Carotid Catheterization and Automated Blood Sampling Induce Systemic IL-6 Secretion and Local Tissue Damage and Inflammation in the Heart, Kidneys, Liver and Salivary Glands in NMRI Mice

Abstract

Automated blood sampling through a vascular catheter is a frequently utilized technique in laboratory mice. The potential immunological and physiological implications associated with this technique have, however, not been investigated in detail. The present study compared plasma levels of the cytokines IL-1β, IL-2, IL-6, IL-10, IL-17A, GM-CSF, IFN-γ and TNF-α in male NMRI mice that had been subjected to carotid artery catheterization and subsequent automated blood sampling with age-matched control mice. Body weight and histopathological changes in the surgical area, including the salivary glands, the heart, brain, spleen, liver, kidneys and lungs were compared. Catheterized mice had higher levels of IL-6 than did control mice, but other cytokine levels did not differ between the groups. No significant difference in body weight was found. The histology revealed inflammatory and regenerative (healing) changes at surgical sites of all catheterized mice, with mild inflammatory changes extending into the salivary glands. Several catheterized mice had multifocal degenerative to necrotic changes with inflammation in the heart, kidneys and livers, suggesting that thrombi had detached from the catheter tip and embolized to distant sites. Thus, catheterization and subsequent automated blood sampling may have physiological impact. Possible confounding effects of visceral damage should be assessed and considered, when using catheterized mouse models.

Fig 1. The surgical area of the ventral neck in one control mouse and one catheterized mouse.

Normal histology (left image) shows a midline area of connective and adipose tissue and the bilateral submandibulary salivary glands. In the right image, the surgical area of one catheterized mouse is affected by increased clear space (edema) and infiltration of inflammatory cells. Fibroblast proliferations suggest regenerative processes. Hematoxylin and eosin. Bars = 500 μm.

Fig 2. Surgical area at the ventral midline of catheterized mice.

In the top left image, the submandibulary salivary gland is multifocally degenerated to necrotic with loss of zymogen granules in tubules and acini of this male mouse. There is increased clear space (edema) in the connective and adipose tissue with infiltration of inflammatory cells (inflammation) and proliferation of fibroblasts (regeneration). The wall of a major artery is infiltrated with inflammatory cells (arteritis) with thrombus formation, protruding to the arterial lumen. The areas highlighted by the black and blue boxes are shown in higher magnification in the bottom left and top right images, respectively. Another catheterized mouse (bottom right image) was found with similar lesions; the submandibulary salivary gland, adjacent to a major artery, was found compressed and necrotic with hemorrhage and neovascularization (angiogenesis) in the necrotic area. Hematoxylin and eosin. Bars = 500 μm in top left image, 200 μm in bottom left image and 100 μm in both right images.

Fig 3. Kidney from one control mouse and one catheterized mouse.

The top left image shows normal kidney histology in one control mouse. In the top right image, focal tubular degeneration with cyst formation is seen, shown in higher magnifications in the bottom left and right images, as indicated in the black and blue boxes, respectively. The epithelium is plump and hyperbasophilic, suggesting regeneration. Note the apoptotic epithelial cell in one dilated tubule (bottom right image). Bars = 200 μm in the top images, 100 μm in the bottom left image and 33 μm in bottom right image.

Fig 4. Liver from one control mouse and one catheterized mouse.

The top left image shows normal liver histology in one control mouse. In the top right image, multifocal granulocyte accumulations in association with hepatocyte necrosis (microgranulomas) are seen, shown in higher magnifications in the bottom images (highlighted by thick arrows). The area highlighted in the black box is shown in higher magnification in the bottom left image. Note the apoptotic hepatocyte (thin arrow). The bottom right image shows another microgranuloma in the same mouse (not shown in the top right image). Note the single cell necrosis in the bottom right corner (arrow head). Bars = 200 μm in the top images, 100 μm in the bottom left image, and 50 μm in the bottom right image.