Developing a vascularized islet-on-a-chip model

Maarten van Agen1, Ulgu Arslan2, Valeria Orlova2, Eelco de Koning1, Françoise Carlotti1

1Department of Internal Medicine, LUMC, Leiden.2Department of Anatomy and Embryology, LUMC, Leiden.

m.s.van_agen@lumc.nl

Background:

The interaction between endocrine cells and vasculature in pancreatic islets is of major importance for islet development and function. Isolation of islets results in a disrupted vasculature contributing to the challenge of long-term primary islets culture, thereby limiting further investigation into beta cell health and disease. Organ-on-a-chip platforms and iPSC (induced pluripotent stem cell) technology represent an opportunity to create a next-generation islet culture system, which would allow disease modelling and drug screening. Here we propose to set up a vascularized human islet-on-a-chip model.

Methods:

We investigated two approaches, with or without preliminary co-culture of the islets with endothelial cells. For the latter condition, primary human islets were individually cultured in microwells in the presence of mCherry-labelled hiPSC-derived endothelial cells (ECs) and human pericytes for 5 days. Viability was assessed by FDA/PI staining. Next, hiPSC-EC/islet clusters or control islets were mixed in a fibrin gel with 25,000 hiPSC-ECs and 5,000 pericytes, and subsequently loaded into a microfluidic chip (IdenTx, AIM biotech). The formation of a vascular network was monitored by confocal microscopy. Beta-cell function was assessed by a dynamic glucose-stimulation insulin secretion test (Biorep V5). Free-floating islets (standard culture) were used as an additional control.

Results:

During the co-culture step, we observed hiPSC-ECs migrating into the islets. Islet viability was stable (>90%) from day 3 onward. Next, loading of hiPSC-EC/islet clusters or control islets into the chip resulted in the formation of a vascular network similarly developed in both conditions. However, the vascular network penetrated the islets only in the hiPSC-EC/islet condition. Preliminary data indicate that islets loaded in the chip were still functional at 2 weeks post isolation, while free floating control islets were not anymore. Furthermore, hiPSC-EC/islet clusters showed an increased secretory capacity compared to the control islet-on-a-chip condition.

Conclusions:

We developed an islet-on-a-chip platform using primary human islets. The microenvironment appears to be beneficial for the maintenance of beta-cell function. Furthermore, pre-vascularization of primary human islets with endothelial cells further enhances the penetration of the vascular network which is associated with improved beta-cell function.