Insulin eye drops improve corneal wound healing in STZ-induced diabetic mice by regulating corneal inflammation and neuropeptide release.

INTRODUCTION: In recent years, insulin eye drops have attracted increasing attention from researchers and ophthalmologists. The aim of this study was to investigate the efficacy and possible mechanism of action of insulin eye drops in diabetic mice with corneal wounds. METHODS: A type 1 diabetes model was induced, and a corneal epithelial injury model of 2.5 mm was established. We used corneal fluorescein staining, hematoxylin-eosin (H-E) staining and the Cochet-Bonnet esthesiometer to examine the process of wound healing. Subsequently, the expression levels of Ki-67, IL-1ß, ß3-tubulin and neuropeptides, including substance P (SP) and calcitonin gene-related peptide (CGRP), were examined at 72 h after corneal injury. RESULTS: Fluorescein staining demonstrated an acceleration of the recovery of corneal epithelial injury in diabetic mice compared with the saline treatment, which was further evidenced by the overexpression of Ki-67. Moreover, 72 h of insulin application attenuated the expression of inflammatory cytokines and neutrophil infiltration. Remarkably, the results demonstrated that topical insulin treatment enhanced the density of corneal epithelial nerves, as well as neuropeptide SP and CGRP release, in the healing cornea via immunofluorescence staining. CONCLUSIONS: Our results indicated that insulin eye drops may accelerate corneal wound healing and decrease inflammatory responses in diabetic mice by promoting nerve regeneration and increasing levels of neuropeptides SP and CGRP.

Association between dyslipidaemia and dry eye disease: a systematic review and meta-analysis.

PURPOSE: To report a systematic review and meta-analysis of the association between dry eye disease (DED) and dyslipidaemia. METHODS: PubMed, Embase, Web of Science and Cochrane Library were systematically searched from January 2000 to December 2021. We included observational studies to assess the correlation of DED with meibomian gland dysfunction and dyslipidaemia without any language restrictions. The pooled OR with 95% CI was calculated in Stata V.15. RESULTS: Of 6727 identified studies, 18 studies (21 databases) with a total of 2 663 126 patients were analysed in our meta-analysis. The results showed that DED risk was associated with dyslipidaemia (OR=1.53, 95% CI: 1.41 to 1.66, p=0.001), especially elevated total cholesterol levels (OR=1.57, 95% CI: 1.25 to 1.99, p<0.001), elevated low-density lipoprotein cholesterol levels (OR=1.13, 95% CI: 1.06 to 1.20, p<0.001) and high-density lipoprotein cholesterol levels (OR=1.06, 95% CI: 1.01 to 1.11, p<0.001), but not with serum triglyceride levels. Moreover, having a history of lipid-lowering drug use (OR=1.41, 95% CI: 1.19 to 1.67, p<0.001) was also found to be positively associated with DED risk. CONCLUSIONS: The findings suggested that dyslipidaemia and lipid-lowering drug use might be associated with an increased risk of DED. More evidence is needed to confirm the findings by prospective studies. PROSPERO REGISTRATION NUMBER: CRD42022296664.

The lack of correlation between symptoms and signs in patients with meibomian gland dysfunction: a secondary analysis of the multicenter, randomized controlled trial.

