gms | German Medical Science

Background: Arteriogenesis is the process by which a pre-existing arterio-arterial anastomosis develops into a functional collateral network following an arterial occlusion. We have shown that alternatively activated M2 macrophages are present in the perivascular bed of collateral vessels and our group postulated that their presence plays a pivotal role during arteriogenesis. IL10 is an anti-inflammatory cytokine that is known to polarize macrophages towards the M2 macrophage function and may thus promote collateral vessel growth.

Our study investigated the effect of IL10 on collateral vessel growth and hind limb reperfusion recovery after femoral artery ligation (FAL).

Materials and methods: FAL was performed on 21 C57/bl6 mice. NaCl, IL10, or an IL10-blocking antibody (IL10-AB) were administered by tail vein injection immediately after the operation (d0), on d3, and d7, while an additional group received IL10 (late) on d3, d7, and d14. Hind limb reperfusion was assessed repeatedly using laser-Doppler imaging on d0, d3, d7, d14, and d21. Subsequently, adductor muscle segments were harvested. An additional 31 mice were subjected to the same procedure to obtain adductor muscle segments for d3 and d7. Sections were HE-stained to determine the internal diameter and mean thickness of collateral vessel walls.

Results: IL10 treatment accelerated hind limb reperfusion after FAL vs. NaCl, whereas reperfusion was impaired during treatment with an IL10-AB \'7bd7: 62.3±16% (NaCl), 77.4±19% (IL10), 76.4±11% (IL10 late), 42.0±10% (IL10-AB, p<0.05) d14: 62.3±18% (NaCl), 83.4±15% (IL10, p<0.05), 81.5±11% (IL10 late, p<0.05), 61.2±14% (IL10-AB)\'7d. This was accompanied by increased endothelial cell proliferation (Ki67) within the collateral vessels in the IL10 treatment group on d3.

Furthermore, critical ischemic events within ligated hind limbs were observed more frequently in groups treated with an IL10-AB than in those treated with NaCl and IL10 \'7b6.3% (NaCl), 41.2% (IL10-AB), 10.0% (IL10)\'7d

Contradictory to the reperfusion recovery rates and ischemic complications, the internal diameters of collateral vessels were significantly smaller in mice treated with IL10 vs. NaCl on d21, while no significant difference was observed in mice treated with an IL10-AB \'7bd21: 64.4±36 µm (NaCl), 36.1±15 µm (IL10, p<0.05), 37.3±14 µm (IL10 late, p<0.05), 69.8±20 µm (IL10-AB)\'7d.

Conclusion: Our findings show that reperfusion recovery after FAL is accelerated with IL10 treatment and impaired by inhibition of endogenous IL10. The mismatch between reperfusion recovery rate and collateral vessel size suggests that these observations are mediated by processes other than arteriogenesis alone and need to be further investigated.