Differential Vulnerability and Response to Injury among Brain Cell Types Comprising the Neurovascular Unit.

The neurovascular unit (NVU) includes multiple different cell types, including neurons, astrocytes, endothelial cells, and pericytes, which respond to insults on very different time or dose scales. We defined differential vulnerability among these cell types, using response to two different insults: oxygen-glucose deprivation (OGD) and thrombin-mediated cytotoxicity. We found that neurons are most vulnerable, followed by endothelial cells and astrocytes. After temporary focal cerebral ischemia in male rats, we found significantly more injured neurons, compared with astrocytes in the ischemic area, consistent with differential vulnerability in vivo. We sought to illustrate different and shared mechanisms across all cell types during response to insult. We found that gene expression profiles in response to OGD differed among the cell types, with a paucity of gene responses shared by all types. All cell types activated genes relating to autophagy, apoptosis, and necroptosis, but the specific genes differed. Astrocytes and endothelial cells also activated pathways connected to DNA repair and antiapoptosis. Taken together, the data support the concept of differential vulnerability in the NVU and suggest that different elements of the unit will evolve from salvageable to irretrievable on different time scales while residing in the same brain region and receiving the same (ischemic) blood flow. Future work will focus on the mechanisms of these differences. These data suggest future stroke therapy development should target different elements of the NVU differently.

"En-glove" lysis of lower eyelid retractors with AlloDerm and dermis-fat grafts in lower eyelid retraction surgery.

PURPOSE: To describe a minimally invasive surgical technique using AlloDerm or dermis-fat grafts for lower eyelid retraction. METHODS: A retrospective review of all patients undergoing lower eyelid retraction surgery via a minimal invasive, "en-glove" technique from 2005 through 2009. Charts were reviewed for the type of graft (AlloDerm or dermis-fat) used, the etiology of lower eyelid retraction, and the follow-up time. Outcome measures included lower eyelid height (measured from the corneal light reflex to the lower eyelid margin, or MRD2), reduction of lagophthalmos, cosmetic appearance, complications, and need for further surgery. Presurgery and postreconstruction photographs were reviewed and graded for functional and cosmetic outcome. RESULTS: A total of 8 patients underwent successful lower eyelid retraction surgery using this minimally invasive technique. Etiologies included thyroid eye disease and cicatricial paralytic lower eyelid retraction. Mean improvement in MRD2 was 1.5 mm for the AlloDerm group (4 patients, 7 eyelids) and 1.0 mm for the dermis-fat group (4 patients, 4 eyelids) after a minimum of 3 months' follow-up. The cosmetic result was satisfactory in all cases. CONCLUSIONS: "En-glove" lower eyelid retraction surgical technique offers a minimally invasive approach for the release of the lower eyelid retractors and allows for volume augmentation using either AlloDerm or dermis-fat spacer graft.