|
|
||||||||
1From the Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan; and 2Biological Sciences, Lancaster University, Lancaster, United Kingdom.
| Abstract |
|---|
|
|
|---|
METHODS. HCECs obtained from peripheral corneal tissue were cultivated, passaged, and transplanted onto denuded AM. The cell density and morphology of the resultant cHCECs on AM were examined by light, scanning electron, and transmission electron microscopy. To determine whether these cHCEC sheets on AM carrier were functional in vivo, the cHCEC sheets on AM were transplanted onto rabbit corneas whose Descemets membrane and endothelial cells had been completely removed. After transplantation, the corneal appearance was examined by slit lamp biomicroscopy, and corneal thickness was measured daily by pachymetry. At 7 days after surgery, the grafts were examined by light, scanning electron, and transmission electron microscopy.
RESULTS. The density of the cHCECs on AM was greater than 3000 cells/mm2. Morphologically, the cHCEC sheets consisted of a fairly continuous layer of flat squamous polygonal endothelial cells that appeared uniform in size with tightly opposed cell junctions in vitro and in vivo after transplantation. The corneas that received transplanted cHCEC sheets had little edema and retained their thinness and transparency.
CONCLUSIONS. The cell density and morphology of cHCECs on AM were similar to those of normal corneas, and cHCECs on AM were functional in vivo. These results indicate that AM maintains HCEC morphology and function and could serve as a carrier for cHCEC transplantation.
For cHCEC transplantation in vivo, some type of carrier is obviously necessary. Up to now, for corneal endothelial cell transplantation, gelatin membranes (Schwartz BD, et al. IOVS 1980;21:ARVO Abstract 100; McCully JP, et al. IOVS 1981;22:ARVO Abstract 230)4 5 and coated hydrogel lenses6 have been used as synthetic carriers for these cells. Human amniotic membrane (AM), widely used as a surgical material,9 has been used successfully as a carrier for cultivated corneal epithelial cell transplantation.8 9 10 In this study, we sought to examine whether AM could also serve as a carrier for cHCECs, both in vitro and in vivo.
| Materials and Methods |
|---|
|
|
|---|
HCEC Culture
To cultivate HCECs, corneal limbal tissue was placed in a Petri dish containing Dulbeccos modified Eagles medium (DMEM; Invitrogen Corp., Carlsbad, CA), 50 U/mL penicillin, and 50 µg/mL streptomycin. Under a dissecting microscope, Descemets membrane with its attached corneal endothelium 1 mm apart from trabecular meshwork was stripped from the stroma and placed in a 35-mm dish containing 1.2 U/mL dispase in phosphate-buffered saline (PBS). The tissue was incubated for 1 hour at 37°C, and the cells were rinsed gently with a sterile pipette. The dispase was then inactivated by suspending the cells in a medium containing DMEM, 50 U/mL penicillin, and 50 µg/mL streptomycin. After gentle centrifugation (3 minutes at 180g), the cells were resuspended in culture medium containing DMEM, 50 U/mL penicillin, 50 µg/mL streptomycin, 10% fetal bovine serum (ICN Biomedicals, Inc., Aurora, OH), and 2 ng/mL basic fibroblast growth factor (Invitrogen Corp.).
The cells were incubated in wells of a collagen IVcoated 24-well plate at 37°C in 5% carbon dioxide-95% humidified air. The medium was changed every other day. Cells reached confluence in 10 to 20 days and were then subcultured by treatment with trypsin-EDTA (Invitrogen Corp.) and seeded at a ratio of 1:2 to 1:8.
Preparation of AM
In accordance with the tenets of the Declaration of Helsinki and with proper informed consent, human AMs were obtained at the time of cesarean section. The method of removing the amniotic epithelial cells from the AM has been reported.11 Briefly, human AM was stored at -80°C in DMEM and glycerol (Nacalai Tesque, Kyoto, Japan) after the AM was washed with PBS containing antibiotics (5 mL of 0.3% ofloxacin). Immediately before use, the thawed AM was deprived of amniotic epithelial cells by incubation with 0.02% EDTA (Wako Pure Chemical Industries, Osaka, Japan) at 37°C for 2 hours, followed by gentle cell scraping with a cell scraper (Nalge Nunc International, Naperville, IL). The tissues were then washed twice with sterile PBS. To confirm whether epithelium was completely removed from AM, light microscopy was used to examine the AM (Fig. 1A) .
