Purpose. We have proposed that conjunctival epithelial stem cells are enriched in the fomical zone for the following reasons: (1) Fornical epithelial cells display greater in vitro growth capacity than bulbar or palpebral epithelial cells (FVOS 1993;34:1814-1828). (2) Slow-cycling basal keratinocytes are concentrated in the fomical epithelium (IVOS 1994; 36:236-246). In this work we asked whether fornical epithelium would display a differential in vivo response to acute and chronic stimulation. Methods. To induce epithelial hyperproliferation, we topically applied 0.5% phorbol myristate (TPA) in petrolatum daily to both eyes of SENCAR mice for 12 days. Control mice received petrolatum only. After 1,2,3,4,5,7,9, and 12 days of TPA treatment, mice received i.p. (0.1ml of) 40|xCi of 3H-thymidinc (-H-TdR), 1 hr prior to sacrifice. Conjunctival epithelium was fixed, processed for autoradiography, and the labeling index (LI; # 3H-TdR-kbeled nuclei/1000 basal keratinocytes) was determined for each of the epithelial zones. Results. Under normal situations, the LI was lowest in fomical epithelium (2.0 ±0.5) compared with bulbar (4.4 ±0.9) and palpebral (5.5 ±0.5) epithelia. Within 14 hrs after TPA treatment, a 12-fold increase in fornical basal cell labeling was noted compared with a 2.5- and 5-fold increase in bulbar and palpebral basal cell labeling, respectively. Fornical epithelium maintained a significantly greater proliferative response (4.5-fold increase) during chronic stimulation than either bulbar or palpebral epithelia (0.5- and 1.5-fold increase, respectively). Conclusions. The more vigorous response of the fomical epithelium to chronic stimulation is strong evidence that this epithelium has a greater proliferative capacity than the other two epithelia, consistent with our hypothesis that conjunctival epithelial stem cells arc primarily located in the fornical region.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience