Maturation of adult beta-cells revealed using a Pdx1/insulin dual-reporter lentivirus

Endocrinology. 2009 Apr;150(4):1627-35. doi: 10.1210/en.2008-1224. Epub 2008 Dec 18.

Abstract

The enigmatic process of beta-cell maturation has significant implications for diabetes pathogenesis, and potential diabetes therapies. This study examined the dynamics and heterogeneity of insulin and pancreatic duodenal homeobox (Pdx)-1 gene expression in adult beta-cells. Insulin and Pdx1 expression were monitored in human and mouse islet cells and MIN6 cells using a Pdx1-monomeric red fluorescent protein/insulin-enhanced green fluorescent protein dual-reporter lentivirus. The majority of fluorescent cells were highly positive for both Pdx1 and insulin. Cells expressing Pdx1 but little or no insulin (Pdx1(+)/Ins(low)) comprised 15-25% of the total population. Time-lapse imaging demonstrated that Pdx1(+)/Ins(low) primary beta-cells and MIN6 cells could convert to Pdx1(+)/Ins(+) cells without cell division. Genes involved in the mature beta-cell phenotype (Glut2, MafA) were expressed at higher levels in Pdx1(+)/Ins(+) cells relative to Pdx1(+)/Ins(low) cells. Conversely, genes implicated in early beta-cell development (MafB, Nkx2.2) were enriched in Pdx1(+)/Ins(low) cells. Sorted Pdx1(+)/Ins(low) MIN6 cells had a higher replication rate and secreted less insulin relative to double-positive cells. Long-term phenotype tracking of Pdx1(+)/Ins(low) cells showed two groups, one that matured into Pdx1(+)/Ins(+) cells and one that remained immature. These results demonstrate that adult beta-cells pass through distinct maturation states, which is consistent with previously observed heterogeneity in insulin and Pdx1 expression in adult beta-cells. At a given time, a proportion of adult beta-cells share similar characteristics to functionally immature embryonic beta-cell progenitors. The maturation of adult beta-cells recapitulates development in that Pdx1 expression precedes the robust expression of insulin and other mature beta-cell genes. These results have implications for harnessing the maturation process for therapeutic purposes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cells, Cultured
  • Flow Cytometry
  • Gene Expression / drug effects
  • Glucose / pharmacology
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Homeodomain Proteins / genetics*
  • Humans
  • Insulin / genetics*
  • Insulin-Secreting Cells / drug effects
  • Insulin-Secreting Cells / metabolism*
  • Lentivirus / genetics*
  • Mice
  • Microscopy, Fluorescence
  • Potassium Chloride / pharmacology
  • Promoter Regions, Genetic / genetics*
  • Rats
  • Reverse Transcriptase Polymerase Chain Reaction
  • Trans-Activators / genetics*

Substances

  • Homeodomain Proteins
  • Insulin
  • Trans-Activators
  • enhanced green fluorescent protein
  • pancreatic and duodenal homeobox 1 protein
  • Green Fluorescent Proteins
  • Potassium Chloride
  • Glucose