Early transient presence of implanted bone marrow stem cells reduces lesion size after cerebral ischaemia in adult rats.

AIMS: Previous studies on the therapeutic time window for intravascular administration of bone marrow stem cells (BMSCs) after stroke have shown that early intervention (from 3 h after onset) in the middle cerebral artery occlusion (MCAO) rat model is the most effective approach to reduce ischaemic lesion size. We have confirmed these observations but noticed that 2 weeks after transplantation, almost none of the grafted BMSCs could be detected in or around the lesion. The present experiments aimed to assess the fate and kinetics of intravascularly injected BMSCs shortly after administration in correlation to the development of the ischaemic lesion after MCAO. METHODS: We administered a syngeneic suspension of complete (haematopoietic and mesenchymal) BMSCs via the carotid artery to rats at 2 h after MCAO onset. We examined the distribution and tissue location of BMSCs within the first 24 h after arterial administration by perfusion-fixating rats and performing immunohistochemical analysis at different time points. RESULTS: The vast majority (>95%) of BMSCs appeared to become trapped in the spleen shortly after injection. Six hours after implantation, together with the appearance of activated microglia, the first BMSCs could be detected in and around the lesion; their number gradually increased during the first 12 h after implantation but started to decrease at 24 h. The implanted BMSCs were surrounded by activated and phagocytotic microglia. CONCLUSION: Our results show that ischaemic lesion size reduction can already be achieved by the early transient presence at the lesion site of intravascularly implanted BMSCs, possibly mediated via activated microglia.

Inhibition of CXCR3-mediated chemotaxis by the human chemokine receptor-like protein CCX-CKR.

BACKGROUND AND PURPOSE: Induction of cellular migration is the primary effect of chemokine receptor activation. However, several chemokine receptor-like proteins bind chemokines without subsequent induction of intracellular signalling and chemotaxis. It has been suggested that they act as chemokine scavengers, which may control local chemokine levels and contribute to the function of chemokines during inflammation. This has been verified for the chemokine-like receptor proteins D6 and DARC as well as CCX-CKR. Here, we provide evidence for an additional biological function of human (h)CCX-CKR. EXPERIMENTAL APPROACH: We used transfection strategies in HEK293 and human T cells. KEY RESULTS: Co-expression of hCCX-CKR completely inhibits hCXCR3-induced chemotaxis. We found that hCCX-CKR forms complexes with hCXCR3, suggesting a relationship between CCX-CKR heteromerization and inhibition of chemotaxis. Moreover, negative binding cooperativity induced by ligands both for hCXCR3 and hCCX-CKR was observed in cells expressing both receptors. This negative cooperativity may also explain the hCCX-CKR-induced inhibition of chemotaxis. CONCLUSIONS AND IMPLICATIONS: These findings suggest that hCCX-CKR prevents hCXCR3-induced chemotaxis by heteromerization thus representing a novel mechanism of regulation of immune cell migration.