BACKGROUND
multiple sclerosis  is an inflammatory demyelinating disease of the central nervous system , which can progress over decades.
the progressive failure of remyelination leads to the cumulative loss of axons, grey matter atrophy and prevalent neurodegeneration responsible for chronic disability and cognitive decline  <cit> .
there is a considerable difference in the way ms affects females and males, as has been highlighted by epidemiology studies and mri analyses  <cit> .
the way of gender-influence in ms is complex and still obscure.
from a pathogenic point of view, females tend to have stronger th1-mediated immune responses and are more prone to develop autoimmune diseases, including ms  <cit> .
however, gender might influence white matter establishment and maintenance of the mature structure of white tracts, thus affecting their repair capability.
a review of in vivo imaging studies suggests that gender-related differences in white matter in the human brain exist in healthy subjects  <cit>  and affect in particular age-related changes in precentral, cingulate, and anterior temporal white matter areas  <cit> .
as well as in the normal brain, white matter pathology seems also to differ in males and females in several neurological and psychiatric conditions.
for example, in schizophrenia there is a subtle and gender-dependent alteration in the forebrain commissures, and the neurotoxic effect of metamphetamine on frontal white matter seems to be less prominent in women than in men  <cit> .
sex differences in lesion size, neuronal cell loss, and mortality rates have been observed after ischemia and trauma  <cit> .
moreover, a gender effect in the progression of several neurodegenerative diseases has been noted.
epidemiological data point to women's proneness to alzheimer's disease  <cit> , and indicate that after traumatic brain injury  women show better recovery than men  <cit> .
apart from this clinical evidence, on which several gonadal steroids-oriented clinical trials have been based  <cit> , relatively few studies have explored possible molecular mechanisms involved in gender-related differences.
in this context, there has been much speculation concerning the gonadal hormone role in immune function and cytokines production during inflammation, myelination, and neurodegeneration/neuroprotection  <cit> , but direct evidence regarding gender-related differences in these and other critical molecular and cellular hallmarks of the diseases is still very scanty.
we are exploring possible molecular determinants for gender-dependent differences in inflammatory demyelinating diseases using experimental allergic encephalomyelitis  in rats as a disease model for ms. eae induced in dark agouti rats is th <dig> mediated, having a relapsing-remitting course, and comprises also persistent demyelination, remyelination, neuronal distress and cognitive defects  <cit> .
in this model, we have demonstrated by liquid chromatography-tandem mass spectrometry that the levels of neuroactive steroids display sex, regional and temporal differences in both control and eae, and these changes did not correlate to the plasma levels of gonadal hormones  <cit> .
in this paper data are presented regarding molecular markers for oligodendrocyte precursor cells, myelin proteins, neurotransmitters and neurotrophins in the course of eae.
attention was focused on the spinal cord as a white matter-rich area in which most of the tissue is occupied by heavily myelinated tracts that is severely affected by inflammation and demyelination, and on the cerebellum as a grey matter-rich area since ataxia is a common symptom in eae rats, and a cerebellar cortical atrophy has been described late in the disease in spite of poor inflammation and demyelination  <cit> .
RESULTS
animals and disease progression
the clinical profile of eae is reported in figure  <dig>  where neurological disability score  and body weight graphs  are shown.
animals develop clinical signs for eae starting from 7- <dig> days post-immunization , after which disease progressed rapidly until  <dig> dpi .
the first regression is not complete and at  <dig> dpi there is a relapse, which is not so severe as the acute phase.
the recovery phase is followed until  <dig> dpi, when a very slight disability still persists.
the statistical analysis by two-way anova indicates that the course of the disease is different between male and female rats .
the body weight curves show the physiological profile in male and female control rats, and the expected gain arrest in the acute phase, which is followed by a partial recovery .
histopathology was analysed at  <dig> dpi.
at this stage, a severe and diffuse inflammatory cellular infiltrate was observed in the spinal cord  in perivascular and intraparenchymal areas.
the astroglial reaction was also analysed by gfap-immunostaining  and demyelination by fluoromyelin histochemistry .
morphometric analysis of the investigated markers is reported in figure 2n-p. the semiquantitative evaluation of the inflammation score reveals a slight but significant difference between male and female rats, having the female animals a lower score .
