hPDX1 adenovirus

Since diabetes is caused by an absolute or relative deficiency of insulin secretion from pancreatic β cells, efforts have been devoted to finding methods to effectively generate replacement β cells. So far, insulin-secreting cells have been generated from various differentiated cell types in the pancreas, such as acinar cells and α cells, by inducing specific transcription factors, such as PDX1 and MAFA. However, how to effectively generate replacement β cells to establish future regenerative therapies for diabetes remains a challenge. Here, researchers demonstrated that exogenously expressed PDX1 activated STAT3 in α cells in vitro, while α cells expressing STAT3-deficient PDX1 in vivo effectively induced α-to-β reprogramming, with the emergence of insulin-secreting cells derived from α cells, whose glucagon expression was suppressed. Depletion of β cells by administration of a degenerative toxin significantly increased the number of α-cell-derived insulin-secreting cells, while inhibition of STAT3 resulted in no increase in β-cell neogenesis after β-cell depletion. Therefore, STAT3 regulation and β-cell depletion non-additively enhanced PDX1-induced α-β reprogramming, which may help establish cell therapies for the treatment of diabetes.

STAT3 has been shown to be activated in pancreatic acinar cells that ectopically express Pdx1. To investigate whether STAT3 is activated in both pancreatic α cells and acinar cells, αTC1 cells were infected with an adenoviral vector expressing Pdx1 (Ad-Pdx1). Immunoblotting of STAT3 phosphorylated at Tyr705 (pSTAT3) showed that pSTAT3 levels were significantly increased in αTC1 cells infected with Ad-Pdx1 compared with control αTC1 cells infected with adenovirus expressing green fluorescent protein (GFP) (Ad-GFP) 72 h after infection (Figure 1A, B). In addition, immunocytochemical staining clearly detected pSTAT3 protein in Ad-Pdx1-infected αTC1 cells, with high expression of PDX1, while the number of pSTAT3-positive cells was low in cells with weak PDX1 expression and control cells infected with Ad-GFP (Figure 1C). When αTC1 cells were infected with an adenoviral vector expressing Mafa (Ad-Mafa), another β-cell-specific transcription factor, exogenously expressed Mafa did not activate STAT3. This is in contrast to previous findings in mPAC cells, which exhibit pancreatic progenitor-like characteristics. Taken together, these findings suggest that Pdx1 activates STAT3 not only in acinar cells but also in α cells.

Figure 1. Ectopic expression of Pdx1 induces STAT3 activation in α cells. (Wakabayashi Y, et al., 2022)