CRISPR/Cas and recombinase-based human-to-pig orthotopic gene exchange for xenotransplantation.

BACKGROUND: Tools for genome editing in pigs are improving rapidly so that making precise cuts in DNA for the purposes of deleting genes is straightforward. Development of means to replace pig genes with human genes with precision is very desirable for the future development of donor pigs for xenotransplantation. MATERIALS AND METHODS: We used Cas9 to cut pig thrombomodulin (pTHBD) and replace it with a plasmid containing a promoterless antibiotic selection marker and the exon for human thrombomodulin. PhiC31 recombinase was used to remove the antibiotic selection marker to create porcine aortic endothelial cells expressing human instead of pTHBD, driven by the endogenous pig promoter. RESULTS: The promoterless selection cassette permitted efficient enrichment of cells containing correctly inserted transgene. Recombinase treatment of selected cells excised the resistance marker permitting expression of the human transgene by the endogenous pTHBD promoter. Gene regulation was maintained after gene replacement because pig endogenous promoter was kept intact in the correct position. CONCLUSIONS: Cas9 and recombinase technology make orthotopic human for pig gene exchange feasible and pave the way for creation of pigs with human genes that can be expressed in the appropriate tissues preserving gene regulation.

Should a Stoma Be Used After Intestinal Transplant.

As we all acknowledge benefits of ostomies, they can come with significant morbidity, quality of life issues, and major complications, especially during reversal procedures. In recent years, we have started to observe that similar graft and patient survival can be achieved without ostomies in certain cases. This observation and practice adopted in a few large-volume transplant centers opened a new discussion about the necessity of ostomies in intestinal transplantation. There is still more time and randomized studies will be needed to better understand and analyze the risk/benefits of "No-ostomy" approach in intestinal transplantation.

Interval between surgery and neoadjuvant chemoradiation therapy for distal rectal cancer: does delayed surgery have an impact on outcome?

BACKGROUND: The optimal interval between neoadjuvant chemoradiation therapy (CRT) and surgery in the treatment of patients with distal rectal cancer is controversial. The purpose of this study is to evaluate whether this interval has an impact on survival. METHODS AND MATERIALS: Patients who underwent surgery after CRT were retrospectively reviewed. Patients with a sustained complete clinical response (cCR) 1 year after CRT were excluded from this study. Clinical and pathologic characteristics and overall and disease-free survival were compared between patients undergoing surgery 12 weeks or less from CRT and patients undergoing surgery longer than 12 weeks from CRT completion and between patients with a surgery delay caused by a suspected cCR and those with a delay for other reasons. RESULTS: Two hundred fifty patients underwent surgery, and 48.4% had CRT-to-surgery intervals of 12 weeks or less. There were no statistical differences in overall survival (86% vs. 81.6%) or disease-free survival rates (56.5% and 58.9%) between patients according to interval (< or =12 vs. >12 weeks). Patients with intervals of 12 weeks or less had significantly higher rates of Stage III disease (34% vs. 20%; p = 0.009). The delay in surgery was caused by a suspected cCR in 23 patients (interval, 48 +/- 10.3 weeks). Five-year overall and disease-free survival rates for this subset were 84.9% and 51.6%, not significantly different compared with the remaining group (84%; p = 0.96 and 57.8%; p = 0.76, respectively). CONCLUSIONS: Delay in surgery for the evaluation of tumor response after neoadjuvant CRT is safe and does not negatively affect survival. These results support the hypothesis that shorter intervals may interrupt ongoing tumor necrosis.