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1230

The breakthrough invention of induced pluripotent stem cells (iPSCs) ignited huge excitement with the promise of unlimited autologous cell sources for future regenerative medicine. However, before this expectation turns into reality the safety and efficacy of these autologous cell products have to be meticulously evaluated and validated. Towards this end much research effort has been concentrated on three clinically relevant aspects: tumorigenesis, immunogenesis, and efficacy. So far almost all of the in vivo studies are carried out through syngeneic mouse or human to immunocompromised mouse transplantations. While these small animal models are important in the initial proof-ofconcept stages, the phylogenetic difference prevents a reliable extrapolation of the findings to the human species. On the other hand the ethical consideration renders it impossible to test iPSC products directly in human body, especially in early pre-clinical stage. The only ideal alternative model comes down to nonhuman primate due to its closeness to the human in terms of phylogenetics, physiology, and immune functions. One recent report published in the journal of Cell Reports described in detail the autologous transplantation studies using rhesus monkey iPSCs and their differentiated mesenchymal stromal cells. The major findings from this study are: 1) undifferentiated rhesus iPSCs formed teratomas in the recipient animals as predicted, but with a higher input cell threshold when compared to the test using immunocompromised mouse. The formed teratomas elicited immune response, characterized as infiltrations by lymphocytes. 2) In contrast the differentiated iPSC product in the form of mesodermal stromal-like cells did not form teratomas after transplantation. As expected these cells differentiated further and formed nascent bone tissue in the implants. The differentiated engraftments and thus-derived bone tissues showed minimal signs of lymphocyte infiltrations. The significance of these findings is, for the first time, iPSCs as well as their differentiated derivatives are put to test in an autologous and immunocompetent nonhuman primate model closely related to human biology. Thus generated information will be extremely valuable in optimizing human iPSC culture and differentiation protocols to bring safe and effective cell products to the clinic trial.

1116

Most cells in our body are not human, but microbial; the ratio of 'them' to 'us' is about 10: 1. Perturbations of host-microbe interactions can lead to miscues and altered host responses that increase the risk of pathogenic processes and promote "western" disorders, such as obesity, diabetes, cancers, allergies, autism, asthma and in flammatory bowel diseases. In theory, dietary components can affect the equilibrium between intestinal microbes and the host, leading to altered physiology. A recent report in Nature provides additional evidence to support this theory, where it was found that the use of artificial sweeteners enhanced the risk of glucose intolerance in both mice and humans by altering the composition and behavior of the intestinal microbiota. Notably, changes of the bacterial Taxa (an over-representation of Bacteroides and an under-representation of Clostridiales) following the consumption of artificial sweeteners was previously found to be associated with type 2 diabetes and other chronic diseases.

1107

Humans have coevolved with their microbes over thousands of years, but this relationship, is now being dramatically affected by shifts in the collective human microbiome resulting from changes in the environment and societal norms. Resulting perturbations of intestinal host-microbe interactions can lead to miscues and altered host responses that increase the risk of pathogenic processes and promote "western" disorders such as in flammatory bowel diseases, cancers, obesity, diabetes, autism, and asthma. Given the current challenges and limitations in gene therapy, approaches that can reshape the gut microbiome represent a reasonable strategy for restoring the balance between host and microbes. In this review and commentary, we highlight recent progress in our understanding of the intestinal microbiome in the context of health and diseases, focusing on mechanistic concepts that underlie the complex relationships between host and microbes. Despite these gains, many challenges lie ahead that make it difficult to close the gap between the basic sciences and clinical application. We will discuss the potential therapeutic strategies that can be used to manipulate the gut microbiota, recognizing that the promise of pharmabiotics ("bugs to drugs") is unlikely to be completely ful filled without a greater understanding of enteric microbiota and its impact on mammalian physiology. By leveraging the knowledge gained through these studies, we will be prepared to enter the era of personalized medicine where clinical inventions can be custom-tailored to individual patients to achieve better outcomes.

