Research

Our team has described a subpopulation of human ductal cells with progenitor-like characteristics. They express high levels of PDX1 and the BMP receptor 1A (BMPR1A, or ALK3), but lack CAII, a functional ductal marker. Upon sorting and culture, these cells proliferate when exposed to BMP-7, and differentiate into all adult pancreatic cell types (including functional β-cells) following BMP-7 withdrawal (Klein et al, Diabetes 2015; Qadir et al, Cell Reports 2018). scRNAseq of the ALK3bright fraction of human pancreatic donors confirmed the existence of clusters with progenitor-like features, with evidence suggesting that such features may be acquired by de-differentiation (Qadir et al, PNAS 2020; and rev. by Domínguez-Bendala et al, Trends in Endocrinology and Metabolism 2019). Sorted populations enriched in markers differentially expressed in these clusters can be ectopically transplanted into immune-deficient mice, where they not only differentiate into functional endocrine and exocrine cells, but also self-organize into ‘micro-pancreata’ with native-like cytoarchitecture (Qadir et al., PNAS 2020).  We remain actively engaged in the in-depth characterization of the human pancreatic progenitor cell niche in samples form healthy as well as T1 and T2D donors.

More recently, we have developed the means to study the dynamic processes behind progenitor cell-dependent regeneration using human pancreatic slices (HPSs). These sections maintain near-intact tissue architecture and function, providing a virtual in vitro window into a live pancreas. Using patented oxygen-enhancing devices designed at the DRI, we have achieved functional long-term culture of HPSs (Qadir et al., Nature Comms. 2020). This technological breakthrough has allowed us to longitudinally track, in real time, beta-cell regeneration in slices from healthy as well as T1D and T2D donors.

Arguably, the long-term culture of HPSs is the final piece needed to realize the full potential of single-cell transcriptomics for the study of human pancreatic regeneration. The combination of long-term organotypic culture with lineage-tracing in vitro and sequential scRNAseq offers a wealth of new research possibilities (Doke et al., Cell Metabolism, 2023). The multi-organ pursuit of all these avenues to the fullest extent afforded by these novel methods will likely revolutionize the design of human regeneration research.

The transplantation of human pluripotent stem cell (hPSC)-derived insulin-producing β-cells for the treatment of diabetes is finally approaching the clinical stage. However, even with state-of-the-art differentiation protocols, a significant percentage of undefined non-endocrine cell types is still generated. Most importantly, there is the potential for carry-over of non-differentiated cell types that may produce teratomas. We sought to modify hPSCs so that their differentiated progeny could be selectively devoid of tumorigenic cells and enriched for cells of the desired phenotype (in this case, β-cells). We have genetically modified hPSCs so that they harbor two suicide gene cassettes, whose expression results in cell death in the presence of specific pro-drugs. We have shown the efficacy of this system at enriching for β-cells and eliminating tumorigenic ones both in vitro and in vivo. Our approach is innovative inasmuch as it allows for the preservation of the desired cells while eliminating those with the potential to develop teratomas. Although other suicide gene-based strategies to avoid tumorigenesis have been described in the literature, none thus far has also provided the means to selectively preserve the cells of interest. Our results are the basis for ongoing research focused on the generation of clinical-grade hPSCs in which the integration of these constructs is targeted to safe genomic harbors, minimizing the risk of insertional mutagenesis and ensuring the selection of single-copy integrations. hPSC lines engineered in this fashion would be considered safe for transplantation.