In this interview with MEDICA-tradefair.com, Prof. Cornelia Blume talks about the right formula to cultivate vascular grafts in a rotating bioreactor, describes the measurement technique this requires and explains the role stem cells play in this process.
Prof. Blume, along with your team you have developed a bioreactor to cultivate vascular grafts. What does this device look like?
Prof. Cornelia Blume: The centerpiece of the reactor is a small tube, in which a one by eight centimeter sized vessel can be cultivated. The housing rotates to ensure an even distribution and growth of cells. Tubing and pump systems are connected to the housing, allowing us to simulate the body's cardiovascular blood flow within the vessel. We can run a second circuit outside the vascular graft, which simulates the tissue pressure in the human body.
So the reactor simulates different conditions found inside the human body. Which of these is particularly important to successfully engineer a vascular graft?
Blume: We start with a fetal circulatory system, where the vasculogenesis takes place at a blood pressure reading between 40-60 mm Hg. This is our estimation for the initial phase of the cultivation process. In the course of the cultivation process, we also want to test higher blood pressure values to make sure the implant can withstand these levels.
In a second step, we determine the so-called shear stress based on the blood pressure readings. This lets us determine the effect the existing pressure has on the cells. Many studies have shown that cells only combine to form tissue under a certain amount of shear stress.
Other parameters are also important for the cultivation process. We have integrated different sensor systems into the reactor to monitor them. The wireless control of these sensors ensures that we do not have to open the reactor during the cultivation process. This would disrupt the process. Among other things, we monitor the nutrient content based on glucose and lactate, the pH value and oxygen tension within the growing vessel. Lower oxygen tension benefits certain cells like the stem cells we work with and that come from a hypoxic niche of the body. We can also check the growth of the vessel by using ultrasound.