Special Senses
Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard in Toxicologic Pathology, 2018
The corneal endothelium is a single layer of flat, hexagonal, mesenchymal cells joined apically by tight junctions and have a Na/K ATP-dependent pump in the cell membrane to maintain stromal deturgescence (Baroody et al. 1987; Doughty 1994; Joyce 2003). Endothelial cell density is variable among species and within the cornea (less dense in the superior cornea than in the inferior cornea). Endothelial cells decrease in number with age. Humans, nonhuman primates, and cats have little or no regenerative capacity and undergo repair by cell sliding (migration) and individual cell enlargement. Dogs have some regenerative capacity, but repair is still mostly due to cell sliding. The endothelial cells of rabbits can divide and form multinucleated cells. Trauma to the corneal endothelium may allow proliferation of keratocytes with the formation of a fibrous membrane on the inner surface of the cornea (retrocorneal membrane) (Jakobiec and Bhat 2010; Sherrard and Rycroft 1967).
Herpes Simplex Virus Ocular Disease
Marie Studahl, Paola Cinque, Tomas Bergström in Herpes Simplex Viruses, 2017
HSV is not usually recovered directly from corneal homogenates of host corneal transplant buttons in patients with immune stromal keratitis, although it may be derived from organ culture on occasion (20). Nucleocapsids and capsids, or HSV DNA, have been observed in keratocytes and whole virions have been observed in the interstitium of some corneal buttons with immune stromal keratitis (20–24). Easty (25) demonstrated that HSV might enter stromal keratocytes where it could either be eliminated or escape the immune response and persist within this layer. The virus can also exist within the stroma as a whole virion shed into the stroma from neurons where it incites an inflammatory response; it can also behave as a slowly proliferating intracellular virus which can alter the antigenicity of the cell wall and elicit an immune response. Latent existence, during which the cell remains antigenically unchanged and there is no active clinical disease, also may occur. It is most likely the residual viral antigens within the stroma that incite the inflammatory response in immune stromal disease, subsequently involving lymphocytes, antiviral antibodies, serum complement, PMNs, and macrophages (12,19,26,27).
Therapeutic Approach in Fungal Keratitis
Mahendra Rai, Marcelo Luís Occhiutto in Mycotic Keratitis, 2019
Steroids role in the fungal keratitis treatment remains controversial (Nada et al. 2017). Some authors have described that early use of topical steroids for infectious keratitis helps reduce neovascularization, scarring and pain. Activated immune cells release cytokines, collagenases and growth factors, leading to keratocytes apoptosis and collagen destruction. Viable corneal keratocytes are transformed into activated fibroblasts, which restore the tissue defects by irregularly depositing collagen and the extracellular matrix. This causes opacification or haze during the scarring process.
Hyperosmolar Potassium Inhibits Corneal Myofibroblast Transformation and Prevent Corneal Scar
Published in Current Eye Research, 2023
Kai Liao, Zekai Cui, Zhijie Wang, Yu Peng, Shibo Tang, Jiansu Chen
Corneal transparency mainly depends on its organizational structure, which involves a highly ordered arrangement of collagen fibers.1,2 Normally, keratocytes are quiescent in the corneal stroma. However, they can differentiate into corneal fibroblasts (CFs) and myofibroblasts in response to different external stimulation, including trauma, infection, and inflammation.3,4 Previous studies have demonstrated that corneal myofibroblasts play an essential role during the process of corneal fibrosis.5,6 Corneal myofibroblasts can reportedly produce excessive amounts of collagen I, leading to the distortion of tissue architecture.3,7 Consequently, inhibiting corneal myofibroblast transformation to prevent corneal fibrosis has become the focus of many studies.
Progeroid syndrome of De Barsy – a case report and review of ophthalmic literature
Published in Ophthalmic Genetics, 2022
Manjushree Bhate, Merle Fernandes, Sirisha Senthil, Shruthi Bathula, Sarah Beilur
Histopathology section from corneal button showed an irregularly folded 3–5 layered stratified squamous epithelium. The Bowman’s layer was fragmented and replaced by scarred tissue. Focally linear calcific deposits were seen over the Bowmans layer (Band shaped keratopathy). The stroma was scarred and hypercellular with the presence of irregularly arranged keratocytes predominantly in anterior and mid stroma. Similar findings were reported by Aldave et al. Blood vessel formation and few scattered chronic inflammatory cells were also noted. Rest of the stroma was scarred and had loss of lamellar pattern with hyalinized collagen bundles (Compact stroma). Additionally, Descemet’s membrane was folded, and endothelial cells were attenuated. Von Gieson Verhoeff stain did not confirm the presence of elastin.
Effects of 1,25 and 24,25 Vitamin D on Corneal Fibroblast VDR and Vitamin D Metabolizing and Catabolizing Enzymes
Published in Current Eye Research, 2021
Xiaowen Lu, Zhong Chen, Mitchell A. Watsky
Extra-hepatic and extra-renal tissue-specific local production of vitamin D has been demonstrated in a number of tissues.23 Our lab has previously demonstrated that corneal epithelium, which is directly exposed to the sun in the same manner as the skin, has the enzymatic components and ability to generate and activate vitamin D. The vitamin D receptor (VDR), CYP24A1, CYP27B1, and five different vitamin D metabolites have all been detected in the cornea and anterior segment.24,25 To our knowledge, there have been no published studies examining vitamin D metabolism in corneal keratocytes. Quiescent keratocytes constitute the primary cell type of the corneal stroma and occupy approximately 3% of its volume.26 Corneal keratocytes are involved in the synthesis of collagens, proteoglycans, growth factors and related proteins, and are the primary cell type involved in the corneal stroma wound repair process. A number of protein and lipid-associated growth factors have been shown to influence these processes in keratocytes. The presence and activity of the VDR and vitamin D-associated metabolic enzymes have not been studied in corneal keratocytes.
Related Knowledge Centers
- Cornea
- Corneal Endothelium
- Dendrite
- Mesenchyme
- Neural Crest
- Apoptosis
- Fibroblast
- Stroma of Cornea
- Keratoconus
- Keratan Sulfate