|
In some experiments, to investigate the extent of the survival of cHCECs on AM after transplantation in vivo, we labeled the cHCECs with the fluorescent membrane dye DiI (1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine perchlorate).12 The stock solution of DiI was made by dissolving 5 mg dye in 5 mL 70% ethanol. The DiI labeling solution was made by diluting the stock solution by 10. Immediately before seeding the HCECs on to the AM, the cells were labeled in vitro by adding DiI solution to the cell suspension. After incubation for 5 minutes at 37°C, the cell suspension was cooled on ice for 15 minutes. Excess dye was then removed by washing the cells twice in PBS. Cells were resuspended at a final cell-seeding concentration of 6.0 x 103 cells/mm2 and seeded on denuded AM, cultured for 7 days, and transplanted. We conducted this experiment with two cHCEC sheets on AM carriers transplanted into rabbit corneas. At 7 days after transplantation, we killed the animals, removed the grafts, and observed them under the fluorescence microscope. We stained same tissues with alizarin red and examined them under the microscope.
Light and Electron Microscopy
Cultures of cHCECs on denuded AM were examined by light, scanning electron, and transmission electron microscopy.
For light microscopy, tissues were stained with alizarin red and hematoxylin and eosin. For alizarin red staining, day-14 cultures on AM were placed endothelial side up on glass slides. Tissues were briefly rinsed in 0.9% sodium chloride followed by a 1-minute staining with 1% alizarin red in deionized water. Cell density (cells per square millimeter) was calculated by averaging cell density of three cHCEC sheets. For cell density of one sheet, five areas (each area equaled 0.25 mm2) per one sheet were examined and averaged.
For hematoxylin and eosin stain, day-14 cultures on AM were embedded in optimal cutting temperature (OCT) compound (Tissue-Tek; Sakura Fine Technical, Tokyo, Japan). After freezing, the resultant blocks were cut into 8-µm-thick sections with a cryostat. The sections were stained with hematoxylin and eosin for examination.
For scanning electron microscopy, day 14 cultures on AM were fixed in 2.5% glutaraldehyde in 0.1 M PBS, washed three times for 15 minutes in PBS, postfixed for 2 hours in 2% osmium tetroxide, and washed three more times in PBS. After dehydration through a graded ethanol series (50%, 70%, 80%, 90%, 95%, and 100%) specimens were transferred to hexamethyldisilazane (Agar Scientific, London, UK) for 2 x 10 minutes and allowed to air dry. When dry, specimens were mounted on aluminum stubs and sputter coated with gold before examination on a scanning electron microscope (model JSM 5600; Japanese Electron Optical Limited [JEOL], Tokyo, Japan).
For transmission electron microscopy, day-14 cultures on AM were fixed in 2.5% glutaraldehyde in 0.1 M PBS, postfixed in 2% osmium tetroxide, dehydrated through a graded ethanol series, and embedded in epoxy resin (Agar 100; Agar Scientific). Ultrathin (70 nm) sections were collected on copper grids and stained for 1 hour each with uranyl acetate and 1% phosphotungstic acid and for 20 minutes with Reynolds lead citrate before examination on a transmission electron microscope (JEM 1010; JEOL).
Animals
Male Japanese white rabbits weighing 2 to 3 kg were obtained from Shimizu Laboratory (Kyoto, Japan). All animals were treated in accordance with the ARVO Statement for Use of Animals in Ophthalmic and Vision Research. The Committee for Animal Research, Kyoto Prefectural University of Medicine, approved all animal studies.
cHCEC Transplantation
Transplantation was performed on the right eye only. Corneal buttons and graft beds were prepared by excising a 7.00-mm site in the central cornea. Descemets membranes together with the endothelium were stripped from the corneal buttons. cHCEC sheets, using AM as a carrier, on culture inserts were trephined to a diameter of 6.25 mm, and they were separated gently from inserts with fine forceps. These sheets were placed on the stroma of the corneal buttons, left for a few minutes until dry to secure the sheet to the stroma. The corneal buttons with cHCEC sheets were then placed on the graft bed of the same animal and sutured with eight interrupted sutures and a continuous suture (10-0 nylon). Four groups were prepared in this experiment (Table 1) . Each group had three animals. In the first group (the cHCEC group), after Descemets membrane was stripped, the cHCEC sheet was placed on the corneal button and transplanted as just described. In the second group (the SD control group), Descemets membrane was stripped and the button transplanted as described. In the third group (the AM control group), after Descemets membrane was stripped, just the acellular AM was transplanted, as described. In the last group (the TO control group), the host cornea was trephined only and transplanted as described, without stripping Descemets membrane and transplanting any sheet. All grafted eyes were examined every day after transplantation. Grafts with technical difficulties (e.g., hyphema, infection, or loss of the anterior chamber) were excluded from further consideration. At day 4 after transplantation, the interrupted sutures were removed.
