Bioengineering approaches for nerve graft revascularization: Current concepts and future directions.

Peripheral nerve injury (PNI) is the most common neurological injury in civilian and military injuries, with over 360,000 PNI procedures performed in the US yearly. Segmental loss of nerve tissue results in a nerve gap precluding a tension-free primary repair, and in these cases, interpositional autologous or acellular nerve allografts are used to bridge the gap. Graft ischemia time is a critical factor in achieving satisfactory nerve regeneration. Rapid nerve graft revascularization is essential in order to sustain Schwann cell growth which in turn is crucial for axonal regeneration. Currently, nerve autografts are considered the gold standard for segmental nerve gaps but are associated with several disadvantages such as limited supply of expendable donor tissue, increased operative time, and donor site morbidity. Hence, readily available, off-the-shelf nerve allografts or scaffolds are being investigated since they provide advantages such as a virtually limitless sourcing, a wide variety of sizes to match recipient nerves, and no donor site morbidity. New, exciting advances in tissue engineering to augment revascularization of nerve allografts or conduits have been investigated. Strategies include pro-angiogenic mesenchymal stem cells, extracellular vesicles, functionalized scaffolds, bioactive peptides, and three-dimensional bioprinting. This article discusses these bioengineering advances and future strategies aimed at enhancing nerve graft and scaffold revascularization. This article is categorized under: Neurological Diseases > Biomedical Engineering Neurological Diseases > Molecular and Cellular Physiology.

Engineering extracellular vesicles for Alzheimer's disease: An emerging cell-free approach for earlier diagnosis and treatment.

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder affecting over five million people globally and has no established cure. Current AD-related treatments only alleviate cognitive and behavioral symptoms and do not address disease onset or progression, underlining the unmet need to create an effective, innovative AD therapeutic. Extracellular vesicles (EVs) have emerged as a new class of nanotherapeutics. These secreted, lipid-bound cellular signaling carriers show promise for potential clinical applications for neurodegenerative diseases like AD. Additionally, analyzing contents and characteristics of patient-derived EVs may address the unmet need for earlier AD diagnostic techniques, informing physicians of altered genetic expression or cellular communications specific to healthy and diseased physiological states. There are numerous recent advances in regenerative medicine using EVs and include bioengineering perspectives to modify EVs, target glial cells in neurodegenerative diseases like AD, and potentially use EVs to diagnose and treat AD earlier. This article is categorized under: Neurological Diseases > Biomedical Engineering Neurological Diseases > Molecular and Cellular Physiology Neurological Diseases > Stem Cells and Development.