Feasibility and scalability of spring parameters in distraction enterogenesis in a murine model

Background: Distraction enterogenesis has been investigated as a novel treatment for short bowel syndrome (SBS). With variable intestinal sizes, it is critical to determine safe, translatable spring characteristics in differently sized animal models before clinical use. Nitinol springs have been shown to lengthen intestines in rats and pigs. Here, we show spring- mediated intestinal lengthening is scalable and feasible in a murine model. Materials and methods: A 10-mm nitinol spring was compressed to 3 mm and placed in a 5mm intestinal segment isolated from continuity in mice. A noncompressed spring placed in a similar fashion served as a control. Spring parameters were proportionally extrapolated from previous spring parameters to accommodate the smaller size of murine intestines. After 2- 3 wk, the intestinal segments were examined for size and histology. Results: Experimental group with spring constants, k = 0.2-1.4 N/ m, showed intestinal lengthening from 5.0 +/- 0.6 mm to 9.5 +/- 0.8 mm ( P < 0.0001), whereas control segments lengthened from 5.3 +/- 0.5 mm to 6.4 +/- 1.0 mm ( P < 0.02). Diameter increased similarly in both groups. Isolated segment perforation was noted when k >= 0.8 N/m. Histologically, lengthened segments had increased muscularis thickness and crypt depth in comparison to normal intestine. Conclusions: Nitinol springs with k <= 0.4 N/m can safely yield nearly 2-fold distraction enterogenesis in length and diameter in a scalable mouse model. Not only does this study derive the safe ranges and translatable spring characteristics in a scalable murine model for patients with short bowel syndrome, it also demonstrates the feasibility of springmediated intestinal lengthening in a mouse, which can be used to study underlying mechanisms in the future. (C) 2017 Elsevier Inc. All rights reserved.