Search

While the peripheral nervous system has regenerative ability, restoration of sufficient function remains a challenge. Vimentin has been shown to be localized in axonal growth fronts and associated with nerve regeneration, including myelination, neuroplasticity, kinase signaling in nerve axoplasm, and cell migration; however, the mechanisms regulating its expression within Schwann cell (SC) remain unexplored. The aim of this study was to profile the spatial and temporal expression profile of microRNA (miRNA) in a regenerating rat sciatic nerve after transection, and explore the potential role of miR-138-5p targeting vimentin in SC proliferation and migration. A rat sciatic nerve transection model, utilizing a polyethylene nerve guide, was used to investigate miRNA expression at 7, 14, 30, 60, and 90 days during nerve regeneration. Relative levels of miRNA expression were determined using microarray analysis and subsequently validated with quantitative real-time polymerase chain reaction. In vitro assays were conducted with cultured Schwann cells transfected with miRNA mimics and assessed for migratory and proliferative potential. The top seven dysregulated miRNAs reported in this study have been implicated in cell migration elsewhere, and GO and KEGG analyses predicted activities essential to wound healing. Transfection of one of these, miRNA-138-5p, into SCs reduced cell migration and proliferation. miR-138-5p has been shown to directly target vimentin in cancer cells, and the luciferase assay performed here in rat Schwann cells confirmed it. These results detail a role of miR-138-5p in rat peripheral nerve regeneration and expand on reports of it as an important regulator in the peripheral nervous system., Competing Interests: The authors declare no conflicts of interest

The subcutaneous route offers myriad benefits for the administration of biotherapeutics in both acute and chronic diseases, including convenience, cost effectiveness and the potential for automation through closed-loop systems. Recent advances in parenteral administration devices and the use of additives which enhance drug dispersion have generated substantial additional interest in IV to SQ switching studies. Designing pre-clinical and clinical studies using SQ mediated delivery however requires deep understanding of complex inter-related physiologies and transport pathways governing the interstitial matrix, vascular system and lymphatic channels. This expert review will highlight key structural features which contribute to transport and biodistribution in the subcutaneous space and also assess the impact of drug formulations. Based on the rapidly growing interest in the SQ delivery route, a number of potential areas for future development are highlighted, which are likely to allow continued evolution and innovation in this important area.

Background: Protein expression profiles throughout 28 days of peripheral nerve regeneration were characterized using an established rat sciatic nerve transection injury model. Reverse phase protein microarrays were used to identify the spatial and temporal expression profile of multiple proteins implicated in peripheral nerve regeneration including growth factors, extracellular matrix proteins, and proteins involved in adhesion and migration. This high-throughput approach enabled the simultaneous analysis of 3,360 samples on a nitrocellulose-coated slide., Results: The extracellular matrix proteins collagen I and III, laminin gamma-1, fibronectin, nidogen and versican displayed an early increase in protein levels in the guide and proximal sections of the regenerating nerve with levels at or above the baseline expression of intact nerve by the end of the 28 day experimental course. The 28 day protein levels were also at or above baseline in the distal segment however an early increase was only noted for laminin, nidogen, and fibronectin. While the level of epidermal growth factor, ciliary neurotrophic factor and fibroblast growth factor-1 and -2 increased throughout the experimental course in the proximal and distal segments, nerve growth factor only increased in the distal segment and fibroblast growth factor-1 and -2 and nerve growth factor were the only proteins in that group to show an early increase in the guide contents. As expected, several proteins involved in cell adhesion and motility; namely focal adhesion kinase, N-cadherin and β-catenin increased earlier in the proximal and distal segments than in the guide contents reflecting the relatively acellular matrix of the early regenerate., Conclusions: In this study we identified changes in expression of multiple proteins over time linked to regeneration of the rat sciatic nerve both demonstrating the utility of reverse phase protein arrays in nerve regeneration research and revealing a detailed, composite spatiotemporal expression profile of peripheral nerve regeneration.

HealthPartners Institute for Medical Education has developed an innovative continuing medical education model that uses elements of theater to explore complex issues in health care and increase participant engagement. The model was recently used during a hospital medicine retreat. The learning event included a four-part monologue in which an actor portrayed a patient, interactive didactic sessions, a game show titled "Who Wants to be Hospitalized a MillionTimes," computerized simulations, and a call for clinicians to help patients adopt healthier behaviors. Post-event evaluations demonstrated that participants gained valuable clinical knowledge and appreciated the combination of active learning and theater.

