Microrna inhibitor system and methods of use thereof

A microRNA inhibitor system comprising a nucleic acid vector and at least one expression cassette, wherein each expression cassette comprises a promoter operably linked to a miR inhibitor, wherein the miR inhibitor comprises

• (a) a 5′ flanking structure that is 15 to 18 nucleotides in length,
• (b) a 3′ flanking structure wherein the 3′ flanking structure comprises
• (i) a first 3′ stem-loop region comprising a stem of 5 to 8 base pairs in length, and a first loop 8 to 18 nucleotides in length,
• (ii) a single-stranded region,
• (iii) a second stem-loop region;
• and
• (iv) a region of the 3′ flanking structure that forms a double stranded region with the 5′ flanking structure, and
• (c) an antisense oligonucleotide (ASO) having a 5′ end and a 3′ end, wherein the ASO is complementary to a target miR, wherein the ASO comprises a stem-loop region, and wherein the ASO is contiguously linked to the 5′ flanking structure at the 5′ end of the ASO, and to the 3′ flanking structure at the 3′ end of the ASO,
• wherein the 3′ flanking structure does not anneal to the ASO, and
• wherein the microRNA inhibitor is about 100 to 135 nucleotides in length.