## 3 Results and Discussion
### Antigaging Effects of Rice Stem Cell Extracts  
The beneficial effect of plasma-treated RSCE on oxidative damage may be due to the induction of the ability of fibroblasts to inhibit senescence. To support this hypothesis, we compared the mRNA expression levels of skin aging-related genes in fibroblasts with and without RSCE treated with plasma after oxidative stress treatment. The formation of oxidative stress increases the amount of matrix metalloproteinase (MMP)-9 expression in fibroblasts, which in turn leads to the degradation of collagen. Increased collagen breakdown by MMP-9 may eventually be a key factor in the aging process of skin tissue [42; 43]. Here, we confirmed that the oxidative stress treatment of t-BHP significantly increased the MMP-9 expression level of HFB, suggesting that RSCE may have anti-aging activity by suppressing the MMP-9 mRNA expression level. The levels of gene expression were quantified as fold changes in expression using the GAPDH as a housekeeping gene. Plasma-treated RSCE reduced the expression level of MMP-9 by 2.8-fold. This expression level showed about 0.8-fold inhibition efficiency compared with RSCE not treated with plasma (Figure 7A). [PERSON] et al. demonstrated that the Centella callus extract significantly inhibited the upregulation of MMP-9 mRNA expression after H\({}_{2}\)O\({}_{2}\) exposure [41]. A decrease in MMP  
Figure 6: Antioxidant enzymes expression of RSCE. All measurements were made in 3 or more than 3 replicates. * \(p<0.05\); ** \(p<0.01\).  
levels may be associated with increased collagen production after plasma-treated RSCE treatment. Moreover, collagen has anti-aging properties, so when the skin is exposed to UV rays for a long time, proteolytic enzymes increase and break down collagen and elastin fibers (elastic fibers) that make up the skin, causing wrinkles that reduce skin elasticity [44]. Therefore, we compared the mRNA expression patterns of HFB for collagen synthesis-related genes in conditions with and without plasma-treated RSCE. Our qRT-PCR results showed that RSCE treated with N2 plasma for 3 min had a regenerative effect on the oxidative damage of HFB (Figure 7B). In HFB, in which the COI-1 expression level was decreased by t-BHP oxidative stress, the COI-1 mRNA expression level was increased again by RSCE. The plasma-treated RSCE (2-fold) showed a significant difference in the expression level of COI-1 and slightly enhanced it compared with the non-plasma-treated RSCE (1.5-fold). The mRNA expression level for COI-1 showed a profile in contrast with that of MMP-9. By analyzing the gene expression of RSCE on fibroblasts, we found common molecular pathway activation and response to the stresses connected to anti-aging. This might involve that skin fibroblasts responded correctly to the anti-aging effects of RSCE. Our findings give novel insight into utilizing RSCE for anti-aging effects and its possible mechanism. Although more molecular mechanism studies are required to develop anti-aging strategies with RSCE, our results suggest that plasma may be a potential tool used to enhance the activity of callus extracts to prevent oxidative stress.  
Figure 7: Quantitative RT-PCR analysis of anti-aging-related genes MMP-9 and Col-1 after treatment of RSCE in HFB. (**A**) MMP-9 (**B**) Col-1. All measurements were made in more than 3 replicates. * \(p\) < 0.05; **_p_ < 0.01.  
All data points represent mean \(\pm\) standard deviation of three replicate experiments. The significance of difference between the control and treatment was examined by Student's \(t\)-test; * \(p<0.05\); ** \(p<0.01\). In order to observe the t-BHP-induced cytotoxicity-prevention activity of plasma-treated RSCE, HFB cells were pretreated with RSCE (3\({}^{\prime}\) RSCE vs. 0\({}^{\prime}\) RSCE) at a concentration of 0.1 mg/mL and plasma-treated for 24 h before t-BHP treatment.