|
| Results |
|---|
|
|
|---|
|
|
|
|
|
|
|
| Discussion |
|---|
|
|
|---|
In our study, the morphology and structure of cHCECs transplanted on denuded AM were evaluated by vital staining, as well as scanning and transmission electron microscopy. We found that the ultrastructure and density of these cells was very similar to that of normal corneal endothelial cells ex vivo. It is also important in cHCEC transplantation to obtain higher cell density. Clinically, it has been proposed that donor corneal tissue with endothelial density of more than 2500 cells/mm2 are ideal to be transplanted in patients with bullous keratoplasty. Using centrifugation, we obtained cHCEC sheets with a density of more than 3000 cells/mm2. These cHCEC sheets seem to have high enough cell density to be used in patients for bullous keratopathy.
In our in vivo study, we also found that the rabbit corneas with transplanted cHCECs on AM retained their thickness and transparency compared with the controls for 1 week, and we also found, but in only one rabbit, that this situation continued for 4 weeks (data not shown). Because rabbit corneal endothelial cells have been known to proliferate in vivo, we wished to investigate the extent of survival of cHCECs transplanted in vivo by using DiI labeling. The results of the DiI labeling showed that the cHCECs remained on the denuded AM transplanted onto the corneal button at least 4 weeks. These results show that transplanted cHCEC sheets remained and were functional for at least 4 weeks. We intend to further investigate the long-term consequences of cHCEC transplantation and the functions of the cHCEC sheet. The HCEC density in the transplants showed 27% reduction 7 days after transplantation, either because of the tissue damage at the time of surgery or the short life of some cultivated endothelial cells. To investigate the long-term consequences of cHCEC transplantation, it is not suitable to use rabbits as recipients, because their corneal endothelial cells proliferate in vivo. It may be better to use cats or monkeys as recipients, because their corneal endothelial cells more closely mimic HCECs in having little or no mitotic activity and a limited regenerative capacity.
The transplanted cHCEC corneas using AM as a carrier are clearer and thinner than either corneas transplanted with AM only or corneas with removed Descemets membranes and endothelial cells. Furthermore, the transplanted cHCEC corneas are as thin as corneas with trephination only. These results indicate that HCECs on AM function as well as that of normal endothelium at least until 7 days after transplantation. The transplanted cHCEC corneas with AM regained partial transparency after transplantation. Normal corneal stromal clarity depends on the regular arrangement of collagen fibers, AM does not have such a characteristic structure. However, we think thinning of AM after transplantation increased its transparency, as seen in the eyes with cultured corneal epithelial cells transplanted for corneal epithelial diseases.10 There was a gap of 0.1 to 0.2 mm between donor human endothelial cells and host rabbit endothelial cells, but the transplanted corneas retained their corneal thickness and transparency. We think that the gap had some influence on the pumpleak balance. The water permeating into the corneal stroma through the nonendothelial area may pump out through the adjacent human and rabbit endothelial area. Because an area of central cornea more than 6 mm in diameter is covered by transplanted HCECs, it is reasonable to speculate that endothelial cells pump water from corneal stroma, although other possible factors such as evaporation may contribute to this to some extent.
In our present study, we transplanted cHCEC sheets by trephining the central corneas, removing Descemets membranes with corneal endothelial cells, placing cHCEC sheets on the stroma of corneal buttons, and suturing them. A technique termed posterior lamellar keratoplasty, an operation for the treatment of bullous keratopathy, has been reported by Melles et al.20 In this method the full-thickness cornea is not transplanted, just the posterior lamella of the cornea, and the method could be adapted for cHCEC transplantation. We have now investigated a cHCEC transplantation technique to remove corneal endothelial cells with Descemets membrane and transplant a cHCEC sheet through a corneoscleral incision, similar to posterior lamellar keratoplasty. cHCEC sheet transplantation by this technique would be expected to have the same advantages as a posterior lamellar keratoplasty: fewer problems with sutures after they are in place, lower astigmatism, and more efficient use of donor tissue. In addition cHCEC transplantation may well have the advantage that scheduled operations could be performed, because we would not be dependent on the availability of corneoscleral discs. This possibility therefore has many advantages for both patients and health professionals.
