Temperature-responsive Rehmannia polysaccharides hydrogel loaded with bone marrow mesenchymal stem cells for bone...

Rehmannia, a natural medicinal and functional plant, has been used as a Chinese materia medica and dietary supplement for a long time, with its polysaccharides being the main bioactive ingredients. Natural polysaccharide hydrogels loaded with bone marrow mesenchymal stem cells (BMSCs) represent an effective strategy for bone defect repair. In this study, a neutral homogeneous polysaccharide (RP-1) was isolated from Rehmannia glutinosa, and it was mainly formed by →2)-β-D-Fruf-(1→, →6)-α-D-Glcp-(1→, →6)-α-D-Galp-(1 → and α-D-Galp-(1 → as backbone. In vitro cell experiments indicated that RP-1 could promote the proliferation and osteogenic differentiation of BMSCs. Then, temperature-sensitive RP-1 hydrogels loaded with BMSCs (RPB@Gel) were prepared and characterized to demonstrate rapid cross-linking at body temperature, and their bone defect repair efficacy was systematically validated through in vitro and in vivo experiments. In vitro studies demonstrated that RPB@Gel hydrogels promoted the proliferation and differentiation by upregulating the mRNA and protein expression (RUNX2, ALP, and Col1a1) in BMSCs. The mechanisms by which this occurs include the activation of the ERK phosphorylation pathway and the facilitation of β-catenin nuclear translocation. In vivo studies demonstrated that RPB@Gel exhibits significant bone defect repair efficacy, as evidenced by micro-CT scanning, histological analysis, and immunohistochemical staining. In summary, within the field of bone defect repair, RP-1 functions both as a bioactive component and as a structural carrier, and RPB@Gel may offer a potential therapeutic approach for bone regeneration.