Porcine Stomach Smooth Muscle Force Depends on History-Effects

Abstract

The stomach serves as food reservoir, mixing organ and absorption area for certain substances, while continually varying its position and size. Large dimensional changes during ingestion and gastric emptying of the stomach are associated with large changes in smooth muscle length. These length changes might induce history-effects, namely force depression (FD) following active muscle shortening and force enhancement (FE) following active muscle stretch. Both effects have impact on the force generating capacity of the stomach, and thus functional relevance. However, less is known about history-effects and active smooth muscle properties of stomach smooth muscle. Thus, the aim of this study was to investigate biomechanical muscle properties as force-length and force-velocity relations (FVR) of porcine stomach smooth muscle strips, extended by the analysis of history-effects on smooth muscle force. Therefore, in total n = 54 tissue strips were dissected in longitudinal direction from the ventral fundus of porcine stomachs. Different isometric, isotonic, and isokinetic contraction protocols were performed during electrical muscle stimulation. Cross-sectional areas (CSA) of smooth muscles were determined from cryo-histological sections stained with Picrosirius Red. Results revealed that maximum smooth muscle tension was 10.4 ± 2.6 N/cm2. Maximum shortening velocity (Vmax) and curvature factor (curv) of the FVR were 0.04 ± 0.01 [optimum muscle length/s] and 0.36 ± 0.15, respectively. The findings of the present study demonstrated significant (P < 0.05) FD [up to 32% maximum muscle force (Fim)] and FE (up to 16% Fim) of gastric muscle tissue, respectively. The FE- and FD-values increased with increasing ramp amplitude. This outstanding muscle behavior is not accounted for in existing models so far and strongly supports the idea of a holistic reflection of distinct stomach structure and function. For the first time this study provides a comprehensive set of stomach smooth muscle parameters including classic biomechanical muscle properties and history-dependent effects, offering the possibility for the development and validation of computational stomach models. Furthermore, this data set facilitates novel insights in gastric motility and contraction behavior based on the re-evaluation of existing contractile mechanisms. That will likely help to understand physiological functions or dysfunctions in terms of gastric accommodation and emptying.

Computational model of gastric motility with active‐strain electromechanics

“…Finally, also a more realistic mechanical model of the gastric tissue should be employed. It is well‐known that the gastric tissue exhibits inhomogeneous and in general also anisotropic mechanical properties, which may also strongly depend on the age of an individual . Exploring the precise effect of the mechanical properties on the electro‐mechanical coupling might be a key to better understand the origin of certain gastric pathologies.…”

Mechanics of the stomach: A review of an emerging field of biomechanics

“…There have been a few papers on the constitutive behavior of the esophagus, [53][54][55][56][57] small intestine, [58][59][60][61][62][63][64] and large intestine, [58,61,[65][66][67][68][69][70][71] and around 20 on the mechanical properties of the gastric wall. [61,[72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89] These revealed that the constitutive properties and thickness of the different layers of the gastric wall differ significantly between different regions of the stomach, corresponding to their respective physiological functions. Most papers on gastric tissue mechanics report results of uniaxial tests only, [61,[72][73][74][75][76]79,…”

“…There have been a few papers on the constitutive behavior of the esophagus, small intestine, and large intestine, and around 20 on the mechanical properties of the gastric wall. These revealed that the constitutive properties and thickness of the different layers of the gastric wall differ significantly between different regions of the stomach, corresponding to their respective physiological functions. Most papers on gastric tissue mechanics report results of uniaxial tests only, which are insufficient to characterize the biaxial deformation (in both circumferential and longitudinal direction) observed in vivo, noting the in general significant anisotropy of gastric tissue.…”

“…Another recent study investigated extensively the active mechanical properties of porcine fundic smooth muscle tissue. [] The study quantified the force‐length and force‐velocity relations of fundic smooth muscle strips. Additionally, the dependency of force generation on preceding length changes, so called history effects, was examined.…”

Numerical analyses of the interrelation between extracellular smooth muscle orientation and intracellular filament overlap in the human abdominal aorta

“…Furthermore, contraction tests on mesenteric arteries of rats, human tracheal tissues and smooth muscles of porcine stomach show a relatively similar ratio between the active and passive stress at optimal muscle length. [8,57,61] Therefore, it is assumed that the ratio between the active stress at optimal muscle length and the corresponding passive stress is the same for both pig common carotid artery and human abdominal aorta. Hence, the experimental length-tension behavior is scaled in the vertical direction (along the stress axis) accordingly, see Figure A1(b).…”