Elastic microfibril distribution in the cornea: Differences between normal and keratoconic stroma

The optical and biomechanical properties of the cornea are largely governed by the collagen-rich stroma, a layer that represents approximately 90% of the total thickness. Within the stroma, the specific arrangement of superimposed lamellae provides the tissue with tensile strength, whilst the spatial arrangement of individual collagen fibrils within the lamellae confers transparency. In keratoconus, this precise stromal arrangement is lost, resulting in ectasia and visual impairment. In the normal cornea, we previously characterised the three-dimensional arrangement of an elastic fiber network spanning the posterior stroma from limbus-to-limbus. In the peripheral cornea/limbus there are elastin-containing sheets or broad fibers, most of which become microfibril bundles (MBs) with little or no elastin component when reaching the central cornea. The purpose of the current study was to compare this network with the elastic fiber distribution in post-surgical keratoconic corneal buttons, using serial block face scanning electron microscopy and transmission electron microscopy. We have demonstrated that the MB distribution is very different in keratoconus. MBs are absent from a region of stroma anterior to Descemet's membrane, an area that is densely populated in normal cornea, whilst being concentrated below the epithelium, an area in which they are absent in normal cornea. We contend that these latter microfibrils are produced as a biomechanical response to provide additional strength to the anterior stroma in order to prevent tissue rupture at the apex of the cone. A lack of MBs anterior to Descemet's membrane in keratoconus would alter the biomechanical properties of the tissue, potentially contributing to the pathogenesis of the disease

Intracrine activity involving NAD-dependent circadian steroidogenic activity governs age-associated meibomian gland dysfunction

新たなイントラクライン機構を用いた加齢性眼疾患治療へ --眼局所のホルモンの加齢変化とサーカディアンリズムが鍵--. 京都大学プレスリリース. 2022-02-14.Canonically, hormones are produced in the endocrine organs and delivered to target tissues. However, for steroids, the concept of tissue intracrinology, whereby hormones are produced in the tissues where they exert their effect without release into circulation, has been proposed, but its role in physiology/disease remains unclear. The meibomian glands in the eyelids produce oil to prevent tear evaporation, which reduces with aging. Here, we demonstrate that (re)activation of local intracrine activity through nicotinamide adenine dinucleotide (NAD+)-dependent circadian 3β-hydroxyl-steroid dehydrogenase (3β-HSD) activity ameliorates age-associated meibomian gland dysfunction and accompanying evaporative dry eye disease. Genetic ablation of 3β-HSD nullified local steroidogenesis and led to atrophy of the meibomian gland. Conversely, reactivation of 3β-HSD activity by boosting its coenzyme NAD+ availability improved glandular cell proliferation and alleviated the dry eye disease phenotype. Both women and men express 3β-HSD in the meibomian gland. Enhancing local steroidogenesis may help combat age-associated meibomian gland dysfunction

Prostaglandin E receptor subtype EP3 expression in human conjunctival epithelium and its changes in various ocular surface disorders.

BACKGROUND: In our earlier genome-wide association study on Stevens-Johnson Syndrome (SJS) and its severe variant, toxic epidermal necrolysis (TEN), we found that in Japanese patients with these severe ocular surface complications there was an association with prostaglandin E receptor 3 (EP3) gene (PTGER3) polymorphisms. We also reported that EP3 is dominantly expressed in the ocular surface-, especially the conjunctival epithelium, and suggested that EP3 in the conjunctival epithelium may down-regulate ocular surface inflammation. In the current study we investigated the expression of EP3 protein in the conjunctiva of patients with various ocular surface diseases such as SJS/TEN, chemical eye burns, Mooren's ulcers, and ocular cicatricial pemphigoid (OCP). METHODOLOGY/PRINCIPAL FINDINGS: Conjunctival tissues were obtained from patients undergoing surgical reconstruction of the ocular surface due to SJS/TEN, chemical eye burns, and OCP, and from patients with Mooren's ulcers treated by resection of the inflammatory conjunctiva. The controls were nearly normal human conjunctival tissues acquired at surgery for conjunctivochalasis. We performed immunohistological analysis of the EP3 protein and evaluated the immunohistological staining of EP3 protein in the conjunctival epithelium of patients with ocular surface diseases. EP3 was expressed in the conjunctival epithelium of patients with chemical eye burns and Mooren's ulcer and in normal human conjunctival epithelium. However, it was markedly down-regulated in the conjunctival epithelium of SJS/TEN and OCP patients. CONCLUSIONS: We posit an association between the down-regulation of EP3 in conjunctival epithelium and the pathogenesis and pathology of SJS/TEN and OCP, and suggest a common mechanism(s) in the pathology of these diseases. The examination of EP3 protein expression in conjunctival epithelium may aid in the differential diagnosis of various ocular surface diseases

Cultivation of Corneal Epithelial Cells on Intact and Denuded Human Amniotic Membrane.

