Induced NB-3 Limits Regenerative Potential of Serotonergic Axons after Complete Spinal Transection

Do Pharmacological Treatments Act in Collaboration with Rehabilitation in Spinal Cord Injury Treatment? A Review of Preclinical Studies

There is no choice other than rehabilitation as a practical medical treatment to restore impairments or improve activities after acute treatment in people with spinal cord injury (SCI); however, the effect is unremarkable. Therefore, researchers have been seeking effective pharmacological treatments. These will, hopefully, exert a greater effect when combined with rehabilitation. However, no review has specifically summarized the combinatorial effects of rehabilitation with various medical agents. In the current review, which included 43 articles, we summarized the combinatorial effects according to the properties of the medical agents, namely neuromodulation, neurotrophic factors, counteraction to inhibitory factors, and others. The recovery processes promoted by rehabilitation include the regeneration of tracts, neuroprotection, scar tissue reorganization, plasticity of spinal circuits, microenvironmental change in the spinal cord, and enforcement of the musculoskeletal system, which are additive, complementary, or even synergistic with medication in many cases. However, there are some cases that lack interaction or even demonstrate competition between medication and rehabilitation. A large fraction of the combinatorial mechanisms remains to be elucidated, and very few studies have investigated complex combinations of these agents or targeted chronically injured spinal cords.

Contactin-6-deficient male mice exhibit the abnormal function of the accessory olfactory system and impaired reproductive behavior

INTRODUCTION

Contactin-6 (CNTN6), also known as NB-3, is a neural recognition molecule and a member of the contactin subgroup of the immunoglobulin superfamily. Gene encoding CNTN6 is expressed in many regions of the neural system, including the accessory olfactory bulb (AOB) in mice. We aim to determine the effect of CNTN6 deficiency on the function of the accessory olfactory system (AOS).

METHODS

We examined the effect of CNTN6 deficiency on the reproductive behavior of male mice through behavioral experiments such as urine sniffing and mate preference tests. Staining and electron microscopy were used to observe the gross structure and the circuitry activity of the AOS.

RESULTS

Cntn6 is highly expressed in the vomeronasal organ (VNO) and the AOB, and sparsely expressed in the medial amygdala (MeA) and the medial preoptic area (MPOA), which receive direct and/or indirect projections from the AOB. Behavioral tests to examine reproductive function in mice, which is mostly controlled by the AOS, revealed that Cntn6^-/- adult male mice showed less interest and reduced mating attempts toward estrous female mice in comparison with their Cntn6^+/+ littermates. Although Cntn6^-/- adult male mice displayed no obvious changes in the gross structure of the VNO or AOB, we observed the increased activation of granule cells in the AOB and the lower activation of neurons in the MeA and the MPOA as compared with Cntn6^+/+ adult male mice. Moreover, there were an increased number of synapses between mitral cells and granule cells in the AOB of Cntn6^-/- adult male mice as compared with wild-type controls.

CONCLUSION

These results indicate that CNTN6 deficiency affects the reproductive behavior of male mice, suggesting that CNTN6 participated in normal function of the AOS and its ablation was involved in synapse formation between mitral and granule cells in the AOB, rather than affecting the gross structure of the AOS.

NB-3 expression in endothelial cells contributes to the maintenance of blood brain barrier integrity in a mouse high-altitude cerebral edema model

NB-3, a member of the contactin/F3 subgroup in the immunoglobulin superfamily, plays an important role in neural development and injury recovery. The blood brain barrier (BBB) is typically involved in the pathophysiology of neural disorders, such as hypoxic-ischemic brain injury. Our previous research found that NB-3 protects against brain damage in a mouse stroke model. However, its role in high-altitude disorders caused by hypobaric hypoxia exposure remains unknown. In the present study, we found that NB-3 was expressed in brain microvascular endothelial cells (BMECs) and responded to hypoxia stimulation. Conditional knockout of NB-3 in endothelial cells increased BBB leakage and downregulated tight junction proteins in vivo. NB-3 deficiency promoted the downregulation of tight junction proteins under Lipopolysaccharide (LPS)/hypoxia stimulation. Conversely, overexpression or supplementation with NB-3 alleviated endothelial barrier injuries. Transcriptome sequencing showed that NB-3 regulated various cell attachment genomic changes, including the Notch signaling pathway. Blocking the Notch signaling pathway increased VEGF/VEGFR2 pathway activation induced by LPS/hypoxia. Collectively, we present evidence that NB-3 plays key roles in maintaining BBB integrity under high-altitude cerebral edema conditions.