Assessed and Emerging Biomarkers in Stroke and Training-Mediated Stroke Recovery: State of the Art

Could aerobic exercise applied before constraint-induced movement therapy change circulating molecular biomarkers in chronic post-stroke?

BACKGROUND

Integrating aerobic exercise (AE) into rehabilitation programs for post-stroke individuals could enhance motor recovery and cardiovascular health by increasing brain-derived neurotrophic factor (BDNF) and the myokine irisin. Chronic stroke survivors typically exhibit elevated matrix metalloproteinase-9 (MMP-9) activity, which is negatively correlated with steps and time in medium cadence, although the impact of AE on this biomarker remains unclear.

OBJECTIVE

To evaluate the effect of high-intensity AE training prior to modified constraint-induced movement therapy (mCIMT) on BDNF and irisin concentration, and on MMP-2 and MMP-9 activity in chronic post-stroke individuals and to associate these results with functional improvements.

METHODS

Nine participants received AE combined with mCIMT for two weeks, while the control group (n = 7) received mCIMT alone. Manual dexterity and functional capacity were assessed before and after the intervention. Serum samples were analyzed for BDNF, irisin, MMP-2 and MMP-9.

RESULTS

There were no significant main effects of assessment, group or interaction on molecular biomarkers. However, the AE group had a significant increase in MMP-9 activity post-intervention (p = .033; d = 0.67). For the Box and Block Test, there were significant main effects of assessment (F [1, 14] = 33.27, p = .000, ηp2 = 0.70) and group (F [1, 14] = 5.43, p = .035, ηp2 = .28). No correlations were found between biomarkers and clinical assessments.

CONCLUSION

AE prior to mCIMT did not influence circulating BDNF and irisin levels but did induce an acute rise in MMP-9 activity, suggesting potential effects on cardiovascular remodeling in this population.

Multiplexing Biosensor for the Detection of Extracellular Vesicles as Biomarkers of Tissue Damage and Recovery after Ischemic Stroke

The inflammatory, reparative and regenerative mechanisms activated in ischemic stroke patients immediately after the event cooperate in the response to injury, in the restoration of functions and in brain remodeling even weeks after the event and can be sustained by the rehabilitation treatment. Nonetheless, patients' response to treatments is difficult to predict because of the lack of specific measurable markers of recovery, which could be complementary to clinical scales in the evaluation of patients. Considering that Extracellular Vesicles (EVs) are carriers of multiple molecules involved in the response to stroke injury, in the present study, we have identified a panel of EV-associated molecules that (i) confirm the crucial involvement of EVs in the processes that follow ischemic stroke, (ii) could possibly profile ischemic stroke patients at the beginning of the rehabilitation program, (iii) could be used in predicting patients' response to treatment. By means of a multiplexing Surface Plasmon Resonance imaging biosensor, subacute ischemic stroke patients were proven to have increased expression of vascular endothelial growth factor receptor 2 (VEGFR2) and translocator protein (TSPO) on the surface of small EVs in blood. Besides, microglia EVs and endothelial EVs were shown to be significantly involved in the intercellular communications that occur more than 10 days after ischemic stroke, thus being potential tools for the profiling of patients in the subacute phase after ischemic stroke and in the prediction of their recovery.

Plasma bioactive adrenomedullin predicts outcome after acute stroke in early rehabilitation

