## 3 Results
### HE Uregulates the Expression Levels of Growth Factors and DP Signature Genes in HDP Cells  
As mentioned above, DP cells function as a source of growth factors, modulating hair growth via autocrine and paracrine mechanisms [67,68]. Several previous studies have also reported hair-induction-related genes called DP signature genes, including _VEGF_, _IGF1_, _FGF2_, _FGF7_, _WNT5A_, alkaline phosphate (_ALP_), versican (_VCAN_), noggin (_NOG_), and lymphoid enhancer binding factor 1 (_LEF1_) [69, 70, 71, 72, 73]. We then validated whether the expression levels of DP signature genes are upregulated by HE treatment compared to the DMSO-treated control (Figure 4c). Indeed, the levels of DP signature genes were increased by treatment with HE. Subsequently, we investigated the intracellular protein expression levels of VEGF, IGF1, FGF2, and FGF7 using Western blot analysis (Figure 4d). We found that HE upregulated the expression levels of those proteins. Moreover, the inhibition of \(\beta\)-catenin using LY294002, a PI3K/AKT inhibitor, attenuated the protein expression level of FGF2, a key signature gene of DP cells (Figure S3). Taken together, our data indicate that the treatment of HE upregulates the expression of growth factors regulated by \(\beta\)-catenin and effectively enhances the hair-inductive properties of HDP cells. Figure 4: Effect of HE on AKT/GSK\(\beta\) and MAPK signaling activation. HDP cells were treated with 50 and 100 ug/mL of HE for 48 h. (**a**) AKT/GSK\(\beta\) and (**b**) MAPK (p38, ERK, JNK) signaling phosphorylation and the protein expression of growth factors were analyzed using Western blot analysis with specific antibodies. \(\beta\)-catenin served as a loading control for total protein. The quantification of phosphorylation and protein levels was performed using ImageJ software v. 1.52a and normalized to total protein levels. (**c**) mRNA levels of hair-inductivity-related genes (_VEGF_, _IGF1_, _FGF7_, _ALP_, _VCAN_, _NOG_, _LEF1_, _FGF2_, and _WNT5A_) were assessed using RT-qPCR. _GAPDH_ was used for normalizing the mRNA expression level. (**d**) Intracellular proteins of VEGF, IGF1, FGF2, and FGF7 determined by Western blot analysis with \(\beta\)-actin serving as a loading control for total protein. Each bar represents the mean \(\pm\) SD of 3 independent experiments. Significance was determined using a one-way ANOVA followed by Tukey’s test. \({}^{*}p<0.05\), \({}^{**}p<0.01\), \({}^{**}p<0.001\) compared with the vehicle-treated group. n.s. means non-significant. HE, heterotrophic-cultured \(S\). _deserticola_ JD052 extract; HDP, human dermal papilla; RT-qPCR, real-time quantitative polymerase chain reaction. HE-Treated Conditioned Media in HDP Cells Is Responsible for Promoting Migration of HaCaT Keratinocytes and Hair Follicle Growth  
The process of new hair regrowth involves a signaling exchange between DP cells and stem/progenitor cells, resembling embryonic hair follicle formation. Furthermore, the hair growth cycle is meticulously orchestrated by reciprocal interactions between epithelial and mesenchymal cells [74; 75]. Outer root sheath (ORS) keratinocytes are crucial for hair follicle function, playing a key role in development, regeneration, and elongation, and serve as a critical link between the hair follicle and the epidermis [76; 77]. Cytokines and growth factors emanating from DP cells direct adjacent epithelial cells to undergo proliferation and differentiation [78; 79]. Therefore, we determined whether conditioned media (CM) from HE-treated HDP cells can affect the ORS-like HaCaT keratinocytes. We first observed that the protein levels of growth factors, including VEGF, IGF1, FGF2, and FGF7, at a dose of 100 \(\upmu\)g/mL of HE-treated conditioned media (CM100) were higher than the levels of those proteins in DMSO-treated conditioned media (CM0) using Western blot analysis (Figure 5a). Additionally, compared to cells cultured in serum-free DMEM and CM0, CM100 augmented the chemotactic migration of HaCaT keratinocytes (Figure 5b).