**3. Therapeutic approach**

The control of the growth, division, and differentiation of MSCs in a safe and predictable manner is essential in tissue regeneration. They should be used as bioreactors to achieve specific cell types in conjunction with soluble factors that lead to healing. A therapeutic strategy is the transplantation of differentiated functional cells to replace cells lost or damaged by disease. However, the strategy requires regulation of the differentiation of the SC toward specific cellular destinations, including those that are outside the mesenchymal lineage, by means of trans-differentiation, where genetic manipulation can promote it and the expression of certain transcription factors for cellular reprogramming.

Because of the plasticity of MSCs, in addition to generating bone, adipose tissue, cartilage, and other skeletal structures, differentiation can generate lineages of liver, kidney, muscle, dermal, nerve, and cardiac cells; regenerate damaged tissue; and treat inflammation in the MI, brain, spinal cord, cartilage, and bone lesions, Crohn's disease, graft-versus-host disease (GvHD) and BM transplantation. The mechanisms of orientation and immunomodulation, the potential for multiple differentiations, and paracrine actions contribute to tissue repair. Induced pluripotent stem cells (iPSC) are very promising for discovering new drugs in medicine regenerative (MR), for their ability to differentiate in any type of cell, and iPSC-induced technology will allow the development of new therapies based on cells and their products as new biological drugs [22].

Transcriptional and epigenetic regulations are essential mechanisms underlying pluripotency, are studied in ESCs, allowing them to give rise to lineages of the three germ layers, and are used in basic studies of tissue formation that provided the foundation for regenerative therapy. Continuous self-renewal is an essential requirement to maintain the transcriptional profile and pluripotent state. To differentiate themselves in other cell lineages, ESCs need to change the transcriptional profiles. On the other hand, new regulators of pluripotency and gene expression may emerge with the study of miRNAs [23].

The immunomodulatory properties of MSCs are related to paracrine factors whose expression varies in each pathology. These factors have a direct impact on cells of the adaptive immune system such as T-cells. However, in the inflammatory process, MSCs secrete paracrine factors that influence other subpopulations of immune cells, such as dendritic cells and macrophages, and polarize them toward a tolerogenic phenotype. *In vivo*, these immunomodulatory factors are increased in the serum of animal models with inflammatory diseases treated with MSCs. The manipulation of immune regulatory cells could improve the immunomodulatory therapeutic strategies of MSCs. Regulatory immune cells accumulate and converge in their regulatory pathways to create a tolerogenic environment [24].

The paracrine signals of the extracellular environment influence the microenvironment of MSCs, both in proliferation and in differentiation. Many therapeutic strategies try to increase the effectiveness of regenerative therapies by direct application in the affected tissue or by differentiation in mature tissues. The MSCs have phenotypic plasticity and harbor an arsenal of bioactive molecules that are released by detecting signals in the local environment or packaging in EVs [25, 26].

The rigidity and/or topography of the cellular environment controls the differentiation of the MSCs, the physical signals determining the target, and cellular differentiation, an environment with high rigidity that leads to osteogenic differentiation, while low rigidity induces lipogenic differentiation. These effects are independent of the chemical/biochemical inducers. Physical factors, such as tension, produce a reorganization of the cytoskeleton during the differentiation of the MSCs and affect the expression of the essential gene of the process. Physical signals control the lineage specification of the MSCs, reorganizing and adjusting the cytoskeleton, and the cells perceive physical signals and transform these into biochemical and biological signals. Specifically, biophysical signals can initiate and strengthen biochemical signaling for the determination and differentiation of the destination of MSCs. The physical properties of the cell environment direct the structural adaptation and functional coupling of the cells to their environment [27].

To facilitate the identification of terms that we use in the following section, we present here abbreviations and meaning of the terms:

"Extracellular vesicle" (EV), is synonymous with "membrane vesicle" (suggested for all populations of vesicles derived from cells);

"Exosomes" are vesicles of 50–100 nm in diameter, generated by exocytosis of multivesicular bodies (MVB), and are a macromolecular complex involved in the degradation of RNA;

"Ectosoma" is a microvesicle derived from neutrophils or monocytes;

"Microparticle" (MV) is any small particle, regardless of its origin, and is more appropriate to indicate membrane-bound structures;

"Microvesicles" (ExMV) are larger extracellular membrane vesicles (100–1000 nm in diameter) [28].

The EVs are classified into three main classes:

The MSCs represent an opportunity in cell therapy because: (i) they are easily accessible; (ii) the isolation is simple, they can be expanded to clinical scales in a short period; (iii) they can be preserved with a minimum loss of potency and stored for administration; and (iv) so far they have not shown adverse reactions to allogeneic transplantation compared with auto-

The control of the growth, division, and differentiation of MSCs in a safe and predictable manner is essential in tissue regeneration. They should be used as bioreactors to achieve specific cell types in conjunction with soluble factors that lead to healing. A therapeutic strategy is the transplantation of differentiated functional cells to replace cells lost or damaged by disease. However, the strategy requires regulation of the differentiation of the SC toward specific cellular destinations, including those that are outside the mesenchymal lineage, by means of trans-differentiation, where genetic manipulation can promote it and the expression

Because of the plasticity of MSCs, in addition to generating bone, adipose tissue, cartilage, and other skeletal structures, differentiation can generate lineages of liver, kidney, muscle, dermal, nerve, and cardiac cells; regenerate damaged tissue; and treat inflammation in the MI, brain, spinal cord, cartilage, and bone lesions, Crohn's disease, graft-versus-host disease (GvHD) and BM transplantation. The mechanisms of orientation and immunomodulation, the potential for multiple differentiations, and paracrine actions contribute to tissue repair. Induced pluripotent stem cells (iPSC) are very promising for discovering new drugs in medicine regenerative (MR), for their ability to differentiate in any type of cell, and iPSC-induced technology will allow the development of new therapies based on cells and their products as new biological drugs [22]. Transcriptional and epigenetic regulations are essential mechanisms underlying pluripotency, are studied in ESCs, allowing them to give rise to lineages of the three germ layers, and are used in basic studies of tissue formation that provided the foundation for regenerative therapy. Continuous self-renewal is an essential requirement to maintain the transcriptional profile and pluripotent state. To differentiate themselves in other cell lineages, ESCs need to change the transcriptional profiles. On the other hand, new regulators of pluripotency and

The immunomodulatory properties of MSCs are related to paracrine factors whose expression varies in each pathology. These factors have a direct impact on cells of the adaptive immune system such as T-cells. However, in the inflammatory process, MSCs secrete paracrine factors that influence other subpopulations of immune cells, such as dendritic cells and macrophages, and polarize them toward a tolerogenic phenotype. *In vivo*, these immunomodulatory factors are increased in the serum of animal models with inflammatory diseases treated with MSCs. The manipulation of immune regulatory cells could improve the immunomodulatory therapeutic strategies of MSCs. Regulatory immune cells accumulate and converge in their

transplantation, and they can expand *in vitro*, without altering their main properties.

**3. Therapeutic approach**

190 Stromal Cells - Structure, Function, and Therapeutic Implications

of certain transcription factors for cellular reprogramming.

gene expression may emerge with the study of miRNAs [23].

regulatory pathways to create a tolerogenic environment [24].


The current nomenclature classifies the vesicles by their biogenesis. The criteria for classification are according to their origin, function, or biogenesis.
