High intensity interval training protects the heart against acute myocardial infarction through SDF-1a, CXCR4 receptors and c-kit levels

Abstract

Background: One of the best and most effective applied and tolerable approaches for cardioprotecion is the regular exercise. In situation of exercise activity and even cardiac ischemic injury, the activity of the myocardial stem cells and their recruiting factors are changed so that contribute the adaptation and repairment of the myocardium. The aim of this study was to investigate the effect of myocardial preconditioning with high intensive interval training on SDF-1a myocardial levels, CXCR4 receptors and c-kit after acute myocardial infarction in male rats.  

Methods: 20 male Wistar rats (8 week old ,weight 234.8 ± 5.7 g) were randomly divided into 4 groups of control (C), training (T), myocardial infraction (MI) and training+ myocardial infraction (T+MI). The training groups performed two weeks of high intensity interval training in four sections. Each section included two or three days of practice sessions and two sessions each per a day. The number or intensity of the intervals increased in each section. SDF-1, CXCR4 and C-Kit proteins were measured by the Western blot method in the myocardial tissue and myocardial injury enzymes (CK, LDH, troponin T) were measured in serum.

Results: The results of this study showed that that SDF-1, CXCR4 and C-Kit had a significant increase after two weeks of high intensity interval training and myocardial infraction. Also, serum enzyme measurements showed a positive effect of exercise, so that in the myocardium injury enzymes significantly increased in the myocardial infarction group compared with the other three groups, training and training- myocardial infarction (P<0.001). As well as, there was a significant difference between the groups of training -myocardial infarction in all of the enzymes of the myocardium injury compared to the control and training groups.

Conclusions: Even short terms of high intensity interval training can increase the levels of proteins SDF1-a, CXCR4 and C-Kit in order to cardioprotection against myocardial injury through recruitment stem cells.

Background

Ischemic heart disease is caused by a change in coronary and myocardial arteries by myocardial oxygen deprivation in result decrease in blood flow to the myocardium [1]. Heart attack or acute myocardial infarction (AMI) is in fact the same ischemia caused by coronary artery atherosclerosis associated with arterial thrombosis, coronary embolism, spasm, and reduction in the diameter of the coronary arteries, leading to permanent and irreversible cell death in the part of the heart muscle [2]. Studies have shown that, following an acute myocardial infarction, inflammation occurs in the affected areas of the heart, and cytokines play a role in the induce of this inflammation [3]. In the among, a group of cytokines with local presence helps to reduce the inflammation process and prevent the injury development [3] and in this case, chemokines play an important role [4]. Part of this process, through the release of heart tissue cardiokines and chemotactic of stem cells, stimulates endogenous pathways in injured locations [5, 6]. More studies have shown that the stem cell recruitmenter factors (such as G-CSF, SDF, SCF and Flt3) are chemokines that recruitment stem cells from the bone marrow and move to the myocardial tissue. Among the recognized chemokines that are released from the myocyte into the bloodstream (Stromal Drive Cell Factor), the SDF of the CXC family has numerous isoforms that play a very important role in post-myocardial regeneration and the most important isoform is α-1 [7]. SDF-1α has a variety of functions, including proangiogenic, improved endothelial function, cell regeneration, and stimulating cell proliferation is antiapoptotic. In normal conditions, the level of this chemokine and the recruitment of the stem cells in the body is insignificant, but it has been observed that there is a upregulation immediately after myocardial infarction and reduces the myocytes injury and improves cardiac function by the movement of stem cells from the bone marrow [8]. Possible mechanisms of this incident can be due to myocardial tissue regeneration by the process of myogenesis and vasculogenesis (new myocyte), damaged tissue remodeling and anti-apoptotic signals and anti-fibrotic myositis, reducing the structural disorder of the myocardial after acute myocardial infarction, the setting up of paracrine and endocrine mechanisms, regeneration of injured myocytes, as a result, reduced infract area [9, 10, 11]. On the other hand, SDF indirectly protects the cells from apoptosis through several signal pathways, the most important of which is the AKT / PKB pathway, and directly affects the BAX / BCL2 ratio, which is the cell death index [12]. It can be seen from the evidence that increased SDF and other factors involved in the recruitment of stem cells and as a result the increase in stem cells can be used to cardio protection and regeneration the myocardial tissue in many ways [13, 14].

There is increasing evidence that the SDF / CXCR4 axis plays a key role in regulating and regeneration injurious myocytes [15, 16, 17, 18, 19]. In this regard, Tang et al (2009) reported that the axis of the SDF / CXCR4 plays an important role in the recruitment of endogenous and exogenous stem cells [20]. Also well known that SDF-1a / CXCR4 axis is directly involved in the movement of stem cells to the area of injury in various tissues [21, 22, 23]. It has been shown that the expression of both SDF-1a, CXCR4, increases following acute hypoxic conditions [24, 25]. In recent decades, many studies have been done on different types of stem cells that are involved in regeneration and production of new cardiac cells [25, 26]. Among them can mention stem cell CSC [3, 27]. CSC includes several types of cells, that most theme in the regeneration and repair of injures areas in the heart of the c-kit [28]. Human and animal studies have shown that c-kit cells are stimulated and activated under hypoxic conditions in response to chemotactic signals such as SDF and SCF to reduce fibrosis of the myocytes [29]. Several other studies have reported that CXCR4 expression and activity in response to the stress of hypoxia result to the proliferation and migration of endogenous cardiac stem cells (C-kit) and it has been shown that activity and expression of HIF-1a is the main factor in expression of CXCR4 and the suppression of HIF-1a expression reduces the expression of CXCR4 [30]. Also, the hypoxic conditions is led to threefold increase serum and tissue levels of SDF-1a [15, 16]. Studies have shown that stem cell factor (SCF) and its receptor play an important role in the migration of C-kit endogenous stem cells to infarcted area after myocardial infarction and concluded that the role of SCF in the accumulation of CSC (C-kit) stem cells is dependent on the expression of the C-kit receptor. It has also been shown that the expression of the C-kit receptor for the movement of exogenous C-kit cells to the injurious cardiac tissue after myocardial infarction is necessary [31]. Accordingly, the crosstalk between the signal of the axes mentioned by the chemokine SDF-1a / CXCR4 and the SCF / C-kit stem cell factor plays an important role in stem cell recruitment [32] and cardio protection through intracellular signaling pathways [33, 34, 35].

Epidemiologic evidence shows that there is a strong relationship between people who are training regularly and are saved from cardiac infarction [36]. Regular exercise seems to be one of the best and most effective practical and tolerable approaches to heart protection [37]. Studies in this field showed that in various physiological conditions such as exercise and altitudes-related ischemia, and also pathological conditions (such as diseases), the concentration of SDF and other stem factors such as CSF-G, SCF, C-KIT, SCa-1 are changed [38, 39]. As Jing lu and et al showed that one until two weeks of incremental training with suitable intensity after stroke ischemia, increased levels of SDF, CXCR4. They showed that the expression of SDF and its receptor CXCR4 following exercise training plays a key role in the proliferation and migration of brain stem cells [39]. Other study by Sen et al (2015) showed that following aerobic exercise training, CD34 cells increased by stimulating SDF-1a and its receptor, CXCR4, and the presence of this chemokine was necessity to move stem cells to injury and inflammatory area [40]. In this field, a study also showed that even one session high intensity exercise (HIE) above the lactate threshold was increased serum levels of FLT3, G-CSF, SDF-1a, CD34 in adult and immature adults [41]. And they concluded that the maximal and submaximal exercises increase the levels of this chemokines in circulation and tissue [42, 43].

However above reasons, although high intensity interval training is known to be a strong stimulant for the release of recruitmener chemokine of various stem cells from different tissues [44], No research has found to study that the effect of a short high intensity interval training on the stimulation and release of chemokines that recruitment stem cell factors endogenous with ischemic. Accordingly, the aim of this study was to investigate the effect of high intensity interval training on tissue level of SDF, receptor and C-Kit proteins in myocardial following acute myocardial infarction in male rats.

