Systematic Reviews
Copyright ©The Author(s) 2025. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Transplant. Sep 18, 2025; 15(3): 102383
Published online Sep 18, 2025. doi: 10.5500/wjt.v15.i3.102383
Islet dimension and its impact on transplant outcome: A systematic review
Sipra Rout, Pravash R Mishra, Appakalai N Balamurugan, Praveen Kumar Ravi
Sipra Rout, Pravash R Mishra, Praveen Kumar Ravi, Department of Anatomy, All India Institute of Medical Sciences, Bhubaneswar 751019, Odisha, India
Appakalai N Balamurugan, Wendy Novak Diabetes Institute, Norton Children's Hospital, Norton Healthcare, Louisville, KY 40202, United States
Appakalai N Balamurugan, Division of Pediatric Endocrinology, Department of Pediatrics, Pediatric Research Institute, University of Louisville, Louisville, KY 40202, United States
Co-corresponding authors: Appakalai N Balamurugan and Praveen Kumar Ravi.
Author contributions: Rout S and Ravi PK conducted the systematic review; Mishra PR and Balamurugan AN supervised the findings of this study; Balamurugan AN and Ravi PK contributed equally to this study as co-corresponding authors; Balamurugan AN provided the relevant photomicrograph to support the data; Ravi PK proposed to investigate the impact of islet size on the transplant outcome; all the authors discussed the results, and contributed to and approved the final manuscript.
Conflict-of-interest statement: All authors declare no conflict of interest in publishing the manuscript.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Praveen Kumar Ravi, MD, DNB, Assistant Professor, Department of Anatomy, All India Institute of Medical Sciences, Sijua, Patrapada, Bhubaneswar 751019, Odisha, India. praveenkumar1059@gmail.com
Received: October 15, 2024
Revised: February 19, 2025
Accepted: February 27, 2025
Published online: September 18, 2025
Processing time: 184 Days and 8.9 Hours
Abstract
BACKGROUND

Not all islet transplants desirably achieve insulin independence. This can be attributed to the microarchitecture and function of the islets influenced by their dimensions. Large islets enhance insulin secretion through paracrine effects but are more susceptible to hypoxic injury post-transplant, while small islets offer better viability and insulin independence. In vivo studies suggest large islets are essential for maintaining euglycemia, though smaller islets are typically preferred in transplantation for better outcomes.

AIM

To document the impact of islet dimension on clinical and preclinical transplant outcomes to optimize procedures.

METHODS

PubMed, Scopus and EMBASE platforms were searched for relevant literature up to 9 April 2024. Articles reported on either glucose-stimulated insulin-secreting (GSIS) capacity, islet viability and engraftment, or insulin independence based on the islet dimension were included. The risk of bias was measured using the Appraisal Tool for Cross-Sectional Studies. Extracted data was analyzed via a narrative synthesis.

RESULTS

Nineteen studies were included in the review. A total of sixteen studies reported the GSIS, of which nine documented the increased insulin secretion in the small islet, where the majority reported insulin secretion per islet equivalent (IEQ). Seven studies documented increased GSIS in large-sized islets that measure insulin secretion per cell or islet. All the articles that compared small and large islets reported poor viability and engraftment of large islets.

CONCLUSION

Small islets with a diameter < 125 µm have desired transplantation outcomes due to their better survival following isolation. Large-sized islets receive blood supply directly from arterioles in vivo to meet their higher metabolic demands. The large islet undergoes central necrosis soon after the isolation (devascularization); failing to maintain the viability and glucose stimuli leads to a decline in GSIS and the overall function of the islet. Improved preservation of large islets after islet isolation, enhances the islet yield (IEQ), thereby reducing the likelihood of failed islet isolation and potentially improves transplant outcome.

Keywords: Islet diameter; Transplantation; Islet size; Insulin-secretion; Viability; Engraftment; Insulin independence; Islet transplantation

Core Tip: This systematic review examines the impact of islet size on transplantation outcomes in clinical and preclinical studies. Small islets (< 125 µm) demonstrate superior viability, glucose-stimulated insulin secretion, and engraftment post-transplantation compared to large islets, which suffer from hypoxic injury and poor viability. However, large islets, essential for maintaining euglycemia in vivo, require improved preservation techniques to enhance their post-isolation survival and function. Optimizing islet size and preservation could significantly improve the success of islet transplantation and insulin independence.