Ultrastructural mitochondrial alterations in equine myopathies of unknown origin.

The research analyzes the structure of muscle mitochondria in horses suffering from an unclassified muscle disease. The study found four cases where horses displayed unusual mitochondrial structure, suggesting a possible form of mitochondrial myopathy.

Objective of the Study

• The study aimed to examine the ultrastructure of muscle mitochondria in equine cases of myopathy, or muscle disease, of unknown origin.

Methods

• Biopsies were taken from the vastus lateralis of the Musculus quadriceps femoris, predominantly immediately post mortem, and processed for transmission electron microscopy.
• As a result, electron micrographs of 90 horses in total were available for analysis. This included 4 control horses, 16 horses suffering from myopathy, and 70 otherwise diseased horses.

Results

• After a thorough clinical and laboratory work-up, four out of five cases that didn’t fit into the usual algorithm to detect known causes of myopathy showed ultrastructural mitochondrial alterations.
• Distinct changes in the structure of the mitochondria were detected in four horses. These included small mitochondria with zones of completely disrupted cristae, extremely long and slender mitochondria, a mix of irregular and very large mitochondria next to smaller ones, and round mitochondria with only a few cristae.
• It remains uncertain whether the sub-sarcolemmal mitochondrial accumulations observed in the fifth patient have any pathological significance.

Conclusions

• The structural changes in the mitochondria were observed in at least four of the horses studied. However, in order to conclude that these alterations are due to mitochondrial dysfunctions, additional biochemical tests are recommended.
• The study concludes with the recommendation that mitochondrial myopathy should be considered in the differential diagnosis when examining horses presenting with muscle weakness.