Basic calcium phosphate crystals activate human osteoarthritic synovial fibroblasts and induce matrix metalloproteinase-13 (collagenase-3) in adult porcine articular chondrocytes

Objective-To determine the ability of basic calcium phosphate (BCP) crystal s to induce (a) mitogenesis, matrix metalloproteinase (MMP)-1, and MMP-13 i n human osteoarthritic synovial fibroblasts (HOAS) and (b) MMP-13 in cultur ed porcine articular chondrocytes. Methods-Mitogenesis of HOAS was measured by [H-3]thymidine incorporation as say and counts of cells in monolayer culture. MMP messenger RNA (mRNA) accu mulation was determined either by northern blot analysis or reverse transcr iptase-polymerase chain reaction (RT-PCR) of RNA from chondrocytes or HOAS treated with ECP crystals. MMP-13 secretion was identified by immunoprecipi tation and MMP-1 secretion by western blot of conditioned media. Results-BCP crystals caused a 4.5-fold increase in [H-3]thymidine incorpora tion by HOAS within 20 hours compared with untreated control cultures (p le ss than or equal to0.05). BCP crystals induced MMP-13 mRNA accumulation and MMP-13 protein secretion by articular chondrocytes. In contrast, in HOAS, MMP-13 mRNA induced by BCP crystals was detectable only by RT-PCR, and MMP- 13 protein was undetectable. Division of and MMP-13 protein was undetectabl e. BCP crystals induced MMP-1 mRNA accumulation and MMP-1 protein secretion by HOAS. MMP-1 expression was further augmented when HOAS were co-incubate d with either ECP and tumour necrosis factor alpha (TNF alpha; threefold) o r BCP and interleukin 1 alpha (IL1 alpha; twofold). Conclusion-These data confirm the ability of BCP crystals to activate HOAS, leading to the induction of mitogenesis and MMP-1 production. MMP-13 produ ction in response to ECP crystals is substantially more detectable in porci ne articular chondrocytes than in HOAS. These data support the active role of BCP crystals in osteoarthritis and suggest that BCP crystals act synergi stically with IL1 alpha and TNFa. to promote A MMP production and subsequen t joint degeneration.