Elucidating the role of inflammatory mediators in frozen shoulder

Frozen shoulder is a painful inflammatory fibrotic disease of the glenohumeral joint capsule. While it’s frequently self-limiting, patients can be symptomatic for years. The underlying pathophysiology of frozen shoulder is not fully understood, hampering the development of an effective therapy. Increased expression of inflammatory mediators has been identified in frozen shoulder, suggesting a potential role for these mediators in disease. However, the precise cellular interactions and the cell types expressing inflammatory mediators have not been identified. A single cell atlas revealed that the rotator interval of the glenohumeral joint capsule is comprised of fibroblasts, myeloid cells, lymphocytes, endothelial cells, and mural cells. Clustering of myeloid cells revealed a CD48+IL1A+ macrophage subset which showed increased expression of several pro-inflammatory genes, including PTGS2, S100A8, EREG, IL1A, IL1B, IL1R1, IL1RN. In frozen shoulder, CD48+IL1A+ macrophages show increased expression of several pro-inflammatory genes, including IL-1 genes (IL1A, IL1B, IL1R1). CD48+IL1A+ macrophages were localised to both the lining and sub-lining regions of the rotator interval of the glenohumeral joint capsule. The expression (immunohistochemistry) of CD68, CD48, IL-1α, IL-1β, and IL-1R was increased in frozen shoulder relative to comparator patient tissues. As the IL1R1 gene was mainly expressed by fibroblasts, ligand-receptor interaction analysis predicted several important IL-1 ligand-receptor pairs between CD48+IL1A+ macrophages and fibroblast populations, including IL1A-IL1R1 and IL1BIL1R1. In turn, fibroblast populations were predicted to communicate with myeloid cell populations via the CSF1-CSF1R pathway. Fibroblasts derived from frozen shoulder capsular tissues acquire an inflammatory fibrotic phenotype upon IL-1α and/or IL-1β stimulation, which was characterised by an increase in inflammation (CCL2, CCL5, CCL8, CCL20, CXCL3, CXCL5, NFKBIA, NFKBIZ, IGF1, FGF7, IL6, CSF2, CSF3) and fibrosis related genes (TGFB1, TGFBR1, WNT5A, COL3A1, MMP2, TIMP1), as well as an increased secretion of inflammatory mediators (CXCL-12, GMCSF, IL-1RA, IL-33, IL-6). This thesis provides novel insight into the cellular basis of frozen shoulder, revealing a distinct CD48+IL1A+ macrophage subset enriched for inflammation in advanced-stage frozen shoulder. CD48+IL1A+ macrophages release IL-1α and IL-1β, which activate surrounding macrophages and fibroblasts via IL-1R to release chemokines and other inflammatory mediators, further promoting inflammation and fibrosis. This data supports the hypothesis that macrophage-fibroblast crosstalk contributes to the underlying pathophysiology of frozen shoulder. Importantly, this thesis provides sufficient data to identify the IL-1R pathway as a potentially important therapeutic target

A single cell atlas of frozen shoulder capsule identifies features associated with inflammatory fibrosis resolution

Frozen shoulder is a spontaneously self-resolving chronic inflammatory fibrotic human disease, which distinguishes the condition from most fibrotic diseases that are progressive and irreversible. Using single-cell analysis, we identify pro-inflammatory MERTKlowCD48+ macrophages and MERTK + LYVE1 + MRC1+ macrophages enriched for negative regulators of inflammation which co-exist in frozen shoulder capsule tissues. Micro-cultures of patient-derived cells identify integrin-mediated cell-matrix interactions between MERTK+ macrophages and pro-resolving DKK3+ and POSTN+ fibroblasts, suggesting that matrix remodelling plays a role in frozen shoulder resolution. Cross-tissue analysis reveals a shared gene expression cassette between shoulder capsule MERTK+ macrophages and a respective population enriched in synovial tissues of rheumatoid arthritis patients in disease remission, supporting the concept that MERTK+ macrophages mediate resolution of inflammation and fibrosis. Single-cell transcriptomic profiling and spatial analysis of human foetal shoulder tissues identify MERTK + LYVE1 + MRC1+ macrophages and DKK3+ and POSTN+ fibroblast populations analogous to those in frozen shoulder, suggesting that the template to resolve fibrosis is established during shoulder development. Crosstalk between MerTK+ macrophages and pro-resolving DKK3+ and POSTN+ fibroblasts could facilitate resolution of frozen shoulder, providing a basis for potential therapeutic resolution of persistent fibrotic diseases

A single cell atlas of frozen shoulder capsule identifies features associated with inflammatory fibrosis resolution

