Using Intravital Microscopy to Study the Role of MIF in Leukocyte Trafficking In Vivo

In vivo visualization of the microvasculature of the mouse cremaster muscle has been fruitful in the evaluation of the role of macrophage migration inhibitory factor in promotion of leukocyte trafficking. Here we explain how to undertake this preparation, including details on mouse anesthesia, securing intravenous access, and cremaster muscle exteriorization. We also provide information on the various microscopy modalities now available for imaging microvascular preparations of this nature.

Structural study of the cremaster muscle in patients with retractile testis

OBJECTIVE

To analyze the structure of the cremaster in patients with retractile testis (RT), comparing the distribution of nerves, elastic system and muscles with patients having cryptorchidism and inguinal hernia (IH).

PATIENTS AND METHODS

We studied 31 patients, 17 with RT (mean age=5.17years); 9 with IH (mean age=2.6) and 5 with cryptorchidism (mean age=3). A cremaster biopsy was performed and submitted to routine histological processing and studied using histochemistry and immunohistochemistry. The samples were photographed under an Olympus BX51 microscope. The images were processed with the Image J software and the cremaster muscle structures were quantified. Means were compared statistically using ANOVA and the unpaired t-test (p<0.05).

RESULTS

There were no differences (p=0.08) in diameter of muscle fiber between the groups. The muscle fiber density differed between patients with RT and IH (p=0.02): RT (mean=17.71%, SD=16.67), IH (mean=38.06%, SD=14) and cryptorchidism (mean=21.47%, SD=16.18). There was no difference (p=0.07) in the density of elastic fibers in the three groups. We observed a lower concentration of cremaster nerves of patients with RT compared with IH (p=0.0362): RT (mean=1.72%, SD=0.58), IH (mean=3.28% SD=0.94) and cryptorchidism (mean=2.52%, SD=0.53).

CONCLUSIONS

Retractile testis is not a normal variant, and presented a similar cremaster muscle structure as in patients with cryptorchidism.

LEVEL OF EVIDENCE

II; prospective comparative study.

Microcirculatory effect of topical vapocoolants

BACKGROUND

Vapocoolant sprays are commonly used to minimize pain following minor interventions such as venipuncture, shave biopsy or needle insertion. Although these sprays have been widely used in clinical practice, little is known about their effect on microcirculation or cutaneous blood flow.

OBJECTIVE

To evaluate the real-time effect of a topical vapocoolant using a well-established, rat cremaster muscle microcirculatory model, allowing direct measurement of changes in vessel diameter, capillary density and leukocyte behaviour.

METHODS

Fifty rats were divided into a control and four experimental groups: group 1: 4 s spray with vapocoolant at 18 cm distance; group 2: 10 s spray at 18 cm distance; group 3: 4 s spray at 8 cm distance; and group 4: 10 s spray at 8 cm distance. Vessel diameters, capillary density and leukocyte behaviour were monitored for 1 h thereafter. Muscle was harvested for immunohistochemistry analysis of proangiogenic markers (vascular endothelial growth factor and von Willebrand factor), leukocyte behaviour markers (E-selectin, vascular cell adhesion molecule, intercellular adhesion molecule), pimonidazole-hypoxia staining and ApopTag (Millipore, USA) staining for apoptosis. Gene expression for inflammatory markers (interleukin [IL]-1β, IL-2, IL-4, IL-6, IL-10, tumour necrosis factor-alpha and interferon-gamma) was evaluated using polymerase chain reaction and myeloperoxidase assay for inflammation was performed.

RESULTS

The use of refrigerant spray decreased vessel diameter and capillary density initially, although none of these decreases were statistically significant. Polymerase chain reaction showed no significant changes. The myeloperoxidase assay showed statistically significant increase in myeloperoxidase activity in groups 2, 3 and 4. Immunohistochemistry was negative for angiogenic and proinflammatory markers.

CONCLUSIONS

The lack of statistically significant changes in vessel diameter and inflammatory markers corroborated the safety on microcirculation.

Intravital Microscopy in the Cremaster Muscle Microcirculation for Endothelial Dysfunction Studies

The intravital microscopy in the mouse cremaster muscle microcirculation is a method widely used to visualize in vivo blood cells interacting with the endothelium and within the vessels. Therefore, it is a suitable technique to study leukocyte-endothelial cell interactions along every stage of the canonical leukocyte recruitment cascade: rolling, adhesion, intravascular crawling, and migration both in postcapillary venules and arterioles of the mouse cremasteric microcirculation. This technique also enables to assess vessel functionality, since hemodynamic parameters such as shear stress, flow rate, and vasodilatation/vasoconstriction, among other vascular events, can be additionally determined. Furthermore, response to multiple drugs and mechanisms underlying blood cells interactions within the vascular system can be studied in a real scenario. This chapter describes a protocol for intravital microscopy in the mouse cremaster muscle microcirculation.

