Sneezing reflex is mediated by a peptidergic pathway from nose to brainstem.

Sneezing is a vital respiratory reflex frequently associated with allergic rhinitis and viral respiratory infections. However, its neural circuit remains largely unknown. A sneeze-evoking region was discovered in both cat and human brainstems, corresponding anatomically to the central recipient zone of nasal sensory neurons. Therefore, we hypothesized that a neuronal population postsynaptic to nasal sensory neurons mediates sneezing in this region. By screening major presynaptic neurotransmitters/neuropeptides released by nasal sensory neurons, we found that neuromedin B (NMB) peptide is essential for signaling sneezing. Ablation of NMB-sensitive postsynaptic neurons in the sneeze-evoking region or deficiency in NMB receptor abolished the sneezing reflex. Remarkably, NMB-sensitive neurons further project to the caudal ventral respiratory group (cVRG). Chemical activation of NMB-sensitive neurons elicits action potentials in cVRG neurons and leads to sneezing behavior. Our study delineates a peptidergic pathway mediating sneezing, providing molecular insights into the sneezing reflex arc.

Dry eye disease in mice activates adaptive corneal epithelial regeneration distinct from constitutive renewal in homeostasis.

Many epithelial compartments undergo constitutive renewal in homeostasis but activate unique regenerative responses following injury. The clear corneal epithelium is crucial for vision and is renewed from limbal stem cells (LSCs). Using single-cell RNA sequencing, we profiled the mouse corneal epithelium in homeostasis, aging, diabetes, and dry eye disease (DED), where tear deficiency predisposes the cornea to recurrent injury. In homeostasis, we capture the transcriptional states that accomplish continuous tissue turnover. We leverage our dataset to identify candidate genes and gene networks that characterize key stages across homeostatic renewal, including markers for LSCs. In aging and diabetes, there were only mild changes with <15 dysregulated genes. The constitutive cell types that accomplish homeostatic renewal were conserved in DED but were associated with activation of cell states that comprise "adaptive regeneration." We provide global markers that distinguish cell types in homeostatic renewal vs. adaptive regeneration and markers that specifically define DED-elicited proliferating and differentiating cell types. We validate that expression of SPARC, a marker of adaptive regeneration, is also induced in corneal epithelial wound healing and accelerates wound closure in a corneal epithelial cell scratch assay. Finally, we propose a classification system for LSC markers based on their expression fidelity in homeostasis and disease. This transcriptional dissection uncovers the dramatically altered transcriptional landscape of the corneal epithelium in DED, providing a framework and atlas for future study of these ocular surface stem cells in health and disease.

Identification of a Sjögren's syndrome susceptibility locus at OAS1 that influences isoform switching, protein expression, and responsiveness to type I interferons.

Sjögren's syndrome (SS) is a common, autoimmune exocrinopathy distinguished by keratoconjunctivitis sicca and xerostomia. Patients frequently develop serious complications including lymphoma, pulmonary dysfunction, neuropathy, vasculitis, and debilitating fatigue. Dysregulation of type I interferon (IFN) pathway is a prominent feature of SS and is correlated with increased autoantibody titers and disease severity. To identify genetic determinants of IFN pathway dysregulation in SS, we performed cis-expression quantitative trait locus (eQTL) analyses focusing on differentially expressed type I IFN-inducible transcripts identified through a transcriptome profiling study. Multiple cis-eQTLs were associated with transcript levels of 2'-5'-oligoadenylate synthetase 1 (OAS1) peaking at rs10774671 (PeQTL = 6.05 × 10-14). Association of rs10774671 with SS susceptibility was identified and confirmed through meta-analysis of two independent cohorts (Pmeta = 2.59 × 10-9; odds ratio = 0.75; 95% confidence interval = 0.66-0.86). The risk allele of rs10774671 shifts splicing of OAS1 from production of the p46 isoform to multiple alternative transcripts, including p42, p48, and p44. We found that the isoforms were differentially expressed within each genotype in controls and patients with and without autoantibodies. Furthermore, our results showed that the three alternatively spliced isoforms lacked translational response to type I IFN stimulation. The p48 and p44 isoforms also had impaired protein expression governed by the 3' end of the transcripts. The SS risk allele of rs10774671 has been shown by others to be associated with reduced OAS1 enzymatic activity and ability to clear viral infections, as well as reduced responsiveness to IFN treatment. Our results establish OAS1 as a risk locus for SS and support a potential role for defective viral clearance due to altered IFN response as a genetic pathophysiological basis of this complex autoimmune disease.

