Insulin-like Growth Factor Binding Protein-3 expression in the human corneal epithelium

Research output: Contribution to journalArticle

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Abstract

Insulin-like Growth Factor Binding Protein-3 (IGFBP3) is a high-affinity binding protein shown to regulate cell growth, differentiation, and apoptosis in a variety of cellular systems. The primary aim of this study was to characterize IGFBP3 expression in the human corneal epithelium and in a corneal epithelial cell line and to establish a potential role for IGFBP3-mediated apoptotic signaling in corneal epithelial cells. Using a telomerase-immortalized human corneal epithelial (hTCEpi) cell line cultured in serum-free media and fresh human eye bank donor tissue, expression and localization of IGFBP3 were established in situ and in vitro by indirect immunofluorescence and western blotting. Real-time PCR was used to measure IGFBP3 mRNA levels following Trichostatin A (TSA) treatment and as a function of confluence. IGFBP3 protein levels were assessed in resting human tears and in conditioned media by western blotting as was the ability of recombinant human IGFBP3 protein to associate with the cell surface. Apoptotic signaling was assessed in vitro using TSA and recombinant human (rh)IGFBP3. Apoptosis was measured by Viability/Cytotoxicity, Annexin V, and TUNEL assays. IGFBP3 was localized to the plasma membrane of human corneal epithelial cells in situ and was upregulated in surface cells in the central cornea. IGFBP3 was secreted in conditioned media of growing cells, with a robust upregulation following confluence (P = 0.014) and differentiation. IGFBP3 was undetectable in human tears. Addition of TSA to the culture media resulted in an upregulation of IGFBP3 mRNA (P < 0.001) and protein. In addition, TSA treatment led to a significant increase in Annexin V positive cells at 18 and 24 h (P < 0.001) and TUNEL positive cells at 24 and 48 h (P < 0.001). The addition of rhIGFBP3 to the cell culture media appeared to induce occasional membrane blebbing, but cells failed to become positive with Annexin V or TUNEL. Taken together, these results demonstrate that cell membrane-associated IGFBP3 is produced by corneal epithelial cells and associates with the plasma membrane of superficial cells in situ and in cultured cells, but not present in human tears. The differential localization and effect(s) on apoptosis suggest that the effects of IGFBP3 are likely tissue compartment and receptor specific and may be regulated by glycosylation.

Original languageEnglish (US)
Pages (from-to)492-501
Number of pages10
JournalExperimental Eye Research
Volume85
Issue number4
DOIs
StatePublished - Oct 2007

Fingerprint

Corneal Epithelium
Insulin-Like Growth Factor Binding Protein 3
trichostatin A
Epithelial Cells
Annexin A5
In Situ Nick-End Labeling
Tears
Cell Membrane
Apoptosis
Conditioned Culture Medium
Culture Media
Up-Regulation
Western Blotting
Eye Banks
Cell Line
Messenger RNA
Proteins
Telomerase
Serum-Free Culture Media
Blister

Keywords

  • apoptosis
  • corneal epithelium
  • IGFBP3

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

Cite this

Insulin-like Growth Factor Binding Protein-3 expression in the human corneal epithelium. / Robertson, Danielle M; Ho, Su Inn; Hansen, Baranda S.; Petroll, Walter M; Cavanagh, Harrison D.

In: Experimental Eye Research, Vol. 85, No. 4, 10.2007, p. 492-501.

Research output: Contribution to journalArticle

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abstract = "Insulin-like Growth Factor Binding Protein-3 (IGFBP3) is a high-affinity binding protein shown to regulate cell growth, differentiation, and apoptosis in a variety of cellular systems. The primary aim of this study was to characterize IGFBP3 expression in the human corneal epithelium and in a corneal epithelial cell line and to establish a potential role for IGFBP3-mediated apoptotic signaling in corneal epithelial cells. Using a telomerase-immortalized human corneal epithelial (hTCEpi) cell line cultured in serum-free media and fresh human eye bank donor tissue, expression and localization of IGFBP3 were established in situ and in vitro by indirect immunofluorescence and western blotting. Real-time PCR was used to measure IGFBP3 mRNA levels following Trichostatin A (TSA) treatment and as a function of confluence. IGFBP3 protein levels were assessed in resting human tears and in conditioned media by western blotting as was the ability of recombinant human IGFBP3 protein to associate with the cell surface. Apoptotic signaling was assessed in vitro using TSA and recombinant human (rh)IGFBP3. Apoptosis was measured by Viability/Cytotoxicity, Annexin V, and TUNEL assays. IGFBP3 was localized to the plasma membrane of human corneal epithelial cells in situ and was upregulated in surface cells in the central cornea. IGFBP3 was secreted in conditioned media of growing cells, with a robust upregulation following confluence (P = 0.014) and differentiation. IGFBP3 was undetectable in human tears. Addition of TSA to the culture media resulted in an upregulation of IGFBP3 mRNA (P < 0.001) and protein. In addition, TSA treatment led to a significant increase in Annexin V positive cells at 18 and 24 h (P < 0.001) and TUNEL positive cells at 24 and 48 h (P < 0.001). The addition of rhIGFBP3 to the cell culture media appeared to induce occasional membrane blebbing, but cells failed to become positive with Annexin V or TUNEL. Taken together, these results demonstrate that cell membrane-associated IGFBP3 is produced by corneal epithelial cells and associates with the plasma membrane of superficial cells in situ and in cultured cells, but not present in human tears. The differential localization and effect(s) on apoptosis suggest that the effects of IGFBP3 are likely tissue compartment and receptor specific and may be regulated by glycosylation.",
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