Identification of Cartilage Microbial DNA Signatures and Associations With Knee and Hip Osteoarthritis

Abstract

ObjectiveAlterations of the gut microbiota have been implicated in many forms of arthritis, but an examination of cartilage microbial patterns has not been performed. This study was undertaken to characterize the microbial DNA profile of articular cartilage and determine changes associated with osteoarthritis (OA).MethodsWe performed 16S ribosomal RNA gene deep sequencing on eroded and intact cartilage samples from knee OA patients (n = 21 eroded and 21 intact samples) and hip OA patients (n = 34 eroded and 33 intact samples) and cadaver controls (n = 10 knee samples and 10 hip samples). Microbial DNA diversity was assessed, groups were compared, and metagenomic profiles were reconstructed. Confirmation was performed in an independent cohort by clade‐specific quantitative polymerase chain reaction. Findings in human cartilage were compared to those in cartilage from OA‐susceptible C57BL/6 (B6) mice and OA‐resistant MRL/MpJ (MRL) mice. Germ‐free B6 mouse cartilage was analyzed as a methodologic control.ResultsAlpha diversity was reduced in human OA versus control samples (P < 0.0001), and in hip versus knee samples (P < 0.0001). Numerous clades were different in human OA versus control samples, and similar findings were noted in comparisons of murine B6 versus MRL mice. Hip samples were microbiologically distinct from knee samples. OA microbial DNA demonstrated increased gram‐negative constituents (P = 0.02). Functional analysis demonstrated increases in lipopolysaccharide production (P = 9.9 × 10−3), phosphatidylinositol signaling (P = 4.2 × 10−4), and nitrogen metabolism (P = 8 × 10−3) and decreases in sphingolipid metabolism (P = 7.7 × 10−4) associated with OA.ConclusionOur study reveals a microbial DNA signature in human and mouse cartilage. Alterations in this signature, including increases in gram‐negative constituents, occur during the development and progression of human OA. Furthermore, our findings indicate that strain‐specific signatures exist within mouse cartilage that mirror human patterns. Further study of the establishment and potential pathogenic role of these DNA signatures is needed.

Ear wound healing in MRL/MpJ mice is associated with gut microbiome composition and is transferable to non-healer mice via microbiome transplantation

“…Lactobacillus has been shown to be depleted within the gut during mouse aging [53], a known risk factor for OA development. These findings align with our previous work which identified Lactobacillales DNA as characteristic of both disease-free human control and OA-protected MRL cartilage [54]. Similarly, we found family Clostridiaceae within cecal microbiota to be highly correlated with ear wound healing, and we previously identified this clade as associated with disease-free human cartilage.…”

Ear wound healing in MRL/MpJ mice is associated with gut microbiome composition and is transferable to non-healer mice via microbiome transplantation

“…Lactobacillus has been shown to be depleted within the gut during mouse aging [49], a known risk factor for OA development. These findings align with our previous work which identified Lactobacillales DNA as characteristic of both disease-free human control and OA-protected MRL cartilage [50]. Similarly, we found family Clostridiaceae within cecal microbiota to be highly correlated with ear wound healing, and we previously identified this clade as associated with disease-free human cartilage.…”

Identification and Characterization of the Intra-Articular Microbiome in the Osteoarthritic Knee

“…Our results indicate that future studies of the intra-articular microbiome should be performed from different geographical locations in order to comprehensively characterize the various microbial compositions that are involved in the initiation and progression of OA. In addition, in light of a report by Dunn et al that identified a microbial DNA signature in human knee and hip cartilage [ 58 ], future work could include assessment of the synergistic role of the cartilage and synovial microbiomes in OA development. Lastly, the concurrent assessment of the gut, blood and intra-articular microbiome would support the hypothesis that a “leaky” gut allows for microbial migration from the gut to the joint, contributing to OA pathogenesis.…”