Pathogenesis and treatments of TGFBI corneal dystrophies

[The latest IC3D classification of corneal dystrophies-Overview and changes of the 3rd edition]

The International Committee on Classification of Corneal Dystrophies (IC3D) was founded in 2005 to address difficulties arising from the outdated nomenclature for corneal dystrophies (CD) and to correct misconceptions in the literature. For each of the 22 CDs, a separate template was created to represent the current clinical, pathological and genetic knowledge of the disease. In addition, each template contains representative clinical photographs as well as light and electron microscopic images and, if available, confocal microscopic and coherence tomographic images of the respective CD. After the first edition was published in 2008, the revised version followed in 2015. The third edition of the IC3D was published as open access in February 2024. The latest edition is intended to serve as a reference work in everyday clinical practice and facilitate the diagnosis of CD, which might sometimes be difficult. This article provides an overview of the diagnostic and treatment principles of CD and presents the IC3D and its changes over time.

Recurrence Characteristics on Optical Coherence Tomography and Treatments of Reis-Bücklers Corneal Dystrophy After Phototherapeutic Keratectomy or Penetrating Keratoplasty

PURPOSE

To evaluate the recurrence characteristics on optical coherence tomography and clinical outcomes after phototherapeutic keratectomy (PTK) or penetrating keratoplasty (PKP) in patients with Reis-Bücklers corneal dystrophy (RBCD).

DESIGN

Retrospective interventional case series.

METHODS

Seventeen patients with RBCD (31 eyes, including 6 surgery-naïve eyes and 25 surgical eyes) received 44 surgical interventions from 1996 through 2022. PTK or PKP was performed as the initial surgical procedure. Significant recurrence was determined when best spectacle-corrected visual acuity decreased at least 2 lines with increased opacity in the superficial cornea. Repeated PTK or PTK on the corneal graft (CG-PTK) was considered if patients could not endure poor vision due to significant recurrence. Recurrence depth and annual increase in thickness of the central cornea and subepithelial deposits were assessed by anterior segment optical coherence tomography.

RESULTS

The mean follow-up time was 12.8 ± 8.5 years (range, 2.0-25.5 years). The mean logMAR best spectacle-corrected visual acuity improved from 1.24 ± 0.48 preoperatively to 0.27 ± 0.09 postoperatively in the initial PTK group (13 eyes, P < .001), from 1.84 ± 0.69 to 0.40 ± 0.13 in the PKP group (12 eyes, P < .001), from 1.04 ± 0.46 to 0.30 ± 0.07 in the repeated PTK group (12 times in 7 eyes, P < .001), and from 1.29 ± 0.43 to 0.39 ± 0.11 in the CG-PTK group (7 times in 5 eyes, P = .001). The median significant recurrence time was 27 months (95% confidence interval 23.9-30.1), 96 months (84.1-107.9), 31 months (28.8-33.1), and 24 months (19.8-28.2), respectively (P < .001). The depth of superficial deposits located between the epithelium and the anterior stroma was approximately 115 µm (85-159 µm). The annual thickening of subepithelial deposits was 14 ± 2 µm after initial PTK, 7 ± 3 µm after PKP, 14 ± 3 µm after repeated PTK, and 30 ± 11 µm after CG-PTK, compared to 4 ± 2 µm in surgery-naïve eyes (P = .002, .515, .002, <.001). The thickness of the central cornea increased by 15 ± 2 µm, 7 ± 2 µm, 15 ± 3 µm, and 31 ± 10 µm per year in the 4 surgery groups, respectively, compared to 5 ± 2 µm in surgery-naïve eyes (P = .001, .469, .001, <.001).

CONCLUSIONS

Better visual acuity can be achieved after PTK than PKP for treatment of RBCD. The annual thickening of subepithelial deposits may approximate an increase in central corneal thickness. The superficial distribution of subepithelial deposits makes it feasible to perform repeated PTK, even on the corneal allograft, for recurrent RBCD.

Involvement of TGFBI-TAGLN axis in cancer stem cell property of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a significant healthcare burden globally. Previous research using single-cell transcriptome analysis identified TGFBI as a crucial marker for the partial-epithelial-mesenchymal transition (partial-EMT) program. However, the precise role of TGFBI in HNSCC progression remains unclear. Therefore, our study aimed to clarify the impact of TGFBI on the malignant behavior of HNSCC cells. Through RNA-sequencing data from the TCGA database, we validated that increased TGFBI expression correlates with a higher occurrence of lymph node metastasis and unfavorable prognosis in HNSCC cases. Functional experiments demonstrated that TGFBI overexpression enhances the ability of sphere formation, indicating stem-cell-like properties. Conversely, TGFBI depletion reduces sphere formation and suppresses the expression of cancer stem cell (CSC) markers. RNA-sequencing analysis of TGFBI-overexpressing and control HNSCC cells revealed TAGLN as a downstream effector mediating TGFBI-induced sphere formation. Remarkably, TAGLN depletion abolished TGFBI-induced sphere formation, while its overexpression rescued the suppressed sphere formation caused by TGFBI depletion. Moreover, elevated TAGLN expression showed correlations with the expression of TGFBI and partial-EMT-related genes in HNSCC cases. In conclusion, our findings suggest that TGFBI may promote CSC properties through the upregulation of TAGLN. These novel insights shed light on the involvement of the TGFBI-TAGLN axis in HNSCC progression and hold implications for the development of targeted therapies.

Comparison of Transcriptomic Analysis of the Conjunctiva in Glaucoma-Treated Eyes with Dry Eyes and Healthy Controls

Ocular surface disease (OSD) associated with topical glaucoma drugs is a common issue impacting treatment adherence. We aimed to identify conjunctival transcriptomic changes in glaucoma and dry eye patients, comparing them to healthy controls. Bulbar conjunctival specimens were collected via impression cytology from 33 patients treated for glaucoma, 9 patients with dry eye, and 14 healthy controls. RNA extraction and bulk RNA sequencing were performed, followed by bioinformatics analysis to detect gene dysregulation. Ingenuity pathways analysis (IPA) identified pathways and biological processes associated with these transcriptomic changes. Sequencing analysis revealed 200 modified genes in glaucoma patients compared to healthy individuals, 233 differentially expressed genes in dry eye patients versus controls, and 650 genes in treated versus dry eye samples. In glaucoma patients, 79% of altered pathways were related to host defense, while dry eye patients showed a 39% involvement of host response, 15% in cellular proliferation and integrity, and 16% of mitochondrial dysfunction. These findings were validated through qRT-PCR. Glaucoma patients showed an intensified conjunctival immune response as a potential cause of OSD, whereas in dry eye patients, in addition to the immune response, other mechanisms such as mitochondrial dysfunction or reduced cellular proliferation were observed.

A Novel Heterozygous TGFBI c.1613C>A Pathogenic Variant is Associated With Lattice Corneal Dystrophy in a Chinese Family

PURPOSE

To investigate the gene mutations and relationship of clinical manifestation in a Chinese family with familial lattice corneal dystrophy (LCD).

DESIGN

Single-family case-control study.

METHODS

A family with familial LCD was recruited for this study. A total of 10 affected and 13 healthy family members participated in this research. Clinical features were examined by slit-lamp examination and anterior segment optical coherence tomography (AS-OCT). Peripheral blood samples were collected from each participant, and genomic DNA was extracted. Whole-exome sequencing (WES) analysis was performed, and the pathogenic variants of LCD were identified using bioinformatics tools and confirmed by Sanger sequencing.

RESULTS

Slit-lamp examination revealed diffuse grayish-white punctate, linear, and "lattice-like" opacities in the corneal epithelium and superficial corneal stroma. AS-OCT revealed an irregularly shaped cornea. The corneal epithelium and anterior corneal stroma showed high-reflective deposits and bulges. The clinical appearance of the patients fit the pattern and features of autosomal dominant inheritance of LCD type I (LCD I). A novel pathogenic variant of exon 12 in TGFBI was found by WES analysis, in which cytosine at position 1613 was substituted by adenine (c.1613C>A), and the amino acid was changed from threonine to lysine (p.T538K). Mutated genes and proteins were predicted to be deleterious.

CONCLUSION

A novel heterozygous pathogenic variant (c.1613C>A) of TGFBI was identified in the Chinese family with LCD I.

The miR-183/96/182 cluster is a checkpoint for resident immune cells and shapes the cellular landscape of the cornea

PURPOSE

The conserved miR-183/96/182 cluster (miR-183C) regulates both corneal sensory innervation and corneal resident immune cells (CRICs). This study is to uncover its role in CRICs and in shaping the corneal cellular landscape at a single-cell (sc) level.