An early and reliable prediction of outcomes after stroke is important for early effective stroke management and the adequate optimal planning of post-stroke rehabilitation and long-term care. Bioactive adrenomedullin (bio-ADM) is a 52-amino acid peptide that is an important peptide hormone in nervous system diseases. The aim of this study was to investigate the prognostic value of bio-ADM on outcomes after rehabilitation in patients with stroke. A total of 557 consecutive patients with a primary diagnosis of ischemic or hemorrhagic stroke (age 69.6-12.9 years, male 51.3%, ischemic stroke 72.5%), who were admitted to an in-patient early rehabilitation center directly after discharge from acute stroke hospital care, were enrolled in this prospective observational study. Plasma concentrations of bio-ADM were determined by using a chemiluminescence immunoassay (functional assay sensitivity 8 pg/ml). The early rehabilitation barthel index (ERBI) was used for the neurological assessment of the patients. The plasma bio-ADM level was analyzed in association with 6-month all-cause mortality as well as a composite outcome of all-cause mortality, unscheduled re-hospitalization, or transfer to a long-term care facility in a vegetative or minimally conscious state. Bio-ADM levels significantly increased in patients with ischemic stroke who died compared to surviving patients (40.4 pg/ml vs. 23.8 pg/ml, p < 0.001) or in those with composite outcomes compared to those with no events (36.9 pg/ml vs. 23.5 pg/ml, p < 0.001). Six-month all-cause mortality was higher in all patients with bio-ADM levels > 70 pg/ml (HR 4.83 [CI 2.28-10.2]). Patients with bio-ADM levels > 70 pg/ml also had higher rates of 6-month composite outcomes (HR 3.82 [CI 2.08-7.01]). Bio-ADM was an independent predictor of all-cause mortality and 6-month composite outcomes after adjusting for age, gender, and ERBI (adjusted OR 1.5; 95% CI 1.0-2.1; p = 0.047 and adjusted OR 1.48; 95% CI 1.1-2.0; p = 0.01, respectively). Bio-ADM may be a suitable novel biomarker to assess the outcomes of patients in rehabilitation after acute stroke. Elevated bio-ADM concentrations may have prognostic value for fatal and nonfatal events in patients with ischemic stroke during early rehabilitation.

The Effects of Four Weeks of Chiropractic Spinal Adjustments on Blood Biomarkers in Adults with Chronic Stroke: Secondary Outcomes of a Randomized Controlled Trial

Certain blood biomarkers are associated with neural protection and neural plasticity in healthy people and individuals with prior brain injury. To date, no studies have evaluated the effects chiropractic care on serum brain-derived neurotrophic factor (BDNF), insulin-like growth factor-II (IGF-II) and glial cell-derived neurotrophic factor (GDNF) in people with stroke. This manuscript reports pre-specified, exploratory, secondary outcomes from a previously completed parallel group randomized controlled trial. We evaluated differences between four weeks of chiropractic spinal adjustments combined with the usual physical therapy (chiro + PT) and sham chiropractic with physical therapy (sham + PT) on resting serum BDNF, IGF-II and GDNF in 63 adults with chronic stroke. Blood samples were assessed at baseline, four weeks (post-intervention), and eight weeks (follow-up). Data were analyzed using a linear multivariate mixed effects model. Within both groups there was a significant decrease in the mean log-concentration of BDNF and IGF-II at each follow-up, and significant increase log-concentration of GDNF at eight-weeks' follow-up. However, no significant between-group differences in any of the blood biomarkers at each time-point were found. Further research is required to explore which factors influence changes in serum BDNF, IGF-II and GDNF following chiropractic spinal adjustments and physical therapy.

Evaluation of anti-inflammatory diphenyldihaloketone EF24 in transient ischemic stroke model

OBJECTIVES

Revascularization is necessary in patients with ischemic stroke, however it does not address inflammation that contribute to reperfusion injury and the early growth of ischemic core. We investigated EF24, an anti-inflammatory agent, in a stroke model.

METHODS

Ischemic stroke was induced in mice by occluding middle cerebral artery for 1 h followed by reperfusion. EF24 was given either 10 min post-reperfusion (EF24_Post) or 10 min before occlusion (prophylactic, EF24_Pro). Survival, ipsilateral uptake of radioactive infarct marker ¹⁸F-fluoroglucaric acid (FGA), inflammatory cytokines, and tetrazolium chloride (TTC) staining were assessed.