Methods

Animals And Experimental design

In this study, Twenty male wistar rats with a  weight of 234.8 + 5.7 grams (eight weeks old) were purchased from the Animal Science Laboratory of Pasteur Institute and After transfer to the Center for Experimental Studies, kept at a temperature of 22 ± 2 ºC,  relative humidity of 50-55% and a dark-light cycle of 12:12. Rats were randomly divided into four groups  of control (C: n = 5), high intensity interval training (T: n = 5), training with myocardial infracted (T+MI: n = 5) and myocardial infracted group (MI: n = 5). In addition, animals were freely available to drinking water and compressed foods for rats during the study. In order to create an accord with the environment, all interventions began at least two weeks after the animals were locate in the lab. 48 hours after the last training session and one week after induction of infarction, the rats were anesthetized with ketamine (100 mg / kg) and xylazine (10 mg / Kg). After confirmation of complete anesthesia, their cardiac tissue extraction and were frozen quickly in liquid nitrogen and stored at -80 ° C in the freezer. After the end of the study, the animals were delivered to the animal care center to be destroyed in accordance with the ethical principles of the animal ethics committee of the university of medical sciences.

All methods including anesthesia and sacrifice procedure were conducted in accordance with the guide for the care and use of laboratory animals, institutes for laboratory animal research, National Institutes of Health (NIH Publication No.85-23, revised 1996) and approved by the Animal Ethics Committee of University of Medical Sciences (28895-1302-1395 IR.IUM S.REC). 

Exercise Protocols

The reasons for the use of this training method in this study because of the beneficial effects of high intensity interval training on cardiovascular disease, angiogenic, mitochondrial biogenesis and extra enhance metabolic needs of the body's muscles, increase stress hormones, and active into signal that research various approve [41,45,46]. 

Before starting presses training, in order to familiarize with treadmills, exercise groups practiced 3 sessions at a speed of 20 m/min for 10 to 15 minutes (approximately 50% of VO2max) on treadmill [45,47,48]. After one day rest, the two-week protocol containing four parts, was performed as follows (table1).

The first section consisted three days of training, two sessions each day, and each session consisting of 4 ×2 min with the speed of 35-40 m/min (~85-95% of vo2max) and 3 × 2 min with slow speeds of 25 to 30 m /min (~60-70% vo2max) between two high interval training. The second part included two days of training, 4 ×2 min with 40 to 45 m / min (~95 -100% vo2max) and 3 × 2 min slow intervals with 28 to 32 m /min (~65-75% vo2max). The third part included three days of training, including 5 high intervals and 4 slow intervals with intensity of the second part. The fourth section consisted of two days of training, as in the third part, but with 6 high intensity intervals and 5 slow intensity intervals [47,49].

In order to ensure the physiological effect of training during two weeks, the functional test of maximum endurance performance capacity at the beginning and end of the training was measured (Fig. 1). The time to exhaust was determined by a mild shock. Whenever the rats contact the shock set at the end of the barrel twice in 30 seconds, or the reflection of the return and standing straight on the leg was seen as exhaustion [50]. The test protocol includes of gradual warming with intensity of 15 to 25 m / min for 5 minutes. Then, in the second stage, the speed and activity time, such as Figure 1, continued time to exhaustion [51].

Induction of Myocardial Ischemia

For induction of myocardial infarction, subcutaneous injection of Isoprenaline (150 mg/kg) solution in normal saline was performed for two consecutive days. The use of this substance in animal models, especially in rats, is one of the common ways to cause infarction [41,47]. 

Histological methods And Confirmation of Infarction

Blood enzymes creatine kinase (CK), lactate dehydrogenase (LDH), and troponin T were measured to confirm the injury of the heart tissue. Hematoxylin and Eosin (H&E) staining was also used to investigate the necrosis and Mason's trichrome staining was used to determine the fibrous tissue. After staining, samples were analyzed using an optical microscope of 40 X zoom.

Proteins measurement

Protein concentrations of SDF-1α, CXCR4 and c-kit were measured using the western blot method, so that 100 mg of left ventricular tissue was located in a RIPA buffer for 30 minutes. Then the ventricular tissue was lysed using a homogenizer. The solution was stored in ice for half an hour. And then for 20 minutes using a centrifuge set at temperature of 4 ° C and speed 12,000 rpm. The supernatant was separated and stored in a freezer at 80 ° C until it was used. Nano-Drop evaluations were used to determine the protein concentration. The western blot test was performed based on the determined protocol. In summary, the prepared samples were prepared with 10 ml Tris (pH 6.8), 12.5 ml Glycerol, 2.5 ml β-mercapto ethanol, 0.01 g Bromo phenol Blue, 25 ml SDS (10%)) are equally combined and boiled in a temperature of 100 ° C for 7 minutes. Then, the solution was exposed to SDS-page 12.5% and proteins were transferred to PVDF membrane. The concentration of these proteins was identified by specific antibodies to SDF-1α (England, biorbyt, orb227817), (England, biorbyt, orb10305) cxcr4 and c-kit (England, biorbyt, orb374707). Finally, the membrane was incubated with an ECL Western blotting system and exposed to X-ray film. Band density analysis was performed by image j software. Whereas β-actin is a component of proteins with stable expression in the cell. The antibody of this protein was used to remove the error of loading equal amounts of protein in the wells. 

Statistical Analysis

In the present study, the Shapiro-Wilk test was used to determine the normal distribution of data and one-way ANOVA and Tukey tests were used for data analysis at the level of 0.05. Statistical analysis was performed using SPSS software.

Results

The results of this study showed that two weeks high intensity interval training significantly increased (P=0.000) endurance capacity of male rats in the two training groups that indicates the physiological effect of this duration and the type of exercise training on the endurance capacity of the rats. The running distance in the control group at the beginning of the training was 735 meters and the time was 41.5 minutes, which after 2 weeks was 945 meters and it’s time to 48.95 minutes. Also, The running distance in the myocardial infraction group changed from  774 m to 976 m and its time ranged from 42.75 to 52.85min, but the running distance in the training group at the beginning of the training was 760 meters and the time was 41.86 minutes and after two weeks of high intensity interval training, the distance was 3400 meters and the time to 182.75 minutes and in the training+myocardial infraction group (T+MI) chanced from 723 to 3324 meters and time from 40.2 to 170.25 minutes (table 2).

The results of one-way analysis showed that there was a significant increase in LDH, CKMB, CK Total and troponin T factors after two weeks of high intensity interval training and myocardial infraction between the groups (P=0.000). Tukey's post hoc test showed that the difference between the myocardial infraction group and the other groups (C (P=0.000), T (P=0.000) and T+MI (P=0.000)). Also, this test showed that in all four factors, there was a difference between the training+myocardial infraction group (T+MI) with training and control groups. These results mean that myocardial infraction significantly increases LDH, CKMB and troponin T. There is also a significant difference in the LDH enzyme between the training group and the control group (p=0.042) (Fig. 2). 

Hematoxylin and Eosin (H&E) staining results (Fig. 3) and Mason’s trichrome staining (Fig. 4) was shown the amount of fibrosis and necrosis in the heart tissue and can confirm the protective effect of exercise training against infarction. pathological results showed that injection of isoprenaline in two consecutive days causes severe tissue injury to the heart. As shown in Figure 3, in the MI group, severe pathological changes were created, including edema, Neutrophil accumulation, separation of fibers, and collagen formation in the heart tissue.

Antibody SDF-1α was used for its expression in the cardiac tissue of four groups of rats. Analysis of Western Blot results using one way ANOVA showed that there is a significant difference between the mean of the four groups. The results showed that the SDF-1α protein concentration of the myocardial infraction group (MI) was statistically significant in comparison with the training group, the control group and the training group with myocardial infraction (T+MI, P=0.000) (Fig. 5A). Also, SDF-1α protein concentration in T+MI group was significant in comparison with the training group (P = 0.002) and control group (P = 0.000).

Also, C-Kit tissue protein concentration was studied in four groups using western blot technique. The result shows that the concentration of this protein in the myocardial infraction group (MI) was significantly higher than the T group, T+MI and control group (P = 0.000). As well as, the concentration of C-kit protein in the T group and T+MI group was significantly higher than the control group (P = 0.000) (Fig. 5B). 