METHODS

Corneas of naïve, young adult [2 and 6 months old (mo)], female miR-183C knockout (KO) mice and wild-type (WT) littermates were harvested and dissociated into single cells. Dead cells were removed using a Dead Cell Removal kit. CD45+ CRICs were enriched by Magnetic Activated Cell Sorting (MACS). scRNA libraries were constructed and sequenced followed by comprehensive bioinformatic analyses.

RESULTS

The composition of major cell types of the cornea stays relatively stable in WT mice from 2 to 6 mo, however the compositions of subtypes of corneal cells shift with age. Inactivation of miR-183C disrupts the stability of the major cell-type composition and age-related transcriptomic shifts of subtypes of corneal cells. The diversity of CRICs is enhanced with age. Naïve mouse cornea contains previously-unrecognized resident fibrocytes and neutrophils. Resident macrophages (ResMφ) adopt cornea-specific function by expressing abundant extracellular matrix (ECM) and ECM organization-related genes. Naïve cornea is endowed with partially-differentiated proliferative ResMφ and contains microglia-like Mφ. Resident lymphocytes, including innate lymphoid cells (ILCs), NKT and γδT cells, are the major source of innate IL-17a. miR-183C limits the diversity and polarity of ResMφ.

CONCLUSION

miR-183C serves as a checkpoint for CRICs and imposes a global regulation of the cellular landscape of the cornea.

Mini-Review: Clinical Features and Management of Granular Corneal Dystrophy Type 2

Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant corneal stromal dystrophy that is caused by p.Arg124His mutation of transforming growth factor β induced (TGFBI) gene. It is characterized by well demarcated granular shaped opacities in central anterior stroma and as the disease progresses, extrusion of the deposits results in ocular pain due to corneal epithelial erosion. Also, diffuse corneal haze which appears late, causes decrease in visual acuity. The prevalence of GCD2 is high in East Asia including Korea. Homozygous patients show a severe phenotype from an early age, and the heterozygote phenotype varies among patients, depending on several types of compound heterozygous TGFBI mutations. In the initial stage, conservative treatments such as artificial tears, antibiotic eye drops, and bandage contact lenses are used to treat corneal erosion. Different surgical methods are used depending on the depth and extent of the stromal deposits. Phototherapeutic keratectomy removes anterior opacities and is advantageous in terms of its applicability and repeatability. For deeper lesions, deep anterior lamellar keratoplasty can be used as the endothelial layer is not always affected. Recurrence following these treatments are reported within a wide range of rates in different studies due to varying definition of recurrence and follow-up period. In patients who have undergone corneal laser vision-correction surgeries such as photorefractive keratectomy, LASEK, or LASIK including SMILE surgery, corneal opacity exacerbates rapidly with severe deterioration of visual acuity. Further investigations on new treatments of GCD2 are necessary.

A Novel 13q12 Microdeletion Associated with Familial Syndromic Corneal Opacification

Progressive corneal opacification can result from multiple etiologies, including corneal dystrophies or systemic and genetic diseases. We describe a novel syndrome featuring progressive epithelial and anterior stromal opacification in a brother and sister and their mildly affected father, with all three family members having sensorineural hearing loss and two also with tracheomalacia/laryngomalacia. All carried a 1.2 Mb deletion at chromosome 13q12.11, with no other noteworthy co-segregating variants identified on clinical exome or chromosomal microarray. RNAseq analysis from an affected corneal epithelial sample from the proband's brother revealed downregulation of XPO4, IFT88, ZDHHC20, LATS2, SAP18, and EEF1AKMT1 within the microdeletion interval, with no notable effect on the expression of nearby genes. Pathway analysis showed upregulation of collagen metabolism and extracellular matrix (ECM) formation/maintenance, with no significantly down-regulated pathways. Analysis of overlapping deletions/variants demonstrated that deleterious variants in XPO4 were found in patients with laryngomalacia and sensorineural hearing loss, with the latter phenotype also being a feature of variants in the partially overlapping DFNB1 locus, yet none of these had reported corneal phenotypes. Together, these data define a novel microdeletion-associated syndromic progressive corneal opacification and suggest that a combination of genes within the microdeletion may contribute to ECM dysregulation leading to pathogenesis.

Topical Losartan: Practical Guidance for Clinical Trials in the Prevention and Treatment of Corneal Scarring Fibrosis and Other Eye Diseases and Disorders

Losartan is an angiotensin II receptor blocker (ARB) that impedes transforming growth factor (TGF) beta signaling by inhibiting activation of signal transduction molecule extracellular signal-regulated kinase (ERK). Studies supported the efficacy of topical losartan in decreasing scarring fibrosis after rabbit Descemetorhexis, alkali burn, and photorefractive keratectomy injuries, and in case reports of humans with scarring fibrosis after surgical complications. Clinical studies are needed to explore the efficacy and safety of topical losartan in the prevention and treatment of corneal scarring fibrosis, and other eye diseases and disorders where TGF beta has a role in pathophysiology. These include scarring fibrosis associated with corneal trauma, chemical burns, infections, surgical complications, and persistent epithelial defects, as well as conjunctival fibrotic diseases, such as ocular cicatricial pemphigoid and Stevens-Johnson syndrome. Research is also needed to explore the efficacy and safety of topical losartan for hypothesized treatment of transforming growth factor beta-induced (TGFBI)-related corneal dystrophies (Reis-Bu¨cklers corneal dystrophy, lattice corneal dystrophy type 1, and granular corneal dystrophies type 1 and type 2) where deposited mutant protein expression is modulated by TGF beta. Investigations could also explore the efficacy and safety of topical losartan treatments to reduce conjunctival bleb scarring and shunt encapsulation following glaucoma surgical procedures. Losartan and sustained release drug delivery devices could be efficacious in treating intraocular fibrotic diseases. Dosing suggestions and precautions that should be considered in trials of losartan are detailed. Losartan, as an adjuvant to current treatments, has the potential to augment pharmacological therapeutics for many ocular diseases and disorders where TGF beta plays a central role in pathophysiology.

Release of frustration drives corneal amyloid disaggregation by brain chaperone

TGFBI-related corneal dystrophy (CD) is characterized by the accumulation of insoluble protein deposits in the corneal tissues, eventually leading to progressive corneal opacity. Here we show that ATP-independent amyloid-β chaperone L-PGDS can effectively disaggregate corneal amyloids in surgically excised human cornea of TGFBI-CD patients and release trapped amyloid hallmark proteins. Since the mechanism of amyloid disassembly by ATP-independent chaperones is unknown, we reconstructed atomic models of the amyloids self-assembled from TGFBIp-derived peptides and their complex with L-PGDS using cryo-EM and NMR. We show that L-PGDS specifically recognizes structurally frustrated regions in the amyloids and releases those frustrations. The released free energy increases the chaperone's binding affinity to amyloids, resulting in local restructuring and breakage of amyloids to protofibrils. Our mechanistic model provides insights into the alternative source of energy utilized by ATP-independent disaggregases and highlights the possibility of using these chaperones as treatment strategies for different types of amyloid-related diseases.

The application and progression of CRISPR/Cas9 technology in ophthalmological diseases

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease (Cas) system is an adaptive immune defence system that has gradually evolved in bacteria and archaea to combat invading viruses and exogenous DNA. Advances in technology have enabled researchers to enhance their understanding of the immune process in vivo and its potential for use in genome editing. Thus far, applications of CRISPR/Cas9 genome editing technology in ophthalmology have included gene therapy for corneal dystrophy, glaucoma, congenital cataract, Leber's congenital amaurosis, retinitis pigmentosa, Usher syndrome, fundus neovascular disease, proliferative vitreoretinopathy, retinoblastoma and other eye diseases. Additionally, the combination of CRISPR/Cas9 genome editing technology with adeno-associated virus vector and inducible pluripotent stem cells provides further therapeutic avenues for the treatment of eye diseases. Nonetheless, many challenges remain in the development of clinically feasible retinal genome editing therapy. This review discusses the development, as well as mechanism of CRISPR/Cas9 and its applications and challenges in gene therapy for eye diseases.

Combined Topography-Guided Trans-Epithelial PRK and PTK for Recalcitrant Recurrent Corneal Erosions in Lattice Corneal Distrophy

Purpose

To report morphologic and functional changes after topography-guided trans-epithelial photorefractive keratectomy (PRK) combined with phototherapeutic keratectomy (PTK) for recalcitrant recurrent corneal erosions in Lattice Corneal Dystrophy (LCD).

Methods

One case report.

