Depletion of circulating PMNs decreases the expansion of pericyte gaps and collagen IV LERs during inflammation.

<p>(<b>A</b>) 3D images showing the association of pericyte gaps and PMNs in mouse cremaster muscles that were untreated (left) or treated with IL-1β (middle and right). Arrows indicated pericyte gaps and a circle showed PMNs migrating through pericyte gaps. In IL-1β-stimulated tissues, two types of venular segments were noted. In some vessel segments (middle), both transmigrating and extravasated PMNs were seen. In others, no PMNs were found in the vessel walls or within 100 µm of the perivascular tissues (right). In the first situation (middle), pericyte gaps being used by transmigrating PMNs (circled area) are referred to as “leukocyte-associated pericyte gaps”. In the second situation (right, boxed area), pericyte gaps are referred to as “non-leukocyte-associated pericyte gaps”. Note: we did not classify the pericyte gaps not circled in the middle panel since we were not sure whether these gaps were used by leukocytes or not. However, these were included in the measurements when analyzing the total pericyte gaps. Similarly, collagen IV LERs were described as “leukocyte-associated LERs” or “non-leukocyte-associated LERs”. (<b>B</b>) Average area of pericyte gaps in untreated or IL-1β-stimulated mouse cremaster muscle venules. (<b>C</b>) 2D images along the longitudinal axis of venules treated with IL-1β together with control or anti-Gr-1 antibodies. Transmigrating PMNs are circled. (<b>D</b>) Number of transmigrating PMNs within venular walls treated with saline or IL-1β together with control or anti-Gr-1 antibodies. (<b>E</b>) Number of extravasated PMNs within mouse cremaster muscles treated with saline or IL-1β together with control or anti-Gr-1 antibodies. (<b>F</b>) Average area of pericyte gaps in untreated venules or vessels treated with IL-1β together with control or anti-Gr-1 antibodies. (<b>G</b>) The total area of leukocyte-associated pericyte gaps was normalized relative to a 200 µm length of vessel. (<b>H</b>) The total area of leukocyte-associated collagen IV LERs was normalized relative to a 200 µm length of vessel. Bar = 10 µm. 5–6 mice were used in each treatment. In (<b>B</b>) and (<b>F</b>), ANOVA plus Neuman-Keuls multiple comparisons were performed and in others, t tests were applied. *P<0.05, **P<0.01, and ***P<0.001, compared to untreated groups. ^###P<0.001, compared between gaps as indicated.