RESULTS

Survival was increased in both EF24-treated groups compared to the stroke+vehicle group. Ipsilateral ¹⁸F-FGA uptake increased 2.6-fold in stroke+vehicle group compared to sham group (p < 0.05); the uptake in EF24-treated groups and sham group was not significantly different. TTC-staining also showed reduction in infarct size by EF24 treatment. Plasma IL-6, TNF-α, and corticosterone did not show significant changes among groups. However, ipsilateral tissue in stroke+vehicle mice showed increased IL-6 (>90-fold) and TNF-α (3-fold); the tissue IL-6 and TNF-α were significantly reduced in stroke+EF24_Pro and stroke+EF24_Post groups. ¹⁸F-FGA uptake significantly correlated with tissue IL-6 levels.

CONCLUSIONS

EF24 controls infarct growth and suppresses tissue inflammation in ischemic stroke, which can be monitored by ¹⁸F-FGA uptake.

State of the science in inflammation and stroke recovery: A systematic review

Stroke is a major cause of mortality worldwide, and survivors often have major life-changing disabilities. Annually in the United States, an estimated 795,000 people experience a new or recurrent stroke. All types of stroke involve an inflammatory reaction that follows the initial phase of incidence. However, investigations into any links between inflammatory markers and recovery processes in the context of post-stroke rehabilitation are lacking. In this systematic review, we searched the literature in PubMed, SCOPUS, and CINAHL databases to gather information on inflammatory biomarkers related to stroke and their association with rehabilitation outcomes, according to PRISMA guidelines. Eleven articles (n=1.773 stroke patients) were selected. Immune markers (interleukin 6 [IL-6], C-reactive protein, IL-1α, tumor necrosis factor α, soluble intercellular adhesion molecule 1) and functional status assessments (Modified Rankin Score, National Institutes of Health Stroke Scale, Functional Independence Measure, etc.) were the primary measures used in the reviewed studies. We found preliminary evidence for the evaluation of inflammatory biomarkers post-stroke, including the role of inflammation in functional recovery and the influence of rehabilitation on inflammation. This is the first systematic review of the topic. The review identifies several gaps in the literature that are critical for understanding the potential use of inflammatory markers to improve post-stroke outcomes.

Association of Proinflammatory Cytokine Levels with Stroke Severity, Infarct Size, and Muscle Strength in the Acute Phase of Stroke

OBJECTIVE

Patterns of cytokine levels and their association with stroke severity, infarct size, and muscle strength are obscure. We aimed to analyze the immune mediators linked to T helper (Th)1, Th2, Th17, and regulatory T cell patterns and their association with stroke severity, infarct size, and muscle strength.

MATERIALS AND METHODS

We included patients with acute stroke (n = 15) and healthy non-disabled individuals (n = 20) aged > 18 years. The dependent variables were stroke severity according to the National Institute of Health Stroke Scale (NIHSS), infarct size on computed tomography, handgrip strength by dynamometry, and global muscle strength according to the Medical Research Council (MRC) scale. The independent variables were the circulating cytokine levels. The cytokine levels were compared between the groups, and correlations between the clinical data were verified.

RESULTS

The stroke group had higher interleukin (IL)-6 (p < 0.0001) and IL-10 (p < 0.0001) levels, but lower tumor necrosis factor (TNF)-α (p = 0.036) levels than the control group. IL-10 and soluble tumor necrosis factor receptor (sTNF-RII) levels were correlated with each other (r = 0.533; p = 0.042) and infarct size (r = 0.653; p = 0.033 and r = 0.689; p = 0.018, respectively). MRC scores were positively and negatively correlated with handgrip strength of the affected side (r = 0.78; p = 0.001) and NIHSS scores (r = -0.87; p < 0.0001), respectively.

CONCLUSIONS

Plasma levels of some cytokines were associated with changes in the acute phase of stroke, and IL-10 and sTNF-RII levels are potential biomarkers of infarct size.

