Induced pluripotent stem cells : it looks simple but can looks deceive?

Use of derived adipose stem cells to reduce complications of cutaneous scarring in smokers. An experimental model in rats

PURPOSE

To evaluate the use of adipose-derived stem cells (ADSC) in reducing the necrosis area in an experimental model of cutaneous ischemic flap in rats submitted to subcutaneous nicotine injection to simulate a smoker patient.

METHODS

In an experimental study, 30 rats were enrolled and divided into two experimental groups of 15 animals all submitted to a subcutaneous nicotine injection to create ischemic cutaneous flaps on their backs. Other 10 animals were used only to obtain adipose tissue derived stem cells (ADSC). The first group (n=15) received ADSC treatment at the end of surgery while the other group, the control (n=15), received no other interventions. After euthanasia, a decal was performed on the whole area of the flap, accurately defining the transition from necrosis to healthy region. Photos of all animals were collected and evaluated by scales standardized by Paint-Autocad- 2015 software to define the area of flap necrosis in each rat. Student T test was performed to compare the groups, considering a p< 0.05 significant. Data were analyzed using SPSS IBM® 18 version.

RESULTS

Through the analysis of the images by the program Paint-Autocad-2015 and the area of decal obtained by the transparent sheet, we obtained a mean of 46% necrosis of the total area of the flap in the treatment group and 69.4% in the control group. In the descriptive analysis, a mean of 3.7 cm of necrosis CI 95% (3.2 - 4.2) was evident in the treatment group whereas a mean value of 5.56 CI 95% (5.2 - 5.9) was found in control group, with p value <0.001 for this comparison.

CONCLUSION

The application of adipose-derived stem cells reduces the percentage of necrosis in an experimental model of randomized cutaneous flap in rats submitted to subcutaneous nicotine injection.

Cellular regeneration strategies for macular degeneration: past, present and future

Despite considerable effort and significant therapeutic advances, age-related macular degeneration (AMD) remains the commonest cause of blindness in the developed world. Progressive late-stage AMD with outer retinal degeneration currently has no proven treatment. There has been significant interest in the possibility that cellular treatments may slow or reverse visual loss in AMD. A number of modes of action have been suggested, including cell replacement and rescue, as well as immune modulation to delay the neurodegenerative process. Their appeal in this enigmatic disease relate to their generic, non-pathway-specific effects. The outer retina in particular has been at the forefront of developments in cellular regenerative therapies being surgically accessible, easily observable, as well as having a relatively simple architecture. Both the retinal pigment epithelium (RPE) and photoreceptors have been considered for replacement therapies as both sheets and cell suspensions. Studies using autologous RPE, and to a lesser extent, foetal retina, have shown proof of principle. A wide variety of cell sources have been proposed with pluripotent stem cell-derived cells currently holding the centre stage. Recent early-phase trials using these cells for RPE replacement have met safety endpoints and hinted at possible efficacy. Animal studies have confirmed the promise that photoreceptor replacement, even in a completely degenerated outer retina may restore some vision. Many challenges, however, remain, not least of which include avoiding immune rejection, ensuring long-term cellular survival and maximising effect. This review provides an overview of progress made, ongoing studies and challenges ahead.

Stem Cells and Labeling for Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition that usually results in sudden and long-lasting locomotor and sensory neuron degeneration below the lesion site. During the last two decades, the search for new therapies has been revolutionized with the improved knowledge of stem cell (SC) biology. SCs therapy offers several attractive strategies for spinal cord repair. The transplantation of SCs promotes remyelination, neurite outgrowth and axonal elongation, and activates resident or transplanted progenitor cells across the lesion cavity. However, optimized growth and differentiation protocols along with reliable safety assays should be established prior to the clinical application of SCs. Additionally, the ideal method of SCs labeling for efficient cell tracking after SCI remains a challenging issue that requires further investigation. This review summarizes the current findings on the SCs-based therapeutic strategies, and compares different SCs labeling approaches for SCI.

