A Matched Survival Analysis of Lung Transplant Recipients With Coronavirus Disease 2019-Related Respiratory Failure.

BACKGROUND: Lung transplantation is an acceptable and potentially life-saving treatment option for coronavirus disease 2019 (COVID-19)-induced acute respiratory distress syndrome and pulmonary fibrosis. This study was conducted to determine whether recipients of lung transplantation (LT) for COVID-19-related lung disease have comparable outcomes to other recipients with a similar level of lung dysfunction. METHODS: The Organ Procurement and Transplant Network database was queried for adult LT candidates between 2006 and 2021. Recipients with COVID-19-related respiratory failure were matched 1:2 using a nearest-neighbor algorithm. Kaplan-Meier methods with log-rank tests were used to compare long-term survival. A proportional hazards model was used to calculate risk of death. RESULTS: A total of 37,333 LT candidates from all causes were compared with 334 candidates from COVID-19-related respiratory failure. COVID-19 recipients were more likely to be younger (50 vs 57 years, P < .001), male (79% vs 60%, P < .001), require extracorporeal membrane oxygenation (56.3% vs 4.0%, P < .001), and have worse lung function (lung allocation score, 82.4 vs 47.8; P < .001) at transplantation. Subsequently, 227 COVID-19 recipients were matched with 454 controls. Patients who received a transplant for COVID-19 had similar rates of mechanical ventilation, extracorporeal membrane oxygenation, postoperative complications, and functional status at discharge compared with controls. There was no difference in overall survival or risk of death from COVID-19 (hazard ratio, 0.82; 95% CI, 0.45-1.53; P = .54). CONCLUSIONS: Six-month survival for recipients of LT for COVID-19-related respiratory failure was comparable to that of other LT recipients.

Krt14 and Krt15 differentially regulate regenerative properties and differentiation potential of airway basal cells.

Keratin expression dynamically changes in airway basal cells (BCs) after acute and chronic injury, yet the functional consequences of these changes on BC behavior remain unknown. In bronchiolitis obliterans (BO) after lung transplantation, BC clonogenicity declines, which is associated with a switch from keratin15 (Krt15) to keratin14 (Krt14). We investigated these keratins' roles using Crispr-KO in vitro and in vivo and found that Krt14-KO and Krt15-KO produce contrasting phenotypes in terms of differentiation and clonogenicity. Primary mouse Krt14-KO BCs did not differentiate into club and ciliated cells but had enhanced clonogenicity. By contrast, Krt15-KO did not alter BC differentiation but impaired clonogenicity in vitro and reduced the number of label-retaining BCs in vivo after injury. Krt14, but not Krt15, bound the tumor suppressor stratifin (Sfn). Disruption of Krt14, but not of Krt15, reduced Sfn protein abundance and increased expression of the oncogene dNp63a during BC differentiation, whereas dNp63a levels were reduced in Krt15-KO BCs. Overall, the phenotype of Krt15-KO BCs contrasts with Krt14-KO phenotype and resembles the phenotype in BO with decreased clonogenicity, increased Krt14, and decreased dNp63a expression. This work demonstrates that Krt14 and Krt15 functionally regulate BC behavior, which is relevant in chronic disease states like BO.

Development and characterization of ferret ex vivo tracheal injury and cell engraftment model.

The field of airway biology research relies primarily on in vitro and in vivo models of disease and injury. The use of ex vivo models to study airway injury and cell-based therapies remains largely unexplored although such models have the potential to overcome certain limitations of working with live animals and may more closely replicate in vivo processes than in vitro models can. Here, we characterized a ferret ex vivo tracheal injury and cell engraftment model. We describe a protocol for whole-mount staining of cleared tracheal explants, and showed that it provides a more comprehensive structural overview of the surface airway epithelium (SAE) and submucosal glands (SMGs) than 2D sections, revealing previously underappreciated structural anatomy of tracheal innervation and vascularization. Using an ex vivo model of tracheal injury, we evaluated the injury responses in the SAE and SMGs that turned out to be consistent with published in vivo work. We used this model to assess factors that influence engraftment of transgenic cells, providing a system for optimizing cell-based therapies. Finally, we developed a novel 3D-printed reusable culture chamber that enables live imaging of tracheal explants and differentiation of engrafted cells at an air-liquid interface. These approaches promise to be useful for modeling pulmonary diseases and testing therapies. Graphical abstract1,2. We describe here a method for differential mechanical injury of ferret tracheal explants that can be used to evaluate airway injury responses ex vivo. 3. Injured explants can be cultured at ALI (using the novel tissue-transwell device on the right) and submerged long-term to evaluate tissue-autonomous regeneration responses. 4. Tracheal explants can also be used for low throughput screens of compounds to improve cell engraftment efficiency or can be seeded with particular cells to model a disease phenotype. 5. Lastly, we demonstrate that ex vivo-cultured tracheal explants can be evaluated by various molecular assays and by immunofluorescent imaging that can be performed live using our custom-designed tissue-transwell.