Table 2 The advantages and disadvantages of different methods targeting circRNA therapeutics

In vitro

RNAi

ShRNA, siRNA, ASO.

KD

1. Convenient to synthesis and deliver;

2. Relative low expense.

1. Rapid degradation;

2. Low delivery efficiency;

3. Lack of cell-specificity;

4. Off-target effect.

In vivo &vitro

CircRNA expression vector

Plasmid, LV, AAV.

OE & KD

1. Relative stable;

2. Frequently used.

1. Mis-spliced product;

2. Off-target effects.

In vivo & vitro

Synthetic circRNA

Circularized RNAs

OE

Highly purified.

1. Difficult to generate large amount;

2. Immune system activation.

In vivo

Nanoparticle

Liposome, polymer, dendrimer, inorganic material (gold, or metal oxides).

OE & KD

1. Target specific cell through receptors and ligands;

2. Relatively stable from degeneration;

3. Facilitate cell uptake;

4. Prevent to immune activation.

1. Limited to target to the cytoplasmic circRNAs;

2. Low delivery efficiency;

3. Toxicity.

In vivo &vitro

Exosome

Exosome

OE & KD

1. Protect RNAi molecules from degradation;

2. Promote cellular uptake;

3. Biocompatible.

1. Difficult in manufacturing;

2. High cost.

In vivo

Cre-lox system

Cre recombinase

KO

1. Cell-type specific or tissue specific;

2. Relatively safe.

1. Ectopic Cre expression leads to the off-target effect;

2. Need validation of genotyping.