New paper! We developed an approach to perform scRNA-seq on islets from #stemcells after txp. We found the islets cured #diabetes & matured to very closely resemble real donor islets! Congrats to @WashUBME PhD co-1st authors @punnaug & @KristinaGMaxwel 1/n cell.com/cell-reports/f…
STORY TIME: This project concept has been a fantasy of mine since I was a graduate student, but the technology to do it robustly was simply not there until recently. Even then, we first performed the transplantations for this study in 2018, because of the extended timescales. 2/n 
Many labs, including our own, had observed that pancreatic stem cell derivatives (pancreatic progenitors, endocrine progenitors, stem cell-derived islets (SC-islets) at varies stages of maturation) better controlled glycemia with extended time in mice. 3/n
Relatedly, the field widely recognizes that the cells we made in vitro (SC-islets) are immature both transcriptionally and functionally compared to native islets from human donors 4/n doi.org/10.1016/j.stem…
It was a mystery that this improved glycemic control after transplantation was due to various types of progenitors differentiating into SC-islets/beta cells and/or that the already differentiated cells matured, and thus were better able to exert glycemic control. 5/n
Punn and Kristina tackled this challenge by first developing an approach to recover SC-islets from the kidneys of mice 6 months after transplantation. 6/n
This involved excising the kidney, cutting away the graft, single-cell dissociating the graft, MACS removal of some of the mouse cells, sequencing, and then computational removal of the residual mouse cells. 7/n
This grafted SC-islet sequencing data set allowed for comparison of data sets from SC-islets before transplantation and human islets from cadaveric donors. We made many interesting observations with this comparison. 8/n
The most important was that the SC-beta cells transcriptionally matured to closely resemble primary beta cells. 9/n
Genes well known to be under expressed by SC-beta cells in vitro had increased expression after txp, such as INS, MAFA, SIX2, MNX1, CHGB, and G6PC2. Overall gene expression and gene sets saw similar trends. 10/n
Of the genes identified here were genes, like FAM159B, identified in @bcellorg’s Patch-seq paper being important to human beta cell electrophysiology. His team’s paper was useful to cross-reference some of our observations on the ‘not usual suspects’ 11/n sciencedirect.com/science/articl…
One other gene of interest was IAPP (amylin), a peptide which we found to be an amazing biomarker correlating with maturation state of SC-islets. This peptide is normally co-secreted with insulin/C-peptide in beta cells but is hugely under expressed in SC-beta cells in vitro 12/n
IAPP peptide had a greater dynamic great than insulin in the serum of mice. Perhaps a good biomarker/target marker for enhanced maturation of SC-beta cells? 13/n
Some of the identified genes had not previously been associated with beta or SC-beta cell maturation. Hopefully a great dataset to mine 14/n
In addition to SC-beta cells, we show datasets on the transcriptional changes of alpha and the enterochromaffin (EC) cells identified by @Adrian_Veres_ & @TheMeltonLab. This likely is important to the translation of this technology to diabetes cell replacement therapy. 15/n
However, for the SC-EC cells, while we catalogue the transcriptional changes and confirm these cells persist for months after transplantation, we really have no idea what effect, if any, they have on in vivo maturation of the islet endocrine cells. 16/n
One fundamental conclusion is that SC-islets made in vitro are not ‘stuck’ in that specified maturation state. They are capable of changing and maturing to be closer to real islets. 17/n
This teaches us that these cells have not irreversibly gone down the ‘wrong path’ and, if given the proper signals, can be matured further in vitro. 18/n
Overall, we hope that this resource article provides an informative dataset to spurs continued innovation in developing maximally mature SC-islets for diabetes cell replacement therapy, drug screening, studies of diabetes pathology, and studies of pancreatic development. 19/END
*dynamic range