The results of Western blot analysis with one-way ANOVA and Tukey's post hoc test showed that CXCR4 protein concentration after two weeks of high intensity interval training in the myocardial infraction group (MI) was significantly higher than the training group (P=0.000), training+myocardial infraction group (T+MI) (P=0.009) and control group (P=0.000). Moreover, the results showed that the concentration of this protein in the T+MI group was significantly increased compared to the control group (P=0.000) and the training group (P=0.017), and the expression of this protein in the training group was significantly increased compared to the control group (P=0.000) (Fig. 5C).

Protein beta-actin as a control has been studied and the results of actin expression in groups of T, T+MI, MI and C, are see in Fig. 5D.

Discussion

The results of present study showed significant increase in endurance capacity, duration and running distance of male Wistar rats that following two-weeks high intensity interval training, which indicated the physiological effects of selected exercises training on performance and physiological adaptations of rat [52].

The results showed that levels of c-kit receptor protein tissue were statistically significant increase in training (T), MI and T + MI groups compared with the control group. Studies have shown that stem cell factor (SCF) and its receptor C-kit play an important role in the migration of endogenous stem cells to infarct areas after MI. kuang et al (2008) showed that the expression of SCF / C-kit significantly increased immediately after MI in the rats. They concluded that the over expression of SCF and its receptor in the infarcted area was associated with the accumulation of stem cells [53]. And they also claimed that the presence and expression of SCF, which is a factor in the accumulation of stem cells, depends on the content of expression of the receptor of the C-kit. On the other hand, Chuan Hang et al (2011) in a study showed that the adult heart has a small number of cells expressing stem cell markers such as C-kit, SCa-1 and MDR-1 [54].

The results of this study showed that the expression of C-kit receptor expression after two weeks high intensity interval training with acute myocardial infarction was significantly increased compared to control group. Studies has shown that following exercises training, the stem cells recruitment of C-kit and also the expression of NKX2 /5 and GATA4 (the key factors transcription of the cardiac stem cells) is increased [55, 56]. In addition, exercise training activates the PI3K / AKT signal pathways in the myocardial infarcted area and beneficial effects are induced through recruitment of C-kit + cells by increasing the synthesis of DNA in the heart infarcted area (57). In this relation, Ellison and et al also showed that the exercise training increases the ratio of cardiac to body weight, volume of myocytes and salso the number of cardiac stem cells in the training group by 5 folds in the ventricular wall. They were also showed that exercise training Exercise in the first, second, and third weeks resulted in C-kit expression in the left ventricle of rat, but this increase was observed in the right ventricle in the third week [58]. Exercise training with controlled intensity increases the expression of growth factors, initiates the regeneration of myocytes, and then activates the differentiation of the C-Kit, which results in the production of new heart cells. This finding suggests that cardiac physiological adaptation depends on the intensity and duration of the exercise [58].

The results of this study showed that SDF-1a and its receptor CXCR4 concentration in three groups significantly increased with control group and also, the tissue concentration of these proteins in the T + MI group was significantly higher than that of the training group. The findings have shown that, during the ischemia and hypoxia, key family factors (HIFs) that directly activate and increase the growth factors (SCF, HGF, VEGF, PDGF), chemokines (SDF-1a) and cytokines [59, 60, 61]. The expression of SDF-1a is regulated through the HIF pathway in endothelial cells and its expression in ischemic tissue is proportional to the amount of oxygen depletion [59, 62]. Accordingly, the SDF / CXCR4 axis is associated with cardiac survival, new angiogenesis, and cardiac cardiac function after cardiac infarction [63]. Recent studies have shown that the SDF/CXCR4 signal axis plays role in reducing infarcted size and improving left ventricular function in ischemic injury-redundant models [64]. On the other hand, following the ischemia in tissue with the activation of the SDF-1a / CXCR4 signal axis, the migration of CPC / C-kit + stem cells to infarction area increases [65, 66]. In this relation, Tang et al found that hypoxia increased the expression of CXCR4 and HIF-1a increased CLK / C-kit + migration through SDF-1a [20]. It is necessary to express that CPC / C-kit + cells are endogenous stem cells in the adult heart that are responsible for the regeneration of cardiac myocyte in physiologic and pathological conditions [20]. Studies have shown that stem cell migration is enhanced by the pathways of SDF-1a / CXCR4 and SCF / C-kit, which plays its role by blocking the pathway of signal p38-MAPK (a factor in reducing the migration of stem cells) [54]. The research that done by Ding (2013), showed that crosstalk between the SDF-1α / CXCR4 and SCF / C-kit signaling pathways plays an important role in profibrotic by recruitment endogenous C-kit stem cells [32]. The researches also showed that the expression of the receptor of the C-kit induces MMP-9 activity, which is necessary for the proliferation and migration of the progressive C-kit stem cells to the cardiac after the MI [31]. On the other hand, TNF-α binding to the C-kit receptor is overexpressed by the C-kit receptor, which increases the regeneration of injuries cardiac cells [31].

