title: Signal transduction pathway involved in the ex vivo expansion of limbal epithelial cells cultured on various substrates.
abstract: OBJECTIVE
  Ex vivo expansion of the limbal epithelial cells activates the nerve growth factor (NGF) mediated downstream signal transduction pathway. It is not clear as to which factors control the stemness of the corneal limbal stem cells, i.e., the maintenance of stem cell properties. It is likely that various signaling pathways are involved, including Notch, Wnt and NGF signaling, etc. In the present study, we investigated the activation of phosphoinositide-3-kinase (PI3K) pathway on cells cultured over the chitosan matrix, chitosan silver matrix, chitosan gold matrix, intact and denuded human amniotic membrane (HAM).
  
  
  METHODS
  Human limbal biopsies obtained from the cadaveric donor eyes were used in this study. The cells cultured over different substrate and observed for the activation of the downstream signaling molecules of PI3K/Akt/FKHRL1 pathway. Western blotting was done to prove the results.
  
  
  RESULTS
  The cells cultured over the intact HAM showed the activation of the downstream signaling molecules of PI3K/Akt/JNK pathway compared to the cells grown over other substrates. On inhibition of the PI3K activity there was absence of phosphorylation of downstream effectors in the limbal epithelial cells from the explant culture over the intact HAM.
  
  
  CONCLUSIONS
  The ex vivo expansion of human limbal epithelial progenitor cells on intact HAM was mediated by PI3K/Akt/FKHRL1 pathway, which is known to govern cell survival, and the mitogen-activated protein kinase (MAPK) pathway, known to control the cell mitosis.
authors.affiliation: L&T Department of Ocular Pathology, Vision Research Foundation, Sankara Nethralaya, Chennai, India.
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Sudha
authors.forename: Srilatha
authors.initials: S
authors.lastname: Jasty
authors.forename: Sasirekha
authors.initials: S
authors.lastname: Krishnan
authors.forename: Subramanian
authors.initials: S
authors.lastname: Krishnakumar
mesh_terms: D000650:Amnion; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D048271:Chitosan; D003315:Cornea / Q000166:cytology*; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D020932:Nerve Growth Factor / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology*
chemical_list: D048271:Chitosan; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases