NPTX2 and Parkinson disease: Subsequently, CCK-8 assay was applied to measure the viability of PD cells, which illustrated that PD cells treated with oe-HOTAIR + sh-NC exhibited diminished viability compared to PD cells treated with oe-NC + sh-NC, while the viability of cells treated with oe-HOTAIR + sh-NPTX2 was much higher than those treated with oe-HOTAIR + sh-NC (all p < 0.05) (Figure 5A).