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Purpose: In the literature, immunohistochemistry on cross sections is the main technique used to study protein expression in corneal endothelial cells (ECs), even though this method allows visualization of few ECs, without clear subcellular localization, and is subject to the staining artifacts frequently encountered at tissue borders. We previously proposed several protocols, using fixation in 0.5% paraformaldehyde (PFA) or in methanol, allowing immunostaining on flatmounted corneas for proteins of different cell compartments. In the present study, we further refined the technique by systematically assessing the effect of fixative temperature. Last, we used optimized protocols to further demonstrate the considerable advantages of immunostaining on flatmounted intact corneas: detection of rare cells in large fields of thousands of ECs and epithelial cells, and accurate subcellular localization of given proteins., Methods: The staining of four ubiquitous proteins, ZO-1, hnRNP L, actin, and histone H3, with clearly different subcellular localizations, was analyzed in ECs of organ-cultured corneas. Whole intact human corneas were fixed for 30 min in 0.5% paraformaldehyde or pure methanol at four temperatures (4 °C for PFA, -20 °C for methanol, and 23, 37, and 50 °C for both). Experiments were performed in duplicate and repeated on three corneas. Standardized pictures were analyzed independently by two experts. Second, optimized immunostaining protocols were applied to fresh corneas for three applications: identification of rare cells that express KI67 in the endothelium of specimens with Fuch's endothelial corneal dystrophy (FECD), the precise localization of neural cell adhesion molecules (NCAMs) in normal ECs and of the cytokeratin pair K3/12 and CD44 in normal epithelial cells, and the identification of cells that express S100b in the normal epithelium., Results: Temperature strongly influenced immunostaining quality. There was no ubiquitous protocol, but nevertheless, room temperature may be recommended as first-line temperature during fixation, instead of the conventional -20 °C for methanol and 4 °C for PFA. Further optimization may be required for certain target proteins. Optimized protocols allowed description of two previously unknown findings: the presence of a few proliferating ECs in FECD specimens, suggesting ineffective compensatory mechanisms against premature EC death, and the localization of NCAMs exclusively in the lateral membranes of ECs, showing hexagonal organization at the apical pole and an irregular shape with increasing complexity toward the basal pole. Optimized protocols were also effective for the epithelium, allowing clear localization of cytokeratin 3/12 and CD44 in superficial and basal epithelial cells, respectively. Finally, S100b allowed identification of clusters of epithelial Langerhans cells near the limbus and more centrally., Conclusions: Fixative temperature is a crucial parameter in optimizing immunostaining on flatmounted intact corneas. Whole-tissue overview and precise subcellular staining are significant advantages over conventional immunohistochemistry (IHC) on cross sections. This technique, initially developed for the corneal endothelium, proved equally suitable for the corneal epithelium and could be used for other superficial mono- and multilayered epithelia.

Purpose: To optimize isolation of viable bovine corneal endothelial cells (BCECs), we evaluated the effectiveness of various preparation protocols. This entailed comparing the effects of collagenase A and trypsin in the presence and absence of a Rho kinase inhibitor, Y-27632, on proliferation and tight junctional and cytoskeletal integrity during their expansion., Methods: 5-bromo-2'-deoxyuridine (BrdU) incorporation evaluated cell proliferation. Western blot analysis evaluated F-actin, zonule occludin, and ZO-1 associated nucleic acid binding protein (ZONAB) and RhoA expression. Rho A pulldown assay evaluated Rho A activity., Results: In the trypsin (TrypLE)-prepared BCECs, BrdU incorporation decreased whereas nuclear ZONAB expression increased and became stable from day 3 to 7. In contrast, in the collagenase-A-prepared BCECs, we observed preserved ZO-1 integrity, invariant nuclear ZONAB expression, and dense cortical F-actin expression, and BrdU incorporation was invariant from days 1 to 7. Y-27632 did not increase BrdU incorporation and nuclear ZONAB expression in the TrypLE-prepared and the collagenase-A-prepared BCECs. Moreover, Y-27632 increased irregular cellular morphology and downregulated the expression of ZO-1 in the collagenase-A-prepared BCECs from days 1 to 7. Y-27632 inhibited RhoA activation irrespective of whether the cells were isolated with trypsin or collagenase A., Conclusions: It is preferable to isolate BCECs with collagenase A and expand them without Y-27632. With this protocol, proliferative activity and tight junctional and cytoskeletal integrity are better preserved than if trypsin is used in the presence or absence of Y-27632.

Purpose: Fuchs' endothelial corneal dystrophy (FECD), which affects approximately 5% of the population over 40 in the U.S.A., is a major cause of corneal transplantation. FECD is associated with mutations of a variety of unrelated genes: SLC4A11, COL8A2, TCF8, and LOXHD1. The current pathological description of the dystrophy includes deficiency of corneal endothelium (CE) pump function and induction of the unfolded protein response (UPR). This study aims to determine the contribution of the two mechanisms by assessing the expression levels of (1) seven endothelial ion transporters known to regulate stromal hydration and (2) UPR related genes in a set of six CE samples obtained from FECD patients compared to that of normal controls., Methods: CE samples collected during FECD keratoplasty or from an eye bank (normal control) were transferred into an RNA stabilizing agent and refrigerated. Total RNA from each CE specimen was individually extracted. The expression levels of ion transporters and UPR genes were tested using quantitative real-time (RT) PCR and a UPR specific PCR array, respectively., Results: In normal CE, the comparative expression levels of ion transporters in decreasing order were SLC4A11, Na(+)/K(+) ATPase, pNBCe1, and NHE1, followed by the isoforms of monocarboxylate transporters (MCTs). In FECD samples, Na(+)/K(+) ATPase and MCTs 1 and 4 were significantly downregulated compared to normal controls (p<0.05). The PCR array tested 84 UPR related genes. Data analysis showed upregulation of 39 genes and downregulation of three genes, i.e., approximately 51% of the tested genes had their expression altered in FECD samples with a difference greater than ± twofold regulation. Thirteen of the altered genes showed significant changes (p<0.05). The PCR array results were validated by quantitative RT-PCR., Conclusions: FECD samples had evident UPR with significant changes in the expression of the protein processing pathway genes. The significant downregulation of ion transporters indicates simultaneous compromised CE pump function in Fuchs' dystrophy.