Results

A 78-year-old man presented us with decreased visual acuity [20/100 in right eye (RE), and 20/400 in left eye (LE)], and redness with foreign body sensation in both eyes. Clinical examination revealed epithelial erosions, and linear stromal opacities involving the center of the cornea in both eyes, supporting the diagnosis of LCD. Several medical approaches including autologous serum, amniotic membrane extract, and nerve growth factor eye drops allowed a temporary improvement in symptoms. A single-step topography-guided trans-epithelial PRK combined with PTK (CIPTA^®2 software, iVis Technologies) was performed in both eyes. After surface ablation using PRK, PTK was performed using masking agents (1% hydroxy-methylcellulose) to smooth the ablated surface. Subsequently, 0.02% Mitomycin C was applied over the ablated surface. At the 3-month follow-up, a resolution of corneal erosions, and stromal opacities were observed in both eyes, with a visual improvement to 20/25 in the RE and 20/50 in the LE. Furthermore, spherical equivalent, keratometric astigmatism, and corneal morphological irregularity index improved.

Conclusion

Recalcitrant corneal erosions and stromal opacities in LCD may be successfully treated using combined topography-guided trans-epithelial PRK and PTK.

Autophagy in the normal and diseased cornea

The cornea and covering tear film are together the 'objective lens' of the eye through which 80% of light is refracted. Despite exposure to a physically harsh and at times infectious or toxic environment, transparency essential for sight is in most cases maintained. Such resiliency makes the avascular cornea a superb model for the exploration of autophagy in the regulation of homeostasis with relevancy to all organs. Nonetheless, missense mutations and inflammation respectively clog or apparently overwhelm autophagic flux to create dystrophies much like in neurodegenerative diseases or further exacerbate inflammation. Here there is opportunity to generate novel topical therapies towards the restoration of homeostasis with potential broad application.

Identification of the Potential Molecular Mechanism of TGFBI Gene in Persistent Atrial Fibrillation

Background

Transforming growth factor beta-induced protein (TGFBI, encoded by TGFBI gene), is an extracellular matrix protein, widely expressed in variety of tissues. It binds to collagens type I, II, and IV and plays important roles in the interactions of cell with cell, collagen, and matrix. It has been reported to be associated with myocardial fibrosis, and the latter is an important pathophysiologyical basis of atrial fibrillation (AF). However, the mechanism of TGFBI in AF remains unclear. We aimed to detect the potential mechanism of TGFBI in AF via bioinformatics analysis.

Methods

The microarray dataset of GSE115574 was examined to detect the genes coexpressed with TGFBI from 14 left atrial tissue samples of AF patients. TGFBI coexpression genes were then screened using the R package. Using online analytical tools, we determined the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, Gene Ontology (GO) annotation, and protein-protein interaction (PPI) network of TGFBI and its coexpression genes. The modules and hub genes of the PPI-network were then identified. Another dataset, GSE79768 was examined to verify the hub genes. DrugBank was used to detect the potential target drugs.

Results

In GSE115574 dataset, a total of 1818 coexpression genes (769 positive and 1049 negative) were identified, enriched in 120 biological processes (BP), 38 cellular components (CC), 36 molecular functions (MF), and 39 KEGG pathways. A PPI-network with average 12.2-degree nodes was constructed. The genes clustered in the top module constructed from this network mainly play a role in PI3K-Akt signaling pathway, viral myocarditis, inflammatory bowel disease, and platelet activation. CXCL12, C3, FN1, COL1A2, ACTB, VCAM1, and MMP2 were identified and finally verified as the hub genes, mainly enriched in pathways like leukocyte transendothelial migration, PI3K-Akt signaling pathway, viral myocarditis, rheumatoid arthritis, and platelet activation. Pegcetacoplan, ocriplasmin, and carvedilol were the potential target drugs.

Conclusions

We used microdataset to identify the potential functions and mechanisms of the TGFBI and its coexpression genes in AF patients. Our findings suggest that CXCL12, C3, FN1, COL1A2, ACTB, VCAM1, and MMP2 may be the hub genes.

Corneal irregularity and visual function using anterior segment optical coherence tomography in TGFBI corneal dystrophy

The purpose of this study was to evaluate corneal irregular astigmatism of patients with granular and lattice corneal dystrophy (GCD and LCD). 70 GCD, 35 LCD, and 81 control eyes were included. Anterior and posterior corneal topographic data obtained from anterior segment optical coherence tomography were expanded into four components via Fourier harmonic analysis. These components were compared with healthy eyes and the association between each component and best-corrected visual acuity (BCVA) was investigated. Anterior and posterior components increased in both GCD and LCD eyes. Anterior and posterior components of GCD2, anterior of LCD type 1 (LCD1), posterior of LCD type IIIA (LCD 3A), and type IV (LCD4) significantly increased. BCVA was significantly associated with anterior and posterior components in LCD eyes but not in GCD. The anterior components of LCD1, anterior and posterior of LCD3A, and posterior of LCD4 , were positively correlated with BCVA. As conclusions, in GCD eyes, anterior and posterior components differed from those of the control but BCVA was not significantly associated with them. In LCD eyes, the anterior and posterior components increased, and BCVA was significantly associated with the anterior and posterior components.

Contrast Sensitivity Changes after Phototherapeutic Keratectomy in Heterozygote Granular Corneal Dystrophy Type 2

Purpose: Contrast sensitivity, the ability to distinguish the relative difference in luminance of an object from its surrounding or adjacent objects, is a useful measure of visual function. In granular corneal dystrophy type 2 (GCD2), opacity of the corneal stroma causes deterioration in visual function. We compared the contrast sensitivity of GCD2 patients before and after phototherapeutic keratectomy (PTK) to evaluate the perioperative visual function in these patients.Methods: This study included 22 eyes of heterozygote GCD2 patients. The visual acuity and contrast sensitivity were measured before and after PTK. The contrast sensitivity was measured in mesopic and photopic background luminances, with glare (G) levels of 0-2 (G0, G1, and G2, respectively) and spatial frequencies at 1.5, 3, 6, 12, and 18 cycles per degree (cpd).Results: The contrast sensitivity increased after PTK at 1.5 and 3 cpd in mesopic and photopic conditions with G0-2 glare (p < 0.05). At 6 cpd, the contrast sensitivity increased in the mesopic condition with G1 glare, and in the photopic condition with G0-2 glare (p < 0.05). However, there was no change in contrast sensitivity at any glare level at 12 and 18 cpd after PTK.Conclusions: In GCD2 patients, the contrast sensitivity increased significantly after PTK. The vision of GCD2 patients, which is decreased due to corneal opacity, is improved after PTK.

De Novo L509P Mutation of the TGFBI Gene Associated with Slit-Lamp Findings of Lattice Corneal Dystrophy Type IIIA

Background: Mutations of the transforming growth factor-β-induced (TGFBI) gene produce various types of corneal dystrophy. Here, we report a novel de novo L509P mutation not located in a known hot spot of the transforming growth factor-β-induced (TGFBI) gene and its clinical phenotype, which resembles that of lattice corneal dystrophy type IIIA (LCD IIIA). Case presentation: A 36-year-old man (proband) visited our clinic due to decreased visual acuity with intermittent ocular irritation in conjunction with painful recurrent erosions in both eyes for 10 years. Molecular genetic analyses revealed a TGFBI L509P mutation (c.1526T>C) in the proband and one of his sons. Interestingly, neither TGFBI mutations nor corneal abnormalities were detected in either of the proband’s biological parents, indicating the occurrence of a de novo L509P mutation. Clinical examinations, including slit-lamp retro-illumination and Fourier-domain anterior segment optical coherence tomography (FD-OCT), revealed gray deposits in the anterior stroma and deeper refractile lines extending from limbus to limbus in both corneas of the proband, consistent with a diagnosis of LCD IIIA. Superficial diffuse haze and surface irregularity were observed in conjunction with corneal erosions and visual impairment, necessitating phototherapeutic keratectomy (PTK). A 60 μm PTK of the Bowman layer and anterior stroma of the proband’s left eye was performed following the removal of the epithelium in order to remove superficial corneal opacities. His BCVA improved from 20/400 to 20/50 at postoperative week 8 and was maintained for 45 months. Pinhole-corrected VA was 20/20 at the last visit, and corneal opacities had not recurred. Conclusions: An inheritable de novo mutation of L509P in the TGFBI gene can produce severe LCD IIIA, which can be successfully treated with OCT-guided PRK.

Genetic screening of TGFBI in Iranian patients with TGFBI-associated corneal dystrophies and a meta-analysis of global variation frequencies

PURPOSE

Transforming growth factor beta-induced (TGFBI)-associated corneal dystrophies (CDs) are a clinically heterogeneous group of CDs caused by mutations in the TGFBI gene. Nucleotide sequences encoding two arginine residues at positions 124 and 555 in TGFBI protein are mutation hotspots. We screened regions of TGFBI that include the hotspots in a cohort of Iranian patients with TGFBI-associated CDs. We also performed a meta-analysis for frequencies of all reported TGFBI mutations.

