Study On Three-dimensional Modeling Of Spatio-temporal Development Of Lymphatic Vessels In Early Human Embryo

Purpose: Lymphatic system diseases are increasing year by year,and many pathological changes are closely related to the abnormal development of lymphatic vessels.A correct understanding of the development and evolution of lymphatic vessels is of great significance for clinical diagnosis and treatment and prevention of related diseases.The discovery of meningeal lymphatic vessels subverts the concept of "no lymphatic vessels in the brain" in traditional textbooks.Compared with blood vessels,the study of lymphatic vessels lags far behind,especially little is known about the development and evolution of lymphatic vessels in human embryos,and the hand drawing of more than 100 years ago is still used today.It is generally believed that lymphatic capillaries originate from venous endothelial cells and germinate into lymphatic sac and lymphatic network,and then lymphatic sac gradually evolves to form peripheral lymph nodes and lymphatic vessels.The morphological changes during embryonic development are great,the process is complex,and malformations often occur under the influence of a variety of factors,which makes it more challenging to understand the morphological characteristics of lymphatic development in different stages.With the development of digital medicine in China,the traditional experimental technology combined with computer is used to reconstruct the microtubule structure observed under the real human embryo microscope to establish a visual process of lymphatic development.It is of guiding significance for prenatal screening of lymphatic abnormalities and clinical diagnosis and treatment.Methods: Human embryo specimens donated to medical research were used to prepare paraffin-embedded serial sections.The morphological and structural characteristics and anastomosis of lymphatic sac and lymphatic vessels in different periods were observed by routine staining and immunohistochemical staining,the adjacent relationship with peripheral blood vessels was identified,and the development and evolution of lymphatic vessels was analyzed.The ultrahigh definition seamless continuous image database is established by using digital slice scanning system.One specimen each with Crown-Rump length of 9 mm,16 mm,25 mm,30 mm and 36 mm was selected for image analysis and three-dimensional modeling.The jugular lymphatic sac,thoracic and abdominal lymphatic vessels and surrounding vessels were reconstructed on the basis of vertebral body.The volume of jugular lymphatic sac and the position of each lymphatic sac and thoracic duct were measured and recorded,and the mosaic and anastomosis of blood vessels and lymphatic vessels were observed.The data of different Crown-Rump lengths were analyzed by statistical method.Results: In this study,22541 consecutive paraffin sections of 42 specimens(Gestation age 5-16 weeks,Crown-Rump length 7.0-170.0 mm)were collected and analyzed,of which15252 were digitized in ultrahigh definition.Some sections were identified by D2-40 immunohistochemical staining for lymphatic vessels and venules.The results showed that the diameter of lymphatic vessels was quite different,the lumen structure was irregular,and some of the lymphatic sac areas were ball-shaped.The results of section analysis and threedimensional reconstruction showed that the jugular lymphatic sac began to sprout in 9mm embryos.The volume ratios of left / right jugular lymphatic sac were 0.67 in 9 mm embryo,2.75 in 16 mm,2.33 in 25 mm,1.31 in 30 mm and 1.33 in 36 mm.The position of each lymphatic sac is relatively fixed,the jugular lymphatic sac is mostly located at the level of the first cervical vertebra to the sixth cervical vertebra,the Cisterna chyli is located between the 12 th thoracic vertebra and the first lumbar vertebra,and the retroperitoneal lymphatic plexus is located between the first lumbar vertebra and the fourth lumbar vertebra.Most of the lymphatic anastomosis between the lymphatic sac began to increase after 16 mm.According to the results,there were obvious thoracic ducts extending to the left jugular lymphatic sac in 25 mm embryos,between the fifth cervical vertebra and the first lumbar vertebrae.No obvious symmetrical thoracic ducts were found at this time.In 30 mm embryos,a large number of D2-40 immunohistochemical staining results showed that there were two longitudinal lymphatic trunks symmetrical along the left and right sides of the spine,where the posterior intercostal lymphatic vessels converged.According to the results,it is suggested that the development of vascular system tends to be stable in 25 mm embryos with about Crown-Rump length.Conclusions: 1.The sprouting of jugular lymphatic sac can be seen in 9mm embryos.The growth of jugular lymphatic sac in the left side of the embryo with different parietal-hip diameter is more dominant than that in the right side;2.In 30 mm embryos,two symmetrical longitudinal lymphatic trunks adjacent to the spine were observed by a large number of immunohistochemistry,and the posterior lymphatic vessels between the left and right intercostals converged here;3.The lumens of lymphatic vessels and lymphatic sac vary greatly and are irregular in shape,often forming lumps,which are easy to produce lymphatic aggregation and lead to the occurrence of lymphedema or lymphoma.