Klinefelter's syndrome (47,XXY) is in excess among men with Sjögren's syndrome.

Primary Sjögren's syndrome (pSS) has a strong female bias. We evaluated an X chromosome dose effect by analyzing 47,XXY (Klinefelter's syndrome, 1 in 500 live male births) among subjects with pSS. 47,XXY was determined by examination of fluorescence intensity of single nucleotide polymorphisms from the X and Y chromosomes. Among 136 pSS men there were 4 with 47,XXY. This was significantly different from healthy controls (1 of 1254 had 47,XXY, p=0.0012 by Fisher's exact test) as well men with rheumatoid arthritis (0 of 363 with 47,XXY), but not different compared to men with systemic lupus erythematosus (SLE) (4 of 136 versus 8 of 306, Fisher's exact test p=NS). These results are consistent with the hypothesis that the number of X chromosomes is critical for the female bias of pSS, a property that may be shared with SLE but not RA.

Infections after refractive surgery.

PURPOSE OF REVIEW: The purpose of the review is to provide a summary of the recent literature concerning infections after refractive surgery pertinent to each procedure category. RECENT FINDINGS: New data from a large retrospective study suggest that the incidence of post-laser assisted in-situ keratomileusis infectious keratitis is declining. Additionally, recent case studies have reported viral, fungal, and Acanthamoeba pathogens. Corneal collagen cross-linking is emerging as an alternative therapeutic option for early stage post-LASIK infectious keratitis. Postoperative bandage contact lens used in patients undergoing surface ablation procedures may confer a higher risk of infection because of greater colonization rates in those individuals, such as healthcare providers, with relatively high risk of exposure to potential pathogens. In the setting of post-penetrating keratoplasty astigmatism, femtosecond laser astigmatic keratotomy procedures pose a risk of infectious keratitis and even endophthalmitis. Lastly, recent case reports of endophthalmitis after refractive lens procedures highlight the importance of postoperative monitoring for this sight threatening, albeit rare, complication. SUMMARY: The risks and management of infections after surgical refractive procedures vary widely depending on the specific technique employed. As technology and treatment options continue to evolve with further research, we anticipate continued success in the management of postoperative infections after refractive surgery.

Intraoperative management of posterior capsular rupture.

PURPOSE OF REVIEW: Posterior capsular rupture (PCR) and vitreous loss are inevitable complications encountered in cataract surgery across all levels of surgical experience and in spite of technological advances to improve safety. Thus, cataract surgeons must always be prepared to practice safe and effective intraoperative management strategies for capsular rupture. RECENT FINDINGS: Novel approaches for lens fragment removal, vitrectomy, and lens implantation have expanded the available options for cataract surgery in the setting of an open posterior capsule. Intraoperative PCR management strategies should prioritize safety and strive to minimize vitreous traction, stabilize anterior chamber volume, maintain capsular and zonular integrity, and protect the corneal endothelium and other anterior segment structures. SUMMARY: With appropriate management of PCR and vitreous, surgeons may still deliver safe and satisfactory visual outcomes for modern cataract surgery.

SDPR expression in human trabecular meshwork and its potential role in racial disparities of glaucoma.