Aging of Stem and Progenitor Cells: Mechanisms, Impact on Therapeutic Potential, and Rejuvenation

It was once suggested that adult or tissue-specific stem cells may be immortal; however, several recently published data suggest that their efficacy is limited by natural aging in common with most other somatic cell types. Decreased activity of stem cells in old age raises questions as to whether the age of the donor should be considered during stem cell transplantation and at what age the donor stem cells should be harvested to ensure the largest possible number of viable, functional, and non-altered stem cells. Although stem cells remain active into old age, changes in stem cells and their microenvironments inhibit their regenerative potential. The impact of aging on stem cell populations differs between tissues and depends on a number intrinsic and extrinsic factors, including systemic changes associated with immune system alterations. In this review, we describe key mechanisms of stem and progenitor cell aging and techniques that are currently used to identify signs of stem cells aging. Furthermore, we focus on the impact of aging on the capacity for proliferation, differentiation, and clinical use of stem cells. Finally, we detail the aging of embryonic, mesenchymal, and induced pluripotent stem cells, with particular emphasis on aging mechanisms and rejuvenation.

JNK/SAPK Signaling Is Essential for Efficient Reprogramming of Human Fibroblasts to Induced Pluripotent Stem Cells

Reprogramming of somatic cells to the phenotypic state termed “induced pluripotency” is thought to occur through three consecutive stages: initiation, maturation, and stabilisation. The initiation phase is stochastic but nevertheless very important as it sets the gene expression pattern that permits completion of reprogramming; hence a better understanding of this phase and how this is regulated may provide the molecular cues for improving the reprogramming process. c‐Jun N‐terminal kinase (JNK)/stress‐activated protein kinase (SAPKs) are stress activated MAPK kinases that play an essential role in several processes known to be important for successful completion of the initiation phase such as cellular proliferation, mesenchymal to epithelial transition (MET) and cell cycle regulation. In view of this, we postulated that manipulation of this pathway would have significant impacts on reprogramming of human fibroblasts to induced pluripotent stem cells. Accordingly, we found that key components of the JNK/SAPK signaling pathway increase expression as early as day 3 of the reprogramming process and continue to rise in reprogrammed cells throughout the initiation and maturation stages. Using both chemical inhibitors and RNA interference of MKK4, MKK7 and JNK1, we tested the role of JNK/SAPK signaling during the initiation stage of neonatal and adult fibroblast reprogramming. These resulted in complete abrogation of fully reprogrammed colonies and the emergence of partially reprogrammed colonies which disaggregated and were lost from culture during the maturation stage. Inhibition of JNK/SAPK signaling resulted in reduced cell proliferation, disruption of MET and loss of the pluripotent phenotype, which either singly or in combination prevented establishment of pluripotent colonies. Together these data provide new evidence for an indispensable role for JNK/SAPK signaling to overcome the well‐established molecular barriers in human somatic cell induced reprogramming. Stem Cells2016;34:1198–1212

Lab generated retina: realizing the dream

Blindness represents an increasing global problem with significant social and economic impact upon affected patients and society as a whole. In Europe, approximately one in 30 individuals experience sight loss and 75% of those are unemployed, a social burden which is very likely to increase as the population of Europe ages. Diseases affecting the retina account for approximately 26% of blindness globally and 70% of blindness in the United Kingdom. To date, there are no treatments to restore lost retinal cells and improve visual function, highlighting an urgent need for new therapeutic approaches. A pioneering breakthrough has demonstrated the ability to generate synthetic retina from pluripotent stem cells under laboratory conditions, a finding with immense relevance for basic research, in vitro disease modeling, drug discovery, and cell replacement therapies. This review summarizes the current achievements in pluripotent stem cell differentiation toward retinal cells and highlights the steps that need to be completed in order to generate human synthetic retinae with high efficiency and reproducibly from patient-specific pluripotent stem cells.

The application of induced pluripotent stem cells for bone regeneration: current progress and prospects

Loss of healthy bone tissue and dysosteogenesis are still common and significant problems in clinics. Cell-based therapy using mesenchymal stem cells (MSCs) has been performed in patients for quite some time, but the inherent drawbacks of these cells, such as the reductions in proliferation rate and osteogenic differentiation potential that occur with aging, greatly limit their further application. Moreover, embryonic stem cells (ESCs) have brought new hope to osteoregenerative medicine because of their full pluripotent differentiation potential and excellent performance in bone regeneration. However, the ethical issues involved in destroying human embryos and the immune reactions that occur after transplantation are two major stumbling blocks impeding the clinical application of ESCs. Instead, induced pluripotent stem cells (iPSCs), which are ESC-like pluripotent cells that are reprogrammed from adult somatic cells using defined transcription factors, are considered a more promising source of cells for regenerative medicine because they present no ethical or immunological issues. Here, we summarize the primary technologies for generating iPSCs and the biological properties of these cells, review the current advances in iPSC-based bone regeneration and, finally, discuss the remaining challenges associated with these cells, particularly safety issues and their potential application for osteoregenerative medicine.

