The reaction of glial progenitor cells in remyelination following ethidium bromide-induced demyelination in the mouse spinal cord

Laser-activated autologous adipose tissue-derived stromal vascular fraction restores spinal cord architecture and function in multiple sclerosis cat model

BACKGROUND

Multiple sclerosis (MS) is the most frequent non-traumatic neurological debilitating disease among young adults with no cure. Over recent decades, efforts to treat neurodegenerative diseases have shifted to regenerative cell therapy. Adipose tissue-derived stromal vascular fraction (SVF) comprises a heterogeneous cell population, considered an easily accessible source of MSCs with therapeutic potential in autoimmune diseases. This study aimed to assess the regenerative capacity of low-level laser-activated SVF in an MS cat model.

METHODS

Fifteen adult Persian cats were used in this study: Group I (control negative group, normal cats), Group II (EB-treated group, induced for MS by ethidium bromide (EB) intrathecal injection), and Group III (SVF co-treated group, induced for MS then treated with SVF on day 14 post-induction). The SVF was obtained after digesting the adipose tissue with collagenase type I and injecting it intrathecal through the foramen magnum.

RESULTS

The results showed that the pelvic limb's weight-bearing locomotion activity was significantly (P ≤ 0.05) recovered in Group III, and the Basso, Beattie, and Bresnahan (BBB) scores of hindlimb locomotion were significantly higher in Group III (14 ± 0.44) than Group II (4 ± 0.31). The lesion's extent and intensity were reduced in the magnetic resonance imaging (MRI) of Group III. Besides, the same group showed a significant increase in the expression of neurotrophic factors: BDNF, SDF and NGF (0.61 ± 0.01, 0.51 ± 0.01 and 0.67 ± 0.01, respectively) compared with Group II (0.33 ± 0.01, 0.36 ± 0.006 and 0.2 ± 0.01, respectively). Furthermore, SVF co-treated group revealed a significant (P ≤ 0.05) increase in oligodendrocyte transcription factor (Olig2) and myelin basic protein (4 ± 0.35 and 6 ± 0.45, respectively) that was decreased in group II (1.8 ± 0.22 and 2.9 ± 0.20, respectively). Moreover, group III showed a significant (P ≤ 0.05) reduction in Bax and glial fibrillary acidic protein (4 ± 0.53 and 3.8 ± 0.52, respectively) as compared with group II (10.7 ± 0.49 and 8.7 ± 0.78, respectively). The transmission electron microscopy demonstrated regular more compact, and markedly (P ≤ 0.05) thicker myelin sheaths (mm) in Group III (0.3 ± 0.006) as compared with group II (0.1 ± 0.004). Based on our results, the SVF co-treated group revealed remyelination and regeneration capacity with a reduction in apoptosis and axonal degeneration.

CONCLUSION

SVF is considered an easy, valuable, and promising therapeutic approach for treating spinal cord injuries, particularly MS.

Evaluation of treatment of experimentally induced canine model of multiple sclerosis using laser activated non-expanded adipose derived stem cells

Multiple sclerosis (MS) is a progressive demyelinating disease of the central nervous system that destroys oligodendrocytes. This work aims to evaluate the treatment of experimentally induced MS in dogs using laser activated non-expanded adipose derived stem cells. The results showed amelioration of the clinical signs over time confirmed by the resolution of the previous lesions on MRI. Positive migration of the injected cells to the site of lesion, increased remyelination detected by Myelin Basic Proteins, positive differentiation into Olig2 positive oligodendrocytes, prevented the glial scar formation and restored axonal architecture. The study concluded that treatment using laser activated stem cells holds a promising therapeutic option for treatment of MS in a canine model.

