Dysregulated alveolar epithelial cell progenitor function and identity in Hermansky-Pudlak syndrome pulmonary fibrosis.

Hermansky-Pudlak syndrome (HPS) is a genetic disorder associated with pulmonary fibrosis in specific subtypes, including HPS-1 and HPS-2. Single mutant HPS1 and HPS2 mice display increased fibrotic sensitivity while double mutant HPS1/2 mice exhibit spontaneous fibrosis with aging, which has been attributed to HPS mutations in alveolar epithelial type II (AT2) cells. Unifying mechanisms of AT2 cell dysfunction in genetic and sporadic fibrotic lung diseases remain unknown. Incorporating AT2 cell lineage tracing in HPS mice, we observed a progressive decline in AT2 cell numbers with aging and aberrant differentiation with increased AT2-derived alveolar epithelial type I cells. HPS AT2 cell proliferation was impaired ex vivo and in vivo , suggesting an intrinsic progenitor defect. Transcriptomic analysis of HPS AT2 cells revealed elevated expression of genes associated with aberrant differentiation and cellular senescence. Through lineage tracing and organoid modeling, we demonstrated that HPS AT2 cells were primed to persist in a Krt8 + reprogrammed transitional state, mediated by p53 activity. These findings suggest that pulmonary fibrosis in HPS may be driven by AT2 cell progenitor dysfunction in the setting of p53-mediated senescence, highlighting a novel potential therapeutic target in HPS and suggesting unifying mechanisms underlying HPS and other forms of pulmonary fibrosis.

Microstructured Hydrogels to Guide Self-Assembly and Function of Lung Alveolospheres.

Epithelial cell organoids have increased opportunities to probe questions on tissue development and disease in vitro and for therapeutic cell transplantation. Despite their potential, current protocols to grow these organoids almost exclusively depend on culture within 3D Matrigel, which limits defined culture conditions, introduces animal components, and results in heterogenous organoids (i.e., shape, size, composition). Here, a method is described that relies on hyaluronic acid hydrogels for the generation and expansion of lung alveolar organoids (alveolospheres). Using synthetic hydrogels with defined chemical and physical properties, human-induced pluripotent stem cell (iPSC)-derived alveolar type 2 cells (iAT2s) self-assemble into alveolospheres and propagate in Matrigel-free conditions. By engineering predefined microcavities within these hydrogels, the heterogeneity of alveolosphere size and structure is reduced when compared to 3D culture, while maintaining the alveolar type 2 cell fate of human iAT2-derived progenitor cells. This hydrogel system is a facile and accessible system for the culture of iPSC-derived lung progenitors and the method can be expanded to the culture of primary mouse tissue derived AT2 and other epithelial progenitor and stem cell aggregates.

STAT3-BDNF-TrkB signalling promotes alveolar epithelial regeneration after lung injury.

Alveolar epithelial regeneration is essential for recovery from devastating lung diseases. This process occurs when type II alveolar pneumocytes (AT2 cells) proliferate and transdifferentiate into type I alveolar pneumocytes (AT1 cells). We used genome-wide analysis of chromatin accessibility and gene expression following acute lung injury to elucidate repair mechanisms. AT2 chromatin accessibility changed substantially following injury to reveal STAT3 binding motifs adjacent to genes that regulate essential regenerative pathways. Single-cell transcriptome analysis identified brain-derived neurotrophic factor (Bdnf) as a STAT3 target gene with newly accessible chromatin in a unique population of regenerating AT2 cells. Furthermore, the BDNF receptor tropomyosin receptor kinase B (TrkB) was enriched on mesenchymal alveolar niche cells (MANCs). Loss or blockade of AT2-specific Stat3, Bdnf or mesenchyme-specific TrkB compromised repair and reduced Fgf7 expression by niche cells. A TrkB agonist improved outcomes in vivo following lung injury. These data highlight the biological and therapeutic importance of the STAT3-BDNF-TrkB axis in orchestrating alveolar epithelial regeneration.

Using selective lung injury to improve murine models of spatially heterogeneous lung diseases.

