Alterations of oligodendrocyte progenitor cells (OPCs) with survival time in humans following high impact brain trauma

BACKGROUND

As there is a lack of comprehensive literature regarding the molecular environment of the human brain emphasizing on oligodendrocyte progenitor cells (OPCs) following high impact brain trauma. The protagonist of OPCs post severe traumatic brain injury (sTBI) provides a significant thrust towards estimating time elapsed since trauma as well as developing novel therapeutic approaches. The present study was carried out to study post trauma alterations pertaining to myelin sheath and oligodendrocyte response with survival time.

MATERIALS AND METHODS

In the present study, victims (both male and female) of sTBI (n = 64) were recruited and contrasted with age and gender matched controls (n = 12). Post mortem brain samples from corpus callosum and grey white matter interface were collected during autopsy examination. Extent of myelin degradation and response of OPC markers Olig-2 and PDGFR-α were evaluated using immunohistochemistry and qRT-PCR. STATA 14.0 statistical software was used for data analysis with P-value<0.05 considered statistically significant.

RESULTS

Timewise qualitative correlation with extent of demyelination performed using LFB-PAS/IHC-MBP, IHC Olig-2 and mRNA expression revealed tendency towards remyelination in both corpus callosum and grey white matter interface. Number of Olig-2 positive cells was significantly higher in sTBI group as compared to control group (P-value: 0.0001). Moreover, mRNA expression studies of Olig-2 showed significant upregulation in sTBI patients. mRNA expression of Olig-2 and PDGFR-α in sTBI patients showed significant variation with respect to survival time (p value:0.0001).

CONCLUSION

Detailed assessment of post TBI changes implementing various immunohistochemical and molecular techniques shall potentially reveal intriguing and important inferences in medicolegal practices and neurotherapeutics.

Analysis of platelet-derived growth factor receptor A and oligodendrocyte transcription factor 2 markers following Hydroxychloroquine administration in animal induced multiple sclerosis model

It has been shown that following demyelination, Oligodendrocyte Progenitor Cells (OPCs) migrate to the lesion site and begin to proliferate, and differentiate. This study aimed to investigate the effects of Hydroxychloroquine (HCQ) on the expression of OLIG-2 and PDGFR-α markers during the myelination process. C57BL/6 mice were fed cuprizone pellets for 5 weeks to induce demyelination and return to a normal diet for 1 week to stimulate remyelination. During the Phase I all of the animals except CPZ and Vehicle groups were exposed to HCQ (2.5, 10, and 100 mg/kg) via drinking water. At the end of the study, animals were euthanized, perfused and the brain samples were assessed for myelination and immunohistochemistry evaluation. What is remarkable is the high rate of Olig2 + cells in the groups treated with 10 and 100 mg/kg HCQ in the demyelination phase and its decreasing trend in the remyelination phase. However, there was no significant difference between groups during phase I and Phase II based on the percentage of olig-2+/total cells in the corpus callosum region. The number of PDGFR-α+ cells in the group treated with 10 mg/kg HCQ was significant in the first phase (p value < 0.05). Considering that the 100 mg/kg HCQ group had the highest level of PDGFR-α as well as the highest level of myelin repair in LFB staining, it could be inferred that it was the most effective dose in inducing proliferation and migration of OPCs.

Bee Venom-Derived BBB Shuttle and its Correlation with Oligodendrocyte Proliferation Markers in Mice Model of Multiple Sclerosis

Multiple sclerosis is a chronic demyelinating disease with a functional disturbance in the immune system and axonal damages. It was shown that Apamin as a blood-brain barrier shuttle acts as a Ca2+ activated K+ channels (SK channels) blocker. In this study, the effects of Apamin on oligodendrocyte differentiation markers were evaluated on an induced model of MS. Briefly, C57BL/6 male mice (22 ± 5 g) except the control group were fed with 0.2% (w/w) cuprizone pellets for 6 weeks. After cuprizone withdrawal, mice were divided randomly into six groups. Apamin (100 µg/kg/BW) was administered intraperitoneally as a co-treatment during phase I (demyelination) or post-treatment phase II (remyelination) twice a week. Mice were anesthetized, perfused with phosphate-buffered saline, then fixed brains were coronally sectioned and the changes in oligodendrocytes markers such as Olig2, PDGFR-α, and BrdU incorporation were assessed by immunohistochemistry assay. Apamin administration increased Olig2+ cells in phase I as compared to the control group (p < 0.0001). Also, a decreasing trend in PDGFRa+ cells observed after cuprizone withdrawal (p < 0.001). 5-Bromo-2'-deoxyuridine (BrdU) incorporation test was confirmed stimulation of oligodendrocyte progenitor cell proliferation in phase I in the Apamin exposed group (p < 0.0001), especially at the subventricular zone. This study highlights the potential therapeutic effects of Apamin as a bee venom-derived peptide on oligodendrocyte precursor proliferation and elevation in myelin content in an oxidative induced multiple sclerosis model due to cuprizone exposure.

Continuous tamoxifen delivery improves locomotor recovery 6h after spinal cord injury by neuronal and glial mechanisms in male rats

No treatment is available for patients with spinal cord injury (SCI). Patients often arrive to the hospital hours after SCI suggesting the need of a therapy that can be used on a clinically relevant window. Previous studies showed that Tamoxifen (TAM) treatment 24h after SCI benefits locomotor recovery in female rats. Tamoxifen exerts beneficial effects in male and female rodents but a gap of knowledge exists on: the therapeutic window of TAM, the spatio-temporal mechanisms activated and if this response is sexually dimorphic. We hypothesized that TAM will favor locomotor recovery when administered up-to 24h after SCI in male Sprague-Dawley rats. Rats received a thoracic (T10) contusion using the MACSIS impactor followed by placebo or TAM (15mg/21days) pellets in a therapeutic window of 0, 6, 12, or 24h. Animals were sacrificed at 2, 7, 14, 28 or 35days post injury (DPI) to study the molecular and cellular changes in the acute and chronic stages. Immediate or delayed therapy (t=6h) improved locomotor function, increased white matter spared tissue, and neuronal survival. TAM reduced reactive gliosis during chronic stages and increased the expression of Olig-2. A significant difference was observed in estrogen receptor alpha between male and female rodents from 2 to 28 DPI suggesting a sexually dimorphic characteristic that could be related to the behavioral differences observed in the therapeutic window of TAM. This study supports the use of TAM in the SCI setting due to its neuroprotective effects but with a significant sexually dimorphic therapeutic window.