Lymphatic System In The Esophagus

Objectives: Esophageal squamous cell carcinoma(ESCC)is one of the most malignant cancers,with its morbidity and mortality ranking among the top ten worst cancers in the world.Lymphatic metastasis is the main mode of metastasis of ESCC cells.Distant metastasis is one of the main reasons for the failure of surgical treatment.It remains unknown how lymphatic metastasis of ESCC takes place.1.This study was aimed to discover the esophageal lymphatic vessels in mouse and human esophagus by immunohistochemical staining.2.Lymphatic vessels in the esophagus of ProxTom mouse was observed under a laser confocal microscope.3.The positional relationship between ESCC cells and blood vessels in metastatic lymph nodes of ESCC patients was observed.Methods:1.Expression of two lymphatic endothelial cell markers,PROX1 and LYVE1,was detected by immunohistochemistry in the esophagus of wild-type mice.2.Expression of PROX1 and LYVE1 was detected by immunohistochemistry in normal human esophagus with tissue samples harvested from patients with ESCC.3.Frozen sections of ProxTom mouse esophagus was stained with DAPI and observed under laser confocal microscopy.4.The genotype of ProxTom mice was validated by polymerase chain reaction(PCR).5.Paraffin sections of metastatic lymph nodes obtained from patients with ESCC were double stained with anti-CD31 and pan-Cytokeratin to show the positional relationship between the blood vessels and ESCC cells in the metastatic lymph nodes.Results:1.The expression patterns of PROX1 and LYVE1 in the mouse esophagus were similar to those of normal human esophagus.2.Expression of LYVE1 in the adult mouse esophagus was the same as that in young mouse esophagus(10-day-old).3.Immunohistochemical staining of LYVE1 showed that,Lymphatic vessels were mainly distributed in the muscular layer of mouse esophagus.The density,morphology and location of esophageal lymphatic vessels in wild-type mice were similar to those in normal human esophagus.4.With ProxTom mouse esophagus observed under a laser confocal microscope,we found that,Esophageal lymphatic vessels in ProxTom mice were the same as those in wild-type mice.Mouse esophageal lymphatic vessels formed a network.5.PCR confirmed that ProxTom mice carried the PROX1-tdTomato transgene.6.CD31 and pan-Cytokeratin double staining of metastatic lymph nodes from patients with ESCC suggested that ESCC cells might enter blood circulation through the blood vessels in the lymph nodes.Conclusions:1.Mouse esophageal lymphatic vessels are mainly distributed in the muscle layer as a network.Mouse esophagus and human esophagus share similarity in the location,density and morphology of lymphatic vessels.2.Cancer cells in the metastatic lymph nodes of patients with ESCC may spread through blood vessels inside lymph nodes.