. Moreover, RSV-activated SIRT1 downregulated the expression levels of alpha smooth muscle actin (α-SMA), vimentin, and Snail and upregulated the expression levels of E-cadherin and Na+/K+-ATPase both in vivo and in vitro, but these effects were reversed when SIRT1 was inhibited by EX527. SIRT1 also upregulated the expression levels of TGF-β receptor 1 and phosphorylated Smad2/3. The interaction between SIRT1 and Smad2/3 in vitro was confirmed by co-immunoprecipitation. Overall, our results indicate that SIRT1 activation inhibits corneal EnMT via the TGF-β/Smad2/3 pathway, which may be a potential therapeutic target for corneal endothelium dysfunction.

Nicotinamide promotes the differentiation of functional corneal endothelial cells from human embryonic stem cells

Corneal transplantation represents the primary therapeutic approach for managing corneal endothelial dysfunction, but corneal donors remain scarce. Anterior chamber cell injection emerges as a highly promising alternative strategy for corneal transplantation, with pluripotent stem cells (PSC) demonstrating considerable potential as an optimal cell source. Nevertheless, only a few studies have explored the differentiation of functional corneal endothelial-like cells originating from PSC. In this investigation, a chemical-defined protocol was successfully developed for the differentiation of functional corneal endothelial-like cells derived from human embryonic stem cells (hESC). The application of nicotinamide (NAM) exhibited a remarkable capability in suppressing the fibrotic phenotype, leading to the generation of more homogeneous and well-distinctive differentiated cells. Furthermore, NAM effectively suppressed the expression of genes implicated in endothelial cell migration and extracellular matrix synthesis. Notably, NAM also facilitated the upregulation of surface marker genes specific to functional corneal endothelial cells (CEC), including CD26 (-) CD44 (-∼+-) CD105 (-) CD133 (-) CD166 (+) CD200 (-). Moreover, in vitro functional assays were performed, revealing intact barrier properties and Na+/K+-ATP pump functionality in the differentiated cells treated with NAM. Consequently, our findings provide robust evidence supporting the capacity of NAM to enhance the differentiation of functional CEC originating from hESC, offering potential seed cells for therapeutic interventions of corneal endothelial dysfunction.

Cu-vitamin B3 donut-like MOFs incorporated into TEMPO-oxidized bacterial cellulose nanofibers for wound healing

In this study, a novel multifunctional nanocomposite wound dressing was developed, consisting of TEMPO-oxidized bacterial cellulose (TOBC) nanofibers functionalized with donut-like copper-based metal-organic frameworks (CuVB3 MOFs). These CuVB3 MOFs were constructed using copper nodes linked by vitamin B3 molecules, resulting in a copper nicotinate crystal structure as confirmed by X-ray diffraction. Electron microscopy confirmed the presence of donut-like microstructures with uniform element distribution in the synthesized MOFs. Through the incorporation of CuVB3 MOFs into the TOBC nanofibers, innovative TOBC-CuVB3 nanocomposites were created. Biocompatibility testing using the MTT assay demonstrated enhanced cell viability of over 115% for the TOBC-CuVB3 nanocomposite. Acridine Orange staining revealed a ratio of 88-92% live cells on the wound dressings. Furthermore, fibroblast cells cultured on TOBC-CuVB3 exhibited expanded morphologies with long filopodia. The agar diffusion method exhibited improved antibacterial activity against both Gram-positive and Gram-negative bacterial strains, correlating with increased CuVB3 concentration in the samples. In vitro cellular scratch assays demonstrated excellent wound healing potential, with a closure rate of over 98% for wounds treated with the TOBC-CuVB3 nanocomposite. These findings underscore the synergistic effects of copper, vitamin B3, and TOBC nanofibers in the wound healing process.