METHODS

Twenty-four TGFBI-associated CD-diagnosed patients were recruited. Exons 4 and 12 of TGFBI were amplified by the polymerase chain reaction and sequenced by Sanger protocol. A meta-analysis on reported TGFBI sequence data was done by reviewing all published relevant articles available in NCBI.

RESULTS

Twenty-two out of 24 patients had mutations in exons 4 or 12 of TGFBI. The most frequent mutations were p.Arg124Cys, p.Arg124His, and p.Arg555Trp; each of these was found in six families. Three other missense mutations including p.Arg555Gln, p.Ile522Asn, and p.Ala546Thr were also identified. The data suggested a fairly tight genotype/phenotype correlation for the most common CDs. Literature review evidenced that the reported mutations affected less than 30% of the amino acids of the TGFBI protein and that p.Arg124His, p.Arg124Cys, p.Arg555Trp, p.Arg124Leu, p.Arg555Gln, and p.His626Arg were the most frequent mutations.

CONCLUSION

TGFBI mutation profile of Iranian patients is very similar to that of the rest of the world. The meta-analysis confirmed the worldwide prevalence of p.Arg124 and p.Arg555, showed that p.His626Arg is also relatively frequent, and evidenced the value of screening exons 4 and 12 of TGFBI.

Mutation effects on FAS1 domain 4 based on structure and solubility

Mutations in the fasciclin 1 domain 4 (FAS1-4) of transforming growth factor β-induced protein (TGFBIp) are associated with insoluble extracellular deposits and corneal dystrophies (CDs). The decrease in solubility upon mutation has been implicated in CD; however, the exact molecular mechanisms are not well understood. Here, we performed molecular dynamics simulations followed by solvation thermodynamic analyses of the FAS1-4 domain and its three mutants-R555W, R555Q, and A546T-linked to granular corneal dystrophy type 1, Thiel-Behnke corneal dystrophy and lattice corneal dystrophy, respectively. We found that both R555W and R555Q mutants have less affinity toward solvent water relative to the wild-type protein. In the R555W mutant, a remarkable increase in solvation free energy was observed because of the structural changes near the mutation site. The mutation site W555 is buried in other hydrophobic residues, and R557 simultaneously forms salt bridges with E554 and D561. In the R555Q mutant, the increase in solvation free energy is caused by structural rearrangements far from the mutation site. R558 separately forms salt bridges with D575, E576, and E598. Thus, we thus identified the relationship between the decrease in solubility and conformational changes caused by mutations, which may be useful in designing potential therapeutics and in blocking FAS1 aggregation related to CD.

Molecular mechanisms of amyloid disaggregation

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Importance of disaggregation mechanism and innate disaggregation in living systems.

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Different types and mechanism of disaggregation reported in literature.

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Structural details of the interactions and the disaggregation mechanisms.

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Amyloid disaggregation in protein aggregation disorders as a potential treatment.

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Proposed amyloid disaggregation mechanism of an ATP-independent chaperone (L-PGDS).

Introduction

Protein aggregation and deposition of uniformly arranged amyloid fibrils in the form of plaques or amorphous aggregates is characteristic of amyloid diseases. The accumulation and deposition of proteins result in toxicity and cause deleterious effects on affected individuals known as amyloidosis. There are about fifty different proteins and peptides involved in amyloidosis including neurodegenerative diseases and diseases affecting vital organs. Despite the strenuous effort to find a suitable treatment option for these amyloid disorders, very few compounds had made it to unsuccessful clinical trials. It has become a compelling challenge to understand and manage amyloidosis with the increased life expectancy and ageing population.

Objective

While most of the currently available literature and knowledge base focus on the amyloid inhibitory mechanism as a treatment option, it is equally important to organize and understand amyloid disaggregation strategies. Disaggregation strategies are important and crucial as they are present innately functional in many living systems and dissolution of preformed amyloids may provide a direct benefit in many pathological conditions. In this review, we have compiled the known amyloid disaggregation mechanism, interactions, and possibilities of using disaggregases as a treatment option for amyloidosis.

Methods

We have provided the structural details using protein-ligand docking models to visualize the interaction between these disaggregases with amyloid fibrils and their respective proposed amyloid disaggregation mechanisms.

Results

After reviewing and comparing the different amyloid disaggregase systems and their proposed mechanisms, we presented two different hypotheses for ATP independent disaggregases using L-PGDS as a model.

Conclusion

Finally, we have highlighted the importance of understanding the underlying disaggregation mechanisms used by these chaperones and organic compounds before the implementation of these disaggregases as a potential treatment option for amyloidosis.

Human amniotic epithelial cell-derived extracellular vesicles provide an extracellular matrix-based microenvironment for corneal injury repair

To study the biological functions and applications of human amniotic epithelial cell-derived extracellular vesicles (hAEC-EVs), the cargos of hAEC-EVs were analyzed using miRNA sequencing and proteomics analysis. The hAECs and hAEC-EVs in this study had specific characteristics. Multi-omics analyses showed that extracellular matrix (ECM) reorganization, inhibition of excessive myofibroblasts, and promotion of target cell adhesion to the ECM were their primary functions. We evaluated the application of hAEC-EVs for corneal alkali burn healing in rabbits and elucidated the fundamental mechanisms. Slit-lamp images revealed that corneal alkali burns induced central epithelial loss, stromal haze, iris, and pupil obscurity in rabbits. Slit-lamp examination and histological findings indicated that hAEC-EVs facilitated re-epithelialization of the cornea after alkali burns, reduced scar formation and promoted the restoration of corneal tissue transparency. Significantly fewer α-SMA-positive myofibroblasts were observed in the hAEC-EV-treated group than the PBS group. HAEC-EVs effectively promoted the proliferation and migration of hCECs and hCSCs in vitro and activated the focal adhesion signaling pathway. We demonstrated that hAEC-EVs were excellent cell-free candidates for the treatment of ECM lesion-based diseases, including corneal alkali burns. HAEC-EVs promoted ECM reorganization and cell adhesion of target tissues or cells via orderly activation of the focal adhesion signaling pathway.

Clusterin, other extracellular chaperones, and eye disease

Proteostasis refers to all the processes that maintain the correct expression level, location, folding and turnover of proteins, essential to organismal survival. Both inside cells and in body fluids, molecular chaperones play key roles in maintaining proteostasis. In this article, we focus on clusterin, the first-recognized extracellular mammalian chaperone, and its role in diseases of the eye. Clusterin binds to and inhibits the aggregation of proteins that are misfolded due to mutations or stresses, clears these aggregating proteins from extracellular spaces, and facilitates their degradation. Clusterin exhibits three main homeostatic activities: proteostasis, cytoprotection, and anti-inflammation. The so-called "protein misfolding diseases" are caused by aggregation of misfolded proteins that accumulate pathologically as deposits in tissues; we discuss several such diseases that occur in the eye. Clusterin is typically found in these deposits, which is interpreted to mean that its capacity as a molecular chaperone to maintain proteostasis is overwhelmed in the disease state. Nevertheless, the role of clusterin in diseases involving such deposits needs to be better defined before therapeutic approaches can be entertained. A more straightforward case can be made for therapeutic use of clusterin based on its proteostatic role as a proteinase inhibitor, as well as its cytoprotective and anti-inflammatory properties. It is likely that clusterin works together in this way with other extracellular chaperones to protect the eye from disease, and we discuss several examples. We end this article by predicting future steps that may lead to development of clusterin as a biological drug.

The Clinical Guiding Role of the Distribution of Corneal Nerves in the Selection of Incision for Penetrating Corneal Surgery in Canines

The cornea is one of the regions with the highest density of nerve terminals in the animal body and it bears such functions as nourishing the cornea and maintaining corneal sensation. In veterinary clinical practice, the corneoscleral limbus incision is frequently applied in cataract surgery, peripheral iridectomy, and other procedures for glaucoma. Inevitably, it would cause damage to the nerve roots that enter the cornea from the corneal limbus, thus inducing a series of complications. In this paper, the in vitro cornea (39 corneas from 23 canines, with ages ranging from 8 months old to 3 years old, including 12 male canines and 11 female canines) was divided into 6 zones, and the whole cornea was stained with gold chloride. After staining, corneal nerves formed neural networks at different levels of cornea. There was no significant difference in the number of nerve roots at the corneoscleral limbus between different zones (F = 1.983, p = 0.082), and the nerve roots at the corneoscleral limbus (mean value, 24.43; 95% CI, 23.43-25.42) were evenly distributed. Additionally, there was no significant difference in the number of corneal nerve roots between male and female canines (p = 0.143). There was also no significant difference in the number of corneal nerve roots between adult canines and puppies (p = 0.324). The results of the above analysis will provide a reasonable anatomical basis for selecting the incision location and orientation of penetrating surgery for the canine cornea in veterinary practice.

Conditions for maintenance of hepatocyte differentiation and function in 3D cultures

Spheroid cultures of primary human hepatocytes (PHH) are used in studies of hepatic drug metabolism and toxicity. The cultures are maintained under different conditions, with possible confounding results. We performed an in-depth analysis of the influence of various culture conditions to find the optimal conditions for the maintenance of an in vivo like phenotype. The formation, protein expression, and function of PHH spheroids were followed for three weeks in a high-throughput 384-well format. Medium composition affected spheroid histology, global proteome profile, drug metabolism and drug-induced toxicity. No epithelial-mesenchymal transition was observed. Media with fasting glucose and insulin levels gave spheroids with phenotypes closest to normal PHH. The most expensive medium resulted in PHH features most divergent from that of native PHH. Our results provide a protocol for culture of healthy PHH with maintained function - a prerequisite for studies of hepatocyte homeostasis and more reproducible hepatocyte research.

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3D spheroid cultures were established in 384-well format

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Eight different media variants were used to optimize the 3D cultures

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Optimized William's medium was as good as expensive commercial medium

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The 3D cultures were used to study drug metabolism and toxicity

Potential underlying genetic associations between keratoconus and diabetes mellitus

Background Keratoconus (KC) is the most common ectatic corneal disease, characterized by significantly localized thinning of the corneal stroma. Genetic, environmental, hormonal, and metabolic factors contribute to the pathogenesis of KC. Additionally, multiple comorbidities, such as diabetes mellitus, may affect the risk of KC. Main Body Patients with diabetes mellitus (DM) have been reported to have lower risk of developing KC by way of increased endogenous collagen crosslinking in response to chronic hyperglycemia. However, this remains a debated topic as other studies have suggested either a positive association or no association between DM and KC. To gain further insight into the underlying genetic components of these two diseases, we reviewed candidate genes associated with KC and central corneal thickness in the literature. We then explored how these genes may be regulated similarly or differentially under hyperglycemic conditions and the role they play in the systemic complications associated with DM. Conclusion Our comprehensive review of potential genetic factors underlying KC and DM provides a direction for future studies to further determine the genetic etiology of KC and how it is influenced by systemic diseases such as diabetes.

Automatic segmentation of corneal deposits from corneal stromal dystrophy images via deep learning

BACKGROUND

Granular dystrophy is the most common stromal dystrophy. To perform automated segmentation of corneal stromal deposits, we trained and tested a deep learning (DL) algorithm from patients with corneal stromal dystrophy and compared its performance with human segmentation.

METHODS

In this retrospective cross-sectional study, we included slit-lamp photographs by sclerotic scatter from patients with corneal stromal dystrophy and real-world slit-lamp photographs via various techniques (diffuse illumination, tangential illumination, and sclerotic scatter). Our data set included 1007 slit-lamp photographs of semi-automatically generated handcraft masks on granular and linear lesions from corneal stromal dystrophy patients (806 for the training set and 201 for test set). For external test (140 photographs), we applied the DL algorithm and compared between automated and human segmentation. For performance, we estimated the intersection of union (IoU), global accuracy, and boundary F1 (BF) score for segmentation.

RESULTS

In 201 internal test set, IoU, global accuracy, and BF score with 95 % confidence Interval were 0.81 (0.79-0.82), 0.99 (0.98-0.99), and 0.93 (0.92-0.95), respectively. In 140 heterogenous external test set as a real-world data, those were 0.64 (0.61-0.67), 0.95 (0.94-0.96), and 0.70 (0.64-0.76) via DL algorithm and 0.56 (0.51-0.61), 0.95 (0.94-0.96), and 0.70 (0.65-0.74) via human rater, respectively.

CONCLUSIONS

We developed an automated segmentation DL algorithm for corneal stromal deposits in patients with corneal stromal dystrophy. Segmentation on corneal deposits was accurate via the DL algorithm in the well-controlled dataset and showed reasonable performance in a real-world setting. We suggest this automatic segmentation of corneal deposits helps to monitor the disease and can evaluate possible new treatments.

Comparison of the rabbit and human corneal endothelial proteomes regarding proliferative capacity

The shortage of human donor corneas has raised important concerns about engineering of corneal endothelial cells (CECs) for clinical use. However, due to the limited proliferative capacity of human CECs, driving them into proliferation and regeneration may be difficult. Unlike human CECs, rabbit CECs have a marked proliferative capacity. To clarify the potential reason for this difference, we analysed the proteomes of four human corneal endothelium samples and four rabbit corneal endothelium samples with quantitative label-free proteomics and downstream analysis. We discovered that vitamin and selenocompound metabolism and some signaling pathways such as NF-kappa B signaling pathway differed between the samples. Moreover, TGFβ, PITX2 and keratocan were distinctively expressed in rabbit samples, which might be associated with active proliferation in rabbit CECs. This study illustrates the proteomic differences between human and rabbit CECs and might promote CEC engineering strategies.

Differentially Expressed Gene Pathways in the Conjunctiva of Sjögren Syndrome Keratoconjunctivitis Sicca

Sjögren syndrome (SS) is an autoimmune condition that targets the salivary and lacrimal glands, with cardinal clinical signs of dry eye (keratoconjunctivitis sicca, KCS) and dry mouth. The conjunctiva of SS patients is often infiltrated by immune cells that participate in the induction and maintenance of local inflammation. The purpose of this study was to investigate immune-related molecular pathways activated in the conjunctiva of SS patients. Female SS patients (n=7) and controls (n=19) completed a series of oral, ocular surface exams. Symptom severity scores were evaluated using validated questionnaires (OSDI and SANDE). All patients fulfilled the ACR/EULAR criteria for SS and the criteria for KCS. Fluorescein and lissamine green dye staining evaluated tear-break-up time (TBUT), corneal and conjunctival disease, respectively. Impression cytology of the temporal bulbar conjunctiva was performed to collect cells lysed and subjected to gene expression analysis using the NanoString Immunology Panel. 53/594 differentially expressed genes (DEGs) were observed between SS and healthy controls; 49 DEGs were upregulated, and 4 were downregulated (TRAF5, TGFBI, KLRAP1, and CMKLRI). The top 10 DEGs in descending order were BST2, IFITM1, LAMP3, CXCL1, IL19, CFB, LY96, MX1, IL4R, CDKN1A. Twenty pathways had a global significance score greater or equal to 2. Spearman correlations showed that 29/49 upregulated DEGs correlated with either TBUT (inverse) or OSDI or conjunctival staining score (positive correlations). Venn diagrams identified that 26/29 DEGs correlated with TBUT, 5/26 DEGs correlated with OSDI, and 16/26 correlated with conjunctival staining scores. Five upregulated DEGs (CFB, CFI, IL1R1, IL2RG, IL4R) were uniquely negatively correlated with TBUT. These data indicate that the conjunctiva of SS patients exhibits a phenotype of immune activation, although some genes could be inhibitory. Some of the DEGs and pathways overlap with previous DEGs in salivary gland biopsies, but new DEGs were identified, and some of these correlated with symptoms and signs of dry eye. Our results indicate that gene analysis of conjunctiva imprints is a powerful tool to understand the pathogenesis of SS and develop new therapeutic targets.

Time- and Stimulus-Dependent Characteristics of Innate Immune Cells in Organ-Cultured Human Corneal Tissue

PURPOSE

The pattern of immune cells infiltrating the corneal stroma has been extensively studied in mice, but data on human tissue have been far less elaborate. To further characterize the number and differentiation state of resident immune cells in organ-cultured human corneal tissue, we employed a comprehensive bioinformatic deconvolution (xCell) of bulk RNA-sequencing (RNA-seq) data, immunohistochemistry (IHC), and flow cytometry (FC).

METHODS

A transcriptome-based analysis of immune cell types in human corneal samples was performed. The results were validated by IHC, focusing on the identification of pro-inflammatory (M1) and regulatory (M2) macrophages. A protocol was established to identify these 2 different macrophage populations in human corneal tissue by means of FC. Subsequently, corneal samples in organ culture were differentially stimulated by IL-10, IL-4 &amp; IL-13, or LPS and macrophage populations were evaluated regarding their response to these stimuli. Furthermore, cell survival was analyzed in correlation with time in organ culture.

