## 4 Discussion
Collagen is essential for preserving the biological and structural completeness of the ECM configuration. The interaction between cells and the collagen secreted by themselves is crucially implicated in cell adhesion and spreading, thereby playing a significant role in determining cellular differentiation pathways [46]. Furthermore, collagen type I is the primary constituent found in periodontal connective tissue. The cultivation of hMSCs on PCL/GE hybrid nanofiber materials has been shown to effectively promote the expression of COL1A1, which is in parallel with our study that GPP manifested an upregulation of COL1A1 until 14 days [47]. Surprisingly, VSCM enhanced the gene expression of COL1A1 less effectively than GPP. In contrast to COL1A1, the expression of FAK, which activates multiple signal transduction pathways that ultimately lead to promoted proliferation and migration, demonstrated a significant increase by GPP and VSCM in 2 weeks, respectively. Prior research has indicated consistent findings that both the GE scaffold and PCL/collagen nanofibers play crucial roles in the production of FAK [48; 49]. Simultaneously, cells engage with the ECM via integrin molecules, notably ITG-\(\upbeta\)1, leading to the activation of FAK [50]. The data we obtained revealed a notable upsurge in the expression of ITG-\(\upbeta\)1 within the GPP and VSCM groups compared to the TCP group after 3 days, whereas GPP induced a higher expression of this protein after 2 weeks. A similar finding was reported by a previous study showing a higher expression of ITG-\(\upbeta\)1 in human MSCs in a PCL-GE nanofiber environment than TCP after 21 days [51]. Further, actin is a prominent cytoskeletal protein that plays a vital role in facilitating cellular locomotion [52]. A specific PCL-GE electrospun material exhibits an increase in the expression of \(\upalpha\)-SMA in human smooth muscle cells [53]. In the same manner, \(\upalpha\)-SMA experienced upregulation due to GPP within 14 days, whilst VSCM appeared to exert a positive effect after the first week. Combining the above findings, it can be inferred that both GPP and VSCM positively regulate ECM generation and cellular functionality activation. Moreover, GPP demonstrated a slightly superior effect in comparison to VSCM. Angiogenesis, the process of forming novel blood vessels, holds significant importance in numerous biological processes, with particular significance in the context of wound healing [54]. VEGF is a potent growth factor known for its ability to stimulate the formation of blood vessels through angiogenesis [55]. TGF-\(\upbeta\)1 is also involved in angiogenesis and serves as a pivotal immunosuppressive secreted polypeptide. Moreover, as a versatile growth factor, it governs various behaviors and functions of fibroblasts and MSCs, thereby orchestrating tissue remodeling by producing connective tissue constituent and matrix proteins [56]. In our study, both VEGF-A and TGF-\(\beta\)1 mRNA levels increased when cultured on GPP within a two-week period, whereas VSCM only showed significant effects after 7 days. Similar to our experiment, several studies have also shown that PCL, GE, and collagen composite structures could promote the production of VEGF and TGF-\(\beta\)1 [57; 58; 59]. However, in terms of the protein content of VEGF-A in the conditioned media, VSCM demonstrated the highest values among the three groups. Additionally, regarding the concentration values of the TGF-\(\beta\)1 protein, the levels remained consistent across all materials. The discrepancy between the levels of gene expression and the subsequent quantity of protein expression could be attributed to various factors. First, gene expression is measured at a single time point, whereas the protein content reflects the total protein production for a certain time period. Moreover, distinct materials and specific proteins may interact in a different way. Collagen and GE structures have both been proven as effective carriers for the controlled release of growth factors [55; 60].