NAD+ metabolism and eye diseases: current status and future directions

Currently, there are no truly effective treatments for a variety of eye diseases, such as glaucoma, age-related macular degeneration (AMD), and inherited retinal degenerations (IRDs). These conditions have a significant impact on patients' quality of life and can be a burden on society. However, these diseases share a common pathological process of NAD+ metabolism disorders. They are either associated with genetically induced primary NAD+ synthase deficiency, decreased NAD+ levels due to aging, or enhanced NAD+ consuming enzyme activity during disease pathology. In this discussion, we explore the role of NAD+ metabolic disorders in the development of associated ocular diseases and the potential advantages and disadvantages of various methods to increase NAD+ levels. It is essential to carefully evaluate the possible adverse effects of these methods and conduct a more comprehensive and objective assessment of their function before considering their use.

Cell therapy in corneal endothelial disease

PURPOSE OF REVIEW

Endothelial keratoplasty is the current gold standard for treating corneal endothelial diseases, achieving excellent visual outcomes and rapid rehabilitation. There are, however, severe limitations to donor tissue supply and uneven access to surgical teams and facilities across the globe. Cell therapy is an exciting approach that has shown promising early results. Herein, we review the latest developments in cell therapy for corneal endothelial disease.

RECENT FINDINGS

We highlight the work of several groups that have reported successful functional outcomes of cell therapy in animal models, with the utilization of human embryonic stem cells, human-induced pluripotent stem cells and cadaveric human corneal endothelial cells (CECs) to generate populations of CECs for intracameral injection. The use of corneal endothelial progenitors, viability of cryopreserved cells and efficacy of simple noncultured cells, in treating corneal decompensation is of particular interest. Further additions to the collective understanding of CEC physiology, and the process of cultivating and administering effective cell therapy are reviewed as well.

SUMMARY

The latest developments in cell therapy for corneal endothelial disease are presented. The continuous growth in this field gives rise to the hope that a viable solution to the large numbers of corneal blind around the world will one day be reality.

CHIR99021 balance TGFβ1 induced human corneal endothelial-to-mesenchymal transition to favor corneal endothelial cell proliferation

Corneal endothelial cells (CECs) play a major role in the maintenance of stromal hydration via the barrier and pump function for clear vision. Adult CECs cannot regenerate after injury. CECs cultured in vitro can undergo mitosis but may undergo corneal endothelial-to-mesenchymal transition (EnMT) and lose their endothelial characteristics. In this study, we examined the effects of CHIR99021 on transforming growth factor beta-1(TGFβ1)-induced EnMT in human CECs (hCECs) lines. CHIR99021 kept hCECs in the hexagonal shape and could downregulate the EnMT markers alpha-smooth muscle actin (α-SMA) and fibronectin (FN1), meanwhile maintained the hCECs function markers Na+/K+-ATPase and zonula occludens-1 (ZO-1) at levels comparable to those in the normal control. Interestingly, we found that the combination of CHIR99021 and TGFβ1 at appropriate concentrations would significantly promote the proliferation and migration of hCECs. These effects may be related to the inhibition of RhoA or Rac1, as well as the activation of Wnt and Erk pathway, with a calcium homeostasis. Our findings indicate that CHIR99021 inhibit EnMT and that the combination of CHIR99021 and TGFβ1 may provide new ideas for corneal endothelial regeneration and wound healing.

Pathogenic Role of Endoplasmic Reticulum Stress in Diabetic Corneal Endothelial Dysfunction

Purpose

Progressive corneal edema and endothelial cell loss represent the major corneal complications observed in diabetic patients after intraocular surgery. However, the underlying pathogenesis and potential treatment remain incompletely understood.

Methods

We used streptozotocin-induced type 1 diabetic mice and db/db type 2 diabetic mice as diabetic animal models. These mice were treated with the endoplasmic reticulum (ER) stress agonist thapsigargin; 60-mmHg intraocular pressure (IOP) with the ER stress antagonist 4-phenylbutyric acid (4-PBA); mitochondria-targeted antioxidant SkQ1; or reactive oxygen species scavenger N-acetyl-l-cysteine (NAC). Corneal thickness and endothelial cell density were measured before and after treatment. Human corneal endothelial cells were treated with high glucose with or without 4-PBA. The expression of corneal endothelial- and ER stress–related genes was detected by western blot and immunofluorescence staining. Mitochondrial bioenergetics were measured with an Agilent Seahorse XFp Analyzer.

Results

In diabetic mice, the appearance of ER stress preceded morphological changes in the corneal endothelium. The persistent ER stress directly caused corneal edema and endothelial cell loss in normal mice. Pharmacological inhibition of ER stress was sufficient to mitigate corneal edema and endothelial cell loss in both diabetic mice after high IOP treatment. Mechanistically, inhibiting ER stress ameliorated the hyperglycemia-induced mitochondrial bioenergetic deficits and improved the barrier and pump functional recovery of the corneal endothelium. When compared with NAC, 4-PBA and SkQ1 exhibited better improvement of corneal edema and endothelial cell loss in diabetic mice.

Conclusions

Hyperglycemia-induced ER stress contributes to the dysfunction of diabetic corneal endothelium, and inhibiting ER stress may offer therapeutic potential by improving mitochondrial bioenergetics.

Long-term corneal recovery by simultaneous delivery of hPSC-derived corneal endothelial precursors and nicotinamide

Human pluripotent stem cells (hPSCs) hold great promise for the treatment of various human diseases. However, their therapeutic benefits and mechanisms for treating corneal endothelial dysfunction remain undefined. Here, we developed a therapeutic regimen consisting of the combination of hPSC-derived corneal endothelial precursors (CEPs) with nicotinamide (NAM) for effective treatment of corneal endothelial dysfunction. In rabbit and nonhuman primate models, intracameral injection of CEPs and NAM achieved long-term recovery of corneal clarity and thickness, similar with the therapeutic outcome of cultured human corneal endothelial cells (CECs). The transplanted human CEPs exhibited structural and functional integration with host resident CECs. However, the long-term recovery relied on the stimulation of endogenous endothelial regeneration in rabbits, but predominantly on the replacing function of transplanted cells during the 3-year follow-up in nonhuman primates, which resemble human corneal endothelium with limited regenerative capacity. Mechanistically, NAM ensured in vivo proper maturation of transplanted CEPs into functional CECs by preventing premature senescence and endothelial-mesenchymal transition within the TGF-β–enriched aqueous humor. Together, we provide compelling experimental evidence and mechanistic insights of simultaneous delivery of CEPs and NAM as a potential approach for treating corneal endothelial dysfunction.

Ex vivo expansion and characterization of human corneal endothelium for transplantation: a review

The corneal endothelium plays a key role in maintaining corneal transparency. Its dysfunction is currently treated with penetrating or lamellar keratoplasty. Advanced cell therapy methods seek to address the persistent global deficiency of donor corneas by enabling the renewal of the endothelial monolayer with tissue-engineered grafts. This review provides an overview of recently published literature on the preparation of endothelial grafts for transplantation derived from cadaveric corneas that have developed over the last decade (2010–2021). Factors such as the most suitable donor parameters, culture substrates and media, endothelial graft storage conditions, and transplantation methods are discussed. Despite efforts to utilize alternative cellular sources, such as induced pluripotent cells, cadaveric corneas appear to be the best source of cells for graft preparation to date. However, native endothelial cells have a limited natural proliferative capacity, and they often undergo rapid phenotype changes in ex vivo culture. This is the main reason why no culture protocol for a clinical-grade endothelial graft prepared from cadaveric corneas has been standardized so far. Currently, the most established ex vivo culture protocol involves the peel-and-digest method of cell isolation and cell culture by the dual media method, including the repeated alternation of high and low mitogenic conditions. Culture media are enriched by additional substances, such as signaling pathway (Rho-associated protein kinase, TGF-β, etc.) inhibitors, to stimulate proliferation and inhibit unwanted morphological changes, particularly the endothelial-to-mesenchymal transition. To date, this promising approach has led to the development of endothelial grafts for the first in-human clinical trial in Japan. In addition to the lack of a standard culture protocol, endothelial-specific markers are still missing to confirm the endothelial phenotype in a graft ready for clinical use. Because the corneal endothelium appears to comprise phenotypically heterogeneous populations of cells, the genomic and proteomic expression of recently proposed endothelial-specific markers, such as Cadherin-2, CD166, or SLC4A11, must be confirmed by additional studies. The preparation of endothelial grafts is still challenging today, but advances in tissue engineering and surgery over the past decade hold promise for the successful treatment of endothelial dysfunctions in more patients worldwide.