Purpose: To identify critical microRNAs (miRNAs) that play important roles in regulating the aging of corneal endothelial cells in mice aged 10-13 weeks and 2 years., Methods: We collected the corneal endothelia from 30 mice aged 10-13 weeks and 30 mice aged 2 years. The samples were pooled into six groups (Y1, Y2, Y3 and S1, S2, S3). Each group comprised corneal endothelia from 10 mice, and these six groups were used for a genome-wide miRNA microarray study. The expression levels of eight selected miRNAs were further validated independently by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Target genes were predicted using a computational approach due to their base-pairing rules between miRNA and messenger RNA target sites. The locations of binding sequences were within the target's 3' untranslated regions (UTR), and the conservation of target binding sequences occurred within related genomes. Additional gene ontology and signaling pathway analyses were performed using bioinformatics tools., Results: Twenty-seven miRNAs (7 upregulated and 20 downregulated) were found to be differentially expressed (fold change >2, p value <0.05) in the corneal endothelia of adult and old mice. The qRT-PCR results confirmed the differential expression of eight miRNAs between the corneal endothelia of adult and old mice. A computational approach demonstrated that the target genes of the differentially expressed miRNAs might be involved in several signaling pathways, including the glutamatergic synapse pathway (p=0.000313), the phosphatidylinositol signaling pathway (p=0.00197), the neurotrophin signaling pathway (p=0.00687), the transforming growth factor-beta signaling pathway (p=0.0143), and oxidative phosphorylation (p=0.0223)., Conclusions: Our study identified miRNAs that are differentially expressed in the corneal endothelium during aging for the first time. We also identified fluctuations in the expression of these specific miRNAs that may be related to age-specific changes. Understanding miRNA expression and interactions in tissues such as the cornea may aid in the understanding of the basic and pathophysiological processes of age-related ocular pathologies.

Purpose: The aim of this prospective study was to evaluate whether blending two kinds of biomaterials, chitosan and polycaprolactone (PCL), can be used as scaffold and carrier for growth and differentiation of corneal endothelial cells (CECs)., Methods: A transparent, biocompatible carrier with cultured CECs on scaffold would be a perfect replacement graft. In the initial part of experiment, for essential and biocompatible test, chitosan and PCL were evaluated respectively and blended in various proportions by coating. In the later part of this study, for evaluation of potential application, homogenous solutions of 25%, 50%, and 75% PCL compositions were attempted to structure blend membranes., Results: Chitosan, PCL 25, PCL 50, and PCL 75 blends could maintain transparency of culturing substrata. BCECs were found to be reached confluence successfully after 7 days on PCL 25, PCL 50, and PCL 75. The expression of tight junction and extracellular matrix protein were observed as well. Alternatively, only PCL 25 could make blend membrane with enough strength during preparation for carrier in culture. On this blend membrane, the growth pattern and phenotype of BCECs could be observed well., Conclusions: A ratio of 75:25 (chitosan:PCL) blends showed enough mechanical properties as well as suitable support for cellular activity in cultivating BCECs. Thus, a novel methodology of biodegradable carrier from chitosan and PCL has potential to be a good replacement scaffold for raising CECs for clinical transplantation.

Purpose: Determine cyclin-dependent kinase inhibitor 2A (p16(Ink4a)) and polycomb ring finger oncogene (Bmi1) expression in corneal endothelium samples from different age groups and test whether the expression of p16(INK4a) and Bmi1 are associated with endothelial cellular senescence in human cornea., Methods: Samples were selected from an eyebank of healthy human corneal endothelial cells (HCECs). Donor human corneas were divided into three age-groups: age ≤30 years, 30-50 years and ≥50 years. The expression of p16(INK4a) and Bmil were analyzed by real-time PCR, immunohistochemistry, and immunofluorescence., Results: Through real-time PCR, we detected less than threefold decreases in Bmi1 expression and greater than fivefold increases in p16(INK4a) expression associated with aging. Bmi1 expression was significantly down-regulated with increasing donor age. The number of p16(INK4a)-positive cells was significantly higher and the number of Bmi1-positive cells was significantly lower in older donors compared to the younger age groups. Our immunohistochemistry experiments showed that the expression of p16(INK4a) in older donors was stronger than that in younger donors and the expression of Bmi1 in older donors was weaker than that in younger donors. Results from both the immunohistochemistry and real-time PCR experiments confirmed increased expression of p16(INK4a) and decreased expression of Bmi1 with age in HCECs. Additionally, the results of immunofluorescence double-staining for p16(INK4a) and Bmi1 further validated the immunocytochemistry and real-time PCR results., Conclusions: Our data are the first to demonstrate that high expression of p16(INK4a) and low expression of Bmi1 are associated with endothelial cellular senescence in human cornea. Our findings are not just for cornea transplantation but also for a better understanding of the cornea senescence and the process of aging in this specific human organ.

Purpose: En face observation of corneal endothelial cells (ECs) using flat-mounted whole corneas is theoretically much more informative than observation of cross-sections that show only a few cells. Nevertheless, it is not widespread for immunolocalization (IL) of proteins, probably because the endothelium, a superficial monolayer, behaves neither like a tissue in immunohistochemistry (IHC) nor like a cell culture in immunocytochemistry (ICC). In our study we optimized IL for ECs of flat-mounted human corneas to study the expression of cell cycle-related proteins., Methods: We systematically screened 15 fixation and five antigen retrieval (AR) methods on 118 human fresh or stored corneas (organ culture at 31 °C), followed by conventional immunofluorescence labeling. First, in an attempt to define a universal protocol, we selected combinations able to correctly localize four proteins that are perfectly defined in ECs (zonula occludens-1 [ZO-1] and actin) or ubiquitous (heterogeneous nuclear ribonucleoprotein L [hnRNP L] and histone H3). Second, we screened protocols adapted to the revelation of 9 cell cycle proteins: Ki67, proliferating cell nuclear antigen (PCNA), minichromosome maintenance protein 2 (MCM2), cyclin D1, cyclin E, cyclin A, p16(Ink4a), p21(Cip1) and p27(Kip1). Primary antibody controls (positive controls) were performed on both epithelial cells of the same, simultaneously-stained whole corneas, and by ICC on human ECs in in vitro non-confluent cultures. Both controls are known to contain proliferating cells. IL efficiency was evaluated by two observers in a masked fashion. Correct localization at optical microscopy level in ECs was define as clear labeling with no background, homogeneous staining, agreement with previous works on ECs and/or protein functions, as well as a meaningful IL in proliferating cells of both controls., Results: The common fixation with 4% formaldehyde (gold standard for IHC) failed to reveal 12 of the 13 proteins. In contrast, they were all revealed using either 0.5% formaldehyde at room temperature (RT) during 30 min alone or followed by AR with sodium dodecyl sulfate or trypsin, or pure methanol for 30 min at RT. Individual optimization was nevertheless often required to optimize the labeling. Ki67 was absent in both fresh and stored corneas, whereas PCNA was found in the nucleus, and MCM2 in the cytoplasm, of all ECs. Cyclin D1 was found in the cytoplasm in a paranuclear pattern much more visible after corneal storage. Cyclin E and cyclin A were respectively nuclear and cytoplasmic, unmodified by storage. P21 was not found in ECs with three different antibodies. P16 and p27 were exclusively nuclear, unmodified by storage., Conclusions: IL in ECs of flat-mounted whole human corneas requires a specific sample preparation, especially to avoid overfixation with aldehydes that probably easily masks epitopes. En face observation allows easy analysis of labeling pattern within the endothelial layer and clear subcellular localization, neither of which had previously been described for PCNA, MCM2, or cyclin D1.

Purpose: Penetrating keratoplasty has been the mainstay for the treatment of blindness and is the most common form of tissue transplantation worldwide. Due to significant rates of rejection, treatment of immunological transplant reactions is of wide interest. Recently in a mouse model, the overexpression of indoeleamine 2,3 dioxigenase (IDO) was led to an extension in corneal allograft survival. L-kynurenine is a tryptophan metabolite, which may render activated T-cells apoptotic and therefore might modulate an allogenous transplant reaction. The function of L-kynurenine in the human cornea remains unclear. We analyzed the expression levels of IDO in human corneal endothelial cells (HCECs) and downstream tryptophan/kynurenine mechanisms in cell culture., Methods: An immunological activation profile was determined in proliferation assays of monocytes from healthy donors. Reversed-phase high pressure liquid chromatography (HPLC), western blot, real time polymerase chain reaction (PCR), and microarray analyses were used. The expression of IDO and immunological infiltration of rejected human corneal allografts (n=12) were analyzed by immunohistochemistry., Results: We found IDO and an associated tryptophan/kynurenine transporter protein exchange mechanism upregulated by inflammatory cytokines in HCECs. The inhibition of T-cell proliferation might depend on rapid delivery of the tryptophan metabolite, L-kynurenine, to the local corneal environment. Microarray analysis gives evidence that the large amino acid transporter 1 (LAT1) transporter protein is responsible for this mechanism., Conclusions: Our data support that adequate levels of functional L-kynurenine might contribute to the maintenance of a relative immune privilege in the ocular anterior chamber, thereby contributing to the preservation of corneal allogeneic cells.

Purpose: To analyze the involvement of the corneal endothelium in uveitis to better understand the formation mechanisms and the keratic precipitate composition. In vivo confocal microscopy images were correlated with ex vivo immunostaining of corneal endothelium from rat eyes with endotoxin-induced uveitis (EIU)., Methods: EIU was induced in Lewis rats by lipopolysaccharide (LPS) injection. Slit-lamp examination and in vivo confocal microscopy were performed 6, 24, 48, 72, and 96 h after the LPS injection. One group of rats was killed at 24 h and the other rats at 96 h. Immunohistochemistry on corneal endothelium using antibodies to intercellular adhesion molecule (ICAM-1), phalloidin, CD68 (anti-macrophage), MCA967 (anti-granulocyte), T cell receptor alpha/beta (TCR alpha/beta; anti-lymphocyte), zonula occludens-1 (ZO-1), and occludin was performed on flat-mount corneas and was analyzed using a three dimensional (3D) laser confocal microscope., Results: In vivo confocal microscopy showed numerous hyperreflective round dots on the corneal endothelium, in the anterior chamber, and in the anterior stroma corresponding to inflammatory cells with a maximum at 24 h after the injection and detectable until the 96th hour. Upon immunostaining, corneal endothelial cells in rats with EIU overexpressed ICAM-1. ZO-1 and occludin had a lower endothelial expression and more heterogeneous distribution in EIU rats than in controls, showing disruption of endothelial cell junctions. Compared to controls, CD68, MCA967, and TCR alpha/beta expression was observed in corneas in rats with EIU. The two techniques showed a circular peripheral network of corneal vessels derived from a large circumferential vascular structure resembling the major arterial circle of iris where the inflammatory cells marginalized to infiltrate the anterior stroma., Conclusions: The correlation between in vivo confocal microscopy and ex vivo immunostaining helped to better understand in vivo confocal microscopy images. The two new techniques applied here were very effective and complementary in evaluating the corneal endothelium involvement in EIU. Based on these findings, in vivo confocal microscopy in clinical practice could be very helpful to better analyze keratic precipitates and corneal modifications in patients with uveitis.

Purpose: To examine karyotype changes in cultured human corneal endothelial cells (HCECs)., Methods: HCECs with Descemet's membrane were removed from 20 donors of various ages (range, 2-77 years; average, 43.7+/-26.4 years) and cultured on dishes coated with extracellular matrix produced by bovine corneal endothelial cells (BCECs). Karyotype changes were examined by G-band karyotyping of HCECs at the third passage from 12 donors and the fifth passage from 16 donors. The number of chromosomes was analyzed in 40-50 cells from the third and fifth passages of each HCEC preparation. A detailed karyotype analysis of 10-16 cells from the third and fifth passages of each HCEC preparation was performed. The frequency of aneuploid cells per case (the number of abnormal cells divided by the total number of cells examined at metaphase) was tested for correlation with age by Spearman's correlation analysis., Results: At the third passage, five cases (41.7%) showed an almost normal karyotype, and five cases (41.7%) showed sex chromosome loss. One case (8.3%) showed chromosome 21 trisomy. At the fifth passage, five cases (31.3%) showed an almost normal karyotype, and four cases (25%) showed sex chromosome loss. Three cases (18.8%) showed chromosome 8 trisomy, and one case (6.3%) showed chromosome 21 trisomy. Donor age and the frequency of aneuploidy had a statistically significant correlation at the fifth passage (R=0.653, p=0.042)., Conclusions: Donor age and the frequency of aneuploidy have a positive correlation in cultured HCECs at the fifth passage. Therefore, HCECs for clinical therapies should be obtained from donors as young as possible. Karyotyping cultured HCECs is crucial before clinical application.

Purpose: To investigate the expression of p16(INK4a), p21(WAF1/CIP1), p27(KIP1), and p53 in human corneal endothelial cell (HCEC) senescence ex vivo at various donor ages., Methods: Residual corneal tissues obtained after penetrating keratoplasty were used in this study. Age, death-to-preservation interval, and preservation-to-surgery interval of the donors were recorded. Corneal endothelial cell survival and density were evaluated by trypan blue and alizarin red staining immediately after keratoplasty. Fresh frozen sections of donor corneas at various ages (18, 33, 54, and 68 years) were immunostained in situ. Total RNA extracted from age groups of 20, 30, 40, 50, and 60 years was evaluated by reverse-transcriptase polymerase chain reaction (PCR) to reveal the expression of the senescence-related genes, p16(INK4a), p21(WAF1/CIP1), p27(KIP1), and p53, in HCECs. Total RNA extracted from 20-, 24-, 26-, 30-, 50-, 55-, 56-, and 60-year-old donor groups was subjected to real-time PCR analysis for measurement of gene expression. The results of the young (< or =30 years) and the old (> or = 50 years) were compared by the unpaired t-test. Ex vivo senescence of HCECs from the donors at various ages (9, 17, 23, 57, 65, and 67 years) was observed by senescence-associated beta-galactosidase activity (SA-beta-Gal) staining at pH 6.0., Results: The mean endothelial cell density of the donor corneas was 2,391.4+/-84.6 cells/mm(2), and the survival rate of the endothelial cells was 84.4%+/-5.3%. Hematoxylin and eosin staining showed normal structures of the corneal epithelium, stroma, and endothelium. The expression and nuclear localization of p16(INK4a), p21(WAF1/CIP1), p27(KIP1), and p53 in HCECs were confirmed by immunohistochemistry in situ. Reverse transcriptase PCR examination showed positive target bands of each gene at each age group. An age-related increase in p16(INK4a) expression was observed by real-time PCR (p=0.014). There was no significant difference in the expression levels of p21(WAF1/CIP1), p27(KIP1), and p53 between the young and old donors (p=0.875, 0.472, and 0.430, respectively). Strong SA-beta-Gal activity was observed in the endothelial cells of the old donors while there was weak and little-to-no blue staining in the endothelia from the young., Conclusions: The population of HCECs exhibiting senescence-like characteristics increases with age. p16(INK4a), p21(WAF1/CIP1), p27(KIP1), and p53 are expressed in HCECs despite donor ages. The p16(INK4a) signal pathway might play a key role in the process of senescence in HCECs.

Purpose: To establish a baseline protein fingerprint of cultured human corneal endothelial cells (HCEC), to determine whether the protein profiles exhibit age-related differences, and to identify proteins differentially expressed in HCEC cultured from young and older donors., Methods: Corneas were obtained from five young (<30 years old) and five older donors (>50 years old). HCEC were cultured, and protein was extracted from confluent passage 3 cells. Extracts from each age group were pooled to form two samples. Proteins were separated on two-dimensional (2-D) gels and stained with SyproRuby. Resultant images were compared to identify protein spots that were either similarly expressed or differentially expressed by at least twofold. Protein spots were then identified by matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry., Results: Protein spots were well resolved, and patterns were reproducible on 2-D gels using either pH 3-10 or pH 4-7 IPG strips. Two-dimensional gels prepared with pH 4-7 IPG strips were used for differential display analysis, which was reproduced on three separate pairs of gels. MALDI-TOF identified 58 proteins with similar expression; 30 proteins were expressed twofold higher in HCEC from young donors; five proteins were expressed twofold higher in cells from older donors; and 10 proteins were identified in gels from young donors that did not match in gels from older donors. Several proteins expressed at higher levels in younger donors support metabolic activity, protect against oxidative damage, or mediate protein folding or degradation., Conclusions: This is the first proteomic comparison of proteins expressed in HCEC cultured from young and older donors. Although restricted to proteins with isoelectric points between pH 4.0 and pH 7.0, the data obtained represent an initial step in the investigation of molecular mechanisms that underlie physiologically important age-related differences in cultured HCEC, including differences that may affect proliferative capacity. Results indicate that HCEC from older donors exhibit reduced expression of proteins that support important cellular functions such as metabolism, antioxidant protection, protein folding, and protein degradation. These differences may affect the ability to consistently obtain a sufficient number of healthy cultured HCEC for use in preparing bioengineered endothelium as an alternative method for the treatment of endothelial dysfunction.

Purpose: To isolate and characterize primary corneal endothelial cells (CEC) from wild type and transgenic mice to facilitate the study of their properties in vitro., Methods: CEC were isolated from wild type or transgenic-immortomice corneas. The Descemet's membrane was gently peeled from the periphery of the cornea towards the central region and placed into wells of a 96 well tissue culture plate coated with fibronectin in growth medium. Cells that grew out were trypsinized and expanded on fibronectin-coated wells and used for further characterization. CEC were evaluated for expression and localization of specific markers and adhesion molecules by FACS analysis and indirect immunofluorescence staining. The migration properties of CEC were evaluated using a scratch wound and transwell assay, while their ability to undergo capillary morphogenesis was assessed on Matrigel., Results: Isolation of CEC from transgenic mice has been somewhat challenging and not previously reported. Here we describe a method for isolation of CEC from wild type and thrombospondin-1 deficient (TSP1-/-) immortomice. Our results indicate that nearly 100% of selected cells express B4-lectin and VE-cadherin, but not PECAM-1. These cells were successfully passaged and maintained in culture for several months without a significant loss in expression of these markers. The wild type CEC, like vascular EC, organized and formed a capillary-like cell network on Matrigel. The ability of the CEC from TSP1-/- mice to form such a network was somewhat compromised. This may be attributed, at least in part, to altered adhesive and migratory properties of these cells., Conclusions: The CEC can be readily obtained from wild type and transgenic mice, which facilitate the comparison and identification of the physiologic role of specific genes in CEC function.

Purpose: Human corneal endothelium exhibits both age-related and topographical differences in relative proliferative capacity and in senescence characteristics. The purpose of these studies was to compare telomere lengths in human corneal endothelial cells (HCEC) from the central and peripheral areas of corneas from young and older donors to determine whether these changes may be due to replicative senescence or to stress-induced premature senescence., Methods: Pairs of corneas from five young (<30 years old) and six older donors (>65 years old) were separated into central and peripheral areas using a 9.5 mm diameter trephine to remove scleral tissue and a 6.0 mm diameter trephine to mark the central-peripheral boundary. One of the pair of corneas was cut into quarters and stained with a peptide nucleic acid (PNA)/fluorescein isothiocyanate (PNA/FITC) probe that specifically binds to telomere repeats. HCEC from the central (0-6.0 mm) and peripheral areas (6.0-9.5 mm) were isolated from the second cornea, mounted on slides by Cytospin, and stained with the PNA/FITC probe. Fluorescence confocal microscopy was used to obtain digital images. The average FITC intensity of nuclei was compared between the central and peripheral areas within and between the two age groups. Ccl185 and 1301 cells were analyzed as controls. Student's unpaired t-test was used to determine the statistical significance of the data., Results: Average FITC intensity from the central endothelium was 205.8+/-4.2 (younger) and 194.2+/-10.5 (older) and from the peripheral endothelium was 208.1+/-9.3 (younger) and 195.9+/-10.8 (older). Average intensity of single cells isolated from central endothelium was 113.9+/-31.1 (younger) and 107.9+/-26.1 (older) and from the periphery was 109.9+/-12.0 (younger) and 106.9+/-32.4 (older). Average FITC intensity of Ccl185 cells and 1301 cells was 50.5+/-5.0 and 206.9+/-19.4, respectively. Comparison of the results indicates no statistically significant difference between the central and peripheral areas within each group or between the young and older age group., Conclusions: Results indicate that the age-related and topographical reduction in relative proliferative capacity and senescence characteristics observed in HCEC are not due to replicative senescence caused by critically short telomeres but implicate stress-induced premature senescence as a cause of these clinically important changes.

Purpose: To determine whether the promyelocytic leukemia zinc finger (PLZF) protein, a transcriptional repressor and negative regulator during cell cycling, plays a role in the proliferation of cultured human corneal endothelial cells (HCECs)., Methods: The expressions of the mRNA and the protein of PLZF were determined by real-time PCR and western blot analysis, respectively. The changes in the expression of the PLZF gene of cultured HCECs were investigated at different times after cell-cell contacts were disrupted by incubation with EDTA. The cell proliferation rate was assessed with a real-time cell electronic sensing (RT-CES) system after cultured HCECs were infected with either PLZF or LacZ encoding adenovirus vector (Ad-PLZF or Ad-LacZ). The PLZF-regulating genes were analyzed by DNA microarray analysis in cultured HCECs infected with Ad-PLZF., Results: The expression of the mRNA of PLZF was first detected when the cultured HCECs became confluent, and the relative amount of PLZF mRNA continued to increase for up to 5 days as the cell-cell contacts were formed more firmly. On the other hand, the expression of the mRNA of PLZF decreased about 20 fold 3 h after EDTA exposure, and gradually returned to the original level as the cell-cell contacts were reformed at 72 h after the exposure. The assessment using the RT-CES system showed that the proliferation of cultured HCECs was inhibited for up to 72 h when infected by Ad-PLZF. DNA microarray analysis revealed that the transforming growth factor-beta stimulated clone 22 (TSC-22) gene was up-regulated by 2.32 fold when infected by Ad-PLZF., Conclusions: These findings indicate that the expression of PLZF in HCECs is closely related to the formation of cell-cell contacts, and that PLZF may play a role in suppressing their proliferation.

Purpose: The well-known reluctance of human corneal endothelial cells (HCECs) to divide has continually intrigued investigators. Related to this, the discovery of an increased endothelial cell population in the periphery of the human cornea has prompted an investigation for evidence of the existence of stem-like cells in the endothelial periphery. Showing that stem cells or transient amplifying cells may exist in the periphery might explain the origin of HCECs and indicate a source for these cells in wound repair. In addition, these cells might be of value in culturing or as a source for the synthesis of artificial corneas., Methods: Human corneas with attached scleral rims were obtained from eye banks and were assayed for telomerase activity and BrdU (bromodeoxyridine) incorporation to determine, respectively, the presence of a stem-like cell marker and replicative activity. In the case of telomerase activity, the tissues were divided into central, intermediate and peripheral areas by the use of trephines. BrdU staining (using alkaline phosphatase bound secondary antibody) was performed on whole corneas plus scleral rims exposed to BrdU antibodies on the endothelial side whereas BrdU fluorescence (using fluorescein bound secondary antibody) was obtained from transverse sections of the these tissues by the same procedure. Some corneas were wounded to determine whether the wounded areas stimulated BrdU (by staining or fluorescence) followed by the synthesis of transforming growth factor beta (TGFbeta). The latter was determined by quantitative ELISA. Rabbit corneas were also assayed for BrdU incorporation to compare their evidence of cell division with that of humans., Results: After dividing corneas into central, intermediate, and peripheral sections, the dissected endothelial tissues exhibited positive telomerase activity in the peripheral and intermediate sections. No activity was observed in the central endothelial tissues or the limbus between the trabecular meshwork and Schwalbe's line. BrdU staining with alkaline phosphatase was occasionally observed in the wounded area's human corneal endothelial cells after wounding. When BrdU fluorescence assays were made on corneal transverse sections with fluorescein, fluorescence occurred in an area just at and adjacent to the trabecular meshwork, but was not seen at the corneal endothelium. After wounding, BrdU fluorescence extended into the corneal endothelium. TGF-beta levels were increased in fluids bathing the endothelium following wounding, but the increases lagged behind the wounding event., Conclusions: It is suggested stem-like cells may be sequestered in a niche at the junctional region where the corneal endothelial cells and the trabecular meshwork come together. These putative stem cells may supply new cells for both the corneal endothelium and the trabeculae. Evidence suggests that cells from this area migrate (perhaps as transient amplifying cells) to the endothelial periphery and, perhaps, to wounded areas of the corneal endothelium when needed. The migration may not be constant and may be age dependent.

Purpose: To determine the protein and mRNA expression of p53, p63, and p73 in central and peripheral human corneal endothelial cells. Since these proteins are known to be involved in the regulation of cell division, this study seeks information about their influence in regulating cell proliferation in the human corneal endothelium., Methods: Human donor corneas were separated into central and peripheral sections. The endothelial tissue from these samples was dissected and samples were analyzed for mRNA transcription of p53, transactivating p63 (TAp63), delta N p63 (DeltaNp63), transactivating p73 (TAp73), and delta N p73 (DeltaNp73) via the reverse transcriptase-polymerase chain reaction (RT-PCR). Additional samples were analyzed for p53, p63, and p73 protein expression via SDS-PAGE, western blotting, and immunodetection. Frozen corneal sections were immunostained for p53 and analyzed via fluorescence microscopy., Results: p53 and TAp63 mRNA and protein expression were detected in central and peripheral human corneal endothelium. p53 and TAp63 protein expression were greater in central than in peripheral tissue. DeltaNp63 and all isoforms of p73 were not detected in either central or peripheral corneal endothelium., Conclusions: p53 is expressed in both peripheral and central human corneal endothelium, although it is more highly expressed in the central endothelium. Similarly, TAp63 is more highly expressed in central rather than in peripheral endothelium. This suggests that the peripheral endothelium may have more potential for cell division than the central endothelium. DeltaNp63, a stem cell marker, was not detected in the corneal endothelium. Neither the TAp73 nor the DeltaNp73 isoforms were detected in either central or peripheral human corneal endothelium.

Purpose: The ocular surface, composed of the conjunctiva and the cornea, is essential for vision. Its integrity depends on numerous molecular and cellular processes such as proliferation, differentiation, apoptosis, adhesion, and extracellular matrix homeostasis, whose deregulation can induce ophthalmological pathologies. The Krüppel-like transcription factors (KLFs) family is made up of 15 C2H2 zinc-finger proteins involved in vertebrate development and able to control cell proliferation, growth, and differentiation. In order to better define their respective roles in the human ocular surface, we decided to determine their pattern of expression in ocular tissues. We then focused on the expression of KLF4 and some of its target genes to establish KLF4's biological activities in human ocular surface., Methods: Firstly, total mRNA was extracted from human total cornea, conjunctiva, corneal epithelial cells (primary culture and established cell line), corneal keratocytes (primary culture), corneal endothelial cells (established cell line), and conjunctival epithelial cells (established cell line) and submitted to RT-PCR experiments in order to determine the expression patterns of the different KLFs. Secondly, KLF4 protein localization was visualized by immunofluorescence assays at tissue and cell levels. Finally, KLF4 target genes (endoglin, ornithine decarboxylase) mRNA expression levels were determined by semi-quantitative RT-PCR, after KLF4 transient transfection in human corneal epithelium (HCE) cells., Results: We detected the presence of twelve transcripts of KLFs in the cornea (KLF2, KLF3, KLF4, KLF5, KLF6, KLF7, KLF8, KLF10, KLF11, KLF12, KLF13, and KLF16) and eight in the conjunctiva (KLF2, KLF3, KLF4, KLF6, KLF7, KLF10, KLF11, and KLF12). Under our conditions, the transcripts encoding KLF1 and KLF9 were never detected. Specific expression patterns of each KLF were also determined for the major cellular components of the human cornea and conjunctiva. KLF4 immunolocalization assays indicated its presence in both the cytoplasmic and nuclear compartments of conjunctival and corneal cells. KLF4 transient overexpression in HCE cells down regulated both endoglin and ODC mRNA levels., Conclusions: For the first time, we established the presence of a KLF network in the human ocular surface and illustrated the conservation of KLF4's biological properties in a corneal derived epithelial cell line.

Purpose: To determine if aquaporin-1 expression is decreased in human and mouse corneal endothelial dysfunction., Methods: Immunohistochemistry with anti-aquaporin 1 antibody and confocal microscopy were used to study a case series of human corneal specimens, and a mouse model of corneal endothelial injury was created with injection of sterile hot water into the anterior chamber with a 33 gauge needle. Western blotting of mouse and human corneas was used to provide confirmatory evidence., Results: Aquaporin-1 was found to be expressed in normal human cornea and decreased in human corneas with endothelial disease but not in human corneas with non-endothelial corneal disease. Aquaporin-1 was also found to be reduced in mouse corneas subjected to corneal endothelial injury. Both results were confirmed by western blot analysis., Conclusions: Corneal endothelial injury is associated with decreased aquaporin-1 expression.

Purpose: Corneal endothelial cells (CECs) undergo endothelial to mesenchymal transformation (EMT) in response to FGF-2 stimulation. One phenotypic change that occurs during EMT is a change in cell shape from polygonal to elongated fibroblast-like cells. We investigated whether FGF-2 plays a role in this morphogenetic pathway by reorganizing actin cytoskeleton through the actions of phosphatidylinositol (PI) 3-kinase and the Ras related Rho family of small guanosine triphosphatases (GTPases)., Methods: Cell morphology was analyzed using phase contrast microscopy, and the organization of actin cytoskeleton and focal adhesions were analyzed by immunofluorescent staining. Expression of vinculin and beta-actin was determined by immunoblot analysis. Pharmacologic inhibitors (LY294002, C3 exoenzyme, Y27632, or PD98059) or neutralizing antibody to FGF-2, respectively, were used to block PI 3-kinase, Rho, Rho associated kinase, extracellular signal regulated kinase, or FGF-2 pathways., Results: CECs treated with FGF-2 became smaller and lost their characteristic polygonal cell morphology. Such cell shape change was completely blocked by treatment with LY294002. CECs in culture have abundant stress fibers that are oriented radially across the cell. However, FGF-2 caused a loss of these stress fibers and focal adhesions. The modulated cells contained a cortical actin ring while LY294002 completely abolished this action of FGF-2 on actin cytoskeleton. Treatment of cells with C3 exoenzyme or Y27632 in the presence of FGF-2 induced spindle shaped cells with prominent pseudopodia which were rapidly formed upon exposure to the inhibitor. The expression level of vinculin was found to be similar in all experimental conditions but vinculin was mostly translocated to the cytoplasm in response to FGF-2 stimulation. CECs plated on Matrigel matrix demonstrated findings similar to those from cells plated on the conventional culture dishes, except that Matrigel facilitated the formation of pseudopodia. We further investigated in vivo actin organization using organ cultures of corneal endothelium (CE) on Descemet's membrane. The contact inhibited endothelial monolayer demonstrated a circumferential actin ring, and no stress fibers were observed. When CE was treated with FGF-2, a half population of CE lost its characteristic contact inhibited cobblestone morphology. Actin cortex was greatly disrupted in these modulated cells. Both neutralizing antibody to FGF-2 and LY294002 completely impeded the modulating activity of FGF-2 on the endothelial monolayer. When CE was simultaneously treated with FGF-2 and Y27632, the circumferential actin cortex was greatly disrupted and the endothelial monolayer was transformed into multi-layers of fibroblastic cells containing pseudopodia. Both LY294002 and neutralizing antibody to FGF-2 antagonized the actions of FGF-2 and Y27632., Conclusions: These data indicate that CECs in culture have constitutively active Rho activity as evidenced by stress fiber formation and that PI 3-kinase negatively regulates the formation of stress fibers and focal adhesions, perhaps antagonizing the Rho pathways. Formation of pseudopodia in response to FGF-2 and Y27632 may suggest that the Rho/ROCK pathway negatively regulates Cdc42.

