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OBJECTIVE. The cost and low success rates of the neurological drug development pipeline have diverted the pharmaceutical industry to ‘nerve-on-a-chip’ systems as preclinical models to streamline drug development. We present a novel micro-engineered 3D hydrogel platform for the culture of myelinated embryonic peripheral neural tissue to serve as an effective in vitro model for electrophysiological and histological analysis that could be adopted for preclinical testing. APPROACH. Dorsal root ganglions (DRG) from 15-day old embryonic rats were cultured in 3D hydrogel platforms. The interaction between Schwann cells (SC) and neurons during axonal development and regeneration affects the direction of growth and the synthesis of myelin sheaths. Induction of myelination was performed with two approaches: the addition of exogenous SC and promoting migration of endogenous SC. MAIN RESULTS. Histological analysis of the preparation utilizing exogenous SC showed aligned, highly fasciculated axonal growth with noticeable myelin sheaths around axons. Separately, electrophysiological testing of the preparation utilizing endogenous SC showed increased amplitude of the compound action potential and nerve conduction velocity in the presence of ascorbic acid (AA) SIGNIFICANCE. This platform has immense potential to be a useful and translatable in vitro testing tool for drug discovery and myelination studies.

Introduction: Oxidative stress has been shown to play an important role in the pathogenesis of intracranial aneurysm (IA). Sulforaphane is an isothiocyanate that exhibits antioxidant properties via the Nrf2 transcription factor. We tested whether sulforaphane would protect against IA formation and subarachnoid hemorrhage (SAH) in a mouse model. Methods: C57BL/6 mice were treated intraperitoneally with either 0.5mg/kg/day of sulforaphane (treatment group, n = 32) or a vehicle solution (control group, n = 26) prior to being subjected to a well-established IA induction protocol involving unilateral nephrectomy, mineralocorticoid administration, and intracranial injection of elastase. Sulforaphane/vehicle treatments were begun seven days prior to elastase injection, and continued daily for the duration of the experiment. Animals were followed for 14 days until sacrifice, with measurement of the number of aneurysms formed and ruptured in each animal. Intracranial vessel tissue was collected, pooled, and analyzed using real-time PCR (RT-PCR) with experiments performed in triplicate (n = 3). Results: There was a lower incidence of IA in the treatment group (1.06 +/- 0.24 per animal) than in the control group (1.54 +/- 0.33), but this trend did not reach significance. The incidence of SAH in the treatment group (0.53 +/- 0.09 per animal) was approximately 50% lower than in the control group (1.08 +/- 0.21, p = 0.012). RT-PCR showed significant (p < 0.05) differences in the expression of interferon gamma, matrix metalloproteinase 9, collagen Ia2, interleukin-6, myosin heavy chain, and SM22 between the treatment and control groups. Conclusions: Treatment with sulforaphane resulted in a significantly lower incidence of SAH in a mouse model of IA. The expression of genes involved in inflammation and extracellular matrix remodeling were altered by sulforaphane administration.

The influence of age on rotator cuff function and muscle structure remains poorly understood. We hypothesize that normal aging influences rotator cuff function, muscle structure, and regulatory protein expression in an established rat model of aging.Seventeen rats were obtained from the National Institute on Aging. The supraspinatus muscles in 11 middle-aged (12 months old) and 6 old (28 months old) rats were studied for age-related changes in rotator cuff neuromuscular function by in vivo muscle force testing and electromyography (EMG). Changes in muscle structure and molecular changes were assessed with quantitative immunohistochemistry for myogenic determination factor 1 (MyoD) and myogenic factor 5 (Myf5) expression.Old animals revealed significantly decreased peak tetanic muscle force at 0.5 N and 0.7 N preload tension (P.05). The age of the animal accounted for 20.9% of variance and significantly influenced muscle force (P = .026). Preload tension significantly influenced muscle force production (P.001) and accounted for 12.7% of total variance. There was regional heterogeneity in maximal compound motor action potential (CMAP) amplitude in the supraspinatus muscle; the proximal portion had a significantly higher CMAP than the middle and distal portions (P.05). The expression of muscle regulatory factors MyoD and Myf5 was significantly decreased in old animals compared with middle-aged animals (P.05).The normal aging process in this rat model significantly influenced contractile strength of the supraspinatus muscle and led to decreased expression of muscle regulatory factors. High preload tensions led to a significant decrease in force production in both middle-aged and old animals.

Peripheral nerve injuries requiring surgery can be repaired by autograft, the clinical "gold standard", allograft, or nerve conduits. Most published clinical studies show the effectiveness of nerve conduits in small size defects in sensory nerves. Many preclinical studies suggest that peripheral nerve regeneration through conduits can be enhanced and repair lengths increased with the use of a biomaterial filler in the conduit lumen. We have previously shown that a luminal hydrogel filler derived from human hair keratin (HHK) can improve electrophysiological and histological outcomes in mouse, rabbit, and non-human primate nerve injury models, but insight into potential mechanisms has been lacking. Based on the premise that a keratin biomaterial (KOS) hydrogel provides an instantaneous structural matrix within the lumen, the current study compares the cellular behavior elicited by KOS hydrogel to Matrigel (MAT) and saline (SAL) conduit fillers in a 1 cm rat sciatic nerve injury model at early stages of regeneration. While there was little difference in initial cellular influx, the KOS group showed earlier migration of dedifferentiated Schwann cells (SC) from the proximal nerve end compared to the other groups. The KOS group also showed faster SC dedifferentiation and myelin debris clearance, and decreased macrophage infiltration during Wallerian degeneration of the distal nerve tissue.

Background Intracranial aneurysms (IA) are increasingly recognized as a disease driven by chronic inflammation. Recent research has identified key mediators and processes underlying IA pathogenesis, but mechanistic understanding remains incomplete. Lymphocytic infiltrates have been demonstrated in patient IA tissue specimens and have also been shown to play an important role in abdominal aortic aneurysms (AAA) and related diseases such as atherosclerosis. However, no study has systematically examined the contribution of lymphocytes in a model of IA. Methods Lymphocyte-deficient (Rag1) and wild-type (WT; C57BL/6 strain) mice were subjected to a robust IA induction protocol. Rates of IA formation and rupture were measured, and cerebral artery tissue was collected and utilized for histology and gene expression analysis. Results At 2 weeks, the Rag1 group had significantly fewer IA formations and ruptures than the WT group. Histological analysis of unruptured IA tissue showed robust B and T lymphocyte infiltration in the WT group, while there were no differences in macrophage infiltration, IA diameter, and wall thickness. Significant differences in interleukin-6 (IL-6), matrix metalloproteinases 2 (MMP2) and 9 (MMP9), and smooth muscle myosin heavy chain (MHC) were observed between the groups. Conclusions Lymphocytes are key contributors to IA pathogenesis and provide a novel target for the prevention of IA progression and rupture in patients.

A human hair keratin biomaterial hydrogel scaffold was evaluated as a nerve conduit luminal filler following median nerve transection injury in 10 Macaca fascicularis nonhuman primates (NHP). A 1 cm nerve gap was grafted with a NeuraGen® collagen conduit filled with either saline or keratin hydrogel and nerve regeneration was evaluated by electrophysiology for a period of 12 months. The keratin hydrogel-grafted nerves showed significant improvement in return of compound motor action potential (CMAP) latency and recovery of baseline nerve conduction velocity (NCV) compared with the saline-treated nerves. Histological evaluation was performed on retrieved median nerves and abductor pollicis brevis (APB) muscles at 12 months. Nerve histomorphometry showed a significantly larger nerve area in the keratin group compared with the saline group and the keratin APB muscles had a significantly higher myofiber density than the saline group. This is the first published study to show that an acellular biomaterial hydrogel conduit filler can be used to enhance peripheral nerve regeneration and motor recovery in an NHP model.

A preceding study analysed how the topology of network motifs affects the overall rate of the underlying biochemical processes. Surprisingly, it was shown that topologically non-isomorphic motifs can still be isodynamic in the sense that they exhibit the exact same performance rate. Because of the high prevalence of feed-forward functional modules in biological networks, one may hypothesize that evolution tends to favour motifs with faster dynamics. As a step towards ranking the efficiency of feed-forward network motifs, we use a linear flow model to prove theorems establishing that certain classes of motifs are isodynamic. In partitioning the class of all motifs on n nodes into equivalence classes based upon their dynamics, we establish a basis for comparing the efficiency/performance rates of different motifs. The potential biological importance of the theorems is briefly discussed and is the subject of an ongoing large-scale project.