A promising field: regulating imbalance of EndMT in cardiovascular diseases

Endothelial-mesenchymal transition (EndMT) is widely involved in the occurrence and development of cardiovascular diseases. Although there is no direct evidence, it is very promising as an effective target for the treatment of these diseases. Endothelial cells need to respond to the complex cardiovascular environment through EndMT, but sustained stimuli will cause the imbalance of EndMT. Blocking the signal transduction promoting EndMT is an effective method to control the imbalance of EndMT. In particular, we also discussed the potential role of endothelial cell apoptosis and autophagy in regulating the imbalance of EndMT. In addition, promoting mesenchymal-endothelial transformation (MEndT) is also a method to control the imbalance of EndMT. However, targeting EndMT to treat cardiovascular disease still faces many challenges. By reviewing the research progress of EndMT, we have put forward some insights and translated them into challenges and opportunities for new treatment strategies for cardiovascular diseases.

Animal models of corneal endothelial dysfunction to facilitate development of novel therapies

Progressive corneal endothelial disease eventually leads to corneal edema and vision loss due to the limited regenerative capacity of the corneal endothelium in vivo and is a major indication for corneal transplantation. Despite the relatively high success rate of corneal transplantation, there remains a pressing global clinical need to identify improved therapeutic strategies to address this debilitating condition. To evaluate the safety and efficacy of novel therapeutics, there is a growing demand for pre-clinical animal models of corneal endothelial dysfunction. In this review, experimentally induced, spontaneously occurring and genetically modified animal models of corneal endothelial dysfunction are described to assist researchers in making informed decisions regarding the selection of the most appropriate animal models to meet their research goals.

Nicotinamide suppresses bevacizumab-induced epithelial-mesenchymal transition of ARPE-19 cells by attenuating oxidative stress

AIM

To investigate the effects of nicotinamide (NAM) on bevacizumab (BEV)-induced epithelial-mesenchymal transition (EMT) of human retinal pigment epithelial cells (ARPE-19) and the underling mechanisms.

METHODS

ARPE-19 cells were treated with BEV for 24, 48, and 72h, and the variation degrees of EMT-related markers (fibronectin, α-SMA, vimentin, and ZO-1) were assessed by Western blotting to select the optimal treatment time point which exhibited the most obvious changes of EMT-related markers for the subsequent experiments. Furthermore, NAM was added to the medium, the mRNA and protein levels of the EMT-related markers were then measured. The accumulation of reactive oxygen species (ROS) and H₂O₂ and the total antioxidant capacity (TAC) of the cells were also measured to evaluate the level of oxidative stress.

RESULTS

After being treated with BEV for 72h, the protein expression levels of EMT-related markers in ARPE-19 cells showed significant changes. Meanwhile the levels of ROS and H₂O₂ were obviously increased, and the TAC of ARPE-19 cells was decreased. Totally 72h was chosen to be the optimal treatment time point in subsequent experiments. Furthermore, NAM inhibited BEV-induced EMT by downregulating fibronectin, α-SMA, and vimentin and upregulating ZO-1, decreased the accumulation of ROS and H₂O₂, and enhanced TAC in BEV-treated ARPE-19 cells.

CONCLUSION

This study demonstrates that NAM suppressed BEV-induced EMT in ARPE-19 cells by attenuating oxidative stress. Hence, NAM may be a potential therapeutic agent for alleviating neovascular fibrosis of the ocular fundus after anti-vascular endothelial growth factor therapy.

Transplantation of human induced pluripotent stem cell-derived neural crest cells for corneal endothelial regeneration

BACKGROUND

The corneal endothelium maintains corneal hydration through the barrier and pump function, while its dysfunction may cause corneal edema and vision reduction. Considering its development from neural crest cells (NCCs), here we investigated the efficacy of the human induced pluripotent stem cell (hiPSC)-derived NCCs for corneal endothelial regeneration in rabbits.

