Biomedical subjects

B Y Yue

Publications and source records attributed to B Y Yue.

At least 19 recordsLinked to original sources

PubMed2001

Effects of protein kinase inhibitor, HA1077, on intraocular pressure and outflow facility in rabbit eyes.

OBJECTIVE: To elucidate the roles of protein kinase in regulating the intraocular pressure (IOP) and outflow facility in rabbit eyes. MATERIALS AND METHODS: A protein kinase inhibitor, 1-(5-isoquinolinesulfonyl)-homopiperazine (HA1077), was used. The IOP and the outflow facility were measured before and after topical, intracameral, or intravitreal administration of HA1077 in rabbits. Western blot analysis was performed to detect the 20-kd light chain of myosin in human trabecular meshwork (TM) cells and bovine ciliary muscle (CM) tissues. The cell morphologic condition and distribution of actin filaments and vinculin in TM cells were studied using cell biology techniques. Carbachol-induced contraction of isolated bovine CM strips following administration of HA1077 was examined in a perfusion chamber. RESULTS: In rabbit eyes, the administration of HA1077 resulted in a significant decrease in IOP in a dose-dependent manner. An increased outflow facility was also observed. Western blot analysis revealed the presence of 20-kd light chain of myosin in human TM cells and bovine CM tissues. In cultured human TM cells, exposure to HA1077 disrupted actin bundles and impaired focal adhesion formation. In addition HA1077 showed relaxation of bovine CM strips. CONCLUSIONS: Use of HA1077 caused a reduction in IOP and an increase in the outflow facility. The results of in vitro experiments suggest that the IOP-lowering effects of HA1077 may be related to the altered cellular behavior of TM cells and relaxation of CM contraction. The results of these studies suggested that protein kinase inhibitors have the potential to be developed into a treatment modality for glaucoma.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed2001

Cell density regulated expression of transcription factor Sp1 in corneal stromal cultures.

Sp1, a ubiquitously expressed transcription factor, has been implicated to have a role in cell differentiation and cell proliferation. In keratoconus, a corneal disease characterized by thinning and scarring of the central cornea, Sp1 is found up-regulated. In the present study, we examined the expression of Sp1 in stromal cells cultured from normal human and keratoconus-afflicted corneas and evaluated the influence of varying cell densities. Immunohistochemical staining, Western blotting and electrophoretic mobility shift assays indicated that in both normal human and keratoconus cultures, Sp1 protein levels and binding activities increased with the density of cells. The basal level of Sp1 in keratoconus cultures was higher than that in normals. These results demonstrate a marked density mediated up-regulation of Sp1 in corneal stromal cells, suggesting that the Sp1 expression may be regulated by differentiation states of the cells in the cornea. In addition, cells from keratoconus corneas in vitro appear to carry and retain the Sp1 abnormality as in vivo. The Sp1 defect may be an inborn error in keratoconus.

Adult↗

PubMed2001

Expression of type XII collagen and hemidesmosome-associated proteins in keratoconus corneas.

PURPOSE: Keratoconus is a disease characterized by thinning of the central and paracentral cornea and scarring in advanced cases. This study was performed to examine the expression of type XII collagen, proteins associated with hemidesmosomes, and beta1 integrin in keratoconus corneas. METHODS: Corneal buttons were collected from normal subjects and patients with keratoconus and other corneal diseases. Immunofluorescence staining was performed on frozen sections for type XII collagen, bullous pemphigoid antigen (BP180), and integrin subunits alpha6, beta4, and beta1. RESULTS: To varying degrees, all proteins examined were expressed in normal human corneas. The staining intensity of type XII collagen was diminished in keratoconus corneas in the epithelial basement membrane zone and the stromal matrix. No significant variation was found in either the staining patterns or intensities for BP180, or integrins alpha6, beta4, and beta1. CONCLUSIONS: The level of type XII collagen was reduced in the epithelial basement membrane zone and stromal matrices in keratoconus corneas. These alterations may affect critical interactions of the corneal epithelium with the under-lying basement membrane, and cell-matrix interactions and matrix organization in the stroma.

Adolescent↗

PubMed2001

Effects of rho-associated protein kinase inhibitor Y-27632 on intraocular pressure and outflow facility.

