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Polymorphonuclear cell apoptosis in exudates generated by polymers
1INSERM U-443, Université de Bordeaux II, 146 rue Leo-Saignat, 33076 Bordeaux Cedex, France.
Abstract:
Flow cytometry was used to quantify apoptotic and necrotic polymorphonuclear (PMN) cells in an exudate generated by biomaterials, and the results were compared with determinations of spontaneous apoptosis and necrosis in PMN cells from the bloodstream. The exudate formed inside cylindrical tubes subcutaneously implanted in the dorsal region of rats was collected over a 1-week period. A rapid and simple staining procedure based on the spectral properties of the bisbenzemide Hoechst 33342 was used to identify apoptotic PMN cells. Quantification of permeabilized PMN cells stained by propidium iodide was possible in the same unfixed specimens. The percentages of apoptotic and permeabilized PMN cells in peripheral rat blood were low (1.8 +/-0 0.5% and 1.7 +/- 0.7%, respectively), similar to results found in humans. In exudates generated by polyvinyl chloride (PVC), the percentages of apoptotic and permeabilized PMN cells were higher than in the blood. The percentage of PMN cells undergoing apoptosis progressively increased with time and reached a maximum at day 2 (27% +/- 6%). The percentage of permeabilized cells progressively increased with time and was much higher than the percentage of apoptotic cells on days 4 and 8. Apoptosis and necrosis of PMN cells at day 2 were inhibited when tubes were filled with 10% serum. Selective inhibition of apoptosis with a caspase inhibitor in vivo indicated that apoptosis and necrosis are two separate pathways leading to the death of PMN cells in the exudate. At day 2, polyurethane (PU) was associated with a lower rate of apoptosis than PVC or a random copolymer of trimethylene carbonate (TMC) and epsiloncaprolactone (ECL). Apoptosis was interpreted as an organized cell removal process that limits inflammation. Apoptosis was the natural route of PMN cell death at the early stage of inflammation.
Insights
Biomaterials induce higher rates of polymorphonuclear (PMN) cell apoptosis and necrosis in exudates compared to blood. Apoptosis is a key process for PMN cell removal and inflammation control during early inflammatory responses.
Area of Science:
- Biomaterials Science
- Immunology
- Cell Biology
Background:
- Polymorphonuclear (PMN) cells play a crucial role in the inflammatory response.
- Understanding PMN cell death pathways, apoptosis and necrosis, is vital for evaluating biomaterial interactions.
- Biomaterial-induced inflammation can lead to altered PMN cell kinetics.
Purpose of the Study:
- To quantify and compare apoptosis and necrosis of PMN cells in biomaterial-induced exudates versus peripheral blood.
- To investigate the temporal dynamics of PMN cell apoptosis and necrosis following biomaterial implantation.
- To explore the influence of different biomaterials and serum on PMN cell death.
Main Methods:
- Flow cytometry utilized for quantifying apoptotic and necrotic PMN cells.
- Hoechst 33342 and propidium iodide staining employed for identifying apoptotic and permeabilized PMN cells, respectively.
- Subcutaneous implantation of biomaterial-filled tubes in rats to generate exudates over a 7-day period.
Main Results:
- PMN cell apoptosis and necrosis were significantly higher in biomaterial exudates than in rat peripheral blood.
- Apoptosis peaked at day 2 (27% +/- 6%), while permeabilized cells increased over time, exceeding apoptotic cells by days 4 and 8.
- Serum (10%) inhibited PMN cell apoptosis and necrosis, and different biomaterials (polyurethane vs. PVC/TMC-ECL) showed varying apoptosis rates.
Conclusions:
- Apoptosis is the primary programmed cell death pathway for PMN cells in early-stage biomaterial-induced inflammation.
- Apoptosis serves as an organized mechanism for PMN cell removal, thereby limiting inflammation.
- Necrosis and apoptosis represent distinct pathways for PMN cell death in the exudate environment.