Abstract/Summary

Envenomation by the Indian ornamental tarantula (Poecilotheria regalis) is medically relevant to humans, both in its native India and worldwide, where they are kept as pets. Muscle-related symptoms such as cramps and pain are commonly reported in humans following envenomation by this species. There is no specific treatment including antivenom for its envenomation. Moreo-ver, the scientific knowledge on the impact of this venom on skeletal muscle function is highly limited. Therefore, we carried out this study to better understand the myotoxic properties of Poe-cilotheria regalis venom by determining its effects in cultured myoblasts and in the tibialis anteri-or muscle in mice. While there was no effect found on undifferentiated myoblasts, the venom af-fected differentiated multinucleated myotubes resulting in the inhibition of fusion and atrophy of myotubes. Similarly, intramuscular administration of this venom in the tibialis anterior muscle in mice resulted in extensive muscle damage on day 5. However, by day 10, the regeneration was evident, and the regeneration process was continuing until day 20. Nevertheless, some tissue ab-normalities including reduced dystrophin expression and microthrombi presence were observed on day 20. Overall, this study demonstrates the ability of this venom to induce significant muscle damage and affect its regeneration in the early stages. These data provide novel mechanistic in-sights into this venom-induced muscle damage and guide future studies to isolate and character-ise individual toxic component(s) that induce muscle damage and their significance in developing better therapeutics.