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Molecular profiling of conjunctival epithelial side-population stem cells: atypical cell surface markers and sources of a slow-cycling phenotype.

ABSTRACT: Side-population (SP) cells isolated from limbal and conjunctival epithelia derive from cells that are slow cycling in vivo, a known feature of tissue stem cells. The purpose of this study was to define the molecular signature of the conjunctival SP cells and identify markers and signaling pathways associated with the phenotype of these cells.Overnight cultures of freshly isolated human conjunctival epithelial cells stained with Hoechst 33342 were sorted by flow cytometry into SP and non-SP cohorts. Isolated RNA was processed for microarray analysis using a commercial oligonucleotide spotted array. Results were validated at the gene and protein levels by quantitative PCR and immunologic methods. Data mining methods were used to identify cellular processes relevant for stem cell function.Comparative analyses of transcripts expression based on present and absent software calls across four replicate experiments identified 16,993 conjunctival epithelial transcripts including 10,266 unique known genes of approximately 24,000 represented in the array. Of those genes, 1254 and 363 were overexpressed (>2-fold) or underexpressed (<0.5-fold), respectively, in the SP. The overexpressed set included genes coding for proteins that have been associated with (1) embryonic development and/or stem cell self renewal (MSX, MEIS, ID, Hes1, and SIX homeodomain genes); (2) cell survival (e.g., CYP1A1 to degrade aromatic genotoxic compounds); (3) cycling rate (e.g., DUSPs and Pax6 to foster slow cycling); and (4) genes whose expression is not typical in epithelia (e.g., CD62E).The molecular signature of conjunctival SP cells is consistent with a stem cell phenotype. Their gene expression patterns underpin slow cycling and plasticity, features associated with tissue stem cells. The results provide valuable insights for the preservation and/or expansion of epithelial stem cells.

SUBMITTER: Akinci MA

PROVIDER: S-EPMC2759864 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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Molecular profiling of conjunctival epithelial side-population stem cells: atypical cell surface markers and sources of a slow-cycling phenotype.

Akinci M A Murat MA Turner Helen H Taveras Maria M Barash Alex A Wang Zheng Z Reinach Peter P Wolosin J Mario JM

Investigative ophthalmology & visual science 20090325 9

<h4>Purpose</h4>Side-population (SP) cells isolated from limbal and conjunctival epithelia derive from cells that are slow cycling in vivo, a known feature of tissue stem cells. The purpose of this study was to define the molecular signature of the conjunctival SP cells and identify markers and signaling pathways associated with the phenotype of these cells.<h4>Methods</h4>Overnight cultures of freshly isolated human conjunctival epithelial cells stained with Hoechst 33342 were sorted by flow cy ...[more]

PMID: 19324848

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Project description:Side population (SP) cells isolated from limbal and conjunctival epithelia derive from cells that are slow cycling in vivo, a known feature of tissue stem cells. The purpose of this study was to define the molecular signature of the conjunctival side population cells by global differential gene expression to identify markers and signaling pathways associated with this cell phenotype. Four overnight cultures of freshly isolated human conjunctival epithelial cells stained with Hoechst 3342 were cytometrically sorted into SP and non-SP cohorts. RNA was isolated and processed for microarray analysis using a commercial oligonucleotide array representing more than 55,000 transcripts derived from about 30,000 different genes. Selected microarray results were validated at the gene and protein levels by quantitative PCR, and immunological methods. Data mining methods were used to identify cellular processes relevant for stem cell function. Comparative analysis of transcripts expression based on expression levels and present/absent software calls across 4 replicate experiments identified 16993 expressed conjunctival epithelial transcripts including 10,266 unique known genes. Of those genes, 1254 and 363 were over expressed (> 2-fold ) or under expressed (< 0.5-fold), respectively, in the SP. The overexpressed set included genes coding for non-epithelial genes (e.g., CD62E/E-selectin and CD93), genes that have been associated with stem cell function in other cellular systems, including several homeodomain genes and genes whose over- or under-expression may underpin the stem cell slow cycling phenotype ( e.g., dual specificity phosphatases and cyclin kinases). Experiment Overall Design: Whole human conjunctivae from unidentifiable cadaver donors, aged 55 to 65, were obtained from the National Disease Research Interchange (NDRI, Philadelphia, PA) within 48 hours of collection. No donor details apart from age, sex, and cause of death were released. The use of human tissue in the study was in accordance with the provisions of the Declaration of Helsinki and sanctioned by the Institutional Review Board. Fresh rabbit tissue was obtained from local abattoirs within one hour of sacrifice. Unless stated otherwise all reagents were procured from Sigma (St. Louis, Mo). Experiment Overall Design: Eight microarray experiments using side population (Hoechst 33342-transporting cells; SP) or non side population (Hoechst 33342-stained cells; nSP) cells from four cadavers.

Project description:Human conjunctival cell lines are useful tools for modeling ocular surface disease and evaluation of ocular drugs and cosmetics. However, gene expression in these cells may not be comparable to primary cultured cells, raising doubts that they could be used as a substitute. We aimed to ascertain the similarities of global gene expression between commonly used cell lines and primary cells using a microarray approach. The Affymetrix U133A chip (>22,000 genes) was used to investigate conjunctival tissue (CT), primary conjunctival epithelial cells (PCEC), two conjunctival epithelial cell lines (IOBA-NHC and ChWK), and HCEC-T, a human corneal epithelial cell line (control). Using principal component analysis, the PCEC profile was clustered more closely to conjunctival tissue than either of the two cell lines. Certain extracellular matrix genes were differentially upregulated in CT compared to PCEC, suggesting presence of fibroblasts in addition to epithelial cells in CT. Overall, 67.3% (95% CI: 66.7-67.9) of transcripts in IOBA-NHC were within 1.5-fold of the corresponding transcripts in PCEC, but only 62.2% (95% CI: 61.5-62.9) in the case of ChWK. In HCEC-T, the proportion was only 58.8% (95% CI 58.1-59.4), suggesting less resemblance to PCEC than the conjunctival epithelial cell lines. The IOBA-NHC profile was more similar to PCEC than ChWK, for all genes and genes concerned with membrane association, communication, development, and regulation of metabolism, especially protein and nucleic acid metabolism. The correlation of normalized gene expression levels was high between either the IOBA-NHC or ChWK and PCEC for genes concerned with cell defense, viral life cycle, antigen presentation, antioxidation, or ubiquitin ligation. In order to evaluate the functional significance of the altered gene expression in IOBA-NHC cells, we evaluated a few proteins important for epithelial differentiation or defense, corresponding to the transcripts for S100A9, TGM2, and TLR4. Protein levels of S100A9 and TGM2 were indeed raised, and TLR4 decreased, in IOBA-NHC compared to PCEC. Gene expression in conjunctival cell lines differs from primary cells, but the profile varies according to functional gene categories. Depending on the methodology of proposed studies, if there is limited availability of PCEC, NHC-IOBA may be more suitable than ChWK, but even then, epithelial differentiation and innate immunity functions in NHC-IOBA may differ from primary cells.

Dataset Information

Molecular profiling of conjunctival epithelial side-population stem cells: atypical cell surface markers and sources of a slow-cycling phenotype.

Publications

Molecular profiling of conjunctival epithelial side-population stem cells: atypical cell surface markers and sources of a slow-cycling phenotype.

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