Efeitos da vibração mecânica sobre o tecido ósseo e nervoso periférico de ratas wistar ooforectomizadas

Abstract

Vibratory platform vibration therapy used in the treatment of postmenopausal osteoporosis because it can promote anabolic effects on bone tissue, but the parameters of use, especially the time of application, are not established. In addition, despite the beneficial effects of vibration, it is known that it can cause peripheral nerve damage. However although mentioned, there is no scientific evidence documenting the effects of this stimulus on the peripheral nerve in parameters used in therapies. Thus, is relevant the study of the mechanical vibration during different periods on the bone tissue, besides analyzing the effects on the nervous tissue. The aim of this study was to analyze and compare the effects of mechanical vibration applied over four and eight weeks on the femur and sciatic nerve of oophorectomized Wistar rats. Sixty-six randomized rats were used in the oophorectomy (GO) and sham-oophorectomy (GP) groups (n = 32 / group). Subsequently, each group was subdivided into 4, euthanized groups in the 12th week of experiment (GP4, GO4, GPV4 and GOV4), and GPV4 and GOV4 were submitted to vibration for 4 weeks; (GP8, GO8, GPV8 and GOV8), and GPV8 and GOV8 groups were submitted to vibration for 8 weeks. The vibration was performed with frequency of 60Hz, for 10 minutes, three days a week. Nociception of the right hind paw was evaluated before the surgical procedure, at the beginning of the treatment and at the end of the treatment with vibration. After the experimental period, the animals were euthanized, and the right sciatic nerve and femur were dissected for histomorphometric analysis. Were measured in 100 fibers nerve the diameter of the fiber, axon, myelin sheath, and quotient g, also were realized the counts of smaller fibers and larger than four micrometers and of the Schwann cell nuclei, as well as the percentage of connective tissue. The femur was analyzed for femoral neck diameter, mean area of cortical bone, percentage of spongy bone, thickness measurement and percentage of cortical bone, as well as osteocyte count. From the analyzes it was observed that the nociception and morphometry of the sciatic nerve morphometry did not have a statistically significant difference; in addition, in the morphological analysis of the sciatic nerve, the groups presented similar characteristics among themselves, without altering the typical morphology. While in the femur, the vibration in the oophorectomized groups led to the increase of the bone mass, being observed the increase of the percentage of the spongy tissue, which was also evidenced in the cortical tissue, with increase of the thickness and the percentage of bone tissue, being the was able to reverse these changes. However, the variables of the mean area of the cortical bone, number of osteocytes and the diameter of the femoral neck were not altered by vibration. With this, it was concluded that the vibration during four and eight weeks promoted increase of the bone mass, whereas it did not have effects on the sciatic nerve of oophorectomized Wistar.