All articles published by are made immediately available worldwide under an open access license. No special permission is required to reuse all or part of the article published by , including figures and tables. For articles published under an open access Creative Common CC BY license, any part of the article may be reused without permission provided that the original article is clearly cited. For more information, please refer to https:///openaccess.
Feature papers represent the most advanced research with significant potential for high impact in the field. A Feature Paper should be a substantial original Article that involves several techniques or approaches, provides an outlook for future research directions and describes possible research applications.
Editor’s Choice articles are based on recommendations by the scientific editors of journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.
Uab Precision Medicine
By Irene Villalón-García Irene Villalón-García Scilit Preprints.org Google Scholar , Mónica Álvarez-Córdoba Mónica Álvarez-Córdoba Scilit Preprints.org Google Scholar , Juan Miguel Suárez-Rivero Juan Miguel Suárez-Rivero Scilit Preprints.org Google Scholar , Suleva Povea-Cabello Suleva Povea-Cabello Scilit Preprints.org Google Scholar , Marta Talaverón-Rey Marta Talaverón-Rey Scilit Preprints.org Google Scholar , Alejandra Suárez-Carrillo Alejandra Suárez-Carrillo Scilit Preprints.org Google Scholar , Manuel Munuera-Cabeza Manuel Munuera-Cabeza Scilit Preprints.org Google Scholar and José Antonio Sánchez-Alcázar José Antonio Sánchez-Alcázar Scilit Preprints.org Google Scholar *
Centro Andaluz de Biología del Desarrollo (CABD-CSIC-Universidad Pablo de Olavide), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, 41013 Sevilla, Spain
Rare diseases are those that have a low prevalence in the population (less than 5 individuals per 10, 000 inhabitants). However, infrequent pathologies affect a large number of people, since according to the World Health Organization (WHO), there are about 7000 rare diseases that affect 7% of the world’s population. Many patients with rare diseases have suffered the consequences of what is called the diagnostic odyssey, that is, extensive and prolonged serial tests and clinical visits, sometimes for many years, all with the hope of identifying the etiology of their disease. For patients with rare diseases, obtaining the genetic diagnosis can mean the end of the diagnostic odyssey, and the beginning of another, the therapeutic odyssey. This scenario is especially challenging for the scientific community, since more than 90% of rare diseases do not currently have an effective treatment. This therapeutic failure in rare diseases means that new approaches are necessary. Our research group proposes that the use of precision or personalized medicine techniques can be an alternative to find potential therapies in these diseases. To this end, we propose that patients’ own cells can be used to carry out personalized pharmacological screening for the identification of potential treatments.
Engineering Precision Medicine
Despite the important emphasis placed on the investigation of rare diseases and the development of orphan drugs by national governments, the pharmaceutical industry and private foundations, there are no adequate treatments for approximately 95% of rare diseases. The advance of genomics and functional proteomics has placed medicine in recent years at the gates of a new revolution, precision medicine, characterized by the development of molecular, genetic and cellular therapies that materialize in specific treatments for particular patients [1]. The rationale for this approach is that different mutations and inter-individual genetic variability can influence significantly both the disease sensitivity and the response to particular pharmacological therapies. The goal of personalized medicine is to maximize the likelihood of therapeutic efficacy and minimize the risk of drug toxicity for an individual patient.
The last decade has witnessed a rapid acceleration in our understanding of the genetic basis of many diseases. With this greater understanding comes the possibility of redefining the disease at a higher resolution and, along with this, aiming for a more precise therapy.
The precision medicine strategy has been successfully applied in different areas of medical care such as cardiology, oncology and nutrition and has a hopeful future in rare diseases [2].
I Have A Rare Disease. We Must Rethink How We Value Care.
At present, fibroblasts cell cultures derived from patients are easily obtained by means of skin biopsies. These cellular models are very informative to understand the pathophysiological alterations and the response of particular mutations to specific treatments. Furthermore, current direct or indirect cell transdifferentiation techniques make it possible to generate two of the most affected cell types in many rare diseases such as neurons or muscle fibers [3, 4]. This personalized approach can be useful both for the evaluation of new drugs and for the repositioning of existing ones (Figure 1). Another advantage of precision personalized medicine is that it allows the evaluation of cellular response to combinations of different drugs, thereby diversifying possible therapeutic targets and optimizing potential treatments for patients.