Stem cell-based therapy for spinal cord injury

Stem cells (SCs) represent a new therapeutic approach for spinal cord injury (SCI) by enabling improved sensory and motor functions in animal models. The main goal of SC-based therapy for SCI is the replacement of neurons and glial cells that undergo cell death soon after injury. Stem cells are able to promote remyelination via oligodendroglia cell replacement to produce trophic factors enhancing neurite outgrowth, axonal elongation, and fiber density and to activate resident or transplanted progenitor cells across the lesion cavity. While several SC transplantation strategies have shown promising yet partial efficacy, mechanistic proof is generally lacking and is arguably the largest impediment toward faster progress and clinical application. The main challenge ahead is to spur on cooperation between clinicians, researchers, and patients in order to define and optimize the mechanisms of SC function and to establish the ideal source/s of SCs that produce efficient and also safe therapeutic approaches.

Human stem cell research and regenerative medicine--present and future

INTRODUCTION

Stem cells are cells with the ability to grow and differentiate into more than 200 cell types.

SOURCES OF DATA

We review here the characteristics and potential of human embryonic stem cells (hESCs), induced pluripotent stem cells (iPSCs) and adult stem cells (ASCs).

AREAS OF AGREEMENT

The differentiation ability of all stem cell types could be stimulated to obtain specialized cells that represent renewable sources of functional cells useful for cell-based therapy.

AREAS OF CONTROVERSY

The proof of functional differentiated cells needs to be investigated in more detail using both in vitro and in vivo assays including animal disease models and clinical studies.

GROWING POINTS

Much progress has been made in the ASCs-based therapies. Meanwhile hESCs and iPSCs have dramatically emerged as novel approaches to understand pathogenesis of different diseases.

AREAS TIMELY FOR DEVELOPING RESEARCH

A number of new strategies become very important in regenerative medicine. However, we discuss the limitations of stem cells and latest development in the reprogramming research.

Induced pluripotent stem cells can be used to model the genomic imprinting disorder Prader-Willi syndrome

The recent discovery of induced pluripotent stem cell (iPSC) technology provides an invaluable tool for creating in vitro representations of human genetic conditions. This is particularly relevant for those diseases that lack adequate animal models or where the species comparison is difficult, e.g. imprinting diseases such as the neurogenetic disorder Prader-Willi syndrome (PWS). However, recent reports have unveiled transcriptional and functional differences between iPSCs and embryonic stem cells that in cases are attributable to imprinting errors. This has suggested that human iPSCs may not be useful to model genetic imprinting diseases. Here, we describe the generation of iPSCs from a patient with PWS bearing a partial translocation of the paternally expressed chromosome 15q11-q13 region to chromosome 4. The resulting iPSCs match all standard criteria of bona fide reprogramming and could be readily differentiated into tissues derived from the three germ layers, including neurons. Moreover, these iPSCs retain a high level of DNA methylation in the imprinting center of the maternal allele and show concomitant reduced expression of the disease-associated small nucleolar RNA HBII-85/SNORD116. These results indicate that iPSCs may be a useful tool to study PWS and perhaps other genetic imprinting diseases as well.

Restoring the balance between disease and repair in multiple sclerosis: insights from mouse models

Multiple sclerosis (MS) is considered an autoimmune-mediated demyelinating disease that targets the central nervous system (CNS). Despite considerable research efforts over multiple decades, our understanding of the basic biological processes that are targeted in the disease and the mechanisms of pathogenesis are poorly understood. Consequently, current therapies directed at controlling the progression of the disease are limited in their effectiveness. Historically, the primary focus of MS research has been to define the cellular and molecular basis of the immunological pathogenic mechanisms. Recently, however, it has become clear that long-term functional recovery in MS will require the development of strategies that facilitate myelin repair in lesion areas. The emerging evidence that the adult vertebrate CNS retains the capacity to regenerate neural cells that have been lost to disease or damage has provoked intensive research focused on defining the mechanisms of myelin repair. Unfortunately, the existing animal models of MS are poorly equipped to assess myelin repair, and new validated strategies to identify therapeutics targeted at promoting myelin repair are badly needed. This Commentary will review established murine models of MS, and discuss emerging technologies that promise to provide insights into the mechanisms of myelin repair.