Transplantation of alveolar macrophages improves the efficacy of endothelial progenitor cell therapy in mouse model of bronchopulmonary dysplasia.

Bronchopulmonary dysplasia (BPD) is a severe complication of preterm births, which develops due to exposure to supplemental oxygen and mechanical ventilation. Published studies demonstrated that the number of endothelial progenitor cells (EPC) is decreased in mouse and human BPD lungs and that adoptive transfer of EPC is an effective approach in reversing the hyperoxia-induced lung damage in mouse model of BPD. Recent advancements in macrophage biology identified the specific subtypes of circulating and resident macrophages mediating the developmental and regenerative functions in the lungs. Several studies reported the successful application of macrophage therapy in accelerating the regenerative capacity of damaged tissues and enhancing the therapeutic efficacy of other transplantable progenitor cells. In the present study, we explored the efficacy of combined cell therapy with EPC and resident alveolar macrophages (rAM) in hyperoxia-induced BPD mouse model. rAM and EPC were purified from neonatal mouse lungs and were used for adoptive transfer to the recipient neonatal mice exposed to hyperoxia. Adoptive transfer of rAM alone did not result in engraftment of donor rAM into the lung tissue but increased the mRNA level and protein concentration of proangiogenic CXCL12 chemokine in recipient mouse lungs. Depletion of rAM by chlodronate-liposomes decreased the retention of donor EPC after their transplantation into hyperoxia-injured lungs. Adoptive transfer of rAM in combination with EPC enhanced the therapeutic efficacy of EPC as evidenced by increased retention of EPC, increased capillary density, improved arterial oxygenation, and alveolarization in hyperoxia-injured lungs. Dual therapy with EPC and rAM has promise in human BPD.NEW & NOTEWORTHY Recent studies demonstrated that transplantation of lung-resident endothelial progenitor cells (EPC) is an effective therapy in mouse model of bronchopulmonary dysplasia (BPD). However, key factors regulating the efficacy of EPC are unknown. Herein, we demonstrate that transplantation of tissue-resident alveolar macrophages (rAM) increases CXCL12 expression in neonatal mouse lungs. rAM are required for retention of donor EPC in hyperoxia-injured lungs. Co-transplantation of rAM and EPC improves the efficacy of EPC therapy in mouse BPD model.

Immunomodulation of susceptibility to pneumococcal pneumonia infection in mouse lungs exposed to carbon nanoparticles via dysregulation of innate and adaptive immune responses.

Carbon nanotubes (CNTs) are emerging pollutants of occupational and environmental health concern. While toxicological mechanisms of CNTs are emerging, there is paucity of information on their modulatory effects on susceptibility to infections. Here, we investigated cellular and molecular events underlying the effect of multi-walled CNT (MWCNT) exposure on susceptibility to Streptococcus pneumoniae infection in our 28-day sub-chronic exposure mouse model. Data indicated reduced phagocytic function in alveolar macrophages (AMs) from MWCNT-exposed lungs evidenced by lower pathogen uptake in 1-h infection assay. At 24-h post-infection, intracellular pathogen count in exposed AMs showed 2.5 times higher net increase (2-fold in vehicle- versus 5-fold in MWCNT-treated), indicating a greater rate of intracellular multiplication and/or survival due to MWCNT exposure. AMs from MWCNT-exposed lungs exhibited downregulation of pathogen-uptake receptors CD163, Phosphatidyl-serine receptor (Ptdsr), and Macrophage scavenger receptors class A type 1 (Msr1) and type 2 (MSr2). In whole lung, MWCNT exposure shifted the macrophage polarization state towards the immunosuppressive phenotype M2b and increased the CD11c+ dendritic cell population required to activate the adaptive immune response. Notably, the MWCNT pre-exposure dysregulated T-cell immunity, evidenced by diminished CD4 and Th17 response, and exacerbated Th1 and Treg responses (skewed Th17/Treg ratio), thereby favoring the pneumococcal infection. Overall, these findings indicated that MWCNT exposure compromises both innate and adaptive immunity leading to diminished host lung defense against pneumonia infection. To our knowledge, this is the first report on an immunomodulatory role of CNT pre-exposure on pneumococcal infection susceptibility due to dysregulation of both innate and adaptive immunity targets.

Cytotoxicity and Characterization of Ultrafine Particles from Desktop Three-Dimensional Printers with Multiple Filaments.

Previous research has indicated that ultrafine particles (UFPs, particles less than 100 nm) emitted from desktop three-dimensional (3D) printers exhibit cytotoxicity. However, only a limited number of particles from different filaments and their combinations have been tested for cytotoxicity. This study quantified the emissions of UFPs from a commercially available filament extrusion desktop 3D printer using three different filaments, including acrylonitrile butadiene Styrene (ABS), thermoplastic polyurethane (TPU), and polyethylene terephthalate glycol (PETG). In this study, controlled experiments were conducted where the particles emitted were used to expose cells grown in an air-liquid interface (ALI) system. The ALI exposures were utilized for in vitro characterization of particle mixtures, including UFPs from a 3D printer. Additionally, a lactate dehydrogenase (LDH) assay was used to evaluate the cytotoxic effects of these UFPs. A549 cells were exposed at the ALI to UFPs generated by an operational 3D printer for an average of 45 and 90 min. Twenty-four hours post-exposure, the cells were analyzed for percent cytotoxicity in a 24-well ALI insert (LDH assay). UFP exposure resulted in diminished cell viability, as evidenced by significantly increased LDH levels. The findings demonstrate that ABS has the most significant particle emission. ABS was the only filament that showed a significant difference compared to the high efficiency particulate arrestance (HEPA) following 90 min of exposure (p-value < 0.05). Both ABS and PETG exhibited a significant difference compared to the HEPA control after 45 min of exposure. A preliminary analysis of potential exposure to these products in a typical environment advises caution when operating multiple printer and filament combinations in poorly ventilated spaces or without combined gas and particle filtration systems.