METHODS

Directed differentiation of hiPSC-derived NCCs was achieved using the chemically defined medium containing GSK-3 inhibitor and TGF-β inhibitor. The differentiated cells were characterized by immunofluorescence staining, FACS analysis, and in vitro multi-lineage differentiation capacity. For in vivo functional evaluation, 1.0 × 106 hiPSC-derived NCCs or NIH-3 T3 fibroblasts (as control) combined with 100 μM Y-27632 were intracamerally injected into the anterior chamber of rabbits following removal of corneal endothelium. Rabbit corneal thickness and phenotype changes of the transplanted cells were examined at 7 and 14 days with handy pachymeter, dual-immunofluorescence staining, and quantitative RT-PCR.

RESULTS

The hiPSC-derived NCCs were differentiated homogenously through 7 days of induction and exhibited multi-lineage differentiation capacity into peripheral neurons, mesenchymal stem cells, and corneal keratocytes. After 7 days of intracameral injection in rabbit, the hiPSC-derived NCCs led to a gradual recovery of normal corneal thickness and clarity, when comparing to control rabbit with fibroblasts injection. However, the recovery efficacy after 14 days deteriorated and caused the reappearance of corneal edema. Mechanistically, the transplanted cells exhibited the impaired maturation, cellular senescence, and endothelial-mesenchymal transition (EnMT) after the early stage of the in vivo directional differentiation.

CONCLUSIONS

Transplantation of the hiPSC-derived NCCs rapidly restored rabbit corneal thickness and clarity. However, the long-term recovery efficacy was impaired by the improper maturation, senescence, and EnMT of the transplanted cells.

Multiple roles of FGF10 in the regulation of corneal endothelial wound healing

Corneal endothelial dysfunction usually induces corneal haze and oedema, which seriously affect visual function. The main therapeutic strategy for this condition is corneal transplantation, but the use of this strategy is limited by the shortage of healthy donor corneas. Compared with corneal transplantation, drug intervention is less invasive and more accessible; thus, finding an effective pharmaceutical alternative for cornea transplantation is critical for the treatment of corneal endothelial dysfunction. In this study, we established a rabbit scratch model to investigate the effect of fibroblast growth factor 10 (FGF10) on corneal endothelial wound healing. Results showed that FGF10 injection accelerated the recovery of corneal transparency and increased the protein expression levels of ZO1, Na⁺/K⁺-ATPase and AQP-1. Moreover, FGF10 significantly inhibited the expression levels of endothelial-to-mesenchymal transition proteins and reduced the expression levels of the proinflammatory factors IL-1β and TNF-α in the anterior chamber aqueous humour. FGF10 also enhanced the Na⁺/K⁺-ATPase activity by enhancing mitochondrial function as a result of its direct interaction with its conjugate receptor. Thus, FGF10 could be a new pharmaceutical preparation as treatment for corneal endothelial dysfunction.

Corneal endothelium tissue engineering: An evolution of signaling molecules, cells, and scaffolds toward 3D bioprinting and cell sheets

Cornea is an avascular and transparent tissue that focuses light on retina. Cornea is supported by the corneal-endothelial layer through regulation of hydration homeostasis. Restoring vision in patients afflicted with corneal endothelium dysfunction-mediated blindness most often requires corneal transplantation (CT), which faces considerable constrictions due to donor limitations. An emerging alternative to CT is corneal endothelium tissue engineering (CETE), which involves utilizing scaffold-based methods and scaffold-free strategies. The innovative scaffold-free method is cell sheet engineering, which typically generates cell layers surrounded by an intact extracellular matrix, exhibiting tunable release from the stimuli-responsive surface. In some studies, scaffold-based or scaffold-free technologies have been reported to achieve promising outcomes. However, yet some issues exist in translating CETE from bench to clinical practice. In this review, we compare different corneal endothelium regeneration methods and elaborate on the application of multiple cell types (stem cells, corneal endothelial cells, and endothelial precursors), signaling molecules (growth factors, cytokines, chemical compounds, and small RNAs), and natural and synthetic scaffolds for CETE. Furthermore, we discuss the importance of three-dimensional bioprinting strategies and simulation of Descemet's membrane by biomimetic topography. Finally, we dissected the recent advances, applications, and prospects of cell sheet engineering for CETE.

