# CD99-targeted immunomagnetic negative selection: A novel strategy for high-purity pancreatic islet isolation in murine models

## TL;DR

A new method using CD99-targeted immunomagnetic selection improves the purity and quality of isolated pancreatic islets for diabetes research in mice.

## Contribution

A novel immunomagnetic negative selection protocol using CD99 for high-purity islet isolation in murine models.

## Key findings

- Islet purity increased from 10.4 ± 3.9% to 93.0 ± 1.4% using CD99-targeted selection.
- Purified islets showed structural integrity and glucose-stimulated insulin secretion comparable to conventional methods.
- CD99-purified islets effectively reversed diabetes in a syngeneic transplantation model.

## Abstract

Islet transplantation represents a promising therapeutic approach for type 1 diabetes through restoration of endogenous insulin production. However, efficient purification of islets from surrounding exocrine tissue remains a critical challenge, as current methodologies often compromise purity, yield, or islet viability.

We exploited the differential expression of CD99 between murine pancreatic exocrine tissue (high expression) and islets (negligible expression) to develop a novel immunomagnetic negative selection protocol. Expression patterns were validated using immunofluorescence, immunohistochemistry, and western blot. Subsequently, streptavidin-conjugated magnetic beads coupled with biotinylated anti-CD99 antibodies were employed to selectively deplete CD99-positive exocrine cells from pancreatic digests, thereby enriching viable islets.

This approach achieved a remarkable increase in islet purity from 10.4 ± 3.9% to 93.0 ± 1.4% (P < 0.0001). Purified islets maintained structural integrity and demonstrated robust glucose-stimulated insulin secretion in vitro, comparable to islets isolated via conventional Ficoll density gradient centrifugation (P > 0.05). In a syngeneic transplantation model, 400 islet equivalents effectively reversed streptozotocin-induced diabetes, with therapeutic efficacy equivalent to Ficoll-purified islets (P > 0.05).

Our CD99-targeted immunomagnetic negative selection offers a novel, highly specific, and effective alternative for obtaining high-quality islets, as demonstrated by their excellent functional performance both in vitro and in vivo.