1226

The multifaceted sequence of events that follow fracture repair can be further complicated when considering risk factors for impaired union, present in a large and growing percentage of the population. Risk factors such as diabetes, substance abuse, and poor nutrition affect both the young and old, and have been shown to dramatically impair the body's natural healing processes. To this end, biotherapeutic interventions such as ultrasound, electrical simulation, growth factor treatment (BMP-2, BMP-7, PDGF-BB, FGF-2) have been evaluated in preclinical models and in some cases are used widely for patients with established non-union or risk/indication or impaired healing (i. e. ultrasound, BMP-2, etc.). Despite the promise of these interventions, they have been shown to be reliant on patient compliance and can produce adverse side effects such as heterotopic ossification. Gene and cell therapy approaches have attempted to apply controlled regimens of these factors and have produced promising results. However, there are safety and efficacy concerns that may limit the translation of these approaches. In addition, none of the above mentioned approaches consider genetic variation between individual patients. Several clinical and preclinical studies have demonstrated a genetic component to fracture repair and that SNPs and genetic background variation play major roles in the determination of healing outcomes. Despite this, there is a need for preclinical data to dissect the mechanism underlying the in fluence of specific gene loci on the processes of fracture healing, which will be paramount in the future of patient-centered interventions for fracture repair.

1323

The transcription factor Sox9 was first discovered in patients with campomelic dysplasia, a haploinsufficiency disorder with skeletal deformities caused by dysregulation of Sox9 expression during chondrogenesis. Since then, its role as a cell fate determiner during embryonic development has been well characterized; Sox9 expression differentiates cells derived from all three germ layers into a large variety of specialized tissues and organs. However, recent data has shown that ectoderm-and endoderm-derived tissues continue to express Sox9 in mature organs and stem cell pools, suggesting its role in cell maintenance and specification during adult life. The versatility of Sox9 may be explained by a combination of post-transcriptional modifications, binding partners, and the tissue type in which it is expressed. Considering its importance during both development and adult life, it follows that dysregulation of Sox9 has been implicated in various congenital and acquired diseases, including fibrosis and cancer. This review provides a summary of the various roles of Sox9 in cell fate specification, stem cell biology, and related human diseases. Ultimately, understanding the mechanisms that regulate Sox9 will be crucial for developing effective therapies to treat disease caused by stem cell dysregulation or even reverse organ damage.

1202

Cell chemotaxis plays a pivotal role in normal development, in flammatory response, injury repair and tissue regeneration in all organisms. It is also a critical contributor to cancer metastasis, altered angiogenesis and neurite growth in disease. The molecular mechanisms regulating chemotaxis are currently being identified and key components may be pertinent therapeutic targets. Although these components appear to be mostly common in various cells, there are important differences in chemotactic signaling networks and signal processing that result in the distinct chemotactic behavior of mesenchymal cells compared to much better studied amoeboid blood cells. These differences are not necessarily predetermined based on cell type, but are rather chosen and exploited by cells to modify their chemotactic behavior based on physical constraints and/or environmental conditions. This results in a specific type of chemotactic migration in mesenchymal cells that can be selectively targeted in disease. Here, we compare the chemotactic behavior, signaling and motility of mesenchymal and amoeboid cells. We suggest that the current model of chemotaxis is applicable for small amoeboid cells but needs to be reconsidered for large mesenchymal cells. We focus on new candidate regulatory molecules and feedback mechanisms that may account for mesenchymal cell type-specific chemotaxis.

1290

Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into various mesodermal lines forming fat, muscle, bone, and other lineages of connective tissue. MSCs possess plasticity and under special metabolic conditions may transform into cells of unusual phenotypes originating from ecto- and endoderm. After transplantation, MSCs release the humoral factors promoting regeneration of the damaged tissue. During last five years, the numbers of registered clinical trials of MSCs have increased about 10 folds. This gives evidence that MSCs present a new promising resource for cell therapy of the most dangerous diseases. The efficacy of the MSCs therapy is limited by low possibilities to regulate their conversion into cells of damaged tissues that is implemented by the pRb-E2F signaling. The widely accepted viewpoint addresses pRb as ubiquitous regulator of cell cycle and tumor suppressor. However, current publications suggest that basic function of the pRb-E2F signaling in development is to regulate cell fate and differentiation. Through facultative and constitutive chromatin modifications, pRb-E2F signaling promotes transient and stable cells quiescence, cell fate choice to differentiate, to senesce, or to die. Loss of pRb is associated with cancer cell fate. pRb regulates cell fate by retaining quiescence of one cell population in favor of commitment of another or by suppression of genes of different cell phenotype. pRb is the founder member of the "pocket protein" family possessing functional redundancy. Critical increase in the efficacy of the MSCs based cell therapy will depend on precise understanding of various aspects of the pRb-E2F signaling.

