[Total Aortic Arch Replacement. Does a management protocol impact the results?] / Reemplazo Total de Arco Aórtico. ¿Un protocolo de manejo impacta en los resultados?

Aortic arch surgery is a surgical challenge due to its technical complexity and brain and body protection requirements. AIM: To describe the surgical protocol and the short and long-term results of aortic arch replacement surgery in a center in the metropolitan region of Santiago, Chile. METHODS: Retrospective descriptive study from April 2015 to August 2022. Elective, urgent, and emergency patients were included, with diagnoses of arch aneurysm and acute or chronic type I and II DeBakey aortic dissection. TECHNIQUE: Arterial cannulation at the brachiocephalic trunk, right axillary artery, or directly into the true lumen of the aortic dissection with Seldinger technique, guided by epiaortic and transesophagic ultrasound. Deep hypothermia at 24°C. Uni or bilateral antegrade cerebral perfusion according to runoff. Four devices were used: a straight tube, a tube with 3 or 4 branches, and a frozen elephant trunk. RESULTS: 37 patients were operated on; 24 of them were men. The average age was 57 years old. In seven patients, a straight tube with anastomosis was used with anastomosis on the island; in six patients, a tube with 3 branches; in ten patients, a tube with four branches; and in fourteen patients, a frozen elephant trunk. There were twenty-one patients (57%) with associated morbidity: prolonged mechanical ventilation 14 the most frequent, paralysis chordae in 7 patients; there were six neurological morbidities, one of them permanent, renal dysfunction in 5 patients, pneumonia associated with mechanical ventilation in 4 patients, reoperation due to bleeding in 4. There was no associated cardiac morbidity. Operative and global mortality at 30 days was 13.5%. Follow-up was closed in October 2022 and is complete in the 30 survivors; the average was 20 months. Two patients died in the follow-up at five years; the survival in the follow-up was 90%. CONCLUSION: The management protocol has good results regarding morbidity and mortality, similar to the international series.

H3K9 Methyltransferases Suv39h1 and Suv39h2 Control the Differentiation of Neural Progenitor Cells in the Adult Hippocampus.

In the dentate gyrus of the adult hippocampus new neurons are generated from neural precursor cells through different stages including proliferation and differentiation of neural progenitor cells and maturation of newborn neurons. These stages are controlled by the expression of specific transcription factors and epigenetic mechanisms, which together orchestrate the progression of the neurogenic process. However, little is known about the involvement of histone posttranslational modifications, a crucial epigenetic mechanism in embryonic neurogenesis that regulates fate commitment and neuronal differentiation. During embryonic development, the repressive modification trimethylation of histone H3 on lysine 9 (H3K9me3) contributes to the cellular identity of different cell-types. However, the role of this modification and its H3K9 methyltransferases has not been elucidated in adult hippocampal neurogenesis. We determined that during the stages of neurogenesis in the adult mouse dentate gyrus and in cultured adult hippocampal progenitors (AHPs), there was a dynamic change in the expression and distribution of H3K9me3, being enriched at early stages of the neurogenic process. A similar pattern was observed in the hippocampus for the dimethylation of histone H3 on lysine 9 (H3K9me2), another repressive modification. Among H3K9 methyltransferases, the enzymes Suv39h1 and Suv39h2 exhibited high levels of expression at early stages of neurogenesis and their expression decreased upon differentiation. Pharmacological inhibition of these enzymes by chaetocin in AHPs reduced H3K9me3 and concomitantly decreased neuronal differentiation while increasing proliferation. Moreover, Suv39h1 and Suv39h2 knockdown in newborn cells of the adult mouse dentate gyrus by retrovirus-mediated RNA interference impaired neuronal differentiation of progenitor cells. Our results indicate that H3K9me3 and H3K9 methyltransferases Suv39h1 and Suv39h2 are critically involved in the regulation of adult hippocampal neurogenesis by controlling the differentiation of neural progenitor cells.