## 2 Results  
### Cell Morphology and Attachment  
The cell growth patterns, and the specific structural features of the scaffolds, are depicted in SEM Figure 1. After 3 days of culture, hPDL-MSCs on GPP exhibited efficient proliferation and spread, predominantly assuming in spindle and polygonal shapes (Figure 1a). Numerous adhesion sites between cells and nanoscaled fibers were revealed under high-magnification images, with cells penetrating the material structure and integrating beneath the superficial fiber layer (Figure 1b). After 1 week, the surface of GPP was mostly covered by hPDL-MSCs. Observation at 1500x magnification demonstrated an interaction of hPDL-MSCs with the fibrous elements of GPP (Figure 1c,d). By the end of the 2-week culture period, GPP was covered by a cohesive and dense (multi)layer of hPDL-MSCs (Figure 1e,f). It was difficult to distinguish cells attached to VSCM on days 3 and 7, probably due to their migration inside the pores and their discrimination from the scaffold structures (Figure 1g-j). However, a continuous layer of interacting cells was established after 2 weeks, overlaying several of the microporous areas of the scaffold (Figure 1k,l).  
The visualization of actin filament and cell nuclei of hPDL-MSCs grown on various materials is shown in Figure 2. Cells grown on TCP exhibited a typical fibroblast-like morphology after 3 days of culture (Figure 2c). In contrast, hPDL-MSCs on GPP had both spindle- and polygonal-like morphologies and demonstrated an appearance of some branching structures (Figure 2a). Cells on TCP were almost confluent at this time point. In comparison to the other two substrates, VSCM was relatively scarcely populated by hPDL-MSCs, appearing in either spindle or polygonal shapes (Figure 2b). Upon 7 days of cell seeding, a marked enhancement in the cell density was noted among all three groups. Cells cultured on GPP and TCP approached full coverage of the material surfaces (Figure 2d,f). The observation of cells on VSCM was complicated by stained cells, which migrated within the membrane and appeared as cloud-like structures (Figure 2e). After 14 days of culture, GPP, and TCP were fully covered by hPDL-MSCs (Figure 2g,i), whereas the coverage of VSCM by the cells was still incomplete (Figure 2h). Moreover, compared to TCP, the cytoskeleton arrangement on GPP tended to be more paralleled oriented. At this stage, cells on VSCM presented a tendency to bridge and proliferate across the microporous structures of the scaffold. Compared to their morphology at 3 and 7 days, the cells further flattened and stretched; the intercellular connections intensified, forming a network structure without directional preference in cell alignment.  
Figure 1: Colonization and patterns of cells observation on two scaffolds through SEM. hPDL-MSCs were grown on GPP (**a–f**) or VSCM (**g–l**) for 3, 7, or 14 days. The images were taken at magnification 400-fold (**left panels**) or 1500-fold (**right panels**). Scale bars correspond to 100 μm and 20 μm, respectively. The yellow arrows indicate cells. GPP demonstrated nanoscale, microscale fiber, and VSCM a porous structure; cell attachment and growth were well-established on both substrates.