RESULTS

xCell-based mathematical deconvolution of bulk RNA-seq data revealed the presence of CD8 T cells, Th17 cells, dendritic cells, and macrophages as the predominant immune cell types in organ-cultured human corneal tissue. Furthermore, RNA-seq allowed the detection of different macrophage marker genes in corneal samples, including PTPRC (CD45), ITGAM (CD11b), CD14, and CD74. Our RNA-seq data showed no evidence of a relevant presence of monocytes in human corneal tissue. The presence of different macrophage subtypes was confirmed by IHC. The disintegration and subsequent FC analysis of human corneal samples showed the presence of both M1 (HLA-DR+, CD282+, CD86+, and CD284+) and M2 (CD163+ and CD206+) macrophage subtypes. Furthermore, we found that the total number of macrophages in corneal samples decreased more than the total cell count with increasing tissue culture time. Treatment with IL-10 led to higher total cell counts per cornea and to an increased expression of the M2 marker CD163 (p < 0.05) while expression levels of various M1 macrophage markers were not significantly reduced by interleukin treatment.

CONCLUSIONS

Regarding different macrophage populations, untreated human corneas showed more M1 than M2 macrophages. With increasing organ culture time, these macrophages decreased. In terms of cell dynamics, adding interleukins to the organ culture medium influenced the phenotype of macrophages within the cornea as detected by FC. Modifying the immunomodulatory properties of human grafts appears a promising approach to further reduce the risk of graft rejection in patients. In this context, treatment with interleukins was more effective in upregulating M2 macrophages than in suppressing M1 macrophages in corneal tissue.

Mutation-induced dimerization of transforming growth factor-β-induced protein may drive protein aggregation in granular corneal dystrophy

Protein aggregation in the outermost layers of the cornea, which can lead to cloudy vision and in severe cases blindness, is linked to mutations in the extracellular matrix protein transforming growth factor-β-induced protein (TGFBIp). Among the most frequent pathogenic mutations are R124H and R555W, both associated with granular corneal dystrophy (GCD) characterized by the early-onset formation of amorphous aggregates. The molecular mechanisms of protein aggregation in GCD are largely unknown. In this study, we determined the crystal structures of R124H, R555W, and the lattice corneal dystrophy-associated A546T. Although there were no changes in the monomeric TGFBIp structure of any mutant that would explain their propensity to aggregate, R124H and R555W demonstrated a new dimer interface in the crystal packing, which is not present in wildtype TGFBIp or A546T. This interface, as seen in both the R124H and R555W structures, involves residue 124 of the first TGFBIp molecule and 555 in the second. The interface is not permitted by the Arg124 and Arg555 residues of wildtype TGFBIp and may play a central role in the aggregation exhibited by R124H and R555W in vivo. Using cross-linking mass spectrometry and in-line size exclusion chromatography-small-angle X-ray scattering, we characterized a dimer formed by wildtype and mutant TGFBIps in solution. Dimerization in solution also involves interactions between the N- and C-terminal domains of two TGFBIp molecules but was not identical to the crystal packing dimerization. TGFBIp-targeted interventions that disrupt the R124H/R555W crystal packing dimer interface might offer new therapeutic opportunities to treat patients with GCD.

Mutant Presenilin 1 Dysregulates Exosomal Proteome Cargo Produced by Human-Induced Pluripotent Stem Cell Neurons

The accumulation and propagation of hyperphosphorylated tau (p-Tau) is a neuropathological hallmark occurring with neurodegeneration of Alzheimer's disease (AD). Extracellular vesicles, exosomes, have been shown to initiate tau propagation in the brain. Notably, exosomes from human-induced pluripotent stem cell (iPSC) neurons expressing the AD familial A246E mutant form of presenilin 1 (mPS1) are capable of inducing tau deposits in the mouse brain after in vivo injection. To gain insights into the exosome proteome cargo that participates in propagating tau pathology, this study conducted proteomic analysis of exosomes produced by human iPSC neurons expressing A246E mPS1. Significantly, mPS1 altered the profile of exosome cargo proteins to result in (1) proteins present only in mPS1 exosomes and not in controls, (2) the absence of proteins in the mPS1 exosomes which were present only in controls, and (3) shared proteins which were upregulated or downregulated in the mPS1 exosomes compared to controls. These results show that mPS1 dysregulates the proteome cargo of exosomes to result in the acquisition of proteins involved in the extracellular matrix and protease functions, deletion of proteins involved in RNA and protein translation systems along with proteasome and related functions, combined with the upregulation and downregulation of shared proteins, including the upregulation of amyloid precursor protein. Notably, mPS1 neuron-derived exosomes displayed altered profiles of protein phosphatases and kinases involved in regulating the status of p-tau. The dysregulation of exosome cargo proteins by mPS1 may be associated with the ability of mPS1 neuron-derived exosomes to propagate tau pathology.

Compound heterozygous mutations in TGFBI cause a severe phenotype of granular corneal dystrophy type 2

We investigated the clinical and genetic features of patients with severe phenotype of granular corneal dystrophy type 2 (GCD2) associated with compound heterozygosity in the transforming growth factor-β-induced (TGFBI) gene. Patients with severe GCD2 underwent ophthalmic examination (best-corrected visual acuity test, intraocular pressure measurement, slit-lamp examination, and slit-lamp photograph analysis) and direct Sanger sequencing of whole-TGFBI. The patient’s family was tested to determine the pedigrees. Five novel mutations (p.(His174Asp), p.(Ile247Asn), p.(Tyr88Cys), p.(Arg257Pro), and p.(Tyr468*)) and two known mutations (p.(Asn544Ser) and p.(Arg179*)) in TGFBI were identified, along with p.(Arg124His), in the patients. Trans-phase of TGFBI second mutations was confirmed by pedigree analysis. Multiple, extensive discoid granular, and increased linear deposits were observed in the probands carrying p.(Arg124His) and other nonsense mutations. Some patients who had undergone phototherapeutic keratectomy experienced rapid recurrence (p.(Ile247Asn) and p.(Asn544Ser)); however, the cornea was well-maintained in a patient who underwent deep anterior lamellar keratoplasty (p.(Ile247Asn)). Thus, compound heterozygosity of TGFBI is associated with the phenotypic variability of TGFBI corneal dystrophies, suggesting that identifying TGFBI second mutations may be vital in patients with extraordinarily severe phenotypes. Our findings indicate the necessity for a more precise observation of genotype–phenotype correlation and additional care when treating TGFBI corneal dystrophies.

Exacerbation of Granular Corneal Dystrophy Type 2 After Small Incision Lenticule Extraction

PURPOSE

To report the outcome of unilateral small incision lenticule extraction (SMILE) in a patient with granular corneal dystrophy type 2 (GCD2).

METHODS

Slit-lamp photography and Fourier domain optical coherence tomography were used to document the clinical course and appearance of the corneas in a patient with genetically determined GCD2 who underwent unilateral SMILE in the right eye.

RESULTS

Slit-lamp examination of a 23-year-old woman revealed 2 faint opacities at the surgical interface approximately 2 months after the SMILE procedure had been performed on her right eye. Nine and 3 typical GCD2 deposits located immediately beneath the Bowman layer were observed in the right and left corneas, respectively. Over time, the deposits at the interface increased in size, density, and number in the right eye. Fourier domain optical coherence tomography performed 33 months after the SMILE procedure revealed deposits at the SMILE interface that were distinct from those located immediately beneath the Bowman layer. The severity of disease exacerbation was less in this patient than what is typically observed in others who have undergone laser-assisted in situ keratomileusis or photorefractive keratectomy.

CONCLUSIONS

SMILE is contraindicated in patients with GCD2, as are other corneal refractive surgical procedures. This case highlights the importance of genetic testing before the performance of refractive corneal procedures-especially for patients with corneal opacities on preoperative slit-lamp examination or a family history of corneal disease compatible with that of a corneal dystrophy.

Genotypic Homogeneity in Distinctive Transforming Growth Factor-Beta Induced (TGFBI) Protein Phenotypes

Background: To evaluate the distribution of the transforming growth factor-beta induced (TGFBI) corneal dystrophies in a multi-ethnic population in Singapore, and to present the different phenotypes with the same genotype. Methods: This study included 32 patients. Slit lamp biomicroscopy was performed for each patient to determine the disease phenotype. Genomic DNA was extracted from the blood samples and the 17 exons of the TGFBI gene were amplified by PCR and sequenced bi-directionally for genotype analysis. Results: Regarding phenotypes, the study patients comprised 11 (34.4%; 8 with R555W and 3 with R124H mutation) patients with granular corneal dystrophy type 1 (GCD1), 6 (18.8%; 5 with R124H and 1 with R124C mutation) patients with GCD2, 13 (40.6%; 7 with R124C, 2 with H626R, 2 with L550P, 1 with A620D and 1 with H572R) patients with lattice corneal dystrophy (LCD) and 2 (6.3%; 1 with R124L and 1 with R124C) patients with Reis–Bückler corneal dystrophy. Regarding genotype, R124H mutation was associated with GCD2 (5 cases; 62.5%) and GCD1 (3 cases; 37.5%). R124C mutation was associated with LCD (7 cases; 87.5%) and GCD2 (1 case; 12.5%). All the 8 cases (100%) of R555W mutation were associated with GCD1. Conclusions: Although the association between genotype and phenotype was good in most cases (65.7%; 21 of 32 patients), genotype/phenotype discrepancy was observed in a significant number.

