Table 5.

Summary of in vivo studies utilizing microRNA as gene therapy.

Reference/Study	Country	Injury Model and Animal	Groups and Sample Size	Parameters for Efficacy	Main Result	Remarks
5. microRNA gene based therapy
a. MicroRNA-21 based gene therapy Li H.J. et al., 2018 [28]	China	ON crush model, rats	6 negative control, 6 injury only, 6 injury + agomir (miR-21 mimic), 6 injury + antagomir (miR-21 inhibitor)	Axon count and flash visual evoked potentials (F-VEP) amplitude and latency RGCs count	Injury + antagomir rats had significantly higher axons/mm compared to negative control at all measured distances away from ON injury (250, 500, and 1000 µm). F-VEP amplitude was significantly higher in injury + antagomir group compared to injury + agomir groups. There was no significant difference between the two in F-VEP latency measurements. Injury + antagomir rats had significantly increased RGCs compared to injury only.	F-VEP amplitude is associated with functional optic nerve fibres and latency is associated with optic nerve demyelination or conductive issues. The significance between agomir and antagomir was not assessed or did not reach significance, despite both separately having significantly lower and higher RGC counts, respectively, compared to injury only rats.