Antisense Oligonucleotide Therapy: Exploring Methods for Ovarian Delivery in a Mouse Model

Introduction:
Antisense oligonucleotide (ASO) is a single stranded oligonucleotide, which binds to intracellular endogenous mRNA and can modulate gene expression. ASO based therapy offers an alternative approach for treating genetic disorders. In the case of Fragile X premutation, about 25% of the carriers may suffer from premature ovarian failure (POI) due to few suggested causative mechanisms such as protein toxicity. A recent study suggested that an ASO based therapy may block the protein toxicity mechanism and have beneficial therapeutic effect. However, following systemic administration, ASOs mainly distribute to the liver and kidneys while reaching other tissues is more challenging.

Aim:
To evaluate and compare the effect of intra peritoneal (IP) and direct ovarian injections on the distribution of an ASO targeting MALAT1 in the ovary.

Methods:
An ASO targeting MALAT1 was injected IP and directly to the ovaries of mice. To visualize the ASO’s distribution within the ovaries, in situ hybridization staining was performed. To evaluate the effect of the ASO on MALAT1 expression levels in the injected ovaries we used relative quantification analysis of RT-qPCR results.

Results:
Direct ovarian injections revealed penetration to the stromal cells but not the follicular apparatus of the injected ovary. Furthermore, downregulation of approximately 26% in MALAT1 mRNA expression levels was observed.

In contrast, IP injections ASO did not manage to efficiently penetrate the ovaries and accumulated in the liver and kidneys.

Conclusions:
A direct ovarian injection can potentially deliver ASOs to the stromal cells of the ovary but not to the follicular apparatus.