Pro-inflammatory effects of human apatite crystals extracted from patients suffering from calcific tendinopathy

Imaging of Rotator Cuff Calcific Tendinopathy Using 18 F-NaF and 18 F-FDG PET/CT

ABSTRACT

Calcific tendinopathy is a common condition of the shoulder caused by the inflammation and deposition of hydroxyapatite crystals in the rotator cuff tendons. PET tracers capturing the molecular changes associated with the crystal deposition of calcific tendinopathy remain underinvestigated. In this report, we present calcified tendinopathy of the infraspinatus tendon demonstrating both 18 F-NaF and 18 F-FDG focal uptake in a 61-year-old woman.

Mechanical overload-induced release of extracellular mitochondrial particles from tendon cells leads to inflammation in tendinopathy

Tendinopathy is one of the most common musculoskeletal diseases, and mechanical overload is considered its primary cause. However, the underlying mechanism through which mechanical overload induces tendinopathy has not been determined. In this study, we identified for the first time that tendon cells can release extracellular mitochondria (ExtraMito) particles, a subtype of medium extracellular particles (mEPs), into the environment through a process regulated by mechanical loading. RNA sequencing systematically revealed that oxygen-related reactions, extracellular particles, and inflammation were present in diseased human tendons, suggesting that these factors play a role in the pathogenesis of tendinopathy. We simulated the disease condition by imposing a 9% strain overload on three-dimensional mouse tendon constructs in our cyclic uniaxial stretching bioreactor. The three-dimensional mouse tendon constructs under normal loading with 6% strain exhibited an extended mitochondrial network, as observed through live-cell confocal laser scanning microscopy. In contrast, mechanical overload led to a fragmented mitochondrial network. Our microscopic and immunoblot results demonstrated that mechanical loading induced tendon cells to release ExtraMito particles. Furthermore, we showed that mEPs released from tendon cells overloaded with a 9% strain (mEP9%) induced macrophage chemotaxis and increased the production of proinflammatory cytokines, including IL-6, CXCL1, and IL-18, from macrophages compared to mEP0%, mEP3%, and mEP6%. Partial depletion of the ExtraMito particles from mEP9% by magnetic-activated cell sorting significantly reduced macrophage chemotaxis. N-acetyl-L-cysteine treatment preserved the mitochondrial network in overloaded tendon cells, diminishing overload-induced macrophage chemotaxis toward mEP9%. These findings revealed a novel mechanism of tendinopathy; in an overloaded environment, ExtraMito particles convey mechanical response signals from tendon cells to the immune microenvironment, culminating in tendinopathy.

Hydroxyapatite deposition disease (HADD) of the spring ligament: an unusual cause of medial foot pain

Foot pain is one of the most common presenting complaints in orthopaedic clinical practice and can be attributed to a multitude of pathologies in the various osseous structures, ligaments, and tendons of the foot. The spring ligament complex (SLC) between the calcaneum and navicular supports the talus and plays a major role in the static stability of the medial longitudinal arch of the foot. Although calcific ligamentous enthesopathy around the ankle has been described in the literature, we report the first case of its kind affecting the SLC in a 51-year-old male with medial foot pain and no history of trauma. We highlight the role of radiological interventions in the diagnosis and effective management using ultrasound (US)-guided barbotage.

Gastric epithelial response to milk fat using the semi-dynamic INFOGEST digestion model coupled with NCI-N87 cells

