Effects of strain and age on ear wound healing and regeneration in mice

Round holes in the ears of MRL mice tend to close with characteristics of regeneration believed to be absent in other mouse strains (e.g., C57BL/6). We evaluated the kinetics and the histopathology of ear wound closure in young (8 weeks old) C57BL/6 and BALB/c mice. We also used middle-aged (40 weeks old) C57BL/6 mice to evaluate the influence of aging on this process. A circular through-and-through hole was made in the ear, photographs were taken at different times after injury and wound area was measured with digital analysis software. The percentages of closed area measured on day 100 were: 23.57 ± 8.66 percent for young BALB/c mice, 56.47 ± 7.39 percent for young C57BL/6 mice, and 75.31 ± 23.65 percent for middle-aged C57BL/6 mice. Mice were sacrificed on days 1, 3, 5, 25, 44, and 100 for histological evaluation with hematoxylin and eosin, Gomori’s trichrome, periodic acid-Schiff, or picrosirius red staining. In young mice of both strains, healing included re-epithelialization, chondrogenesis, myogenesis, and collagen deposition. Young C57BL/6 and BALB/c mice differed in the organization of collagen fibers visualized using picrosirius-polarization. Sebaceous glands and hair follicles regenerated and chondrogenesis was greater in young C57BL/6 mice. In middle-aged C57BL/6 mice all aspects of regeneration were depressed. The characteristics of regeneration were present during ear wound healing in both young BALB/c and young C57BL/6 mice although they differed in intensity and pattern. Greater ear wound closure in middle-aged C57BL/6 mice was not correlated with regeneration.

Effects of strain and age on ear wound healing and regeneration in mice.

Round holes in the ears of MRL mice tend to close with characteristics of regeneration believed to be absent in other mouse strains (e.g., C57BL/6). We evaluated the kinetics and the histopathology of ear wound closure in young (8 weeks old) C57BL/6 and BALB/c mice. We also used middle-aged (40 weeks old) C57BL/6 mice to evaluate the influence of aging on this process. A circular through-and-through hole was made in the ear, photographs were taken at different times after injury and wound area was measured with digital analysis software. The percentages of closed area measured on day 100 were: 23.57 +/- 8.66% for young BALB/c mice, 56.47 +/- 7.39% for young C57BL/6 mice, and 75.31 +/- 23.65% for middle-aged C57BL/6 mice. Mice were sacrificed on days 1, 3, 5, 25, 44, and 100 for histological evaluation with hematoxylin and eosin, Gomori's trichrome, periodic acid-Schiff, or picrosirius red staining. In young mice of both strains, healing included re-epithelialization, chondrogenesis, myogenesis, and collagen deposition. Young C57BL/6 and BALB/c mice differed in the organization of collagen fibers visualized using picrosirius-polarization. Sebaceous glands and hair follicles regenerated and chondrogenesis was greater in young C57BL/6 mice. In middle-aged C57BL/6 mice all aspects of regeneration were depressed. The characteristics of regeneration were present during ear wound healing in both young BALB/c and young C57BL/6 mice although they differed in intensity and pattern. Greater ear wound closure in middle-aged C57BL/6 mice was not correlated with regeneration.

Digestion, absorption and tissue distribution of ovalbumin and palmitoyl-ovalbumin: impact on immune responses triggered by orally administered antigens.

Previous work in this laboratory has demonstrated that ovalbumin coupled to palmitoyl residues (palmitoyl-Ova) does not induce oral tolerance. The present study sought to determine whether this coupling affects digestion, absorption and transfer of antigen. Ova and palmitoyl-Ova were shown to be digested differently in vitro by proteolytic enzymes and presented different tissue distribution kinetics after being labelled with (99m)technetium and orally administered to animals. Palmitoyl-Ova remained longer in the stomach, while native Ova was quickly transferred to the gut and other organs. After 3 h, higher levels of palmitoyl-Ova were found in the blood, Peyer's patches, mesenteric lymph nodes, liver and, especially, the spleen, which appears to be essential for immunization with palmitoyl-Ova. In fact, splenectomized mice treated orally with palmitoyl-Ova became tolerant, while tolerance to Ova was not affected. Thus, palmitoyl coupling was demonstrated to affect antigen digestion, absorption and transport. This is the first time that the spleen has been shown to be required for oral immunization with palmitoyl-Ova.

Covalent coupling of palmitate to ovalbumin inhibits and blocks the induction of oral tolerance.

Oral tolerance is a phenomenon that may occur in animals exposed to soluble antigens for the first time by the oral route. In the present study, we show that oral tolerance against ovalbumin (Ova) can be obtained after intragastric administration of the antigen in the presence of free residues of palmitate. On the other hand, oral tolerance induction is blocked when the residues of palmitate are covalently bound to the antigen (Ova-palmitate conjugates). We have also noticed that oral administration of Ova-palmitate conjugates can boost and/or prime experimental animals for Ova-specific cellular and humoral systemic immune responses. Oral treatment with the conjugates also induces the production of local secretory immunoglobulin A (IgA) as measured in intestinal washes. Furthermore, Ova-palmitate given orally can inhibit oral tolerance induction by naïve Ova.

Selective induction of interleukin-1 receptor antagonist and interleukin-8 in human monocytes by normal polyspecific IgG (intravenous immunoglobulin).

We have investigated the effects of intravenous immunoglobulin (IVIg), a therapeutic preparation of normal human polyspecific IgG, on the synthesis and release of cytokines by peripheral blood monocytes. IVIg was found to selectively induce gene transcription and secretion of interleukin-1 receptor antagonist (IL-1ra) and IL-8 in cultures of normal human monocytes. The addition of IVIg to cultures of purified monocytes induced a dose-dependent secretion of IL-1ra and IL-8 without stimulating the production of IL-1 alpha, IL-1 beta, tumor necrosis factor-alpha or IL-6. The effects of IVIg required both the Fc and F(ab')2 portions of IgG. IVIg-induced production of IL-8 by monocytes was enhanced by lipopolysaccharide (LPS), although LPS inhibited the secretion of IL-1ra, suggesting that IVIg and LPS stimulate distinct intracellular pathways in monocytes. Induction of IL-1ra and IL-8 by IVIg was enhanced in the presence of autologous T lymphocytes. Our observations document the selectivity of the effects of IVIg on the synthesis of cytokines and cytokine antagonists by human monocytes. Induction of IL-1ra and IL-8 by IVIg may contribute to the anti-inflammatory effects of immunoglobulin therapy in patients with autoimmune and systemic inflammatory disorders.

Intravenous immunoglobulin (IVIg) in the treatment of autoimmune and inflammatory diseases.

The beneficial effect of intravenous immunoglobulin (IVIg) in certain autoimmune disorders has led to the development of clinical trials in a large number of autoimmune and systemic inflammatory diseases. Experimental studies are being carried out to understand better the mechanisms of action of IVIg. In this review, we discuss the clinical use of IVIg in autoimmune disorders and outline the possible mechanisms by which IVIg may be exerting an immunoregulatory effect in various autoimmune and systemic inflammatory diseases. A clear understanding of the mechanisms of action of IVIg in autoimmune diseases will facilitate the optimization of their use as a therapeutic alternative to conventional immunosuppression.