In 2006, a hallmark publication by Yamanaka et al. redefined the field of stem cell biology [5]. For the first time, adult fully differentiated somatic cells were dedifferentiated to the pluripotent state using four transcription factors; OCT4 (also known as POU5F1), SOX2, KLF4 and MYC, yielding iPSCs, which have the capacity to differentiate into all types of somatic cells. These stem cell models carrying patient-specific mutations have become a valuable tool for rare disease research [3]. iPSCs provide numerous advantages as models for biomedical research. First, inducing pluripotency from somatic cells offers a non-invasive method to obtain cellular models for particular mutations and the generation of certain cell types that are difficult to obtain directly from humans. Second, iPSC models enable a sufficient number of cells for experimental work [6]. Thus, this model has been used for pathomechanism studies, differentiation assays, and drug screening [7].
However, the use of iPSCs for disease modelling has several disadvantages, such as its complexity and high cost of production [8]. Moreover, induction of pluripotency is accompanied by epigenetic reprogramming and a metabolic shift from OXPHOS toward glycolysis and vice versa during differentiation. Furthermore, the high expression of pluripotency genes increases the number of tumorigenic cells remaining in culture after differentiation [9]. In addition, it has been reported that the nuclear genome of iPSCs is genetically instable and frequently harbours mitochondrial DNA (mtDNA) aberrations [10]. For instance, it has been reported in inherited mitochondrial diseases that nuclear reprogramming reduces the copy number of mtDNA and may change the proportions of wild-type and mutant mtDNA (the degree of heteroplasmy), which determines the onset and severity of the symptoms of mitochondrial diseases. In addition, the degree of mtDNA heteroplasmy has been suggested to vary among different iPSC clones, indicating uneven mitochondrial segregation during reprogramming. Therefore, it is possible to obtain mtDNA mutation-free clones of iPSCs from patients with pathogenic mtDNA mutations. However, this fact can be an advantage since patient-derived mutation-free clones of iPSCs could be used for cell replacement therapies.
Rare Disease: Where Precision Medicine Was Born
Since the first direct reprogramming of a differentiated cell type into another was achieved, it took more than twenty years to reprogram fibroblasts into neuronal cells [11]. The first successful direct conversion of murine fibroblasts into induced neurons (iNs) was achieved in 2010, when Wernig and colleagues identified a combination of three proneural factors (the proneural gene ASCL1 and the transcription factors Brain-2 [BRN2] and Myelin transcription factor 1 like [MYT1L]), which were able to convert murine embryonic and postnatal fibroblasts into functional neurons in vitro [12]. The expression of these three transcription factors was required to obtain electrophysiologically functional neurons. Since then, iNs are defined as the product of directly reprogrammed neurons starting from somatic cells avoiding passing through the pluripotent stage. About one year later, this approach was transferred to human fibroblasts, using the additional factor Neurogenic Differentiation factor 1 (NEUROD1) to obtain iNs [13]. It was observed that longer conversion times were needed for human cells in comparison to mouse cells. Since then, the strategy of solely expression of different transcription factors has been successfully used to generate iNs [14, 15, 16]. However, from the beginning, the generation of iNs using direct reprogramming has had a main challenge: reaching a high conversion efficiency, which is defined as the percentage of iNs obtained relative to the number of starting cells plated. Although it can be very variable depending on the starting cells and the protocol used, the first approaches using direct reprogramming obtained very poor conversion efficiencies [17, 18]. Moreover, it is also necessary to reach a good purity percentage, which is defined as the number of iNs in the final population related to the total cells in the plate. These two parameters are crucial since neurons are post-mitotic cells not able to further expand. In conclusion, a main drawback of direct transdifferentiation is a limited number of functional cells that can be obtained, which hence unmeet the requisite for drug screening [19]. Over the next years, new tools and strategies have been found to improve efficiency and purity of neuronal conversion. For example, the expression of different combinations of neuronal-specific miRNAs has been shown to direct the conversion of somatic cells into iNs [20, 21], although
At present, fibroblasts cell cultures derived from patients are easily obtained by means of skin biopsies. These cellular models are very informative to understand the pathophysiological alterations and the response of particular mutations to specific treatments. Furthermore, current direct or indirect cell transdifferentiation techniques make it possible to generate two of the most affected cell types in many rare diseases such as neurons or muscle fibers [3, 4]. This personalized approach can be useful both for the evaluation of new drugs and for the repositioning of existing ones (Figure 1). Another advantage of precision personalized medicine is that it allows the evaluation of cellular response to combinations of different drugs, thereby diversifying possible therapeutic targets and optimizing potential treatments for patients.