The stomach is a relevant spot of lipolysis for milk fat, but research on the effect of digested milk fat in the gastric epithelium is scarce and difficult to evaluate. In the present study, we implemented the semi-dynamic in vitro digestion model of INFOGEST, combined with gastric NCI-N87 cells, to study the effect of fat-free, whole conventional, and whole pasture-based milk on gastric epithelium. Cellular messenger ribonucleic acid (mRNA) expression of membrane fatty acids receptors (GPR41, GPR84), antioxidant enzymes (CAT, SOD, GPX), and inflammatory molecules (NF-κB p65, IL-1β, IL-6, IL-8 and TNF-α) was assessed. No significant differences were observed in mRNA expression of GPR41, GPR84, SOD, GPX, IL-6, IL-8, and TNF-α, after exposure of the NCI-N87 cells to milk digesta samples (p > 0.05). An increase of CAT mRNA expression was observed (p < 0.05), at a similar level, for all milk types. Whole milk digested samples induced higher mRNA expression of NF-κB p65 and IL-1β than fat-free milk (p < 0.05); while no differences were observed between whole conventional and whole pasture-based milk (p > 0.05). Moreover, the effect of milk digesta on gastric mRNA expression was studied in a scenario of subsequent stimulation of NCI-N87 monolayer with the pro-inflammatory cytokine IFN-γ. In these conditions, milk digesta samples increased CAT mRNA expression (p < 0.05), but had no effect in the expression of NF-κB p65 and IL-1β (p > 0.05). The increase of CAT mRNA expression suggests that milk fatty acids are used for energy production by gastric epithelial cells. Cellular antioxidant response to higher milk fatty acids availability could be associated to gastric epithelial inflammation, but did not contribute to increased inflammation in case of an external contact with IFN-γ. Besides, a conventional or a pasture-based origin did not affect the impact of whole milk in the NCI-N87 monolayer. The combined model responded to differences in milk fat content, which indicates its usefulness to study effects of foods at the gastric level.

Macrophage metabolic profile is altered by hydroxyapatite particle size

Since the recent observation that immune cells undergo metabolic reprogramming upon activation, there has been immense research in this area to not only understand the basis of such changes, but also to exploit metabolic rewiring for therapeutic benefit. In a resting state, macrophages preferentially utilise oxidative phosphorylation to generate energy; however, in the presence of immune cell activators, glycolytic genes are upregulated, and energy is generated through glycolysis. This facilitates the rapid production of biosynthetic intermediates and a pro-inflammatory macrophage phenotype. While this is essential to mount responses to infectious agents, more evidence is accumulating linking dysregulated metabolism to inappropriate immune responses. Given that certain biomaterials are known to promote an inflammatory macrophage phenotype, this prompted us to investigate if biomaterial particulates can impact on macrophage metabolism. Using micron and nano sized hydroxyapatite (HA), we demonstrate for the first time that these biomaterials can indeed drive changes in metabolism, and that this occurs in a size-dependent manner. We show that micronHA, but not nanoHA, particles upregulate surrogate markets of glycolysis including the glucose transporter (GLUT1), hexokinase 2 (HK2), GAPDH, and PKM2. Furthermore, we demonstrate that micronHA alters mitochondrial morphology and promotes a bioenergetic shift to favour glycolysis. Finally, we demonstrate that glycolytic gene expression is dependent on particle uptake and that targeting glycolysis attenuates the pro-inflammatory profile of micronHA-treated macrophages. These results not only further our understanding of biomaterial-based macrophage activation, but also implicate immunometabolism as a new area for consideration in intelligent biomaterial design and therapeutic targeting. STATEMENT OF SIGNIFICANCE: Several recent studies have reported that immune cell activation occurs concurrently with metabolic reprogramming. Furthermore, metabolic reprogramming of innate immune cells plays a prominent role in determining cellular phenotype and function. In this study we demonstrate that hydroxyapatite particle size alters macrophage metabolism, in turn driving their functional phenotype. Specifically, the pro-inflammatory phenotype promoted by micron-sized HA-particles is accompanied by changes in mitochondrial dynamics and a bioenergetic shift favouring glycolysis. This effect is not seen with nano-HA particles and can be attenuated upon inhibition of glycolysis. This study therefore not only identifies immunometabolism as a useful tool for characterising the immune response to biomaterials, but also highlights immunometabolism as a targetable aspect of the host response for therapeutic benefit.

Basic calcium phosphate crystals induce the expression of extracellular matrix remodelling enzymes in tenocytes

OBJECTIVES

Basic calcium phosphate (BCP) crystals contribute to several syndromes associated with tendon disease, including acute calcific tendinitis and Milwaukee shoulder syndrome. Interactions between BCP crystals and tenocytes (tendon cells) may contribute to these clinical syndromes. This study aimed to determine the direct effects of BCP crystals on tenocyte function and viability.