the astroglial reaction observed in male and female rats during eae was stronger in female than in male rats .
demyelination, as analysed in the gracile fasciculus of the lumbar spinal cord, was no different in male and female rats.
at this stage, and as already reported in previously published paper  <cit>  very few cellular infiltrates were found in cerebellum and cerebral cortex .
myelin markers
in order to investigate possible gender effects on demyelination/remyelination during eae in dark-agouti rats, the expression level of myelin markers was analyzed in both male and female rats at the different phases of the eae, in spinal cord and cerebellum.
in particular, mrna expression level was analyzed for pdgfαr, which is a marker for the oligodendrocyte precursor cells  responsible for myelin repair in the mature cns  <cit>  and mbp, which is one of the most abundant among the myelin proteins  <cit> .
in the spinal cord, pdgfαr mrna expression in healthy males is around  <dig>  times higher than in healthy females , whereas the mbp mrna level is  <dig> times higher in males than in females  .
in both sexes, the expression of both genes was down-regulated in all phases of the disease  and a significant difference was observed between females and males .
pdgfαr mrna down-regulation is stronger in male than in female at  <dig> and  <dig> dpi.
mbp mrna expression level differs between male and female at  <dig> and  <dig> dpi.
the histochemical analysis of myelin during the acute phase of eae indicated that the decrease in myelin staining in the gracile fasciculus was comparable in both male and female rats .
to determine whether the sex-dependent difference in mbp mrna expression also had an impact on protein content, mbp protein levels were measured in the spinal cord of control healthy rats using western blot.
the  <dig> ,  <dig>  and  <dig>  isoforms were studied, and a representative western-blot experiment has been included in figure  <dig>  no differences between female and male rats were observed in any of the investigated isoforms .
a morphometric analysis of the myelin sheath in male and female rats was also performed by measuring the g-ratio of the lateral, dorsal and ventral funiculus of the lumbar spinal cord in confocal images of fluoromyelin staining.
no differences between male and female rats were observed .
in the cerebellum, no significant changes were observed in the expression of pdgfαr mrna between healthy male and female rats and during the course of eae .
on the contrary, mbp mrna expression level was down-regulated during eae in both females and males.
significant differences were observed in the expression of the mbp gene in eae animals  at  <dig> dpi between females and males, being lower in female than male rats .
gad, neurotrophins and related receptors
in order to investigate markers for neuronal distress/lesion, the expression level for mrnas encoding for gaba synthesis enzyme and neurotransmitter and neurotrophins was analyzed.
no gender effect was observed in the expression of mrna encoding for the enzymes gad <dig> and gad <dig> either in healthy or eae animals .
however, the expression of gad <dig> and gad <dig> mrna during eae was down-regulated in both male and female rats.
significant differences were observed at different phases of eae.
gad <dig> and gad  <dig> mrna levels displayed a recovery at  <dig> dpi.
the expression of bdnf, ngf neurotrophin receptors trka  and p <dig>  was also studied during eae in both sexes in the cerebellum.
no gender effect for any of the investigated mrnas was found in healthy animals .
bdnf mrna expression was not significantly changed during the course of eae  in both male and female rats.
on the contrary, there was a significant up-regulation of ngf mrna expression level in the acute, inflammatory phase of the disease in both male and female rats , which was partly attenuated, but not resolved, in the course of the disease in female rats and resolved already at  <dig> days in male rats.
a slight, but significant and stable up-regulation of the ngf low-affinity receptor p <dig> mrna expression was observed in both female and male rats .
an up-regulation of the ngf high-affinity receptor trka mrna expression level was also found in female and male .
discussion
gender bias in autoimmune diseases is a well-known and hitherto unexplained fact.
in particular, ms is more prevalent in females than in males, and this female predominance increases as time goes by.
gender appears to play a critical role also in the progression of ms, suggesting that not only immune reaction, but also remyelination, axonal pathology and neural damage might be gender-dependent  <cit> .
in all cases, the histopathological and molecular mechanisms underlying the inherent differences in male and female ms are still obscure  <cit> .
in the present study molecular markers for myelin and grey matter that are differentially regulated in male and female rats in the experimental model of the disease have been described.
