Epithelial and mesenchymal progenitor cells in normal and inflamed human lacrimal glands

Stem/progenitor cells play an important role in tissue repair and regeneration in response to injury and maintain tissue homeostasis. The existence of the progenitor cells within the human lacrimal gland is established, but their distribution and response to tissue injury are unclear. This study investigated progenitor cells' distribution and gene expression in normal and inflamed human lacrimal glands. Biopsies from healthy human lacrimal glands (n = 9, 61 ± 14.3 years) and non-specific dacryoadenitis (n = 5; 42.8 ± 19.3 years) were immunostained with progenitor cell markers- Nestin, p63 alpha, CK15, ABCG2, c-kit, and CD90, along with RT-PCR. The basal cell layer of interlobular and intercalated ducts and periacinar spindle-shaped cells expressed progenitor markers. In the dacryoadenitis specimens, lacrimal gland injury was noted as moderate to severe diffuse inflammation and acinar atrophy. The average percentage of positive cells (in ten high-power fields) showed no significant change in dacryoadenitis specimens, except for an increase in CD90. Gene expression revealed a substantial increase in CD90 and reduced expression of ABCG2 and p63α in dacryoadenitis. Double immunostaining with CD73 and CD105 demonstrated predominant CD90 expression in the endothelial cells rather than in the periacinar or periductal regions. The human lacrimal gland has progenitor cells around the intercalated and interlobular ducts that do not increase in severe glandular inflammation. Inflamed lacrimal glands have a demonstrable increase in the expression of MSCs but a reduction in epithelial progenitor cells. Future studies on the interaction between immune and progenitor/stem cells within the lacrimal gland will clarify the mechanisms involved.