Active, three-dimensional stomach deformation - experiment and simulation

Abstract

The stomach is a central organ of vertebrates and, due to its extreme deformations, places special demands on the stomach tissue and especially on the active smooth muscle. Although a variety of dysfunctions and associated tissue changes are known, mechanical studies are scarce compared to other organs.

Thus, the main objective of the proposal is to develop and validate a porcine stomach model. In the first phase of the project, it was possible to collect a high-resolution data set on the local and layer-specific stomach structure and the mechanical tissue properties, on the basis of which an electro-chemomechanical stomach model was developed.

For the completion of the model development and in particular the model validation, various experimental and model-based tasks are still necessary, which arose in the first project phase and are to be worked on in the context of the present follow-up application. Unexpected problems arose, e.g., in the stimulation of the antrum, which is interesting on the one hand, as this indicates significant electro-chemomechanical differences between the gastric regions, on the other hand, this led to delays in the planned course of the project and makes it necessary to develop other approaches.

Measurements are to be carried out on skinned, isolated smooth muscle fibre bundles of the antrum in order to determine the mechanical properties of the antrum. For a validation of the stomach model on tissue strip level, active biaxial experiments are to be carried out for the first time.

Furthermore, realistic model predictions require the determination of the microstructure and composition of these tissue strips by means of immunohistological investigations. In addition, the active experiments on the whole stomach necessary for validating the whole stomach model will be carried out by measuring the whole stomach deformation and the generated internal pressures.

The pronounced history dependence (force depression, force enhancement) of muscle force determined in the first project phase requires a model extension to predict realistic internal stomach pressures and deformations.

In the final project phase, a step-by-step model validation is to take place on the measured three-dimensional deformations and forces/pressures, first at tissue strip level and finally at whole organ level.

The developed stomach model represents a substitute and complementary method to animal experiments and, based on the similarity of the human and pig stomach, to human studies. It can thus contribute to the reduction of animal experiments and to a better understanding of stomach function in the future.