This study focuses on mechanical ventilation used in intensive care unit to supplement ventilatory function in patients. Indeed, mechanical ventilation can "paradoxically" be at the origin of complications that can be life-threatening in patients. Indeed, mechanical ventilation buy unloading respiratory muscles, mays induce atrophy of these muscles and an alteration of their contractile properties induced by a disturbance of the redox status and tissue regeneration. This muscular pathology is called ventilation-induced diaphragmatic dysfunction (DDIV).
In animal models, antioxidant molecules showed a beneficial effect to limit this pathology, highlighting the importance of oxidative stress in the pathophysiology of DDIV. Among the different molecules tested, SS-31, which is a chelator of free radicals specific to the mitochondria, has shown its effectiveness in preventing VIDD in an animal model. However, physiopathological data in Human are still needed to propose this molecule in a therapeutic trial. Indeed, the maintenance of muscle mass and therefore tissue regeneration depends on the ability of muscle stem cells (MuSC) or satellite cells to activate and differentiate. Muscular homeostasis depends also on the capacity of these cells to activate quiescence genes in order to maintain a pool of quiescent cells which keep capacity for self-renewal. In the context of a pathological microenvironment favoring excessive activation of satellite cells, such as during mechanical ventilation, the investigators can postulate that this will lead to a loss of the pool of quiescent cells, thus inducing a loss of homeostasis of the muscle tissue responsible for long-term atrophy. Recent studies on mice, have shown a higher potential for these diaphragmatic quiescent cells to be activated and participating in the renewal of damaged muscle fibers in comparison to peripheral muscles. This specificity of early activation of diaphragmatic satellite cells could weaken them against a pathological microenvironment induced by mechanical ventilation, altering their regenerative capacity. But no data currently exists in humans.
The investigators therefore want, in this study, to assess the diaphragm specificity of the physiopathological mechanisms involved in VIDD, by a comparative study in the same subject of the biological function of satellite stem cells originating from the quadriceps muscle and the diaphragm. This study is complementary to the BOTAN project validated by the IRB of Montpellier (IRB Accreditation number: 198711), on 24/11/2021 under number 2021\_IRB-MTP\_08-37, allowing the collection of diaphragmatic satellite cells from the care. In fact, in subjects included in the BOTAN study, the investigators will perform, during the same surgical intervention, allowing access to a diaphragmatic biopsy, a biopsy of the quadriceps in order to evaluate in parallel the regenerative capacities of the stem cells of the quadriceps, compared to that of the diaphragm in the same patient.
Our hypothesis is that the mechanical and oxidative stress imposed by mechanical ventilation will lead to impaired activation of satellite cells, depletion of the pool of quiescent satellite cells. The consequence will be an inability of muscular tissue regeneration and ultimately atrophy associated diaphragm contractile dysfunction. Thus by comparing the biological function of satellite cells and their regenerative capacities coming from diaphragm and quadriceps of the same patient, the investigators will be able to answer the question of whether diaphragmatic stem cells are more active in their renewal compared to those of the quadriceps and therefore more likely susceptible to lose their pool of quiescent cells, at the basis of muscle atrophy and VIDD.
This work would allow us in the future to identify new therapeutic targets aimed at limiting the early activation of satellite cells at rest, harmful for the maintenance of a pool of quiescent satellite cells during mechanical ventilation, in order to limit the impact of the VIDD.
Moreover, the BOTAN study will allow us to propose a in vitro model of VIDD from cultures of human diaphragmatic stem cells, which will be subjected to mechanical stress similar to those encountered in ventilated patients. Thanks to the present study, which will allow us to assess the specificity of early activation of the quadriceps satellite cells compared to that of the diaphragm in the same individual, the investigators will also be able to validate a in vitro tool allowing the screening of bioactive molecules of interest to limit VIDD, without the need for a diaphragm biopsy but only a quadriceps biopsy, which is much more simple and less invasive. Thus, this study is the first study in humans to propose this type of comparative evaluation, which will make it possible to propose new minimally invasive tools in the evaluation and optimization of pharmacological treatments to limit the impact of VIDD.
