Evaluation of anterior versus posterior component separation for hernia repair in a cadaveric model
SURGICAL ENDOSCOPY AND OTHER INTERVENTIONAL TECHNIQUES
Authors: Majumder, Arnab; Martin-del-Campo, Luis A.; Miller, Heidi J.; Podolsky, Dina; Soltanian, Hooman; Novitsky, Yuri W.
Abstract
Background Component separation remains an integral step during ventral hernia repair. Although a multitude of techniques are described, anterior component separation (ACS) via external oblique release (EOR) and posterior component separation (PCS) via transversus abdominis muscle release (TAR) are commonly utilized. The extent of myofascial medialization after ACS or PCS has not been well elucidated. We conducted a comparative analysis of ACS versus PCS in an established cadaveric model. Methods Fifteen cadavers underwent both ACS via EOR and PCS via TAR. Following midline laparotomy (MLL), baseline myofascial elasticity was measured. Steps for ACS included creation of subcutaneous flaps (SQF), external oblique release (EOR), and retrorectus dissection (RRD). For PCS, steps included retrorectus dissection (RRD), transversus abdominis muscle division (TAD), and retromuscular dissection (RMD). Maximal advancement of anterior rectus fascia (ARF) was measured following application of tension to the fascia as a whole, and separately at upper, middle, and lower segments. Statistical analysis was performed with Mann-Whitney U test. Values are represented as average myofascial medialization in centimeters. Results Following MLL an average of 5.0 +/- 0.9 cm (range 3.4-6.0 cm) of baseline medialization was obtained. Complete ACS provided 8.8 +/- 1.2 cm (range 6.3-10.7 cm) of ARF advancement compared to 10.2 +/- 1.7 cm (range 7.6-12.7 cm) with PCS, p = 0.046. In the upper and mid-abdomen, we noted increased ARF advancement with PCS versus ACS (8.1 +/- 1.4 cm vs. 6.7 +/- 1.2 cm and 11.4 +/- 1.5 vs. 9.6 +/- 1.4 cm, respectively, p = 0.01). Similar levels of ARF advancement were observed in the lower abdomen, 9.1 +/- 1.7 cm versus 8.7 +/- 1.8 cm, p = 0.535. Conclusions Component separation via both anterior and posterior approaches provide substantial myofascial advancement. In our model, we noted statistically greater anterior fascial medialization after PCS versus ACS as a whole, and especially in the upper and mid-abdomen. We advocate PCS as a reliable and possibly superior alternative for linea alba restoration for reconstructive repairs, especially for large defects in the upper and mid-abdomen. Graphic
The potential underlying mechanism of the leukemia caused by MLL-fusion and potential treatments
MOLECULAR CARCINOGENESIS
Authors: Liu, Haolin; Lee, Schuyler; Zhang, Qianqian; Chen, Zhongzhou; Zhang, Gongyi
Abstract
A majority of infant and pediatric leukemias are caused by the mixed-lineage leukemia gene (MLL) fused with a variety of candidates. Several underlying mechanisms have been proposed. One currently popular view is that truncated MLL1 fusion and its associated complex constitutively hijacks super elongation complex, including positive transcription elongation factor b, CDK9, and cyclin T1 complex and DOT1L, to enhance the expression of transcription factors that maintain or restore stemness of leukocytes, as well as prevent the differentiation of hematopoietic progenitor cells. An alternative emerging view proposes that MLL1-fusion promotes the recruitment of TATA binding protein and RNA polymerase II (Pol II) initiation complex, so as to increase the expression levels of target genes. The fundamental mechanism of both theories are gain of function for truncated MLL1 fusions, either through Pol II elongation or initiation. Our recent progress in transcription regulation of paused Pol II through JMJD5, JMJD6, and JMJD7, combined with the repressive role of H3K4me3 revealed by others, prompted us to introduce a contrarian hypothesis: the failure to shut down transcribing units by MLL-fusions triggers the transformation: loss of function of truncated MLL1 fusions coupled with the loss of conversion of H3K4me1 to H3K4me3, leading to the constitutive expression of transcription factors that are in charge of maintenance of hematopoietic progenitor cells, may trigger the transformation of normal cells into cancer cells. Following this track, a potential treatment to eliminate these fusion proteins, which may ultimately cure the disease, is proposed.