In vitro and in vivo evaluation of hypericin for photodynamic therapy of equine sarcoids.

This study focused on evaluating the effectiveness of a specific compound, hypericin, in treating equine sarcoids (skin tumors in horses) by means of photodynamic therapy. Initial findings have shown promising results, with significant tumor reduction both at the end of the therapy and two months later.

Importance of the Research

• This research highlights the potential utility of hypericin, a photodynamic compound, as a non-invasive treatment agent against equine sarcoids, common skin tumours in horses.

In Vitro Evaluation

• The study first assessed the cytotoxic (cell-damaging) effect of hypericin on three distinct equine cell lines in the laboratory (in vitro).
• The researchers observed that the phototoxic effect (toxic effect upon exposure to light) of hypericin on these horse cell lines was approximately the same as its effect on several highly sensitive human cell lines.
• It was found that the energy density (amount of energy) used significantly influenced the phototoxic effect, but this effect was independent of the specific type of cell.

In Vivo Evaluation

• Apart from the in vitro test, the study also investigated the effect of photodynamic therapy using hypericin on actual equine sarcoids in a donkey (in vivo).
• Three equine sarcoids received four injections of the compound directly into the tumour (intratumoural injections).
• After the injections, the tumours were exposed to light daily for a period of 25 days.
• At the end of the therapy, the volume of the tumours had reduced by 81% and after a further two months, a total reduction of 90% was observed.

Conclusion and Future Work

• Based on these results, the study concluded that photodynamic therapy using hypericin holds promise as a non-invasive method for treating equine sarcoids.
• However, the paper calls for further experimentation, implying that more comprehensive studies will be needed before this treatment approach can definitively be recommended for wide use.