PURPOSE: To elucidate the roles of Rho-associated protein kinase (ROCK) in regulating intraocular pressure (IOP) and outflow facility in the rabbit eye. METHODS: A specific ROCK inhibitor Y-27632 was used. The IOP, the outflow facility, and the pupil diameter were determined before and after the topical, intracameral, or intravitreal administration of Y-27632 in rabbits. Western blot analysis was used to identify specific ROCK isoform in human trabecular meshwork (TM) cells and bovine ciliary muscle (CM) tissues. The cell morphology and distribution of actin filaments and vinculin in TM cells were studied by cell biology techniques. Carbachol (Cch)-induced contraction of isolated bovine CM strips after administration of Y-27632 was measured in a perfusion chamber. RESULTS: In rabbit eyes, administration of Y-27632 resulted in a significant decrease in IOP in a dose-dependent manner. An increase of the outflow facility and pupil size dilation was also observed in Y-27632-treated eyes. Western blot analysis revealed the presence of p160ROCK in human TM cells and bovine CM tissues. In cultured human TM cells, exposure to Y-27632 caused retraction and rounding of cell bodies as well as disruption of actin bundles and impairment of focal adhesion formation. Y-27632 in addition inhibited Cch-induced contraction of isolated bovine CM strips. CONCLUSIONS: Administration of Y-27632 caused a reduction in IOP and an increase in the outflow facility. The in vitro experiments suggest that the IOP-lowering effects of Y-27632 may be related to the altered cellular behavior of TM cells and relaxation of CM contraction. These studies suggest that ROCK inhibitors may have great potential to be developed for treatment of glaucoma and other ocular diseases.

Actins↗

PubMed2001

Involvement of Sp1 elements in the promoter activity of genes affected in keratoconus.

PURPOSE: Keratoconus is a progressive disease that thins and scars the corneal stroma. In keratoconus corneas, levels of degradative enzymes, including lysosomal acid phosphatase (LAP) and cathepsin B, are elevated, and those of the inhibitors alpha1-proteinase inhibitor (alpha 1-PI) and alpha 2-macroglobulin (alpha 2-M) are reduced, especially in the epithelial layer. An increased expression of the transcription factor Sp1 was also demonstrated. The role of Sp1 in regulation of the genes affected in keratoconus was examined in this study. METHODS: DNA segments, containing 5'-flanking promoter sequences of the alpha 1-PI, LAP, cathepsin B, and alpha 2-M genes were ligated into the secreted alkaline phosphatase (SEAP) reporter gene vector. These constructs, along with the pSV beta-galactosidase control vector, were transfected into cultured human corneal epithelial and stromal cells and skin fibroblasts. Cotransfection with the Sp1 expression vector was performed in parallel. SEAP and beta-galactosidase enzyme activities were assayed. RESULTS: In corneal epithelial cells, as in stromal cells, alpha 1-PI promoter activity was suppressed by cotransfection of pPacSp1. The LAP, cathepsin B, and alpha 2-M promoters were functional in corneal cells, whereas activities of these promoters were much lower in skin fibroblasts. Cotransfection experiments indicated that the up- or downregulation of LAP, cathepsin B, and alpha 2-M observed in keratoconus-affected corneas was not mediated by Sp1. CONCLUSIONS: These results support the theory that the corneal epithelium, along with the stroma, is involved in keratoconus. An upstream role of Sp1 is indicated and the Sp1-mediated downregulation of the alpha 1-PI gene may be a key event in the disease development.

Acid Phosphatase↗

PubMed2001

Keratocan expression is increased in the stroma of keratoconus corneas.

BACKGROUND: Keratoconus is a noninflammatory disease characterized by thinning and scarring of the central portion of the cornea. The etiology is unclear. In this study, we sought to identify mRNAs that are differentially expressed in the stroma of keratoconus corneas in comparison to those of corneas from normal individuals and patients with other corneal diseases. MATERIALS AND METHODS: Total RNA was isolated from the stromal layer of normal human, keratoconus, and pseudophakic bullous keratopathy corneas. cDNA was synthesized and PCR-select subtractive hybridization experiments were performed. The differentially expressed genes noted were verified by dot blot analysis, cloned, and sequenced. Immunohistochemical staining, in situ hybridization, and/or reverse transcription polymerase chain reaction were used to assess expression of the identified genes at protein and/or mRNA levels in normal, keratoconus, and other diseased corneas. RESULTS: A number of genes were found to be up-regulated in keratoconus specimens. These included heat shock protein 90, decorin, fibronectin, ferritin heavy chain, and keratocan. Among them, keratocan mRNA transcript and protein were demonstrated to be expressed at a higher level specifically in the keratoconus stroma. CONCLUSIONS: Keratocan expression in the stoma was increased in keratoconus corneas. This up-regulation appears to be keratoconus specific. Keratocan is one of the three keratan sulfate proteoglycans in the cornea speculated to be important for structure of the stromal matrix and maintenance of corneal transparency. The overexpressed keratocan may conceivably alter the fibrillogenesis in the stroma, leading to structural defects and contributing to the development of keratoconus.