Extracellular Vesicles in Regeneration and Rehabilitation Recovery after Stroke

Patients that survive after a stroke event may present disabilities that can persist for a long time or permanently after it. If stroke prevention fails, the prompt and combinatorial intervention with pharmacological and rehabilitation therapy is pivotal for the optimal recovery of patients and the reduction of disabilities. In the present review, we summarize some key features of the complex events that occur in the brain during and after the stroke event, with a special focus on extracellular vesicles (EVs) and their role as both carriers of biomarkers and potential therapeutics. EVs have already demonstrated their ability to be used for diagnostic purposes for multiple brain disorders and could represent valuable tools to track the regenerative and inflammatory processes occurring in the injured brain after stroke. Last, but not least, the use of artificial or stem cell-derived EVs were proved to be effective in stimulating brain remodeling and ameliorating recovery after stroke. Still, effective biomarkers of recovery are needed to design robust trials for the validation of innovative therapeutic strategies, such as regenerative rehabilitation approaches.

PET Detection of Cerebral Necrosis Using an Infarct-Avid Agent 2-Deoxy-2-[18F]Fluoro-D-Glucaric Acid (FGA) in a Mouse Model of the Brain Stroke

PURPOSE

Ischemic stroke is a leading cause of disability worldwide. The volume of necrotic core in affected tissue plays a major role in selecting stroke patients for thrombolytic therapy or endovascular thrombectomy. In this study, we investigated a recently reported positron emission tomography (PET) agent 2-deoxy-2-[¹⁸F]fluoro-D-glucaric acid (FGA) to determine necrotic core in a model of transient middle cerebral artery occlusion (t-MCAO) in mice.

PROCEDURES

The radiopharmaceutical, FGA, was synthesized by controlled, rapid, and quantitative oxidation of clinical doses of 2-deoxy-2-[¹⁸F]fluoro-D-glucose (FDG) in a one-step reaction using a premade kit. Brain stroke was induced in the left cerebral hemisphere of CD-1 mice by occluding the middle cerebral artery for 1 h, and then allowing reperfusion by removing the occlusion. One day post-ictus, perfusion single-photon emission tomography (SPECT) was performed with ^99mTc-lableled hexamethylpropyleneamine oxime (HMPAO), followed by PET acquisition with FGA. Plasma and brain tissue homogenates were assayed for markers of inflammation and neurotrophins.

RESULTS

The kit-based synthesis was able to convert up to 2.2 GBq of FDG into FGA within 5 min. PET images showed 375 % more accumulation of FGA in the ipsilateral hemisphere than in the contralateral hemisphere. SPECT images showed that the ipsilateral HMPAO accumulation was reduced to 55 % of normal levels; there was a significant negative correlation between the ipsilateral accumulation of FGA and HMAPO (p < 0.05). FGA accumulation in stroke also correlated with IL-6 levels in the ipsilateral hemisphere. There was no change in IL-6 or TNFα in the plasma of stroke mice.

CONCLUSIONS

Accumulation of FGA correlated well with the perfusion defect and inflammatory injury. As a PET agent, FGA has potential to image infarcted core in the brain stroke injury with high sensitivity, resolution, and specificity.

Serum activity of matrix metalloproteinase-2 and -9 is increased in chronic post-stroke individuals: a cross-sectional exploratory study

BACKGROUND

High concentrations of matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9) are associated with inflammation early after stroke. In chronic stages, the elevation of some cytokines is related to the presence of co-morbid conditions in these individuals. In addition to this, some characteristics such as sensorimotor impairment, atrophy, and sedentary lifestyle predispose the system to an inflammatory response.

OBJECTIVE

To quantify MMP-2 and -9 serum activity in chronic post-stroke individuals and correlate it with variables of physical activity level, body composition, functional and walking capacity, and with inflammatory biomarkers. Additionally, gelatinase activity was characterized according to motor impairment.

