The pulmonary vasculature in lethal COVID-19 and idiopathic pulmonary fibrosis at single cell resolution

Aims

SARS-CoV-2 infection causes COVID-19, which in severe cases evokes life-threatening acute respiratory distress syndrome (ARDS). Transcriptome signatures and the functional relevance of non-vascular cell types (e.g. immune and epithelial cells) in COVID-19 are becoming increasingly evident. However, despite its known contribution to vascular inflammation, recruitment/invasion of immune cells, vascular leakage and perturbed hemostasis in the lungs of severe COVID-19 patients, an in-depth interrogation of the endothelial cell (EC) compartment in lethal COVID-19 is lacking. Moreover, progressive fibrotic lung disease represents one of the complications of COVID-19 pneumonia and ARDS. Analogous features between idiopathic pulmonary fibrosis (IPF) and COVID-19 suggest partial similarities in their pathophysiology, yet, a head-to-head comparison of pulmonary cell transcriptomes between both conditions has not been implemented to date.

Methods and Results

We performed single nucleus RNA-seq (snRNA-seq) on frozen lungs from 7 deceased COVID-19 patients, 6 IPF explant lungs and 12 controls. The vascular fraction, comprising 38,794 nuclei, could be subclustered into 14 distinct EC subtypes. Non-vascular cell types, comprising 137,746 nuclei, were subclustered and used for EC-interactome analyses. Pulmonary ECs of deceased COVID-19 patients showed an enrichment of genes involved in cellular stress, as well as signatures suggestive of dampened immunomodulation and impaired vessel wall integrity. In addition, increased abundance of a population of systemic capillary and venous ECs was identified in COVID-19 and IPF. COVID-19 systemic ECs closely resembled their IPF counterparts, and a set of 30 genes was found congruently enriched in systemic ECs across studies. Receptor-ligand interaction analysis of ECs with non-vascular cell types in the pulmonary micro-environment revealed numerous previously unknown interactions specifically enriched/depleted in COVID-19 and/or IPF.

Conclusions

This study uncovered novel insights into the abundance, expression patterns and interactomes of EC subtypes in COVID-19 and IPF, relevant for future investigations into the progression and treatment of both lethal conditions.

Translational perspective

While assessing clinical and molecular characteristics of severe and lethal COVID-19 cases, the vasculature’s undeniable role in disease progression has been widely acknowledged. COVID-19 lung pathology moreover shares certain clinical features with late-stage IPF – yet an in-depth interrogation and direct comparison of the endothelium at single-cell level in both conditions is still lacking. By comparing the transcriptomes of ECs from lungs of deceased COVID-19 patients to those from IPF explant and control lungs, we gathered key insights the heterogeneous composition and potential roles of ECs in both lethal diseases, which may serve as a foundation for development of novel therapeutics.

Radiologic and pathologic response to neoadjuvant chemotherapy predicts survival in patients undergoing the liver-first approach for synchronous colorectal liver metastases

PURPOSE

To investigate the short- and long-term outcomes of liver first approach (LFA) in patients with synchronous colorectal liver metastases (CRLM), evaluating the predictive factors of survival.

METHODS

Sixty-two out of 301 patients presenting with synchronous CRLM underwent LFA between 2007 and 2016. All patients underwent neoadjuvant chemotherapy. After neoadjuvant treatment patients were re-evaluated according to the Response Evaluation Criteria in Solid Tumors (RECIST). Liver resection was scheduled after 4-6 weeks. Changes in non-tumoral parenchyma and the tumor response according to the Tumor Regression Grade score (TRG) were assessed on surgical specimens. Primary tumor resection was scheduled 4-8 weeks following hepatectomy.

RESULTS

Five patients out of 62 (8.1%) showed "Progressive Disease" at re-evaluation after neoadjuvant chemotherapy, 22 (35.5%) showed "Stable Disease" and 35 (56.5%) "Partial Response"; of these latter, 29 (82%) showed histopathologic downstaging. The 5-year survival (OS) rate was 55%, while the 5-year disease-free survival (DFS) rate was 16%. RECIST criteria, T-stage, N-stage and TRG were independently associated with OS. Bilobar presentation of disease, RECIST criteria, R1 margin and TRG were independently associated with DFS. Patients with response to neoadjuvant chemotherapy had better survival than those with stable or progressive disease (radiological response 5-y OS: 65% vs. 50%; 5-y DFS: 20% vs. 10%; pathological response 5-y OS: 75% vs. 56%; 5-y DFS: 45% vs. 11%).

CONCLUSIONS

LFA is an oncologically safe strategy. Selection is a critical point, and the best results in terms of OS and DFS are observed in patients having radiological and pathological response to neoadjuvant chemotherapy.