Background: The sagittal plane computed tomographic (CT) scan has been proposed as the most important radiologic view in the diagnosis of orbital floor fractures. Before the advent of high-resolution CT, several articles were published in the radiology literature debating the need for direct sagittal views, which required cumbersome patient positioning. Today, the ability to easily create high-quality sagittal reformations requires reassessment of the importance of this view in the evaluation of orbital floor fractures., Materials and Methods: Computed tomographic studies of 24 orbital floor fractures for which coronal and sagittal images were available were included. Five independent reviewers evaluated all image sets and recorded maximum fracture width, depth, posterior shelf length (PSL), and presence of medial wall fracture and of trap door deformity. Direct fracture width measurements were obtained via coronal images, whereas depth and PSL were measured directly in the sagittal plane. Indirect measurements in a given plane were obtained by counting the number of slices in which the fracture was present and multiplying by the slice thickness. Cronbach alpha analysis was used to provide an intraclass correlation coefficient, where greater values signify less interreviewer variability., Results: The Cronbach alpha values for width, depth, and PSL were 64%, 59%, and 85% in the coronal view and 76%, 55%, and 51% in the sagittal view, respectively. The alpha values for presence/absence of medial wall fracture and trap door deformity were greater in the coronal view at 73% and 55%, respectively. The intrareviewer variability was not significantly correlated with the degree of patient rotation or CT scan slice thickness. The interreviewer variability was significantly less among attending reviewer then resident reviewers., Conclusions: There was less interreviewer variability when the measured variables were assessed indirectly (width was best assessed in the sagittal plane, and depth and PSL were best assessed in the coronal view). These findings support the idea that additional views aid the surgeon's ability to further define fracture anatomy than might be possible with any single view, thereby improving preoperative planning and reconstructive strategies.

Background: Empirical and experimental evidence abounds as to the negative effects of smoking on skin flaps. The ideal duration of preoperative smoking cessation is unclear. The present study evaluates the effect of various durations of smoking cessation on skin flap survival in a rat model., Methods: Forty smoke-exposed and 10 non-smoke-exposed Sprague-Dawley rats were divided into five groups: controls and 0 days, 2 weeks, 4 weeks, and 8 weeks of smoking cessation. All animals had a dorsally based random pattern flap created and either bilateral pure axial superficial inferior epigastric (superficial inferior epigastric) flaps or a unilaterally superficial inferior epigastric axial with random component flap. The percentage of flap necrosis was assessed 2 weeks postoperatively., Results: The mean amount of random skin flap necrosis was 16.6 +/- 13.0 percent, 30.3 +/- 8.4 percent, 27.6 +/- 7.9 percent, 27.1 +/- 6.1 percent, and 29.7 +/- 10.3 percent, respectively. There was significantly less flap necrosis in the controls than in all other groups (p < 0.03). There was no necrosis of any of the pure axial superficial inferior epigastric flaps. The mean amount of superficial inferior epigastric axial with random component skin flap necrosis was 11.1 +/- 6.2 percent, 31.1 +/- 6.0 percent, 36.0 +/- 8.4 percent, 21.7 +/- 4.0 percent, and 19.1 +/- 6.3 percent, respectively. All smoke-exposed groups had significantly greater flap necrosis than controls, with the exception of the 8-week group (p < 0.02)., Conclusions: Smoking irreversibly increases the risk of flap necrosis in a random pattern flap out to 2 months of preoperative cessation. Preoperative smoking does not result in any necrosis of pure axial flaps. In axial with random component flaps, significant decreases in skin flap necrosis are not seen until 4 weeks of preoperative cessation.

Microvascular clamps have several potential shortcomings, including the risk of vessel injury. LeGoo, a novel reverse thermosensitive polymer (Pluromed Inc., Woburn, MA), is investigated as a substitute to vascular clamping in a microsurgical model and the technical details are described. Femoral vessels of Sprague Dawley rats were used to evaluate the usefulness of this polymer for performing end-to-end arterioarterial (AA), venovenous (VV), and end-to-side arteriovenous (AV) microvascular anastomoses. The ability to obtain and maintain hemostasis was assessed. Secondary endpoints, including polymer volume, concentration, temperature, infusion technique, ability to reinfuse, blood vessel stenting effect, polymer dissolution characteristics, and reestablishment of flow, were also noted. Initial hemostasis occurred in every case. Mean duration of efficacy (hemostasis) after initial injection was 17.8 minutes (4 minutes to 44.5 minutes) for AA anastomoses and 31.8 minutes (13 minutes to 46 minutes) for VV anastomoses. Mean volume of polymer initially injected was 0.11 mL (0.01 mL to 0.20 mL) and 0.07 mL (0.06 mL to 0.10 mL) for AA and AV arteries, respectively, and 0.14 mL (0.10 mL to 0.20 mL) and 0.20 mL (0.15 mL to 0.27 mL) for VV and AV veins. Use of LeGoo in veins was clearly superior to arterial use with regard to the technical aspects of injecting LeGoo and reestablishing hemostasis, as well as greater vessel stenting effect and less vessel retraction. This novel polymer showed promise for its ability to allow for hemostasis while performing microvascular anastomoses. Improvements were made with regard to injection techniques, appropriate volumes, ability to reliably determine gel plug dissolution, and final vessel patency. Preliminary results demonstrate that this polymer may be a viable substitute for microvascular clamps.

In this study we investigated the effects of materials prepared with electrical poling on neurite outgrowth in vitro and nerve regeneration in vivo. Neuro-2a cells were seeded on poled and unpoled poly(lactic-co-glycolic) (PLGA) films and observed at time periods 24, 48 and 72 h post-seeding. The percentage of cells with neurites and the neurites per cell were quantified using light microscopy. At 48 and 72 h post-seeding, both the number of cells with neurites and the neurites per cell were significantly increased on the poled films compared to those on unpoled films. An established rat sciatic nerve model was used for in vivo studies to assess the effects of PLGA guides, poled for two different periods, on peripheral nerve regeneration. Guides were inserted in rats to bridge a 1.0 cm gap created in the right sciatic nerve. After four weeks, nerves regenerated through poled guides displayed a significant increase in conduction velocity and significantly increased numbers of axons across the guides, as compared to nerves regenerating through an unpoled guidance channel. Electrical poling was shown to promote neurite growth, axon regeneration and the conduction rate of the repaired nerve. We concluded that guides prepared with electrical poling enhance peripheral nerve regeneration.

Using an established rat peripheral-nerve regeneration model, the authors have demonstrated enhancement of regeneration following subcutaneous priming of bioresorbable poly(lactic-co-glycolic)acid (PLGA) guides in vivo. Four weeks after nerve reconstruction, regeneration of the peripheral nerve through the cell-infiltrated guides displayed a significant increase in the total axon number and myelination status recorded in primed over unprimed guides, demonstrating the importance of cell-mediated events in the regeneration process. To define the different components enhancing nerve regeneration in this model, they have focused on identifying factors capable of eliciting Schwann-cell migration, since this has been identified as an early and necessary event in nerve regeneration. Using an in vitro migration assay, screening of a limited number of cellular and extracellular factors has demonstrated differential promotion of Schwann-cell migration. Of interest, combining fibronectin and bFGF resulted in a two-fold enhancement in Schwann-cell migration over that recorded with either alone. These results describe a rapid screening process for identifying various molecules and combinations thereof, with potential involvement in Schwann-cell migration. Coupling these findings to the use of the PLGA guide as an in vivo delivery system provides a rationale for the selection of exogenous factors to test for the enhancement of peripheral-nerve regeneration.

Using an established rat peripheral nerve regeneration model, we investigated the role of glial growth factor (GGF) in nerve regeneration in combination with a novel bioresorbable poly(lactic-co-glycolic) acid (PLGA) guide in vivo. Schwann cells, established from a 1-cm segment of excised rat sciatic nerve, were isolated and seeded onto nerve guides with or without GGF (n = 24/group). Living nerve guides were re-established in these animals, and nerve regeneration was assessed over a period of 12 weeks. Histological studies revealed a reduction in the total axon count and the number of myelinated axons in the presence of exogenously added Schwann cells compared to saline controls. In contrast, the addition of GGF alone enhanced the total number of axons and significantly increased the number of blood vessels. Although combining GGF with Schwann cells negated the enhanced numbers of axons and blood vessels seen with GGF alone, this combination resulted in the highest myelination index and the fastest conduction velocities recorded. The PLGA guide material did not trigger any histologically detectable host response and was permissive for nerve regeneration in this animal model. The results from this study demonstrate the potential utility of this guide in vivo and establish a promotional role for GGF in nerve regeneration.

Schwann cells play a central role in peripheral-nerve regeneration, in which it has been shown that the addition of exogenous Schwann cells enhances the temporal and spatial sequence of events observed in regeneration. In this study, the authors investigated the fate of exogenous cells in this process by using fluorescently tagged autogenous Schwann cells in an established rat model of peripheral-nerve regeneration. Tracking labeled cells over a 4-week period revealed early migration of Schwann cells into the proximal nerve segment, followed by a concentration of migrating Schwann cells, leading the proximal growth cone throughout the regenerative process. The early proximal distribution of labeled cells suggests active migration in response to nerve damage, with spatial localization at the center of the proximal nerve segment and not the epineural surface. These observations demonstrate an interaction of exogenous Schwann cells with intact nerve tissue in vivo and affirm their role in the directional growth of regenerating axons.

Hyaluronic acid has been shown to enhance peripheral nerve regeneration in vitro. It has been proposed that, during the fibrin matrix phase of regeneration, hyaluronic acid organizes the extracellular matrix into a hydrated open lattice, thereby facilitating migration of the regenerating axons. Hyaluronic acid solutions and saline control solutions were injected into a nerve guide spanning a transected gap in the sciatic nerve of Sprague-Dawley rats (five in each group). Nerve conduction velocities were measured at 4 weeks by electromyography (EMG) before sacrifice of the animals. These studies demonstrated increased conduction velocities in the hyaluronic acid group compared with control animals (P = 0.006). After the animals were sacrificed, regenerated axon cables were quantified histologically, and axon branching was delineated by retrograde tracer analysis. In addition, the hyaluronic acid group showed an increase in myelinated axon counts at 4 weeks (P= 0.03). An increase in retrograde flow was demonstrated in the hyaluronic acid groups compared with animals receiving saline solution.

Schwann cells appear to stimulate the early phases of axon regeneration. The reported study investigated whether nerve guides with Schwann-cell monolayers can help regenerating nerves span gaps larger than 1 cm. Schwann-cell cultures were established by resecting 1-cm segments of sciatic nerves of adult female Sprague-Dawley rats, establishing cell monolayers in 24-mm nerve guides, and then reinserting these "living guides" into 20-mm nerve gaps of the rats from which they were developed. Control groups had plain guides (no Schwann cells) inserted between the same 20-mm gaps. In the experimental group, resected nerves regrew progressively. At 8 weeks, regrowth had spanned the entire gap in 60 percent of the animals. Axon counts increased at each successive time point. Regeneration did begin to occur in the control group but by 8 weeks, those cables had atrophied. The experimental groups displayed more central connections and higher nerve conduction velocity. Explant organ cultures of rat sciatic nerve can be used to develop nonneural conduits with Schwann-cell monolayers. These living artificial nerve guides permit the spanning of gaps of at least 20 mm.

Hereditary hemorrhagic telangiectasia is a systemic disorder of blood vessels. It often leads to severe epistaxis that is refractory to conventional therapy. Three patients with severe epistaxis caused by hereditary hemorrhagic telangiectasia unresponsive to laser coagulation and to septal dermoplasty and requiring multiple transfusions underwent extirpation of nasal mucosa through a rhinotomy approach, with a median forehead flap and split-thickness skin graft coverage of the mucosal defects over the floor and lateral walls of the nose. All patients had reduced frequency and severity of bleeding without any need for transfusions during follow-up periods of 6 months, 3 years, and 5 years, respectively. Forehead flaps resulted in minimal morbidity. Partial nasal obstruction and a forehead scar were the main complaints. Surgical technique, complications, and alternative therapy are discussed.

The use of non-neural conduits to span gaps in regenerating peripheral nerves has been noted in the literature for many years. An intriguing addition to this so-called entubulation repair method is the continuous instillation of neuronotrophic or growth factors into the lumen of the guide to bathe the regenerating nerve. A model is presented which uses an osmotic pump that supplies a constant, reproducible amount of solution into the lumen of a nerve guide without disrupting the regeneration process.

The inside-out vein graft is a vein conduit pulled through itself to invert the normal orientation and place the adventitial layer within the lumen of the conduit. Our study compares regeneration of peripheral nerves in the rat through two conduits: inside-out graft of the jugular vein and autogenous nerve graft. In 10 rats, the right jugular vein was harvested, turned inside out, and used to bridge a 10 mm defect created in the right sciatic nerve. The 10 mm nerve segment from the right was then used as a standard nerve graft to bridge a 10 mm gap created in the left sciatic nerve. Rats were sacrificed at 8 and 12 weeks. Regeneration on the inside-out vein graft side showed superior functional results (faster conduction velocities) and improved histological results (greater axon counts) compared with the nerve grafted side. We feel the adventitial surface of the wall of the vein promotes nerve regeneration by providing an environment rich with collagen, laminin, and Schwann cells and promotes increased vascularization of the new nerve.

The influence on nerve regeneration of the extracellular matrix glycoprotein laminin was studied after sciatic nerve transection in 90 outbred Sprague-Dawley rats. Nerve regeneration through basal lamina grafts was comparable with regeneration through traditional nerve grafts across gaps up to 2.0 cm in length. True axonal regeneration rather than axonal branching was demonstrated by retrograde horseradish peroxidase labeling of nerve cables. Pretreatment of basal lamina grafts with antilaminin antibodies reduced the total number of regenerated axons by 90 percent with a significant decrease of nerve conduction velocity and a significant impairment of walking track patterns. The basement membrane glycoprotein laminin serves a critical role in the regeneration of peripheral nerves through basal lamina grafts.

Vein grafts have been used both experimentally and clinically to bridge gaps in peripheral nerves. This study describes a modification of the vein graft technique in which vein graft conduits are pulled inside-out before anastomosis with proximal and distal nerve stumps. This technique creates an autogenous vein conduit with the collagen-rich adventitial surface exposed to the regenerating axons. The inside-out technique is a fast and simple modification of the standard vein graft technique and produces an accelerated rate of nerve regeneration and significantly earlier myelination compared with the results obtained from the use of polyethylene nerve guides and standard vein graft conduits.

The culmination of any operation is a healed wound. Failure of a wound to heal increases time spent in the hospital and the expense, and may start a cascade of progressive complications. Thus, it is important to optimize as many factors as possible before operation and to have the knowledge and resources to deal with wound problems should they occur. This approach involves understanding basic wound healing with its multiple factors, including nutrition, and knowing how to deal with potential adverse factors in wound healing, such as chemotherapy, corticosteroids, and radiation.

In a ten-year review (1978 to 1988), ten ulnar artery aneurysms in nine male patients were studied. Blunt trauma led to 70%, penetrating trauma to 20%, and 10% had no history of trauma. Three cases were seen as asymptomatic palmar masses with brief antecedent histories of 4 weeks or less. Seven patients with aneurysms had persistent vascular hand symptoms for 6 weeks or longer. All seven symptomatic lesions proved to be sources of emboli. Diagnostic arteriography was done in all cases. Intraoperative digital plethysmography aided in operative decisions regarding the necessity for microvascular reconstruction. Five aneurysms were resected with end-to-end ulnar artery microvascular repairs, four resected without repair, and a single case treated with long-term anticoagulants. Follow-up, averaging 40 months, showed uniform improvement in vascular symptoms, with no loss of jeopardized tissues. Ulnar artery aneurysms, well studied preoperatively and intraoperatively, can be treated successfully with selective microvascular reconstruction.

Cell mediated lympholysis (CML) has been proposed as an in vitro model of the rejection process that results from transplantation of allogeneic tissue. To date, the absolute frequencies of cytotoxic T lymphocytes (CTL) and their precursors (CTL.P) have not been directly estimated in man because of technical difficulties. Through optimizing the conditions for radiometric detection of 51Cr release and the attendant improvement in CML sensitivity, direct CTL frequency estimates have been determined in peripheral blood (PBL), spleen (SPL), and lymph nodes (LNC) after in vitro allostimulation using unrelated human cells and limiting dilution assays. The mean frequency of CTL generated from PBL is 1 in 826 cells (0.121% +/- 0.101%) which, from preliminary experiments, is significantly greater than that generated from either LNC or SPL (p less than 0.05). With restimulation of primed cells on day 10, the frequency of CTL generated from PBL was increased 400%. The CTL.P frequency (0.0064% +/- 0.0050%) was approximately 5% of the corresponding CTL frequency. The CTL.P frequencies were found to be minimal estimates as both accessory "filler" cells and T cell growth factors increased the level of detection of CTL.P an average of threefold. The limiting cell dilution assay as detailed in this report should be a powerful tool for defining the cellular requirements and related factors necessary for optimal induction of a CTL response and should provide the means for determination of the immunogenetic requirements and the allospecificity of human cytotoxic lymphocytes.

Serial studies were made of the membranes of the erythrocytes and the vesicles shed during storage of blood in polyvinyl chloride containers for 35 days in citrate-phosphate-dextrose-adenine anticoagulant. Special precautions were taken to eliminate artifacts created by contaminating leukocytes, platelets and red blood cell ghosts. A total of 15.6% of the cholesterol and 5.2% of the phospholipids of the membranes was lost with no gross change in the gel electrophoretic patterns. The quantity of vesicles found in the supernatant plasma increased during storage and their membranes were characterized by the absence of spectrin, ankyrin, and periodic acid Schiff bands 2 and 3. The ratio of lipids to protein in the vesicles increased as they accumulated perhaps reflecting a rearrangement of the erythrocyte membrane constituents during prolonged maintenance at 4 degrees C.