two areas were investigated: the spinal cord, which is the area with extensive inflammation and demyelination, and the cerebellum, in view of the ataxia symptom in eae, where inflammatory cellular infiltrates are scare in this disease model  <cit> .
while the clinical profile of the disease differs between sexes being more severe in female than male rats, the inflammatory cellular infiltration in the spinal cord is lower in females, but produces a stronger astroglial reaction than in males.
moreover, disease-induced alteration of several markers is different between the two sexes.
in particular, a strong gender-dependent difference in mbp and pdgfar mrna expression level in the spinal cord of healthy animals was found, which correspond to a different regulation during the disease.
eae in male and female dark agouti rats
here we confirm that both male and female dark agouti rats are highly susceptible to eae  <cit> .
while the clinical score profile in the acute phase is similar in males and females, male rats show a more pronounced recovery than female rats.
in this eae model, a massive infiltration by inflammatory cells, and a massive demyelination were observed in the spinal cord, whereas small and localized lesions were spread over the main white tracts, including the cerebellar peduncoli, corpus callosum and optic nerve  <cit> .
the remyelination process starts quite early also in dark agouti rats, but it is not yet complete at  <dig> dpi  <cit> .
in spite of the fact that severity of inflammatory infiltrate in the spinal cord is lower in female compared to male rats, astroglial reaction is more pronounced in female than in male rats.
this could be related to humoral rather cellular immune reaction.
overall, the females of all the species used for ms models display stronger immune responses than males  <cit> .
this is attributed to cytokines production  <cit> .
for example, cytokine il- <dig> is implicated in gender differences in eae severity in c57bl/ <dig> mice, where the absence of the anti-inflammatory il- <dig> entails lower susceptibility to eae in females vs males or wt females with normal levels of il- <dig>  <cit> .
gender-dependent differences in white matter during health and inflammatory-demyelinating disease
when comparing the expression level of the genes included in the study in male vs female healthy rats, the most significant result was the 5-fold higher mbp and the  <dig> -fold higher pdgfαr expression in males than females in the spinal cord, but not in the cerebellum.
this difference is not present at protein level, and, more generally, no significant differences in myelin sheaths in the spinal cord were found between male and female rats.
this result might suggest that mbp synthesis could be regulated in a different way at post-transcriptional and translational levels in males and females.
in fact, mrna levels and protein levels do not always correlate  <cit>  and this might be due to the post-transcriptional mechanisms playing and/or to the different in vivo half life of proteins.
gonadal steroid and neurosteroid may elicit effects through non-genomic mechanisms via ers localized on the plasma membrane, and ligand-independent pathways to activate ers have been also described  <cit> .
moreover, the mechanisms controlling the rates of degradation/synthesis for a given mrna and protein are not homogeneous, even within proteins that have similar functions  <cit> .
technical limits of the methods for quantifying mrna and proteins should also be taken into account.
more generally, the issue of gender-related difference in the anatomy of white tracts is complex and controversial.
the gender-dependent difference in pdgfαr and mbp mrna in the spinal cord correlates with data from cerghet et al.
<cit>  in mice.
they found that the density of oligodendrocytes and the content of several myelin proteins in white tracts is higher in males than in females, whereas the lifespan of oligodendrocytes is shorter in females than in males, thus suggesting that myelin turnover is greater in females than in males.
it may thus be argued that males have a greater functional reserve than females, whereas females have a greater vulnerability related to higher myelin protein turnover.
we and others already described the variation of mbp protein content, such as different markers for opcs in male and female rats during eae  <cit> .
in this study we report that there is a gender-dependent difference in the regulation of pdgfαr and mbp during the experimental disease, involving both genes in the spinal cord, and mbp, only in the cerebellum.
this correlates with other reports describing differences in remyelination in old male and female rats  <cit>  and in cuprizone intoxication model   <cit> .
neurotrophins and neuronal markers in inflammatory-demyelinating diseases
the eae model in rodents  allows neuronal distress/damage to be investigated.
we already described how the expression level of the acetylcholine synthesis enzyme choline acetyltransferase mrna level was transiently reduced in motor neurons in the spinal cord  <cit>  and in cholinergic neuron of the basal forebrain  <cit>  during eae.
