Angiotensin-converting enzyme 2 in peripheral lung club cells modulates the susceptibility to SARS-CoV-2 in chronic obstructive pulmonary disease.

Accumulating evidence has confirmed that chronic obstructive pulmonary disease (COPD) is a risk factor for development of severe pathological changes in the peripheral lungs of patients with COVID-19. However, the underlying molecular mechanisms remain unclear. Because bronchiolar club cells are crucial for maintaining small airway homeostasis, we sought to explore whether the altered susceptibility to SARS-CoV-2 infection of the club cells might have contributed to the severe COVID-19 pneumonia in COPD patients. Our investigation on the quantity and distribution patterns of angiotensin-converting enzyme 2 (ACE2) in airway epithelium via immunofluorescence staining revealed that the mean fluorescence intensity of the ACE2-positive epithelial cells was significantly higher in club cells than those in other epithelial cells (including ciliated cells, basal cells, goblet cells, neuroendocrine cells, and alveolar type 2 cells). Compared with nonsmokers, the median percentage of club cells in bronchiolar epithelium and ACE2-positive club cells was significantly higher in COPD patients. In vitro, SARS-CoV-2 infection (at a multiplicity of infection of 1.0) of primary small airway epithelial cells, cultured on air-liquid interface, confirmed a higher percentage of infected ACE2-positive club cells in COPD patients than in nonsmokers. Our findings have indicated the role of club cells in modulating the pathogenesis of SARS-CoV-2-related severe pneumonia and the poor clinical outcomes, which may help physicians to formulate a novel therapeutic strategy for COVID-19 patients with coexisting COPD.

[Expression of HOXC4 gene during early development in zebrafish].

OBJECTIVE: To investigate the mechanism of HOXC4 gene during early development in zebrafish, study it's expression in hematopoiesis system with whole mount in situ hybridization (WISH), then make a foundation work for further study of HOXC4 gene in hematopoiesis development. METHODS: The total RNA of different phases of zebrafish embryos was extracted, and a fragment of HOXC4 gene was cloned with RT-PCR, then HOXC4 gene fragment and pCS2 was digested with BamH I and Xho I restriction enzyme, after that HOXC4 gene fragment was inserted into pCS2+ vector. After confirming the constructed plasmid, the digoxingenin-labeled anti-sence mRNA probe of HOXC4 gene was synthesized in vitro by using T3 RNA polymerase, the exprression pattern of HOXC4 during zebrafish embryogenesis using anti-sence probe with WISH was conducted. RESULTS: HOXC4 gene was cloned by RT-PCR and HOXC4-pCS2+ plasmid was constructed and confirmed, expression of HOXC4 showed that it was expressed highly in nervous system of wild-type (WT) Tuebingen zebrafish. CONCLUSION: The expression pattern of HOXC4 during early development in zebrafish was obtained, and it is very important for further study of HOXC4 gene function in zebrafish.

[Expression pattern of hoxd3 gene during early development of wild-type zebrafish embryos].

OBJECTIVE: To investigate the expression pattern of hoxd3 gene during early embryogenesis and angiogenesis of wild-type zebrafish. METHODS: Total RNA was extracted from embryos of zebrafish in different development stages by trizol. The cDNA of hoxd3 gene was amplified by RT-PCR. The RT-PCR product was ligated to pCS(2+) vector by T4 DNA ligatase polymerase and sequenced. T3 RNA polymerase in vitro transcription system was used to obtain the probe of digoxin-labeled anti-sense mRNA of hoxd3 gene. The expression pattern of hoxd3 was detected by whole embryo in situ hybridization (WISH) with anti-sense mRNA probe. RESULTS: pCS(2+)-hoxd3 plasmid was successfully constructed, which was used to prepare anti-sense mRNA probe of hoxd3 in vitro. Expression pattern of hoxd3 gene was detected by WISH during zebrafish early embryogenesis and angiogenesis. It was observed that hoxd3 mRNA was expressed at the junction region of midbrain and hindbrain in wild-type zebrafish in embryos at 24 ≊72h postfertilization(hpf). CONCLUSION: hoxd3 gene is mainly expressed in nervous system of wide-type zebrafish embryos.