The influence of long-term space travels on the musculoskeletal apparatus of astronauts: state of the art and challenges of health monitoring and possible countermeasures

Long-duration space missions pose significant risks to astronaut health, particularly due to the detrimental effects of microgravity on the musculoskeletal system. Extensive literature emphasizes how bone and muscle tissues, essential for structural integrity and mobility, undergo rapid degradation in space environments, leading to critical health challenges. The work conducted in this thesis harnesses the expertise of Politecnico di Torino in biomechanics, in collaboration with Thales Alenia Space, to enhance understanding of bone and muscle deterioration during extended space missions. It builds on prior findings and explores technological strategies to mitigate these effects, focusing on adapting in vitro models based on bioreactors to study musculoskeletal responses in microgravity. The bibliographic research reviewed past studies of space-induced musculoskeletal degradation, highlighting key biological mechanisms and current countermeasures. The analysis highlighted that commonly used techniques, such as resistive exercise, have decreased effectiveness during extended missions, failing to fully prevent muscle atrophy and bone loss. There is therefore a pressing need of improved models, providing a controlled environment for investigating the effects of microgravity conditions, and for testing and refining countermeasures. In this perspective, the centerpiece of this thesis is the BIGMECH bioreactor, a state-of-the-art system developed at Politecnico di Torino, designed to provide a bone-like environment to develop and investigate in vitro biomimetic bone tissue models. BIGMECH bioreactor integrates direct perfusion and intermittent pressure stimulation to mimic bone-like mechanical stimuli, while pulsed electromagnetic fields (PEMF) provide therapeutic effects. Previous experiments have shown the suitability of the bioreactor in maintaining cell viability and enhancing bone regeneration, highlighting its potential for space applications. In this work a real-time pressure monitoring system was implemented. In-house Python software manages data acquisition, control, and visualization. By interfacing pressure sensors and an Analog- to-Digital Converter (ADC) via a BeagleBone Black microcontroller, the system provides real-time data and visualization at a sampling frequency of 1250 Hz. Comparative tests with laboratory DAQ setups confirmed the accuracy of the developed monitoring system in measuring pressure variations in the bioreactor, and demonstrated the bioreactor accuracy in replicating physiological pressures relevant to bone marrow. In collaboration with Thales Alenia Space, a gap analysis for identifying the critical challenges (e.g., miniaturization, space qualification) for adapting the BIGMECH bioreactor to space conditions was performed. Addressing these hurdles will be pivotal in the future for the deployment aboard the International Space Station (ISS) and future extraterrestrial habitats. In conclusion, this study identified key gaps in current countermeasures to musculoskeletal degradation in microgravity and underscores the BIGMECH bioreactor's potential as a key tool for investigating the adverse effects of microgravity on bone tissue. The developed automatic monitoring system represents a crucial first step towards adapting the technology for space applications, enabling the study of therapies aimed at improving astronaut health during long-term missions, with promising implications for treating musculoskeletal diseases on Earth.