Conceptual design of the testing device. In a test chamber, a specimen from a human coronary artery (CA) is stretched in two perpendicular directions. At the same time, a stamp in the form of a stent strut is pressed onto the specimen in the thickness direction. To simulate the blood flow and pressure inside a CA, the test chamber is connected to an artificial heart. In addition, a bioreactor with nutrient solution enables long-term tests over several days. (VE: video extensometer; MCL: mock circulatory loop)

Second harmonic generation (SHG) imaging through the arterial wall (out-of-plane view) perpendicular to the stamp. SHG images show collagen fibers from specimens of a 6 months old porcine descending aorta behaving under different pressures p (MPa) of the stamp with a width of 0.08 mm and a length of 3 mm. The blurred spots under the stamp at the deepest point of the lesion are indicators of the separation of fibers into individual fibrils.

The LAESIO project, on which engineers will be working with the support of medical doctors, biologists and mathematicians, tries to clarify what happens from a biomechanical and structural perspective when stents damage blood vessels and do not treat them. Vascular damage during coronary stent placement (CSI) needs to be reduced as it has been shown to be the strongest stimulus for in-stent restenosis. For this purpose, engineers need precise and verified mathematical material damage models (MDM) that can describe the mechanical behavior of arterial walls during CSI. This MDM can later be used for computer simulations to develop improved stents or new vascular therapies.

LAESIO's central hypothesis states that precise MDM for stent optimization can only be achieved by correlating the load on the artery during CSI with the severity of the resulting vascular damage and cell proliferation.
The overall objective is the development of such an experimentally verified MDM for the mathematical description of so-called damage mechanisms (DM) within the arterial wall on the macro- and micro-levels as well as cell proliferation during the process of CSI.

As a basis for all investigations, the mechanical interaction between stent and blood vessel is simulated during a CSI in an experiment outside the organism. Using histological and 3D imaging methods, the damage to the respective structural components of the artery, such as collagen fibers and muscle cells, is examined. Furthermore, the time- and load-dependent cell proliferation is analyzed. High-resolution microscopes are used here, which enable observations of the arterial wall on a nanoscale. The data obtained are then statistically evaluated and mathematically linked. The resulting equations are able to mathematically describe DMs and cell proliferation during CSI. With the unique MDM, LAESIO provides a powerful tool for stent manufacturers and scientists that makes it possible to estimate the negative effects of stent prototypes using computer simulations. The findings from this project will also improve the understanding of CA in the physiological and pathological state.

Funding: Austrian Science Fund (FWF)