In vitro spontaneous osteoclastogenesis of human peripheral blood mononuclear cells is not crucially dependent on T lymphocytes

Abstract

Objective. In vitro spontaneous osteoclastogenesis from peripheral blood mononuclear cells (PBMCs) is increased in diseases with excessive bone loss. The purpose of this study was to reassess the role of T lymphocytes in this process.Methods. Fresh or cryopreserved PBMCs obtained from healthy subjects and from patients with rheumatoid arthritis, psoriatic arthritis, and nonpsoriatic spondylarthritis were cultured at high density and stained for tartrate-resistant acid phosphatase (TRAP). Resorption of mineralized matrix was assessed by a dentin disc assay. CD14؉ monocytes and CD3؉ T cells were selected using magnetically labeled antibodies.Results. Numerous multinucleated, TRAP؉, dentin-resorbing osteoclasts developed spontaneously from fresh PBMCs from healthy individuals. This process was abrogated by T cell depletion and was restored by exogenous macrophage colony-stimulating factor (M-CSF) and RANKL, indicating the important role of T cells in spontaneous osteoclastogenesis in vitro. Using physiologic freezing and thawing as a model for the activation of PBMCs, spontaneous osteoclastogenesis was significantly increased in cryopreserved versus fresh cells. Under these conditions, spontaneous osteoclastogenesis was not dependent on T lymphocytes, since it was not influenced by T cell depletion and persisted in purified CD14؉ cell cultures supplemented with M-CSF and RANKL. In contrast to studies with fresh PBMCs, spontaneous osteoclastogenesis under these conditions did not appear to be clearly different between healthy subjects and patients with arthritis.Conclusion. Spontaneous osteoclastogenesis in vitro is dependent on T lymphocytes or on the direct activation of monocytic cells, depending on the test conditions. This variability warrants better validation of the relevance of this functional test for in vivo osteoclastogenesis.

Natural killer cells trigger osteoclastogenesis and bone destruction in arthritis

“…2A and 4B) suggests that osteoclasts can appear spontaneously, an observation in line with previous studies (28,29).…”

Potassium citrate prevents increased osteoclastogenesis resulting from acidic conditions: Implication for the treatment of postmenopausal bone loss

“…A spontaneous osteoclastogenesis has been observed in all cultures without differentiating stimuli [31], but it was not influenced by the acidity of culture medium. On the contrary, the low pH fostered the activity of pro-osteoclastogenic factors and promoted the OC differentiation.…”

“…Since all the above genes are down-regulated in presence of K citrate, it is reasonable to hypothesize that the partial neutralization obtained with the compound may hamper osteoclastogenesis through the “switch off” of the Ca 2+ /calcineurin/NFATc1 pathway. The alkalizing activity of K citrate might reduce the activation of the acid-sensing receptors identified on the plasma membrane of OC, including ovarian cancer G-protein-coupled receptor 1 (OGR1) [46,47], T cell death-associated gene 8 (TDAG8) [48], transient receptor potential (TRP) family members [31,33], and the acid-sensitive ion channel (ASIC) subunits [42,49]. All the above mentioned molecules increase intracellular Ca 2+ , thus favoring the NFATc1 activation and OC differentiation [34].…”

The Multifaceted Osteoclast; Far and Beyond Bone Resorption

“…Circulating osteoclast precursors were initially identified as biomarkers for erosive disease in psoriatic arthritis patients, in rheumatoid arthritis, spondyloarthritis, and osteoporosis [Ritchlin et al, 2003;Vandooren et al, 2009]. Conversely, the loss of circulating osteoclast precursors has been correlated with non-erosive inflammatory arthritis [Schwarz et al, 2006].…”