Resumo:
Oral mucositis (OM) is one of the most common acute complications of cancer therapy,
caused by the cytotoxic effects of head and neck chemotherapy or radiotherapy. It has
been suggested that the effect of laser photobiomodulation on microcirculation occurs
due to stimulation of mast cell degranulation and consequent increase in cell
permeability, as these cells produce and release a wide range of chemical mediators
associated with different biological processes. The aim this study was to evaluate the
influence of laser photobiomodulation on mast cell expression and degranulation in
chemoinduced oral mucositis lesions. Thirty-six Syrian hamsters (Mesocrietus auratus)
of the golden lineage, adult and male, were randomly assigned to four large groups
according to the experimental procedure: Untreated Mucositis (M), Mucosite with Red
Laser (LV) (GaAlAs, λ660nm, 40mW, 0.04cm2, t = 30s, D = 2.4J / cm2, Twin Flex
Evolution, MMoptics®, São Carlos, SP) and Infrared Laser Mucositis (LI) λ780nm,
40mW, 0.04cm2, t = 30s, D = 2.4J / cm2, Twin Flex Evolution, MMoptics®, São Carlos,
SP). The groups were subdivided into 3 subgroups according to the time of death of
the animals: 7, 11 and 15 day groups (M-7, M-11, M-15, LV-7, LV -11, LV-15, LI-7, LI 11, and LI-15). OM injuries were caused by making grooves in the right cheek pouch
of each animal and, immediately after the procedure, they were subjected to irradiation,
which was repeated every 48 hours, until the animals died. The specimens were
processed and stained using Hematoxylin-eosin and Toluidine Blue techniques. The
results showed that among the irradiated groups, LV-7 presented the highest mean
mast cell expression (38.28 ± 19.05) (p <0.001). Regarding degranulation, the group
with the largest number of fields with more than 50% of degranulated mast cells was
M-11 (p <0.001) and, among the irradiated ones, LV-11 (p = 0.008). Laser irradiation
at both wavelengths decreased the percentage of mast cell degranulation. The group
irradiated with infrared laser showed lower expression of mast cells and lower
percentage of mast cells in degranulation. There was a predominance of mild chronic
inflammation. In general, it was not possible to observe significant expression of
degranulated mast cells in the irradiated groups, which suggests that laser light may
accelerate the inflammatory process and proposes future analysis in groups with
shorter experimental time.
