Human Conjunctival Stem Cells are Predominantly Located in the Medial Canthus and Inferior Fornix

Abstract

 

Purpose:

 

The ability to culture complete functional conjunctival epithelial sheets in vitro for ocular surface reconstruction would be greatly enhanced by a higher proportion of stem cells in the initial biopsy. This research therefore, aimed to locate the sites of human conjunctival stem cells.

 

Methods:

 

A technique was developed to retrieve whole intact human cadaveric conjunctival tissue extending from the lid margins to the limbus, spanning the posterior lid, tarsal, bulbar and forniceal areas. Tissue was retrieved from 18 donors (36 eyes) within 24 hours of death and divided into specific areas for comparison. One specimen from each donor was co-cultured with inactivated 3T3 fibroblasts for colony forming efficiency assays and immunocytochemical studies. The other specimen was fixed in formaldehyde and paraffin embedded for immunohistochemical studies. Various stem cell and conjunctival markers were analyzed including P63ΔN, P634A4, ABCG2, Hsp70 and CK19.

 

Results:

 

A significant pattern of colony forming efficiency was consistently demonstrated across the conjunctiva: highest levels were found in the medial canthal and inferior forniceal conjunctiva than in other areas (p < 0.005; figure). Immunocyto- and immunohistochemical staining supported these findings with greater proportions of cells in these areas staining for stem cell markers P63ΔN, ABCG2 and Hsp70 (p < 0.005).

 

Conclusions:

 

Conjunctival stem cells are distributed throughout the conjunctiva but are richest in the medial canthus and inferior fornix. This knowledge will aid choice of conjunctival biopsy site for optimal tissue expansion in vitro.  

 

Keywords: conjunctiva