PURPOSE. Surgery to reconstruct the ocular surface is greatly facilitated by the use of amniotic membrane, either as a biologic drape or, more recently, as a substrate for the transplantation of cultivated corneal epithelial cells. This study was designed to compare the usefulness of intact and denuded human amniotic membranes as a substrate for corneal epithelial cell culture. METHODS. Small (3-mm-diameter) biopsy specimens of superficial cornea including epithelium were excised from the central and limbal regions in rabbits. They were cultured on human amniotic membrane with or without amniotic epithelial cells and examined by light, scanning electron, and transmission electron microscopy. RESULTS. Cellular outgrowth from the central explants (n = 10) after 14 days in culture measured 1.82 ± 2.62 mm2 on intact amniotic membrane and 131.83 ± 28.31 mm2 on denuded amniotic membrane. In contrast, outgrowths from the limbal explants (n = 10) at the same time measured 4.58 ± 4.56 and 505.39 ± 134.20 mm2 on intact and denuded amniotic membranes, respectively. The leading edges of the outgrowths on intact amniotic membrane were much less uniform than those on denuded amniotic membrane, and, in the former, corneal epithelial cells appeared to migrate over the top of amniotic epithelial cells. Limbal cells cultivated on denuded amniotic membrane formed a nicely stratified layer that adhered well to the underlying amniotic membrane. CONCLUSIONS. Denuded amniotic membrane appears to be an excellent substrate for the cultivation of corneal epithelial cells, with a view to transplantation

Phenotypic investigation of human eyes with transplanted autologous cultivated oral mucosal epithelial sheets for severe ocular surface diseases.

Purpose To determine the epithelial lineage of origin of surgically removed grafts after autologous cultivated oral mucosal epithelial transplantation (COMET). Design Retrospective comparative case series. Participants We studied 6 eyes from 5 patients with total corneal stem cell destruction; 3 eyes were from patients with Stevens–Johnson syndrome and 3 eyes had sustained chemical injury. Methods Autologous cultivated oral mucosal epithelial sheets on human amniotic membrane (AM) were transplanted onto the ocular surface. Regrafting (2 eyes) or penetrating keratoplasty (4 eyes) was performed after the initial transplantation procedure for further visual rehabilitation. Main Outcome Measures The excised grafts were subjected to clinical evaluation and to light, scanning, and transmission electron microscopic (EM) study and to immunohistochemical analysis. Results In clinically failed grafts, EM and immunohistochemical analysis disclosed only small areas where the original cultivated oral epithelial cells persisted. Neighboring conjunctival epithelial cells had apparently invaded a large portion of the corneal surface (keratin 3[−], Muc5ac[+]); there were many blood vessels and inflammatory cells. In clinically successful grafts, transplanted cultivated oral epithelial cells survived and had adapted well to the host corneal tissues (keratin 3[+], Muc5ac[−]); there was no infiltration by inflammatory cells, nor was there dissolution of the AM substrate. Conclusions We posit that the process of graft opacification after COMET is responsible for the loss of transplanted cultivated oral epithelial cells and that this is followed by conjunctival cell invasion onto the corneal surface. We confirmed that in clinically successfully grafted eyes, autologous cultivated oral epithelial cells survived on the corneal surface and maintained ocular surface integrity

Two new spermidine alkaloids from Chisocheton weinlandii

The investigation of the MeOH extract of the leaves of Chisocheton weinlandii Harms (Meliaceae) revealed two new open-chain spermidine alkaloids, chisitine 1 (1) and chisitine 2 (2). Their structures were elucidated by NMR spectroscopy, tandem-mass spectrometry, and independant syntheses (Scheme 3). Detailed MS/MS fragmentation pathways are discussed for both compounds based on H/D exchange and 18O-labeling experiments (Schemes 1 and 2)