METHODS

Fourteen patients with stroke onset >6 months and seven healthy individuals were enrolled in this study. The clinical assessment included: body composition, measure by bioelectrical impedance analyzer; Fugl-Meyer Motor Assessment Scale; six-minute and ten-meter walk tests, and physical activity level assessed by the StepWatch® Activity Monitor. Blood samples were collected from antecubital vein and serum MMP-2 and -9 activity was analyzed using gelatin Zymography, and the TNFα, IL-6, IL-1β, IL-10 biomarkers using ELISA kits.

RESULTS

Chronic post-stroke individuals presented an increased activity of MMP-2 and -9 compared to healthy individuals. Positive correlations with time and steps in low cadence and negative ones with medium cadence and peak activity index were observed. According to the motor impairment, the MMP-2 activity was increased in the mild-moderate group compared to the control group.

CONCLUSION

Increased gelatinases in chronic post-stroke individuals could describe an inflammation process related to the limited capacity of walking in high intensities.

Extracellular Vesicles in Acute Stroke Diagnostics

There is a large unmet need for fast and reliable diagnostics in several diseases. One such disease is stroke, where the efficacy of modern reperfusion therapies is highly time-dependent. Diagnosis of stroke and treatment initiation should be performed as soon as possible, and preferably before arrival at the stroke center. In recent years, several potential blood biomarkers for stroke have been evaluated, but without success. In this review, we will go into detail on the possibility of utilizing extracellular vesicles (EVs) released into the blood as novel biomarkers for stroke diagnostics. EVs are known to reflect the immediate state of the secreting cells and to be able to cross the blood–brain barrier, thus making them attractive as diagnostic biomarkers of brain diseases. Indeed, several studies have reported EV markers that enable differentiation between stroke patients and controls and, to a lesser extent, the ability to correctly classify the different stroke types. Most of the studies rely on the use of sophisticated and time-consuming methods to quantify specific subpopulations of the nanosized EVs. As these methods cannot be easily implemented in a rapid point of care (POC) test, technical developments followed by prospective clinical studies are needed.

Plasma cyclic glycine proline/IGF-1 ratio predicts clinical outcome and recovery in stroke patients

Objective

Many stroke patients make a partial recovery in function during the first 3 months, partially through promoting insulin‐like growth factor‐1 (IGF‐1) function. A prognostic biomarker that associates with IGF‐1 function may predict clinical outcome and recovery of stroke. This study evaluated plasma concentrations of IGF‐1, IGF binding protein (IGFBP)‐3 and cyclic‐glycine‐proline (cGP) and their associations with clinical outcome in stroke patients.

Methods

Thirty‐four patients were recruited within 3 days of stroke. Clinical assessments included the National Institutes of Health Stroke Scale (NIHSS) within 3 days (baseline), and at days 7 and 90; the modified Rankin Scale (mRS) and Fugl‐Meyer Upper‐Limb Assessment Scale (FM‐UL) at days 7 and 90. Plasma samples were collected from the patients at the baseline, days 7 and 90. Fifty age‐matched control participants with no history of stroke were also recruited and provided plasma samples. IGF‐1, IGFBP‐3, and cGP concentrations were analyzed using ELISA or HPLC‐MS.

Results

Baseline concentrations of IGFBP‐3, cGP, and cGP/IGF‐1 ratio were lower in stroke patients than the control group. The neurological scores of stroke patients were improved and plasma cGP and cGP/IGF‐1 ratio increased over time. Baseline cGP/IGF‐1 ratio was correlated with the NIHSS scores at day 90 and the changes in NIHSS scores from the baseline to 90 days.

Interpretation

Low cGP concentrations and cGP/IGF‐1 ratio in stroke patients suggest an impaired IGF‐1 function. The cGP/IGF‐1 ratio at admission maybe further developed as a prognostic biomarker for stroke recovery.

