Background: The adult healthy human pancreas has been poorly studied given lack of indication to obtain tissue from the pancreas in the absence of disease and rapid postmortem degradation. Through our partnership with our local organ donation procurement facility, we leveraged cutting-edge transcriptomic and spatial technologies to further our understanding of this organ prior to the development of pathologic disease.

Methods: Acquisition of donor pancreata for research purposes was approved by the Gift of Life research review group. Donor pancreata not eligible for transplant or for whom there were no eligible recipients were collected for research. Upon arrival to the laboratory, the donor pancreas was dissected by a clinically-trained pancreatobiliary surgeon. The organ was dissected into head, body, and tail, with portions of each placed into DMEM media with 1%BSA/10μM Y27632 or 10% formalin for single cell sequencing or paraffin embedding, respectively. Single cell RNA sequencing was performed using the 10x Genomics Platform. Spatial transcriptomics of FFPE blocks was performed using the GeoMX Nanostring Platform.

Results: Histopathological analysis of the samples surprisingly revealed pancreatic intraepithelial neoplasia (PanIN) lesions in over half of our cohort of 60 samples. PanIN, the most common precursor lesion to pancreatic cancer, is microscopic and cannot be detected with conventional radiology; thus, its prevalence in the general healthy population was previously unknown. Integrating single cell RNA sequencing and spatial transcriptomics, we compared healthy pancreata to pancreatic cancer and observed distinct transcriptomic signatures in the microenvironment of these tissues, particularly in the fibroblast and myeloid compartments. Examination of the epithelial compartment of neoplastic lesions revealed that PanIN cells from healthy pancreata were remarkably similar in transcriptional profile to cancer cells, suggesting that neoplastic pathways are initiated early in tumorigenesis.

Conclusions: Through a unique pipeline of acquiring organ donor tissue with virtually no warm ischemic time, we discovered that neoplastic lesions in the healthy pancreas are quite common. Surprisingly, we found that PanINs transcriptionally bear high concordance to malignant tumors; conversely, the surrounding microenvironment was distinct. This finding raise the key question of why PanINs, found frequently in the population, rarely progress to pancreatic cancer which is exceedingly rare. Further investigation to identify mechanisms that promote PanIN progression to malignancy bears important clinical significance, as results may have the possibility to be leveraged for early detection and therapeutic strategies.

Histological structures identified in healthy donor pancreas and tumor-bearing pancreas delineating the progression of benign to malignant states in pancreatic cancer.

A) UMAP projection of single-cell RNA sequencing of donor pancreas, tumor, and tumor-adjacent “normal” tissue. B) Heatmap and pseudobulk PCA blots showing the distinct features of fibroblasts and myeloid cells in healthy versus tumor tissue.

Brian Griffith

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