PLANT SMALL RNA TECHNOLOGY 123 this miRNA decreased with senescence. In senescent cells, after treatment with PSR bao- bab extract, the level of miRNA-19b exceeded the basal level of young cells. MiRNA- 19b level was previously shown to be associated with senescence and with the quality of collagen (19). The induction of senescence was verifi ed by SA β-galactosidase staining at different pas- sages. As expected, an increase in SA β-galactosidase activity was observed in in vitro se- nescent cells (Figure 6). The image quantifi cation of SA β-galactosidase activity allowed us to observe a decrease in this marker in senescent fi broblasts that were treated with PSR baobab extract this observed decrease was more pronounced than with the placebo treatment. In summary, these results allowed us to compare the effect of both PSR and placebo bao- bab extracts. We noted a better effi ciency of PSR extract on the modulation of certain aging markers: an increase in collagen expression in ex vivo skin, an increase in miRNA-19b expression, stability in Drosha expression, and a decrease in SA β-galactosidase activity in Figure 4. Observation of collagen I expression in ex vivo human skin biopsies and fi broblasts: (A) skin bi- opsies were treated with 1% PSR baobab extract or with 1% placebo (baobab extract without small RNA) for 48 h (twice a day) (´20). Collagen I immunohistological staining in green and nuclei counter-stained in blue with DAPI (on the original pictures) (´20). Quantifi cation of immunohistological staining of collagen I (intensity in % adjusted by considering the area of the examined dermis zone ns not signifi cant * signifi cant compared with control, with Student’s t test, n = 3). (B) Expression of collagen I mRNA in fi broblasts treated with 1% baobab PSR or placebo extracts for 24 h (twice a day). Error bars corresponded to the calcu- lated RQmin and RQmax values, based on standard deviation of the mean expression level ***: highly sig- nifi cant compared with young control cells, compared with senescent control cells (indicated by an arrow) with Student’s t test, n = 3 replicates.

JOURNAL OF COSMETIC SCIENCE 124 aged skin fi broblasts. These results allowed us to conclude that application of the small RNA-rich Baobab extract helps skin cells to counter the visible signs of skin aging via the modulation of essential markers of senescence. CONCLUSION Although there are many antiaging cosmetic products on the consumer market offering a wide range of skin benefi ts, there remains a need for effective topically applied cosmetic compositions that provide antiaging or rejuvenating benefi ts to the skin, hair, and/or nails using natural ingredients as active agents. In this article, we present an innovative extraction technology that allows for the generation of new botanical extracts containing small RNAs, which can be used as natural cosmetic ingredients. PSR technology appears to be well adapted to plant species such as baobab. Indeed, baobab trees are well-known for their capacity for survival and longevity, which is supported in particular by its small RNAs that can rapidly regulate gene expression and enable adaptation to stressful envi- ronment. By addressing the maintenance of miRNA maturation machinery in the skin, Figure 6. Evaluation of SA β-galactosidase activity in young (P7) and senescent (P31) fi broblasts treated with 1% PSR baobab extract or with 1% placebo (baobab extract without small RNA) for 48 h (twice a day) (×20). Quantifi cation of blue staining (intensity in % adjusted by considering the cell number) ***: highly signifi cant, *: signifi cant compared with young control cells or compared with senescent control cells (indi- cated with an arrow) with Student’s t test, n = 3 replicates. Figure 5. Evaluation of Drosha mRNA (A) and miRNA-19b (B) levels in young (P8) and senescent (P32) fi broblasts treated with 1% PSR baobab extract or with 1% placebo (baobab extract without small RNA) for 24 h (twice a day). Error bars corresponded to the calculated RQmin and RQmax values, based on standard deviation of the mean expression level ***: highly signifi cant compared with young control cells, compared with senescent control cells (indicated by an arrow) with Student’s t test, n = 3 replicates.