Optimization of differential filtration-based mitochondrial isolation for mitochondrial transplant to cerebral organoids

Hypotonic Swelling Method for the Isolation of Pure Mitochondria From Primary Human Skeletal Myoblasts for Proteomic Studies

Mitochondria play a fundamental role in energy metabolism, particularly in high-energy-demand tissues such as skeletal muscle. Understanding the proteomic composition of mitochondria in these cells is crucial for elucidating the mechanisms underlying muscle physiology and pathology. However, effective isolation of mitochondria from primary human skeletal muscle cells has been challenging due to the complex cellular architecture and the propensity for contamination with other organelles. Here, we compared four different methods to isolate mitochondria from primary human skeletal myoblasts regarding total protein yield, mitochondrial enrichment capacity and purity of the isolated fraction. We presented a modified method that combines differential centrifugation with a hypotonic swelling step and a subsequent purification process to minimise cellular contamination. We validated our method by demonstrating its ability to obtain highly pure mitochondrial fractions, as confirmed by Western Blot with mitochondrial, cytosolic and nuclear markers. We demonstrated that proteomic analysis can be performed with isolated mitochondria. Our approach provides a valuable tool for investigating mitochondrial dynamics, biogenesis and function in the context of skeletal muscle biology in health and disease. This methodological advancement opens new avenues for mitochondrial research and its implications in myopathies, sarcopenia, cachexia and metabolic disorders.

Effects of Melatonin Administration on Physical Performance and Biochemical Responses Following Exhaustive Treadmill Exercise

Exercise, despite being a beneficial activity for health, can also be a source of oxidative imbalance, which can lead to a decrease in performance. Furthermore, melatonin is an endogenous molecule that may counteract exercise-induced oxidative stress. The aim of this study was to evaluate the potential ergogenic and antioxidant capacity of melatonin administered for a maximal effort test. A total of 30 rats were divided into three groups-control, exercise, and exercise + melatonin (intraperitoneal administration of 10 mg/kg)-to assess the effects of an exhaustive incremental protocol in the two exercise groups (with and without melatonin) on the treadmill-running performance (final speed reached), lipid and protein oxidation markers (malondialdehyde + 4-hidroxyalkenals and carbonyl content, respectively), and cellular and mitochondrial membranes' fluidity in skeletal muscle, brain, and liver tissues. Our results show an ergogenic effect of melatonin (31 ± 4 vs. 36 ± 4 cm/s), which may be due to its antioxidant properties being significantly stronger than its protective effect when performing increasing exercise on a treadmill until exhaustion. Melatonin reverted the membrane rigidity in the brain caused by exercise (with no effect on muscle or liver), prevented lipid oxidation in muscle, and prevented lipid and protein oxidation in the liver. Differences between tissues' responses to exercise and melatonin need to be investigated in the future to elucidate other possible mechanisms that explain melatonin's ergogenic effect.

Compartmental Differences in the Retinal Ganglion Cell Mitochondrial Proteome

Among neurons, retinal ganglion cells (RGCs) are uniquely sensitive to mitochondrial dysfunction. The RGC is highly polarized, with a somatodendritic compartment in the inner retina and an axonal compartment projecting to targets in the brain. The drastically dissimilar functions of these compartments implies that mitochondria face different bioenergetic and other physiological demands. We hypothesized that compartmental differences in mitochondrial biology would be reflected by disparities in mitochondrial protein composition. Here, we describe a protocol to isolate intact mitochondria separately from mouse RGC somatodendritic and axonal compartments by immunoprecipitating labeled mitochondria from RGC MitoTag mice. Using mass spectrometry, 471 and 357 proteins were identified in RGC somatodendritic and axonal mitochondrial immunoprecipitates, respectively. We identified 10 mitochondrial proteins exclusively in the somatodendritic compartment and 19 enriched ≥2-fold there, while 3 proteins were exclusively identified and 18 enriched in the axonal compartment. Our observation of compartment-specific enrichment of mitochondrial proteins was validated through immunofluorescence analysis of the localization and relative abundance of superoxide dismutase ( SOD2 ), sideroflexin-3 ( SFXN3 ) and trifunctional enzyme subunit alpha ( HADHA ) in retina and optic nerve specimens. The identified compartmental differences in RGC mitochondrial composition may provide promising leads for uncovering physiologically relevant pathways amenable to therapeutic intervention for optic neuropathies.

Considerations for developing mitochondrial transplantation techniques for individualized medicine

Tweetable abstract Mitochondrial transplantation has been used to treat various diseases associated with mitochondrial dysfunction. Here, we highlight the considerations in quality control mechanisms that should be considered in the context of mitochondrial transplantation.