Cortico-Muscular Coherence Is Reduced Acutely Post-stroke and Increases Bilaterally During Motor Recovery: A Pilot Study

Motor recovery following stroke is believed to necessitate alteration in functional connectivity between cortex and muscle. Cortico-muscular coherence has been proposed as a potential biomarker for post-stroke motor deficits, enabling a quantification of recovery, as well as potentially indicating the regions of cortex involved in recovery of function. We recorded simultaneous EEG and EMG during wrist extension from healthy participants and patients following ischaemic stroke, evaluating function at three time points post-stroke. EEG–EMG coherence increased over time, as wrist mobility recovered clinically, and by the final evaluation, coherence was higher in the patient group than in the healthy controls. Moreover, the cortical distribution differed between the groups, with coherence involving larger and more bilaterally scattered areas of cortex in the patients than in the healthy participants. The findings suggest that EEG–EMG coherence has the potential to serve as a biomarker for motor recovery and to provide information about the cortical regions that should be targeted in rehabilitation therapies based on real-time EEG.

Alkaline phosphatase: a potential biomarker for stroke and implications for treatment

Stroke is the fifth leading cause of death in the U.S., with more than 100,000 deaths annually. There are a multitude of risks associated with stroke, including aging, cardiovascular disease, hypertension, Alzheimer's disease (AD), and immune suppression. One of the many challenges, which has so far proven to be unsuccessful, is the identification of a cost-effective diagnostic or prognostic biomarker for stroke. Alkaline phosphatase (AP), an enzyme first discovered in the 1920s, has been evaluated as a potential biomarker in many disorders, including many of the co-morbidities associated with stroke. This review will examine the basic biology of AP, and its most common isoenzyme, tissue nonspecific alkaline phosphatase (TNAP), with a specific focus on the central nervous system. It examines the preclinical and clinical evidence which supports a potential role for AP in stroke and suggests potential mechanism(s) of action for AP isoenzymes in stroke. Lastly, the review speculates on the clinical utility of AP isoenzymes as potential blood biomarkers for stroke or as AP-targeted treatments for stroke patients.

Aerobic Training Efficacy in Inflammation, Neurotrophins, and Function in Chronic Stroke Persons: A Randomized Controlled Trial Protocol

BACKGROUND

Neuroinflammation is an important part of stroke pathophysiology and has both detrimental and beneficial effects after stroke. Besides that the enhancement of neurotrophins seems to be related to improvements in stroke recovery. Evidences suggest that exercise plays a role in modulating anti-inflammatory and neurotrophic effects. However, little is known about its impact in stroke survivors, mainly in chronic stroke. The purpose of this study is to investigate the efficacy of moderate-intensity treadmill exercise in changing inflammatory mediators, interleukin-6 (IL-6), soluble tumor necrosis factor receptors I and II (sTNFRI, sTNFRII), interleukin-10 (IL-10), and brain-derived neurotrophic factor (BDNF) levels in chronic stroke patients. The secondary objective is to investigate the effects of training in improve mobility and exercise capacity.

METHODS

This is a randomized controlled trial. Chronic stroke patients will be randomized to an experimental or control group, and will receive group interventions three times per week, over 12 weeks. The experimental group will receive moderate-intensity (60%-80% of maximum heart rate reserve) treadmill exercise. Control group will perform walking training on the ground (<40% of maximum heart rate reserve). Primary outcomes include IL-6, sTNFRI, sTNFRII, IL-10, and BDNF levels. Secondary outcomes include mobility and exercise capacity. Outcomes will be measured at baseline, postintervention, and at the 4-week follow-up.

DISCUSSION

The findings of this trial have the potential to provide important insights regarding the effects of an aerobic physical program in the inflammatory process and in the neuronal plasticity in stroke persons and its impact on mobility and exercise capacity.