Novel Mutations in COL6A3 That Associated With Peters' Anomaly Caused Abnormal Intracellular Protein Retention and Decreased Cellular Resistance to Oxidative Stress

Peters' anomaly (PA) is a rare form of anterior segment dysgenesis characterized by central corneal opacity accompanied by iridocorneal or lenticulo-corneal adhesions. Although genetic mutations, particularly those affecting transcription factors that function in eye development, are known to cause PA, the etiology of this disease remains poorly understood. In this study, 23 patients with PA were recruited for panel sequencing. Four out of 23 patients were found to carry variants in known PA causal genes, PITX2 and PITX3. More importantly, two homozygous mutations (NM_057164: p.Val86Ala and p.Arg689Cys) in the COL6A3 gene (collagen type VI alpha-3 chain) that correlated with the phenotype of type I PA were identified, and then validated by following whole-exome sequencing. The expression profile of the COL6A3 gene in the cornea and the impact of the mutations on protein physiological processing and cellular function were further explored. It was shown that COL6A3 presented relatively high expression in the cornea. The mutant COL6A3 protein was relatively retained intracellularly, and its expression reduced cellular resistance to oxidative stress through an enhanced endoplasmic reticulum stress response. Taken together, our findings expanded the known genetic spectrum of PA, and provided evidence for the involvement of COL6A3 or collagen VI in ocular anterior segment development, thereby offering new insight for future investigations targeting PA.

Corneal Dystrophy in Dutch Belted Rabbits as a Possible Model of Thiel-Behnke Subtype of Epithelial-Stromal TGFβ-Induced Corneal Dystrophy

The International Committee for Classification of Corneal Dystrophies (IC3D) categorized corneal dystrophies in humans using anatomic, genotypic, and clinicopathologic phenotypic features. Relative to the IC3D classification, a review of the veterinary literature confirmed that corneal dystrophy is imprecisely applied to any corneal opacity and to multiple poorly characterized histologic abnormalities of the cornea in animals. True corneal dystrophy occurs in mice with targeted mutations and spontaneously in pet dogs and cats and in Dutch belted (DB) rabbits, but these instances lack complete phenotyping or genotyping. Corneal dystrophy in DB rabbits can be an important confounding finding in ocular toxicology studies but has only been described once. Therefore, the ophthalmology and pathology of corneal dystrophy in 13 DB rabbits were characterized to determine whether the findings were consistent with or a possible model of any corneal dystrophy subtypes in humans. Slit lamp and optical coherence tomography (OCT) imaging were used to characterize corneal dystrophy over 4 months in young DB rabbits. The hyperechoic OCT changes correlated with light microscopic findings in the anterior stroma, consisting of highly disordered collagen fibers and enlarged keratocytes. Histochemical stains did not reveal abnormal deposits. Small clusters of 8 to 16 nm diameter curly fibers identified by transmission electron microscopy were consistent with Thiel-Behnke (TBCD) subtype of epithelial-stromal transforming growth factor β-induced dystrophies. Sporadic corneal dystrophy in DB rabbits appears to be a potential animal model of TBCD, but genotypic characterization will be required to confirm this categorization.

Novel insights into gene therapy in the cornea

Corneal disease remains a leading cause of impaired vision world-wide, and advancements in gene therapy continue to develop with promising success to prevent, treat and cure blindness. Ideally, gene therapy requires a vector and gene delivery method that targets treatment of specific cells or tissues and results in a safe and non-immunogenic response. The cornea is a model tissue for gene therapy due to its ease of clinician access and immune-privileged state. Improvements in the past 5-10 years have begun to revolutionize the approach to gene therapy in the cornea with a focus on adeno-associated virus and nanoparticle delivery of single and combination gene therapies. In addition, the potential applications of gene editing (zinc finger nucleases [ZNFs], transcription activator-like effector nucleases [TALENs], Clustered Regularly Interspaced Short Palindromic Repeats/Associated Systems [CRISPR/Cas9]) are rapidly expanding. This review focuses on recent developments in gene therapy for corneal diseases, including promising multiple gene therapy, while outlining a practical approach to the development of such therapies and potential impediments to successful delivery of genes to the cornea.

Mutation-Independent Allele-Specific Editing by CRISPR-Cas9, a Novel Approach to Treat Autosomal Dominant Disease

CRISPR-Cas9 provides a tool to treat autosomal dominant disease by non-homologous end joining (NHEJ) gene disruption of the mutant allele. In order to discriminate between wild-type and mutant alleles, Streptococcus pyogenes Cas9 (SpCas9) must be able to detect a single nucleotide change. Allele-specific editing can be achieved by using either a guide-specific approach, in which the missense mutation is found within the guide sequence, or a protospacer-adjacent motif (PAM)-specific approach, in which the missense mutation generates a novel PAM. While both approaches have been shown to offer allele specificity in certain contexts, in cases where numerous missense mutations are associated with a particular disease, such as TGFBI (transforming growth factor β-induced) corneal dystrophies, it is neither possible nor realistic to target each mutation individually. In this study, we demonstrate allele-specific CRISPR gene editing independent of the disease-causing mutation that is capable of achieving complete allele discrimination, and we propose it as a targeting approach for autosomal dominant disease. Our approach utilizes natural variants in the target region that contain a PAM on one allele that lies in cis with the causative mutation, removing the constraints of a mutation-dependent approach. Our innovative patient-specific guide design approach takes into account the patient's individual genetic make-up, allowing on- and off-target activity to be assessed in a personalized manner.

Topical siRNA delivery to the cornea and anterior eye by hybrid silicon-lipid nanoparticles

The major unmet need and crucial challenge hampering the exciting potential of RNAi therapeutics in ophthalmology is to find an effective, safe and non-invasive means of delivering siRNA to the cornea. Although all tissues of the eye are accessible by injection, topical application is preferable for the frequent treatment regimen that would be necessary for siRNA-induced gene silencing. However, the ocular surface is one of the more complex biological barriers for drug delivery due to the combined effect of short contact time, tear dilution and poor corneal cell penetration. Using nanotechnology to overcome the challenges, we developed a unique silicon-based delivery platform for ocular delivery of siRNA. This biocompatible hybrid of porous silicon nanoparticles and lipids has demonstrated an ability to bind nucleic acid and deliver functional siRNA to corneal cells both in vitro and in vivo. Potent transfection of human corneal epithelial cells with siRNA-ProSilic® formulation was followed by a successful downregulation of reporter protein expression. Moreover, siRNA complexed with this silicon-based hybrid and applied in vivo topically to mice eyes penetrated across all cornea layers and resulted in a significant reduction of the targeted protein expression in corneal epithelium. In terms of siRNA loading capacity, system versatility, and potency of action, ProSilic provides unique attributes as a biodegradable delivery platform for therapeutic oligonucleotides.

Corneal dystrophies

Corneal dystrophies are broadly defined as inherited disorders that affect any layer of the cornea and are usually progressive, bilateral conditions that do not have systemic effects. The 2015 International Classification of Corneal Dystrophies classifies corneal dystrophies into four classes: epithelial and subepithelial dystrophies, epithelial-stromal TGFBI dystrophies, stromal dystrophies and endothelial dystrophies. Whereas some corneal dystrophies may result in few or mild symptoms and morbidity throughout a patient's lifetime, others may progress and eventually result in substantial visual and ocular disturbances that require medical or surgical intervention. Corneal transplantation, either with full-thickness or partial-thickness donor tissue, may be indicated for patients with advanced corneal dystrophies. Although corneal transplantation techniques have improved considerably over the past two decades, these surgeries are still associated with postoperative risks of disease recurrence, graft failure and other complications that may result in blindness. In addition, a global shortage of cadaveric corneal graft tissue critically limits accessibility to corneal transplantation in some parts of the world. Ongoing advances in gene therapy, regenerative therapy and cell augmentation therapy may eventually result in the development of alternative, novel treatments for corneal dystrophies, which may substantially improve the quality of life of patients with these disorders.

