Preferential Biological Processes in the Human Limbus by Differential Gene Profiling

Abstract

Corneal epithelial stem cells or limbal stem cells (LSCs) are responsible for the maintenance of the corneal epithelium in humans. The exact location of LSCs is still under debate, but the increasing need for identifying the biological processes in the limbus, where LSCs are located, is of great importance in the regulation of LSCs. In our current study we identified 146 preferentially expressed genes in the human limbus in direct comparison to that in the cornea and conjunctiva. The expression of newly identified limbal transcripts endomucin, fibromodulin, paired-like homeodomain 2 (PITX2) and axin-2 were validated using qRT-PCR. Further protein analysis on the newly identified limbal transcripts showed protein localization of PITX2 in the basal and suprabasal layer of the limbal epithelium and very low expression in the cornea and conjunctiva. Two other limbal transcripts, frizzled-7 and tenascin-C, were expressed in the basal epithelial layer of the limbus. Gene ontology and network analysis of the overexpressed limbal genes revealed cell-cell adhesion, Wnt and TGF-β/BMP signaling components among other developmental processes in the limbus. These results could aid in a better understanding of the regulatory elements in the LSC microenvironment.

microRNA-103/107 Family Regulates Multiple Epithelial Stem Cell Characteristics

“…However, Wnt‐β‐catenin signaling is not a requirement for proliferative capacity of hair follicle stem cells but is necessary for stem cell fate determination . Our findings implicate attenuation of the noncanonical JNK‐DVL and Ca +2 ‐CMKII pathways, which enhances limbal and epidermal keratinocyte proliferative capacity Endogenous Wnt activity is normally low in the unperturbed limbal epithelium . Similarly, Wnt 3A was minimally detected in limbal epithelial precursor and limbal niche cells as well as in the stem cell‐enriched bulge region of the telogen hair follicle .…”

Frizzled 7 Maintains the Undifferentiated State of Human Limbal Stem/Progenitor Cells

“…It has been reported that Wnt4 is upregulated in fetal limbal cornea compared to fetal central cornea and in primary cultured limbal epithelium compared to the cells after five passages . Our previous studies revealed several Wnt signaling components preferentially expressed in the limbus than in the cornea in both adult monkey and human . In addition, activation of Wnt/β‐catenin signaling using LiCl increases the proliferation and colony‐forming efficiency (CFE) of cultured human limbal epithelial cells , suggesting an active role of Wnt signaling in LSCs regulation.…”

Pigmentation Is Associated with Stemness Hierarchy of Progenitor Cells Within Cultured Limbal Epithelial Cells

“…Earlier attempts to clarify the developmental biology and differentiation hierarchy of hLESCs have been hampered by the use of nondiscovery based methods such as microarray analysis , poor study material such as nonhuman or whole unfractionated tissue , or impure hLESC cultures . A few discovery based next‐generation sequencing hLESCs transcriptomic studies have been conducted but these were also limited by the use of in situ material or nonhuman models .…”