Laminin 511 Precoating Promotes the Functional Recovery of Transplanted Corneal Endothelial Cells

Corneal endothelial dysfunction is a major cause of corneal blindness and is mainly treated by corneal transplantation. However, the global shortage of donor cornea hampers its application. Intracameral injection of cultured primary corneal endothelial cells (CECs) was recently confirmed in clinical trials. However, abnormal adhesion of the grafted CECs affects the application of this strategy. In this study, we explored if laminin 511 (LN511) improves the therapeutic function of the intracameral CEC injection for corneal endothelial dysfunction. To mimic the late stage of corneal endothelial diseases, intense scraping was developed to remove CECs and extracellular matrix of the posterior Descemet's membrane (DM) without DM removal in rabbits. Then, Dulbecco's phosphate-buffered saline (DPBS) and LN511 were intracamerally injected as the control and intervention groups, respectively. We found that the injected LN511 could settle and form a coating on the posterior surface of DM. After CEC transplantation, corneal clarity of rabbits in the LN511 group was rapidly recovered within 7 days, whereas the corneal recovery took 14 days in the DPBS group. Corneal thickness of LN511 group decreased to 413.3 ± 20.8 μm 7 days after operation, which was significantly lower than 1086.3 ± 78.6 μm of DPBS group (p < 0.01). Moreover, for the grafted CECs, LN511 promoted the rapid adhesion, tight junction formation, and expression of Na⁺/K⁺-ATPase and ZO-1. In vitro analysis revealed that the functions of LN511 on the cultured human CECs mechanistically depended on the cell density and the nuclear-cytoplasmic translocation of the Yes-associated protein. Our study demonstrated that LN511 precoating promoted the adhesion of the transplanted CECs and enhanced the functional regeneration of the corneal endothelium. Thus, our data suggested that the strategy of LN511 precoating and CECs' intracameral injection could be a potential method for the therapy of corneal endothelial dysfunction. Impact statement Intracameral injection of cultured corneal endothelial cells (CECs) is a potential alternative therapy for corneal endothelial dysfunction and has been proven to be effective in clinical trials. However, abnormal adhesion of the grafted CECs affects its application. In this study, intense scraping was developed to remove CECs and extracellular matrix of the posterior Descemet's membrane (DM) without DM removal for the therapy of late stage of corneal endothelial diseases. Laminin 511 was intracamerally injected to form a coating, improve the posterior DM, enhance the adhesion of the grafted CECs, and promote the functional regeneration of CEC transplantation through Yes-associated protein signaling.

Dose- and Time-Dependent Cytotoxicity of Carteolol in Corneal Endothelial Cells and the Underlying Mechanisms

Carteolol is a non-selective β-adrenoceptor antagonist used for the treatment of glaucoma, and its abuse might be cytotoxic to the cornea. However, its cytotoxicity and underlying mechanisms need to be elucidated. Herein, we used an in vivo model of feline corneas and an in vitro model of human corneal endothelial cells (HCECs), respectively. In vivo results displayed that 2% carteolol (clinical dosage) could induce monolayer density decline and breaking away of feline corneal endothelial (FCE) cells. An in vitro model of HCECs that were treated dose-dependently (0.015625–2%) with carteolol for 2–28 h, resulted in morphological abnormalities, declining in cell viability and elevating plasma membrane (PM) permeability in a dose- and time- dependent manner. High-dose (0.5–2%) carteolol treatment induced necrotic characteristics with uneven distribution of chromatin, marginalization and dispersed DNA degradation, inactivated caspase-2/-8, and increased RIPK1, RIPK3, MLKL, and pMLKL expression. The results suggested that high-dose carteolol could induce necroptosis via the RIPK/MLKL pathway. While low-dose (0.015625–0.25%) carteolol induced apoptotic characteristics with chromatin condensation, typical intranucleosomal DNA laddering patterns, G₁ cell-cycle arrest, phosphatidylserine (PS) externalization, and apoptotic body formation in HCECs. Meanwhile, 0.25% carteolol treatment resulted in activated caspase-2, -3, -8, and -9, downregulation of Bcl-2 and Bcl-xL, upregulation of Bax and Bad, ΔΨm disruption, and release of cytoplasmic cytochrome c (Cyt.c) and AIF into the cytoplasm. These observations suggested that low-dose carteolol could induce apoptosis via a caspase activated and mitochondrial-dependent pathway. These results suggested that carteolol should be used carefully, as low as 0.015625% cartelol caused apoptotic cell death in HCECs in vitro.

