# Anti-CD31 antibody preconditioning for enhancement of endothelial cell capture and vascularization: a novel strategy for bioengineering lung scaffolds

## TL;DR

A new method using an anti-CD31 antibody improves blood vessel formation in lab-grown lungs, potentially solving issues with current bioengineered lung grafts.

## Contribution

The first demonstration of using anti-CD31 antibody preconditioning to enhance vascularization in bioengineered lung scaffolds.

## Key findings

- Anti-CD31 antibody coating improved endothelial cell adhesion, viability, and expression of key genes like Claudin-1 and eNOS.
- Coated scaffolds showed better vascular structure and reduced leakage compared to uncoated scaffolds.
- Anti-CD31 coating reduced platelet aggregation and thrombus formation in both ex vivo and in vivo experiments.

## Abstract

Recellularization of acellular lung scaffolds is a promising technique for the generation of bioengineered lungs. However, at the present time, pre-clinical evaluation of bioengineered lungs shows graft failure likely due to thrombus formation and bleeding from bronchi. This is believed to be due to the impairment of barrier function, incomplete vascular endothelial cell coverage, and limited endothelial cell function. Therefore, efficient recellularization of the vasculature region of the lung scaffold with functional endothelial cells is an important goal. Coating of decellularized tissues, prior to recellularization has shown improved vascular endothelial cell coverage and endothelial cell function. Here, we report the first demonstration of preconditioning decellularized lung vasculature with an anti‑CD31 antibody to enhance re-endothelialization and vascular function in bioengineered lungs. Presence of the anti-CD31 antibody (Ab) coating resulted in enhanced cell adhesion, viability, proliferation and expression of key endothelial cell genes including Claudin-1 (CLDN) and Endothelial Nitric Oxide Synthase (eNOS). Re-endothelialized scaffolds in the anti-CD31 Ab coated group had morphological reconstitution of the pulmonary vasculature and a higher percentage of endothelialized blood vessels. Markedly greater fractions of intravascular Dextran in the anti-CD31 Ab coated group (20.7 ± 2.5% vesus 51.7 ± 2.5%, p = 0.0001) demonstrated reduced vascular endothelium leakage. Importantly, scaffolds in the anti-CD31 Ab coated group showed reduced platelet aggregation, measured via staining and quantification for integrin αIIb, when perfused with whole-blood ex vivo (17.7 ± 3.8% vs. 6.7 ± 1.5%, p = 0.04); and in vivo following a 30 min-left orthotopic left lung transplant in the mouse (14.7 ± 2.5% vs. 4.3 ± 1.5% in the anti-CD31 group (p = 0.004); suggesting reduced thrombus formation. Taken together, our results frame scaffold preconditioning with anti-CD31 Ab as a viable approach towards the generation of vascularized bioengineered lung constructs.

The online version contains supplementary material available at 10.1186/s13036-025-00593-x.