Esophagus stretch tests: Biomechanics for tissue engineering and possible implications on the outcome of esophageal atre
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ORIGINAL ARTICLE
Esophagus stretch tests: Biomechanics for tissue engineering and possible implications on the outcome of esophageal atresia repairs performed under excessive tension Amulya K. Saxena1 · Ede Biro2 · Gerhard Sommer3 · Gerhard A. Holzapfel3,4 Received: 22 May 2020 / Accepted: 13 August 2020 © The Japan Esophageal Society 2020
Abstract Background Esophageal biomechanical studies are important to understand structural changes resulting from stretches during repair of esophageal atresias as well as to obtain values to compare with the biomechanics of tissue-engineered esophagus in the future. This study aimed to investigate light microscopic changes after uniaxial stretching of the ovine esophagus. Methods In vitro uniaxial stretching was performed on esophagi (n = 20) of 1-month-old lambs within 4–6 h post-mortem. Esophagi were divided into 5 groups: control and stretched (1.1, 1.2, 1.3 and 1.4). Force and lengthening were measured with 5 cycles performed on every specimen using a PBS organ bath at 37 °C. Histological studies were performed on the 5 groups. Results Low forces of ~ 2 N (N) were sufficient for a 1.2–1.25 stretch in the 1st cycle, whereas a three times higher force (~ 6 N) was needed for a stretch of 1.3. In the 2nd to 5th cycle, the tissue weakened and a force of ~ 3 N was sufficient for a stretch of 1.3. Histologically, in the 1.3–1.4 stretch groups, rupture of muscle fibers and capillaries were observed, respectively. Changes in mucosa and collagen fibers could not be observed. Conclusions These results offer norm values from the native esophagus to compare with the biomechanics of future tissueengineered esophagus. Esophageal stretching > 1.3 leads to tears in muscle fibers and to rupture of capillaries. These findings can explain the decrease in microcirculation and scarring in mobilized tissue and possibly offer clues to impaired motility in esophagus atresias repaired under excessive tension. Keywords Ovine esophagus · Biomechanics · Esophageal atresia · Dysmotility · Tissue engineering
Introduction Esophageal atresia is a relatively common congenital malformation occurring in 1:3000–5000 births [1]. Successful repairs of esophageal atresia were initially performed as staged procedures in 1939; with the first successful primary * Amulya K. Saxena [email protected] 1
Department of Pediatric Surgery, Chelsea Children’s Hospital, Chelsea and Westminster Hospital NHS Fdn Trust, Imperial College London, 369 Fulham Road, London SW10 9NH, UK
2
Department of Pediatric Surgery, Medical University of Pecs, Pecs, Hungary
3
Institute of Biomechanics, Graz University of Technology, Graz, Austria
4
Norwegian University of Science and Technology, Trondheim, Norway
repair in 1941 [2]. Improvement in survival increased from approximately 90% by the mid-1980′s [3]. With the increase in survivability and the majority of the esophageal atresia being repaired directly by primary anastomosis; follow-ups as early as the late 1980′s indicated that patients after primary repa
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