here investigation was focused on cerebellum, which is involved in motor symptoms in eae.
in spite of scant inflammation and demyelination, a grey matter atrophy  <cit>  and a purkinje cell loss  <cit>  has been described in the cerebellum.
as index of neuronal injury, we investigated the expression level of the mrnas encoding for the gaba synthesis enzyme γ-aminobutyric acid decarboxylase   <cit> .
a transient down-regulation of both gad <dig> and gad <dig> was observed in male and female eae rats, thus confirming that the acute phase of the disease is associated with reversible neuron distress.
due to the neurotrophins role as endogenous neuroprotectors, their expression levels were investigated during eae, focusing on ngf and bdnf.
previous results from our laboratory have described higher levels of ngf in certain brain areas, like the thalamus and cerebral cortex, but not the spinal cord, in eae compared to healthy rats, associated to a strong up-regulation of p75- and trka-like immunoreactivity  <cit> .
this up-regulation diminishes over time and a drop in ngf mrna expression level was reported in the cerebral cortex at  <dig> dpi  <cit> .
here we confirm the up-regulation of ngf and its high-affinity receptor trka mrna in the cerebellum in both male and female in the early, inflammatory phase of eae, while bdnf is down-regulated at the same times.
ngf, but also bdnf, modulate inflammation and immune cell function in many diseases  <cit> .
both the high and low affinity ngf receptors are widely expressed in the immune system, thus indicating a potential for responding to this neurotrophin through an autocrine mechanism  <cit> .
ngf increase during eae may possibly also result in increased neuroprotection  <cit> , working with the marmoset model, showed that ngf icv administration delayed the onset of clinical eae, and also prevented the full development of eae lesions.
ngf administration also influences eae development and progression in rats  <cit>  by reducing the severity of the disease compared to that in saline treated eae mice.
the low-affinity receptor p <dig> is also up-regulated.
notably, the up-regulation of p <dig> in purkinje neurons has been described in eae  <cit> .
the p <dig> up-regulation in eae could be related to the purkinje neurons death and cerebellar atrophy, since p <dig> can induce autophagy and death in these cells  <cit> .
since the original report describing the different content of ngf in the submaxillary gland in male and female mice  <cit> , many other reports have illustrated sexually dimorphic distribution of ngf in tissues and plasma of different animal species  <cit> .
the cerebellum and particularly the purkinje cells have been recognized as a major source for neurosteroid production  <cit> , and we reported that neurosteroids are differentially regulated in the cerebellum of control male and female rats, such as during eae  <cit> .
our mrna data indicate that there are no sex differences in the ngf and bdnf levels in cerebellum either in healthy and eae rats, thus confirming previous reports suggesting that neurotrophin levels do not correlate with estrogen levels in females or with estrogen or testosterone levels in males at this age  <cit> .
CONCLUSIONS
differences in vulnerability and disease evolution have already given rise to clinical trials for ms based on gonadal steroids.
with regard to animal models of inflammatory-demyelinating diseases, it has recently been reported that the combined administration of  <dig> beta-estradiol and progesterone prevents cuprizone-provoked demyelination of the corpus callosum in male mice  <cit> .
a similar effect of combined treatment was also found in mog -induced eae mice  <cit> .
however, rational future prospects regarding the use of sex steroids as adjuvant therapy in ms should be based on the identification of the pathological process, cell type, and molecular pathways positively affected by steroids with regard to disease onset and progression.
this study provides a description of the gender-dependent and disease-dependent regulation of markers for these different processes in a well-established animal model, suggesting that demyelination/remyelination might be a target for gender-dependent therapies.

