Long-term neural regeneration following injury to the peroneal branch of the sciatic nerve in sheep.

Peripheral nerves (PNs) are frequently injured as a result of trauma or disease. Development of therapies to regenerate PNs requires the use of animal models, typically beginning in rodents and progressing to larger species. There are several large animal models of PN regeneration that each has their benefits and drawbacks. Sheep have been used in PN studies due to their similarities in body weight to humans and the ease and lesser expense in their care and housing relative to other species. We have investigated the use of sheep for studies of PN regeneration and have developed and tested an injury model in the peroneal branch of the sciatic nerve. Three experimental groups were tested on mature sheep: a bisection; a 5-cm reverse autograft; and sham surgery. Protocols were developed for the post-operative care for animals with this injury, and regeneration was tracked for extended time points via compound muscle action potentials (CMAPs) and endpoint assessments of nerve morphometry, muscle mass and muscle fibrosis. Results indicate the practical viability of this PN injury model and show distinctions in the degree and rate of regeneration between bisection and reverse autograft that persisted 14 months. This long-term study shows bisections lead to significantly improved CMAPS and muscle mass and lesser muscle fibrosis as compared to reverse autograft. The persistence of these discernable changes between two relatively similar experimental groups out to extended time points is an indication of the sensitivity of this nerve section and its potential applicability for comparative studies.

Sexual Dimorphism in Lesion Size and Sensorimotor Responses Following Spinal Cord Injury.

Spinal cord injury (SCI) is a devastating disorder, which impacts the lives of millions of people worldwide with no clinically standardized treatment. Both pro-recovery and anti-recovery factors contribute to the overall outcome after the initial SCI. Sex is emerging as an important variable, which can affect recovery post-SCI. Contusion SCI at T10 was generated in male and female rats. Open-field Basso, Beattie, Bresnahan (BBB) behavioral test, Von Frey test, and CatWalk gate analysis were performed. Histological analysis was performed at the 45-day post-SCI end point. Male/female differences in sensorimotor function recovery, lesion size, and the recruitment of immune cells to the lesion area were measured. A group of males with less severe injuries was included to compare the outcomes for severity. Our results show that both sexes with the same injury level plateaued at a similar final score for locomotor function. Males in the less severe injury group recovered faster and plateaued at a higher BBB score compared to the more severe injury group. Von Frey tests show faster recovery of sensory function in females compared to both male groups. All three groups exhibited reduced mechanical response thresholds after SCI. The lesion area was significantly larger in the male group with severe injury than in females, as well as in males of less severe injury. No significant differences in immune cell recruitment were identified when comparing the three groups. The faster sensorimotor recovery and significantly smaller lesion area in females potentially indicate that neuroprotection against the secondary injury is a likely reason for sex-dependent differences in functional outcomes after SCI.

A Long-Term Pilot Study on Sex and Spinal Cord Injury Shows Sexual Dimorphism in Functional Recovery and Cardio-Metabolic Responses.

More than a quarter of a million individuals in the US live with spinal cord injury (SCI). SCI disrupts neural circuitry to vital organs in the body. Despite severe incidences of long-term peripheral complications from SCI, the cardio-metabolic consequences and divergences in sex-related responses are not well described. We examined the effects of SCI on functional recovery, cardiac structure and function, body composition, and glucose metabolism on adult female and male Sprague Dawley (SD) rats. SCI was induced at T10 via contusion. Measured outcomes include behavioral assessment, body weight, dual-energy X-ray absorptiometry (DEXA) for body composition, echocardiography for cardiac structure and function, intraperitoneal glucose tolerance test (IPGTT) for glucose metabolism, insulin tolerance test (ITT), and histology of cardiac structure at the endpoint. There was a decrease in body fat percentage in both sexes, with SCI females disproportionately affected in percent body fat change. Left ventricular internal diameter during systole (LVIDs) was decreased in SCI females more than in SCI males. No significant differences in glucose metabolism were observed up to 20 weeks post-injury (PI). These data show significant cardio-metabolic differences as a consequence of SCI and, furthermore, that sex is an underlying factor in these differences.

Analysis of N- and O-Linked Glycosylation: Differential Glycosylation after Rat Spinal Cord Injury.

Glycosylation is a fundamental cellular process that has a dramatic impact on the functionality of glycoconjugates such as proteins or lipids and mediates many different biological interactions including cell migration, cellular signaling, and synaptic interactions in the nervous system. In spinal cord injury (SCI), all of these cellular processes are altered, but the potential contributions of glycosylation changes to these alterations has not been thoroughly investigated. We studied the glycosylation of injured spinal cord tissue from rats that received a contusion SCI. The N- and O-linked glycosylation was assessed at 3 and 14 days post-injury (DPI), and compared with uninjured control and time-matched sham spinal tissue. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and tandem MS (MS/MS) were performed to analyze carbohydrate structures. Results revealed diverse and abundant glycosylation in all groups, with some carbohydrate structures differentially produced in SCI animals compared with uninjured controls and shams. One such change occurred in the abundance of the Sda structure, Neu5Ac-α-(2,3)-[GalNAc-ß-(1,4)-]Gal-ß-(1,4)-GlcNAc, which was increased in SCI samples compared with shams and non-injured controls. Immunohistochemistry (IHC) and western blot were performed on SCI and sham samples using the CT1 antibody, which recognizes the terminal trisaccharide of Sda with high specificity. Both of these metrics confirmed elevated Sda structure in SCI tissue, where IHC further showed that Sda is expressed mainly by microglia. The results of these studies suggest that SCI causes a significant alteration in N- and O-linked glycosylation.