In order to identify how differential gene expression in the trabecular meshwork (TM) contributes to racial disparities of caveolar protein expression, TM dysfunction and development of primary open angle glaucoma (POAG), RNA sequencing was performed to compare TM tissue obtained from White and Black POAG surgical (trabeculectomy) specimens. Healthy donor TM tissue from White and Black donors was analyzed by PCR, qPCR, immunohistochemistry staining, and Western blot to evaluate SDPR (serum deprivation protein response; Cavin 2) and CAV1/CAV2 (Caveolin 1/Caveolin 2). Standard transmission electron microscopy (TEM) and immunogold labeled studies were performed. RNA sequencing demonstrated reduced SDPR expression in TM from Black vs White POAG patients' surgical specimens, with no significant expression differences in other caveolae-associated genes, confirmed by qPCR analysis. No racial differences in SDPR gene expression were noted in healthy donor tissue by PCR analysis, but there was greater expression as compared to specimens from patients with glaucoma. Analysis of SDPR protein expression confirmed specific expression in the TM regions, but not in adjacent tissues. TEM studies of TM specimens from healthy donors did not demonstrate any racial differences in caveolar morphology, but a significant reduction of caveolae with normal morphology and immuno-gold staining of SDPR were noted in glaucomatous TM as compared to TM from healthy donors. Linkage of SDPR expression levels in TM, POAG development, and caveolar ultrastructural morphology may provide the basis for a novel pathway of exploration of the pathologic mechanisms of glaucoma. Differential gene expression of SDPR in TM from Black vs White subjects with glaucoma may further our understanding of the important public health implications of the racial disparities of this blinding disease.

Meibomian gland stem/progenitor cells: The hunt for gland renewal.

Meibomian glands (MGs) secrete lipid (meibum) onto the ocular surface to form the outermost layer of the tear film. Proper meibum secretion is essential for stabilizing the tear film, reducing aqueous tear evaporation, and maintaining the homeostasis of the ocular surface. Atrophy of MG as occurs with aging, leads to reduction of meibum secretion, loss of ocular surface homeostasis and evaporative dry eye disease (EDED). Since MGs are holocrine glands, secretion of meibum requires continuous self-renewal of lipid-secreting acinar meibocytes by stem/progenitor cells, whose proliferative potential is dramatically reduced with age leading to MG atrophy and an age-related meibomian gland dysfunction (ARMGD). Understanding the cellular and molecular mechanisms regulating meibocyte stem/progenitor cell maintenance and renewal may provide novel approaches to regenerating MG and treating EDED. Towards that end, recent label retaining cell and lineage-tracing experiments as well as knock-out transgenic mouse studies have begun to identify the location and identities of meibocyte progenitor cells and potential growth and transcription factors that may regulate meibocyte renewal. In addition, recent reports have shown that ARMGD may be reversed by novel therapeutics in mice. Herein, we discuss our current understanding of meibocyte stem/progenitor cells and the hunt for gland renewal.

Repository Corticotropin Injection as an Alternative Treatment for Refractory Ocular Mucous Membrane Pemphigoid.

PURPOSE: The purpose of this study was to report the clinical course and outcome of patients with refractory ocular mucous membrane pemphigoid (MMP) treated by repository corticotropin injection (RCI). METHODS: Patients with biopsy-proven ocular MMP treated with RCI from 3 tertiary medical centers were evaluated. Medical records between January 2013 and January 2021 were reviewed and deidentified to retrieve relevant disease-related data. Primary outcome measures included conjunctival inflammatory activity, change in Foster clinical conjunctival scarring staging after RCI treatment, and the development of ocular and systemic complications. RESULTS: Included were 15 patients (10 women and 5 men; 36-95 yrs of age) with a mean follow-up of 4.5 years. Most of the patients (80%) had Foster stage 3 at presentation, and all patients had active MMP. Each patient had failed to respond to at least 1 immunomodulatory drug during the follow-up, and 9 (60%) patients had treatment failure of at least 2 other agents before the use of RCI. The mean duration of RCI treatment was 21 months (range, 3-54 mo). Foster stage did not change in any of the 15 patients at the last follow-up. Nine patients continued RCI therapy at the last follow-up, and in all of them, the disease activity of MMP was well controlled. No serious adverse events because of RCI were documented during the follow-up in any treated patient. CONCLUSIONS: RCI may serve as an alternative or an adjunctive treatment in patients with severe and refractory ocular MMP. Treatment with RCI seems to be safe and well-tolerated.

Acanthamoeba Keratitis, Pathology, Diagnosis and Treatment.