Also, other signaling pathways are activated by axis SDF-1a / CXCR4, which results in cell survival and stem cell proliferation. So that, the expression of CXCR4 is PI3K / AKT phosphorylation mediator, which that results in upregulate vascular growth factor (VEGF) regulation [33]. AKT and ERK1 / 2 are another signal path that is activated by the SDF-1a/CXCR4 axis, which inactivates the BAD protein expression (associated with cell death) [34, 35]. It also increases the expression of cell protect and survival proteins such as BCL2, BCL-XL, Notch-1, β-catenin and NK-KB. The CAMP / PKA signal path is another path that is activated by the SDF-1a/CXCR4 axis, which is necessity for the migration of stem cells to injuries areas [67].

Research showed that tissue ischemia increased the expression of SDF-1, which activates the STST3 signal pathway, and improves cell growth and inhibits cell apoptosis [54]. STAT3 is a protective pathway in the heart that, by activating several downstream signal pathways, expresses BCL2, BCL-XL, HSP, and angiogenic factors and decreases the secretion of inflammatory cytokines [68].

Pathologic results the present study showed that subcutaneous injection of isopretonol in two continues days caused severe pathological changes such as edema, neutrophilic accumulation, tissue disruption and hemorrhage in rat’s cardiac tissue. It also significantly increases indexes injuries cardiac such as LDH, CK total, CKMB enzymes and troponin T enzyme compared to the control and training groups, which was consistent with the results of the study by Farvin et al (2010) and tofighi et al (2016) [69, 70]. On the other hand, the results of this study showed that cardiac injury factors in T + MI group were less than that in the MI group, which may be the result of the protective effect of exercise training against ischemic attacks and cardiac infarction. The results of this study were similar to the results of Lebo et al (2011) and Nuno et al (2012) [71, 72]. Several studies have reported that exercise training protects against cardiac MI in animal models Induces [73, 74, 75, 76, 77]. It seems to Regular training periods one of the best and most effective and tolerant approaches that cause cardiac protection [37]. Anatomical and physiological changes in the coronary arteries, head shock protein (HSPS), increased activity of cyclooxygenase-2 (COX-2), increased endoplasmic endothelial stress (ER), enhanced potassium function of ATP-dependent sarcolemma (sarcoKATP), increased levels of ATP-dependent potassium channels in mitochondria (mitoKATP), nitric oxide (NO), and increased the antioxidant capacity of the myocardium are among the cellular-molecular mechanisms involved in cardiac protection from cardiovascular injuries [76, 78]. In this field, this study showed that the increase in the chemokine SDF and its receptor, as well as the C-kit receptor, would result in cardiac protection and regeneration by high intensity interval training. In the present study and other studies, it has been shown that under normal conditions, the levels of SDF-1α and its receptor CXCR4 in the heart tissue is insignificant [9, 39], but in different physiological conditions such as intense training, hypoxia and ischemia, as well as pathological conditions (Such as acute myocardial infarction), the concentration of these factors changes [79, 80]. In a similar study, researchers showed that serum levels of chemokines such as SDF-1α and stem cells, increased after one-session endurance training, and they increased this as a result of increased levels of cytokines in the trained peoples [11, 81]. These results were similar to the results of the present study, which showed that the high intensity interval training of SDF-1α tissue concentration increased. It seems that exercise training through induce ischemia and low hypoxia in various tissues of the body, including the cardiac, increases the level of SDF-1α and other stem cell promoters, and this increase can recruitment the stem cell to the ischemic and hypoxia tissue [40]. In this field, various conclusions have been reported from the effect of exercise training on the levels and effects of chemokines by researchers, as Sen et al (2015) and Sarto et al (2007) showed that following the performance of various exercises training, the levels of SDF-1a increased significant [40, 79]. They report that the probable reasons for the significant increase in the SDF-1a / CXCR4 axis were in cardiac increased cortisol levels due to exercise stress, which plays a key role in the onset of the AKT / PKB signal cascade, which improves cardiac function, improves ejection fraction, left ventricular fractional shortening, increased left ventricular wall thickness and recruitment of stem cells [41, 81]. Another study by Mendes-Fereer et al (2008) found that acute activity exercise and long-term exercise training led to the release of catecholamine’s that increase the movement of the progressive hematopoietic stem cells and also the acute and exercise training of the receptor expression Beta-adrenergic α1,2 and β2 increased, via increasing the expression of MMP-9, which is essential for the migration of progressive hematopoietic stem cells [82], In addition, the release epinephrine by the exercise activity of induced expression the receptor of GSK3β, which cause increases the sensitivity of the chemotactic signaling pathways of SDF-1 and this of via induce remodeling of cytoskeletons [83].

