**6. Stem cell therapeutics; exosomes as biomarkers in cardiovascular diseases**

The intercellular communication between cardiac, vascular, SCs, and progenitor cells with differentiated cardiovascular cells is a complex process, with a diversity of mechanisms in cardiovascular disease and therapeutics. The EVs are produced through different pathways and are released and absorbed by most cells including cardiac, vascular, and progenitor stem cells [58].

or ethanol consumption increase the permeability of the exosomes, and different inducers of exosomes modify the content of the exosomal protein. The production of reactive oxygen species (ROS) is an underlying mechanism of increased production of exosomes and ethanol at "physiological" concentrations would trigger the release of exosomes. This work, as determined by Western blot analysis and mass spectrometry, mentions that exosomes retain their protein load in different physiological/pathological conditions; the protein content of the exosomes' cardiac etiologies differed from other types of exosomes due to their content of cytosolic, sarcomeric, and mitochondrial proteins. Ethanol did not affect the stability of the exosomes but increased the production of exosomes in cardiac myocytes; exosomes derived from ethanol and hypoxia/reoxygenation had a different protein content. Finally, inhibition

Therapeutic Strategies of Secretome of Mesenchymal Stem Cell

http://dx.doi.org/10.5772/intechopen.78092

197

Through circulating blood, circulating exosomes can reach distant tissues, allow direct communication with target cells, and regulate intracellular signals. Circulating exosomes and their exosomal charges participate in the hypertrophy of cardiomyocytes, apoptosis, and angiogenesis. Circulating exosomes enriched with various types of biological molecules can be modified in number and in loads of exosomes in cardiac lesions, such as MI, reperfusion injury, myocardial ischemia, atherosclerosis, hypertension, and cardiomyopathy due to sepsis, and can influence the function of the cardiomyocytes and contribute to the pathogenesis of CVD. A therapeutic strategy based on exosomes can be used to decrease myocardial injury

The CD34+ cells are a structural component in the formation of neovasculature in ischemic tissue, and secrete paracrine factors that stimulate the formation of new vessels, an element of proangiogenic paracrine activity associated with CD34+ cells secreted by exosomes, with a potent angiogenic paracrine activity both *in vitro* and *in vivo*. Exosomes stimulate mechanisms mediated by genetic receptors by transferring proteins, RNA, or microRNA directly to the

All types of cardiac cells are able to secrete ExMVs, which are captured by the recipient cells and can alter gene expression or activate cascades of intracellular signals. A possible therapeutic intervention to reduce the ischemia/reperfusion injury (I/R) is the pre or post-conditioning, which allows the activation of the salvage recovery pathway by reperfusion salvage kinase (RISK), where transcription factors such as factor 1α-induced hypoxia (HIF-1α), mediators such as heat shock protein 70 kDa (Hsp70) and inducible nitric oxide synthase (iNOS), demonstrated in an in vitro preconditioning model, which does not influence the secretion of EV and its morphology, but it has an effect on EV size and particularly on its charge. EVs derived from fibroblasts enhanced cell migration and the effect was improved by means of in vitro preconditioning. An experimental model of *in vitro* preconditioning of cardiac cells concluded that it does not influence the concentration of ExMVs, but regulates their load and affects

In conclusion, cardiac cells, such as cardiomyocytes, endothelial cells, and fibroblasts, release exosomes that modulate cellular functions. The exosomes released by CPCs are cardioprotective and improve cardiac function after MI, compared to that achieved by progenitor cells,

and they have antiapoptotic, proangiogenic functions.

of ROS reduced the production of exosomes [66].

and induce cardiac regeneration [67].

cytoplasm of target cells [68].

migration [69].

The conventional treatment in obstructive coronary disease is percutaneous coronary revascularization, angioplasty, stent placement, or coronary revascularization graft. In patients where there was no improvement or these treatments were not indicated, it is necessary to limit the damage produced by MI, to restore blood flow, and supply blood to the ischemic region. Microcirculation is a therapeutic target for the treatment of ischemic disease. Several preclinical studies show that CD34+ cells can stimulate neovascularization in ischemic tissue by increasing capillary circulation and improving acute and chronic myocardial ischemia [59]. A double-blind study showed lower rates of amputation in patients with critical ischemia of the lower limb with the administration of CD34+ cells [60]. Other studies mention that transplantation of CD34+ cells into ischemic myocardium after MI is better than neovascularization with mononuclear cells [61].