Adolescent↗

PubMed2000

Signal transduction mediated by adhesion of human trabecular meshwork cells to extracellular matrix.

In this study we investigated the signaling event induced by adhesion of human trabecular meshwork (TM) cells to extracellular matrix (ECM) elements such as fibronectin. The role of tyrosine phosphorylation in adhesion was evaluated. A number of intracellular entities involved in the adhesion-mediated pathways were identified. For the experiments, human TM cells were seeded onto fibronectin- or polylysine (negative control)-coated plates. Fifteen, 30, 90 and 240 min after the seeding, cell lysates were collected. Immunoblotting analysis revealed that tyrosine phosphorylation occurred within 15 min of adhesion of TM cells to fibronectin and the level increased with time. The phosphotyrosyl proteins had molecular masses 25-220 kDa. A much lower level of tyrosine phosphorylation was observed when cells were plated on polylysine. Immunoprecipitation experiments indicated that the phosphotyrosine-containing proteins included focal adhesion kinase, paxillin, phosphatidylinositol 3-kinase and mitogen activated protein kinase. Within 30 min of adherence to fibronectin, human TM cells immunostained for paxillin and phosphotyrosine and exhibited prominent focal contacts. When treated with tyrosine kinase inhibitors genistein and herbimycin A and a protein kinase C (PKC) pseudosubstrate peptide inhibitor, cell adhesion to fibronectin was compromised and focal contact formation was limited. These results demonstrated that in human TM cells, tyrosine kinase was activated upon their adherence to fibronectin. PKC also appeared to play a role in modulation of the cell-matrix adhesion process. The current study provides insight into the signaling pathways that are linked to the ECM-induced events in TM cells. Elucidation of the hierarchy of signal responses may help develop strategies manipulating the cell-matrix interactions in the TM system.

Adult↗

PubMed2000

Normal expression levels of cathepsins, protease inhibitors, and Sp1 in conjunctival tissues from patients with keratoconus.

PURPOSE: In keratoconus corneas, it has been shown that levels of degradative enzymes and transcription factor Sp1 are elevated and those of inhibitors are reduced, especially in the epithelial layer. This study is to determine whether the biochemical abnormalities identified in corneas also exist in conjunctival tissues. METHODS: Conjunctival tissues were collected from normal subjects and from patients with keratoconus, senile cataract, and other corneal diseases. Immunohistochemical staining for cathepsins B and G, alpha 1-proteinase inhibitor, alpha 2-macro-globulin and Sp1 was performed. RESULTS: The epithelium of all conjunctival specimens showed immunoreactivity toward the antibodies. The staining for cathepsins B and G, and the inhibitors was mostly cytoplasmic, while that for Sp1 was nuclear. The staining intensity in keratoconus specimens was all within normal range. CONCLUSIONS: These results suggest that the abnormalities in cathepsins B and G, protease inhibitors and Sp1 identified in keratoconus corneas are not manifested in the conjunctiva. Keratoconus appears to be a disease localized to the cornea.

Adolescent↗

PubMed2000

Ultrastructural localization of myocilin in human trabecular meshwork cells and tissues.