Many lung diseases, such as the acute respiratory distress syndrome (ARDS), display significant regional heterogeneity with patches of severely injured tissue adjacent to apparently healthy tissue. Current mouse models that aim to mimic ARDS generally produce diffuse injuries that cannot reproducibly generate ARDS's regional heterogeneity. This deficiency prevents the evaluation of how well therapeutic agents reach the most injured regions and precludes many regenerative medicine studies since it is not possible to know which apparently healing regions suffered severe injury initially. Finally, these diffuse injury models must be relatively mild to allow for survival, as their diffuse nature does not allow for residual healthy lung to keep an animal alive long enough for many drug and regenerative medicine studies. To solve all of these deficiencies in current animal models, we have created a simple and reproducible technique to selectively induce lung injury in specific areas of the lung. Our technique, catheter-in-catheter selective lung injury (CICSLI), involves guiding an inner catheter to a particular area of the lung and delivering an injurious agent mixed with nanoparticles (fluorescently and/or radioactively labeled) that can be used days later to track the location and extent of where the initial injury occurred. Furthermore, we demonstrate that CICSLI can produce a more severe injury than diffuse models, yet has much higher survival since CICSLI intentionally leaves lung regions undamaged. Collectively, these attributes of CICSLI will allow investigators to better study how drugs act within heterogeneous lung pathologies and how regeneration occurs in severely damaged lung tissue, thereby aiding the development of new therapies for ARDS and other heterogenous lung diseases.

Early stage lung cancer detection in systemic sclerosis does not portend survival benefit: a cross sectional study.

BACKGROUND: Systemic Sclerosis (SSc) is a rare connective tissue disorder associated with an increased risk of malignancy including lung cancer. METHODS: A single center review of all cases of lung cancer in patients with SSc was conducted. Clinical, radiographic, and detailed pathologic data was collected. Risk factors were compared with our center's SSc Registry. Cancer characteristics were compared with the National Cancer Institute SEER Cancer Statistics (NCI SEER) data. RESULTS: 17 cases were identified; the majority were females (82%) with the lung cancers diagnosed after the onset of SSc (88%). Tobacco use was identified in 65% of cases. Serologic testing showed 50% of cases were Scl-70 positive. Twelve cases had radiographic evidence of SSc lung involvement, however only 6 had restrictive physiology on pulmonary function testing. Thirteen cases had pulmonary nodules preceding lung cancer. Thirteen of the cancers were adenocarcinoma. Ten underwent molecular mutational profiling: 2/8 had KRAS mutation and 1/10 had EGFR mutation. More of the non-small cell lung cancers were diagnosed at localized disease (56%) than in the NCI SEER database. However, 5 years survival among the stage I cases was 25% versus an expected survival of 54%. CONCLUSIONS: The high proportion of adenocarcinomas seen in our study is different from that reported in the literature. Lung cancers were diagnosed at an early stage, likely due to our center's practice of radiographic screening for SSc associated lung involvement, however this did not confer a survival advantage. A high proportion of patients who developed lung cancer had interstitial lung disease.

Emergency department evaluations of non-percutaneous blood or body fluid exposures during cardiopulmonary resuscitation.

INTRODUCTION: The demography of healthcare workers (HCWs) and non-HCWs seeking medical care at emergency departments after a non-percutaneous potential exposure to human immunodeficiency virus (HIV) during cardiopulmonary resuscitation (CPR), the types and body locations of their exposures, the time elapsed from exposure to emergency department presentation, and usage of HIV-post-exposure prophylaxis (PEP) for these exposures are described. METHODS: A retrospective study of emergency department patients who were exposed to blood or body fluids during CPR in Rhode Island from January 1995-June 2001 was performed. The demography, characteristics of the exposure, and HIV-PEP usage for these patients were compared, and the elapsed time from exposure to evaluation in the emergency department was calculated. RESULTS: Of the 39 patients exposed to non-percutaneous blood or body fluid during CPR, 22 were healthcare workers (HCWs) and 17 were non-HCWs. Thirty-four patients sustained mucous membrane exposures. Most of the patients (69.2%) were exposed to saliva or sputum (p <0.001), experienced a mouth exposure (71.8%; p <0.0001) and presented to the emergency department within one day of their exposure (84.4%; p <0.0001). Three HCWs and no non-HCWs were offered HIV-PEP for their CPR exposure. Of the three HCWs offered PEP, two actually received it. CONCLUSIONS: Nearly half of the patients who presented with non-percutaneous exposures acquired during CPR were not HCWs. Most of the exposures were to saliva or sputum and occurred on their mucous membranes. Continuing education programs on maintaining universal precautions to prevent blood or body fluid exposures and appreciating the benign nature of most non-percutaneous exposures possible during CPR are needed.