Myelinosome formation represents an early stage of oligodendrocyte damage in multiple sclerosis and its animal model

Oligodendrocyte damage is a central event in the pathogenesis of the common neuroinflammatory condition, multiple sclerosis (MS). Where and how oligodendrocyte damage is initiated in MS is not completely understood. Here, we use a combination of light and electron microscopy techniques to provide a dynamic and highly resolved view of oligodendrocyte damage in neuroinflammatory lesions. We show that both in MS and in its animal model structural damage is initiated at the myelin sheaths and only later spreads to the oligodendrocyte cell body. Early myelin damage itself is characterized by the formation of local myelin out-foldings-'myelinosomes'-, which are surrounded by phagocyte processes and promoted in their formation by anti-myelin antibodies and complement. The presence of myelinosomes in actively demyelinating MS lesions suggests that oligodendrocyte damage follows a similar pattern in the human disease, where targeting demyelination by therapeutic interventions remains a major open challenge.

Functional consequences of ethidium bromide demyelination of the mouse ventral spinal cord

Ethidium bromide (EB) has been extensively used in the rat as a model of spinal cord demyelination. However, this lesion has not been addressed in the adult mouse, a model with unlimited genetic potential. Here we characterize behavioral function, inflammation, myelin status and axonal viability following bilateral injection of 0.20 mg/mL ethidium bromide or saline into the ventral white matter (VWM) of female C57Bl/6 mice. EB-induced VWM demyelination significantly reduced spared VWM and Basso Mouse Scale (BMS) scores persisting out to 2 months. Chronic hindlimb dysfunction was accompanied by a persistent inflammatory response (demonstrated by CD45(+) immunofluorescence) and axonal loss (demonstrated by NF-M immunofluorescence and electron microscopy; EM). These cellular responses differ from the rat where inflammation resolves by 3-4 weeks and axon loss is minimal following EB demyelination. As these data suggest that EB-injection in the mouse spinal cord is a non-remyelinating lesion, we sought to ask whether wheel running could promote recovery by enhancing plasticity of local lumbar circuitry independent of remyelination. This did not occur as BMS and Treadscan assessment revealed no significant effect of wheel running on recovery. However, this study defines the importance of descending ventral motor pathways to locomotor function in the mouse as VWM loss results in a chronic hindlimb deficit.

Magnetic stimulation influences injury-induced migration of white matter astrocytes

This study investigates the effects and underlying mechanism of magnetic stimulation on injury-induced migration of white matter astrocytes. Twenty-four adult healthy SD rats were selected to inject 0.5 ml of 1% ethidium bromide (EB) in PBS into the dorsal spinal cord funiculus on the left side at the T10-11 level to make located spinal cord injury models. Then they were randomly divided into four groups (A, B, C, and D). Groups A, B, C, and D were exposed to 1 Hz pulsed magnetic stimulation underwent 5-min sessions on 14 consecutive days at the following levels: 0T (Group A) 1.9x40% T (Group B); 1.9x80% T (Group C); 1.9x100% T (Group D). On day 14 after stimulation, the rats were killed and the expression of glial fibrillary acidic protein (GFAP), microtubule associated protein-2 (MAP-2), extracellular signal-regulated kinase1/2 (ERK1/2), and the volume of holes were detected with immunohistochemistry. Quantitative analysis of the expression of GFAP, MAP-2, and ERK1/2 were performed with the image analysis system. With the increase of magnetic stimulation intensity, the volume of hole decreased at day 14 (P<0.05). In lesion areas, the expression of GFAP and ERK1/2 could be seen, while that of MAP-2 did not change before and after magnetic stimulation. Significant difference was revealed in the expression of GFAP, ERK1/2 among the four groups. It was significantly higher in the magnetic stimulation groups than that in the control group (P<0.05). After magnetic stimulation, astrocytes migrated into the hole. U0126, a potent and selective MEK1/2 inhibitor, inhibited up-regulation of pERK1/2 which was stimulated by magnetic stimulation. These data indicate that magnetic stimulation increases the migratory capacity of reactive white matter astrocytes in the injured center nervous system, which may be associated with activation of MEK1,2/ERK mitogenic pathway.