Acanthamoeba keratitis is an unusual corneal infection that is recently increasing in frequency and is often contracted by contact lens wearers, someone who experienced recent eye trauma, or someone exposed to contaminated waters. Acanthamoeba survive in air, soil, dust, and water. Therefore, eye trauma and poor contact lens hygiene practices lead to the entrapment of debris and thus infection. Acanthamoeba keratitis results in severe eye pain, inflammation, and defects of the epithelium and stroma that can potentially result in vision loss if not diagnosed early and treated promptly. The disease can be diagnosed using corneal scrape/biopsy, polymerase chain reactions, impression cytology, or in vivo confocal microscopy. Once diagnosed, it is usually treated with an antimicrobial combination therapy of biguanide and aromatic diadine eye drops for several months. Advanced stages of the disease result in vision loss and the need for corneal transplants. Avoiding the risk factors and diagnosing the disease early are the most effective ways to combat Acanthamoeba keratitis.

Corneal perforation in ocular graft-versus-host disease.

PURPOSE: Corneal perforation is a rare, vision-threatening complication of ocular graft-versus-host disease (GVHD) and is not well understood. Our objective was to examine the clinical disease course and histopathologic correlation in patients who progressed to this outcome. METHODS: This study is a retrospective case series from four academic centers in the United States. All patients received a hematopoietic stem cell transplant (HSCT) prior to developing ocular GVHD. Variables of interest included patient demographics, time interval between HSCT and ocular events, visual acuity throughout clinical course, corticosteroid and infection prophylaxis regimens at time of corneal perforation, medical/surgical interventions, and histopathology. RESULTS: Fourteen eyes from 14 patients were analyzed. Most patients were male (86%) and Caucasian (86%), and average age at time of hematopoietic stem cell transplant was 47 years. The mean interval between hematopoietic stem cell transplant and diagnosis of ocular graft-versus-host disease was 9.5 months, and between hematopoietic stem cell transplant and corneal perforation was 37 months. Initial best-corrected visual acuity was 20/40 or better in 9 eyes, and all eyes had moderate or poor visual outcomes despite aggressive management, including corneal gluing in all patients followed by keratoplasty in 8 patients. The mean follow-up after perforation was 34 months (range 2-140 months). Oral prednisone was used prior to perforation in 11 patients (79%). On histopathology, representative specimens in the acute phase demonstrated ulcerative keratitis with perforation but minimal inflammatory cells and no microorganisms, consistent with sterile corneal "melt" in the setting of immunosuppression; and in the healed phase, filling in of the perforation site with fibrous scar. CONCLUSIONS: In these patients, an extended time interval was identified between the diagnosis of ocular graft-versus-host disease and corneal perforation. This represents a critical window to potentially prevent this devastating outcome. Further study is required to identify those patients at greatest risk as well as to optimize prevention strategies.

Compositional Analysis of Extracellular Aggregates in the Eyes of Patients With Exfoliation Syndrome and Exfoliation Glaucoma.

Purpose: Exfoliation syndrome (XFS) is a condition characterized by the production of insoluble fibrillar aggregates (exfoliation material; XFM) in the eye and elsewhere. Many patients with XFS progress to exfoliation glaucoma (XFG), a significant cause of global blindness. We used quantitative mass spectrometry to analyze the composition of XFM in lens capsule specimens and in aqueous humor (AH) samples from patients with XFS, patients with XFG and unaffected individuals. Methods: Pieces of lens capsule and samples of AH were obtained with consent from patients undergoing cataract surgery. Tryptic digests of capsule or AH were analyzed by high-performance liquid chromatography-mass spectrometry and relative differences between samples were quantified using the tandem mass tag technique. The distribution of XFM on the capsular surface was visualized by SEM and super-resolution light microscopy. Results: A small set of proteins was consistently upregulated in capsule samples from patients with XFS and patients with XFG, including microfibril components fibrillin-1, latent transforming growth factor-ß-binding protein-2 and latent transforming growth factor-ß-binding protein-3. Lysyl oxidase-like 1, a cross-linking enzyme associated with XFS in genetic studies, was an abundant XFM constituent. Ligands of the transforming growth factor-ß superfamily were prominent, including LEFTY2, a protein best known for its role in establishing the embryonic body axis. Elevated levels of LEFTY2 were also detected in AH from patients with XFG, a finding confirmed subsequently by ELISA. Conclusions: This analysis verified the presence of suspected XFM proteins and identified novel components. Quantitative comparisons between patient samples revealed a consistent XFM proteome characterized by strong expression of fibrillin-1, lysyl oxidase-like-1, and LEFTY2. Elevated levels of LEFTY2 in the AH of patients with XFG may serve as a biomarker for the disease.