Prognostic utility of circulating nucleic acids in acute brain injuries

INTRODUCTION

Acute brain injuries represent major causes of morbidity and mortality worldwide. Nevertheless, therapeutic options are centered mainly on supportive care, and accurate prognosis prediction following traumatic brain injury (TBI) or stroke remains a challenge in clinical settings. Areas covered: Circulating DNA and RNA have shown potential as predictive molecules in acute brain injuries. In particular, plasma cell-free DNA (cfDNA) levels have been correlated to severity, mortality, and outcome after TBI and stroke. The real-time quantitative polymerase chain reaction (qPCR) is the most widely used technique for determination of cfDNA in brain injuries; however, to consider the use of cfDNA in emergency settings, a quicker and easier methodology for detection should be established. A recent study proposed detection of cfDNA applying a rapid fluorescent test that showed compatible results with qPCR. Expert commentary: As a promising perspective, detection of cfDNA levels using simple, rapid, and cheap methodology has potential to translate to clinic as a point-of-care marker, supporting the clinical decision-making in emergency care settings. Conversely, miRNA profiles may be used as signatures to determine the type and severity of injuries. Additionally, in the future, some miRNAs may constitute innovative neurorestorative therapies without the common hurdles associated with cell therapy.

FNDC5 expression in Purkinje neurons of adult male rats with acute spinal cord injury following treatment with methylprednisolone

Spinal cord injury (SCI) is a serious and complex medical condition that can happen to anyone. At present, therapy mainly focuses on rehabilitation and pharmacological treatment, such as methylprednisolone (MP). Supra-spinal changes in certain structures, such as the cerebellum, that receive many afferents from the spinal cord might be one reason for unsuccessful therapeutic outcomes. Recently, the expression of FNDC5 was reported in cerebellar Purkinje cells as a possible neuroprotective agent. In the present study, we considered the expression of FNDC5 in Purkinje cells following SCI with and without MP administration in adult rats with SCI. Thirty-five adult male rats were used in this study. The animals were randomly allocated into five groups, including SCI, spinal cord injury with methylprednisolone treatment (SCI + MP), operation sham, control, and operation sham with MP. Induction of SCI was achieved by using special clips to compress the spinal cord at a determined level. After a certain interval time, the animals underwent study for FNDC5 expression, apoptosis by using immunohistochemistry, Western blotting, and TUNEL and Nissl staining. Our results showed a significant decrease in the number of Purkinje cells following SCI. Therapy with MP inhibits apoptosis in irFNDC5 Purkinje cells and restores them. Expression of FNDC5 significantly increased in SCI and decreased following MP therapy. We also showed other cerebellar cells with FNDC5 immunoreactivity in the two other cerebellar layers that were firstly reported. Since irisin is known as a plasma product of FNDC5, we think it might be a plasma marker following therapeutic efforts for SCI; however, it needs further research. In addition, it is possible that changes in FNDC5 expression in Purkinje cells might be related to neurogenesis in the cerebellum with unknown mechanisms.

Influence of physical exercise on microRNAs in skeletal muscle regeneration, aging and diseases

Skeletal muscle is a dynamic tissue with remarkable plasticity and its growth and regeneration are highly organized, with the activation of specific transcription factors, proliferative pathways and cytokines. The decline of skeletal muscle tissue with age, is one of the most important causes of functional loss of independence in older adults. Maintaining skeletal muscle function throughout the lifespan is a prerequisite for good health and independent living.

Physical activity represents one of the most effective preventive agents for muscle decay in aging.

Several studies have underlined the importance of microRNAs (miRNAs) in the control of myogenesis and of skeletal muscle regeneration and function.

In this review, we reported an overview and recent advances about the role of miRNAs expressed in the skeletal muscle, miRNAs regulation by exercise in skeletal muscle, the consequences of different physical exercise training modalities in the skeletal muscle miRNA profile, their regulation under pathological conditions and the role of miRNAs in age-related muscle wasting.

Specific miRNAs appear to be involved in response to different types of exercise and therefore to play an important role in muscle fiber identity and myofiber gene expression in adults and elder population.

Understanding the roles and regulation of skeletal muscle miRNAs during muscle regeneration may result in new therapeutic approaches in aging or diseases with impaired muscle function or re-growth.