Biomechanical properties of the stomach: A comprehensive comparative analysis of human and porcine gastric tissue.

BACKGROUND: Stomach-related disorders impose medical challenges and are associated with significant social and economic costs. The field of biomechanics is promising for understanding tissue behavior and for development of medical treatments and surgical interventions. In gastroenterology, animal models are often used when studies on humans are not possible. Often large animal models with similar anatomical characteristics (size and shape) are preferred. However, it is uncertain if stomachs from humans and large animals have similar mechanical properties. The aim of the present study is to characterize and compare hyper- and viscoelastic properties of porcine and human gastric tissue using tension and radial compression tests. METHODS: Hyperelastic and viscoelastic properties were quantified from quasi-static ramp tests and stress relaxation tests. Tension in two directions and radial compression experiments were done on intact stomach wall samples as well as on separated mucosa and muscularis layer samples from porcine and human fundus, corpus and antrum. RESULTS AND CONCLUSIONS: Similar hyper- and viscoelastic constitutive models can be used to describe porcine and human gastric tissue. In total, 19 constitutive parameters were compared and results showed significant variations between species. For example, for intact circumferential samples from antrum, the stiffness (a) and relaxation (τ1) were greater for human samples than for porcine samples (p < 0.0001). The constitutive parameters were condition-, region- and layer-dependent and no distinct pattern hereof between species was found. This indicates that different parameters must be used to describe the specific situation. The present work provides insight into porcine and human gastric radial compressive and tensile hyper- and viscoelastic properties, strengthening the inter-species relation of the biomechanical properties. Constitutive relations were established that may aid development and translation of diagnostic or therapeutic devices with computational models.

Electrospun nanofiber mesh with fibroblast growth factor and stem cells for pelvic floor repair.

Surgical outcome following pelvic organ prolapse (POP) repair needs improvement. We suggest a new approach based on a tissue-engineering strategy. In vivo, the regenerative potential of an electrospun biodegradable polycaprolactone (PCL) mesh was studied. Six different biodegradable PCL meshes were evaluated in a full-thickness abdominal wall defect model in 84 rats. The rats were assigned into three groups: (1) hollow fiber PCL meshes delivering two dosages of basic fibroblast growth factor (bFGF), (2) solid fiber PCL meshes with and without bFGF, and (3) solid fiber PCL meshes delivering connective tissue growth factor (CTGF) and rat mesenchymal stem cells (rMSC). After 8 and 24 weeks, we performed a histological evaluation, quantitative analysis of protein content, and the gene expression of collagen-I and collagen-III, and an assessment of the biomechanical properties of the explanted meshes. Multiple complications were observed except from the solid PCL-CTGF mesh delivering rMSC. Hollow PCL meshes were completely degraded after 24 weeks resulting in herniation of the mesh area, whereas the solid fiber meshes were intact and provided biomechanical reinforcement to the weakened abdominal wall. The solid PCL-CTGF mesh delivering rMSC demonstrated improved biomechanical properties after 8 and 24 weeks compared to muscle fascia. These meshes enhanced biomechanical and biochemical properties, demonstrating a great potential of combining tissue engineering with stem cells as a new therapeutic strategy for POP repair. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:48-55, 2020.

Electrospun biodegradable microfibers induce new collagen formation in a rat abdominal wall defect model: A possible treatment for pelvic floor repair?

Half of the female population over age 50 years will experience pelvic organ prolapse. We suggest a new approach based on tissue engineering principles to functionally reconstruct the anatomical structures of the pelvic floor. The aim of this study is to investigate the mechanical performance and effect on collagen and elastin production of a degradable mesh releasing basic fibroblast growth factor (bFGF). Implantation of biodegradable mesh with or without bFGF in their core has been conducted in 40 rats in an abdominal wall defect model. Samples were explanted after 4, 8, and 24 weeks, and tested for mechanical properties and the composition of connective tissue. The study showed an increase in mRNA expression for collagen-I (p = 0.0060) and collagen-III (p = 0.0086) in the 4 weeks group with bFGF. The difference was equalized at 8 and 24 weeks. No difference was found at any time for protein amount for collagen-I, collagen-III, and fibronectin. The amount of collagen decreased from 4 to 24 weeks but the fraction of collagen increased. The maximal load of the newly formed tissue showed no effect of bFGF at any time. Exclusively, histology showed a limited ingrowth of collagen fibers after 4 weeks with bFGF but signs of elastin fibers were seen at 24 weeks. The investigation showed that a biodegradable mesh promotes tissue formation with a promising strength. The mesh with bFGF did not represent any advantage on either long or short term in comparison to the mesh without bFGF. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 680-688, 2018.