Project description:ICU acquired weakness (ICUAW) is a complication of critical illness characterized by structural and functional impairment of skeletal muscle that may persist for years after ICU discharge with many survivors developing protracted courses with few regaining functional independence. Elucidating molecular mechanisms underscoring sustained ICUAW is crucial to understanding outcomes linked to different morbidity trajectories as well as for the development of novel therapies. Quadriceps muscle biopsies and functional measures of muscle strength and mass were obtained at 7 days and 6 months post-ICU discharge from a cohort of ICUAW patients. Unsupervised co-expression network analysis of transcriptomic profiles identified discrete modules of co-expressed genes associated with the degree of muscle weakness and atrophy in early and sustained ICUAW. Modules were enriched for genes involved in skeletal muscle regeneration and extracellular matrix deposition. Collagen deposition in persistent ICUAW was confirmed by histochemical stain. Modules were further validated in an independent cohort of critically ill patients with sepsis-induced multi-organ failure and a porcine model of ICUAW, demonstrating disease-associated conservation across species and peripheral muscle type. Our findings provide a pathomolecular basis for sustained ICUAW, implicating aberrant expression of distinct skeletal muscle structural and regenerative genes in early and persistent ICUAW. Total RNA was extracted from approximately 200mg of quadriceps muscle (vastus lateralis) tissue in patients with Intensive care unit (ICU) acquired weakness (ICUAW) at day 7 post-ICU discharge (D7) and month 6 post-ICU discharge (M6), and from healthy controls (C)
Project description:Background: The aim of this study is to improve our understanding of the mechanisms underlying the sparing of masticatory muscles in ICU patients with acute quadriplegic myopathy (AQM) by using a unique porcine ICU model, i.e., 5-day longitudinal experiments where animals are sedated, mechanically ventilated and exposed to factors triggering AQM, such as muscle unloading, endotoxin-induced sepsis, and systemic exposure to CS and NMBA. Results: An increased expression was notably observed in atrogin-1, cathepsins, FoxO1a, runx1 and heat-shock proteins genes. A decreased expression in some sarcomeric proteins and myostatin genes was also noticed. Hence, modifications in heat-shock proteins and myostatin genes are in sharp contrast to alterations in the limb muscles and it is postulated that elevated heat-shock proteins and decreased myostatin genes play a protective role in the masticatory muscle in ICU patients with AQM. Conclusions: We have observed a general down-regulation of muscle proteins and myostatin. Genes involved in the UPS system, cathepsins, RUNX1, TBX1, TIMP2 and transcripts of heat-shock proteins were up-regulated. However, we have neither observed a decrease in fiber CSA or force generation, suggesting that the expected atrophic changes have been countered by a protective mechanism and myostatin downregulation. Five female domestic piglets were treated with non-depolarizing neuromuscular blocking agents (NMBA), corticosteroids(CS) and sepsis. Five female piglets were untreated.
Project description:ICU acquired weakness (ICUAW) is a complication of critical illness characterized by structural and functional impairment of skeletal muscle that may persist for years after ICU discharge with many survivors developing protracted courses with few regaining functional independence. Elucidating molecular mechanisms underscoring sustained ICUAW is crucial to understanding outcomes linked to different morbidity trajectories as well as for the development of novel therapies. Quadriceps muscle biopsies and functional measures of muscle strength and mass were obtained at 7 days and 6 months post-ICU discharge from a cohort of ICUAW patients. Unsupervised co-expression network analysis of transcriptomic profiles identified discrete modules of co-expressed genes associated with the degree of muscle weakness and atrophy in early and sustained ICUAW. Modules were enriched for genes involved in skeletal muscle regeneration and extracellular matrix deposition. Collagen deposition in persistent ICUAW was confirmed by histochemical stain. Modules were further validated in an independent cohort of critically ill patients with sepsis-induced multi-organ failure and a porcine model of ICUAW, demonstrating disease-associated conservation across species and peripheral muscle type. Our findings provide a pathomolecular basis for sustained ICUAW, implicating aberrant expression of distinct skeletal muscle structural and regenerative genes in early and persistent ICUAW.
Project description:Background: The aim of this study is to improve our understanding of the mechanisms underlying the sparing of masticatory muscles relative to limb muscles in ICU patients with acute quadriplegic myopathy (AQM) by using a unique porcine ICU model, i.e., 5-day longitudinal experiments where animals are sedated, mechanically ventilated and exposed to factors triggering AQM, such as muscle unloading, endotoxin-induced sepsis, and systemic exposure to CS and NMBA. Results: An altered expression was notably observed in heat-shock proteins genes, sarcomeric proteins and myostatin genes were noticed. Hence, modifications in heat-shock proteins, sarcomeric proteins and myostatin genes are in sharp contrast to alterations in the limb muscles and it is postulated that elevated heat-shock proteins and decreased sarcomeric protein and myostatin genes play a protective role in the masticatory muscle relative to limb muscle in ICU patients with AQM. Conclusions: This intervention had no significant effect on masseter muscle fiber size or force-generation capacity. This is in sharp contrast to the dramatic decrease observed in specific force in limb muscle fibers from the same animals. However, significant differences were observed between the craniofacial and the limb muscle with a masseter muscle specific regulation of i) transcriptional and growth factors like RUNX1, FOXO1A, TBX1, PGC1-β and myostatin, ii) several heat shock protein genes like HSP 90, HSP 105/110 and αB-crystallin, iii) a matrix metalloproteinase inhibitor (TIMP2) and iv) oxidative stress responsive elements such as SRXN1 and SOD2. These muscle-type specific differences, the alterations in heat shock protein, sarcomeric protein and myostatin genes are forwarded as important factors underlying the sparing of masticatory muscles compared with limb muscles in critically ill ICU patients with Acute Quadriplegic Myopathy. Keywords: Treatment, immobilization, muscle function.
Project description:Background : The aim of this study is to improve our understanding of the mechanisms underlying the role of sepsis in the limb muscles of ICU patients with acute quadriplegic myopathy (AQM) by using a unique porcine ICU model, i.e., 5-day longitudinal experiments where animals are sedated, mechanically ventilated and exposed to factor triggering AQM that is endotoxin-induced sepsis. Results : An increased expression of genes involved in chemokine activity and transcriptional regulation. A decreased expression in genes regulating heat shock proteins, cytoskeletal & sarcomeric and oxidative stress response were also apparent. Therefore, it appears that sepsis has an additive deleterious role in acute quadriplegic myopathy. Sepsis-induced molecular mechanisms involving chemokine/innate immunity and heat shock proteins are forwarded as probable mechanisms underlying the decreased force generating capacity. Conclusions : This sepsis had significant effect on biceps femoris muscle force-generation capacity but not on fiber size. However, significant differences were observed between the MV and MV+SEP in the transcriptional regulation of an increased expression of genes involved in chemokine activity genes like MCP-1 and transcriptional regulation genes like JUNB, STAT3 and BHLHB2. A decreased expression in genes regulating heat shock proteins like HSP 90, HSP 70 and αB-crystallin, cytoskeletal & sarcomeric like MAP1A, MyBP-C1 and MYH7 and oxidative stress response like SRXN1 and SOD2 were also apparent. Therefore, it appears that sepsis has an additive negative role in acute quadriplegic myopathy.