Lactobacillus acidophilus supernatant alleviates osteoporosis by upregulating colonic SERT expression

Autophagy-induced osteoblast-derived exosomes maintain bone formation and prevent osteoporosis by remodeling gut microbiota-metabolism

BACKGROUND

Osteoporosis is a chronic disease of bone metabolism with high incidence rates. Recently, exosome therapy has emerged as a promising avenue for the treatment of osteoporosis. However, the role of autophagy-induced osteoblast-derived exosomes (Auto-exo) in osteoporosis has yet to be elucidated.

METHODS

The effect of Auto-exo in bone formation was assessed in vivo. The composition of gut microbiota was determined through 16S rDNA sequencing, and metabolite profiles were analyzed using liquid chromatography-mass spectrometry (LC-MS). Cell experiments were conducted to explore the role of bilirubin in bone formation.

RESULTS

Auto-exo were successfully isolated and identified. Auto-exo promoted bone formation and alleviated osteoporosis progression in a mouse model of osteoporosis. 16S rDNA sequencing revealed that Auto-exo changed diversity and composition of gut microbiota in osteoporotic mice, with a notable increase in Lactobacillus and a decrease in Dubosiella and Faecalibaculum. LC-MS analysis indicated that Auto-exo treatment reduced the elevated levels of bilirubin in osteoporotic mice. Cell experiments uncovered that bilirubin remarkably inhibited osteoblast differentiation. Furthermore, Auto-exo promoted osteoblast differentiation via inhibiting bilirubin production.

CONCLUSIONS

Our findings demonstrated that Auto-exo promoted bone formation by modulating the gut microbiota-metabolites bilirubin axis, thereby alleviating osteoporosis progression. This discovery provides a novel perspective on the mechanisms underlying the therapeutic effects of Auto-exo in osteoporosis.

A systematic review and meta-analysis of the effects of probiotics on bone outcomes in rodent models

Emerging evidence demonstrates an opportunity for using probiotics to support bone health, but findings in humans are limited. This systematic review investigated if probiotic supplementation improves bone mineral density (BMD) and bone structure in rodent models compared to no supplementation. Studies (n = 71) examining the effect of oral consumption of any probiotic strain on BMD or bone structure in rodents were included. Meta-analyses were conducted separately by study model (intact, ovariectomized) and bone site (femur, tibia, spine) to determine the probiotic effect (standardized mean difference, SMD) on volumetric BMD (vBMD), bone volume fraction (BV/TV), and cortical thickness (Ct.Th). Reasons for heterogeneity were explored (probiotic genus, sex, type of rodent). In intact rodents, probiotics resulted in greater vBMD (SMD = 0.43, 95% CI [0.13, 0.74], I2 = 3%, p < 0.05) and higher BV/TV (SMD = 0.63, 95% CI [0.25, 1.02], I2 = 57%, p < 0.05) at the femur without changes in cortical bone structure. In ovariectomized models, probiotic supplementation resulted in greater vBMD (femur: SMD = 1.28, 95% CI [1.01, 1.55], I2 = 3%, p < 0.05; tibia: SMD = 1.29, 95% CI [0.52, 2.05], I2 = 67%, p < 0.05; and spine: SMD = 1.47, 95% CI [0.97, 1.97], I2 = 26%, p < 0.05) as well as higher BV/TV (femur: SMD = 1.16, 95% CI [0.80, 1.52], I2 = 56%, p < 0.05; tibia: SMD = 2.13, 95% CI [1.09, 3.17], I2 = 79%, p < 0.05; spine: SMD = 2.04, 95% CI [1.17, 2.90], I2 = 76%, p < 0.05) and Ct.Th at the tibia (SMD = 2.35; 95% CI [0.72, 3.97], I2 = 82%, p < .0.05) but not at the femur versus control. The syntheses support probiotics as a strategy to improve bone outcomes in rodent models.

Extracellular Proteins Isolated from L. acidophilus as an Osteomicrobiological Therapeutic Agent to Reduce Pathogenic Biofilm Formation, Regulate Chronic Inflammation, and Augment Bone Formation In Vitro

Periprosthetic joint infection (PJI) is a challenging complication that can occur following joint replacement surgery. Efficacious strategies to prevent and treat PJI and its recurrence remain elusive. Commensal bacteria within the gut convey beneficial effects through a defense strategy named "colonization resistance" thereby preventing pathogenic infection along the intestinal surface. This blueprint may be applicable to PJI. The aim is to investigate Lactobacillus acidophilus spp. and their isolated extracellular-derived proteins (LaEPs) on PJI-relevant Staphylococcus aureus, methicillin-resistant S. aureus, and Escherichia coli planktonic growth and biofilm formation in vitro. The effect of LaEPs on cultured macrophages and osteogenic, and adipogenic human bone marrow-derived mesenchymal stem cell differentiation is analyzed. Data show electrostatically-induced probiotic-pathogen species co-aggregation and pathogenic growth inhibition together with LaEP-induced biofilm prevention. LaEPs prime macrophages for enhanced microbial phagocytosis via cathepsin K, reduce lipopolysaccharide-induced DNA damage and receptor activator nuclear factor-kappa B ligand expression, and promote a reparative M2 macrophage morphology under chronic inflammatory conditions. LaEPs also significantly augment bone deposition while abating adipogenesis thus holding promise as a potential multimodal therapeutic strategy. Proteomic analyses highlight high abundance of lysyl endopeptidase, and urocanate reductase. Further, in vivo analyses are warranted to elucidate their role in the prevention and treatment of PJIs.