title: The discovery of the synovial lymphatic stomata and lymphatic reabsorption in knee effusion.
abstract: To illustrate the mechanism of lymphatic reabsorption in knee joint effusion. The current investigation employed transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques to reveal the ultrastructure of the knee synovial membrane in New Zealand rabbits and human. Ultrastructural changes of the synovial lymphatic stomata were observed by using trypan blue absorption and sodium hydroxide (NaOH) digestion methods, and the animal models of synovitis. New Zealand rabbits and human synovial membranes were composed of two types of synovial cells: type A and type B. No lymphatic stomata were found among type A synovial cells, whereas lymphatic stomata with the diameters ranging 0.74-3.26 µm were found in type B synovial cells, and some stomata were closed. After the NaOH digestion, a number of sieve pores, similar to lymphatic stomata in size and shape, were observed in the dense fibrous connective tissue underneath the type B synovial cells. After injecting trypan blue into the rabbit knee joint cavity, absorption of trypan blue through the lymphatic stomata was observed, suggesting the absorption function of the synovial lymphatic stomata. In the rabbit knee joint synovitis models, the synovial lymphatic stomata diameter enlarged. Some macrophages migrated from the lymphatic stomata, indicating that the synovial lymphatic stomata were involved in the joint effusion absorption and inflammatory response. Our study is the first to report the existence of synovial lymphatic stomata in the New Zealand rabbits and human knee joints. Lymphatic stomata may have an important role in the reabsorption of joint effusion.
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Zepeng
authors: Z
authors: Ping
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Tingting
authors: T
authors: Jiang
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Chong
authors: C
authors: Wang
authors: Department of Orthopedics, Taizhou Hospital of Zhejiang Province, Linhai, 317000, China.
authors: Zhongyi
authors: Z
authors: Chen
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Zhongliang
authors: Z
authors: Chen
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Jiaxiong
authors: J
authors: Wang
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Li
authors: L
authors: Wang
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Beibei
authors: B
authors: Wang
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Dandan
authors: D
authors: Xu
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Changming
authors: C
authors: Liu
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Zhongjie
authors: Z
authors: Li
authors: Department of Histology and Embryology, Institute of Cell Biology, Zhejiang University, Hangzhou, 310058, China.
authors: Ji-Cheng
authors: JC
authors: Li
mesh_terms: D000818:Animals; D001202:Ascitic Fluid / Q000378:metabolism*; D001692:Biological Transport; D006801:Humans; D007719:Knee Joint / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D054048:Peritoneal Stomata / Q000648:ultrastructure*; D011817:Rabbits; D013583:Synovial Membrane / Q000648:ultrastructure*; D013585:Synovitis / Q000473:pathology*
keywords: joint cavity; lymphatic reabsorption; lymphatic stomata; synovial cells; ultrastructure