Frozen shoulder is a spontaneously self-resolving chronic inflammatory fibrotic human disease, which distinguishes the condition from most fibrotic diseases that are progressive and irreversible. Using single-cell analysis, we identify pro-inflammatory MERTKlowCD48+ macrophages and MERTK + LYVE1 + MRC1+ macrophages enriched for negative regulators of inflammation which co-exist in frozen shoulder capsule tissues. Micro-cultures of patient-derived cells identify integrin-mediated cell-matrix interactions between MERTK+ macrophages and pro-resolving DKK3+ and POSTN+ fibroblasts, suggesting that matrix remodelling plays a role in frozen shoulder resolution. Cross-tissue analysis reveals a shared gene expression cassette between shoulder capsule MERTK+ macrophages and a respective population enriched in synovial tissues of rheumatoid arthritis patients in disease remission, supporting the concept that MERTK+ macrophages mediate resolution of inflammation and fibrosis. Single-cell transcriptomic profiling and spatial analysis of human foetal shoulder tissues identify MERTK + LYVE1 + MRC1+ macrophages and DKK3+ and POSTN+ fibroblast populations analogous to those in frozen shoulder, suggesting that the template to resolve fibrosis is established during shoulder development. Crosstalk between MerTK+ macrophages and pro-resolving DKK3+ and POSTN+ fibroblasts could facilitate resolution of frozen shoulder, providing a basis for potential therapeutic resolution of persistent fibrotic diseases

Management and outcomes of femoral periprosthetic fractures at the hip: data from the characteristics, outcomes and management of periprosthetic fracture service evaluation (COMPOSE) cohort study

Aims The aim of this study was to describe the management and associated outcomes of patients sustaining a femoral hip periprosthetic fracture (PPF) in the UK population. Methods This was a multicentre retrospective cohort study including adult patients who presented to 27 NHS hospitals with 539 new PPFs between 1 January 2018 and 31 December 2018. Data collected included: management strategy (operative and nonoperative), length of stay, discharge destination, and details of post-treatment outcomes (reoperation, readmission, and 30-day and 12-month mortality). Descriptive analysis by fracture type was performed, and predictors of PPF management and outcomes were assessed using mixed-effects logistic regression. Results In all, 417 fractures (77%) were managed operatively and 122 (23%) conservatively. The median time to surgery was four days (interquartile range (IQR) 2 to 7). Of those undergoing surgery, 246 (59%) underwent revision and/or fixation and 169 (41%) fixation alone. The surgical strategy used differed by Unified Classification System for PPF type, with the highest rate of revision in B2/B3 fractures (both 77%, 176/228 and 24/31, respectively) and the highest rate of fixation alone in B1- (55/78; 71%) and C-type (49/65; 75%) fractures. Cemented stem fixation (odds ratio (OR) 2.66 (95% confidence interval (CI) 1.42 to 4.99); p = 0.002) and B2/B3 fracture type (OR 7.56 (95% CI 4.14 to 13.78); p < 0.001) were predictors of operative management. The median length of stay was 15 days (IQR 9 to 23), 12-month reoperation rate was 5.6% (n = 30), and 30-day readmission rate was 8.4% (n = 45). The 30-day and 12-month mortality rates were 5.2% (n = 28) and 21.0% (n = 113). Nonoperative treatment, older age, male sex, admission from residential or nursing care, and sustaining the PPF around a revision prosthesis were significant predictors of an increased 12-month mortality. Conclusion Femoral hip PPFs have mortality, reoperation, and readmission rates comparable with hip fracture patients. However, they have a longer wait for surgery, and surgical treatment is more complex. There is a need to create a national framework for data collection for this heterogeneous group of patients in order to understand the outcomes of different approaches to treatment

Epidemiology and characteristics of femoral periprosthetic fractures: data from the characteristics, outcomes and management of periprosthetic fracture service evaluation (COMPOSE) cohort study

Aims The aim of this study was to describe the demographic details of patients who sustain a femoral periprosthetic fracture (PPF), the epidemiology of PPFs, PPF characteristics, and the predictors of PPF types in the UK population. Methods This is a multicentre retrospective cohort study including adult patients presenting to hospital with a new PPF between 1 January 2018 and 31 December 2018. Data collected included: patient characteristics, comorbidities, anticoagulant use, social circumstances, level of mobility, fracture characteristics, Unified Classification System (UCS) type, and details of the original implant. Descriptive analysis by fracture location was performed, and predictors of PPF type were assessed using mixed-effects logistic regression models. Results In total, 720 femoral PPFs from 27 NHS sites were included. PPF patients were typically elderly (mean 79.9 years (SD 10.6)), female (n = 455; 63.2%), had at least one comorbidity (n = 670; 93.1%), and were reliant on walking aids or bed-/chair-bound prior to admission (n = 419; 61.7%). The study population included 539 (74.9%) hip PPFs, 151 (21.0%) knee PPFs, and 30 (4.2%) dividing type PPFs. For hip (n = 407; 75.5%) and knee (n = 88; 58.3%) arthroplasty UCS B type fractures were most common. Overall, 556 (86.2%) were treated in the presenting hospital and 89 (13.8%) required transfer for treatment. Female sex was the only significant predictor of fracture type (A/B1/C type versus B2/B3) for femoral hip PPFs (odds ratio 0.61 (95% confidence interval 0.41 to 0.91); p = 0.014). Sex, residence type, primary versus revision implant PPF, implant fixation, and time between arthroplasty and PPF were not found to predict fracture type for hip PPFs. Conclusion This multicentre analysis describes patient and injury factors for patients presenting with femoral PPFs to centres across the UK. These patients are generally elderly and frail, comparable to those sustaining a hip fracture. These data can be useful in planning future services and clinical trials