Cardiovascular diseases (CVD) have a high prevalence, morbidity, and mortality. The identification of biomarkers with high sensitivity and specificity can evaluate the prognosis of CVD, optimize personalized treatment, and reduce mortality. Biomarkers based on exosomes may reflect the stage and progression of coronary artery obstruction, heart failure, cerebrovascular accidents, arterial hypertension, cardiac arrhythmia, cardiomyopathy, valvular heart disease, and pulmonary arterial hypertension. On the other hand, exosomes as immunomodulators can be used in cardiac ischemia, pulmonary hypertension and many other diseases, including cancer, and also be used as a biomarker of the disease [62, 63]. Some exosomes can inhibit cell apoptosis and increase cell proliferation, contain specific surface proteins and the like, such as CD9, CD63, CD81, and proteins can transfect cardiomyocytes, endothelial cells, SC fibroblasts, and smooth muscle cells, and induce beneficial cellular changes. The release of exosomes from the cell is mainly regulated by Rab GTPase (Rab27a/b and Rab35). After a MI, the exosomes work in local and systemic microcommunications, in the exosomal transport of miRNA, and in the contribution of signals for cardiac repair, the myocardium can secrete exosomes, especially those that emerge in the border area of MI, so control of the quality and quantity of exosomes can serve as biomarkers in the diagnosis and prognosis of MI and as a new therapeutic objective to regulate cardiac remodeling [64].

The EVs secreted by the cardiac progenitor cells (CPC) can improve the cardiac function after the lesion by the content of exosomes with angiogenic factors that generate the ischemic tissue repair and are cardioprotective agents; the exosomes are the active components of the CD34+ of the BM. Experimentally, exosomes secreted by MSCs and CPCs have been shown to decrease tissue damage and facilitate ventricular remodeling in animal models of myocardial ischemia and reperfusion injury. The EVs are the active paracrine component of the CPCs [65].

In a study of stability, the exosomes of adult cardiac myocytes were shown to release heat shock protein (HSP) 60 in exosomes. When this protein is not in the exosomes, apoptosis is generated through the activation of the Toll-like receptor 4 and the release of Hsp60 would damage the surrounding cardiac myocytes. On the other hand, fever and a change in the pH or ethanol consumption increase the permeability of the exosomes, and different inducers of exosomes modify the content of the exosomal protein. The production of reactive oxygen species (ROS) is an underlying mechanism of increased production of exosomes and ethanol at "physiological" concentrations would trigger the release of exosomes. This work, as determined by Western blot analysis and mass spectrometry, mentions that exosomes retain their protein load in different physiological/pathological conditions; the protein content of the exosomes' cardiac etiologies differed from other types of exosomes due to their content of cytosolic, sarcomeric, and mitochondrial proteins. Ethanol did not affect the stability of the exosomes but increased the production of exosomes in cardiac myocytes; exosomes derived from ethanol and hypoxia/reoxygenation had a different protein content. Finally, inhibition of ROS reduced the production of exosomes [66].

cardiovascular disease and therapeutics. The EVs are produced through different pathways and are released and absorbed by most cells including cardiac, vascular, and progenitor stem

The conventional treatment in obstructive coronary disease is percutaneous coronary revascularization, angioplasty, stent placement, or coronary revascularization graft. In patients where there was no improvement or these treatments were not indicated, it is necessary to limit the damage produced by MI, to restore blood flow, and supply blood to the ischemic region. Microcirculation is a therapeutic target for the treatment of ischemic disease. Several preclinical studies show that CD34+ cells can stimulate neovascularization in ischemic tissue by increasing capillary circulation and improving acute and chronic myocardial ischemia [59]. A double-blind study showed lower rates of amputation in patients with critical ischemia of the lower limb with the administration of CD34+ cells [60]. Other studies mention that transplantation of CD34+ cells into ischemic myocardium after MI is better than neovascularization