We examined ultrastructurally the localization of myocilin (formerly called trabecular meshwork inducible glucocorticoid response, or TIGR) protein in cultured human trabecular meshwork (TM) cells and in normal human TM tissues. The TM, a specialized tissue located at the chamber angle of the eye, is believed to be responsible for the development of glaucoma. The myocilin gene has been directly linked to both juvenile and primary open-angle glaucomas, and multiple mutations have been identified. Human TM cells were treated with 0.1 mM of dexamethasone (DEX) to induce myocilin expression. This protein was immunolocalized by colloidal gold electron microscopy using an anti-human myocilin polyclonal antibody. Double labeling with different sizes of gold particles was also performed with additional monoclonal antibodies specific for cell organelles and structures. In both DEX-treated and untreated cultured cells, myocilin was associated with mitochondria, cytoplasmic filaments, and vesicles. In TM tissues, myocilin was localized to mitochondria and cytoplasmic filaments of TM cells, elastic-like fibers in trabecular beams, and extracellular matrices in the juxtacanalicular region. These results indicate that myocilin is localized both intracellularly and extracellularly at multiple sites. This protein may exert diverse biological functions at different sites.

Adult↗

PubMed1999

Oxidative stress affects cytoskeletal structure and cell-matrix interactions in cells from an ocular tissue: the trabecular meshwork.

The trabecular meshwork (TM) is a specialized eye tissue that regulates the aqueous humor outflow and controls intraocular pressure. Cells in this tissue are essential for maintenance of the outflow system. Disturbance of the TM cell status by insults such as oxidative stress may lead to elevation of the intraocular pressure and development of glaucoma. In the present study, we investigated the effect of oxidative stress on the adhesion of human TM cells to extracellular matrix (ECM) proteins. Treatment with 1 mM of H2O2 for 10 or 30 min did not affect cell viability, whereas the adhesion of TM cells to fibronectin, laminin, and collagen types I and IV was significantly reduced. Phalloidin and immunostaining also revealed reorganization of actin and vimentin structures. The level of integrins alpha5beta1, alphavbeta3, and beta1 was not altered, although the distribution of paxillin and focal adhesion kinase in focal contacts was reduced. Concomitantly, the level of transcription factor NF-kappaB was enhanced by the H2O2 treatment. Nuclear extracts of the treated cells also contained a heightened NF-kappaB binding activity. These changes persisted for up to 6 h after the H2O2 treatment but were partially recovered by 24 h. We concluded that under sublethal oxidative stress conditions, the TM cell adhesion to the ECM was impaired. The short-term loss of cell-matrix adhesiveness may be related to the rearrangement of cytoskeletal structures. Extensive and repeated oxidative stress in vivo may result in reduced TM cell adhesion, leading to cell loss, compromised TM integrity, and pathologic consequences.

Actins↗

PubMed1999

Alteration of cytoskeletal structure, integrin distribution, and migratory activity by phagocytic challenge in cells from an ocular tissue--the trabecular meshwork.

The trabecular meshwork is a specialized tissue in the anterior chamber of the eye that regulates the aqueous humor outflow and controls the intraocular pressure. Cells in the trabecular meshwork are believed to be essential for maintenance of the outflow system, and their malfunctioning may lead to elevation of intraocular pressure and development of glaucoma. These cells are avid phagocytes. Using an in vitro tissue culture system, we have previously shown that bovine trabecular meshwork cells exhibited a short-term loss of cell-matrix adhesiveness after exposure to latex microspheres. The current study showed that 4 h after phagocytosis, the cytoskeletal structure in trabecular meshwork cells was disrupted, the formation of focal contact formation was limited, and the cellular migratory activity was increased. These in vitro responses paralleled those that occur in vivo. By 24 h, all the changes demonstrated returned to normal. Our data suggest that the short-term loss in cell-matrix cohesiveness observed after phagocytic challenge may be related to the reorganization of cytoskeletal structures and the decline of focal contact formation. The altered cell migration may also be interlinked.

Animals↗

PubMed1999

Collagen fibrillar network in the optic nerve head of normal monkey eyes and monkey eyes with laser-induced glaucoma--a scanning electron microscopic study.

PURPOSE: To examine the three-dimensional organization of collagen fibrils in the lamina cribrosa of normal monkey eyes and monkey eyes with laser-induced glaucoma. METHODS: Intraocular pressure elevation and glaucomatous optic discs were obtained in one eye of three adult monkeys by repeated applications of argon laser to the chamber angle. The monkey eyes were enucleated, and the collagen fibrillar network was investigated by scanning electron microscopy after cell maceration with 10% sodium hydroxide and conductive staining. RESULTS: In normal monkey eyes, round to oval shaped regular laminar pores through which axon bundles exited were observed in the lamina cribrosa. The straight, column-like pores or openings were formed by multilayered laminar plates that aligned vertically in parallel with the optic nerves. The surface of the laminar plates was covered by delicate, loosely arranged collagen fibrils. The inner surface of the pores was smooth, made up of well-packed collagen fibers. In glaucomatous eyes, the laminar pores were clogged by tightened collagen fibrils. The inner surface of the pores was irregular, and the pores were narrowed or distorted. CONCLUSIONS: Alterations in the three-dimensional organization of collagen fibrils were demonstrated in the optic nerve head of glaucomatous monkey eyes. The architectural changes may affect the flexibility and resilience required of the lamina cribrosa in supporting optic nerve fibers.

