BIOMATERIAL-INDUCED ALTERATIONS OF HUMAN NEUTROPHILS UNDER FLUID SHEAR-STRESS - SCANNING ELECTRON-MICROSCOPIC STUDY IN-VITRO

Morphological changes of human polymorphonuclear neutrophils (PMN) adh ering to hydrophilic (glass) and hydrophobic (FEP-Teflon, polyethylene , polypropylene) surfaces were studied in a parallel-plate flow chambe r at the light and scanning electron microscopical levels. The PMN wer e exposed to a shear stress of 0.19 Pa (1.9 dynes cm(-2)) or were allo wed to adhere without the stress component (static control) during 30 min for all four biomaterials. Observation by light microscopy was per formed in situ in the flow chamber at 1, 5, 10, 15, 20, 25 and 30 min. The total number of adherent cells as a function of time and the acti vation status of the population on the basis of morphological criteria were determined. On the hydrophilic material adhesion of activated PM N was significantly higher (P < 0.05) than on the more hydrophobic sur faces. This effect was most pronounced for the adhesion of neutrophils to glass and polypropylene (PP). Polyethylene (PE) showed only minor adhesion rates. Scanning electron microscopy revealed details of cell shape changes and permitted a more precise classification of populatio ns of neutrophils based on distinctive shapes. As PMN were exposed to shear stress on glass, the majority of cells exhibited surface veils, ridges and ruffles, suggesting a high level of cell migration. In this case, on polymeric surfaces the presence of filopodial networks (FEP- Teflon) and ameoboid cell shapes (PP and PE) was noted. The results su ggest that a low shear stress, as well as various chemical and physica l properties of biomaterial surfaces, are together responsible for dif ferentiation of PMN populations on solid substrata. (C) 1996 Elsevier Science Limited