Regulation of miR-29b and miR-30c by vitamin D receptor activators contributes to attenuate uraemia-induced cardiac fibrosis

Background

Uraemic cardiomyopathy, a process mainly associated with increased myocardial fibrosis, is the leading cause of death in chronic kidney disease patients and can be prevented by vitamin D receptor activators (VDRAs). Since some microRNAs (miRNAs) have emerged as regulators of the fibrotic process, we aimed to analyse the role of specific miRNAs in VDRA prevention of myocardial fibrosis as well as their potential use as biomarkers.

Methods

Wistar rats were nephrectomized and treated intraperitoneally with equivalent doses of two VDRAs: calcitriol and paricalcitol. Biochemical parameters, cardiac fibrosis, miRNA (miR-29b, miR-30c and miR-133b) levels in the heart and serum and expression of their target genes collagen I (COL1A1), matrix metalloproteinase 2 (MMP-2) and connective tissue growth factor (CTGF) in the heart were evaluated.

Results

Both VDRAs attenuated cardiac fibrosis, achieving a statistically significant difference in the paricalcitol-treated group. Increases in RNA and protein levels of COL1A1, MMP-2 and CTGF and reduced expression of miR-29b and miR-30c, known regulators of these pro-fibrotic genes, were observed in the heart of chronic renal failure (CRF) rats and were attenuated by both VDRAs. In serum, significant increases in miR-29b, miR-30c and miR-133b levels were observed in CRF rats, which were prevented by VDRA use. Moreover, vitamin D response elements were identified in the three miRNA promoters.

Conclusions

VDRAs, particularly paricalcitol, attenuated cardiac fibrosis acting on COL1A1, MMP-2 and CTGF expression, partly through regulation of miR-29b and miR-30c. These miRNAs and miR-133b could be useful serum biomarkers for cardiac fibrosis and also potential new therapeutic targets.

Vitamin D receptor activation, left ventricular hypertrophy and myocardial fibrosis

BACKGROUND

Left ventricular hypertrophy (LVH), a common complication in chronic kidney disease (CKD), is associated with high cardiovascular mortality. The aim of this experimental study was to analyze the effect of different vitamin D receptor activators (VDRAs) on both LVH and myocardial fibrosis in chronic renal failure (CRF).

METHODS

Male Wistar rats with CRF, carried out by 7/8 nephrectomy, were treated intraperitoneally with equivalent doses of VDRAs (calcitriol, paricalcitol and alfacalcidol, 5 days per week) during 4 weeks. A placebo group (CRF + vehicle) and a Sham group with normal renal function served as controls. Biochemical, morphological, functional and molecular parameters associated with LVH were evaluated, as well as cardiac fibrosis, collagen I, transforming growth factor β1 (TGFβ1) and matrix metalloproteinase-1 (MMP1) expression.

RESULTS

All VDRAs treatment prevented LVH, with values of cardiomyocyte size, LV wall and septum thickness and heart-body weight ratio similar to those observed in the Sham group. At molecular levels, all VDRAs attenuated atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression compared with CRF + vehicle. The phosphorylation of ERK1/2, a signal for activating growth, was stimulated in the CRF + vehicle group; VDRAs use prevented this activation. Paricalcitol was the only VDRA used that maintained in the normal range all parameters associated with myocardial fibrosis (total collagen, collagen I, TGFβ1 and MMP1).

CONCLUSIONS

Our findings demonstrated that the three VDRAs used induced similar changes in bone metabolic parameters and LVH. In addition, paricalcitol was the only VDRA which showed a relevant beneficial effect in the reduction of myocardial fibrosis, a key factor in the myocardial dysfunction in CKD patients.

