Comparison of siRNA-mediated silencing of glycosaminoglycan synthesis genes and enzyme replacement therapy for mucopolysaccharidosis in cell culture studies

Cytotoxicity of laronidase (Aldurazyme®), employed in enzyme replacement therapy (ERT) for mucopolysaccharidosis type I (MPS I) and various siRNAs, tested previously in studies on substrate reduction therapy (SRT) for mucopolysaccharidoses, was tested. The enzyme did not cause any cytotoxic effects, and the siRNAs did not inhibit growth of most investigated cell lines. However, some cytotoxic effects of some tested siRNAs were observed in one MPS IIIA cell line. The efficacy of a combination of enzyme replacement therapy and siRNA-based substrate deprivation therapy was tested on three MPS I cell lines. Surprisingly, different results were obtained for different cell lines. The decrease of glycosaminoglycan storage in cells treated simultaneously with both methods was: (i) less pronounced than obtained with either of those methods used alone in one cell line, (ii) similar to that observed for enzyme replacement therapy in another cell line, and (iii) stronger than that obtained with either of the methods used alone in the third cell line. Therefore, it appears that the effects of various therapeutic methods may strongly depend on the features of the MPS cell line.