## 4 Discussion
This observation indicated that HE phosphorylated GSK3\(\beta\) via AKT or ERK signaling, but not p38 MAPK. Furthermore, MAPK signaling is also related to the proliferation of DP cells. We thus investigated the MAPK signaling pathway following HE treatment. As shown in Figure 4b, it was observed that HE did not affect MAPK signaling. Taking together, herein, we demonstrated that the activation of \(\beta\)-catenin signaling through HE treatment occurred by GSK3\(\beta\) activation via phosphorylation at the serine 9 residue by AKT. Moreover, it is known that DP cells display specific hair-inductive genes in parallel with hair growth. Representative hair-inductive genes, also known as DP signature genes, including _VEGF_, _IGF1_, _ALP_, _WNT5A_, _LEF1_, _FGF2_, _VCAN_, _NOG_, and _FGF7_, have been reported as essential factors that support hair follicle growth by DP cells. Hence, it was determined that DP signature genes were caused by HE treatment in HDP cells in our result (Figure 4c). In our data, HE also upregulated the intracellular protein expression levels of autocrine and paracrine factors including VEGF, IGF1, FGF2, and FGF7, while we confirmed that \(\beta\)-catenin inhibition with LY294002 attenuated the protein expression of FGF2 (Figures 4d and S3). In addition, cross-talking among DP cells and epithelial elements is essential for hair-inductivity [97]. DP cells modulate the growth of hair follicles via affecting both themselves and the neighboring epithelial elements with the aforementioned factors. To originate new follicles, epithelial elements react to growth factors secreted from DP cells, followed by proliferation and migration [98; 99; 100]. In this work, we also observed that HE significantly increased the secretion levels of growth factors from HDP cells (Figure 5a). It was further determined that the migration of ORS-like HaCaT keratinocytes was elevated by conditioned media from HDP cells (CM100) (Figure 5b). Lastly, our data in Figure 5c showed that CM100 could significantly upregulate the hair-growth-related genes, which induce catagen in keratinocytes, including _VEGF_, _IGF1_, and _IL-1a_. These data suggested that HE exerts chemokine secretion from HDP cells, facilitating the migration of surrounding keratinocytes in the follicular niche, and finally influences hair growth improvement. This work may have shortcomings in convincing researchers that _S. deserticola_ JD052 extract cures alopecia in the human body. In our data, we did not observe an increase in the hair-inductive properties or \(\beta\)-catenin signaling, along with its upstream effects, in the 3D-cultured HDP spheroid model. This model serves as an in vitro system to mimic the 3D spheroid structures found in vivo, in addition to enlarging the DP spheroid size [102]. Although mouse models are commonly used in hair loss research, they have inherent issues, including the absence of the vellus-to-terminal hair transition and the lack of androgenetic alopecia, a condition prevalent in humans [103]. To address these constraints, studies have demonstrated that culturing HDP cells in 3D spheroids preserves their transcriptional identity and enhances their hair-inductive potential [104; 105]. Notably, increased spheroid formation correlates with greater hair growth inductivity, and upon transplantation, these spheroids have been shown to induce de novo hair growth. These findings highlight the potential for the relevance of 3D spheroid culture systems as a promising in vitro model for investigating hair growth mechanisms. Nevertheless, to the best of our knowledge, this study is the first to demonstrate the activation of the following pathways using the _S. deserticola_ JD052 extract. Our findings provide strong evidence that HE activates the AKT/GSK3\(\beta\) pathway, subsequently leading to the activation of the \(\beta\)-catenin signaling pathway, while also enhancing the expression of hair-follicle-related genes in the in vitro 2D-cultured systems.