STUDY DESIGN: Experimental human study. PURPOSE: To determine whether angiopoietin-like protein 2 (ANGPTL2) is highly expressed in the hyperplastic facet joint (FJ) synovium and whether it activates interleukin-6 (IL-6) secretion in FJ synoviocytes. OVERVIEW OF LITERATURE: Mechanical stress-induced synovitis is partially, but significantly, responsible for degenerative and subsequently osteoarthritic changes in the FJ tissues in patients with lumbar spinal stenosis (LSS). However, the underlying molecular mechanism remains unclear. IL-6 is highly expressed in degenerative FJ synovial tissue and is responsible for local chronic inflammation. ANGPTL2, an inflammatory and mechanically induced mediator, promotes the expression of IL-6 in many cells. METHODS: FJ tissues were harvested from five patients who had undergone lumbar surgery. Immunohistochemistry for ANGPTL2, IL-6, and cell markers was performed in the FJ tissue samples. After cultured synoviocytes from the FJ tissues were subjected to mechanical stress, ANGPTL2 expression and secretion were measured quantitatively using real-time quantitative reverse-transcription–polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA), respectively. Following ANGPTL2 administration in the FJ synoviocytes, anti-nuclear factor-κB (NF-κB) activation was investigated using immunocytochemistry, and IL-6 expression and secretion were assayed quantitatively with or without NF-κB inhibitor. Moreover, we assessed whether ANGPTL2-induced IL-6 modulates leucocyte recruitment in the degenerative process by focusing on the monocyte chemoattractant protein-1 (MCP-1) expression. RESULTS: ANGPTL2 and IL-6 were highly expressed in the hyperplastic FJ synovium samples. ANGPTL2 was co-expressed in both, fibroblast-like and macrophage-like synoviocytes. Further, the expression and secretion of ANGPTL2 in the FJ synoviocytes increased in response to stimulation by mechanical stretching. ANGPTL2 protein promoted the nuclear translocation of NF-κB and induced IL-6 expression and secretion in the FJ synoviocytes. This effect was reversed following treatment with NF-κB inhibitor. Furthermore, ANGPTL2-induced IL-6 upregulated the MCP-1 expression in the FJ synoviocytes. CONCLUSIONS: Mechanical stress-induced ANGPTL2 promotes chronic inflammation in the FJ synovium by activating IL-6 secretion, leading to FJ degeneration and subsequent LSS.
Chemokine CCL2 ; Enzyme-Linked Immunosorbent Assay ; Humans ; Immunohistochemistry ; Inflammation ; Interleukin-6 ; Spinal Stenosis ; Stress, Mechanical ; Synovial Membrane ; Synovitis ; Zygapophyseal Joint

  Background: Heat shock proteins (Hsps), expression of which are induced by thermal treatment, function in the protection of kidneys by suppressing apoptosis and maintaining renal tubular viability. Moreover, recently, it has been indicated that the expression of Hsps can be a therapeutic target for autosomal dominant polycystic kidney disease (ADPKD). We investigated the effect of dry sauna therapy on ADPKD model mice.  Methods and Results: The mice (male DBA/2FG-pcy mice) were categorized into three groups: controls, TS: pcy mice subjected to prolonged sauna with administered water containing 4% sucrose, SW: pcy mice administered water containing 4% sucrose. The TS group was subjected to sauna sessions twice a week for four weeks. The TS group attained and were maintained at rectal temperatures of approximately 39.0°C, until they were carefully removed from the far infrared-ray device. After 4 weeks of sauna treatment, creatinine and blood-urea-nitrogen (BUN) levels determined by an enzymatic method. The heat shock protein (HSP) or cell growth and size related proteins were analyzed by western blotting. The TS group exhibited marginally higher creatinine and BUN levels than did the control and SW groups, however, the differences were not significant. However, cyst enlargement in the TS group reduced significantly compared to that of the control group. HSP90 expression was slightly decreased in the TS and SW groups relative to the control group (p < 0.01 or p < 0.001, vs. control), as was Erk expression, which is linked to cyst development and proliferation (p < 0.05, TS vs. control). Hsp27 expression and phosphorylation level in the SW group were comparable with that of the control group. However, the TS group had increased levels of Hsp27 and phosphorylation (NS). The expression of pro-caspase-3 in the TS group was marginally lower than that in the control group. However, the activity of caspase-3 in all groups showed no differences.  Conclusion: The findings of this study indicated that 4 weeks of sauna treatment could cause transient dehydration and related renal dysfunction and led to the risk of stimulating cyst growth by increased Hsp27 expression. Moreover, we concluded that prevention of dehydration and cyst growth could be suppressed by taking an appropriate amount of water directly after sauna treatment.

  Background: Heat shock proteins (Hsps), expression of which are induced by thermal treatment, function in the protection of kidneys by suppressing apoptosis and maintaining renal tubular viability. Moreover, recently, it has been indicated that the expression of Hsps can be a therapeutic target for autosomal dominant polycystic kidney disease (ADPKD). We investigated the effect of dry sauna therapy on ADPKD model mice.  Methods and Results: The mice (male DBA/2FG-pcy mice) were categorized into three groups: controls, TS: pcy mice subjected to prolonged sauna with administered water containing 4% sucrose, SW: pcy mice administered water containing 4% sucrose. The TS group was subjected to sauna sessions twice a week for four weeks. The TS group attained and were maintained at rectal temperatures of approximately 39.0°C, until they were carefully removed from the far infrared-ray device. After 4 weeks of sauna treatment, creatinine and blood-urea-nitrogen (BUN) levels determined by an enzymatic method. The heat shock protein (HSP) or cell growth and size related proteins were analyzed by western blotting. The TS group exhibited marginally higher creatinine and BUN levels than did the control and SW groups, however, the differences were not significant. However, cyst enlargement in the TS group reduced significantly compared to that of the control group. HSP90 expression was slightly decreased in the TS and SW groups relative to the control group (p < 0.01 or p < 0.001, vs. control), as was Erk expression, which is linked to cyst development and proliferation (p < 0.05, TS vs. control). Hsp27 expression and phosphorylation level in the SW group were comparable with that of the control group. However, the TS group had increased levels of Hsp27 and phosphorylation (NS). The expression of pro-caspase-3 in the TS group was marginally lower than that in the control group. However, the activity of caspase-3 in all groups showed no differences.  Conclusion: The findings of this study indicated that 4 weeks of sauna treatment could cause transient dehydration and related renal dysfunction and led to the risk of stimulating cyst growth by increased Hsp27 expression. Moreover, we concluded that prevention of dehydration and cyst growth could be suppressed by taking an appropriate amount of water directly after sauna treatment.