Autogenous vascular replacements induced by a subcutaneous pulsatile system

Combination of inductive effect of lipopolysaccharide and in situ mechanical conditioning for forming an autologous vascular graft in vivo

Autologous vascular grafts have the advantages of better biocompatibility and prognosis. However, previous studies that implanted bare polymer tubes in animals to grow autologous tubular tissues were limited by their poor yield rates and stability. To enhance the yield rate of the tubular tissue, we employed a design with the addition of overlaid autologous whole blood scaffold containing lipopolysaccharides (LPS). Furthermore, we applied in vivo dynamic mechanical stimuli through cyclically inflatable silicone tube to improve the mechanical properties of the harvested tissues. The effectiveness of the modification was examined by implanting the tubes in the peritoneal cavity of rats. A group without mechanical stimuli served as the controls. After 24 days of culture including 16 days of cyclic mechanical stimuli, we harvested the tubular tissue forming on the silicone tube for analysis or further autologous interposition vascular grafting. In comparison with those without cyclic dynamic stimuli, tubular tissues with this treatment during in vivo culture had stronger mechanical properties, better smooth muscle differentiation, and more collagen and elastin expression by the end of incubation period in the peritoneal cavity. The grafts remained patent after 4 months of implantation and showed the presence of endothelial and smooth muscle cells. This model shows a new prospect for vascular tissue engineering.

Conductance to outflow of CSF in normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) is defined as a combination of dementia, gait disturbances and/or urinary incontinence, hydrocephalus, and a normal intracranial mean pressure. The clinical effect of CSF shunting in patients with this syndrome is sometimes striking, but generally only 50-60% of the shunted patients benefit from the treatment. It is assumed that the condition is caused by reduced conductance to outflow of CSF ( Cout ). A clinically usable method for the measurement of Cout has been developed. Cout has been measured in 80 patients with NPH. The results of clinical examination, computed tomography (CT), long-term intracranial pressure recording, isotope cisternography (ICG), and Cout have been compared to the clinical results of shunting 3 and 12 months after operation. Among the preoperative investigations Cout proved to have the best diagnostic specificity and sensitivity. Thus, selection of patients for shunting on the basis of Cout should lead to a satisfyingly high success rate. The different methods for measurement of Cout are discussed, and a theory on the pathophysiology of NPH is proposed. A clinical investigational programme, based on the results from clinical examination, CT, pressure recording, and measurements of Cout is suggested.

Why does hydrocephalus progress?

Experimental results in rabbits support the hypothesis that occlusion of the cerebral subarachnoid space, resulting in an increased strain-stress ratio in the ventricular wall, is the mechanical basis of chronic progressive hydrocephalus within a rigid skull. When the cerebral subarachnoid space was drained through an artificial low-resistance fluid pathway, the wall of the olfactory ventricle showed edema that was indistinguishable from the edema of kaolin hydrocephalus. Increased CSF pressure did not produce edema of this grade when the cerebral subarachnoid space was patent. When the subarachnoid space surrounding the right olfactory bulb was occluded with silicone rubber, the right but not the left olfactory ventricle enlarged; resistance to cerebrospinal fluid absorption remained normal.