Molecular signals governing cremaster muscle development: clues for cryptorchidism

BACKGROUND/AIM

Cryptorchidism affects 2-4% of newborn boys. Testicular descent requires the gubernaculum to differentiate into cremaster muscle (CM) during androgen-mediated inguino-scrotal descent, but the cellular mechanisms regulating this remodeling remain elusive. β-Catenin, a marker of canonical Wnt signaling, promotes myogenic genes and cellular adhesion. We aimed to determine if androgen receptor (AR) blockade altered β-catenin and its downstream myogenic proteins within the CM.

METHOD

Gubernacula from male rats (n=12) and rats treated with anti-androgen, flutamide (n=12) at E19, D0, D2 were processed for immunohistochemistry. Antibodies against β-catenin, embryonic myosin, and myogenin were visualized by confocal microscopy.

RESULTS

At E19, β-catenin immuno-reactivity (IR) localized to the CM membrane. By D2, cytoplasmic β-catenin-IR was noted with overall β-catenin-IR decreasing. Myogenic proteins resided primarily in cells containing β-catenin on their plasma membrane. Embryonic myosin-IR was high at E19 and then decreased by D2, while myogenin-IR increased. AR blockade increased cytoplasmic β-catenin at D2 and reduced levels of both myogenic proteins.

CONCLUSION

Myogenic proteins are present in CM cells containing β-catenin. AR blockade did not alter cellular adhesion via β-catenin. In contrast, blocking AR prevented β-catenin entering the nucleus and impaired CM myogenesis. Mutations in this pathway may result in idiopathic cryptorchidism.

Intravital microscopic evaluation of cremasteric microcirculation in experimental testicular torsion

AIM

Although absent cremasteric reflex is a significant clinical finding for testicular torsion (TT), there is limited information about microcirculation of the cremasteric muscle (CM) after TT. This experimental study was performed to evaluate CM microcirculation by intravital microscopy after TT.

MATERIALS AND METHODS

Twelve Wistar rats were allocated into two equal groups: control (CG) and torsion (TG). After anesthetization of the CG rats, the CM flap was dissected through a left ventral inguinal incision with its vascular pedicle. In TG rats, TT was performed by rotating left testicles 720(°) in clockwise direction for 1 h. Then, the CM flap was dissected as in CG, and was placed under an intravital microscope. Vessel diameters, functional capillary perfusion and leukocyte activation in post-capillary venules were measured and evaluated statistically.

RESULTS

There was a significant decrease in vessel diameter in TG compared to CG (p < 0.05). The median of perfused capillaries in CG and TG was 13 (11.75-14.30) and 5.5 (4.75-7.25), respectively (p < 0.05). Number of granulocytes (rolling, sticking, transmigrated) was greater in TG than CG (p < 0.05).

CONCLUSION

Intravital microscopic evaluation of CM after TT showed decrease in vessel diameter and number of perfused capillaries, and increase in granulocyte activation. Clinical, electrophysiological alterations in CM after TT can be explained by deterioration of microcirculation of CM.

Infertility in rats subjected to genitofemoral nerve section is not associated with testicular damage

This work was aimed at assessing the relationship between testicular ascent and infertility induced by genitofemoral nerve (GFN) section in rats. Eighteen male rats were assigned to three experimental groups as follows: (i) Group SGFN was subjected to surgical section of genitofemoral nerve; (ii) Group Sham; (iii) Control group. The GFN was cut at puberty (28D), and the contralateral testis removed at 90D, with fertility tests at 120D. At 150D, maturity index, epithelial area and histopathological index of seminiferous tubules of all rats were determined and statistically compared between superior and inferior testicle poles, and between groups. There were no differences in testicular parameters, sperm morphology or sperm concentrations (P > 0.05). Section of NGF interfered with fertility (58.3 ± 15.4 in SGFN versus 83.3 ± 10.5 in Sham) and litter size (6.2 ± 1.1 in SGFN versus 10.7 ± 1.4 in Sham). Cremaster of SGFN group showed early neuropathy. The GFN section induced partial testicular ascent and diminished fertility without damage on testicular morphology or spermatic parameters, because, cremaster could affect the contractibility and ejaculation mechanisms in which it participates. The study of the damage on cremaster induced by an injury on GFN could have an overview of the mechanisms inherent in the testicular ascent induced by this iatrogenic alteration and their potential risks on fertility.