Cartilage stem/progenitor cells are activated in osteoarthritis via interleukin-1β/nerve growth factor signaling

Abstract

IntroductionInterleukin-1β (IL-1β) and nerve growth factor (NGF) are key regulators in the pathogenesis of inflammatory arthritis; specifically, IL-1β is involved in tissue degeneration and NGF is involved in joint pain. However, the cellular and molecular interactions between IL-1β and NGF in articular cartilage are not known. Cartilage stem/progenitor cells (CSPCs) have recently been identified in osteoarthritic (OA) cartilage on the basis of their migratory properties. Here we hypothesize that IL-1β/NGF signaling is involved in OA cartilage degeneration by targeting CSPCs.MethodNGF and NGF receptor (NGFR: TrkA and p75NTR) expression in healthy and OA human articular cartilage and isolated chondrocytes was determined by immunostaining, qRT-PCR, flow cytometry and western blot. Articular cartilage derived stem/progenitor cells were collected and identified by stem/progenitor cell characteristics. 3D-cultured CSPC pellets and cartilage explants were treated with NGF and NGF neutralizing antibody, and extracellular matrix changes were examined by sulfated glycosaminoglycan (GAG) release and MMP expression and activity.ResultsExpression of NGF, TrkA and p75NTR was found to be elevated in human OA cartilage. Cellular changes upon IL-1β and/or NGF treatment were then examined. NGF mRNA and NGFR proteins levels were upregulated in cultured chondrocytes exposed to IL-1β. NGF was chemotactic for cells isolated from OA cartilage. Cells isolated on the basis of their chemotactic migration towards NGF demonstrated stem/progenitor cell characteristics, including colony-forming ability, multi-lineage differentiation potential, and stem cell surface markers. The effects of NGF perturbation in cartilage explants and 3D-cultured CSPCs were next analyzed. NGF treatment resulted in extracellular matrix catabolism indicated by increased sGAG release and MMP expression and activity; conversely, treatment with NGF neutralizing antibody inhibited increased MMP levels, and enhanced tissue inhibitor of matrix metalloprotease-1 (TIMP1) expression in OA cartilage explants. NGF blockade with neutralizing antibody also affected cartilage matrix remodeling in 3D-CSPC pellet cultures.ConclusionOur results strongly suggest that NGF signaling is a contributing factor in articular cartilage degeneration in OA, which likely targets a specific subpopulation of progenitor cells, the CSPCs, affecting their migratory and matrix remodeling activities. These findings provide novel cellular/signaling therapeutic targets in osteoarthritic cartilage.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0840-x) contains supplementary material, which is available to authorized users.

Role of NGF‐TrkA signaling in calcification of articular chondrocytes

“…Nerve growth is observed in human OA joints, and NGF is known to be involved in neuropathic pain transmission (26,27); however, it is not clear whether NGF plays a role in joint degeneration. Our group has recently found that expression of NGF and NGFRs in OA cartilage is associated with a subpopulation of tissue-specific stem and progenitor cells in vivo and can be regulated by the OA mediator IL-1b (18). The in vitro findings reported here provide further evidence supporting the functional involvement of NGF-NGFR signaling in OA pathogenesis, specifically suggesting a role in hACs homeostasis and pathologic calcification.…”

“…Other groups and our recent findings strongly implicated the involvement of NGF-and NGF receptor (NGFR)mediated signaling in OA pathogenesis in cartilage, evidenced by the active presence of the high-affinity NGFR tropomyosin receptor kinase A (TrkA) and low-affinity NGFRs [P75 neurotrophin receptor (P75NTR), CD271] in human OA cartilage (16,17) and the elevation of NGF expression in cultured chondrocytes induced by the OA mediator and proinflammatory cytokine IL-1b (18). In addition, a population of NGF-responsive migratory progenitor cells has been identified in OA cartilage (18,19). However, the exact function of NGF and NGFR in articular cartilage biology and OA pathogenesis remains to be clarified.…”

“…The responsiveness of primary hACs to NGF signaling was next investigated. Healthy hACs showed little to no expression of NGFRs (including both TrkA and P75NTR); however, in OA cartilage, NGFR-positive cells became abundant (18). We have previously shown that the proinflammatory OA mediator IL-1b enhanced the expression of NGF and NGFR in cultured human chondrocytes (18).…”

“…Healthy hACs showed little to no expression of NGFRs (including both TrkA and P75NTR); however, in OA cartilage, NGFR-positive cells became abundant (18). We have previously shown that the proinflammatory OA mediator IL-1b enhanced the expression of NGF and NGFR in cultured human chondrocytes (18). We therefore postulated that articular chondrocytes have the potential to respond to NGF given the emergence of NGFRs.…”

Chondrocytes from congenital microtia possess an inferior capacity for in vivo cartilage regeneration to healthy ear chondrocytes

“…The chondrogenic potential of chondrocytes has been reported to have a negative correlation with cell migration ability in a two‐dimensional cell migration assay (O'Connell et al ., ). Others using articular chondrocytes have also found the important role of cell migration in cartilage catabolism (Pereira et al ., ; Jiang et al ., ). Our results demonstrated that the weaker chondrogenic phenotype in P 1 healthy chondrocyte was accompanied with its stronger migration ability and increased expression of stemness‐related genes, which further confirmed the faster dedifferentiation potential in healthy ear chondrocytes than in microtia.…”