The endothelium is the monolayer of cells, located at the posterior of the cornea, which maintains corneal transparency. In humans, corneal endothelial cell density decreases with age, suggesting that the rate of cell replacement by mitosis does not keep pace with the rate of cell loss. Other factors, such as diabetes, inflammation, ocular trauma or surgery, contribute to cell loss and can lead to endothelial decompensation, stromal edema, and loss of visual acuity. Bullous keratopathy caused by endothelial dysfunction is currently medically untreatable and restoration of vision can only be accomplished by corneal transplantation. Our long- term goal is to develop medical treatments to promote healing of stressed corneal endothelium. To reach this goal, we must discover how corneal endothelial repair is regulated. Normally, both mitosis and cell movement contribute to monolayer repair; however, human corneal endothelium does not readily divide upon injury, so repair occurs mainly by cell movement. This relative lack of mitotic capability is not universal, since corneal endothelial cells in species, such as rabbits, readily divide. Studies during the last grant cycle focussed on the regulation of cell movements. The proposed studies will change focus to concentrate on the regulation of the corneal endothelial cell cycle. This approach is more direct and may be more helpful in achieving the long-term goal. The working hypothesis for these studies is that, although in humans the relative number of senescent, non-dividing cells increases with age, there is, at all ages, a population of mitotically quiescent, G1-phase arrested cells which are capable of mitogenic stimulation. In both humans and rabbits, in vivo conditions maintain the endothelium in a quiescent, differentiated state to preserve its important physiologic functions. Factors which may contribute to quiescence include contact inhibition, the relatively high concentration of TGF-beta (a potential growth inhibitor) in the aqueous humor, and autocrine mitotic inhibition by PGE2. Reversal of growth arrest in the presence of growth factors, such as EGF, should promote mitosis in stressed corneal endothelium. The proposed studies will use cell biological, pharmacological and molecular biological methods to achieve the following Specific Aims: 1) Compare in human and rabbit corneal endothelium the relative percent of actively cycling and quiescent cells and the relative position within the cell cycle in which quiescent cells are arrested, 2) Determine whether, during early fetal development, there is a change in human corneal endothelium from an actively cycling to a quiescent state which correlates with the formation of a stable, contact inhibited and/or differentiated monolayer, 3) Determine whether release from contact inhibition, particularly in the presence of EGF and/or indomethacin can stimulate corneal endothelial cells to re-enter the cell cycle, and 4) Determine whether TGF-beta inhibits corneal endothelial cell division and whether such inhibition is reversible. These studies should help determine the relative mitotic potential of human corneal endothelium, investigate causes for in vivo inhibition of corneal endothelial mitosis and help discover means to reverse mitotic inhibition in a clinically relevant manner.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY005767-15
Application #
6178449
Study Section
Visual Sciences A Study Section (VISA)
Program Officer
Fisher, Richard S
Project Start
1985-07-01
Project End
2002-03-31
Budget Start
2000-04-01
Budget End
2002-03-31
Support Year
15
Fiscal Year
2000
Total Cost
$335,580
Indirect Cost
Name
Schepens Eye Research Institute
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
02114
Joyce, Nancy C (2012) Proliferative capacity of corneal endothelial cells. Exp Eye Res 95:16-23
Ishino, Yutaka; Zhu, Cheng; Harris, Deshea L et al. (2008) Protein tyrosine phosphatase-1B (PTP1B) helps regulate EGF-induced stimulation of S-phase entry in human corneal endothelial cells. Mol Vis 14:61-70
Harris, Deshea L; Joyce, Nancy C (2007) Protein tyrosine phosphatase, PTP1B, expression and activity in rat corneal endothelial cells. Mol Vis 13:785-96
Konomi, Kenji; Joyce, Nancy C (2007) Age and topographical comparison of telomere lengths in human corneal endothelial cells. Mol Vis 13:1251-8
Konomi, Kenji; Zhu, Cheng; Harris, Deshea et al. (2005) Comparison of the proliferative capacity of human corneal endothelial cells from the central and peripheral areas. Invest Ophthalmol Vis Sci 46:4086-91
Joyce, Nancy C; Zhu, Cheng Chris (2004) Human corneal endothelial cell proliferation: potential for use in regenerative medicine. Cornea 23:S8-S19
Zhu, Cheng; Joyce, Nancy C (2004) Proliferative response of corneal endothelial cells from young and older donors. Invest Ophthalmol Vis Sci 45:1743-51
Joyce, Nancy C; Harris, Deshea L; Mello, David M (2002) Mechanisms of mitotic inhibition in corneal endothelium: contact inhibition and TGF-beta2. Invest Ophthalmol Vis Sci 43:2152-9
Zieske, J D; Hutcheon, A E; Guo, X et al. (2001) TGF-beta receptor types I and II are differentially expressed during corneal epithelial wound repair. Invest Ophthalmol Vis Sci 42:1465-71
Senoo, T; Obara, Y; Joyce, N C (2000) EDTA: a promoter of proliferation in human corneal endothelium. Invest Ophthalmol Vis Sci 41:2930-5

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