Table 1.

List of the studies investigating the expression of ACE2 in pancreatic islets and β-cells

Ref	Study design	Method of ACE2 detection	Main findings
Yang et al16	Pancreatic sections from a 43-year-old male brain-dead organ donor.	Immunohistochemical staining with unspecified ACE2 antibody	Strong staining of ACE2 in pancreatic islets and weak in exocrine tissues.
Liu et al	A public database (GTEx) database (https://gtexportal.org) and two ssRNA sequencing data sets of different endocrine cells.	mRNA expression level of ACE2	ACE2 expression is higher in the pancreas than in the lung. ACE2 is expressed in both the exocrine glands and islets.
Taneera et al15	Human pancreatic microarray expression data from 67 donors	mRNA expression in whole islets	ACE2 is expressed at lower levels compared to ADAM17 or TMPRSS2.
Fignani et al13	Fresh, FFPE, or frozen human pancreatic islets from seven brain-dead donors and one T1D donor. Also, the human cell line “EndoC-βH1” was included.	RNA seq, RT-PCR and immunohistochemical staining using anti-ACE2 (cat. MAB933, R&D, USA)	ACE2 preferentially expressed in subsets of β-cells and pancreas microvasculature pericytes. Moderate expression in rare ductal cells ACE2 expression in the human EndoC-βH1 cells was similar to that observed in human pancreatic islets.
Yang et al17	Human Pluripotent Stem-derived endocrine cell types and primary human islets.	Immunohistochemical staining with Anti-ACE2(Abcam, Cat# ab15348 and R & D Systems, Cat# AF933) and ssRNA sequencing	ACE2 protein is expressed in α and β derived cells but not in δ cells. ACE2 mRNA is expressed in human acinar cells, ductal cells, beta cells, alpha cells. Primary human β and α cells express ACE2 protein.
Kusmartseva et al14	Public ssRNA-seq from five datasets, including 22 non-diabetic and 8 T2D individuals. Pancreatic tissues from 56 non-diabetic, SARS-CoV-2 negative donors and three patients with fatal COVID-19.	scRNA-sequencing, fluorescence in situ hybridization, western blotting, and immunolocalization using anti-ACE2 (Abcam Cat# ab108252, Abcam Cat# ab15348;R&D Systems Cat# MAB933 and R&D Systems Cat# AF933)	ssRNA-seq revealed low ACE2 expression levels in the majority of islet cell subsets. Expression levels of ACE2 were not different between non-diabetic donors and T2D in any of the islet cell subtypes.
Coate et al12	Tow public bulk RNA-seq dataset from human islets, four ssRNA-seq from human pancreatic and pancreatic tissues normal donors with or without diabetes and COVID-19 decedents after autopsy.	RNA-seq and Immunohistochemical staining using anti-ACE2 (Atlas Antibodies Cat# HPA000288; Abcam Cat# ab15348; R&DCat# AF933 and R&DCat# MAB933).	ACE2 is not expressed in β cells at mRNA or protein levels ACE2 is expressed in exocrine tissue microvasculature and a subset of pancreatic ducts (Percicytes).
Müller et al36	Pancreatic islets from four different donors and EndoC-βH1 cells.	RT-PCR and immunohistochemistry staining using anti-ACE2 (Abcam Cat # ab15348 and ab92323)	SARS-CoV-2 infects human exocrine and endocrine pancreas ex vivo and in vivo resulted in reduced numbers of insulin-secretory granules in β-cells and impaired glucose-stimulated insulin secretion. SARS-CoV-2 nucleocapsid proteins detected in pancreatic exocrine and β-cells.