Tracheal delivery of HO-1-modified human umbilical cord-derived mesenchymal stem cells treats pulmonary arterial hypertension by enhancing pulmonary antioxidant and anti-inflammatory responses.

OBJECTIVE: Pulmonary arterial hypertension (PAH) is a life-threatening cardiovascular disease, with current treatments only alleviating symptoms. Mesenchymal stem cells (MSCs) possess immune-regulatory and reparative properties, and HO-1-modified MSCs enhance their anti-inflammatory and antioxidant effects. This study aims to investigate the potential of tracheal delivery of HO-1-modified MSCs for the treatment of PAH.

METHODS: This study first assessed the levels of inflammation and oxidative stress in the lung tissue pathology of healthy donors and IPAH patients, detecting F4/80, IL-6, and the oxidative stress marker 8-OHdG. Subsequently, in MCT-induced rat and hypoxia-exposed mouse models, we evaluated lung tissue sections for HE staining and α-SMA immunohistochemistry, along with antioxidant enzymes (SOD, CAT, GSH) and inflammatory factors (TNF-α, IL-18, IL-6, IL-1β) at 1, 2, 3, 4, and 5 weeks to assess the effects of various treatments. Next, we compared the anti-inflammatory and antioxidant capacities of HO-1-modified MSCs derived from umbilical cord (UC-MSCs) and adipose tissue (AD-MSCs), selecting the best cell intervention strategy. Using in vivo imaging, we assessed the cell homing of intravenously injected cells and drug retention after tracheal delivery. After tracheal delivery of HO-1-MSCs at 3, 4, and 5 weeks, we analyzed IHC staining for α-SMA, right heart catheterization, lung tissue inflammation, and antioxidant stress markers to identify the optimal intervention window. The efficacy was also compared with traditional HO-1 pharmacological agonists. Finally, the effects of HO-1-MSCs on vascular cells (PAECs, PASMCs) and immune cells (bone marrow macrophages, myeloid-derived neutrophils) in vivo were further explored to evaluate their potential and mechanisms in PAH treatment.

RESULTS: Compared to donor controls, IPAH patient lung tissues exhibited significant inflammation and oxidative stress, with increased macrophage infiltration and elevated levels of IL-6 and 8-OHdG. In MCT rat and hypoxia mouse models, PAH development was associated with vascular remodeling, persistent inflammation, and oxidative stress. UC-MSCs showed stronger anti-inflammatory and antioxidant effects than AD-MSCs. Tracheal delivery of HO-1-MSCs significantly improved outcomes at weeks 3 and 4, reversing pulmonary vascular remodeling, reducing pulmonary artery pressure, inhibiting IL-6 and IL-18 expression, and restoring antioxidant enzyme activity (SOD and CAT). Compared to traditional HO-1 agonists, HO-1-MSCs demonstrated superior efficacy. Additionally, HO-1-MSCs effectively inhibited PAECs proliferation, suppressed the activation of the ERK/AKT pathway, reduced PASMCs proliferation and migration, significantly decreased neutrophil activation, and promoted M2 macrophage polarization while reducing the M1 macrophage population.

CONCLUSION: Tracheal delivery of HO-1-(UC)-MSCs effectively alleviates inflammation and oxidative stress in PAH, improves vascular remodeling and pulmonary artery pressure, and offers a promising new therapeutic strategy for PAH treatment.