Expression regulation of hyaluronan synthase in corneal endothelial cells

PURPOSE

Our previous study showed that hyaluronan synthase (HAS), the enzyme protein of hyaluronan (HA) biosynthesis, is expressed in ocular tissues including the corneal endothelium. In the current study, the mechanism that regulates HAS expression in bovine corneal endothelial cells (BCECs) was investigated.

METHODS

Cultured BCECs were used. HAS expression in BCECs at the mRNA level was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis. The effects of transforming growth factor (TGF)-beta and platelet-derived growth factor (PDGF)-BB on HAS expression were examined by quantitative RT-PCR. The involvement of the Smad family (intracellular signal transducer of TGF-beta) was also investigated. The expression of HAS in BCECs at the protein level was confirmed by immunocytochemistry and Western blot analysis.

RESULTS

Three HAS isoforms in BCECs were expressed at the mRNA level. The transcriptional sizes of each HAS in BCECs were 4.9 kb for HAS1, 2.8 kb for HAS2, and 1.6 kb for HAS3. The expression of HAS2 at the mRNA level was stimulated by TGF-beta1 and/or PDGF-BB treatment. In contrast, HAS1 and HAS3 expression was not affected by these growth factors. The additive effects of TGF-beta1 and PDGF-BB were observed in the stimulation of the expression levels of HAS2. HAS2 upregulation by these growth factors was also detected by Western blot analysis. The stimulation of the expression of HAS2 at the mRNA level by TGF-beta was accelerated by the overexpression of Smad2, Smad3, and Smad4 and inhibited by that of Smad7, all of which were confirmed to be involved in the signal transduction from TGF-beta through HAS expression.

CONCLUSIONS

Although three HAS isoforms were expressed in the corneal endothelial cells, the expression of HAS2 was upregulated by TGF-beta1 and/or PDGF-BB. HAS2 expression was regulated by TGF-beta through Smad family members.

Effects of perfluorophenanthrene on the human corneal endothelium

PURPOSE

To evaluate long term effects of perfluorophenanthrene (C12F24), a perfluorocarbon fluid, in the anterior chamber of the human eye, where residual perfluorophenanthrene was retained in the eye postoperatively.

METHODS

Slit-lamp microscopic and specular microscopic examinations of 4 eyes of 4 patients were performed. All the eyes were operated for complicated retinal detachment and they were aphakic at the end of the operations. Mean follow-up period was 10 months (6-16 months).

RESULTS

Perfluorophenanthrene was seen in the anterior chamber in the first or second day postoperatively as a single drop. In the third week, postoperatively, the first signs of splitting the perfluorophenanthrene (fish egging phenomena) was observed. There was no sign of corneal or anterior segment toxicity with the slit lamp microscopic examinations and the intraocular pressure was within normal limits during the follow-up period in all eyes. However, some structural changes of the corneal endothelium were shown by specular microscopy. Decreased endothelial cell density, a reversed illumination pattern in which the normally dark cellular boundaries appear bright and intracytoplasmic light reflecting bodies were signs of cellular damage at the contact sites whereas no significant changes were seen at non contact sites.

CONCLUSION

Residual perfluorophenanthrene in the anterior chamber does not induce gross corneal damage or ocular inflammation, although structural changes indicating the damage of the corneal endothelium, can be shown by specular microscopy at the contact sites. Corneal endothelial changes seem to arise from a contact-dependent effect of the perfluorophenanthrene.

Irradiation for inhibition of endothelial cell growth in vitro

The clinical effect of ionising radiation on ocular neovascularisations is controversial, not only because of the variety of treatment modalities. The aim of our study was to investigate an experimental model which allows to evaluate radiation parameters and to study the mechanism of the inhibitory effect on neoangiogenesis. In vitro experiments were performed using human umbilical vein endothelial cells and human corneal keratocytes. The cells were irradiated with different doses of photon beam radiation and counted daily after treatment. Cell cultures confirmed the efficiency of irradiation in inhibiting proliferation of vascular endothelial cells. Radiosensitivity was shown to be higher in vascular endothelial cells than in corneal stromal keratocytes. This might be helpful in investigating therapy parameters for treating ocular neovascularisations, as well as underlying mechanisms.