Although there is a need for confirmation based on future studies, it can be reasoned that this is probably due to the fact that the tissue levels of SDF, CXCR4, and C-KIT in the training group and training- myocardial infraction group compared to the myocardial infraction group, despite of increasing the values was not statistically significant. The results of this study in tissue injuries showed that exercise training have a pathway of cardiac protection through induce multiple signal pathways and other unknown mechanisms that actually injuries resistance to acute ischemia and reduce the injuries caused by ischemia Acute and decreased cellular damage in the cardiac tissue. Therefore, the expected accumulation chemokine tissue levels in the training-myocardial infraction group may be statistically insignificant.

Conclusion

Despite the need for further research in this field, the general results of the present study suggest that high intensity interval training can be a type of preconditioning of the cardiac by increasing the levels of recruitment factors and the cardiac tissue regeneration factors itself and, in acute ischemia, reduce the amount of tissue injuries significantly. Therefore, it is suggested that people who do not have enough time to do exercise training, use high intensity interval training to take advantages of this training method.

Abbreviations

G-CSF: Granulocyte colony-stimulating factor; SDF: Stromal cell-derived factor; CXCR-4: chemokine receptor type 4; SCF: Stem cell factor; Flt3: FMS-like tyrosine kinase 3; CK: Creatin kinase; LDH: Lactate dehydrogenase;

Declarations

Ethics approval and consent to participate 

All animal experimental protocols mentioned in this study were carried out in compliance with the Guide for Care and Use of Laboratory Animals. All procedures were carried in accordance with the ARRIVE guidelines. The study was approved by the Animal Ethics Committee of Iran University of Medical Sciences (28895-1302-1395 IR.IUM S.REC). 

Consent for publication 

Not applicable

Availability of data and material 

The datasets used and/or analysed in the current study are available from the corresponding author upon reasonable request

Competing interests

The authors declare that they have no competing interests 

Funding

This work was supported in part by grants from the Iran University of Medical Sciences (28895-1302-1395 IR.IUM S.REC). The funding bodies were involved in providing primary materials for the data collection and were not involved in data analysis or interpretation and writing the manuscript. 

Authors ‘contributions

BM designed the experiments, collected and analyzed the data; RH, NF and RF controlled and supervised the stages of the study and revised the manuscript; GHR and RM helped to the training and laboratory tests; RM involved in writing the manuscript. All authors have read and approved the final version of the manuscript, and agree with the order of presentation of the authors.

Acknowledgements  

We appreciate all those who helped us in this research

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Tables

Table 1 

High intensity interval training protocol  

Table 2

The results of functional test before and after two weeks of HIIT in research groups.