Phase-contrast magnet resonance imaging reveals regional, transmural, and base-to-apex dispersion of mechanical dysfunction in patients with long QT syndrome.

BACKGROUND: Regional dispersion of prolonged repolarization is a hallmark of long QT syndrome (LQTS). We have also revealed regional heterogeneities in mechanical dysfunction in transgenic rabbit models of LQTS. OBJECTIVE: In this clinical pilot study, we investigated whether patients with LQTS exhibit dispersion of mechanical/diastolic dysfunction. METHODS: Nine pediatric patients with genotyped LQTS (12.2 ± 3.3 years) and 9 age- and sex-matched healthy controls (10.6 ± 1.5 years) were subjected to phase-contrast magnetic resonance imaging to analyze radial (Vr) and longitudinal (Vz) myocardial velocities during systole and diastole in the left ventricle (LV) base, mid, and apex. Twelve-lead electrocardiograms were recorded to assess the heart rate-corrected QT (QTc) interval. RESULTS: The QTc interval was longer in patients with LQTS than in controls (469.1 ± 39.4 ms vs 417.8 ± 24.4 ms; P < .01). Patients with LQTS demonstrated prolonged radial and longitudinal time-to-diastolic peak velocities (TTP), a marker for prolonged contraction duration, in the LV base, mid, and apex. The longer QTc interval positively correlated with longer time-to-diastolic peak velocities (correlation coefficient 0.63; P < .01). Peak diastolic velocities were reduced in LQTS in the LV mid and apex, indicating impaired diastolic relaxation. In patients with LQTS, regional (TTPmax-min) and transmural (TTPVz-Vr) dispersion of contraction duration was increased in the LV apex (TTPVz_max-min: 38.9 ± 25.5 ms vs 20.2 ± 14.7 ms; P = .07; TTPVz-Vr: -21.7 ± 14.5 ms vs -8.7 ± 11.3 ms; P < .05). The base-to-apex longitudinal relaxation sequence was reversed in patients with LQTS compared with controls (TTPVz_base-apex: 14.4 ± 14.9 ms vs -10.1 ± 12.7 ms; P < .01). CONCLUSION: Patients with LQTS exhibit diastolic dysfunction with reduced diastolic velocities and prolonged contraction duration. Mechanical dispersion is increased in LQTS with an increased regional and transmural dispersion of contraction duration and altered apicobasal longitudinal relaxation sequence. LQTS is an electromechanical disorder, and phase-contrast magnetic resonance imaging Heterogeneity in mechanical dysfunction enables a detailed assessment of mechanical consequences of LQTS.

Mutation analysis of the apoptotic "death-receptors" and the adaptors TRADD and FADD/MORT-1 in osteosarcoma tumor samples and osteosarcoma cell lines.

Apoptosis is a key mechanism of the organism that regulates embryogenesis and development, maintains homeostasis of the immune system and removes potentially hazardous cells. A dysregulation of apoptosis signaling may thus disturb the balance of cell survival and cell death, leading to the development of several diseases including cancer. In order to determine whether osteosarcomas display an increased frequency of genetic alterations that affect apoptosis signaling, we analyzed the death domains of the death receptor genes CD95/Fas/Apo1, TNFR1, DR3/Apo3/WSL-1/LARD/TRAMP, DR5/TRAIL-R2/TRICK2/KILLER, DR6 and the complete coding sequences of the death receptor gene DR4/TRAIL-R1 and the genes of the adaptors TRADD and FADD/MORT-1. The investigation included 15 osteosarcoma tumor samples, 3 osteosarcoma cell lines (SAOS-2, HOS and MG63) and peripheral blood from 20 donors as controls. We were able to identify 4 different sequence variations within the DR4 gene located on exons 3, 4, 5 and 10 (death-domain). No alterations have been detected in the other genes or exons investigated. Except the sequence variant affecting exon 4, the alterations were homozygous in 15% of the tumor samples and cell lines, whereas the same alterations found in the control group were heterozygous or even not detectable. Three out of 4 alterations are located in the receptor's extracellular cysteine rich domain, which contains the ligand binding area and 1 on exon 10 coding for the death-domain. They may thus exert influence on ligand-receptor interactions and subsequent apoptosis induction. Our findings suggest that homozygous genetic alterations within the DR4 gene may be implicated in the formation of osteosarcoma.

Identification of drug-regulated genes in osteosarcoma cells.

The introduction of systemic chemotherapy improved significantly the prognosis of osteosarcoma. Despite this success, approximately 30-40% of patients will relapse. Cytotoxic drugs have been shown to induce apoptosis in the target cells independent of their primary effects. The underlying molecular mechanisms and the intracellular mediators, however, are still largely unknown. Therefore, the purpose of our study was to identify drug-regulated genes in osteosarcoma cells useful as prognostic factors and for the development of new therapeutic strategies. Using suppressive subtractive hybridization (SSH) the gene expression pattern of untreated Saos-2 cells was compared to cells treated with cisplatin, methotrexate and doxorubicin, respectively. We identified 8 genes that are regulated >2-fold in drug-treated osteosarcoma cell lines. Expression of ferritin light chain, rhoA, inosine monophosphatdgehydrogenase II, ribonucleotide reductase M2, pro2000 and pro1859 were increased after drug treatment, whereas prohibitin and alpha-actinin expressions were significantly downregulated. Differential expression of the identified genes was verified by Northern blot analysis of 3 different osteosarcoma cell lines. In addition, the effects on chemosensitivity of 4 selected genes was analyzed by overexpression of recombinant constructs in Saos-2 cells and subsequent quantification of drug-induced apoptosis. Overexpression of prohibitin and rhoA reduced significantly drug sensitivity to approximately 52% and 59% indicating a crucial role in the modulation of drug-induced cell death.