Phakic posterior chamber intraocular lens for the correction of anisometropia and treatment of amblyopia

PURPOSE

To assess the potential visual benefits of posterior chamber phakic intraocular lens implants in eyes of children with anisometropic amblyopia.

METHODS

In a prospective study, three girls 9, 14, and 18 years old with high anisometropia and deep amblyopia were included in this study. The phakic posterior chamber intraocular lens (ICL; STAAR Surgical AG, Nidau, Switzerland) was used to correct the anisometropia. This intraocular lens was inserted in the anterior chamber through a 3.0-mm temporal clear cornea incision and manipulated into the posterior chamber using an iris manipulator. A peripheral iridectomy was performed using the Ocutome Probe (Storz; Premiere, St. Louis, Missouri). Local therapy with corticosteroids and antibiotics were prescribed for 2 weeks, and patients were followed regularly for a period of 6 to 9 months.

RESULTS

In the three amblyopic eyes of the three patients, the preoperative best-corrected visual acuity of 6/30, 6/60, and 6/30 improved, to 6/7.5 (20/25), 6/30 (20/100), and 6/15 (20/50), respectively, 6 months after the surgery. Binocular functions with development of fusional abilities and stereopsis were observed in two of these patients after the intraocular lens implantation. In the third patient, the fusional abilities developed only after surgical correction of the exotropia. The intraocular pressure remained within normal limits, and there was no significant change in the corneal endothelial cell count during the period of follow-up. No major intraoperative or postoperative complications were observed, except for a temporary pigment dispersion.

CONCLUSIONS

Implantation of phakic posterior chamber intraocular lenses may be beneficial for the treatment of amblyopia in children with anisometropia. Although additional cases and long-term follow-up observations are necessary, it appears that amblyopia may be overcome by the use of posterior chamber phakic intraocular lens implants, even in eyes of children beyond the age generally considered to be responsive to anti-amblyopic treatment.

EDTA: a promoter of proliferation in human corneal endothelium

PURPOSE

To determine whether it is possible to induce proliferation in the endothelium of older donor corneas by treatment of the intact monolayer with EDTA.

METHODS

Corneas from donors 52 to 75 years of age were obtained from an eye bank and were usually cut in quarters to increase sample size. The effect of EDTA dose (0.02-2.0 mg/ml) and incubation time (6, 30, and 60 minutes) on endothelial cell-cell contacts was evaluated by staining for ZO-1, a cell junction marker. Cell death was tested by a commercial live-dead assay. Corneal pieces were incubated for 0, 24, 48, or 60 hours in culture medium (M-199, 10% fetal bovine serum, 10 ng/ml epidermal growth factor, 20 ng/ml fibroblast growth factor) before EDTA treatment. After treatment, pieces were incubated in the same medium for 24, 48, 72, or 96 hours to permit cell cycle entry. Tissue was fixed, stained for Ki67 (a marker for late G1-phase through the M-phase), and mounted in medium containing propidium iodide to visualize all nuclei. Confocal images were evaluated by computer (Image software; NIH, Bethesda, MD) to count Ki67-positive and propidium iodide-stained cells.

RESULTS

EDTA released corneal endothelial cell-cell contacts in a dose- and time-dependent manner. At doses and incubation times tested, EDTA did not induce significant cell death. Preincubation in culture medium for 24 hours was needed for endothelial cells to efficiently initiate proliferation in response to EDTA. The endothelium of corneas incubated in mitogen-containing medium for up to 108 hours without EDTA treatment did not stain for Ki67. EDTA at 2.0 mg/ml for 60 minutes appeared optimal and stimulated 16% to 18% of the cells to proliferate. Ki67-positive mitotic figures were visible 48 hours after exposure to EDTA. Formation of daughter cells was visible after double-staining for Ki67 and ZO-1.

CONCLUSIONS

EDTA released cells from contact inhibition and promoted proliferation in corneal endothelium from older donors. The authors hypothesize that corneal endothelium from older individuals divide in situ when exposed to positive growth factors under conditions in which cells have been transiently released from contact inhibition.

[Cultured bovine corneal epithelial cells express functional water channel]

OBJECTIVE

To investigate the water permeability (P(f)) of the cultured bovine corneal epithelial cells (CBCEC) and whether aquaporins (AQPs) were present.

METHODS

Laser light-scattering system was used to determine the volume change of CBCEC from isotonic status rapidly transferred to hypotonic one, and the P(f) value was calculated. Messenger RNA obtained from CBCEC was injected into Xenopus laevis oocytes. After four days, the P(f) was determined by monitoring volume changes of oocytes upon hypoosmotic challenge (180 mOsm/L changed to 15 mOsm/L).

RESULTS

CBCEC challenged with 10% hypoosmotic solution at 37 degrees C swelled rapidly; the cellular P(f) was 72 microm/s. In the oocytes injected with mRNA from CBCEC, the P(f) increased to 76 microm/s. This increase was inhibited (by 89%) by 0.3 mmol/L HgCl(2).

CONCLUSION

Our results suggest that CBCEC express a typical mercurial-sensitive functional water channel in good numbers, judging from the comparatively high P(f) we measured. These begin to reopen the question of the presence and extent of an epithelial role in control of corneal hydration.

PGE2 synthesis by corneal endothelial cells: effect of glucocorticoids and NSAIDs

The aim of this work was to study the effect of various anti-inflammatory drugs on PGE2 synthesis in cultured bovine corneal endothelial cells (BCECs) stimulated with calcium ionophore A23187 or lipopolysaccharide (LPS) of Salmonella typhimurium. NSAIDs were more potent in inhibiting LPS-stimulated PGE2 synthesis. Diclofenac was more potent than indomethacin, although both drugs showed a 98% maximal inhibitory effect. Dexamethasone inhibited 80% of the A23187-stimulated PGE2 synthesis and only 53% of the LPS-stimulated PGE2 synthesis. Prednisolone did not show an inhibitory effect. The results demonstrate the inhibitory effect of NSAIDs and show differences between the activity of glucocorticoids on PGE2 synthesis in BCECs. Prednisolone could not inhibit PGE2 synthesis in these cells in our experimental conditions.

Protective role for bcl-2 in experimentally induced cell death of bovine corneal endothelial cells

To characterize the pattern of cell death and to investigate the potential role of bcl-2 in a death paradigm of corneal endothelial cells, primary cultures of bovine corneal endothelial (BCEN) cells were first established and treated with 0.01-1 microM staurosporine, a nonspecific protein kinase inhibitor. The pattern of BCEN cell death induced by staurosporine was apoptotic in nature, characterized by shrinkage of the cytoplasmic membrane, nuclear condensation and DNA fragmentation. Cotreatment of BCEN cells with Z-VAD-fmk (a caspase inhibitor) but not cycloheximide (a protein synthesis inhibitor) prevented staurosporine-induced cell death. To investigate the potential role of bcl-2, BCEN cells were transferred with a eukaryotic expression vector containing anti-apoptotic bcl-2 cDNA and characterized by reverse transcription-polymerase chain reaction (RT-PCR; BCEN/bcl-2). As measured by the MTT reduction assay after treatment with staurosporine, the survival rate of BCEN/bcl-2 cells was 48.0 +/- 4.8% compared to 7.4 +/- 2.1% in control BCEN cells. As determined by light microscopy, apoptotic changes such as nuclear condensation and apoptotic bodies were largely attenuated in BCEN/bcl-2 cells after staurosporine treatment although arborization of processes and rounding up of the cell body were not affected by overexpression of bcl-2. These results suggest that staurosporine induces apoptosis in a cycloheximide-independent but caspase-dependent manner and bcl-2 acts as a negative regulator in staurosporine-induced apoptosis of BCEN cells.

In vitro culture characteristics of corneal epithelial, endothelial, and keratocyte cells in a native collagen matrix

The objective of this investigation was to demonstrate the effectiveness of a tissue-engineered collagen sponge as a substrate for the culture of human corneal cells. To that end, human kerotocyte, epithelial, and endothelial cells were cultured separately on collagen sponges composed of native fibrillar collagen with a pore size of approximately 0.1 mm. Co-culture experiments were also performed (epithelial/endothelial and epithelial/keratocyte cultures). Proliferation of keratocytes and matrix production was assessed. The morphology of the epithelial and endothelial cell cultures was characterized by histology and scanning electron microscopy. Keratocytes cultured on collagen sponges exhibited increased matrix synthesis over time as well as proliferation and repopulation of the matrix. Epithelial and endothelial cells showed the ability to migrate over the collagen sponge. The thickness of the epithelial layer was influenced by soluble factors produced by endothelial cells. The morphology of the bottom layer of epithelial cells was influenced by the presence of keratocytes in the culture. These studies indicate that human corneal cells exhibit normal cell phenotype when cultured individually on an engineered collagen sponge matrix and co-culture of different cell types in the cornea can influence cell behavior.

[Changes of corneal endothelium in patients with primary glaucoma]

OBJECTIVE

To study the density and morphology of corneal endothelium in patients with primary glaucoma.

METHODS

125 eyes of 68 patients with glaucoma were compared with 63 eyes of 32 patients without glaucoma in the same age group. Exclusion criteria included history of corneal disease, ocular inflammation, trauma, contact lens wearing and surgery. The following date were recorded: type and duration of glaucoma, glaucoma medications, and intraocular pressure (IOP) measurement. Non-contact specular microscope was performed on the central cornea, endothelial images were analyzed by computer.

RESULTS

Corneal endothelium density was significantly lower in patients with glaucoma[(2386.81 +/- 289.76)/mm2] than that in controls [(2540.78 +/- 195.66)/mm2]. Cell density of primary angle-closure glaucoma(PACG) [(2262.65 +/- 338.64)/mm2] was significantly low, especially in acute PACG[(1925.16 +/- 403.38)/mm2]. The area of endothelium became bigger than normal. But the endothelium density and morphology of primary open-angle glaucoma(POAG) and non-acute PACG had no changes. No correlation was found between mean recent IOP and endothelium density.

CONCLUSIONS

This study suggested that patients with acute PACG might have lower corneal endothelium density and bigger cell area than those without glaucoma in the same age group. The endothelium density and morphology of POAG and non-acute PACG were as similar as those of normal persons.

Endothelial cell density of the cornea during rigid gas permeable contact lens wear

PURPOSE

To determine the influence of a daily wear rigid gas permeable (RGP) high DK lens (CIBA Vision Persecon92E, Dk=92 x 10(-11)) on corneal endothelial cell density (ECD).

METHODS

A prospective longitudinal, follow-up study was conducted. Variations in corneal ECD during the first year were reported. For this purpose, the endothelium of 97 eyes of 57 unadapted subjects were compared by specular microscopy before and after 1 week (n= 74), 1 month (n=67), 3 months (n=51), and 1 year (n=23) of wearing contact lenses.

RESULTS

There was a significant decrease in cell density vs age (r=-0.28, P=0.005). ECD significantly increased 1 week (3.6%) (P=0.001), 1 month (3.6%) (P=-0.003), and 3 months (4.5%) (P=0.003) after contact lens wear. One year after the lens fitting, a similar but not significant increase was found. While ECD increase was insignificant with initially high ECD subjects (>2700 cells/mm2), subjects with low ECD initially (<2700 cells/mm2) showed a significant increase in ECD in all time intervals.

CONCLUSIONS

In the 1 week RGP contact lens wearing period, the endotheliums with low ECD probably adapted to a new oxygen environment by cell migration or mitotic activity. The increased ECD was perhaps related to the daily wear schedule in which the oxygen partial pressure was sufficient.

Reassessment of the corneal endothelial cell organisation in children

AIM

To assess uniformity of the corneal endothelial cell mosaic in children.

METHODS

36 healthy children (5-11 years old, 16 boys, 20 girls) were assessed by specular microscopy. Endothelial cell density (ECD) was calculated from measured cell areas, and the number of sides/cell noted.

RESULTS

Average values for ECD and cell areas were 3987 cells/mm(2) (95% CI 3806 to 4168 cells/mm(2)) and 278 (SD 85) mm(2) respectively, with normal distribution (COV 28. 2%, range 17.4 to 39.2%) and with the average percentage of six sided cells being 66.6% (8.8%). Cell area was positively correlated to number of cell sides (p <0.01, r(2)=0.993), but the percentage of six sided cells was negatively correlated to ECD (p <0.01, r=0.493).

CONCLUSION

A high ECD occurs in children, but this does not mean there is a high percentage of "hexagons".

Laser in situ Keratomileusis After Penetrating Keratoplasty

PURPOSE

To determine the safety, efficacy, predictability, and stability of laser in situ keratomileusis (LASIK) to correct myopia and myopic astigmatism in eyes with prior penetrating keratoplasty.

