Dual role of miR-1 in the development and function of sinoatrial cells.

miR-1, the most abundant miRNA in the heart, modulates expression of several transcription factors and ion channels. Conditions affecting the heart rate, such as endurance training and cardiac diseases, show a concomitant miR-1 up- or down-regulation. Here, we investigated the role of miR-1 overexpression in the development and function of sinoatrial (SAN) cells using murine embryonic stem cells (mESC). We generated mESCs either overexpressing miR-1 and EGFP (miR1OE) or EGFP only (EM). SAN-like cells were selected from differentiating mESC using the CD166 marker. Gene expression and electrophysiological analysis were carried out on both early mES-derived cardiac progenitors and SAN-like cells and on beating neonatal rat ventricular cardiomyocytes (NRVC) over-expressing miR-1. miR1OE cells increased significantly the proportion of CD166+ SAN precursors compared to EM cells (23% vs 12%) and the levels of the transcription factors TBX5 and TBX18, both involved in SAN development. miR1OE SAN-like cells were bradycardic (1,3 vs 2 Hz) compared to EM cells. In agreement with data on native SAN cells, EM SAN-like cardiomyocytes show two populations of cells expressing either slow- or fast-activating If currents; miR1OE SAN-like cells instead have only fast-activating If with a significantly reduced conductance. Western Blot and immunofluorescence analysis showed a reduced HCN4 signal in miR-1OE vs EM CD166+ precursors. Together these data point out to a specific down-regulation of the slow-activating HCN4 subunit by miR-1. Importantly, the rate and If alterations were independent of the developmental effects of miR-1, being similar in NRVC transiently overexpressing miR-1. In conclusion, we demonstrated a dual role of miR-1, during development it controls the proper development of sinoatrial-precursor, while in mature SAN-like cells it modulates the HCN4 pacemaker channel translation and thus the beating rate.

1,25-Dihydroxyvitamin D3 in the treatment of idiopathic thrombocythemia and myelofibrosis.

The effect of treatment with 1,25-dihydroxyvitamin D3 administered at the dose of 1.50-3.00 ug/day for at least 12 months was evaluated in three patients with idiopathic myelofibrosis and in five patients with idiopathic thrombocythemia. This treatment did not cause any significant change in the hematological values or the clinical course of the myeloproliferative diseases in any of the patients. Based on these data, treatment with 1,25-dihydroxyvitamin D3 in non toxic doses seems to be of doubtful benefit in patients with these disorders.

Immunoreactive calcitonin: a tumor marker for myelogenous leukemias.

In a series of 59 patients with chronic or acute myelogenous leukemia (CML, AML) we investigated whether circulating immunoreactive human calcitonin (i-hCT) levels correlate with diagnosis, response to therapy and clinical course. I-hCT was detectable in plasma samples of 88% of patients with CML in the chronic phase and in 100% of patients with CML in blastic transformation. In the AML patients, a significant relation was observed between the cytological subtype and i-hCT levels at diagnosis. In sequentially studied patients the i-hCT plasma concentration was related to the overall mass of leukemic cells, being lower when complete remission was achieved than at diagnosis and increasing at time of recurrence. These data suggest that circulating i-hCT levels can serve as a "tumor marker" in human myelogenous leukemias.