Cardiovascular diseases (CVD) have a high prevalence, morbidity, and mortality. The identification of biomarkers with high sensitivity and specificity can evaluate the prognosis of CVD, optimize personalized treatment, and reduce mortality. Biomarkers based on exosomes may reflect the stage and progression of coronary artery obstruction, heart failure, cerebrovascular accidents, arterial hypertension, cardiac arrhythmia, cardiomyopathy, valvular heart disease, and pulmonary arterial hypertension. On the other hand, exosomes as immunomodulators can be used in cardiac ischemia, pulmonary hypertension and many other diseases, including cancer, and also be used as a biomarker of the disease [62, 63]. Some exosomes can inhibit cell apoptosis and increase cell proliferation, contain specific surface proteins and the like, such as CD9, CD63, CD81, and proteins can transfect cardiomyocytes, endothelial cells, SC fibroblasts, and smooth muscle cells, and induce beneficial cellular changes. The release of exosomes from the cell is mainly regulated by Rab GTPase (Rab27a/b and Rab35). After a MI, the exosomes work in local and systemic microcommunications, in the exosomal transport of miRNA, and in the contribution of signals for cardiac repair, the myocardium can secrete exosomes, especially those that emerge in the border area of MI, so control of the quality and quantity of exosomes can serve as biomarkers in the diagnosis and prognosis of MI and as a

The EVs secreted by the cardiac progenitor cells (CPC) can improve the cardiac function after the lesion by the content of exosomes with angiogenic factors that generate the ischemic tissue repair and are cardioprotective agents; the exosomes are the active components of the CD34+ of the BM. Experimentally, exosomes secreted by MSCs and CPCs have been shown to decrease tissue damage and facilitate ventricular remodeling in animal models of myocardial ischemia and reperfusion injury. The EVs are the active paracrine component of

In a study of stability, the exosomes of adult cardiac myocytes were shown to release heat shock protein (HSP) 60 in exosomes. When this protein is not in the exosomes, apoptosis is generated through the activation of the Toll-like receptor 4 and the release of Hsp60 would damage the surrounding cardiac myocytes. On the other hand, fever and a change in the pH

new therapeutic objective to regulate cardiac remodeling [64].

cells [58].

with mononuclear cells [61].

196 Stromal Cells - Structure, Function, and Therapeutic Implications

the CPCs [65].

Through circulating blood, circulating exosomes can reach distant tissues, allow direct communication with target cells, and regulate intracellular signals. Circulating exosomes and their exosomal charges participate in the hypertrophy of cardiomyocytes, apoptosis, and angiogenesis. Circulating exosomes enriched with various types of biological molecules can be modified in number and in loads of exosomes in cardiac lesions, such as MI, reperfusion injury, myocardial ischemia, atherosclerosis, hypertension, and cardiomyopathy due to sepsis, and can influence the function of the cardiomyocytes and contribute to the pathogenesis of CVD. A therapeutic strategy based on exosomes can be used to decrease myocardial injury and induce cardiac regeneration [67].

The CD34+ cells are a structural component in the formation of neovasculature in ischemic tissue, and secrete paracrine factors that stimulate the formation of new vessels, an element of proangiogenic paracrine activity associated with CD34+ cells secreted by exosomes, with a potent angiogenic paracrine activity both *in vitro* and *in vivo*. Exosomes stimulate mechanisms mediated by genetic receptors by transferring proteins, RNA, or microRNA directly to the cytoplasm of target cells [68].

All types of cardiac cells are able to secrete ExMVs, which are captured by the recipient cells and can alter gene expression or activate cascades of intracellular signals. A possible therapeutic intervention to reduce the ischemia/reperfusion injury (I/R) is the pre or post-conditioning, which allows the activation of the salvage recovery pathway by reperfusion salvage kinase (RISK), where transcription factors such as factor 1α-induced hypoxia (HIF-1α), mediators such as heat shock protein 70 kDa (Hsp70) and inducible nitric oxide synthase (iNOS), demonstrated in an in vitro preconditioning model, which does not influence the secretion of EV and its morphology, but it has an effect on EV size and particularly on its charge. EVs derived from fibroblasts enhanced cell migration and the effect was improved by means of in vitro preconditioning. An experimental model of *in vitro* preconditioning of cardiac cells concluded that it does not influence the concentration of ExMVs, but regulates their load and affects migration [69].

In conclusion, cardiac cells, such as cardiomyocytes, endothelial cells, and fibroblasts, release exosomes that modulate cellular functions. The exosomes released by CPCs are cardioprotective and improve cardiac function after MI, compared to that achieved by progenitor cells, and they have antiapoptotic, proangiogenic functions.
