Interleukin-6 trans-signaling and pathological low back pain in patients with Paget disease of bone

Modulation of TRPV4 protects against degeneration induced by sustained loading and promotes matrix synthesis in the intervertebral disc

While it is well known that mechanical signals can either promote or disrupt intervertebral disc (IVD) homeostasis, the molecular mechanisms for transducing mechanical stimuli are not fully understood. The transient receptor potential vanilloid 4 (TRPV4) ion channel activated in isolated IVD cells initiates extracellular matrix (ECM) gene expression, while TRPV4 ablation reduces cytokine production in response to circumferential stretching. However, the role of TRPV4 on ECM maintenance during tissue-level mechanical loading remains unknown. Using an organ culture model, we modulated TRPV4 function over both short- (hours) and long-term (days) and evaluated the IVDs' response. Activating TRPV4 with the agonist GSK101 resulted in a Ca²⁺ flux propagating across the cells within the IVD. Nuclear factor (NF)-κB signaling in the IVD peaked at 6 h following TRPV4 activation that subsequently resulted in higher interleukin (IL)-6 production at 7 days. These cellular responses were concomitant with the accumulation of glycosaminoglycans and increased hydration in the nucleus pulposus that culminated in higher stiffness of the IVD. Sustained compressive loading of the IVD resulted in elevated NF-κB activity, IL-6 and vascular endothelial growth factor A (VEGFA) production, and degenerative changes to the ECM. TRPV4 inhibition using GSK205 during loading mitigated the changes in inflammatory cytokines, protected against IVD degeneration, but could not prevent ECM disorganization due to mechanical damage in the annulus fibrosus. These results indicate TRPV4 plays an important role in both short- and long-term adaptations of the IVD to mechanical loading. The modulation of TRPV4 may be a possible therapeutic for preventing load-induced IVD degeneration.

Changes in serum angiogenic factors among patients with acute pain and subacute pain

Screening serum biomarkers for acute and subacute pain is important for precise pain management. This study aimed to examine serum levels of angiogenic factors in patients with acute and subacute pain as potential biomarkers. Serum samples were collected from 12 healthy controls, 20 patients with postherpetic neuralgia (PHN), 4 with low back pain (LBP), and 1 with trigeminal neuralgia (TN). Pain intensity in these patients was evaluated using the visual analog scale (VAS). The serum concentrations of 11 angiogenic biomarkers were examined by Milliplex Map Human Angiogenesis Magnetic Bead Panel 2. The pain assessment from VAS showed that all patients showed moderate and severe pain. Among 11 angiogenic factors, osteopontin (OPN), thrombospondin-2 (TSP-2), soluble platelet endothelial cell adhesion molecule-1 (sPECAM-1), soluble urokinase-type plasminogen activator receptor (suPAR), and soluble epidermal growth factor receptors (sErbB2) were up-regulated and soluble interleukin-6 receptor α (sIL-6Rα) were down-regulated in patients with pain compared to the healthy participants (all P-values were < 0.005). Moreover, a linear regression model showed that the serum OPN concentration was correlated with pain intensity in patients with PHN (P = 0.03). There was no significant difference between the serum concentration of soluble epidermal growth factor receptors, sErbB3, soluble AXL, tenascin, and soluble neuropilin-1 in patients with acute and subacute pain and that of healthy controls. The results of this study provided new valuable insights into our understanding of angiogenic factors that may contribute to as mechanistic biomarkers of pain, and reveal the pathophysiological mechanism of pain.

Clinical Trial Registration:www.chictr.org.cn, identifier ChiCTR2200061775.

Preventive Role of Vitamin D Supplementation for Acute Phase Reaction after Bisphosphonate Infusion in Paget's Disease

CONTEXT

Intravenous aminobisphosphonates (N-BPs) can induce an acute phase reaction (APR) in up to 40% to 70% of first infusions, causing discomfort and often requiring intervention with analgesics or antipyretics.

OBJECTIVE

Our aim was to explore the risk factors of APR in a large sample of patients with Paget's disease of bone (PDB) and to assess the possible preventive effects of vitamin D administration.

METHODS

An observational analysis was performed in 330 patients with PDB at the time of N-BP infusion. Then, an interventional study was performed in 66 patients with active, untreated PDB to evaluate if vitamin D administration (oral cholecalciferol 50 000 IU/weekly for 8 weeks before infusion) may prevent APR.

RESULTS

In a retrospective study, APR occurred in 47.6% and 18.3% of naive or previously treated patients, respectively. Its prevalence progressively increased in relation to the severity of vitamin D deficiency, reaching 80.0% in patients with 25-hydroxyvitamin D (25OHD) levels below 10 ng/mL (relative risk (RR) = 3.7; 95% confidence interval (CI) 2.8-4.7, P < .0001), even in cases previously treated with N-BPs. Moreover, APR occurred more frequently in patients who experienced a previous APR (RR = 2.8; 95% CI 1.5-5.2; P < .001) or in carriers of SQSTM1 mutation (RR = 2.3; 95% CI 1.3-4.2; P = .005). In the interventional study, vitamin D supplementation prevented APR in most cases, equivalent to a RR of 0.31 (95% CI 0.14-0.67; P < .005) with respect to prevalence rates of the observational cohort. A similar trend was observed concerning the occurrence of hypocalcemia.

CONCLUSIONS

The achievement of adequate 25OHD levels is recommended before N-BP infusion in order to minimize the risk of APR or hypocalcemia in PDB.

Vitamin D Status in Paget Disease of Bone and Efficacy-Safety Profile of Cholecalciferol Treatment in Pagetic Patients with Hypovitaminosis D

Adequate vitamin D status is essential for skeletal health. Paget's disease of bone (PDB) is a common metabolic skeletal disorder, but data regarding the vitamin D status in PDB patients are lacking. We performed a case-control study to estimate vitamin D status in 708 PDB patients and in 1803 healthy controls from Italy and an observational prospective study to evaluate the efficacy-safety profile of oral cholecalciferol treatment [400.000 International Units (UI) of cholecalciferol administered in cycles of 8 weeks until 25OHD levels reaches 70 nmol/L as primary therapy and 50.000 UI of cholecalciferol administered every 2 weeks for 52 weeks for the maintenance therapy] in 82 PDB patients with hypovitaminosis D, i.e., 25OHD < 50 nmol/L. The main outcome measures for the prospective study were 25OHD levels, metabolic risk factors (RF) for nephrolithiasis, bone pain score (BPS), and pain medication score (PMS). Over half of PDB patients had hypovitaminosis D. Among PDB patients treated with cholecalciferol, 76 patients reached 25OHD levels ≥ 70 nmol/L after the first cycle of primary therapy and the remaining six patients after a second cycle. The maintenance therapy guaranteed 25OHD levels ≥ 70 nmol/L during the entire follow-up. The increase in 25OHD levels reduced PTH, BPS, and PMS levels, without changes in RF for nephrolithiasis. We can conclude that (i) hypovitaminosis D is frequent in PDB patients, (ii) cholecalciferol significantly increased 25OHD levels in PDB patients, and (iii) the correction of hypovitaminosis D improves the quality of life of PDB patients without inducing significant changes in RF for nephrolithiasis.