Histopathology and selective biomarker expression in human meibomian glands.

BACKGROUND/AIMS: Meibomian gland dysfunction (MGD) is the most common form of evaporative dry eye disease, but its pathogenesis is poorly understood. This study examined the histopathological features of meibomian gland (MG) tissue from cadaver donors to identify potential pathogenic processes that underlie MGD in humans. METHODS: Histological analyses was performed on the MGs in the tarsal plates dissected from four cadaver donors, two young and two old adults, including a 36-year-old female (36F) and three males aged 30, 63 and 64 years (30M, 63M and 64M). RESULTS: The MGs of 36F displayed normal anatomy and structure, whereas the MGs of 30M showed severe ductal obstruction with mild distortion. The obstruction was caused by increased cytokeratin levels in association with hyperproliferation, but not hyperkeratinisation. In two older males, moderate to severe MG atrophy was noted. Cell proliferation was significantly reduced in the MG acini of the two older donors as measured by Ki67 labelling index (6.0%±3.4% and 7.9%±2.8% in 63M and 64M, respectively) when compared with that of the two younger donors (23.2%±5.5% and 16.9%±4.8% in 30M and 36F, respectively) (p<0.001). The expression patterns of meibocyte differentiation biomarkers were similar in the older and younger donors. CONCLUSION: Our histopathological study, based on a small sample size, suggests potentially distinct pathogenic mechanisms in MGD. In the young male adult, hyperproliferation and aberrant differentiation of the central ductal epithelia may lead to the obstruction by overproduced cytokeratins. In contrast, in older adults, decreased cell proliferation in acinar basal epithelia could be a contributing factor leading to MG glandular atrophy.

A surgical skills assessment rubric for pterygium surgery.

PURPOSE: To introduce an assessment tool (rubric) for evaluating ophthalmology residents' competency in pterygium surgery. METHODS: A panel of experienced international surgeons collaborated and developed the rubric. After describing various stages of the procedure, the Dreyfus scale of skill acquisition was used for scoring each stage. After finalizing the rubric, two surgeons independently evaluated 20 masked pterygium surgery videos of 10 residents and scored the videos according to the rubric. The agreement between the scores of them was examined with the intra-class correlation coefficient test. RESULTS: This rubric divides pterygium surgery into 13 different stages and covers the two most common techniques of pterygium surgery; conjunctival autograft and amniotic membrane transplant. The rubric showed face and content validity. Overall, an intraclass correlation coefficient of 0.90 (95% confidence interval 0.76-0.96, P < 0.001) was achieved between the two surgeons. The residents scored significantly higher on surgeries performed later in their rotation compared to the earlier surgeries (4.32 ± 0.35 vs 3.96 ± 0.31, P = 0.006). Certain stages of pterygium surgery were more strongly correlated with the residents' past pterygium surgical experience. CONCLUSION: This study introduces an international rubric for assessing competency in pterygium surgery. In addition to face and content validity, this rubric shows high inter-rater reliability. This may be a useful tool for teaching and measuring competency in pterygium surgery.

Denaturation and solvent effect on the conformation and fibril formation of TGFBIp.

