## 3 Results and Discussion
### Experimental Study on Cell Adhesion within HA/WS Skeleton In Vitro  
The C57 BL/J6 murine preosteoclast cells were utilized for conducting in vitro cell adhesion assays on a three-dimensional porous HA/WS scaffold. The cells were seeded onto the scaffold, stimulated with 100 ng/mL rRNAKL and 10 ng/mL M-CSF, and subsequently cultured under controlled humidified conditions. After three days of incubation, the cells were fixed using 4% PFA and lightly coated with carbon. The adhesion of cells to the porous skeleton was examined using both scanning electron microscopy as well as optical microscopy. Numerous researchers have acknowledged the extensive interactions between cells and the microenvironment surrounding the skeletal surface during in vitro growth and culture, with three-dimensional culture models being more adept at simulating in vivo conditions compared to traditional two-dimensional cell culture models. In order to construct a three-dimensional cell culture model, we devised and manufactured an HA/WS porous skeleton featuring an interconnected micro-scale porous network that facilitates fluid delivery through its pores, thereby closely mimicking natural cellular growth processes. As depicted in Figure 17, osteoclasts exhibit robust adhesion, spreading, and proliferation on the three-dimensional porous HA/WS skeleton, indicating excellent biocompatibility. The presence of a three-dimensional porous structure further enhances the microenvironment for osteoclast adhesion and proliferation. Immersion in SBFs and the subsequent functional modification of the three-dimensional porous HA/WS skeleton to induce apatite nanocrystal formation within its structure represent an effective approach for promoting osteoclast adhesion, growth, and culture. As depicted in Figure 18, the adhesion morphology of osteoclasts on the three-dimensional porous HA/WS skeleton was suboptimal in the absence of SBF immersion, with a sparse and uneven distribution. Only a limited number of osteoclasts exhibited adherence to the three-dimensional porous HA/WS skeleton. Despite imperfect adhesion, this observation still suggests that HA/WS three-dimensional porous skeletons possess biological activity. Figure 16: Surface element analysis results of three-dimensional porous HA/WS skeleton immersed in simulated body fluids for 21 days. Comparing the three-dimensional porous HA/WS skeleton without SBFs, shown in Figure 18, and the three-dimensional porous HA/WS skeleton immersed in SBFs, shown in Figure 18c, the pretreatment of the three-dimensional porous HA/WS skeleton with SBF facilitated enhanced growth, permeation, and filling by osteoclasts. As shown in Figure 19, after SBF immersion, the proliferation of osteoclasts in the skeletal pore wall and inner pore was significantly promoted with the assistance of apatite nanocrystals. The results indicated that HA/WS three-dimensional porous skeleton had good biocompatibility, and the three-dimensional porous skeleton structure provided a good microenvironment for the adhesion and proliferation of osteoclasts, and promoted the adhesion, growth and culture of osteoclasts. Figure 17: Optical images of adhesion status of osteoclast cell adhesion on HA/WS skeleton (top view) after 3 days of seeding; (**a**,**b**) non-SBF-immersed porous HA/WS skeleton; (**c**) SBF-immersed porous HA/WS skeleton. Figure 18: The SEM images of HA/WS three-dimensional porous osteoclasts cultured without SBF immersion. (**a**-**c**) SEM images of osteoclasts on HA/WS at different magnifications. The three-dimensional porous HA/WS skeleton possesses a highly porous network with an optimal pore size range of 100 \(\upmu\)m to 500 \(\upmu\)m, facilitating the fluid flow of SBFs in three-dimensional cell culture models. Our findings demonstrate that the pretreated apatite nanocrystal-coated three-dimensional porous HA/WS skeleton promotes the adhesion and proliferation of preosteoclast cells, making it more suitable for osteoclast culture compared to the surface of a conventional 24-well cell culture plate.