Investigation of TGFBI (transforming growth factor beta-induced) Gene Mutations in Families with Granular Corneal Dystrophy Type 1 in the Konya Region

Objectives:

Granular corneal dystrophies (GCD) are characterized by small, discrete, sharp-edged, grayish-white opacities in the corneal stroma. Among the genes responsible for the development of GCD, the most strongly related gene is transforming growth factor beta-induced (TGFBI), located in the 5q31.1 locus. Studies show that R124H in exon 4 and R555W in exon 12 are hot-spot mutations in the TGFBI gene that lead to GCD development. In this study, we aimed to investigate these two hot-spot mutations in exons 4 and 12 of the TGFBI gene and other possible mutations in the same regions, which code important functional regions of the protein, in Turkish families with GCD1 and to determine the relationship between the mutations and disease and related phenotypes.

Materials and Methods:

The study included, 16 individuals diagnosed with GCD type 1 (GCD1), 11 of these patients’ healthy relatives, and 28 unrelated healthy individuals. DNA was obtained from peripheral blood samples taken from each individual and polymerase chain reaction was used to amplify target gene regions. Genotyping studies were done by sequence analysis.

Results:

The R124S mutation in exon 4 of TGFBI was not detected in the patients or healthy individuals in our study. However, all individuals diagnosed as having GCD1 were found to be heterozygous carriers of the R555W mutation in exon 12 of TGFBI. This mutation was not detected in healthy family members or control individuals unrelated to these families. In addition, we detected the silent mutation F540F in exon 12 and c.32924 G>A substitution in an intronic region of the gene in a few patients and healthy individuals.

Conclusion:

Our study strongly supports the association of GCD1 with R555W mutation in exon 12 region of the TGFBI gene, as reported in the literature.

Involvement of the JNK signaling in granular corneal dystrophy by modulating TGF-β-induced TGFBI expression and corneal fibroblast apoptosis

Granular corneal dystrophy (GCD) is featured by corneal deposits of transforming growth factor beta-induced gene (TGFBI) mediated by the TGF-β (transforming growth factor-β)/Smad signaling. However, the roles of c-Jun amino-terminal kinase (JNK) pathway in GCD pathogenesis remains unexplored, which was investigated in this study. JNK signaling activation and inhibition in primary corneal fibroblasts were obtained by treatments with anisomycin and SP600125, respectively. Protein abundance and phosphorylation were detected by immunoblotting. Cell viability and apoptosis were analyzed by CCK-8 and flow cytometry respectively. TGFBI deposit and autophagy progression were assessed by immunofluorescence. The results found that JNK1 expression and phosphorylation were greatly increased in corneal tissues from GCD2 patients. JNK signaling activation impaired the viability and promoted apoptosis and autophagy processes in primary corneal fibroblasts, along with Smad2/3 phosphorylation, TGFBI accumulation and Bcl-2 suppression. Autophagy related proteins, such as ATG5 (autophagy related 5), ATG12 (autophagy related 12) and LC3B (microtubule-associated protein 1 light chain 3 beta), were also increased in anisomycin or TGF-β1 treated corneal fibroblasts. However, SP600125 effectively reversed the above effect induced by TGF-β1 treatment in corneal fibroblasts, including the TGF-β-induced autophagy progression. The results suggested that JNK signaling was activated in GCD2 corneal tissues, and it mediated the TGF-β-induced TGFBI protein accumulation and apoptosis of corneal fibroblasts during GCD2 pathogenesis.

Generation of mouse model of TGFBI-R124C corneal dystrophy using CRISPR/Cas9-mediated homology-directed repair

Mutations in transforming growth factor-beta-induced (TGFBI) gene cause clinically distinct types of corneal dystrophies. To delineate the mechanisms driving these dystrophies, we focused on the R124C mutation in TGFBI that causes lattice corneal dystrophy type1 (LCD1) and generated novel transgenic mice harbouring a single amino acid substitution of arginine 124 with cysteine in TGFBI via ssODN-mediated base-pair substitution using CRISPR/Cas9 technology. Eighty percent of homozygous and 9.1% of heterozygous TGFBI-R124C mice developed a corneal opacity at 40 weeks of age. Hematoxylin and eosin and Masson trichrome staining showed eosinophilic deposits in subepithelial corneal stroma that stained negative for Congo-red. Although amyloid deposition was not observed in TGFBI-R124C mice, irregular amorphous deposits were clearly observed via transmission electron microscopy near the basement membrane. Interestingly, we found that the corneal deposition of TGFBI protein (TGFBIp) was significantly increased in homozygous TGFBI-R124C mice, suggesting a pathogenic role for the mutant protein accumulation. Furthermore, as observed in the LCD1 patients, corneal epithelial wound healing was significantly delayed in TGFBI-R124C mice. In conclusion, our novel mouse model of TGFBI-R124C corneal dystrophy reproduces features of the human disease. This mouse model will help delineate the pathogenic mechanisms of human corneal dystrophy.

Novel Mutations Associated With Various Types of Corneal Dystrophies in a Han Chinese Population

Aims: To study the genetic spectra of corneal dystrophies (CDs) in Han Chinese patients using next-generation sequencing (NGS).

Methods: NGS-based targeted region sequencing was performed to evaluate 71 CD patients of Han Chinese ethnicity. A custom-made capture panel was designed to capture all coding exons and untranslated regions plus 25 bp of intronic flanking sequences of 801 candidate genes for eye diseases. The Genome Analysis Tool Kit Best Practices pipeline and an intensive computational prediction pipeline were applied for the analysis of pathogenic variants.

Results: We achieved a mutation detection rate of 59.2% by NGS. Eighteen known mutations in CD-related genes were found in 42 out of 71 patients, and these cases showed a genotype–phenotype correlation consistent with previous reports. Nine novel variants that were likely pathogenic were found in various genes, including CHST6, TGFBI, SLC4A11, AGBL1, and COL17A1. These variants were all predicted to be protein-damaging by an intensive computational analysis.

Conclusions: This study expands the spectra of genetic mutations associated with various types of CDs in the Chinese population and highlights the clinical utility of targeted NGS for genetically heterogeneous CD.

Identification of Potential Biomarkers and Survival Analysis for Head and Neck Squamous Cell Carcinoma Using Bioinformatics Strategy: A Study Based on TCGA and GEO Datasets

The mechanism and gene markers of head and neck squamous cell carcinoma (HNSCC), a common malignant tumor, have not yet been identified. The aim of this study was to identify the key genes and pathways associated with HNSCC and to further analyze its molecular mechanism and prognostic significance. In this study, the expression profile chip data GSE6631 from Gene Expression Omnibus (GEO) included paired HNSCC tumor and normal samples from 22 patients; the RNAseq tertiary dataset of HNSCC and corresponding clinical information from The Cancer Genome Atlas (TCGA) included biological information of 12 normal head and neck tissues and 111 HNSCC sample tissues. Differentially expressed genes (DEGs) were screened by R software, and the pathway enrichment analysis of DEGs was performed by DAVID, String, and Sytoscape software programs. Combining the GEO and the TCGA databases, we used bioinformatics technology to screen out 50 DEGs in HNSCC and enrich the biological functions and key pathways of HNSCC. Then we performed Gene Ontology (GO) enrichment analysis, the Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway analysis, protein-protein interaction (PPI) analysis, and survival analysis on these DEGs. Using CMap, we identified candidate small molecules that might reverse HNSCC gene expression. Finally, four most important small molecules that could provide more reliable biomarkers for early diagnosis and individualized control of HNSCC were identified.

Identification of a Heterozygous Mutation in the TGFBI Gene in a Hui-Chinese Family with Corneal Dystrophy

Background/Aims

Corneal dystrophies (CDs) belong to a group of hereditary heterogeneous corneal diseases which result in visual impairment due to the progressive accumulation of deposits in different corneal layers. So far, mutations in several genes have been responsible for various CDs. The purpose of this study is to identify gene mutations in a three-generation Hui-Chinese family associated with granular corneal dystrophy type I (GCD1).

Methods

A three-generation Hui-Chinese pedigree with GCD1 was recruited for this study. Slit-lamp biomicroscopy, optical coherence tomography, and confocal microscopy were performed to determine the clinical features of available members. Whole exome sequencing was performed on two patients to screen for potential disease-causing variants in the family. Sanger sequencing was used to test the variant in the family members.

Results

Clinical examinations demonstrated bilaterally abundant multiple grayish-white opacities in the basal epithelial and superficial stroma layers of corneas of the two patients. Whole exome sequencing revealed that a heterozygous missense mutation (c.1663C > T, p.Arg555Trp) in the transforming growth factor beta-induced gene (TGFBI) was shared by the two patients, and it cosegregated with this disease in the family confirmed by Sanger sequencing.

Conclusions

The results suggested that the heterozygous TGFBI c.1663C > T (p.Arg555Trp) mutation was responsible for GCD1 in the Hui-Chinese family, which should be of great help in genetic counseling for this family.