Anatomical Features and Clinical Significance of Radiculomuscular Artery Variants Involving the Suboccipital Segment of Vertebral Artery : Angiographic and Cadaver Studies.

OBJECTIVE: To discuss the significance of the radiculomuscular artery in typical variations of the distal vertebral artery (VA) from the viewpoint of microsurgical anatomy. METHODS: Some variations involving the radiculomuscular artery revealed by digital subtraction angiography (DSA) were recruited and studied together with our findings from cadaver dissections. RESULTS: A total of 29 variants were found in 26 patients, including 10 C­2 vertebral origins of the posteroinferior cerebellar artery (PICA), 13 duplicated (12 patients) and 6 aberrant V3s. An aberrant V3 was observed in our cadaver specimen. Each of these variants involved only the distal part of the lateral spinal artery (LSA) that incorporates the radiculomuscular artery and the radiculomedullary branch. Using DSA two aberrant V3s were indicated and another one was verified by anatomical study as an extradural location. CONCLUSION: The radiculomuscular artery accounts for the C­2 vertebral origin of the PICA, duplicated and aberrant V3, and extradural course of an aberrant V3 does exist. A probable extradural course of a variant between C­2 and C­1 should be kept in mind whenever each of the variations involving the radiculomuscular artery is detected by DSA or computed tomography angiography (CTA).

Secreted Protein Acidic and Rich in Cysteine Modulates Molecular Arterial Homeostasis of Human Arterial Smooth Muscle Cells In Vitro.

Secreted protein acidic and rich in cysteine (SPARC) is widely expressed in the vascular smooth muscle cells (VSMCs) of human intracranial aneurysms (IAs), but the effect and underlying mechanism of SPARC on VSMCs during the formation and progression of IAs needs to be probed. Human umbilical arterial smooth muscle cells (HUASMCs) were treated with a gradient concentrations of SPARC in vitro for different time. Cell counting kit-8 (CCK-8) assay, cell cycle, and cell apoptosis were used to investigate the effect of SPARC on HUASMCs. After exposure to 2 and 4 µg/ml SPARC, cell viability were 89.3 ± 2.00 %, and 87.57 ± 2.17 % (P < 0.05 vs. control), respectively. Induced by 2 µg/ml SPARC, the proportion of cells in G0/G1 phase was 74.77 ± 1.33 % (P < 0.05 vs. control), and the early and late apoptosis ratio were 7.38 ± 1.25 % and 4.86 ± 0.81 % (P < 0.01 vs. control), respectively. After exposure to 2 µg/ml SPARC for 2, 6, 12, 24, and 48 h, Western blot analysis showed that the protein level of p21 was upregulated significantly at 2-12 h (P < 0.05 vs. control), while the expression of p53 remained stable within 48 h. The expression of Bax protein increased markedly and peaked at 24 (P < 0.01 vs. control), while Bcl2 protein decreased significantly at 48 h (P < 0.01 vs. control). Cleaved caspase3 was also upregulated dramatically and peaked at 24 h (P < 0.05 vs. control). The protein level of MMP2 increased significantly and peaked at 24 h (P < 0.01 vs. control), while TIMP2 remained stable and even reduced at 48 h (P < 0.05 vs. control). Taken together, SPARC could arrest HUASMCs in G0/G1 phase by overexpression of p21 and induce mitochondria-mediated apoptosis in vitro, which could result in the decreased cell viability. Besides, SPARC might also lead to the activation of MMP2 instead of MMP9. These results indicated SPARC could reduce the self-repair capability and increase injury of media layer and internal elastic lamina of intracranial artery, which would disrupt the normal homeostatic mechanism controlling vascular repair, thus promoting the formation and progression of IAs.