Regional lymph drainage routes from the diaphragm in the rat

Therapeutic delivery to the peritoneal lymphatics: Current understanding, potential treatment benefits and future prospects

The interest in approaches to deliver therapeutics to the lymphatic system has increased in recent years as the lymphatics have been discovered to play an important role in a range of disease states such as cancer metastases, inflammatory and metabolic disease, and acute and critical illness. Therapeutic delivery to lymph has the potential to enhance treatment of these conditions. Currently much of the existing data explores therapeutic delivery to the lymphatic vessels and nodes that drain peripheral tissues and the intestine. Relatively little focus has been given to understanding the anatomy, function and therapeutic delivery to the peritoneal lymphatics. Gaining a better understanding of peritoneal lymphatic structure and function would contribute to the understanding of disease processes involving these lymphatics and facilitate the development of delivery systems to target therapeutics to the peritoneal lymphatics. This review explores the basic anatomy and ultrastructure of the peritoneal lymphatics system, the lymphatic drainage pathways from the peritoneum, and therapeutic and delivery system characteristics (size, lipophilicity and surface properties) that favour lymph uptake and retention after intraperitoneal delivery. Finally, techniques that can be used to quantify uptake into peritoneal lymph are outlined, providing a platform for future studies.

The effects of pneumoperitoneum and controlled ventilation on peritoneal lymphatic bacterial clearance: experimental results in rats

OBJECTIVE

To evaluate the effect of pneumoperitoneum, both alone and in combination with controlled ventilation, on peritoneal lymphatic bacterial clearance using a rat bacterial peritonitis model.

METHOD

A total of 69 male Wistar rats were intraperitoneally inoculated with an Escherichia coli solution (10(9) colony-forming units (cfu)/mL) and divided into three groups of 23 animals each: A (control group), B (pneumoperitoneum under 5 mmHg of constant pressure), and C (endotracheal intubation, controlled ventilation, and pneumoperitoneum as in Group B). The animals were sacrificed after 30 min under these conditions, and blood, mediastinal ganglia, lungs, peritoneum, liver, and spleen cultures were performed.

RESULTS

Statistical analyses comparing the number of cfu/sample in each of the cultures showed that no differences existed between the three groups.

CONCLUSION

Based on our results, we concluded that pneumoperitoneum, either alone or in association with mechanical ventilation, did not modify the bacterial clearance through the diaphragmatic lymphatic system of the peritoneal cavity.

Salmonella typhimurium infection triggers dendritic cells and macrophages to adopt distinct migration patterns in vivo

The presence of an anti-bacterial T cell response and evidence of bacterial products in inflamed joints of reactive arthritis patients suggests an antigen transportation role in this disease for macrophages and dendritic cells. We have investigated the functional properties and in vivo migration of macrophages and DC after infection with Salmonella enterica serovar Typhimurium (S. typhimurium). BM-derived macrophages and DC displayed enhanced expression of costimulatory molecules (CD40 and CD86) and increased production of pro-inflammatory cytokines (TNF-alpha, IL-6 and IL-12p40) and nitric oxide after infection. Upon adoptive transfer into mice, infected DC migrated to lymphoid tissues and induced an anti-Salmonella T cell response, whereas infected macrophages did not. Infection of DC with S. typhimurium was associated with strong up-regulation of the chemokine receptor CCR7 and acquisition of responsiveness to chemokines acting through this receptor. Moreover, S. typhimurium-infected CCR7-deficient DC were unable to migrate to lymph nodes after adoptive transfer, although they did reach the spleen. Our data demonstrate distinct roles for macrophages and DC as antigen transporters after S. typhimurium infection and a dependence on CCR7 for migration of DC to lymph nodes after bacterial infection.

Ultrastructure and Estrogen Regulation of the Lymphatic Stomata of Ovarian Bursa in Mice

The ovarian bursa is a key player in maintaining adaptive ovarian microenvironment for ovulation. The lymphatic stomata are believed to be a major contributor to execute the function of the ovarian bursa, whereas little is known about their ultrastructure and regulation. Here, we examined the ultrastructure of lymphatic stomata in mouse ovarian bursa by scanning electron microscopy and transmission electron microscopy and investigated its regulation by estrogen. We found that the mesothelium on the visceral layer of mouse ovarian bursa was composed of the cuboidal and flattened cells. The lymphatic stomata with round and oval shapes were mainly among the cuboidal cells. The particles, cells, and fluid passed through the stomata and entered into the lymphatic drainage unit composed of connective tissue and lymphatic endothelial cells beneath the stomata. We also used trypan blue as a tracer and found that the absorption of trypan blue through the lymphatic stomata was increased by estrogen that enlarged the average opening area of lymphatic stomata. Furthermore, we detected that there existed estrogen receptors in the nuclei of the mesothelial cells on the visceral ovarian bursa by using immunoelectron microscopy. Taken together, these data suggest that both the absorption and opening area of the lymphatic stomata in mouse ovarian bursa may be influenced by estrogen.

