Basic Studies On The Effect Of Noninvasive Treatments On Degenerative Changes Of Aneurysmal Wall

Backgrounds: Cerebral aneurysms(CAs) rupture is a major cause of subarachnoid hemorrhage(SAH) with high morbidity and mortality. Current management of unruptured CAs is microsurgical clipping and/or endovascular coiling. No safe and effective noninvasive therapies have been identified in clinical praciece. Recent studies suggest the endothelial dysfunction or impairment and macrophage-mediated chronic inflammatory response are responsible for aneurysm formation and progression to rupture. Our previous studies reported that decreased level and impaired function of endothelial progenitor cells(EPCs) in CAs patients was correlated with CAs formation. Modulating the inflammatory process and the impaired circulating EPCs may prove to be clinically significant.Objective:(1) To investigate the role of aspirin administration in vascular degeneration after CAs induction and clarifies the possible underlying mechanisms.(2) To investigate the effect of intravenous transfusion of cord blood-derived endothelial colony-forming cells(ECFCs) on vascular degeneration after CAs induction and clarify the possible underlying mechanisms.Methods:(1) 7-week old male Sprague–Dawley(SD) rats(20/group) were randomly divided into normal group, CA group and CA+aspirin group. The blood pressure of unanesthetized rats was measured using a noninvasive tail cuff method. After deep anesthesia, blood sample was obtained to examine circulating CD34+CD133+ EPCs, platelet aggregation and platelet counts. The right anterior cerebral artery/olfactory artery(ACA/OA) bifurcations were stripped and assessed morphologically after Verhoeff’s Van Gieson staining. Macrophages(CD68+) infiltration in aneurysmalwall was evaluated by immunohistochemistry. The m RNAs expression of MMP-2, MMP-9, TIMP-1, NF-κB, MCP-1 and VCAM-1 was examined by RT-PCR.(2) 7-week old male SD rats(30/group) were randomly divided into normal group, CA+saline group and CA+ECFCs transfusion group. The blood pressure and morphological features of right ACA/OA bifurcations was measured as Methods(1). Macrophages(CD68+) infiltration and apoptosis of smooth muscle cells(SMCs) in aneurysmal wall was evaluated by immunohistochemistry. The m RNAs expression of MMP-2, MMP-9, TIMP-1, NF-κB, MCP-1, VCAM-1, e NOS, Bcl-2 and i NOS was examined by RT-PCR.Results:(1) 2 months after CA induction, rats in the CA+aspirin group exhibited a significant decrease in degeneration of internal elastic lamina(IEL), medial layer thinning and CA size in ACA/OA bifurcations without alteration in blood pressure compared with rats in the CA group. Aspirin following CA induction increased circulating EPCs to near control levels, inhibited platelet aggregation and caused no change in platelet counts. Aspirin reversed the upregulation of NF-κB, MCP-1 and VCAM-1 expression after CA induction. Aspirin reduced macrophages infiltration into the aneurysmal wall, which was accompanied by downregulation of MMP-2 and MMP-9 expression and upregulation of TIMP expression.(2) Rats in CA+ECFCs group showed a notable reduction in IEL degeneration, media layer thinning and CA size without alteration in blood pressure compared with those in CA+saline group. ECFCs transfusion dramatically decreased VCAM-1 and NF-κB expression, increased e NOS expression but caused no change in MCP-1 expression, which was accompanied by reduced macrophages infiltration. ECFCs transfusion inhibited the MMPs-driven wall destruction by downregulating MMP-2, MMP-9 expression and upregulating TIMP-1 expression. Moreover, ECFCstransfusion reversed downregulation of Bcl-2 expression and upregulation of i NOS expression, and decreased SMCs apoptosis.Conclusion:(1) These findings suggest that aspirin have a beneficial effect in preventing vascular degeneration by mobilizing EPCs, reducing macrophages-mediated chronic inflammation and arterial remodeling.(2) These findings suggest that ECFCs transfusion confers protection against degeneration of aneurysmal wall by inhibiting endothelial dysfunction, macrophages-mediated chronic inflammation and excessive SMCs apoptosis.(3) Collectively, our data indicate that aspirin administration or ECFCs transfusion, as noninvasive treatments, may work as reliable supplement to surgical treatment of unruptured CAs.