Targeted delivery of a triplex-forming oligonucleotide to hepatic stellate cells

Liver fibrosis is characterized by abnormal accumulation of extracellular matrix (ECM), namely, fibrillar collagens in the hepatic stellate cells (HSCs). Earlier, we developed an antigene approach, using a type alpha 1 (I) collagen gene promoter specific triplex-forming oligonucleotide (TFO) to inhibit collagen gene expression. In this paper, to enhance overall delivery of TFOs to the liver and more specifically to HSCs, we synthesized mannose 6-phosphate-bovine serum albumin (M6P-BSA) by phosphorylating p-nitrophenyl-alpha-D-mannopyranoside, reducing its nitro group, and reacting it with thiophosgene to produce p-isothiocyanatophenyl-6-phospho-alpha-D-mannopyranoside (itcM6P) for conjugation with BSA. P-33-TFO was conjugated with M6P-BSA via a disulfide bond, and the stability of the (M6P)(20)-BSA-TFO conjugate was determined. Following tail vein injection into rats, (M6P)(20)-BSA-P-33-TFO rapidly cleared from the circulation and accumulated mainly in the liver. Almost 66% of the injected (M6P)(20)-BSA-P-33-TFO accumulated in the liver at 30 min postinjection, which was significantly higher than that deposited after injection of 33P-TFO. A large proportion of the injected (M6P)(20)-BSA-P-33-TFO was taken up by the HSCs as evidenced by determination of radioactivity in the digested liver cells upon liver perfusion and separation on a Nycodenz gradient. Therefore, this TFO conjugate may be used for the treatment of liver fibrosis.