The MTB project (for Mice Telemetry on Bion) aims to study hemodynamics on mice, using onboard telemetry equipment and transmitter implants, during a 30-day spaceflight aboard the Russian automated bio-satellite Bion-M No. 1.
For many years, CNES has been taking part in this type of experiments, through its partnership with the Russian Institute for Biomedical Problems (IBMP), carried out on humans and animals alike, including experiments aboard bio-satellites.
Hemodynamics have always been subject to close attention, but unfortunately, no continuous monitoring experiment (blood pressure and heart rate) has been conducted during a space flight so far.
That is why CNES suggested including a dynamic study of central cardiovascular parameters on mice in the Russian Bion-M No. 1 biosatellite’s programme. These parameters will be monitored using onboard telemetry equipment and transmitter implants.
If successful, this demonstration of “mobile” monitoring of the cardiovascular system via telemetry would be a world first and open a vast area of space applications.
The hemodynamic parameters will also be monitored once the subjects are back on the ground, in resting and test conditions, while they readapt to normal gravity.
The minimum number of animals required for this experiment is 5 mice.
The MTB equipment has continuous acquisition, transmission and recording abilities for the 5 mice’s blood pressure as well as the barometric pressure inside their contention cages MLG-01-01.
The MTB equipment comprises:
- 5 sensor implants, one in each mouse
- 10 command receiver antennas (2 on each of the 5 contention cages housing the animals)
- 5 receivers (one in each cage)
- 1 recording device to record the mice’s blood pressure and the barometric pressure in each cage
- connection cables
- a set of MTB monitoring and test equipment (ETC MTB).
The main focus of this mission is to monitor continuously the mice’s blood pressure and heart rate, calculated from the blood pressure curve. This monitoring begins before the flight and continues on after the subjects have come back to the ground, including the biosatellite search and retrieval and the animals’ transportation, when they are readapting to normal gravity.
The other significant aspect of this experiment is the opportunity to carry out specific studies of microgravity without being affected by the usual countermeasures used by astronauts. The data concerning cardiovascular deconditioning are linked to animals’ general deconditioning and thus interests every scientist involved in the Bion project. The experiment will generate valuable data on the cardiovascular reaction to different phases during flight, not only in microgravity but also in “hypergravity” during spacecraft launch and landing. The data collected from these mice will help evaluate the specific effects microgravity can have and will be crucial to interpreting data collected by other scientific teams.
The partners agree to conduct the experiments according to the following timetable.
The plan is to use between 30 and 40 mice, weighing at least 20 grammes, and at least 4 months old. Age and weight selection criteria were based on the minimum size a mouse can be to be implanted with a sensor, and on the fact that at this age, the animal’s growth slows down and its physiology stabilises.
Implants will be given to at least 10 animals; the catheter used to record blood pressure will be implanted in the aortic arch through the carotid artery. The recording unit will store the data so as to make both the blood pressure curve and the beat-by-beat data available for analysis (PAS, PAD, PAM, FC).
Functional tests are non-invasive and aim to evaluate cardiovascular deconditioning and the animal’s general condition. The tests will take place before and after the flight (1rst and 3rd days).
Hemodynamic parameters will be recorded during a physical exercise (treadmill). To evaluate the cardiovascular response to an emotional state and to estimate the animal’s general activity and anxiety levels, it will be subjected to the “hole-board” and the “elevated plus maze” tests. The first will be carried out in a comfortable setting (red lighting) whereas the second will be done in moderately stressful conditions (bright lighting).
During the 3rd day of testing, they will be replaced by similar tests (the “open field” and the “day/night chamber” tests) to prevent the animals from getting used to testing conditions.
In order to evaluate motor and vestibular functions, a “Rotarod” test will also be performed, as well as a grip test to measure the animals’ maximum voluntary forepaws grip strength. Other neurological tests are also planned, as well as estimating different behavioural responses (turnaround response, leg bearing and flexion, cornea response, etc.).
The animals will then be implanted with a catheter used for intravenous injections. Two days after this procedure, if possible, physiological tests will be carried out including, on conscious subjects, a baroreflex test, an H-reflex test, a muscle strength assessment, and a blood flow evaluation using microspheres.