COMPARISON OF GROWTH-RATES OF BOVINE RETINAL AND BRAIN MICROVASCULAR PERICYTES IN DIFFERENT OXYGEN CONCENTRATIONS IN-VITRO

Background: The hyperoxic injury of the microcirculation in the centra l nervous system appears to be specific to the retina in premature mam mals. Oxygen tensions in normal adult mammalian retina and brain vary between nearly 0 and 90 mmHg. This study sought to compare the in vitr o replication of retinal and brain microvascular pericytes in normal g lucose medium and in 1%, 5% and 20% oxygen (equivalent to 15 mmHg, 35 mmHg and 150 mmHg, respectively). Methods: A preliminary study, using oxygen microelectrodes, confirmed that the pericellular oxygen tension of pericytes, cultured in medium under air, was within 13 mmHg of the tension of the gas phase above the media. Pericytes were highly enric hed by magnetic antibody cell sorting with the anti-pericyte monoclona l antibody (3G5) to 95% to 99% purity, to remove cell contaminants whi ch may have invalidated the mitogenic assay. Results: Mitogenic assays showed that brain pericytes replicated faster than their counterparts from retina (P<0.0001, averaged for data from all culture conditions using three-way ANOVA). Reduction of oxygen tension from 150 to 15 mmH g led to significantly increased replication of retinal pericytes (P=0 .01), but an insignificant increase for brain pericytes. Conclusions: We have found that pericytes from the brain and retina cultured conven tionally in fetal calf serum consume a relatively low amount of oxygen . Decreasing the oxygen tension to 1% (15 to 20 mmHg) increased the re plication of retinal pericytes but not brain pericytes in normal gluco se concentrations and in fetal calf serum. That retinal pericyte repli cation is sensitive to variation in oxygen tensions, indicates that th e retinal microvascular cells have a unique biological response. This growth sensitivity to oxygen may be important in the pathogenesis of r etinopathy of prematurity.