BACKGROUND: This study was performed to investigate the association between symptoms and signs in patients with meibomian gland dysfunction (MGD). METHODS: Data were obtained from 122 MGD patients who were recruited for intense pulsed light therapy from November 2017 to April 2018 and the severity of their symptoms and signs at baseline were observed and recorded. Spearman correlation analyses were performed to analyze the relationships between SPEED score and signs. Subjects were divided into different subgroups based on possible influencing factors, and the differences in symptoms and signs were compared between different subgroups. Then influencing factors were controlled by regression analysis to explore the relationship between symptoms and signs and the strong factors affecting symptoms and signs. RESULTS: Analysis of baseline data showed that SPEED scores were not correlated with TBUT, CFSS, MGYSS or any index of eyelid margin abnormality (p > 0.05). In addition, abnormalities of lid margins, including hyperemia, thickening, rounding, hyperkeratinization, and telangiectasia around orifices, were more likely to occur in older patients, menopausal patients, and patients living in northern China. Multiple linear regression analysis indicated that there was still no correlation between symptoms and signs (p > 0.05) after adjusting for influencing factors. Further analysis suggested that each influencing factor has different effects on symptoms and signs, among which menopause affects the SPEED score (R = -4.112, p = 0.025), and age and region have significant effects on eyelid margin abnormalities. CONCLUSIONS: In conclusion, the results demonstrated a poor correlation between symptoms and signs in MGD patients. Age, hormone, and a dry environment may influence the disease, which suggests that the severity of the disease needs to be comprehensively assessed.

Indirect Application of Intense Pulsed Light Induces Therapeutic Effects on Experimental Murine Meibomian Gland Dysfunction.

Purpose: To investigate the indirect effects of intense pulsed light (IPL) on morphological and pathological changes of the meibomian glands (MGs) in apolipoprotein E knockout (ApoE-/- ) mice and explore the underlying mechanisms. Methods: ApoE-/- mice were treated with or without IPL three times below the lower eyelids and MGs were not directly exposed to irradiation. The eyelids and ocular surface were observed under a stereoscope. The morphology of MGs was examined by photographing and hematoxylin and eosin staining. Lipid droplets in MGs were examined by Oil Red O staining. The ultrastructure of meibocytes and mitochondria was observed under transmission electron microscopy. The relative gene and protein expression in MGs of upper eyelids was determined by immunostaining, Western blot, and qRT-PCR. Results: Three IPL treatments decreased the toothpaste-like plugging of orifices and thickening and irregularity of the upper and lower eyelid margins in ApoE-/- mice. The morphology of some MGs improved after IPL treatments, accompanied by increased proliferation of acinar basal cells and decreased ductal keratinization. Furthermore, the accumulation of hyperchromatic lipid droplets in the acini increased, and the lipid droplets distributed in the cells around the acini were round and small. Compared with untreated ApoE-/- mice, oxidative stress and apoptosis were downregulated by IPL treatment, accompanied by the improvements in mitochondrial structure. Further research showed that IPL treatments reduced the levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-17A, IL-6 in MGs and inactivated nuclear factor kappa B (NF-κ B). Conclusion: Collectively, the results demonstrate that indirect effects of IPL can improve the structure and function of MGs and mitigate the progression of MGD, which may be related to the indirect effects of photobiomodulation.

The Role of Neutrophil Extracellular Traps in the Ocular System.

Purpose: Neutrophils remain at the top of congenital and adaptive immune systems. The past 20 years witnessed a steep rise in the interest in neutrophil extracellular traps (NETs), which are a novel type of anti-pathogen mechanism coordinated with neutrophils. However, accumulating data revealed that excessive NETs in the host were associated with exacerbated inflammation, thrombosis, and autoimmunity. Increasing evidence found the participation of NETs in the pathophysiological process of many infectious and sterile diseases in the ocular system. Therefore, we discussed the role of neutrophil extracellular traps in the ocular system in this review.Methods: Articles were searched on PubMed, Embase and Web of science up to December 2021.Results: In this review, we exhibited the protective role of neutrophils patrolling the ocular surface from invading pathogens and their contribution to exacerbated inflammation and thrombogenesis in some ocular diseases. We also discussed the physiological and pathological processes of NET generation to identify novel biomarkers and therapeutic targets to interrupt immoderate NET formation and alleviate NET-induced harmful effects.Conclusions: Neutrophils and NETs are quite important for immune responses in the ocular system, while their negative effects on ocular tissue should also be emphasized, which could serve as novel biomarkers and potential therapeutic targets.