The distribution and morphology of lymphatic vessels on the peritoneal surface of the adult human diaphragm, as revealed by an ink-absorption method

Application of india ink to the peritoneal and pleural surfaces of the adult human diaphragm allowed visualization of the distribution and morphology of the lymphatic vessels by light microscopy and scanning electron microscopy. The diaphragms examined had been fixed and stored in 10% formalin. Numerous lymphatic vessels were stained black with india ink, presenting reticular, radial-meshwork, ladder-like and lacy patterns. They were distributed throughout the entire sternocostal part. Analysis by light and scanning electron microscopy of the areas indicated by india ink revealed the presence of primary lymphatic vessels that formed lymphatic lacunae and stomatal openings to the peritoneal cavity. A layer of secondary collecting lymphatic vessels was located cranially with respect to the layer of primary lymphatic vessels. Thus, the peritoneum had at least two layers of lymphatic vessels. These lymphatic vessels were not tubular vessels but resembled flat cisternae, as has been suggested in the case of the mouse diaphragm. The pleura lacked lymphatic stomata and had no such double-layered lymphatic organization. This is the first report that showed distribution and morphology of the lymphatic vessels in the diaphragmatic peritoneum of the formalin-fixed, adult human diaphragm. The method and results in the present study may contribute to morphological analysis of the lymphatic system in the wall of the human body cavity.

Paclitaxel loaded poly(L-lactic acid) microspheres for the prevention of intraperitoneal carcinomatosis after a surgical repair and tumor cell spill

A controlled release delivery system for paclitaxel was developed using poly(L-lactic acid) to provide local delivery to the peritoneal cavity. Microspheres were made in 1-40 and 30-120 microm size ranges. In an in vitro release study, 30-120 microm microspheres loaded with 10, 20 and 30% paclitaxel exhibited a burst phase of release for 3 days followed by an apparently zero-order phase of release. At all loadings, 20-25% of the original load of paclitaxel was released after 30 days. The effect of microsphere size on retention in the peritoneal cavity was assessed. Control 1-40 microm microspheres were injected intraperitoneally in rats. The rats received either insufflation of the peritoneal cavity using 11 mmHg CO2 or no further treatment. After sacrifice, microspheres with diameters less than 24 microm were observed in the lymphatic system after being cleared from the peritoneal cavity through fenestrations in the diaphragm. Insufflation of the peritoneal cavity had no effect on the size of microspheres that were cleared. Efficacy studies were carried out using 30-120 microm microspheres that were of sufficient size to be retained in the peritoneal cavity. In a model of a tumor cell spill after a cecotomy repair, 100 mg of 30-120 microm microspheres containing 30% paclitaxel were effective in preventing growth of tumors in the peritoneal cavity at both 2 and 6 weeks post-surgery. No gross or histologically evident tumor growth was observed on any peritoneal surfaces or in the surgical wound site. Rats receiving control microspheres all showed tumor cell implantation and growth after 2 weeks.

The lymphatic vessels and the so-called "lymphatic stomata" of the diaphragm: a morphologic ultrastructural and three-dimensional study

We studied the absorbing peripheral lymphatic vessel with the light microscope, the transmission electron microscope, the scanning electron microscope, and three-dimensional models of the diaphragm of several rodents and insectivores under normal and experimental conditions (lymphatic stasis and dehydration). To clarify the delicate and complex mechanism that permits drainage of the abdominal cavity contents into the lymphatic circulatory system, we introduced Polystyrene latex spherules, China ink, and Trypan blue into the abdominal cavities. After anatomical comparisons of the superficial and deep networks of absorbing peripheral lymphatic vessels at the tendinous and muscular portions of the diaphragm and after classification of lymphatic vessels into absorbing and conducting functions, we examined the stomata, which, owing to morphologic and topographic findings, we defined as stable structures. Furthermore, we observed that the stomata and submesothelial connective channel are fundamental elements that facilitate the flow of the corpuscular and liquid contents of the peritoneal cavity to the submesothelial absorbing lymphatic vessel wall. Also, we underlined that the genesis of the connective channel depends on the secondary cytoplasm extensions of two distinct adjacent endothelial cells, which, to facilitate the flow of the absorbed abdominal contents, completely coat this channel. Additionally, our observations illustrate that the secondary cytoplasm extensions do not engage in continuous relationships with the basal lamina of the mesothelium and with the margins of the stoma, and, hence, the hypothesis of "lymphatic stomata" as an expression of the anchoring of the borders of the open interendothelial junctions to the orifice margins of the stoma cannot be confirmed. Moreover, we describe the presence and formation of intraendothelial channels in the lymphatic endothelial wall. We affirm that this morphological entity is a dynamic unit, because its numerical density varies according to different physiological and experimental conditions to degrees of hydrostatic and colloidal osmotic pressure and, perhaps, also to the particular characteristics of the substances that the connective channel liberates into the endothelial wall of the lymphatic vessel. In conclusion, we affirm that the absorbing peripheral lymphatic vessels of the diaphragm, by way of intraendothelial channel formations, membrane diffusion, and the vesicular path of the endothelial cells, constitute the fundamental draining elements for the corpuscular and liquid contents of the abdominal cavity.

A study of the three-dimensional organization of the human diaphragmatic lymphatic lacunae and lymphatic drainage units

The peritoneal stomata, lymphatic drainage units and subperitoneal terminal lymphatics, called lymphatic lacunae, form a specialized drainage system in the diaphragm, by which absorption of fluid in bulk, particles and cells is carried out in the peritoneal cavity. The aim of this study is to elucidate the three-dimensional organization and function of the subperitoneal lymphatic lacunae and lymphatic drainage units by using lymphatic casts in the scanning electron microscope (SEM), ODO (OsO4-DMSO-OsO4) freeze fracture, conventional SEM and the transmission electron microscope (TEM). The subperitoneal lymphatic lacuna is unique for its large size and its multiple morphology and can be recognized by its broad, flattened enlargement and the blind-ends of lymphatic vessels, from which extend numerous main lymphatic vessels and side branches. These lymphatic vessels communicate with each other and form a rich lymphatic plexus under the diaphragmatic peritoneum. Two layers of lymphatic networks, i.e. the subperitoneal plexus and the deeper plexus are found in the muscular portion. Only one layer is present in the tendinous portion of the human diaphragm. The lymphatic plexus is denser in the tendinous portion than that in the muscular portion. The lymphatic lacunae occur exclusively in the muscular portion of the human diaphragm. The lumina of lymphatic lacunae are separated from the peritoneal cavity by a barrier consisting of cuboidal mesothelial cells, endothelial cells of the lymphatic lacunae and intervening connective tissue forming a lymphatic drainage unit. All these three components of the lymphatic drainage unit abut upon each other, but are not linked by specialized junctions. The cuboidal mesothelial cells frequently extend valve-like cytoplasmic processes that bridge the subperitoneal channel and make give it a tortuous course. The fibrous layer of the connective tissue is arranged in fiber bundles and gives a three-dimensional network forming the floor of the peritoneal stomata and the roof of the lymphatic lacunae. Via the fibrous network, the cuboidal mesothelial cells and the endothelial cells of the lacunae come into close contact with each other and form short subperitoneal channels which connect the peritoneal cavity with the subperitoneal lymphatic lacunae. The lymphatic drainage units may regulate the material absorption of the peritoneal stomata from the peritoneal cavity. It is suggested that the peritoneal stomata together with the subperitoneal channels, lymphatic drainage units and lymphatic lacunae comprise an important diaphragmatic lymphatic drainage system which plays an important role in the absorption of materials from the peritoneal cavity.

A scanning electron microscopy and computer image processing morphometric study of the pharmacological regulation of patency of the peritoneal stomata

The experiment on mice was carried out by injecting intraperitoneally Chinese materia medica for treating hepatocirrhosis with ascites. Observations and a quantitative analysis were carried out on the pharmacological regulation of the peritoneal stomata by using a scanning electron microscope (SEM) and a computer image processing system attached to the SEM. There was a significant increase in both the diameter (P < 0.05) and distribution density (P < 0.01) of the peritoneal stomata in the red sage root and alismatis rhizome groups, whereas the effect of poria and poria peel was not significant compared with the control group (P > 0.05). Our findings confirm the effect of red sage root and alismatis rhizome on the regulation of the peritoneal stomata, which can enhance the absorption of ascitic fluid, taking into consideration the absorbent function of these stomata. They indicate that the patency of peritoneal stomata can vary in response to the effect of some Chinese materia. They also suggest that the ascites is drained mainly by means of enhancing the patency of the stomata and lymphatic absorption of the stomata during the process of treatment by traditional Chinese medicine.