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A4465 - Long-Term Evaluation of Pulmonary Macrophage Transplantation Therapy in Csf2ra Gene-Deficient Mice, a Clinically Relevant Model of Hereditary Pulmonary Alveolar Proteinosis
Author Block: K. Shima1, T. Suzuki1, P. I. Arumugam1, N. Lachmann2, T. Moritz2, Y. Ma1, D. Black1, C. Chalk1, B. C. Carey1, B. C. Trapnell1; 1Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, 2Institute of Experimental Hematology, Hannover Medical School, Hannover, Germany.
Rationale: Hereditary pulmonary alveolar proteinosis (hPAP) is a severe pediatric lung disease caused by CSF2RA or CSF2RB mutations that disrupt GM-CSF receptor signaling and reduce alveolar macrophage (AM)-mediated surfactant clearance resulting in pulmonary alveolar surfactant accumulation and respiratory failure. We recently developed and validated Csf2ra gene-deficient (Csf2ra-/-) mice as an authentic model of human hPAP caused by CSF2RA mutations (which account for the majority of hPAP patients). Pulmonary macrophage transplantation (PMT) has shown promise in Csf2ra-/- mice as a novel therapy; however, long-term studies of safety and efficacy are needed before testing PMT as therapy in humans. Methods: Csf2ra-/- mice received one PMT treatment - intrapulmonary instillation of 2x106 syngeneic wild type (WT) bone marrow-derived macrophages (BMDMs) /mouse - and then a series of safety and efficacy studies were conducted over the following 8 months. Results: Administration of PMT of WT BMDMs into Csf2ra-/- recipients once resulted in efficient pulmonary engraftment of donor macrophages and replacement of endogenous AMs as demonstrated by the increase in percentage CD116+ BAL cells over time. BAL fluid turbidity (an excellent global measure of pulmonary surfactant accumulation/PAP disease severity) improved over time in PMT-treated mice compared to untreated mice in which hPAP progressively worsened. BAL biomarkers of hPAP (increased BAL levels of cholesterol, GM-CSF, M-CSF, MCP-1) were also reduced in PMT-treated compared to untreated Csf2ra-/- mice (n=6/group, p≤0.01). To evaluate the effects of the local milieu on differentiation of transplanted BMDMs, the transcriptome of BAL cells from Csf2a-/- mice was evaluated by RNAseq analysis eight months after a single PMT and compared to the results for age-matched untreated Csf2ra-/- and WT mice. Results of unsupervised hierarchical clustering analysis demonstrated AMs from PMT-treated mice co-clustered with AMs from age-matched WT and not untreated Csf2ra-/- mice. PMT had no effects on complete blood cell counts and body weight among groups of age-matched treated and untreated mice and was not associated with any cellular or molecular inflammatory responses. Conclusions: Results of long-term preclinical efficacy and safety studies in Csf2r-/- mice demonstrate that PMT therapy of hPAP is highly efficacious, durable, well tolerated and did not identify any safety concerns. One administration of PMT resulted in excellent pulmonary engraftment without preparative myeloablation. Interestingly, donor macrophages adopted the phenotype of WT AMs, not that of the Csf2ra-/- recipients into which they were transplanted confirming pulmonary GM-CSF is a critical determinate of AM specification.