1214

Exposure to ultraviolet (UV) radiation is associated with approximately 65% of melanoma cases, and 90% of non-melanoma skin cancers (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). While the incidence of most other malignancies has either stabilized or declined, that of NMSC has increased and is developing even in younger age groups. NMSCs account for nearly 15, 000 deaths, 3.5 million new cases, and more than 3 billion dollars a year in medical costs in the United States alone, representing a major public health concern. As sun protection efforts have not been proven effective, targeted chemoprevention strategies are much needed. Skin carcinogenesis by DNA damage is considered a pre-dominant paradigm for UV toxicity. Exposure to UV radiation can activate various oncogenes while inactivating tumor suppressor genes, resulting in inappropriate survival and proliferation of keratinocytes that harbor these damages. Moreover, increasing evidence demonstrate that in flammatory responses by the immune cells within the tumor microenvironment also contribute significantly to skin tumorigenesis. Initiation and progression of skin carcinogenesis mediated by UV radiation involve complex pathways, including those of apoptosis, proliferation, autophagy, DNA repair, checkpoint signaling, metabolism, and in flammation. In this review, we highlight the recent advances in two of these key molecular processes that result in UV-mediated skin carcinogenesis. In particular, we discuss 1) pathways that regulate DNA damage repair and 2) the regulation of the in flammatory process its crosstalk with DNA repair potentially leading to non-melanoma skin carcinogenesis.

1243

Fibroblast growth factors (FGF) and their receptors serve many functions in both the developing and adult organism. Humans contain 18 FGF ligands and four FGF receptors (FGFR). FGF ligands are polypeptide growth factors that regulate several developmental processes including cellular proliferation, differentiation, and migration, morphogenesis, and patterning. FGF-FGFR signaling is also critical to the developing axial and craniofacial skeleton. In particular, the signaling cascade has been implicated in intramembranous ossification of cranial bones as well as cranial suture homeostasis. In the adult, FGFs and FGFRs are crucial for tissue repair. FGF signaling generally follows one of three transduction pathways: RAS/MAP kinase, PI3/AKT, or PLCg. Each pathway likely regulates specific cellular behaviors. Inappropriate expression of FGF and improper activation of FGFRs are associated with various pathologic conditions, unregulated cell growth, and tumorigenesis. Additionally, aberrant signaling has been implicated in many skeletal abnormalities including achondroplasia and craniosynostosis. The biology and mechanisms of the FGF family have been the subject of significant research over the past 30 years. Recently, work has focused on the therapeutic targeting and potential of FGF ligands and their associated receptors. The majority of FGF-related therapy is aimed at age-related disorders. Increased understanding of FGF signaling and biology may reveal additional therapeutic roles, both in utero and postnatally. This review discusses the role of FGF signaling in general physiologic and pathologic embryogenesis and further explores it within the context of skeletal development.

1140

Glioblastoma Multiforme (GBM) is a rapidly progressing brain tumor. Despite the relatively low percentage of cancer patients with glioma diagnoses, recent statistics indicate that the number of glioma patients may have increased over the past decade. Current therapeutic options for glioma patients include tumor resection, chemotherapy, and concomitant radiation therapy with an average survival of approximately 16 months. The rapid progression of gliomas has spurred the development of novel treatment options, such as cancer gene therapy and oncolytic virotherapy. Preclinical testing of oncolytic adenoviruses using glioma models revealed both positive and negative sides of the virotherapy approach. Here we present a detailed overview of the glioma virotherapy field and discuss auxiliary therapeutic strategies with the potential for augmenting clinical efficacy of GBM virotherapy treatment.

1185

There have been significant advancements in the field of retinal gene therapy in the past several years. In particular, therapeutic efficacy has been achieved in three separate human clinical trials conducted to assess the ability of adeno-associated viruses (AAV) to treat of a type of Leber's congenital amaurosis caused by RPE65 mutations. However, despite the success of retinal gene therapy with AAV, challenges remain for delivering large therapeutic genes or genes requiring long DNA regulatory elements for controlling their expression. For example, Stargardt's disease, a form of juvenile macular degeneration, is caused by defects in ABCA4, a gene that is too large to be packaged in AAV. Therefore, we investigated the ability of helper dependent adenovirus (HD-Ad) to deliver genes to the retina as it has a much larger transgene capacity.Using an EGFP reporter, our results showed that HD-Ad can transduce the entire retinal epithelium of a mouse using a dose of only 1×10⁵ infectious units and maintain transgene expression for at least 4 months. The results demonstrate that HD-Ad has the potential to be an effective vector for the gene therapy of the retina.

1169