Animals↗

PubMed1999

Expression of integrin receptors in the human trabecular meshwork.

PURPOSE: To examine the expression of integrin receptors in the human trabecular meshwork. METHODS: The expression of integrins in human tissues was visualized by immunohistochemical staining using integrin-specific antibodies. Immunoprecipitation was performed after biotin labeling of cell surface proteins. Reverse transcriptase-polymerase chain reaction was used to detect the presence of mRNA species for integrin subunits. RESULTS: Human trabecular meshwork tissues obtained from donors 2 to 65 years old stained positively for integrins alpha1, alpha3, alpha4, alpha5, alpha6, alphav, beta1, beta3, beta4 and beta5. The staining was observed mostly around the edges of trabecular beams in association with trabecular meshwork cells. The staining intensity did not appear to vary with donor age. In addition, immunoprecipitation of tissue extracts revealed the presence of integrin alpha2 and confirmed the absence of beta2. Results from polymerase chain reactions were consistent with these findings. CONCLUSIONS: A spectrum of integrin receptors that may have important roles in the cell-matrix interactions are demonstrated in the human trabecular meshwork. The repertoire identified in tissues is similar to that found in cultured cells except that the beta4 expression in tissues is lost in cultures.

Adult↗

PubMed1999

Levels of alpha1-proteinase inhibitor and alpha2-macroglobulin in the tear film of patients with keratoconus.

PURPOSE: Levels of alpha1-proteinase inhibitor and alpha2-macroglobulin in the tear film of patients with keratoconus were measured to elucidate their possible roles in the pathogenesis of keratoconus. METHODS: Tear samples were collected from 15 keratoconus patients and 14 age-similar human control subjects. Levels of alpha1-proteinase inhibitor and alpha2-macroglobulin in each tear sample were quantified and compared between the two groups. RESULTS: Mean values for alpha1-proteinase inhibitor were 101.0+/-35.5 and 106.1+/-41.7 ng/microg protein for the keratoconus and control groups, respectively. The corresponding mean values for alpha2-macroglobulin were 13.5+/-6.8 and 14.8+/-7.5 ng/microg protein. Neither inhibitor showed a statistically significant difference between the keratoconus and control specimens. Subset analysis to evaluate the effects of contact lens wear and the presence of a graft in the fellow eye did not reveal a statistically significant difference. CONCLUSION: The tear film of patients with keratoconus contains normal levels of protease inhibitors. Therefore, the tear film may not be a source of the reduced inhibitor levels shown in the corneas of patients with keratoconus.

Adolescent↗

PubMed1998

Involvement of Sp1 elements in the promoter activity of the alpha1-proteinase inhibitor gene.

The transcripts of the alpha1-proteinase inhibitor in the cornea are different from those in hepatocytes and monocytes, suggesting that alpha1-proteinase inhibitor gene transcription may respond to different cell-specific regulatory mechanisms. Although information on alpha1-proteinase inhibitor gene structure has been obtained, little is known regarding the cis- and trans-acting factors that regulate its expression. In this study, we cloned and sequenced a 2. 7-kilobase 5'-flanking region upstream from the corneal transcription initiation site of the gene, demonstrated functional promoter activity, and identified the regulatory elements. Sequencing revealed that the 5'-flanking element was highly G/C-rich in regions proximal to the corneal transcription start site. DNase I footprinting located 10 potential Sp1-binding sites between nucleotides -1519 and +44. The putative promoter was functional in human corneal stromal cells, but not in human skin, scleral, and conjunctival fibroblasts, suggesting that the promoter may be corneal cell-specific. The promoter activity in the corneal cells was repressed when Sp1 was coexpressed. In the cornea-thinning disease keratoconus, down-regulation of the alpha1-proteinase inhibitor gene and increased Sp1 expression have both been demonstrated. The current results suggest that down-regulation of the inhibitor in keratoconus corneas may be related directly to overexpression of the Sp1 gene. This information may help elucidate the molecular pathways leading to the altered alpha1-proteinase inhibitor expression in keratoconus.

