Mechanistic insights into conjunctivalization in limbal stem cell deficiency using a lineage tracing approach

Disease that develops on the ocular surface in animals and humans that have their limbal stem cells erased or their niche severely damaged by physical or chemical trauma, is difficult to visually evaluate in a progressive and long-term manner. When limbal stem cell deficiency (LSCD) develops under such circumstances, intravital clinical microscopy or other techniques cannot be used to accurately detail what transpires on the cornea. Here, we investigated the evolution of LSCD and characterize cellular transformations that arise when the limbal niche is lost.

We employed the multi-color K14CreER^T2-Confetti transgenic reporter mice (n = 51) to monitor LSCD in real-time, combined with proliferation markers and in vitro analyses to identify and characterize conjunctival epithelial transformations using wild-type C57BL/6 mice (n = 31).

Conjunctival epithelia either spawn MUC5AC ⁺ goblet cells (GCs) or K12⁺ cornea-like epithelia. These cells arise from Ki67⁺ proliferating differentiated conjunctival squames as opposed to DNA label retaining conjunctival stem/progenitor cells. In vitro analyses suggests that GC metaplasia (GCM) and conjunctival transdifferentiation (CjTD) evolve from environmental stress and soluble keratocyte elaborated signals and corneal matrix-associated physical cues.

GCM is a pathological process, as opposed to CjTD, which is the cornea's attempt to self-repair. The co-existence of two fundamentally diverse cellular interchanges establishes a medical conundrum in LSCD which may be resolved via pharmacological or biological intervention in conjunction with surgery to replenish the stem cell pool.