Effects of streptozotocin on in vitro long-term cultured human islet cell monolayers

Replacement beta cells may be generated from stem/progenitor cells, possibly residing within the pancreatic islet cells. We sought to investigate the possible use of human islet (HI)-derived cell monolayers as a possible source for beta cells. These cells could be propagated in vitro and potentially induced to acquire glucose-stimulated insulin release (GSIR) ability. Loss of three-dimensional architecture, following monolayer establishment, resulted in either rearrangement of both pancreatic hormone expression and key transcription factors or decrease in insulin production or GSIR disappearance. We showed that cell deregulation/dedifferentiation was reversible by treating the cell monolayers, after five passages with streptozotocin (STZ), a well-known beta-cell toxin. When used at subtoxic concentrations, STZ promoted differentiation of HI-derived cell monolayers and GSIR recovery. This effect allowed production of insulin-secreting cells starting from cell monolayers doubled five times in vitro, meaning a 400-fold increase in the cellular starting material. Such islet cell expansion capability in vitro might elucidate a new source of insulin-secreting cells thereby possibly overcoming the problem posed by searching for human organ donation.