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Biodegradation of polycarbonate-based polyurethanes by the human monocytes-derived macrophage and U937 cell systems
Loren A Matheson1, Rosalind S Labow, J Paul Santerre
1University of Ottawa Heart Institute, University of Ottawa, 40 Ruskin Street, Ottawa, Ontario, Canada.
Abstract:
The prominent cell type found on implanted medical devices during the chronic inflammatory response is the monocyte-derived macrophage (MDM). Using an activated in vitro cell system, it was possible to show that MDMs possess esterolytic activities that may contribute to the degradation of polyurethanes. In the present study, the U937 cell line was paralleled to the MDM cell system in order to validate the use of a cell line that could expedite studies on biomaterial biocompatibility and biostability. Using 12-o-tetradecanoylphorbol 13-acetate (PMA), the optimum differentiation time for the U937 cells was 72 h based on biodegradation, degradative potential, and (35)S-methionine uptake. After activation of the cells by resuspending from tissue culture polystyrene plates and reseeding onto a (14)C-labeled polycarbonate-based polyurethane(PCNU), both U937 cells and the MDMs elicited comparable radiolabel release (measure of polymer breakdown) and esterase activity (measure of degradative potential) at 48 h. There was no difference in the effect on radiolabel release and esterase activity elicited by both cell types with inhibitors of protein synthesis, esterase activity, and phospholipase A(2). This established that both cell types likely used similar hydrolytic activities and signaling pathways to cause degradation of the PCNU. Immunoblotting demonstrated that both cell systems secreted monocyte-specific esterase and cholesterol esterase enzymes previously shown to degrade PCNUs. The U937 cell system is more convenient and reproducible than MDMs for pursuing possible biological pathways elucidating the mechanism of polyurethane biodegradation. Once established with U937s, the pathways can then be validated with the more physiologically relevant human MDM cell system.
Insights
Monocyte-derived macrophages (MDMs) degrade polyurethanes. The U937 cell line mimics MDM activity, offering a reproducible model for studying biomaterial degradation and biocompatibility.
Area of Science:
- Biomaterials Science
- Cell Biology
- Immunology
Background:
- Monocyte-derived macrophages (MDMs) are key cells involved in the inflammatory response to implanted medical devices.
- MDMs exhibit esterolytic activity, suggesting a role in polyurethane degradation.
- Biomaterial biocompatibility and biostability studies require reliable cell models.
Purpose of the Study:
- To validate the U937 cell line as a reproducible model for studying polyurethane biodegradation.
- To compare the degradative potential of U937 cells with primary MDMs.
- To elucidate the mechanisms of polyurethane degradation by immune cells.
Main Methods:
- U937 cells were differentiated using 12-o-tetradecanoylphorbol 13-acetate (PMA).
- Cells were cultured on (14)C-labeled polycarbonate-based polyurethane (PCNU) to assess polymer breakdown and esterase activity.
- Inhibitors of protein synthesis, esterase activity, and phospholipase A(2) were used to investigate degradation pathways.
- Immunoblotting was performed to identify secreted enzymes.
Main Results:
- Differentiated U937 cells showed comparable radiolabel release and esterase activity to MDMs when cultured on PCNU.
- Similar effects of inhibitors on both cell types indicated shared hydrolytic activities and signaling pathways.
- Both cell systems secreted monocyte-specific esterase and cholesterol esterase enzymes.
Conclusions:
- The U937 cell line serves as a convenient and reproducible model for studying polyurethane biodegradation.
- This cell line can expedite research into biomaterial biocompatibility and biostability.
- Findings support the use of U937 cells for initial pathway elucidation, followed by validation with human MDMs.