Abstract Introduction and Background Endothelial dysfunction is a key driver of graft-versus-host disease (GVHD)-related lung complications following allogeneic hematopoietic stem cell transplantation (HSCT). Pulmonary endothelial cells (ECs) are particularly vulnerable, and their loss contributes to idiopathic pneumonia syndrome and diffuse alveolar hemorrhage. The transcription factor FOXF1 maintains endothelial stability and regenerative capacity, yet its role in transplant-associated vascular injury remains unclear. We hypothesized that allogeneic HSCT leads to pulmonary EC depletion and FOXF1 downregulation, and that restoring FOXF1 expression via nanoparticle-based minicircle delivery could rescue endothelial injury. Methods Juvenile C57BL/6 mice (postnatal day 8-10) underwent total-body irradiation (13 Gy, split dose) followed by retro-orbital infusion of 3 × 106 bone marrow cells from either syngeneic or allogeneic (BALB/c) donors. Non-irradiated mice served as controls. Lung and blood samples were collected on days 7, 14, and 28 post-transplant. Pulmonary ECs (CD45−/CD31+) were quantified by flow cytometry, and Foxf1 and Cdh5 expression were analyzed by qPCR. To evaluate therapeutic rescue, allogeneic recipients received an intravenous injection of lipid nanoparticles carrying minicircle FOXF1 DNA on day 14. Survival, body weight, and EC recovery were subsequently monitored. Results Allogeneic HSCT recipients exhibited reduced survival, weight loss, and splenomegaly consistent with GVHD. Donor engraftment was confirmed by day 14. Flow cytometry revealed marked depletion of pulmonary ECs in allogeneic recipients at all time points, accompanied by sustained Foxf1 downregulation. Syngeneic recipients showed only transient Foxf1 suppression with full recovery by day 28. Notably, intravenous administration of minicircle FOXF1 nanoparticles significantly improved survival, restored pulmonary EC numbers, and reactivated endothelial Foxf1 expression compared with the empty nanoparticle control group. Conclusions Allogeneic HSCT induces severe pulmonary endothelial injury and persistent Foxf1 suppression, which can be reversed by nanoparticle-mediated FOXF1 gene delivery. These findings identify FOXF1 as both a mechanistic regulator and a therapeutic target in transplant-associated endothelial dysfunction. Nanoparticle-based FOXF1 restoration represents a promising strategy to preserve vascular integrity and improve outcomes following pediatric HSCT. This abstract is funded by: R01-HL158659-01
Lan et al. (Fri,) studied this question.