Sequential Contribution of Parenchymal and Neural Stem Cell-Derived Oligodendrocyte Precursor Cells toward Remyelination.

In the adult mammalian forebrain, oligodendrocyte precursor cells (OPCs), also known as NG2 glia are distributed ubiquitously throughout the gray and white matter. They remain proliferative and continuously generate myelinating oligodendrocytes throughout life. In response to a demyelinating insult, OPCs proliferate rapidly and differentiate into oligodendrocytes which contribute to myelin repair. In addition to OPCs, neural stem cells (NSCs) in the subventricular zone (SVZ) also contribute to remyelinating oligodendrocytes, particularly in demyelinated lesions in the vicinity of the SVZ, such as the corpus callosum. To determine the relative contribution of local OPCs and NSC-derived cells toward myelin repair, we performed genetic fate mapping of OPCs and NSCs and compared their ability to generate oligodendrocytes after acute demyelination in the corpus callosum created by local injection of α-lysophosphatidylcholine (LPC). We have found that local OPCs responded rapidly to acute demyelination, expanded in the lesion within seven days, and produced oligodendrocytes by two weeks after lesioning. By contrast, NSC-derived NG2 cells did not significantly increase in the lesion until four weeks after demyelination and generated fewer oligodendrocytes than parenchymal OPCs. These observations suggest that local OPCs could function as the primary responders to repair acutely demyelinated lesion, and that NSCs in the SVZ contribute to repopulating OPCs following their depletion due to oligodendrocyte differentiation.

Creation of an Extraluminal Arterial Bypass Graft Using a Commercially Available Self-Expanding Stent Graft: Feasibility Study in a Porcine Model.

PURPOSE: The purpose of this study was to assess the technical feasibility of ultrasound-guided endovascular creation of a percutaneous extraluminal arterial bypass graft without a surgically created arterial anastomosis. MATERIALS AND METHODS: Nine swine were utilized for this IACUC-approved study using a carotid bypass model in swine. Using sonographic guidance, percutaneous access was obtained to the proximal and distal common carotid artery. A self-expanding stent graft was advanced through the proximal carotid access site, tunneled subcutaneously, then advanced through the distal carotid access site, and deployed. The stent grafts were monitored weekly for patency using ultrasound. Angiography was performed at 4 weeks to evaluate for graft patency. Gross pathologic analysis was performed on the explanted stent grafts. RESULTS: In eight out of the nine swine (89%), percutaneous extraluminal bypass graft creation was technically successful, with brisk flow through the stent graft to the distal circulation, complete exclusion of the bypassed segment of carotid artery, and no extravasation. The technical failure was due to stent graft maldeployment. Of the six swine evaluated for patency, four grafts were patent at the 4-week end point. Both occluded stent grafts were due to extraluminal extrusion of one end, likely related to neck movement and growth in neck length. CONCLUSION: The percutaneous arterial bypass technique had a high technical success rate and a graft patency rate of 67% at 4 weeks, with early occlusions possibly related to limitations of the animal model.

Internally Randomized Control Trial of Radiation Exposure Using Ultra-low Radiation Imaging Versus Traditional C-arm Fluoroscopy for Patients Undergoing Single-level Minimally Invasive Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: Randomized controlled trial. OBJECTIVE: To compare radiation exposure between ultra-low radiation imaging (ULRI) with image enhancement and standard-dose fluoroscopy for patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF). SUMMARY OF BACKGROUND DATA: Although the benefits of MIS are lauded by many, there is a significant amount of radiation exposure to surgeon and operating room personnel. Our goal with this work was to see if by using ultra-low dose radiation settings coupled with image enhancement, this exposure could be minimized. METHODS: An institutional review board approved, prospective, internally randomized controlled trial was performed comparing ultra-low dose settings coupled with image enhancement software to conventional fluoroscopic imaging. In this study, each patient served as their own control, randomly assigning one side of MIS-TLIF for cannulation and K-wire placement using each imaging modality. Further, the case was also randomly divided into screw placement and cage placement/final images to allow further comparisons amongst patients. Radiation production from the C-arm fluoroscope and radiation exposure to all operating room personnel were recorded. RESULTS: Twenty-four patients were randomly assigned to undergo a single level MIS-TLIF. In no case was low radiation imaging abandoned, and no patient had a neurologic decline or required hardware repositioning. Everyone in the operating room-the physician, scrub nurse, circulator, and anesthesiologist-all benefited with 61.6% to 83.5% reduction in radiation exposure during cannulation and K-wire placement to screw insertion aided by ULRI. In every case but the anesthesiologist dose, this was statistically significant (P < 0.05). This benefit required no additional time (P = 0.78 for K-wire placement). CONCLUSION: ULRI, when aided by image enhancement software, affords the ability for all parties in the operating room to substantially decrease their radiation exposure compared with standard-dose C-arm fluoroscopy without adding additional time or an increased complication rate. LEVEL OF EVIDENCE: 2.