Human Conjunctival Stem Cells are Predominantly Located in the Medial Canthal and Inferior Forniceal Areas

Abstract

Purpose: The conjunctiva plays a key role in ocular surface defence and maintenance of the tear film. Ex vivo expansion of conjunctival epithelial cells offers potential to reconstruct the ocular surface in cases of severe cicatrising disease, but requires initial biopsies rich in stem cells to ensure long-term success. The distribution of human conjunctival stem cells, however, has not been clearly elucidated.

Methods: Whole human cadaveric conjunctiva was retrieved and divided into specific areas for comparison. From each donor, all areas from one specimen were cultured for colony-forming efficiency assays and immunocytochemical studies; all areas from the other specimen were fixed and paraffin embedded for immunohistochemical studies. Expression of CK19, p63, and stem cell markers ABCG2, ΔNp63, and Hsp70 were analyzed. Results were correlated to donor age and postmortem retrieval time.

Results: Conjunctiva was retrieved from 13 donors (26 specimens). Colony-forming efficiency and expression of stem cell markers ABCG2, ΔNp63, and Hsp70 in cultures and ABCG2 in fixed tissue were all consistently demonstrated throughout the tissue but with highest levels in the medial canthal and inferior forniceal areas (P < 0.01 for each). Both increasing donor age and longer postmortem retrieval times were associated with significantly lower colony-forming efficiency, stem cell marker expression in cell cultures and ABCG2 expression in fixed tissue.

Conclusions: Biopsies from the medial canthus and inferior forniceal areas, from younger donors, and with short postmortem retrieval times offer the greatest potential to developing conjunctival stem cell-rich epithelial constructs for transplantation.

Keywords: conjunctiva; inferior fornix; medial canthus; progenitor cell; stem cell.