METHODS

Eight eyes of 8 patients with penetrating keratoplasty had significant postoperative refractive error. Each eye received LASIK 1 year or more after penetrating keratoplasty. All were followed for 6 months or more. All patients were treated with the Chiron Technolas 217 excimer laser and the Automated Corneal Shaper microkeratome.

RESULTS

Mean spherical equivalent refraction decreased from -4.50 D (range, -3.00 to -7.25 D) to -0.75 D (range, -1.50 to +0.50 D) and the mean preoperative astigmatism decreased from 3.50 D (range, 1.50 to 5.00 D) to 1.25 D (range, 0.75 to 2.00 D). Uncorrected visual acuity improved by at least two Snellen lines in all eyes. Best spectacle-corrected visual acuity did not change in four eyes (50%) and improved in three eyes (37.5%).

CONCLUSION

LASIK effectively reduced low and moderate myopia and myopic astigmatism following penetrating keratoplasty.

Prospective, randomized clinical evaluation of Optisol vs organ culture corneal storage media

OBJECTIVE

To compare the outcome of penetrating keratoplasty with the use of corneas stored either in Optisol (Chiron Ophthalmics, Irvine, Calif) or in organ culture.

METHODS

Penetrating keratoplasty was performed on 12 pairs of patients matched by age and diagnosis. Each pair of procedures was done on the same day by the same surgeon using the same technique. Twelve pairs of corneas were used. One cornea of each pair had been stored in organ culture at 36 degrees C and one in Optisol at 4 degrees C. Mean (+/-SD) storage time was 6+/-3 days. Mean endothelial cell density before storage was 2617/mm(2) for the corneas in organ culture and 2624/mm(2) for the corneas in Optisol. Examinations were performed at 1, 4, 12, and 24 months.

RESULTS

One reversible rejection occurred in the Optisol group. At 1 month the mean endothelial cell density was 2327+/-341/mm(2) for the organ culture group and 2240+/-504/mm(2) for the Optisol group. At 12 months the difference was more pronounced (2225+/-410 and 2103+/-466/mm(2), respectively), although statistically not significant. Corneal thickness also did not show any statistically significant difference.

CONCLUSION

Penetrating keratoplasty performed with corneas stored for a maximum of 11 days in either Optisol or organ culture show similar outcomes in the first 2 postoperative years. Arch Ophthalmol. 2000;118:757-760

Some observations on the use of cultured corneal endothelial cells as a model for intact corneal endothelium

Major differences have been identified between corneal endothelial cells in situ and those grown in culture. Cells in intact porcine corneal endothelium were studied and compared with primary cultures of the same cells either in suspension or in monolayers which had been grown on plastic (Nunc, Permonax). Differences were identified in the organization of the cytoskeleton (filamentous actin) between the cells in situ and in monolayer culture. The ability to withstand exposure to cryoprotective concentrations of Me(2)SO also varied substantially depending on whether the cells were in situ or in culture. These results underline the need for caution in the use of cells in culture as a model for studying the nature of injury to cells during the freezing of whole tissues.

The resiliency of the corneal endothelium to refractive and intraocular surgery

PURPOSE

To describe stress factors (phenylephrine and contact lenses) from the corneal epithelium that can affect the corneal endothelium, and to describe the effects of refractive and intraocular surgery on the corneal endothelial structure and function.

METHODS

Significant clinical and experimental publications are reviewed and recent experiments conducted in the author's laboratory to describe the corneal endothelial stresses.

RESULTS

The corneal epithelium serves as a barrier to topical phenylephrine (2.5-10%). In a compromised epithelium, topical phenylephrine will cause drug-induced stromal edema and endothelial vacuolization. Contact lenses are capable of stimulating the epithelial arachidonic acid cascade to release 12(R)hydroxyeicosatetraenoic acid (12(R)HETE) and 8(R)hydroxy-hexadecatrienoic acid (8(R)HHDTrE) to cause endothelial Na+/K+ adenosine triphosphatase (ATPase)-inhibition and polymegethism. Specular microscopy of the corneal endothelial cells after refractive surgery (photorefractive keratectomy [PRK], laser in situ keratomileusis [LASIK], intrastromal rings [INTACs]) has shown that there is minimal effect. However, laser ablation of the stroma within 200 microm of the corneal endothelium will result in endothelial cell structural changes and the formation of the amorphous substance deposited onto Descemet's membrane. Phacoemulsification with a high flow of the irrigation solution can alter the endothelial surface glycoprotein layer. Lidocaine hydrochloride (1%) used as intracameral anesthesia readily diffuses through the corneal endothelium, resulting in stromal uptake and endothelial cell swelling. With phacoemulsification, however, the washout of lidocaine from the cornea (T1/2, 5 minutes) and iris (T1/2, 9 minutes) occurs quickly. Corneal endothelial wound healing after keratoplasty occurs in the following sequence: migration of endothelial cells, development of tight junctions, and the formation of Na+/K+ ATPase pump sites.

