Balloon expansion of the pectoralis major muscle flap in sternoplasty: a biomechanical and histologic study in a rat model.

The pectoralis major advancement flap is currently the most popular technique for reconstruction of the anterior chest in patients with sternotomy wounds. Recently, the SpaceMaker balloon was introduced for rapid expansion of the pectoralis major muscle intraoperatively. The aim of the present study was to investigate the biomechanical and histologic effects of this expansion technique in a rat model. The upper 2 cm of the sternum was resected in 54 male rats. Reconstruction with balloon-assisted pectoralis muscle expansion was performed in 24 rats (study group). Another 24 rats underwent reconstruction with simple muscle advancement without expansion. Submuscular insertion of a catheter for expansion, without inflation, was performed in the remaining six rats (sham group). Rats were killed either immediately or 2 to 4 weeks after surgery. Thirty-eight rats, including 16 after reconstruction with expansion, 16 after reconstruction without expansion, and six in the sham group, were killed immediately after surgery. Sixteen rats were killed 2 to 4 weeks after surgery, eight rats for each reconstruction technique. Before the animals were killed, the biomechanical properties of the muscles were tested with weights to calculate stiffness (in newtons per meter) and compliance gain (in percent). After the animals were killed, biopsy specimens were obtained for histologic analysis. Results indicated significantly lower muscle stiffness in the study group compared with the others immediately after surgery (p = 0.0000), although the difference failed to achieve statistical significance 2 to 4 weeks later (p = 0.76). In the study group, the compliance gain was 74.4 percent immediately after surgery but only 3.4 percent 2 weeks to 1 month postoperatively. Histologic examinations in all groups immediately and 2 to 4 weeks after surgery revealed regular muscle striation with no signs of inflammation. The elastic stiffness of the rat pectoralis major muscle is significantly reduced following rapid intraoperative expansion and returns to normal 2 to 4 weeks later.

Tumor microRNA-29a expression and the risk of recurrence in stage II colon cancer.

There is emerging evidence for the prognostic role of various microRNA (miRNA) molecules in colon cancer. The aim of this study was therefore to compare the miRNA profiles in the primary tumor of patients with recurrent and non-recurrent colon cancer. The study population included 110 patients, 51 (46%) with stage I and 59 (54%) with stage II disease, who underwent curative colectomies between 1995 and 2005 without adjuvant therapy and for whom reliable miRNA expression data were available. RNA was extracted from formalin-fixed paraffin-embedded (FFPE) tumor samples. Initial profiling, using microarrays, was done in order to identify potential biomarkers of recurrence. The miRNA expression was later verified by quantitative real-time polymerase chain reaction (qRT-PCR). Findings were compared between patients who had a recurrence within 36 months of surgery (bad prognosis group, n=23, 21%) and those who did not (good prognosis group, n=87, 79%) in the entire group and within each stage. The results showed that in stage I, none of the 903 miRNAs tested showed differential expression between patients with good prognosis compared with those with poor prognosis. In contrast, in stage II, one miRNA, miR-29a, showed a clear differential expression between the groups (p=0.028). High expression of miR-29a was associated with a longer disease-free survival (DFS), on both univariate and multivariate analyses. Using miR-29a, the positive predictive value for non-recurrence was 94% (2 recurrences among 31 patients). The differential expression of miR-29a was verified by qRT-PCR, showing a similar impact of this miR on DFS. In conclusion, this study demonstrated a significant impact of miR-29a on the risk of recurrence in patients with stage II but not in patients with stage I colon cancer. Based on these results, a validation study is planned.