PhD defense: Ditte Reker

Investigating the Mode of Action Behind the Cartilage Regenerative Effect of Sprifermin (rhFGF18) Using Ex Vivo Models

Supervisors
Professor Martin W. Berchtold, BIO-UCPH
Associate Professor Anders Aspberg, Lund University
Dr. Anne-Christine Bay-Jensen, Head of Rheumatology, Nordic Bioscience

Committee
Professor Ingrid Meulenbelt, Leiden University Medical Center
Dr. Jan Talts, Longboat Explorers, SmiLe Incubator, Lund
Associate Professor Lotte Bang Pedersen, BIO-UCPH (chair)

Thesis abstract
Osteoarthritis (OA) is in urgent need of disease-modifying OA drugs, which modify the structural tissue changes driving the disease. Sprifermin (recombinant human fibroblast growth factor 18, rhFGF18) utilizes an anabolic approach to regenerate the degenerated articular cartilage of OA patients. We aimed to investigate the mode of action behind the cartilage regenerative effect of Sprifermin, using ex vivo models.

Ex vivo cultures of articular cartilage were stimulated with Sprifermin, FGF18, IGF-I (positive control) or placebo formulation (negative control). Pre-culturing with OSM and TNF-α was also used to induce an inflammatory state before treatment. Effects on metabolic activity (AlamarBlue), cell proliferation (PCNA staining), extracellular matrix (ECM) remodeling (ProC2, CS846, C2M, AGNx2, acMMP9 and AGNx1 biomarker release) and cartilage quality (COL1A1, COL2A1, ACAN and SOX9 gene expression, and Safranin O/Fast green staining) were monitored.

The ex vivo cartilage cultures confirmed the well-known anabolic effects of Sprifermin (increased cell proliferation, metabolic activity, and type II collagen and aggrecan formation), while revealing a novel catabolic effect (increased aggrecanase activity, but not MMP activity). A temporal biphasic

ECM remodeling process was observed during Sprifermin treatment, with an early catabolic phase followed by a late anabolic phase. The resulting cartilage quality was sustained, but not modulated by Sprifermin. Inflammatory pre-culturing of the cartilage prior to treatment altered the response to Sprifermin.

In conclusion, a temporal biphasic process of ECM remodeling was observed in articular cartilage ex vivo during Sprifermin-induced cartilage regeneration. Parallel chondrocyte proliferation and increased metabolic activity were indicative of a growing chondrocyte population. Finally, induction of an inflammatory state before treatment appeared to change the response to Sprifermin.