CONCLUSIONS

Corneal endothelial resiliency is due to the increased peripheral endothelial cell number for migration, the ability of endothelial cells to form tight junctions to maintain the endothelial barrier, the increase in endothelial Na+/K+ ATPase pump sites under stress, and the ability of the corneal endothelial cells to shift their metabolism of glucose to the hexose monophosphate shunt for the production of nicotinamide adenine dinucleotide phosphate (NADPH) and membrane repair. All of these factors are important, along with the aqueous humor sodium concentration, which establishes the osmotic gradient for corneal deturgescence and transparency.

Immortalization of human corneal endothelial cells using electroporation protocol optimized for human corneal endothelial and human retinal pigment epithelial cells

PURPOSE

In this study we established a protocol for transfection of human corneal endothelial and human retinal pigment epithelial cells. This protocol was used for immortalization of human corneal endothelial cells.

METHODS

Transfection was performed by means of electroporation. For immortalization a plasmid encoding large and small SV40 T-antigen was used.

RESULTS

The established electroporation protocol was suitable for both cell types. This protocol was used for transfection of human corneal endothelial cells with a plasmid containing the early region of SV40. The transfected cultures exhibited an increased life-span before they entered crisis. One culture recovered from crisis and was cultivated for 300 population doublings. The cells exhibited an in vivo-like morphology usually lost during cell culture.

CONCLUSIONS

We describe for the first time a culture of SV40 transfected human corneal endothelial cells which recovered from crisis and can therefore be regarded as immortalized.

Relationship of telomeres and p53 in aging bovine corneal endothelial cell cultures

PURPOSE

To demonstrate a relationship between telomere lengths and levels of p53 in cultured bovine corneal endothelial cells (CECs) during aging.

METHODS

Bovine CECs were grown and aged as long-term cultures. Telomere lengths were determined directly on gels with 32P probes after treatment of isolated DNA with RsaI and HinfI. Protein p53 was determined using an enzyme-linked immunosorbent sandwich assay. Cellular aging and the development of replicative senescence were monitored by the appearance of senescent morphology and the beta-galactosidase assay.

RESULTS

Bovine CEC telomeres lost 4 kb (from 12.8 to 8.8 kb) over 1 year (89 population doublings [PDs]). The p53 levels in bovine CECs were initially small (approximately 60 pg/million cells), but rose 3.5-fold by culture age of 260 days (64 PDs). On initiation, cultured bovine CECs did not stain for the senescent marker beta-galactosidase. However, these cells stained at 89 PDs and senescent morphology was observed in the cultures at 64 PDs.

CONCLUSIONS

The data indicate an inverse relationship between telomere lengths (decreasing) and levels of p53 (increasing) in bovine CECs during aging. These properties may influence the ability of these cells to divide as they enter into replicative senescence.

Assessment of the reliability of human corneal endothelial cell-density estimates using a noncontact specular microscope

PURPOSE

We sought to determine the variance in endothelial cell density (ECD) estimates for human corneal endothelia.

METHODS

Noncontact specular micrographs were obtained from white subjects without any history of contact lens wear, or major eye disease or surgery; subjects were within four age groups (children, young adults, older adults, senior citizens). The endothelial image was scanned, and the areas from > or =75 cells measured from an overlay by planimetry. The cell-area values were used to calculate the ECD repeatedly so that the intra- and intersubject variation in an average ECD estimate could be made by using different numbers of cells (5, 10, 15, etc.).