Base Sequence↗

PubMed1998

Three-dimensional scanning electron microscopic study of keratoconus corneas.

OBJECTIVE: To examine the 3-dimensional collagen fibril organization in the Bowman layer of keratoconus corneas. METHODS: Eight keratoconus corneas, 8 corneas with other diseases, and 5 normal human corneas were studied. A cell maceration method in combination with scanning electron microscopy was used to examine the collagen network in the Bowman layer. RESULTS: In normal corneas, the surface of the Bowman layer was smooth and collagen fibrils were regularly arranged. By contrast, sharply edged defects in the Bowman layer were found in keratoconus corneas. Lattice-like configurations of the ruptured Bowman layer and collagenous scar tissue were observed, to varying degrees, in all keratoconus corneas examined. None of the other diseased corneas exhibited the ruptures. CONCLUSIONS: Scanning electron microscopy demonstrated alterations in the Bowman layer specific to keratoconus. Fragmentation of the Bowman layer may be an early change leading to keratoconus conditions.

Adolescent↗

PubMed1998

Effects of ascorbic acid on levels of fibronectin, laminin and collagen type 1 in bovine trabecular meshwork in organ culture.

PURPOSE: Fibronectin, laminin and collagen type I are important extracellular matrix products of trabecular meshwork cells. This study was performed to examine the effects of ascorbic acid, a significant component in the aqueous humor, on the levels of these proteins in trabecular meshwork cells maintained in organ culture. METHODS: The anterior segment of freshly enucleated bovine eyes was perfused in a modified organ culture system. Three cultures were set up simultaneously. One received serum-free medium containing 100 micrograms/ml of ascorbic acid, one received 250 micrograms/ml of ascorbic acid and one served as a control. After 72 h, the tissues were processed for paraffin sections and immunostaining was conducted using an avidin-biotin-peroxidase complex method. Western blot and dot blot assays were performed on tissue extracts. RESULTS: Compared with the controls, the staining for fibronectin and laminin was markedly enhanced in trabecular meshwork tissues treated with both concentrations of ascorbic acid. Increased collagen type I production by trabecular meshwork cells was also demonstrated in the presence of ascorbic acid. Western blot and dot blot results confirmed the immunostaining findings. CONCLUSIONS: Ascorbic acid promotes production of fibronectin, laminin and collagen type I by trabecular meshwork cells. The organ culture results are consistent with those obtained previously from tissue culture studies.

Animals↗

PubMed1998

Expression of degradative enzymes and protease inhibitors in corneas with keratoconus.

PURPOSE: Keratoconus is characterized by thinning and scarring of the central region of the cornea. Previous research showed that, in corneas obtained from patients with keratoconus, lysosomal enzyme activities are elevated, whereas levels of protease inhibitors such as alpha1-proteinase inhibitor are reduced. This study was undertaken to examine further the expression of a spectrum of proteolytic enzymes and protease inhibitors. METHODS: Corneal buttons were collected from patients with keratoconus, healthy subjects, and patients with other corneal diseases. Immunohistochemical staining was performed on paraffin sections. Enzymatic assays and western blot analysis were carried out for cathepsins B and G. In addition, an in situ zymography procedure was used to examine the gelatin- and casein-digesting activities in corneas with keratoconus. RESULTS: An enhanced staining was found with antibodies to cathepsins B and G. Enzymatic assays and western blotting confirmed that the levels of these two enzymes were elevated in corneas with keratoconus. No alteration was noted with any of the matrix metalloproteinase (MMP) family members and other enzymes and inhibitors examined, although in situ zymography did indicate an increase in net gelatin- and casein-digesting activities in corneas with keratoconus. These activities were mostly abolished by inhibitors for serine and cysteine proteinases, but not by those for MMPs and aspartic proteinases. CONCLUSIONS: Levels of cathepsins B and G are increased in corneas with keratoconus. These enzymes may contribute to the heightened in situ gelatin- and casein-digesting activities, leading to abnormalities in keratoconus.

Adolescent↗