title: Colony forming unit endothelial cells do not exhibit telomerase alternative splicing variants and activity.
abstract: Endothelial progenitor colony forming unit-endothelial cells (CFU-EC) were first believed to be the progenitors of endothelial cells, named endothelial progenitor cells. Further studies revealed that they are monocytes regulating vasculogenesis. The main hindrance of these cells for therapeutic purposes is their low frequency and limited replicative potentials. This study was undertaken to determine telomerase activity and alternative splicing variants in CFU-EC as a potential cause of limited replicative capacity in these cells.
  
  
  
  CFU-EC were isolated from peripheral blood using a standard cell culture assay. Colonies were detached mechanically and alternative splicing variant mRNA were evaluated using real-time PCR. Telomerase enzyme activity was assessed using telomerase repeat amplification protocol. The same procedures were done on the cancer cell line Calu6 as the positive control.
  
  
  
  The cultured peripheral blood mononuclear cells formed colonies with spindle-shaped monocytic cells sprouted from the clusters. These morphological characteristics fulfill the definition of CFU-EC. Telomere length amplification protocol assay revealed no telomerase activity and real-time PCR showed no expression of telomerase enzyme mRNA in CFU-EC. Both parameters were significantly higher in the cancer cell line Calu6 taken as the positive control.
  
  
  
  The absence of telomerase activity in the CFU-EC is a result of pre-transcriptional regulation of gene expression rather than other mechanisms for controlling telomerase activity such as post-transcriptional modifications. This finding can explain the limited proliferative activity of CFU-EC cells. We propose that absence of telomerase activity in CFU-EC can be attributable to their more mature monocytic nature that needs further investigations.
authors.affiliation: Student Research Committee, Shiraz University of Medical Sciences (SUMS), Shiraz, Iran.|Cellular and Molecular Research Club, Shiraz, Iran.|Dept. of Cardiovascular, Shiraz, Iran.
authors.forename: Armin
authors.initials: A
authors.lastname: Attar
authors.affiliation: Student Research Committee, Shiraz University of Medical Sciences (SUMS), Shiraz, Iran.|Cellular and Molecular Research Club, Shiraz, Iran.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Khosravi Maharlooi
authors.affiliation: Student Research Committee, Shiraz University of Medical Sciences (SUMS), Shiraz, Iran.|Cellular and Molecular Research Club, Shiraz, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Khoshkhou
authors.affiliation: Institute of Cancer Research, Shiraz, Iran.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Hosseini
authors.affiliation: Institute of Cancer Research, Shiraz, Iran.
authors.forename: Mansoureh
authors.initials: M
authors.lastname: Jaberipour
authors.affiliation: Student Research Committee, Shiraz University of Medical Sciences (SUMS), Shiraz, Iran.|Cellular and Molecular Research Club, Shiraz, Iran.
authors.forename: Arman
authors.initials: A
authors.lastname: Dehghan
authors.affiliation: Dept. of Pathology, Shiraz University of Medical Sciences (SUMS), Shiraz, Iran.|Hematology Research Center, 
  Shiraz University of Medical Sciences (SUMS), Shiraz, Iran.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Monabati
mesh_terms: D000328:Adult; D017398:Alternative Splicing / Q000235:genetics*; D042783:Endothelial Cells / Q000166:cytology* / Q000201:enzymology*; D006801:Humans; D060888:Real-Time Polymerase Chain Reaction; D017384:Sequence Deletion; D013234:Stem Cells / Q000166:cytology* / Q000201:enzymology*; D019098:Telomerase / Q000235:genetics* / Q000378:metabolism; D016615:Telomere / Q000378:metabolism
chemical_list: D019098:Telomerase
keywords: Telomerase; Endothelial cells; Hemangioblast; Alternative splicing