Morphologic characteristics of initial lymphatics of the healthy and diseased human gingiva

Critical review: Cardiac telocytes vs cardiac lymphatic endothelial cells

The study of cardiac interstitial Cajal-like cells (ICLCs) began in 2005 and continued until 2010, when these cells were renamed as telocytes (TCs). Since then, numerous papers on cardiac ICLCs and TCs have been published. However, in the initial descriptions upon which further research was based, lymphatic endothelial cells (LECs) and initial lymphatics were not considered. No specific antibodies for LECs (such as podoplanin or LYVE-1) were used in cardiac TC studies, although ultrastructurally, LECs and TCs have similar morphological traits, including the lack of a basal lamina. When tissues are longitudinally cut, migrating LECs involved in adult lymphangiogenesis have an ICLC or TC morphology, both in light and transmission electron microscopy. In this paper, we present evidence that at least some cardiac TCs are actually LECs. Therefore, a clear-cut distinction should be made between TCs and LECs, at both the molecular and the ultrastructural levels, in order to avoid obtaining invalid data.

Cilostazol on the expression of ICAM-1, VCAM-1 and inflammatory factors in plasma in patients with thromboangiitis obliterans

The effects of cilostazol on the expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and inflammatory factors in plasma in patients with thromboangiitis obliterans (TAO) were studied. Plasma viscosity, fibrinogen, total cholesterol (TC) and triglyceride (TG) were detected for the healthy control, TAO and cilostazol groups, respectively. Results showed that compared with those in the control group, the plasma viscosity, fibrinogen, TC and TG levels in TAO group were significantly increased. By contrast, compared with those in TAO group, the plasma viscosity, fibrinogen, TC and TG levels in the cilostazol group were significantly decreased. ELISA results revealed that ICAM-1 and VCAM-1 expression levels in TAO group were obviously increased compared with those in control group. ICAM-1 and VCAM-1 expression levels in cilostazol group were obviously decreased compared with those in TAO group. According to RT-PCR, the mRNA expression levels of IL-1β, IL-6 and TNF-α in TAO group were significantly higher than those in control group, while the levels in cilostazol group were significantly decreased compared with those in TAO group. In addition, RT-PCR and western blotting proved that expression of both mRNA and protein of ICAM-1 and VCAM-1 in TAO group was significantly increased and obviously decreased after administration of cilostazol. The results of analysis of variance showed that the differences of ICAM-1 and VCAM-1 expression was statistically significant among the control, TAO and cilostazol groups (p<0.01). Cilostazol can significantly reduce the TAO-induced abnormal increase in ICAM-1, VCAM-1 and inflammatory factor expression in plasma in patients. It was proven that cilostazol has a good anti-TAO effect.

Solitary Superficial Microcystic Lymphatic Malformation (Lymphangioma Circumscriptum) of the Gingiva

BACKGROUND

Lymphatic malformations are uncommon, hamartomatous, developmental aberrations of the lymphatic system. The case presented in this report is a rare solitary gingival involvement of a microcystic-type lymphatic malformation.

METHODS

The lesion presented clinically as a small vesicular swelling of a buccal interdental papilla in a 16-year-old girl. Involved tissues were excised and submitted for routine histologic examination. The expression of the endothelial marker CD34 was investigated using immunohistochemical staining.

RESULTS

A physical examination failed to reveal similar or other abnormalities elsewhere in the body of the patient, including the oral cavity. Histopathologic analysis of the specimen demonstrated the presence of subepithelial, thin-walled, distended vascular cavities forming confluent vesicles containing lymph. The dilated lymphatic formations were lined by flattened CD34-negative endothelial cells. These features were consistent with a microcystic gingival lymphatic malformation. To the best of our knowledge, only two additional reports of this malformation have been published to date, but both presented with bilateral gingival involvement.

CONCLUSION

Even though lymphatic malformations are encountered very infrequently on gingiva, they should be considered in the differential diagnosis of related conditions with a vesicular clinical appearance.

A model for mechanics of primary lymphatic valves

Recent experimental evidence indicates that lymphatics have two valve systems, a set of primary valves in the wall of the endothelial cells of initial lymphatics and a secondary valve system in the lumen of the lymphatics. While the intralymphatic secondary valves are well described, no analysis of the primary valves is available. We propose a model for primary lymphatics valves at the junctions between lymphatic endothelial cells. The model consists of two overlapping endothelial extensions at a cell junction in the initial lymphatics. One cell extension is firmly attached to the adjacent connective tissue while the other cell extension is not attached to the interstitial collagen. It is free to bend into the lumen of the lymphatic when the lymphatic pressure falls below the adjacent interstitial fluid pressure. Thereby the cell junction opens a gap permitting entry of interstitial fluid into the lymphatic lumen. When the lymphatic fluid pressure rises above the adjacent interstitial fluid pressure, the endothelial extensions contact each other and the junction is closed preventing fluid reflow into the interstitial space. The model illustrates the mechanics of valve action and provides the first time a rational analysis of the mechanisms underlying fluid collection in the initial lymphatics and lymph transport in the microcirculation.

