Sprifermin (rhFGF18) versus vehicle induces a biphasic process of extracellular matrix remodeling in human knee OA articular cartilage ex vivo

A. C. Bay-Jensen,C. S. Thudium,T. Gantzel,M. W. Berchtold,A. Aspberg,A. Gigout,C. Ladel,M. Michaelis,D. Reker,A. S. Siebuhr,M. A. Karsdal

doi:10.1038/s41598-020-63216-z

Abstract

Sprifermin, recombinant human fibroblast growth factor 18 (rhFGF18), induces cartilage regeneration in knees of patients with osteoarthritis (OA). We hypothesized that a temporal multiphasic process of extracellular matrix (ECM) degradation and formation underlie this effect. We aimed to characterize the temporal ECM remodeling of human knee OA articular cartilage in response to sprifermin treatment. Articular cartilage explants from patients with knee OA (npatients = 14) were cultured for 70 days, with permanent exposure to sprifermin (900, 450, 225 ng/mL), FGF18 (450 ng/mL), insulin-like growth factor-1 (100 ng/mL, positive control) or vehicle (nreplicates/treatment/patient = 2). Metabolic activity (AlamarBlue) and biomarkers of type IIB collagen (PIIBNP) formation (Pro-C2 enzyme-linked immunosorbent assay [ELISA]) and aggrecanase-mediated aggrecan neo-epitope NITEGE (AGNx1 ELISA) were quantified once a week. At end of culture (day 70), gene expression (quantitative reverse transcription polymerase chain reaction) and proteoglycan content (Safranin O/Fast green staining) were quantified. The cartilage had continuously increased metabolic activity, when treated with sprifermin/FGF18 compared to vehicle. During days 7–28 PIIBNP was decreased and NITEGE was increased, and during days 35–70 PIIBNP was increased. At end of culture, the cartilage had sustained proteoglycan content and relative expression of ACAN < COL2A1 < SOX9 < COL1A1, indicating that functional chondrocytes remained in the explants. Sprifermin induces a temporal biphasic cartilage remodeling in human knee OA articular cartilage explants, with early-phase increased aggrecanase activity and late-phase increased type II collagen formation.

Highlights

Sprifermin, recombinant human fibroblast growth factor 18, induces cartilage regeneration in knees of patients with osteoarthritis (OA)
This study demonstrated that chondrocytes could be reached and activated by sprifermin through the extracellular matrix (ECM) of the explant and identified two response biomarkers: PRO-C2, reflecting type II collagen formation, and AGNx1, reflecting aggrecanase-mediated aggrecan degradation
We investigated the effect of sprifermin on human OA cartilage and its ability to induce cartilage remodeling through a temporal multiphasic process of ECM degradation and ECM formation

Summary

Introduction

Sprifermin, recombinant human fibroblast growth factor 18 (rhFGF18), induces cartilage regeneration in knees of patients with osteoarthritis (OA). Sprifermin induces a temporal biphasic cartilage remodeling in human knee OA articular cartilage explants, with early-phase increased aggrecanase activity and late-phase increased type II collagen formation. The activation of FGFR3 induces proliferation, while maintaining the chondrogenic phenotype[10,11,12,13] It induces formation of extracellular matrix (ECM) molecules type II collagen and aggrecan[8,9,10,11,12,14]. This study demonstrated that chondrocytes could be reached and activated by sprifermin through the ECM of the explant and identified two response biomarkers: PRO-C2, reflecting type II collagen formation (the propeptide PIIBNP), and AGNx1, reflecting aggrecanase-mediated aggrecan degradation (the NITEGE fragment). Chondrocyte cultures (both monolayer and 3-dimensional) revealed an inverse linear correlation between proliferation and ECM formation, suggesting that chondrocytes cannot efficiently proliferate and produce ECM simultaneously[11]

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