A: gel zymography (top) of representative pairs of cerebral hemispheres from wild-type (WT) mice contralateral and ipsilateral to the occlusion obtained 8 and 24 h after transient middle cerebral artery (MCA) occlusion (MCAO), showing an upregulation of pro... A: gel zymography (top) of representative pairs of cerebral hemispheres from wild-type (WT) mice contralateral and ipsilateral to the occlusion obtained 8 and 24 h after transient middle cerebral artery (MCA) occlusion (MCAO), showing an upregulation of pro-matrix metalloproteinase (MMP)-9 (105 kDa), active MMP-9 (88 and 77 kDa), and pro-MMP-2 (72 kDa). Quantification of pro- and active MMP-9 from 4 brains, normalized to the MMP-9 standard, is shown in the histogram (bottom). B: gel zymography (top) of representative pairs of the ipsilateral hemispheres of brains of chimeric mice and matched WT and MMP-9−/− mice at 24 h of reperfusion after transient MCAO. Note the expression of pro-MMP-9 and active MMP-9 in the WT→MMP-9−/− chimeras at levels similar to that seen in WT mice, only the faintest expression of pro-MMP-9 in MMP-9−/−→WT chimeras, and no pro- or active MMP-9 in MMP-9−/− mice. Expression of pro-MMP-2 was not appreciably upregulated in MMP-9−/− mice relative to WT mice, and no active MMP-2 was detected. Quantification of pro- and active MMP-9 from 4 brains is shown in the histogram (bottom), normalized to the MMP-9 standard. C: gel zymography of representative blood-derived neutrophils from the chimeric mice and matched WT and MMP-9−/− mice. Note that the expression of pro-MMP-9 (105 kDa) in neutrophils from WT→MMP-9−/− chimeras was similar to that measured in neutrophils from WT mice, whereas, conversely, expression was absent in neutrophils from MMP-9−/− mice and in neutrophils from MMP-9−/−→WT chimeras. Active MMP-9 and pro-MMP-2 are absent in neutrophils from all groups. Lane 1, human MMP standard (STND; 92 kDa). Jeffrey M. Gidday et al. Am J Physiol Heart Circ Physiol 2005;289:H558-H568 ©2005 by American Physiological Society