Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndromerelated coronavirus-2 (SARS-CoV-2) has affected millions of people globally. Clinically, it presents with mild flu-like symptoms in most cases but can cause respiratory failure in high risk population. With the aim of unearthing newer treatments, scientists all over the globe are striving hard to comprehend the underlying mechanisms of COVID-19. Several studies till date have indicated a dysregulated host immune response as the major cause of COVID-19 induced mortality. In this Perspective, we propose a key role of endothelium, particularly pulmonary endothelium in the pathogenesis of COVID-19. We draw parallels and divergences between COVID-19-induced respiratory distress and bacterial sepsis-induced lung injury and recommend the road ahead with respect to identification of endothelium-based biomarkers and plausible treatments for COVID-19.

ObjectiveGut lymphatic vessels are crucial in maintaining abdominal fluid homeostasis. We studied these vessels in clinical cirrhosis and explored effects of vascular endothelial growth factor-C (VEGF-C), a pro-lymphangiogenic factor, in experimental portal hypertension.DesignVascular endothelial growth factor receptor 3 (vegfr3)-positive lymphatic channels were enumerated in duodenal (D2) biopsies from cirrhotic patients. Vegfr3 antibody-tagged lipid nanocarriers were used to formulate novel nano-engineered (E-VEGF-C) molecule for targeted lymphangiogenesis of gut lymphatic vessels. The uptake of E-VEGF-C was evaluated in lymphatic endothelial cells (LyECs) in vitro and in vivo. The effects of E-VEGF-C were tested in cirrhotic and non-cirrhotic animal models of portal hypertension. Animals given nanocarriers alone served as vehicle. Mesenteric lymphatic vessel numbers/proliferation and drainage were analyzed. Abdominal ascites, hepatic and systemic hemodynamics was measured. Liver, duodenum, mesentery and plasma were examined.ResultsIn D2 biopsies, number of dilated vegfr3+ lymphatic vessels was significantly increased in decompensated as compared to compensated cirrhosis and correlated with presence of ascites. E-VEGF-C was efficiently taken up by the mesenteric LyECs. E-VEGF-C treated rats displayed a marked increase in the proliferation of mesenteric lymphatic vessels and drainage as compared to CCl4-vehicle. Ascites and mesenteric inflammation were markedly reduced in E-VEGF-C treated cirrhotic rats. Portal pressures were attenuated in both cirrhotic and non-cirrhotic portal hypertensive rats treated with E-VEGF-C as compared to respective vehicle groups.ConclusionE-VEGF-C molecule enhances mesenteric lymphangiogenesis and improves lymphatic vessel drainage, attenuating abdominal ascites and portal pressures. Targeted gut lymphangiogenesis may serve as an emerging therapy for portal hypertension.Significance of the StudyWhat is already known about this subject?Gut lymphatic vessels play crucial roles in maintaining fluid and immune homeostasis in the abdomen.An increased but dysfunctional gut lymphangiogenesis occurs to compensate for lymphatic insufficiency in patients with gut inflammatory diseases.Therapies aimed at enhancing lymphangiogenesis with growth factors such as VEGF-C constitute an effective strategy to improve lymphatic drainage and ameliorate inflammation in certain pathologies.Gut lymphatic vessels remain poorly characterized in patients with cirrhosis.What are the new findings?Dilated vegfr3+ lymphatic vessels are significantly increased in patients with decompensated as compared to compensated cirrhosis and correlated with presence of ascites.A nanoengineered pro-angiogenic molecule, E-VEGF-C with specificity for uptake by the gut lymphatic endothelial cells molecule enhances mesenteric lymphangiogenesis.E-VEGF-C improved lymphatic vessel drainage, attenuating abdominal ascites and portal pressures.How might it impact on clinical practice in the foreseeable future?Gut lymphangiogenesis is proposed as an innovative strategy for the management of ascites and portal hypertension.