Purpose: Procollagen I is synthesized and intracellularly degraded in corneal endothelial cells (CEC), whereas type IV and VIII collagens are secreted into Descemet's membrane. In our previous study, we demonstrated that procollagen I synthesized by CEC is improperly folded and that the molecule was largely colocalized with protein disulfide isomerase (PDI) within the endoplasmic reticulum (ER). In the present study, we further investigated whether the alpha-subunit of prolyl 4-hydroxylase (P4Halpha) and glucose regulatory protein/immunoglobulin heavy chain binding protein (Grp78/BiP) were also involved in ER retention of procollagen I in CEC., Methods: Immunocytochemical analysis was performed to determine the colocalization of procollagen I with molecular chaprones. Protein synthesis was measured by immunoblot analysis and the association between proteins was determined by coimmunoprecipitation followed by immunoblot analysis. mRNA was quantitated using RT-PCR., Results: To study the interaction of procollagen I with certain molecular chaperones involved in the collagen biosynthetic pathway, we determined whether procollagen I colocalized with P4Halpha and Grp78/Bip, and then compared this molecular chaperone colocalization with their association with type IV collagen. Procollagen I was colocalized with either P4Halpha or Grp78/Bip to a much lesser degree than type IV collagen was colocalized with these same ER proteins. Colocalization between the molecular chaperones demonstrated that P4Halpha and Grp78/Bip were largely colocalized in the peripheral region of the ER, whereas colocalization of P4Halpha and PDI was mostly limited to a small region of the ER. When cells were treated with alpha,alpha-dipyridyl, the inhibitor did not affect the colocalization profiles of collagens with the molecular chaperones. However, the inhibitor markedly increased colocalization of P4Halpha and PDI, but it significantly decreased colocalization between P4Halpha and Grp78/Bip. When synthesis of the molecular chaperones was compared between CEC and corneal stromal fibroblasts (CSF), more Grp78/Bip and PDI were produced by CEC than by CSF. On the other hand, expression of Hsp47 was lower in CEC than it was in CSF. Coimmunoprecipitation was used to compare the association of P4Halpha or Grp78/Bip with collagens in CEC and CSF. The association of collagens (regardless of type) with P4Halpha or Grp78/Bip was much higher in CEC than in CSF. When the association of collagen molecules with respective molecular chaperones was compared in CEC, the degree of association between Grp78/Bip and procollagen I was similar to that between the molecular chaperone and type IV collagen. On the other hand, the degree of association between P4Halpha and type IV collagen was much higher than that between P4Halpha and procollagen I., Conclusions: These data suggest that procollagen I and type IV collagen may use different molecular chaperones in the ER, thus targeting their distinctive destinations.

Purpose: To determine whether TGF-beta2 exerts inhibitory action in a density dependent manner in primary, first passage, and second passage corneal endothelial cells (CEC)., Methods: Fifty percent confluent cultures were used for actively cycling cells and monolayers were used as contact inhibited cultures. Half of the experiments were performed in cells treated with TGF-beta2 at 10 ng/ml for 24 h. Subcellular localization of cyclin dependent kinase 4 (Cdk4), p27Kip1 (p27), and phosphorylated p27 (pp27) was determined by immunofluorescent staining followed by confocal laser microscopic analysis. Expression of proteins were analyzed by immunoblotting., Results: Before colocalization between Cdk4 and p27 was studied, the two proteins were respectively stained, either in growing cells for the presence of Cdk4 or in contact inhibited cultures for the presence of p27. Nuclear Cdk4 was observed in FGF-2 treated cells while nuclear staining of Cdk4 was lost in mitogen deprived or TGF-beta2 treated cells. On the other hand, a strong positive staining of nuclear p27 was observed in growth down regulated conditions, which was completely lost in growth up regulated conditions. When cells were double stained with Cdk4 and p27 antibodies, actively cycling cells contained nuclear Cdk4. Less than 10% of the primary cells were positive for Cdk4 staining, whereas all of the second passage CEC contained nuclear Cdk4. Conversely, p27 was not detected in actively cycling cells in either primary or passaged cells. Contact inhibited cells demonstrated nuclear p27 staining in all cells, but only a few cells were positive for nuclear Cdk4. Nuclear Cdk4 was absent when the actively cycling cells were treated with TGF-beta2, whereas TGF-beta2 did not induce the expression of nuclear p27 in the same cultures. In contact inhibited cells, TGF-beta2 did not affect the staining profiles of p27. In the first passage CEC, TGF-beta2 slightly increased the number of cells that were positive for nuclear Cdk4. When the effect of TGF-beta2 at the level of protein synthesis was determined, TGF-beta2 markedly downregulated Cdk4 synthesis and slightly upregulated p27 synthesis in actively cycling cells. On the other hand, TGF-beta2 did not exert the same effect on Cdk4 synthesis in contact inhibited cells as it did on actively cycling cells. Contact inhibited cells contained a high level of p27, and TGF-beta2 slightly upregulated p27 synthesis in these cells. When phosphorylated p27 was determined to be present, the nuclei of both actively cycling and contact inhibited cells contained phosphorylated p27 in the nuclei, regardless of the passage numbers. TGF-beta2 inhibited phosphorylation of p27 in actively cycling cells, but it had no effect on phosphorylation of p27 in contact inhibited cells., Conclusions: These data suggest that Cdk4 and p27 expression is density dependent, and TGF-beta2 exerted its activity on actively cycling cells. In these cells, TGF-beta2 downregulated Cdk4 expression and prevented the phosphorylation of p27, which is a prerequisite for nuclear export of the inhibitor molecule for degradation. Thus, TGF-beta2 inhibits the G1/S transition while it maintains p27 in an active form in the nuclei during the exponential growth cell stage.

Purpose: To determine the subcellular localization of 18 kDa FGF-2 after synthesis and before secretion into the extracellular matrix., Methods: Corneal endothelial cells (CEC) were transfected with an expression vector coding for green fluorescent protein (GFP) and 18 kDa FGF-2. Expression of the fusion protein was determined by immunoblot analysis and the subcellular localization of the fusion protein was examined by immunocytochemical analysis., Results: When the expression of the fusion protein was determined by immunoblot analysis, the expressed fusion protein had a molecular weight of 45 kDa, resulting from the 27 kDa GFP and 18 kDa FGF-2. Following a 90 min exposure of cells to the vector, the expressed 18 kDa FGF-2 was completely translocated to the nucleus within a 24 h incubation. When cells were further incubated for another 24 h, one-half of the fusion protein was retro-transported from the nucleus to the cytoplasm, largely to the membrane and focal adhesion site, while the other half remained in the nucleus. During a 72 h incubation, the fusion protein was completely translocated to the cytoplasm, where it was diffusely distributed and its staining potential was greatly lost. Transfected cells showed both a slight increase in cell proliferation and a down-regulation in the expression of the high affinity receptors of FGF., Conclusions: These results indicate that the 18 kDa FGF-2 is directly translocated from its synthetic site to the nucleus. The nuclear 18 kDa FGF-2 is then retro-transported to membrane/focal adhesion sites, after which the molecule may be secreted. When 18 kDa FGF-2 remains in the nucleus, there is a slight stimulatory activity of cell proliferation and a down-regulation of its receptor. These data suggest an intracellular action of 18 kDa FGF-2 through mechanisms independent of the receptor-mediated signaling pathways.

