Effective mechanism of polysaccharides from Erxian herbal pair in promoting bone repair in traumatic osteomyelitis by activating osteoblast GPR41 and inhibiting the MEK/ERK/MAPK signalling axis

Polysaccharides are the key components of natural products; however, their effects on bone repair haven't been fully evaluated. This study aimed to assess the efficacy and mechanism of polysaccharides in promoting bone repair. The Erxian herb pair polysaccharide (EHP) was isolated and purified using water extraction (1:20 (w/v); 100 ± 2 °C; 5 h) and alcohol precipitation (80 ± 2 %). A traumatic osteomyelitis (TO) rat model was established using lipopolysaccharide (LPS). The gut microbiota was analysed through intestinal flora and metagenomic sequencing. The results revealed that the yields of crude polysaccharide and purified polysaccharide EHP were 3.73 ± 0.34 % and 0.48 ± 0.06 %, respectively. The total sugar content of EHP was 83.53 ± 0.16 %. The EHP, with a molecular weight of 31.964 kDa, was primarily composed of mannose, rhamnose, glucose, galactose, and arabinose. In vivo experiments demonstrated that EHP intervention (300 mg/kg/day) significantly augmented bone density and enhanced the activity of alkaline phosphatase (ALP) (P < 0.01). EHP upregulated the abundance of probiotics and increased the production of butyric acid (P < 0.05). In vitro experiments revealed that butyric acid (500–1000 μM) enhanced osteoblast activity and inhibited the expression of mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated kinase (ERK) (P < 0.01). These findings indicate that polysaccharides may represent a promising therapeutic agent for bone-healing.