OSP-Immunofluorescent remyelinating oligodendrocytes in the brainstem of toxically-demyelinated Wistar rats

Central nervous system (CNS) remyelination following toxically-induced demyelination is a well known process. Oligodendrocytes constitute the bulk of the myelinating cells in the brain whereas Schwann cells overwhelm oligodendrocytes numbers in spinal cord remyelination. Despite the common knowledge of these facts, we still do not know completely the origin of both remyelinating cells. The present study investigated the participation of mature oligodendrocytes in remyelination after ethidium-bromide (EB) induced demyelination in the brainstem of normal and cyclosporin A-immunosuppressed Wistar rats. Thirty adult female rats were divided into three experimental groups. In group 1 the rats received a single intracisternal injection of 10 muL of 0.1% ethidium bromide (EB) in 0.9% saline (n=10); in group 2 the rats received the EB injection while immunosuppressed with cyclosporin A (n=10); in group 3 the rats received a single 10 muL injection of 0.9% saline while treated with cyclosporin A. The rats were killed at 15, 21 and 31 days after injection. Within the EB lesions, from 15 days onward many cells within the periphery of the lesions stained positive for OSP (oligodendrocyte specific protein) a marker for mature oligodendrocytes and myelin. This cell marking signals that, at least, part of the process of repairing the myelin sheaths is carried out by mature cells of the oligodendrocyte lineage.

Intracellular calcium-binding protein S100A4 influences injury-induced migration of white matter astrocytes

Astrocytes play a crucial role in central nervous system (CNS) pathophysiology. White and gray matter astrocytes are regionally specialized, and likely to respond differently to CNS injury and in CNS disease. We previously showed that the calcium-binding protein S100A4 is exclusively expressed in white matter astrocytes and markedly up-regulated after injury. Furthermore, down-regulation of S100A4 in vitro significantly increases the migration capacity of white matter astrocytes, a property, which might influence their function in CNS tissue repair. Here, we performed a localized injury (scratch) in confluent cultures of white matter astrocytes, which strongly express S100A4, and in cultures of white matter astrocytes, in which S100A4 was down-regulated by transfection with short interference (si) S100A4 RNA. We found that S100A4-silenced astrocytes rapidly migrated into the injury gap, whereas S100A4-expressing astrocytes extended hypertrophied processes toward the gap, but without closing it. To explore the involvement of S100A4 in migration of astrocytes in vivo, we induced focal demyelination and transient glial cell elimination in the spinal cord white matter by ethidium bromide injection in S100A4 (-/-) and (+/+) mice. The results show that astrocyte migration into the demyelinated area is promoted in S100A4 (-/-) compared to (+/+) mice, in which a pronounced glial scar was formed. These data indicate that S100A4 reduces the migratory capacity of reactive white matter astrocytes in the injured CNS and is involved in glial scar formation after injury.

Expression of insulin-like growth factors in remyelination following ethidium bromide-induced demyelination in the mouse spinal cord

Insulin-like growth factors, IGF-I and IGF-II, play important roles in development and myelination in the CNS, but little is known about the response of IGF after demyelination. The present study investigated the expression of IGF and their cognitive receptors in the process of remyelination following ethidium bromide (EBr)-induced demyelination in the adult mouse spinal cord. The present results, in a quantitative real-time PCR, showed significant increases in the levels of the mRNA for both IGF-I and IGF-II during both the demyelination and remyelination stages. The levels of IGF-I receptor (IGF-IR) mRNA increased from 10 days to 4 weeks after the EBr injection. The levels of IGF-II receptor (IGF-IIR) mRNA decreased for 6 days and then increased 10 days after the EBr injection. In situ hybridization studies showed the cells expressing IGF-I mRNA to be mainly macrophage-like cells, while those expressing IGF-II mRNA were predominantly Schwann cell-like cells invading the demyelinating lesion. The immunoreactivity for the IGF-IR and IGF-IIR increased in various kinds of cells within and around the demyelinating lesions from 6 days to 4 weeks after the EBr injection. These results suggest that locally produced IGF could partly be involved in some mechanisms underlying remyelination processes following the EBr-induced demyelination in the mouse spinal cord.