Immunohistochemical Identification of Lymphatic Vessels in the Periodontium of Equine Cheek Teeth

Abstract

Immunohistochemical detection of lymphatic capillaries was performed in the periodontium of maxillary and mandibular cheek teeth from 6 horses (aged 3-23 years). Tissue sections of the periodontium were taken at 4 different horizontal levels along the long axis of the tooth. The specimens were processed for immunoreaction with anti-Prox1, in order to distinguish lymphatic endothelium from blood vascular endothelium. Lymphatic vessels were detected in all periodontal tissues except for the dental cementum. Lymphatic capillaries were most densely distributed in the gingiva compared to other tissues of the periodontium. Lymphatic capillaries were found most consistently in samples taken from the gingival and subgingival regions in all horses examined. Within these levels, the gingiva as well as the spongiosa of the maxillary and mandibular bone had the greatest incidence of lymphatic vessels. Considering the distinct distribution of the lymphatic capillaries in the periodontium of the maxillary and mandibular cheek teeth, two complementary lymphatic drainage pathways are proposed: (1) superficial lymph drainage via the gingiva, emptying into the mandibular lymph nodes; (2) deep lymph drainage via the mandibular and maxillary spongiosa, emptying into the mandibular and retropharyngeal lymph nodes, respectively.

Presumed primary ocular lymphangiosarcoma with metastasis in a miniature horse

“…To the authors’ knowledge, this is the first reported case in which PROX‐1 was used to aid in the diagnosis of a lymphangiosarcoma in a horse. PROX‐1 expression has also previously been reported in one case of feline lymphangiosarcoma . The neoplasm origin in the present case was confirmed by the positive detection of this antigen, and the authors suggest that PROX‐1 staining should be considered when there is need for further differentiation of an angiosarcoma in a horse.…”

Lymphatic Vessel Network Structure and Physiology

“…Lyve1-positive vessels have been detected in the lamina propria in gingiva and in the free oral mucosa in mice (835, 1096). Prox1 expression has also been identified in equine gingival lymphatics (1021). Inflammation of the gingiva leads to formation of crevicular fluid and accumulation of CD45+ cells.…”

Lymphatic function and responses in periodontal disease

“…Whether there is lymphatic drainage from the periodontal ligament is uncertain since conflicting data have been published. Lymphatic vessels have not been detected in the rat apical periodontal ligament [37] or in human apical lesions [38], in contrast to findings in horse periodontal ligament lymphatic vessels where lymphatic vessels have been shown [39]. If fluid from the periodontal ligament is drained from lymphatic vessels within the tissue or if fluid is transported through the interstitium into adjacent tissue, supplied with lymphatic vessels, remains to be investigated.…”

“…3), whereas VEGF-D is only found in some few immune cells in the connective tissue [42]. The lymphatic marker Prox1 has been shown in gingival lymphatic vessels [39] and activity in the homeobox gene Prox1 is necessary and sufficient to maintain a lymphatic endothelial fate [43]. Lymphatic endothelial cells are one of the few differentiated cell types that require a constant expression of a particular 'instructor' gene (in this case Prox1) to maintain their phenotype [44].…”