NAD+ precursors protect corneal endothelial cells from UVB-induced apoptosis

Excessive exposure of the eye to ultraviolet B light (UVB) leads to corneal edema and opacification because of the apoptosis of the corneal endothelium. Our previous study found that nicotinamide (NIC), the precursor of nicotinamide adenine dinucleotide (NAD), could inhibit the endothelial-mesenchymal transition and accelerate healing the wound to the corneal endothelium in the rabbit. Here we hypothesize that NIC may possess the capacity to protect the cornea from UVB-induced endothelial apoptosis. Therefore, a mouse model and a cultured cell model were used to examine the effect of NAD⁺ precursors, including NIC, nicotinamide mononucleotide (NMN), and NAD, on the UVB-induced apoptosis of corneal endothelial cells (CECs). The results showed that UVB irradiation caused apparent corneal edema and cell apoptosis in mice, accompanied by reduced levels of NAD⁺ and its key biosynthesis enzyme, nicotinamide phosphoribosyltransferase (NAMPT), in the corneal endothelium. However, the subconjunctival injection of NIC, NMN, or NAD⁺ effectively prevented UVB-induced tissue damage and endothelial cell apoptosis in the mouse cornea. Moreover, pretreatment using NIC, NMN, and NAD⁺ increased the survival rate and inhibited the apoptosis of cultured human CECs irradiated by UVB. Mechanistically, pretreatment using nicotinamide (NIC) recovered the AKT activation level and decreased the BAX/BCL-2 ratio. In addition, the capacity of NIC to protect CECs was fully reversed in the presence of the AKT inhibitor LY294002. Therefore, we conclude that NAD⁺ precursors can effectively prevent the apoptosis of the corneal endothelium through reactivating AKT signaling; this represents a potential therapeutic approach for preventing UVB-induced corneal damage.

Ocular Hypotonia and Transient Decrease of Vision as a Consequence of Exposure to a Common Toad Poison

The common toad produces venom (bufotoxin) that is produced in the parotid gland of the toad as well as in the skin. This toxic compound is a potent inhibitor of Na⁺/K⁺-ATPase activity. Physiological effects of bufotoxin are similar to those of digitalis and cause increased heart rate and muscle contractions. Ocular toxicity was described. A 67-year-old female patient was admitted to the emergency service because of sudden vision loss and a burning sensation in both eyes after she had been exposed to the poison of a toad. Slit lamp examination showed conjunctival hyperaemia and signs of ocular hypotonia. Topical antibiotic treatment was administered, and after 24 hours, corneal oedema and ocular hypotonia were in remission. Inhibition of Na⁺/K⁺-ATPase is a well-known effect of the toad venom. Na⁺/K⁺-ATPase is a part of corneal endothelial cells, ciliary body, and iris, and its inhibition caused by exposure to bufadienolides induces corneal dysfunction, decreased vision, and ocular hypotonia. Effects of bufadienolides on the decrease of ocular pressure appear to be very strong, with quick action. This rarely described effect of the bufotoxin can be used as a basis for further research of toad venom and its pharmacological potential. Purpose. To present a case of a 67-year-old female patient who experienced a sudden decrease in vision after exposure to the poison from a common toad (Bufo bufo).