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Veterinary Wounds
Veterinary Wounds
Mast cells (MCs) are found in many tissues and contain granules rich in histamine and heparin and a battery of mediators with proinflammatory and immunoregulatory potential. Although best known for their role in anaphylaxis and allergy, MCs also have an important protective role, as they are intimately involved in wound healing and defence against invasive pathogens.1,2 They are thought to originate from bone marrow precursors expressing the CD34 molecule and circulate in an immature form until they reach a tissue site where they mature and develop their definitive characteristics.3
Mast cells play a major role in the inflammatory stage of the wound healing process and release proinflammatory mediators. Large numbers are expressed in the skin, where they represent 2%–8% of dermal cells, and cutaneous MCs have been found to be localized in the epidermis and hair follicles, and close to blood vessels and nerves.4 It is because they produce so many proinflammatory and growth-promoting mediators such as histamine, leukotrienes, prostaglandins, proteases, and cytokines4 that the hypothesis that MCs contribute to skin healing has developed.
They are activated either by direct injury or by activated complement proteins when they are stimulated to release granules and hormonal mediators into the interstitium. Mast cells express a high-affinity receptor (FceRI) for the Fc region of immunoglobulin (IgE), the least commonly circulating antibody produced by B-cells: the antibody-producing cells of the immune system.3 This receptor is of such high affinity that binding of IgE molecules is essentially irreversible. As a result, MCs are coated with IgE.
It should be mentioned here that although there is an extensive body of suggestive evidence in support of MC functions during wound healing,1,5 a debate still exists, and the precise role of MCs in the process has yet to be proven.5 Recently, several authors6,7 have suggested that MCs are unnecessary for uncomplicated wound healing. Therefore, because of these uncertainties, a review by Werner and Grose8 does not list MCs as participants in the wound healing process. However, a review published in 2008 states that there is new understanding regarding the role of MCs in wound healing and lists wound healing among the basic functions of MCs.9
However, the following work by Abramo et al lends valuable insight into the contribution of MCs to the observed accelerated healing of experimental cutaneous wounds by application of the aliamide adelmidrol. Adelmidrol (N,N'-bis(2-hydroxyethyl)nonandiamide) has amphipathic properties and is used as a cosmetic agent in humans and animals for application to skin and mucous membranes, which are either irritable or subject to acute irritation. It is currently under development (by Innovet Italia srl, Milan) as a topical aid to wound healing. The Abramo et al study was designed to examine the effect of the 2% w/w experimental gel on morphometric and densitometric features of MCs, and on MC counts, during healing of experimental skin wounds. Histological influence of adelmidrol on the degranulation of MCs was assessed on punch biopsy wounds taken from the 2 dorsal paramedial thoracolumbar areas of 10 dogs over a 14-day period. Toluidine blue-stained sections were prepared, skin MCs were counted and densitometric analysis was used to assess their granular content. These data show that although there were no statistically significant differences in MC counts, there was a significantly greater mean granule content shown in treated wounds when compared to controls, thereby, suggesting that the aliamide has down regulated the skin MCs in the wound area without significantly influencing their number.