IgV(H) and bcl6 somatic mutation analysis reveals the heterogeneity of cutaneous B-cell lymphoma, and indicates the presence of undisclosed local antigens

Our understanding of the ontology of B-cell lymphomas (BCL) has been improved by the study of mutational status of IgV(H) and bcl6 genes, but only a few cases of cutaneous BCL have been examined for this status. We analyzed IgV(H) and bcl6 somatic mutations in 10 cutaneous BCL, classified as follicular (three primary and one secondary), primary marginal zone (two cases), and diffuse large BCL (three primary and one secondary). We observed a lower rate (<2%) of IgV(H) mutation in all marginal zone lymphomas, and a preferential usage of V(H)2-70 (one primary follicular and two primary diffuse large BCL). Fewer than expected replacement mutations in framework regions (FR) were observed in three primary follicular lymphomas (FLs) and in all diffuse large BCL, indicating a negative antigen selection pressure. Ongoing mutations were observed in eight of 10 cases. Only two primary FLs and two diffuse large BCL showed bcl6 somatic mutation. These data support the heterogeneous nature of the different cutaneous BCL, and specifically the distinction between cutaneous follicular and marginal zone lymphomas. The biased usage of V(H)2-70, the low rate of replacement mutation in the FR, and the presence of ongoing mutation imply that local antigens could modulate the growth of primary cutaneous BCL.

Cutaneous presentation of follicular lymphomas

The description of primary cutaneous follicular lymphoma has raised interest in the differential diagnosis of this versus disseminated follicular lymphoma involving the skin. We report here on four cases of Stage IV follicular lymphoma, diagnosed in skin biopsy, in which cutaneous lesion was the most noticeable feature of clinical presentation. In all cases, the morphological features were superimposed over typical nodal follicular lymphoma. Apart from classic B-cell markers, they were characterized by CD10 and bcl6 positivity, markers of follicle germinal center cells; and bcl2 expression, with a corresponding t(14;18) translocation in three of three cases examined. In all four cases, bone marrow study and clinical staging revealed disease that had disseminated since diagnosis. Follow-up showed relapsing cutaneous and nodal disease in two cases. The only difference observed with a control group of 10 cases of primary cutaneous follicular lymphoma was the absence in this group of t(14; 18). Disseminated classical follicular lymphoma has to be considered in the differential diagnosis of follicular lymphoma presenting in the skin. This series of cases suggests that the presence of t(14;18) could imply the existence of disease that has disseminated beyond the skin and that cases harboring this translocation could be candidates for systemic polychemotherapy.

Primary cutaneous large B-cell lymphoma: the relation between morphology, clinical presentation, immunohistochemical markers, and survival

The histogenesis, morphology, immunophenotype, and clinical behavior of cutaneous large B-cell lymphomas (CLBCL) are largely a matter of controversy. We performed an investigation to determine whether CLBCL have features that differentiate them from other large B-cell lymphomas and whether CLBCL is itself a heterogeneous group. To this end, we reviewed the main characteristics of a series of 32 cases of LBCL found in the skin. We reviewed the clinical findings and paraffin sections of the tumors from these 32 patients. The immunohistochemical study performed included p53, MIB1, Bcl2, Bcl6, and CD10 markers. We carried out statistical analysis of these data (univariate and multivariate), seeking an association between the features of the tumors and clinical outcome, as defined by failure-free survival time. Only one patient died as a consequence of the lymphoma. Nevertheless, the accumulated probability of survival without failure at 48 months was 0.46. The number, type, and localization of the lesions were not associated with variations in either survival or failure-free survival. The expression of p53 was negative in this group of CLBCL, whereas Bcl-2 expression or localization in the lower leg did not relate to any other significant feature. Histologic examination of the cases disclosed three different groups: Grade III follicular lymphomas (FLs), monomorphous large B-cell lymphomas (LBCL type I), and LBCL with an admixed component of small B-lymphocytes (LBCL type II). Grade III FL (11 cases) tended to be found in the head and neck and showed CD10 expression in a majority of cases. A higher probability of lymph node relapses was associated with cases located in the head and neck and with CD10+ tumors. Cutaneous large B-cell lymphomas are indolent tumors, but follow an insidious course. Our data support the interpretation that CLBCL is a heterogeneous condition; comprises some LBCL derived from CD10+ germinal center cells which manifests more frequently as tumors in the head and neck region, with an increased probability of relapse in lymph nodes [1] and has some distinctive morphologic features. The existence of a component of small B-cells within the other CLBCL could lend support to the theory that some of these tumors, more than arise de novo, may have originated in preexistent small B-cell lymphomas, but no firm evidence of this is provided in this study.