 multiple sclerosis is an inflammatory demyelinating disease of the central nervous system, which can progress over decades. the progressive failure of remyelination leads to the cumulative loss of axons, grey matter atrophy and prevalent neurodegeneration responsible for chronic disability and cognitive decline. there is a considerable difference in the way ms affects females and males, as has been highlighted by epidemiology studies and mri analyses. the way of gender-influence in ms is complex and still obscure. from a pathogenic point of view, females tend to have stronger th1-mediated immune responses and are more prone to develop autoimmune diseases, including ms. however, gender might influence white matter establishment and maintenance of the mature structure of white tracts, thus affecting their repair capability. a review of in vivo imaging studies suggests that gender-related differences in white matter in the human brain exist in healthy subjects and affect in particular age-related changes in precentral, cingulate, and anterior temporal white matter areas. as well as in the normal brain, white matter pathology seems also to differ in males and females in several neurological and psychiatric conditions. for example, in schizophrenia there is a subtle and gender-dependent alteration in the forebrain commissures, and the neurotoxic effect of metamphetamine on frontal white matter seems to be less prominent in women than in men. sex differences in lesion size, neuronal cell loss, and mortality rates have been observed after ischemia and trauma. moreover, a gender effect in the progression of several neurodegenerative diseases has been noted. epidemiological data point to women's proneness to alzheimer's disease, and indicate that after traumatic brain injury women show better recovery than men. apart from this clinical evidence, on which several gonadal steroids-oriented clinical trials have been based, relatively few studies have explored possible molecular mechanisms involved in gender-related differences. in this context, there has been much speculation concerning the gonadal hormone role in immune function and cytokines production during inflammation, myelination, and neurodegeneration/neuroprotection, but direct evidence regarding gender-related differences in these and other critical molecular and cellular hallmarks of the diseases is still very scanty. we are exploring possible molecular determinants for gender-dependent differences in inflammatory demyelinating diseases using experimental allergic encephalomyelitis in rats as a disease model for ms. eae induced in dark agouti rats is th mediated, having a relapsing-remitting course, and comprises also persistent demyelination, remyelination, neuronal distress and cognitive defects. in this model, we have demonstrated by liquid chromatography-tandem mass spectrometry that the levels of neuroactive steroids display sex, regional and temporal differences in both control and eae, and these changes did not correlate to the plasma levels of gonadal hormones. in this paper data are presented regarding molecular markers for oligodendrocyte precursor cells, myelin proteins, neurotransmitters and neurotrophins in the course of eae. attention was focused on the spinal cord as a white matter-rich area in which most of the tissue is occupied by heavily myelinated tracts that is severely affected by inflammation and demyelination, and on the cerebellum as a grey matter-rich area since ataxia is a common symptom in eae rats, and a cerebellar cortical atrophy has been described late in the disease in spite of poor inflammation and demyelination.  animals and disease progression the clinical profile of eae is reported in figure where neurological disability score and body weight graphs are shown. animals develop clinical signs for eae starting from 7- days post-immunization, after which disease progressed rapidly until dpi. the first regression is not complete and at dpi there is a relapse, which is not so severe as the acute phase. the recovery phase is followed until dpi, when a very slight disability still persists. the statistical analysis by two-way anova indicates that the course of the disease is different between male and female rats. the body weight curves show the physiological profile in male and female control rats, and the expected gain arrest in the acute phase, which is followed by a partial recovery. histopathology was analysed at dpi. at this stage, a severe and diffuse inflammatory cellular infiltrate was observed in the spinal cord in perivascular and intraparenchymal areas. the astroglial reaction was also analysed by gfap-immunostaining and demyelination by fluoromyelin histochemistry. morphometric analysis of the investigated markers is reported in figure 2n-p. the semiquantitative evaluation of the inflammation score reveals a slight but significant difference between male and female rats, having the female animals a lower score. the astroglial reaction observed in male and female rats during eae was stronger in female than in male rats. demyelination, as analysed in the gracile fasciculus of the lumbar spinal cord, was no different in male and female rats. at this stage, and as already reported in previously published paper very few cellular infiltrates were found in cerebellum and cerebral cortex. myelin markers in order to investigate possible gender effects on demyelination/remyelination during eae in dark-agouti rats, the expression level of myelin markers was analyzed in both male and female rats at