Depletion of HIF-1α by Inducible Cre/loxP Increases the Sensitivity of Cultured Murine Hepatocytes to Ionizing Radiation in Hypoxia.

The transcription factor hypoxia-inducible factor (HIF) is the main oxygen sensor which regulates adaptation to cellular hypoxia. The aim of this study was to establish cultured murine hepatocyte derived cells (mHDC) as an in vitro model and to analyze the role of HIF-1α in apoptosis induction, DNA damage repair and sensitivity to ionizing radiation (IR). We have crossed C57/BL6 mice that bear loxP sites flanking exon 2 of Hif1a with mice which carry tamoxifen-inducible global Cre expression. From the offspring, we have established transduced hepatocyte cultures which are permanently HIF-1α deficient after tamoxifen treatment. We demonstrated that the cells produce albumin, acetylcholine esterase, and the cytokeratins 8 and 18 which functionally characterizes them as hepatocytes. In moderate hypoxia, HIF-1α deficiency increased IR-induced apoptosis and significantly reduced the surviving fraction of mHDC as compared to HIF-1α expressing cells in colony formation assays. Furthermore, HIF-1α knockout cells displayed increased IR-induced DNA damage as demonstrated by increased generation and persistence of γH2AX foci. HIF-1α deficient cells showed delayed DNA repair after IR in hypoxia in neutral comet assays which may indicate that non-homologous end joining (NHEJ) repair capacity was affected. Overall, our data suggest that HIF-1α inactivation increases radiation sensitivity of mHDC cells.

Phalloplasty in Female-to-Male Transsexuals by Gottlieb and Levine's Free Radial Forearm Flap Technique-A Long-Term Single-Center Experience Over More than Two Decades.

BACKGROUND: The free radial forearm flap phalloplasty is the most utilized method for penile reconstruction. Among the techniques described in the literature, evidence for the flap design after Gottlieb and Levine is poor. METHODS: From January 1993 until December 2015, 402 phalloplasties were performed in our clinic. Among the 247 free radial forearm flap phalloplasties, 232 free radial forearm flap phalloplasties were performed after Gottlieb and Levine in 229 patients. Operation and patient-specific characteristics were evaluated. RESULTS: This study presents the highest number of free radial forearm flap phalloplasties after Gottlieb and Levine. The rate of total flap failure was 3%; 46% of the patients were heavy smokers. Urinary fistulae and strictures are common. The revision rate for urinary fistulae and/or strictures was 1.3 per patient. The number of postoperative complications, such as bleeding (14.2%), thrombosis of the flap requiring revision (11.2%), or delayed wound healing (16.8%) was considering the high rate of nicotine abuse (45.9%) reasonable. CONCLUSION: The free radial forearm phalloplasty in the design by Gottlieb and Levine is well established at our institution and has proven safe and reliable since 1993. The operative results are satisfactory for both patients and surgeons even in the presence of relevant comorbidities and heavy smoking. We acknowledge the long ordeal and psychological pressure that our patients suffer from, before presenting in our outpatient clinic.