Lymphatic networks in the periodontal tissue and dental pulp as revealed by histochemical study

The structural organization and fine distribution of the lymphatic networks in the periodontal tissues (gingiva, periodontal membrane, and alveolar process) and dental pulp of animals and humans were reviewed with special reference to histochemical examination by light and electron microscopy. The distinction between lymphatics and blood vessels was made on cryostat sections of undecalcified and calcified teeth treated with EDTA solution and whole mount preparations of periodontal membranes using 5'-nucleotidase (5'-Nase)-alkaline phosphatase (ALPase) double staining. This staining procedure allowed lymphatic vessels in the periodontal tissue and dental pulp to be differentiated from blood vessels. The specificity and localization of the enzyme reactions were confirmed by comparative histochemical studies of the same specimen with light microscopy and scanning or transmission electron microscopy. Well-developed 5'-Nase-positive lymphatic networks were observed on the tissue sections and whole mount preparations of the gingiva, periodontium, and dental pulp. More lymphatic vessels were seen in the root area of the periodontium than in the cervical area. In the dental pulp, lymphatic vessels were more numerous in the central part than in the peripheral odontoblastic layer. These distributions of the lymphatic capillary networks are discussed in relation to their ability to supply lymph to the teeth.

Lymphatic vessels in the oral cavity: different structures for the same function

A study using a light and transmission electron microscope was performed on some structural characteristics of the lymphatic capillaries in different regions of the human oral cavity. The lymphatic capillaries of dental pulp, masticatory mucosa (gingiva and peri-implant mucosa) and lining mucosa (cheek) were examined. Our attention was focused on the morphologic characteristics of the endothelial wall in the lymphatic capillaries. In particular, the connections between endothelial cells were investigated. In the lymphatic capillaries of the dental pulp, the endothelial wall was always very complex. It frequently presented protrusions of the endothelial cells that overlapped and formed intercellular channels. These channels were thus contained by the vessel endothelial wall with their extremities opening out towards the surrounding interstitium and the vessel lumen. The endothelial wall of the lymphatic capillaries of the cheek was very smooth and thin without complex intercellular junctions. The endothelial cells were joined by end-to-end junctions and open junctions were frequently observed. Intercellular channels were also found in the endothelial wall of lymphatic capillaries of the gingiva and the peri-implant mucosa. The presence of numerous clefts represented by the open junctions in the lymphatics of the cheek and the existence of complex intercellular adhesions with the formation of intercellular channels in the endothelial wall of the lymphatic capillaries of the dental pulp and gingiva induce us to believe that these may play a role in the various mechanisms used by lymphatic capillaries to absorb interstitial fluids. These mechanisms are based on the different morpho-functional characteristics of the surrounding tissue.

The characteristic cellular organization and CEACAM1 expression in the junctional epithelium of rats and mice are genetically programmed and not influenced by the bacterial microflora

BACKGROUND

The epithelial cell adhesion molecule CEACAM1 exhibits an interesting dynamic expression during tooth development. It is first expressed in the reduced enamel epithelium, its expression then increases in the orally faced reduced epithelium and the overlying oral epithelium that then fuse to give rise to the junctional epithelium. The expression of CEACAM1 remains at high levels in the junctional epithelium, in contrast to the surrounding oral sulcular epithelium which shows much lower expression levels. We investigated if the high expression levels of CEACAM1 and the loosely organized cells characteristic of the junctional epithelium are genetically programmed or result from bacterial infiltration.

METHODS

Oral tissues from germ-free rats and mice and animals with conventional bacterial flora were analyzed by transmission electron microscopy and immunohistochemical staining for CEACAM1.

RESULTS

The junctional epithelium of both germ-free and conventional animals was identical with respect to both CEACAM1 expression and morphology. Also the presence of leukocytes was the same in both types of animals.

CONCLUSIONS

The results indicate that the characteristic morphology and the high expression levels of CEACAM1 in the junctional epithelium are genetically programmed and not a result of bacterial infiltration. This suggests that CEACAM1 has an important role for the structural integrity of the junctional epithelium. This conclusion was supported by the observation that the junctional epithelium does not express any E-cadherin, which is another abundant epithelial cell adhesion molecule.