RESULTS

An average ECD of 3,519 cells/mm2 (range, 2,598-5,312 cells/mm2) was obtained of counts of 75 cells/ endothelium from individuals aged 6-83 years. Average ECD estimates in each age group were 4,124, 3,457, 3,360, and 3,113 cells/mm2, respectively. Analysis of intersubject variance revealed that ECD estimates would be expected to be no better than +/-10% if only 25 cells were measured per endothelium, but approach +/-2% if 75 cells are measured.

CONCLUSION

In assessing the corneal endothelium by noncontact specular microscopy, cell count should be given, and this should be > or =75/ endothelium for an expected variance to be at a level close to that recommended for monitoring age-, stress-, or surgery-related changes.

Cell cycle kinetics in corneal endothelium from old and young donors

PURPOSE

To compare cell cycle kinetics in corneal endothelial cells from young and old donors.

METHODS

Human corneas were obtained from the eye bank and separated into two groups: young (19 corneas, <30 years of age) and old (40 corneas, >50 years of age). Corneas were cut in quarters, and the endothelium was released from contact inhibition by producing a 2-mm scrape wound. Unwounded endothelium acted as a negative control. Corneal pieces were exposed for 24, 36, 48, 60, 72, and 84 hours to medium containing 10% fetal bovine serum, 20 ng/ml fibroblast growth factor, and 50 mg/ml gentamicin or the same medium supplemented with 10 ng/ml epidermal growth factor (EGF). Tissue was fixed, immunostained for Ki67 (a marker for the late G1-through M-phase) or for 5-bromo-2'-deoxyuridine (BrdU; a marker for the S-phase), and mounted in medium containing propidium iodide (PI) to visualize all nuclei. Confocal images were evaluated using an image analysis program to count Ki67-positive and PI-stained cells and to evaluate cell cycle position. Cells were counted in 15x100 microm2 areas randomly selected from each wound, and the mean was used for subsequent calculations.

RESULTS

Human corneal endothelial cells could be reliably scored for their position within the cell cycle using Ki67 staining patterns. In both age groups, cells repopulating the wound area stained positively for Ki67, whereas no Ki67 staining was observed in unwounded areas under any condition tested. Cells from old donors treated with fetal bovine serum and FGF stained positively for Ki67, indicating that these cells were actively cycling. Compared with cells from young donors, old cells entered the cell cycle more slowly (48 versus 36 hours), the peak of Ki67 staining occurred later (72 versus 60 hours), and fewer cells proliferated (23% versus 47%) or exhibited mitotic figures (4% versus 7%). Addition of EGF to the culture medium increased Ki67 staining in both groups, but the effect on old cells was more dramatic. More cells from old donors entered the cell cycle by 36 hours after wounding, the number of proliferating cells increased 1.6-fold, and the relative number of mitotic figures increased 2.5-fold over cells treated in the absence of EGF.

CONCLUSIONS

Regardless of donor age, corneal endothelial cells can enter and complete the cell cycle. In the presence of fetal bovine serum and FGF, cells from old donors can proliferate but respond more slowly and to a lesser extent than cells from young donors. EGF added to the medium stimulates cells from old donors to enter the cell cycle faster, increases the relative number of actively cycling cells, and increases the number of cells exhibiting mitotic figures. The resultant hypothesis is that it is possible to stimulate a significant proliferative response in corneal endothelial cells from old individuals. Administration of an optimal combination of stimulatory growth factors is required under conditions in which cells have been transiently released from contact inhibition.

Effect of irrigating solution and irrigation temperature on the cornea and pupil during phacoemulsification

PURPOSE

To evaluate the effect of irrigation solution and temperature on pupil diameter, corneal endothelium, and corneal pachymetry during and after phacoemulsification.

SETTING

Klinik Dardenne, Bonn, Germany.

METHODS

Eighty patients who had cataract surgery by phacoemulsification were assigned to 1 of 4 cross-classified groups and had intraoperative irrigation with room-temperature or refrigerated fortified balanced salt solution (BSS Plus) or modified Ringer's solution. Pupil diameters were recorded at different stages during the surgery. Epithelial cell counts and pachymetry were determined before and 1 day after surgery.

RESULTS

The solution temperature did not affect any parameter. The type of solution did not influence endothelial cell loss; however, the solution had a significant effect on corneal pachymetry 1 day postoperatively. The corneas irrigated with BSS Plus were less swollen than the corneas irrigated with Ringer's solution. By day 14, corneal thickness was equal among all groups.