In 2006, a hallmark publication by Yamanaka et al. redefined the field of stem cell biology [5]. For the first time, adult fully differentiated somatic cells were dedifferentiated to the pluripotent state using four transcription factors; OCT4 (also known as POU5F1), SOX2, KLF4 and MYC, yielding iPSCs, which have the capacity to differentiate into all types of somatic cells. These stem cell models carrying patient-specific mutations have become a valuable tool for rare disease research [3]. iPSCs provide numerous advantages as models for biomedical research. First, inducing pluripotency from somatic cells offers a non-invasive method to obtain cellular models for particular mutations and the generation of certain cell types that are difficult to obtain directly from humans. Second, iPSC models enable a sufficient number of cells for experimental work [6]. Thus, this model has been used for pathomechanism studies, differentiation assays, and drug screening [7].
However, the use of iPSCs for disease modelling has several disadvantages, such as its complexity and high cost of production [8]. Moreover, induction of pluripotency is accompanied by epigenetic reprogramming and a metabolic shift from OXPHOS toward glycolysis and vice versa during differentiation. Furthermore, the high expression of pluripotency genes increases the number of tumorigenic cells remaining in culture after differentiation [9]. In addition, it has been reported that the nuclear genome of iPSCs is genetically instable and frequently harbours mitochondrial DNA (mtDNA) aberrations [10]. For instance, it has been reported in inherited mitochondrial diseases that nuclear reprogramming reduces the copy number of mtDNA and may change the proportions of wild-type and mutant mtDNA (the degree of heteroplasmy), which determines the onset and severity of the symptoms of mitochondrial diseases. In addition, the degree of mtDNA heteroplasmy has been suggested to vary among different iPSC clones, indicating uneven mitochondrial segregation during reprogramming. Therefore, it is possible to obtain mtDNA mutation-free clones of iPSCs from patients with pathogenic mtDNA mutations. However, this fact can be an advantage since patient-derived mutation-free clones of iPSCs could be used for cell replacement therapies.
Rare Disease: Where Precision Medicine Was Born
Since the first direct reprogramming of a differentiated cell type into another was achieved, it took more than twenty years to reprogram fibroblasts into neuronal cells [11]. The first successful direct conversion of murine fibroblasts into induced neurons (iNs) was achieved in 2010, when Wernig and colleagues identified a combination of three proneural factors (the proneural gene ASCL1 and the transcription factors Brain-2 [BRN2] and Myelin transcription factor 1 like [MYT1L]), which were able to convert murine embryonic and postnatal fibroblasts into functional neurons in vitro [12]. The expression of these three transcription factors was required to obtain electrophysiologically functional neurons. Since then, iNs are defined as the product of directly reprogrammed neurons starting from somatic cells avoiding passing through the pluripotent stage. About one year later, this approach was transferred to human fibroblasts, using the additional factor Neurogenic Differentiation factor 1 (NEUROD1) to obtain iNs [13]. It was observed that longer conversion times were needed for human cells in comparison to mouse cells. Since then, the strategy of solely expression of different transcription factors has been successfully used to generate iNs [14, 15, 16]. However, from the beginning, the generation of iNs using direct reprogramming has had a main challenge: reaching a high conversion efficiency, which is defined as the percentage of iNs obtained relative to the number of starting cells plated. Although it can be very variable depending on the starting cells and the protocol used, the first approaches using direct reprogramming obtained very poor conversion efficiencies [17, 18]. Moreover, it is also necessary to reach a good purity percentage, which is defined as the number of iNs in the final population related to the total cells in the plate. These two parameters are crucial since neurons are post-mitotic cells not able to further expand. In conclusion, a main drawback of direct transdifferentiation is a limited number of functional cells that can be obtained, which hence unmeet the requisite for drug screening [19]. Over the next years, new tools and strategies have been found to improve efficiency and purity of neuronal conversion. For example, the expression of different combinations of neuronal-specific miRNAs has been shown to direct the conversion of somatic cells into iNs [20, 21], although
0 comments:
Post a Comment