title: A comparison of stem cell-related gene expression in the progenitor-rich limbal epithelium and the differentiating central corneal epithelium.
abstract: OBJECTIVE
  Corneal epithelium is maintained by a population of stem cells (SCs) that have not been identified by specific molecular markers. The objective of this study was to find new putative markers for these SCs and to identify associated molecular pathways.
  
  
  METHODS
  Real time PCR (rt-PCR) was performed in 24 human limbal and central corneal epithelial samples to evaluate the gene expression profile of known corneal epithelial SC-associated markers. A pool of those samples was further analyzed by a rt-PCR array (RT²-PCR-A) for 84 genes related to the identification, growth, maintenance, and differentiation of SCs.
  
  
  RESULTS
  Cells from the corneal epithelium SC niche showed significant expression of ATP-binding cassette sub-family G member 2 (ABCG2) and cytokeratin (KRT)15, KRT14, and KRT5 genes. RT²-PCR-A results indicated an increased or decreased expression in 21 and 24 genes, respectively, in cells from the corneal SC niche compared to cells from the central corneal epithelium. Functional analysis by proprietary software found 4 different associated pathways and a novel network with the highest upregulated genes in the corneal SC niche. This led to the identification of specific molecules, chemokine (C-X-C motif) ligand 12 (CXCL12), islet-1 transcription factor LIM/homeodomain (ISL1), collagen-type II alpha 1 (COL2A), neural cell adhesion molecule 1 (NCAM1), aggrecan (ACAN), forkhead box A2 (FOXA2), Gap junction protein beta 1/connexin 32 (GJB1/Cnx32), and Msh homeobox 1 (MSX1), that could be used to recognize putative corneal epithelial SCs grown in culture and intended for transplantation. Other molecules, NCAM1 and GJB1/Cnx32, potentially could be used to positively purify them, and Par-6 partitioning defective 6 homolog alpha (PARD6A) to negatively purify them.
  
  
  CONCLUSIONS
  Knowledge of these gene and molecular pathways has provided a better understanding of the signaling molecular pathways associated with progenitor-rich limbal epithelium. This knowledge potentially could give support to the design and development of innovative therapies with the potential to reverse corneal blindness arising from ocular surface failure.
authors.affiliation: Institute for Applied Ophthalmobiology (IOBA), University of Valladolid, Valladolid, Spain. tnietom@ioba.med.uva.es
authors.forename: Teresa
authors.initials: T
authors.lastname: Nieto-Miguel
authors.forename: Margarita
authors.initials: M
authors.lastname: Calonge
authors.forename: Ana
authors.initials: A
authors.lastname: de la Mata
authors.forename: Marina
authors.initials: M
authors.lastname: López-Paniagua
authors.forename: Sara
authors.initials: S
authors.lastname: Galindo
authors.forename: María Fideliz
authors.initials: MF
authors.lastname: de la Paz
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Corrales
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D001344:Autopsy; D015415:Biomarkers / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics; D019573:Epithelium, Corneal / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks; D006801:Humans; D053547:Keratin-14 / Q000235:genetics / Q000378:metabolism; D053569:Keratin-15 / Q000235:genetics / Q000378:metabolism; D053555:Keratin-5 / Q000235:genetics / Q000378:metabolism; D016850:Limbus Corneae / Q000166:cytology / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D015415:Biomarkers; D053547:Keratin-14; D053569:Keratin-15; D053555:Keratin-5; D009363:Neoplasm Proteins; D012333:RNA, Messenger