the different phases of the eae, in spinal cord and cerebellum. in particular, mrna expression level was analyzed for pdgfαr, which is a marker for the oligodendrocyte precursor cells responsible for myelin repair in the mature cns and mbp, which is one of the most abundant among the myelin proteins. in the spinal cord, pdgfαr mrna expression in healthy males is around times higher than in healthy females, whereas the mbp mrna level is times higher in males than in females. in both sexes, the expression of both genes was down-regulated in all phases of the disease and a significant difference was observed between females and males. pdgfαr mrna down-regulation is stronger in male than in female at and dpi. mbp mrna expression level differs between male and female at and dpi. the histochemical analysis of myelin during the acute phase of eae indicated that the decrease in myelin staining in the gracile fasciculus was comparable in both male and female rats. to determine whether the sex-dependent difference in mbp mrna expression also had an impact on protein content, mbp protein levels were measured in the spinal cord of control healthy rats using western blot. the, and isoforms were studied, and a representative western-blot experiment has been included in figure no differences between female and male rats were observed in any of the investigated isoforms. a morphometric analysis of the myelin sheath in male and female rats was also performed by measuring the g-ratio of the lateral, dorsal and ventral funiculus of the lumbar spinal cord in confocal images of fluoromyelin staining. no differences between male and female rats were observed. in the cerebellum, no significant changes were observed in the expression of pdgfαr mrna between healthy male and female rats and during the course of eae. on the contrary, mbp mrna expression level was down-regulated during eae in both females and males. significant differences were observed in the expression of the mbp gene in eae animals at dpi between females and males, being lower in female than male rats. gad, neurotrophins and related receptors in order to investigate markers for neuronal distress/lesion, the expression level for mrnas encoding for gaba synthesis enzyme and neurotransmitter and neurotrophins was analyzed. no gender effect was observed in the expression of mrna encoding for the enzymes gad and gad either in healthy or eae animals. however, the expression of gad and gad mrna during eae was down-regulated in both male and female rats. significant differences were observed at different phases of eae. gad and gad mrna levels displayed a recovery at dpi. the expression of bdnf, ngf neurotrophin receptors trka and p was also studied during eae in both sexes in the cerebellum. no gender effect for any of the investigated mrnas was found in healthy animals. bdnf mrna expression was not significantly changed during the course of eae in both male and female rats. on the contrary, there was a significant up-regulation of ngf mrna expression level in the acute, inflammatory phase of the disease in both male and female rats, which was partly attenuated, but not resolved, in the course of the disease in female rats and resolved already at days in male rats. a slight, but significant and stable up-regulation of the ngf low-affinity receptor p mrna expression was observed in both female and male rats. an up-regulation of the ngf high-affinity receptor trka mrna expression level was also found in female and male. discussion gender bias in autoimmune diseases is a well-known and hitherto unexplained fact. in particular, ms is more prevalent in females than in males, and this female predominance increases as time goes by. gender appears to play a critical role also in the progression of ms, suggesting that not only immune reaction, but also remyelination, axonal pathology and neural damage might be gender-dependent. in all cases, the histopathological and molecular mechanisms underlying the inherent differences in male and female ms are still obscure. in the present study molecular markers for myelin and grey matter that are differentially regulated in male and female rats in the experimental model of the disease have been described. two areas were investigated: the spinal cord, which is the area with extensive inflammation and demyelination, and the cerebellum, in view of the ataxia symptom in eae, where inflammatory cellular infiltrates are scare in this disease model. while the clinical profile of the disease differs between sexes being more severe in female than male rats, the inflammatory cellular infiltration in the spinal cord is lower in females, but produces a stronger astroglial reaction than in males. moreover, disease-induced alteration of several markers is different between the two sexes. in particular, a strong gender-dependent difference in mbp and pdgfar mrna expression level in the spinal cord of healthy animals was found, which correspond to a different regulation during the disease. eae in male and female dark agouti rats here we confirm that both male and female dark agouti rats are highly susceptible to eae. while the clinical score profile in the acute phase is similar in males and females, male rats show a more pronounced recovery than female rats. in this eae model, a massive infiltration by inflammatory cells, and a massive demyelination were observed in the spinal cord, whereas small and localized lesions were spread over the main white tracts, including the cerebellar peduncoli, corpus callosum and optic nerve. the