Toward the Future: The New Challenges of the Cell Therapy and Potential of Regenerative Medicine

Stem cells are always regarded as cells with unique and extraordinary properties. SCs are able to self-renew and differentiate into specialized cells and this is a great advantage to maintain homeostasis in the body. The cells can divide with two different strategies and they are influenced by intrinsic and extrinsic factors of their microenvironment in which there are: the niche. The internal signals are represented by the genetic information of the cells, the external signals come instead from the microenvironment and they are physical or chemical signals. Stem cells are classified into embryonic stem cells and adult stem cells. Embryonic stem cells are derived from the inner cell mass of the blastocyst, these have great potential and over the years researchers have studied their properties and the importance of keeping them in appropriate culture conditions. Adult stem cells are found in a large number of tissues and have the very important role to replace damaged cells in living tissue. SCs can also be classified according to their potential, so they can be defined as totipotent, pluripotent, multipotent and they can differentiate respectively in a decreasing number of specialized cells of the body.

The hematopoietic stem cells (HSCs) are a population responsible of the hematopoiesis’s process; they have the characteristic to repeatedly divide or they can mature to generate different cell types, through the process of hematopoiesis. In this regenerative process, the cells are organized in a hierarchical structure: at the summit there are the hematopoietic stem cells and to the base, there is the progeny in differentiation. Hematopoietic cells commissioned to a particular hematic spinneret can be induced to convert themself in cells of the different spinner; another important feature of HSC is plasticity, that is the potential differentiation, thanks to which the cells are capable to undertake phenotypic and functional characteristics of other organs or tissues.

The process of hematopoiesis is regulated by numerous external and internal factors which operate on transcriptional level; this factors can also interact with each other.

Recently, knowledge about HSCs increases more and more; which allows their application also in clinical scope, to permanently treat serious pathologies.

Regenerative medicine is a new concept of developing medicine. This field of science concerns reconstruction and repair of damaged tissues and organs. In physiological conditions, their integrity and functionality are ensured by the presence of adult stem cells that maintain and renew effectively all cell types. When there are injuries resulting from different causes, its essential to reconstitute the original structure and this represents the goal of regenerative medicine. The aim is to employ stem cells in clinic as cell therapy. For obtaining this result, its necessary to know the biology of stem cells and then its essential to have technologies useful to regenerate them in culture and allow their vitality. Today stem cells are a therapeutic reality: their potentiality helped in healing many kinds of diseases and restore the health of patients. With the progress of research and the development of new therapy protocols, it will be possible to expand stem cell therapy to different specialized areas of pathology.

The derivation of human embryonic stem cells in the last decades, made possible by the parallel and growing development of in vitro fertilization and embryo cryopreservation technologies, have opened the door for regenerative medicine. The study of cell replacement in loss of function diseases has received further impulse by the derivation of induced pluripotent cells less than 10 years ago. Currently, pluripotent cells are extensively employed in disease modeling, toxicology testing, and drug discovery. Phase I clinical trials with both embryonic and induced pluripotent cells derivates have been underway for a few years now, and initial results have been published recently. As the field of regenerative medicine moves forward at an impressive pace, we aim to review the origin and characteristics of the different kind of pluripotent stem cells, their potential use in key translational areas, and the challenges and opportunities that we face for their integrated use in a modern and personalized medicine.

This chapter describes hematopoietic stem cells and their therapeutic uses to cure otherwise lethal, malignant and non-malignant diseases. Here we analyze the biological characteristics of different hematopoietic stem cell sources and how they are mobilized, collected, selected from the patient himself for autologous transplantation, or from matched or mismatched, related or unrelated donors for allogeneic transplantation [1 - 3]. Hematopoietic stem cell transplantation has been implemented for decades and has undergone many improvements over the years [3]. Today it is a safe, feasible option for selected patients and it still remains the only cure for a wide range of malignancies or non-malignant diseases despite advances in understanding disease genetics and biology. Moreover, with improvements in conditioning regimens and graft manipulation [2, 4], cells can be transplanted to enhance immune reconstitution and reduce relapse, which are the most common cause of transplant failure [2, 4]. Given the immunological modulation and anti-leukemic effect of these cells, conditioning regimen can be reduced and transplantation is now extended to elderly patients who are more susceptible to drug toxicity.

Recent advanced protocols on cell reprogramming for the generation of human induced pluripotent stem cells (hiPSCs) has improved the comprehension of the pathogenic mechanisms and the development of new drugs. In fact, disease-specific pluripotent stem cells offer an ideal platform for both cell and gene therapy protocol applications and represent a good possibility for new and personalized pharmacological treatments. Without any doubt, the most innovative therapies are those which provide a site specific gene correction, and are suitable to those diseases for which a drug’s therapy is not available. In the last decade have emerged ZFNs, TALENs, and the CRISPR/Cas9 system, tools for genome engineering, consisting of a sequence-specific DNA-binding domain and a non-specific DNA cleavage domain, that allow to correct mutated genes in vitro.

In this chapter, we focus on hiPSCs as a target cells for gene manipulation: new strategies as Zinc-finger nucleases, TALENs and CRISPR/ Cas9 have been developed to maximize the efficiency of genome editing protocols on human reprogrammed cells. Indeed, humanized iPSCs-based disease model systems exploit an individualized cellbased platform that has unlimited growth potential for novel regenerative strategies and clinical therapeutics, along with companion diagnostics, to predict and prognosticate the molecular basis of various human diseases.

This chapter discusses alternative methods for drug delivery. Specifically, we focused on the use of mesenchymal stem cells (MSCs) and to show how these stem cells can be available as off-the-shelf cells. The advantages of MSCs are their unique immune properties and the ability of these cells to migrate to areas of inflammation such as tumors. In addition, MSCs are easy to harvest with several fold expansion, as well as little to no ethical concern. Although MSCs are similar by phenotype, the effectiveness from each source needs to be compared for homing to the desired organ/tissue, intercellular communication and the delivery of non-coding RNA through secreted exosomes. A major advantage of MSCs is the ease by which they can become available as off-the-shelf cells containing the drugs or RNA for immediate transplant to patients. There is little concern that MSCs will linger for a prolonged period because the clinical and experimental evidence indicate that allogeneic MSCs (off-the-shelf) can be readily cleared by the immune system. The chapter discusses why there is an immediate need for cellular delivery of drugs, given the cumbersome regulation and confounds of current single drug trials.