Influência da terapia laser de baixa intencidade em células precursoras miogênicas (in vitro) e durante a regeneração muscular (in vivo).
Resumo
The Low Intensity Laser Therapy (LILT) constitutes one of the resources most used by
physical therapists, with the goal of stimulating the process of repairing the skeleton muscle
tissue. On the other hand, the intense utilization, its respective action mechanisms and
therapeutic effectiveness are not scientifically proved. Based on this, we elaborated the
present study aiming to investigate the influence of the LILT, at wavelengths (λ) usually
used at clinical practices (670, 685 and 830 nm), on the function of the Myogenic Precursor
Cells (MPCs), directly responsible for the tissue regeneration process. The beginning phase
was carried out throughout in vitro experiments, determining the alterations started by
radiations over the proliferation ability and the cellular differentiation. The MPCs used
were in the second passage, after had been extracted from four days old Wistar rats. To
analyze the proliferation, it was elaborated, for each λ, a dose-response data curve
including the control group constituted of non-radiated cells, and the irradiated groups with
doses of 0.3; 0.6; 0.9; 1.2; and 1.5 J/cm2. This procedure was carried out with the cells
under the influence of 5 or 10% of fetal bovine serum (FBS). The dose demonstrating the
highest effectiveness on the cellular proliferation in each radiation, was used to establish
the influence on the process of cellular differentiation, and investigated throughout the
analysis of the expression of the genes related to the isoforms IIa and IIx of the myosin
heavy chain (MHC). The final phase of the study was pointed towards the radiation action
evaluation, at the same dose parameters used before, on the muscle regeneration process in
vivo, after induced cryoscopy lesion at the Tibialis anterior muscles of adults Wistar rats.
There were evaluations of the histological, histochemical aspects for the Succinic
Dehydrogenase enzyme (SDH) and the activity of the Lactate Dehydrogenase enzymes
(LDH) and Citrate Sintase (CS). The outcomes demonstrated that the radiation at λ of 670,
685 and 830 nm promoted an increase of 56.8, 70.6 and 84.8 % on the proliferate ability of
the PMCs. These values were achieved with the 1.2, 0.6 and 0.3 J/cm2 doses respectively,
and with the cells under the influence of 5% of FBS. The highest concentration of serum
(10% of FBS) determined a less pronounced bio-stimulating effect, rising only 13.6, 17.5
and 10.9 %, respectively. In relation to the MHC isoforms expression rate, it showed that
there was a significant fall of the IIa isoform, due to the action of the 685 nm, and an
increase of the IIx isoform, due to the action of the 685 and 830 nm radiations, in relation
to the non-radiated cells rate. By means of in vivo analysis, it was possible to demonstrate
the ability of radiation at λ of 685 and 830 nm on increasing DHL enzymes and CS during
the muscle regeneration process. Therefore, according to the outcomes it is allowed to
attribute to the LILT an ability λ and dose-dependent of influencing the proliferation
function and the metabolism of the MPCs. It was not possible to infer its effect on the
cellular differentiation process, because of the inverted effect on the MHC isoforms
expression, though.