METHODS

In vitro assays were used to assess changes in human tenocytes cultured with BCP crystals. Real-time PCR was used to determine changes in the expression of tendon-related genes and extracellular matrix remodelling enzymes (MMPs; a disintegrin and metalloproteases, ADAMTS; and tissue inhibitor of metalloproteinases, TIMPs). ELISA was used to measure protein concentrations in tenocyte supernatants. MTT and alamarBlue™ assays were used to determine changes in cell viability.

RESULTS

BCP crystals upregulated tenocyte gene expression of MMP-1, MMP-3, ADAMTS-4 and TIMP-1 after 24 h. Time-course experiments showed expression peaked at 8 h for TIMP-1 and 48 h for MMP-1 and ADAMTS-4. Cyclooxygenase (COX)-1 gene expression was upregulated after 48 h. Tenocytes did not alter expression of scleraxis and tendon collagens, and expression of pro-inflammatory cytokines was not induced with BCP crystals. BCP crystals increased tenocyte release of prostaglandin E2 (PGE2) and MMP-1 protein after 24 h. However, neither COX-1 inhibition nor COX-2 inhibition led to consistent change in BCP crystal-induced tenocyte gene expression of extracellular matrix remodelling enzymes. BCP crystals had no effect on tenocyte viability.

CONCLUSION

BCP crystals induce extracellular matrix remodelling enzymes, but not inflammatory cytokines, in tenocytes.

Calcific tendinopathy of the pronator quadratus muscle: A rare site and cause of ulnar sided wrist pain

Ulnar -sided wrist pain is a common complaint and can present a diagnostic challenge for a musculoskeletal clinician. Calcific tendinopathy is a well-recognised disorder related to the deposition of calcium hydroxyapatite crystals within tendons. Classically, tendons around the shoulder and the hip joints are the most commonly affected sites. We report a rare site of calcific tendinopathy of the Pronator Quadratus muscle presenting with ulnar-sided wrist pain in a 36-year-old male posing a diagnostic dilemma. This case-report highlights the importance of a thorough clinical evaluation and crucial role of cross-sectional imaging in reaching a diagnosis of calcific tendinopathy of the Pronator Quadratus muscle as unusual cause of ulnar-sided wrist pain. This is the first reported case of calcific tendinopathy in pronator quadratus in the literature we could review.

Efficacy of Ultrasound-Guided Percutaneous Lavage and Biocompatible Electrical Neurostimulation, in Calcific Rotator Cuff Tendinopathy and Shoulder Pain, A Prospective Pilot Study

Calcific tendinopathy of the shoulder (CTS) is the most common cause of shoulder pain. Conservative treatment is considered as the first therapeutic choice for CTS. The main objective of this study was to assess the effect of US-guided needling (UGN) compared to UGN plus Biocompatible Electrical Neurostimulation (BEN) in the treatment of the CTS. Pilot, prospective, non-interventional, monocentric, and observational study of patients treated for calcific rotator cuff tendinopathy and shoulder pain. Patients’ selection, enrollment and interventions were conducted at the Chiparo Physical Medicine and Rehabilitation outpatient facility. Forty adult patients (aged 40−60 years) with a diagnosis of CTS in the acute and colliquative phase were recruited and enrolled into the study. Participants were assessed for self-perceived pain through the Numerical Rating Scale (NRS), and for functional limitation through the Shoulder Pain and Disability Index score (SPADI) at baseline (T0), after 15 days (T1), and after 40 days (T2). As a possible confounding factor between the two treatments’ response, the dimension of the tendon calcification was also assessed by US-examination. Through the study, both groups improved their perceived functional performance of the arm (p-value < 0.001). AT T1, the SPADI score decreased by half in both groups, and the improvement remained stable at T2. A multiplicative effect (Time × Treatment) was demonstrated (p-value < 0.001). An improvement in the NRS score was measured at T1, and it remained stable at T2, a multiplicative effect was also reported (p-value < 0.001). The main results of this pilot study provide evidence that UGN plus BEN increases functional performance and reduces shoulder pain in individuals with CTS. Moreover, the tendon calcification dimension at the baseline and the percentage of drainage of the lesion were associated with a functional performance recovery and pain reduction detected after intervention.