Purpose: To investigate the extracellular matrix macromolecules found in Descemet's membrane and in retrocorneal fibrous membrane (RCFM), and to examine whether the corneal endothelium has the capacity to produce both basement and non-basement membrane phenotypes., Methods: Rabbit corneas with and without RCFM were analyzed by immunofluorescence using antibodies to 8 different collagens (basement membrane collagens: types IV and VIII; fibrillar collagens: types I and III; interfibrillar collagens: type VI and two spliced variant forms of type XII and one anchoring fiber: type VII), proteoglycans (perlecan and decorin), (beta)ig-h3 and laminin-1., Results: Normal corneal endothelium stains positively for all of the tested collagen types except type VII collagen. On the other hand, Descemet's membrane reacts positively only to the type IV collagen antibody. When non-collagenous components in normal cornea were examined, corneal endothelium stained positively for perlecan, decorin, (beta)ig-h3 and laminin, whereas Descemet's membrane staining for these proteins was negative. When collagenous components of RCFM were examined, RCFM stained positively for all of the tested collagen types except type IV collagen. When non-collagenous components of RCFM were examined, RCFM demonstrated a strong positive staining with decorin, (beta)ig-h3 and laminin, while perlecan staining was weak., Conclusions: These observations suggest that corneal endothelium is able to produce both basement membrane phenotypes and non-basement membrane, fibrillar phenotypes. This in vivo study confirms our in vitro model of endothelial mesenchymal transformation, in which corneal endothelial cells are transformed to fibroblasts that are responsible for fibrosis.

Purpose: To determine the cellular localization of the Src homology (SH)2 and SH3 domains of PLC-gamma1 and their cytoplasmic binding partners, living corneal endothelial cells were microinjected with the fusion proteins containing SH domains., Methods: Fusion proteins were prepared from plasmid vectors, and the fusion proteins containing SH2-SH2 [(SH2)2], SH2-SH2-SH3 [(SH2)2-SH3] or SH3 were isolated using affinity chromatography. Following microinjection, immunolocalization was analyzed using confocal laser microscope., Results: Microinjected SH domains were targeted to the subcellular location following stimulation with FGF-2: the SH3 domain appeared to be targeted to cytoskeleton; the (SH2)2 domain showed a dual localization in cytoplasm and plasma membrane; the (SH2)2-SH3 domain was predominantly localized at membrane and perinuclear sites. In the absence of stimulation by FGF-2, the microinjected fusion proteins remained at the injection sites. When cytoplasmic binding partners were determined by double-staining, the SH3 domain demonstrated colocalization with vinculin: the staining profile of the SH3 domain was identical to that of vinculin, which demonstrates characteristic punctated profiles. The punctated staining of SH3 disappears toward the basal membrane, while that of vinculin remains in all confocal optical sections. On the other hand, some fraction of the (SH2)2 domain was colocalized with FGF receptor at the membrane site. When PLC-gamma1 and F-actin were double-stained, the endogenous PLC-gamma1 demonstrated a diffuse cytoplasmic staining and/or perinuclear staining, while phalloidin staining demonstrated that all cells have filamentous cytoplasmic distribution of F-actin., Conclusions: These findings indicate that the SH3 domain directs PLC-gamma1 to bind to vinculin and that the SH2 domains may mediate the binding of PLC-gamma1 to receptor tyrosine kinase. Furthermore, they suggest that phosphorylation is not required for targeting of PLC-gamma1 to membrane or cytoskeleton sites.

Purpose: Type I collagen is post-translationally regulated in corneal endothelial cells (CEC): CEC synthesize procollagen I and degrade it intracellularly. We investigated whether there is a Hsp47-independent pathway during intracellular trafficking of procollagen I., Methods: Specific inhibitors were used to block intracellular transport of procollagen I and Hsp47. Immunocytochemical analysis was performed to determine the intracellular localization of the proteins of interest., Results: When cells were treated with alpha,alpha'-dipyridyl, this specific inhibitor for collagen promoted retention in the endoplasmic reticulum (ER) of some of the underhydroxylated procollagen I, which was colocalized with Hsp47 in CEC. At the same time, another fraction of the alpha,alpha'-dipyridyl-induced underhydroxylated procollagen I was not located in the ER. When CEC were treated with brefeldin A, procollagen I and Hsp47 demonstrated a high degree of colocalization at the ER, whereas the inhibitor had less of an effect on the compartmentalization of procollagen I and prolyl 4-hydroxylase. When CEC were treated with either monensin or bafilomycin A1, procollagen I and Hsp47 were not colocalized: procollagen I was mostly localized at the Golgi area, while Hsp47 predominantly showed ER distribution. When colocalization of procollagen I and prolyl 4-hydroxylase was examined, a major population of procollagen I was not colocalized with prolyl 4-hydroxylase in the ER., Conclusions: These results indicate that some procollagen I and Hsp47 travel together from the ER to the cis-Golgi compartment and that a major population of procollagen I that may not be properly hydroxylated may be destroyed intracellularly via the Hsp47-independent pathway in CEC.

Purpose: Fibroblast growth factor 2 (FGF-2) induces endothelial-mesenchymal modulation in corneal endothelial cells, including stimulation of cell proliferation and cell shape change and induction of fibrillar collagen. In the present study, we investigated whether FGF-2 uses distinct signaling pathways for individual biological activities., Methods: Specific metabolic inhibitors were used to block cell proliferation, while reversion of cellular morphology (modulated with FGF-2) was determined using specific antibodies and inhibitors. Immunocytochemical analysis was performed to identify any changes observed in the cytoskeleton in relation to cell shape. Association of cytoskeleton molecules with phosphatidylinositol 3-kinase was determined using co-precipitation. Cell proliferation was assayed using a colorimetric method for determining the number of viable cells., Results: The fibroblastic morphology induced by FGF-2 reverted to a polygonal shape in cells treated with anti-FGF-2 antibody, anti-phosphatidylinositol 3-kinase antibody, LY294002, and genistein, while anti-phospholipase C gamma1 antibody did not to reverse the modulated cell morphology. Cell proliferation mediated by FGF-2 was blocked by metabolic inhibitors (genistein, LY294002 and wortmannin); genistein inhibited FGF-mediated cell proliferation in a dose-response manner and had a maximum inhibition of 80% at 100 microM, while inhibitors of phosphatidylinositol 3-kinase had less inhibitory effect than did genistein. When cytoskeleton proteins were examined, the characteristic punctated staining profiles of vinculin observed in normal cells were maintained in fibroblastic corneal endothelial cells treated with FGF-2. The inhibitors that cause reversion of cell shape also demonstrated the punctated staining potential. Likewise, the staining profiles of alpha-actinin and smooth muscle alpha-actin were not altered, regardless of cell shape. Filamentous actin and alpha-actinin were co-localized to the cytoskeleton and phosphatidylinositol 3-kinase was associated with the cytoskeleton, regardless of cell shape., Conclusions: These findings indicate that FGF-2 uses distinct and/or dual signaling pathways for individual biological activities.