PURPOSE: Transforming growth factor beta-induced protein (TGFBIp) aggregates into the phenotypic amyloid fibrils and/or non-amyloid deposits in corneal dystrophies and other disorders. While significant progress has been made in molecular genetics to successfully establish the link between the missense mutations of TGFBI and TGFBIp-related corneal dystrophies, the underlying mechanism for the abnormal aggregation remains elusive due to the lack of insights into the conformational perturbations induced by mutations. In the present study, we examined the effects of denaturants and a co-solvent on recombinant TGFBIp, with a focus on protein conformational changes and amyloid fibril formation. METHODS: Recombinant TGFBIp was subjected to various spectroscopic studies, such as far-ultraviolet circular dichroism (far-UV CD), intrinsic tryptophan fluorescence and quenching, and 1-anilinonaphthalene-8-sulfonic acid (ANS) fluorescence, under various denaturing conditions (urea and guanidine hydrochloride [GndHCl], acidic pH, and trifluoroethanol [TFE, co-solvent]). A thioflavin T (ThT) fluorescence assay was used to determine the fibril formation of TGFBIp. In addition, a rabbit polyclonal antibody against the oligomer precursors that initiate the formation of amyloid fibrils was also used in dot blot experiments to detect the formation of prefibrillar precursors. RESULTS: The purified recombinant TGFBIp is in the folded state according to its intrinsic tryptophan fluorescence analyses. A single-step unfolding process was observed in the GndHCl denaturation experiment. Results from far-UV CD, intrinsic tryptophan fluorescence, and ANS fluorescence experiments showed that TFE exerted its solvent effects by initially unfolding and transforming TGFBIp to a beta-sheet-enriched conformer at 20%. When increased to 40%, TFE changed TGFBIp into a non-native alpha-helix conformer. Although GndHCl and TFE led to protein unfolding, enhanced fibril formation could only be observed in the presence of TFE and at acidic pH, according to the ThT fluorescence assays. The paradigmatic protofibrillar TGFBIp oligomers were also detected during the fibril formation by the dot blot experiment. CONCLUSIONS: Our results suggest that protein unfolding may serve as the prerequisite but is not sufficient for the fibrillogenesis. Other factors, such as the solvent used, fragmentation, or pH, may also be crucial for the formation of TGFBIp fibrils.

TRPV1 activity and substance P release are required for corneal cold nociception.

As a protective mechanism, the cornea is sensitive to noxious stimuli. Here, we show that in mice, a high proportion of corneal TRPM8+ cold-sensing fibers express the heat-sensitive TRPV1 channel. Despite its insensitivity to cold, TRPV1 enhances membrane potential changes and electrical firing of TRPM8+ neurons in response to cold stimulation. This elevated neuronal excitability leads to augmented ocular cold nociception in mice. In a model of dry eye disease, the expression of TRPV1 in TRPM8+ cold-sensing fibers is increased, and results in severe cold allodynia. Overexpression of TRPV1 in TRPM8+ sensory neurons leads to cold allodynia in both corneal and non-corneal tissues without affecting their thermal sensitivity. TRPV1-dependent neuronal sensitization facilitates the release of the neuropeptide substance P from TRPM8+ cold-sensing neurons to signal nociception in response to cold. Our study identifies a mechanism underlying corneal cold nociception and suggests a potential target for the treatment of ocular pain.

Reproducibility of Ocular Surface Staining in the Assessment of Sjögren Syndrome-Related Keratoconjunctivitis Sicca: Implications on Disease Classification.

OBJECTIVE: The objective of this study was to assess the performance and reproducibility of the two currently used ocular surface staining scores in the assessment of keratoconjunctivitis sicca in Sjögren syndrome (SS) research classification. METHODS: In a multidisciplinary clinic for the evaluation of sicca, we performed all tests for the American European Consensus Group (AECG) and the American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria, including the van Bijsterveld score (vBS) and the Ocular Staining Score (OSS), in 994 participants with SS or with non-SS sicca. We analyzed the concordance between the scores, the diagnostic accuracy and correlation with clinical variables, and interrater and intrasubject reproducibility. RESULTS: A total of 308 (31.1%) participants had a discordant vBS and OSS that was due to extra corneal staining points in the OSS. The presence of one or more of the additional points was highly predictive of SS classification (odds ratio = 3.66; P = 1.65 × 10e-20) and was associated with abnormal results of all measures of autoimmunity and glandular dysfunction. Receiver operating characteristic curves showed optimal cutoff values of four for the vBS (sensitivity = 0.62; specificity = 0.71; Youden's J = 0.33) and five for the OSS (sensitivity = 0.56; specificity = 0.75; Youden's J = 0.31). Notably, there was very poor consistency in interobserver mean scores and distributions (P < 0.0001) and in intrasubject scores after a median of 5.5 years (35% changed status of the ocular criterion). CONCLUSION: Ocular surface staining scores are useful for SS research classification; however, they are subject to significant interrater and intrasubject variability, which could result in changes in classification in 5%-10% of all subjects. These results highlight the need for objective and reproducible markers of disease that have thus far remained elusive for SS.