remyelination process starts quite early also in dark agouti rats, but it is not yet complete at dpi. in spite of the fact that severity of inflammatory infiltrate in the spinal cord is lower in female compared to male rats, astroglial reaction is more pronounced in female than in male rats. this could be related to humoral rather cellular immune reaction. overall, the females of all the species used for ms models display stronger immune responses than males. this is attributed to cytokines production. for example, cytokine il- is implicated in gender differences in eae severity in c57bl/ mice, where the absence of the anti-inflammatory il- entails lower susceptibility to eae in females vs males or wt females with normal levels of il-. gender-dependent differences in white matter during health and inflammatory-demyelinating disease when comparing the expression level of the genes included in the study in male vs female healthy rats, the most significant result was the 5-fold higher mbp and the -fold higher pdgfαr expression in males than females in the spinal cord, but not in the cerebellum. this difference is not present at protein level, and, more generally, no significant differences in myelin sheaths in the spinal cord were found between male and female rats. this result might suggest that mbp synthesis could be regulated in a different way at post-transcriptional and translational levels in males and females. in fact, mrna levels and protein levels do not always correlate and this might be due to the post-transcriptional mechanisms playing and/or to the different in vivo half life of proteins. gonadal steroid and neurosteroid may elicit effects through non-genomic mechanisms via ers localized on the plasma membrane, and ligand-independent pathways to activate ers have been also described. moreover, the mechanisms controlling the rates of degradation/synthesis for a given mrna and protein are not homogeneous, even within proteins that have similar functions. technical limits of the methods for quantifying mrna and proteins should also be taken into account. more generally, the issue of gender-related difference in the anatomy of white tracts is complex and controversial. the gender-dependent difference in pdgfαr and mbp mrna in the spinal cord correlates with data from cerghet et al. in mice. they found that the density of oligodendrocytes and the content of several myelin proteins in white tracts is higher in males than in females, whereas the lifespan of oligodendrocytes is shorter in females than in males, thus suggesting that myelin turnover is greater in females than in males. it may thus be argued that males have a greater functional reserve than females, whereas females have a greater vulnerability related to higher myelin protein turnover. we and others already described the variation of mbp protein content, such as different markers for opcs in male and female rats during eae. in this study we report that there is a gender-dependent difference in the regulation of pdgfαr and mbp during the experimental disease, involving both genes in the spinal cord, and mbp, only in the cerebellum. this correlates with other reports describing differences in remyelination in old male and female rats and in cuprizone intoxication model. neurotrophins and neuronal markers in inflammatory-demyelinating diseases the eae model in rodents allows neuronal distress/damage to be investigated. we already described how the expression level of the acetylcholine synthesis enzyme choline acetyltransferase mrna level was transiently reduced in motor neurons in the spinal cord and in cholinergic neuron of the basal forebrain during eae. here investigation was focused on cerebellum, which is involved in motor symptoms in eae. in spite of scant inflammation and demyelination, a grey matter atrophy and a purkinje cell loss has been described in the cerebellum. as index of neuronal injury, we investigated the expression level of the mrnas encoding for the gaba synthesis enzyme γ-aminobutyric acid decarboxylase. a transient down-regulation of both gad and gad was observed in male and female eae rats, thus confirming that the acute phase of the disease is associated with reversible neuron distress. due to the neurotrophins role as endogenous neuroprotectors, their expression levels were investigated during eae, focusing on ngf and bdnf. previous results from our laboratory have described higher levels of ngf in certain brain areas, like the thalamus and cerebral cortex, but not the spinal cord, in eae compared to healthy rats, associated to a strong up-regulation of p75- and trka-like immunoreactivity. this up-regulation diminishes over time and a drop in ngf mrna expression level was reported in the cerebral cortex at dpi. here we confirm the up-regulation of ngf and its high-affinity receptor trka mrna in the cerebellum in both male and female in the early, inflammatory phase of eae, while bdnf is down-regulated at the same times. ngf, but also bdnf, modulate inflammation and immune cell function in many diseases. both the high and low affinity ngf receptors are widely expressed in the immune system, thus indicating a potential for responding to this neurotrophin through an autocrine mechanism. ngf increase during eae may possibly also result in increased neuroprotection, working with the marmoset model, showed that ngf icv administration delayed the onset of clinical eae, and also prevented the full development of eae lesions. ngf administration also influences eae development and progression in rats