cHCEC transplantation has the potential to be performed, not only as an allogeneic transplantation procedure but also as an autotransplantation procedure, if a small number of corneal endothelial cells from a healthy eye were cultivated, expanded, and transplanted to the contralateral endothelial damaged eye of the same patient. Moreover, in regenerative medicine, the potential of some pluripotent stem cells21 22 23 for use in clinical treatments has been noted. Therefore, if pluripotent stem cells (e.g., hematopoietic stem cells and mesenchymal stem cells obtained from bone marrow) could be obtained from patients who undergo bullous keratoplasty and these stem cells could be induced to differentiate into corneal endothelial cells, it would be possible to transplant autologous corneal endothelial sheets without any risk of rejection.
| Footnotes |
|---|
Submitted for publication January 7, 2003; revised June 24 and August 28, 2003; accepted August 31, 2003.
Disclosure: Y. Ishino, None; Y. Sano, None; T. Nakamura, None; C.J. Connon, None; H. Rigby, None; N.J. Fullwood, None; S. Kinoshita, None
The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked "advertisement" in accordance with 18 U.S.C.
1734 solely to indicate this fact.
Corresponding author: Yutaka Ishino, Department of Ophthalmology, Kyoto Prefectural University of Medicine, 465 Hirokoji Kawaramachi, Kamigyo-ku, Kyoto, Japan; yishino{at}ophth.kpu-m.ac.jp.
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
N. Koizumi, Y. Sakamoto, N. Okumura, N. Okahara, H. Tsuchiya, R. Torii, L. J. Cooper, Y. Ban, H. Tanioka, and S. Kinoshita Cultivated Corneal Endothelial Cell Sheet Transplantation in a Primate Model Invest. Ophthalmol. Vis. Sci., October 1, 2007; 48(10): 4519 - 4526. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. H. Suh, C. Zhang, R. S. Chuck, W. J. Stark, S. Naylor, K. Binley, S. Chakravarti, and A. S. Jun Cryopreservation and Lentiviral-Mediated Genetic Modification of Human Primary Cultured Corneal Endothelial Cells Invest. Ophthalmol. Vis. Sci., July 1, 2007; 48(7): 3056 - 3061. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. Li, A. L. Sabater, Y.-T. Chen, Y. Hayashida, S.-Y. Chen, H. He, and S. C. G. Tseng A Novel Method of Isolation, Preservation, and Expansion of Human Corneal Endothelial Cells Invest. Ophthalmol. Vis. Sci., February 1, 2007; 48(2): 614 - 620. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Kikuchi, C. Zhu, T. Senoo, Y. Obara, and N. C. Joyce p27kip1 siRNA Induces Proliferation in Corneal Endothelial Cells from Young but Not Older Donors Invest. Ophthalmol. Vis. Sci., November 1, 2006; 47(11): 4803 - 4809. [Abstract] [Full Text] [PDF] |
||||
![]() |
J.-Y. Lai, K.-H. Chen, W.-M. Hsu, G.-H. Hsiue, and Y.-H. Lee Bioengineered Human Corneal Endothelium for Transplantation Arch Ophthalmol, October 1, 2006; 124(10): 1441 - 1448. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Mimura, S. Yamagami, S. Yokoo, M. Araie, and S. Amano Comparison of Rabbit Corneal Endothelial Cell Precursors in the Central and Peripheral Cornea Invest. Ophthalmol. Vis. Sci., October 1, 2005; 46(10): 3645 - 3648. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Mimura, S. Yamagami, S. Yokoo, Y. Yanagi, T. Usui, K. Ono, M. Araie, and S. Amano Sphere Therapy for Corneal Endothelium Deficiency in a Rabbit Model Invest. Ophthalmol. Vis. Sci., September 1, 2005; 46(9): 3128 - 3135. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Yokoo, S. Yamagami, Y. Yanagi, S. Uchida, T. Mimura, T. Usui, and S. Amano Human Corneal Endothelial Cell Precursors Isolated by Sphere-Forming Assay Invest. Ophthalmol. Vis. Sci., May 1, 2005; 46(5): 1626 - 1631. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |