Dense distribution of macrophages in flexor aspects of the hand and foot of mid-term human fetuses

In the developing human musculoskeletal system, cell death with macrophage accumulation occurs in the thigh muscle and interdigital area. To comprehensively clarify the distribution of macrophages, we immunohistochemically examined 16 pairs of upper and lower extremities without the hip joint (left and right sides) obtained from 8 human fetuses at approximately 10-15 weeks of gestation. Rather than in muscles, CD68-positive macrophages were densely distributed in loose connective tissues of the flexor aspects of the extremities, especially in the wrist, hand and foot. In contrast, no or fewer macrophages were evident in the shoulder and the extensor aspects of the extremities. The macrophages were not concentrated at the enthesis of the tendon and ligament, but tended to be arranged along other connective tissue fibers. Deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling revealed apoptosis in the hand lumbricalis muscles, but not in the area of macrophage accumulation. Likewise, podoplanin-positive lymphatic vessels were not localized to areas of macrophage accumulation. Re-organization of the connective tissue along and around the flexor tendons of the hand and foot, such as development of the bursa or tendon sheath at 10-15 weeks, might require the phagocytotic function of macrophages, although details of the mechanism remain unknown.

Is lymphatic status related to regression of inflammation in Crohn's disease?

AIM: To investigate the status of the lymphatic vessels in the small bowel affected by Crohn’s disease (CD) at the moment of surgery.

METHODS: During the period January 2011-June 2011, 25 consecutive patients affected by CD were operated on in our Institution. During surgery, Patent Blue V was injected subserosally and the way it spread along the subserosa of the intestinal wall, through the mesenterial layers towards the main lymphatic collectors and eventually to the lymph nodes was observed and recorded. Since some patients had been undergone strictureplasty at previous surgery, we also examined the status of intestinal lymph vessels after previous strictureplasties. The same procedure was performed in a control group of 5 patients affected by colorectal cancer. Length of lesions, caliber, maximal thickness of the diseased intestinal wall, thickness of the wall at injection site and thickness of the mesentery were evaluated at surgery.

RESULTS: We observed three features after the injection of Patent Blue V in the intestinal loops: (1) Macroscopically healthy terminal ileum of patients with CD or colon cancer showed thin lymphatic vessels linearly directed toward the mesentery; (2) In mild lesions in which the intestinal wall did not reach 8 mm of thickness, we observed short, wide and tortuous lymphatic vessels directed longitudinally along the intestinal axis toward disease-free areas and then transversally toward the mesentery; and (3) Injection in the severely affected lesions, that had a thickness of the intestinal wall over 10 mm, did not show any feature of lymphatic vessels at least on the subserosal surface. There was a correlation between the thickness of the parietal wall and the severity of the lymphatic alterations. Normal lymphatic vessels were observed at previous strictureplasties in the presence of complete regression of the inflammation.

CONCLUSION: Injection of Patent Blue V in the intestinal wall could help distinguish healthy tracts of the small bowel from those macroscopically borderline.

Lymphangiogenesis: A new player in cancer progression

Lymph node metastasis is the hallmark of colon cancer progression, and is considered one of the most important prognostic factors. Recently, there has been growing evidence that tumor lymphangiogenesis (formation of new lymphatic vessels) plays an important role in this process. Here, we review the latest findings of the role of lymphangiogenesis in colorectal cancer progression, and discuss its clinical application as a biomarker and target for new therapy. Understanding the molecular pathways that regulate lymphangiogenesis is mandatory to pave the way for the development of new therapies for cancer. In the future, tailored treatments consisting of combinations of chemotherapy, other targeted therapies, and anti-lymphangiogenesis agents will hopefully improve patient outcomes. This progression to the clinic must be guided by new avenues of research, such as the identification of biomarkers that predict response to treatment.

Perimuscular connective tissue contains more and larger lymphatic vessels than the shallower layers in human gallbladders

AIM: To clarify whether perimuscular connective tissue contains more lymphatic vessels than the shallower layers in human gallbladders.

METHODS: Lymphatic vessels were stained immunohistochemically with monoclonal antibody D2-40, which is a specific marker of lymphatic endothelium, in representative sections of 12 normal human gallbladders obtained at the time of resection for colorectal carcinoma liver metastases. In individual gallbladder specimens, nine high-power (× 200) fields with the highest lymphatic vessel density (LVD), termed “hot spots”, were identified for each layer (mucosa, muscle layer, and perimuscular connective tissue). In individual hot spots, the LVD and relative lymphatic vessel area (LVA) were measured microscopically using a computer-aided image analysis system. The mean LVD and LVA values for the nine hot spots in each layer were used for statistical analyses.

RESULTS: In the mucosa, muscle layer, and perimuscular connective tissue, the LVD was 16.1 ± 9.2, 35.4 ± 15.7, and 65.5 ± 12.2, respectively, and the LVA was 0.4 ± 0.4, 2.1 ± 1.1, and 9.4 ± 2.6, respectively. Thus, both the LVD and LVA differed significantly (P < 0.001 and P < 0.001, respectively; Kruskal-Wallis test) among the individual layers of the wall of the gallbladder, with the highest LVD and LVA values in the perimuscular connective tissue. Most (98 of 108) of the hot spots within the perimuscular connective tissue were located within 500 μm of the lower border of the muscle layer.

CONCLUSION: The perimuscular connective tissue contains more and larger lymphatic vessels than the shallower layers in the human gallbladder. This observation partly explains why the incidence of lymph node metastasis is high in T2 (tumor invading the perimuscular connective tissue) or more advanced gallbladder carcinoma.