by reducing the severity of the disease compared to that in saline treated eae mice. the low-affinity receptor p is also up-regulated. notably, the up-regulation of p in purkinje neurons has been described in eae. the p up-regulation in eae could be related to the purkinje neurons death and cerebellar atrophy, since p can induce autophagy and death in these cells. since the original report describing the different content of ngf in the submaxillary gland in male and female mice, many other reports have illustrated sexually dimorphic distribution of ngf in tissues and plasma of different animal species. the cerebellum and particularly the purkinje cells have been recognized as a major source for neurosteroid production, and we reported that neurosteroids are differentially regulated in the cerebellum of control male and female rats, such as during eae. our mrna data indicate that there are no sex differences in the ngf and bdnf levels in cerebellum either in healthy and eae rats, thus confirming previous reports suggesting that neurotrophin levels do not correlate with estrogen levels in females or with estrogen or testosterone levels in males at this age.  differences in vulnerability and disease evolution have already given rise to clinical trials for ms based on gonadal steroids. with regard to animal models of inflammatory-demyelinating diseases, it has recently been reported that the combined administration of beta-estradiol and progesterone prevents cuprizone-provoked demyelination of the corpus callosum in male mice. a similar effect of combined treatment was also found in mog -induced eae mice. however, rational future prospects regarding the use of sex steroids as adjuvant therapy in ms should be based on the identification of the pathological process, cell type, and molecular pathways positively affected by steroids with regard to disease onset and progression. this study provides a description of the gender-dependent and disease-dependent regulation of markers for these different processes in a well-established animal model, suggesting that demyelination/remyelination might be a target for gender-dependent therapies. 
 a strong gender-dependent difference in myelin and myelin precursor marker mrna expression levels is observed in control animals in the spinal cord, but not in the cerebellum. this is the only gender-dependent difference in the expression level of the indicated markers in healthy animals; both pdgfαr and mbp mrnas in the spinal cord and mbp in the cerebellum are down-regulated during eae in gender-dependent manner; in the cerebellum, the expression profile of neuron-associated markers is characterized by a substantial down-regulation during the inflammatory phase of the disease, which does not differ between male and female rats; there is an up-regulation of ngf, trka and p mrna expression in the early phases of the disease, which is not different between male and female. in spite of clinical evidence, relatively few studies have explored molecular mechanisms possibly involved in gender-related differences. tissues were sampled during acute, relapse/remission and chronic phases and results were analysed by two-way anova. spinal cord and cerebellum, which are respectively severely and mildly affected by inflammation and demyelination. experimental allergic encephalomyelitisgender-relatedratspinal cordcerebellumneurotrophins and related receptors the present study describes possible cellular- and molecular-involved markers which are differentially regulated in male and female rats and result in gender-dependent eae evolution and progression.
 multiple sclerosis varies considerably in its incidence and progression in females and males. in spite of clinical evidence, relatively few studies have explored molecular mechanisms possibly involved in gender-related differences. the present study describes possible cellular- and molecular-involved markers which are differentially regulated in male and female rats and result in gender-dependent eae evolution and progression. attention was focused on markers of myelination and neuronal distress and/or damage, in two cns areas, i.e. spinal cord and cerebellum, which are respectively severely and mildly affected by inflammation and demyelination. tissues were sampled during acute, relapse/remission and chronic phases and results were analysed by two-way anova.  a strong gender-dependent difference in myelin and myelin precursor marker mrna expression levels is observed in control animals in the spinal cord, but not in the cerebellum. this is the only gender-dependent difference in the expression level of the indicated markers in healthy animals; both pdgfαr and mbp mrnas in the spinal cord and mbp in the cerebellum are down-regulated during eae in gender-dependent manner; in the cerebellum, the expression profile of neuron-associated markers is characterized by a substantial down-regulation during the inflammatory phase of the disease, which does not differ between male and female rats; there is an up-regulation of ngf, trka and p mrna expression in the early phases of the disease, which is not different between male and female.  it is reported herein that the regulation of markers involved in demyelination and neuroprotection processes occurring during eae, a well-established ms animal model, is gender- and time-dependent. these findings might contribute to gender- and phase disease-based therapy strategies. experimental allergic encephalomyelitisgender-relatedratspinal cordcerebellumneurotrophins and related receptors 