Comparative Analysis of the Bioactivity and Anti-Inflammatory Effects Against Endotoxin in Mitochondria for Transplantation: Impact of Muscle Origin in Rats.

Background: Mitochondria are essential for cellular energy production and cell survival. Mitochondrial dysfunction has been implicated in various neurological disorders, prompting the development of novel therapeutic approaches targeting these organelles. Among these, mitochondrial transplantation (MT), which replaces dysfunctional mitochondria with healthy counterparts from donor tissues, has emerged as a promising strategy. While skeletal muscle is a rich source of mitochondria, the optimal muscle tissue for MT remains unidentified, and the potential functional differences among mitochondria from various muscle types are not fully understood. This study investigates the quantity, size, respiratory function, energy production, and anti-inflammatory effects of mitochondria isolated from red skeletal muscle (RSM), mixed skeletal muscle (MSM), and white skeletal muscle (WSM).

Methods: Mitochondria were extracted from the soleus muscle (RSM), pectoralis major and rectus abdominis (MSM), and biceps brachii and gastrocnemius (WSM) of healthy 8-week-old male Sprague Dawley rats. Nanoparticle tracking analysis was employed to determine mitochondrial quantity and size. The activities of mitochondrial complexes I, II, and IV and adenosine triphosphate (ATP) content were assessed. The protective effects of mitochondria (100 μg/mL) from each muscle type against lipopolysaccharide (LPS, 5 μg/mL)-induced cell death and mitochondrial membrane potential disruption were evaluated in PC-12 neuronal cells.

Results: RSM-derived mitochondria exhibited a smaller average size and significantly higher mitochondrial content compared to those from MSM (mean size: = 0.0056, vs. pectoralis major; = 0.0056, vs. rectus abdominis; count of mitochondria: < 0.0001, vs. pectoralis major; < 0.0001, vs. rectus abdominis) and WSM (mean size: = 0.0006, vs. biceps brachii; < 0.0001, vs. gastrocnemius; count of mitochondria: < 0.0001, vs. biceps brachii; < 0.0001, vs. gastrocnemius). Additionally, RSM mitochondria demonstrated the highest activity of mitochondrial complex I among the three muscle types ( = 0.0001, vs. pectoralis major; = 0.0095, vs. rectus abdominis; < 0.0001, vs. biceps brachii; < 0.0001, vs. gastrocnemius). WSM-derived mitochondria showed relatively lower complex II activity ( = 0.0006, biceps brachii vs. soleus; = 0.0218, biceps brachii vs. rectus abdominis), while complex IV activity and ATP content were comparable across all groups. Supplementation with mitochondria isolated from RSM and WSM, but not MSM, effectively mitigated LPS-induced cell death (mitochondria isolated from soleus: = 0.0031; biceps brachii: = 0.0046; gastrocnemius: = 0.0169) and preserved mitochondrial membrane potential (mitochondria isolated from soleus: = 0.0204; biceps brachii: = 0.0086; gastrocnemius: = 0.0001) in PC-12 cells.

Conclusions: RSM emerges as the optimal source for mitochondrial extraction, demonstrating superior respiratory activity and significant protective effects against LPS-induced cell death and mitochondrial dysfunction. These findings provide critical insights into optimizing MT outcomes through the strategic selection of mitochondrial sources.