CONCLUSION

Long-term results were equally favorable in all 4 groups. However BSS Plus induced less short-term corneal swelling than Ringer's solution. From these findings, it appears that BSS Plus may decrease corneal risk in cases with compromised corneas or prolonged surgery.

Phakic posterior chamber lenses for high myopia: functional and anatomical outcomes

PURPOSE

To evaluate the functional and the anatomical outcomes after implantation of phakic posterior chamber intraocular lenses (IOLs) in highly myopic eyes.

SETTING

Service d'Ophtalmologie, Hôpital Purpan, Toulouse, France.

METHODS

Fifty-eight eyes of 46 patients that had implantation of phakic posterior chamber lenses for high myopia were evaluated. Predictability, efficiency, safety, and subjective and objective quality of vision were evaluated preoperatively and at least 6 months postoperatively. The effect of the procedure on the cornea, aqueous humor, pupil, anterior chamber angle, crystalline lens, and retina were studied.

RESULTS

Mean preoperative myopia was -13.85 diopters (D) +/- 3.1 (SD) (range -8.00 to -19.25 D). Mean postoperative spherical equivalent was -1.22 +/- 0.83 D (range +0.75 to -3.50 D); 56.9% of eyes were within +/-1.00 D of the predicted result, and 77.6% gained 1 or more lines of best corrected visual acuity. All contact-lens-intolerant patients had improved quality of vision for day and night driving, distance vision, and vision under dim illumination. The mean postoperative level of contrast sensitivity without correction was higher than the mean preoperative level with correction. Adverse events were 2 cases of crystalline lens opacification 16 and 18 months after surgery and 2 cases of pigment deposits in the angle with increased intraocular pressure, which was controlled by beta-blockers.

CONCLUSION

Implantation of posterior chamber phakic IOLs is effective and predictable; however, long-term follow-up is needed.

Effectiveness of LASIK to correct refractive error after penetrating keratoplasty

OBJECTIVE

Refractive errors may invalidate the good results of penetrating keratoplasty (PK). The Authors evaluate the effectiveness of excimer laser in situ keratomileusis (LASIK) in the correction of refractive error after PK.

MATERIALS AND METHODS

Four patients, a 26-year-old woman, a 54-year-old man, a 19-year-old man, and a 51-year-old woman, showed refractive errors: -11 = -4.5 x 85 ; -8, -4.5 = -11 x 95 ; and -4.5 = -4 x = 1200, with a clear graft at least 20 months after penetrating keratoplasty secondary to keratoconus. However, they underwent the LASIK procedure with a nasal-hinged flap of 160 um. No sutures were placed.

RESULTS

At follow-up, 24, 18, 12, and 12 months, respectively, the graft remained clear and the endothelial cells were unchanged. The uncorrected visual acuities were 20/50, 20/25, 20/50, and 20/25, respectively with an unchanged best corrected visual acuity (20/20) for all patients. No significant complications were observed.

CONCLUSIONS

LASIK procedure seems to be an effective technique to correct refractive error after successful penetrating keratoplasty.

Purinoceptor-mediated calcium mobilization and cellular proliferation in cultured bovine corneal endothelial cells

In the present study, we investigated the effect of adenosine triphosphate (ATP) on cytosolic free calcium mobilization and mitogenic activity in cultured bovine corneal endothelial cells (BCEC). The [Ca2+]i was determined using a Ca2+ sensitive indicator, Fura-2/AM, and cell proliferation was evaluated by counting the cell number. ATP, its metabolites and analogs caused transient increase in [Ca2+]i in a concentration-dependent manner (10(-7) M-10(-3) M) and the potency of agonists was ordered as follows: 2-methylthio-ATP > uridine triphosphate > ATP > adenosine diphosphate. Adenosine monophosphate and adenosine did not affect [Ca2+]i. ATP (10(-4) M) also promoted the accumulation of inositol trisphosphate (IP3). The ATP-induced transient [Ca2+]i increase and IP3 accumulation were attenuated by pretreatment with a phospholipase C inhibitor, U-73122 (5 microM), for 30 min. ATP (10(-5) M) significantly enhanced the proliferation of BCEC. ATP-induced [Ca2+]i increase and cell proliferation were inhibited by a purinoceptor antagonist, suramin (10(-4) M). Thus, the present study indicates that BCEC contain P2 purinoceptors that regulate their proliferation.