Efeitos do transplante de células mononucleares de medula óssea na hipertensão espontânea em ratos

Abstract

In the present study, the effects of transplantation of bone marrow-mononuclear cells (MNT) from isogenic adult (Ad) or young (Yo) spontaneously hypertensive rats (SHR) or allogenic normotensive Wistar-Kyoto (WKY) rats on systemic arterial blood pressure levels of receptor SHRs were assessed. Bone marrow-mononuclear cells were extracted from tibiae, femurs and umerus of isogenic male adult (16 weeks-old aged rats, MNT-Ad, n=4) or young (4 weeks-old rats, MNT-Yo, n=2) donor SHRs or allogenic male adult normotensive WKY rats (16 weeks-old aged rats, MNT-WKY, n=2) and injected (5x106 cells/rats, i.v.) in 24 female 16-20 weeks-old aged receptor SHRs (respectively, MNT-Ad, n=10, MNT-Yo, n=7 and MNT-WKY, n=7). Mononuclear cells were labeled using fluorescent stain celltracker CM-DiI, before administration in order to track cell destination. Age-matched female SHRs receiving only vehicle formed control groups (CON, n=15). Indirect arterial pressure (AP) were daily or each two days recorded by means of caudal artery occlusion method during one week before and until two weeks after cell transplantation in all experimental groups. At the ending, after previous canulation (performed 24-48 hours before), all animals were submitted to a pulsatile direct AP recording session during one hour in conscious freely moving conditions. Following, all animals were euthanized under supra-dosage of anesthetic sodium thiopental (100mg/Kg, i.p.) and fluorescence microscopy was used on thin sections of several organs including kidneys, spleen, lung and heart in order to track donor CM-DiI+ cells. In both groups submitted to isogenic transplantation (MNT-Ad and MNT-Yo), AP was significantly reduced after the third day, remaining lower until the end of observation period. Confirming these findings, the values of mean AP directly measured were 137±4mmHg in MNT-Ad group and 136±3mmHg in MNT-Yo group (versus 163±5mmHg in CON group, p<0.005). In addition, no difference in heart rate variability and spontaneous baroreflex sensitivity parameters were observed while variance, very low frequency and low frequency components of arterial pressure variability were significantly lowers in both MNT-Ad and MNT-Yo groups. A significant reduction in cardiac hypertrophy, probably due to the relief in hemodynamic overload on left ventricle was also observed. No changes were verified in glomerular density in both MNT-Yo and MNT-Ad groups, compared to CON group. Small amounts of CM-DiI+ cells were found in several tissues, including the kidneys, while a great amount of labeled transplanted cells were present into the spleen of the animals that received isogenic transplantation. On the other hand, in SHRs submitted to allogenic transplantation with WKY cells (MNT-WKY group), no reduction in AP was observed after eleven day of observation. According to this, direct AP measurements in MNT-WKY animals were not different of control animals. In addition, no changes in cardiovascular variability, baroreflex sensitivity, cardiac hypertrophy and glomerular density were observed in MNT-WKY animals. In this allogenic transplantation, labeled transplanted WKY cells were found only into the spleen, suggesting immune rejection. All these findings indicate that isogenic, in immunocompetent animals, transplantation of bone marrow-mononuclear cells with different ages is able to consistently reduce arterial blood pressure in systemic arterial hypertension.