Molecular endotypes in musculoskeletal disorders: a systematic review

Musculoskeletal (MSK) disorders are highly heterogeneous and have diverse cellular and molecular pathobiological mechanisms, termed "endotypes". This systematic review aimed to summarize current knowledge of molecular endotypes in MSK disorders.

This review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA). Five databases including PubMed, Web of Science, Scopus, Ovid Medline, and Embase were searched for publications on molecular endotypes of MSK disorders classified by the International Classification of Diseases 11th Revision (ICD-11) that were published prior to September 1st, 2024. Articles were included if they were peer-reviewed original research articles on adult-onset human MSK disorder molecular endotypes/subtypes that used directly collected human specimen, in English language, and had full text available. Citations of the included studies were also screened manually using the same inclusion criteria.

Our search identified 44,660 unique records and 34 eligible studies were included. The majority of these studies focused on osteoarthritis (OA, n = 14) and rheumatoid arthritis (RA, n = 12), with a small number of studies focused on other MSK conditions. In OA, high- and low-inflammation clusters were consistently identified using different types of samples, and high- and low-pain clusters were observed in several other studies. In RA, endotypes with different levels of inflammation markers or treatment responses were reported in several studies, and one study reported that RA patients displayed two different dysbiotic microbiota patterns which corresponded to different responses to treatments.

MSK endotype research is still in its early stage. More endotype studies on MSK disorders are needed to assist in designing clinical trials and developing personalized therapy strategies.