Establishment of Skeletal Myogenic Progenitors from Non-Human Primate Induced Pluripotent Stem Cells.

Pluripotent stem (PS) cells enable the scalable production of tissue-specific derivatives with therapeutic potential for various clinical applications, including muscular dystrophies. Given the similarity to human counterparts, the non-human primate (NHP) is an ideal preclinical model to evaluate several questions, including delivery, biodistribution, and immune response. While the generation of human-induced PS (iPS)-cell-derived myogenic progenitors is well established, there have been no data for NHP counterparts, probably due to the lack of an efficient system to differentiate NHP iPS cells towards the skeletal muscle lineage. Here, we report the generation of three independent Macaca fascicularis iPS cell lines and their myogenic differentiation using PAX7 conditional expression. The whole-transcriptome analysis confirmed the successful sequential induction of mesoderm, paraxial mesoderm, and myogenic lineages. NHP myogenic progenitors efficiently gave rise to myotubes under appropriate in vitro differentiation conditions and engrafted in vivo into the TA muscles of NSG and FKRP-NSG mice. Lastly, we explored the preclinical potential of these NHP myogenic progenitors in a single wild-type NHP recipient, demonstrating engraftment and characterizing the interaction with the host immune response. These studies establish an NHP model system through which iPS-cell-derived myogenic progenitors can be studied.

Major Histocompatibility Complex-Matched Arteries Have Similar Patency to Autologous Arteries in a Mauritian Cynomolgus Macaque Major Histocompatibility Complex-Defined Transplant Model.

Background Arterial bypass and interposition grafts are used routinely across multiple surgical subspecialties. Current options include both autologous and synthetic materials; however, each graft presents specific limitations. Engineering artificial small-diameter arteries with vascular cells derived from induced pluripotent stem cells could provide a useful therapeutic solution. Banking induced pluripotent stem cells from rare individuals who are homozygous for human leukocyte antigen alleles has been proposed as a strategy to facilitate economy of scale while reducing the potential for rejection of induced pluripotent stem cell-derived transplanted tissues. Currently, there is no standardized model to study transplantation of small-diameter arteries in major histocompatibility complex-defined backgrounds. Methods and Results In this study, we developed a limb-sparing nonhuman primate model to study arterial allotransplantation in the absence of immunosuppression. Our model was used to compare degrees of major histocompatibility complex matching between arterial grafts and recipient animals with long-term maintenance of patency and function. Unexpectedly, we (1) found that major histocompatibility complex partial haplomatched allografts perform as well as autologous control grafts; (2) detected little long-term immune response in even completely major histocompatibility complex mismatched allografts; and (3) observed that arterial grafts become almost completely replaced over time with recipient cells. Conclusions Given these findings, induced pluripotent stem cell-derived tissue-engineered blood vessels may prove to be promising and customizable grafts for future use by cardiac, vascular, and plastic surgeons.

Simultaneous Reprogramming and Gene Correction of Patient Fibroblasts.

The derivation of genetically modified induced pluripotent stem (iPS) cells typically involves multiple steps, requiring lengthy cell culture periods, drug selection, and several clonal events. We report the generation of gene-targeted iPS cell lines following a single electroporation of patient-specific fibroblasts using episomal-based reprogramming vectors and the Cas9/CRISPR system. Simultaneous reprogramming and gene targeting was tested and achieved in two independent fibroblast lines with targeting efficiencies of up to 8% of the total iPS cell population. We have successfully targeted the DNMT3B and OCT4 genes with a fluorescent reporter and corrected the disease-causing mutation in both patient fibroblast lines: one derived from an adult with retinitis pigmentosa, the other from an infant with severe combined immunodeficiency. This procedure allows the generation of gene-targeted iPS cell lines with only a single clonal event in as little as 2 weeks and without the need for drug selection, thereby facilitating "seamless" single base-pair changes.

Nonirradiated NOD,B6.SCID Il2rγ-/- Kit(W41/W41) (NBSGW) mice support multilineage engraftment of human hematopoietic cells.

In this study, we demonstrate a newly derived mouse model that supports engraftment of human hematopoietic stem cells (HSCs) in the absence of irradiation. We cross the NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NSG) strain with the C57BL/6J-Kit(W-41J)/J (C57BL/6.Kit(W41)) strain and engraft, without irradiation, the resulting NBSGW strain with human cord blood CD34+ cells. At 12-weeks postengraftment in NBSGW mice, we observe human cell chimerism in marrow (97% ± 0.4%), peripheral blood (61% ± 2%), and spleen (94% ± 2%) at levels observed with irradiation in NSG mice. We also detected a significant number of glycophorin-A-positive expressing cells in the developing NBSGW marrow. Further, the observed levels of human hematopoietic chimerism mimic those reported for both irradiated NSG and NSG-transgenic strains. This mouse model permits HSC engraftment while avoiding the complicating hematopoietic, gastrointestinal, and neurological side effects associated with irradiation and allows investigators without access to radiation to pursue engraftment studies with human HSCs.

Development of an efficient targeted cell-SELEX procedure for DNA aptamer reagents.

BACKGROUND: DNA aptamers generated by cell-SELEX offer an attractive alternative to antibodies, but generating aptamers to specific, known membrane protein targets has proven challenging, and has severely limited the use of aptamers as affinity reagents for cell identification and purification. METHODOLOGY: We modified the BJAB lymphoblastoma cell line to over-express the murine c-kit cell surface receptor. After six rounds of cell-SELEX, high-throughput sequencing and bioinformatics analysis, we identified aptamers that bound BJAB cells expressing c-kit but not wild-type BJAB controls. One of these aptamers also recognizes c-kit endogenously expressed by a mast cell line or hematopoietic progenitor cells, and specifically blocks binding of the c-kit ligand stem cell factor (SCF). This aptamer enables better separation by fluorescence-activated cell sorting (FACS) of c-kit(+) hematopoietic progenitor cells from mixed bone marrow populations than a commercially available antibody, suggesting that this approach may be broadly useful for rapid isolation of affinity reagents suitable for purification of other specific cell types. CONCLUSIONS/SIGNIFICANCE: Here we describe a novel procedure for the efficient generation of DNA aptamers that bind to specific cell membrane proteins and can be used as high affinity reagents. We have named the procedure STACS (Specific TArget Cell-SELEX).

A role for HPV16 E5 in cervical carcinogenesis.

A subset of the mucosotropic human papillomaviruses (HPV), including HPV16, are etiologic agents for the vast majority of cervical cancers, other anogenital cancers, and a subset of head and neck squamous cell carcinomas. HPV16 encodes three oncogenes: E5, E6, and E7. Although E6 and E7 have been well-studied and clearly shown to be important contributors to these cancers, less is known about E5. In this study, we used E5 transgenic mice to investigate the role of E5 in cervical cancer. When treated for 6 months with estrogen, a cofactor for cervical carcinogenesis, E5 transgenic mice developed more severe neoplastic cervical disease than similarly treated nontransgenic mice, although no frank cancers were detected. In addition, E5 when combined with either E6 or E7 induced more severe neoplastic disease than seen in mice expressing only one viral oncogene. Prolonged treatment of E5 transgenic mice with exogenous estrogen uncovered an ability of E5 to cause frank cancer. These data indicate that E5 acts as an oncogene in the reproductive tracts of female mice.

Hepatic transcriptional networks induced by exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) serves as a prototype for a range of environmental toxicants and as a pharmacologic probe to study signal transduction by the aryl hydrocarbon receptor (AHR). Despite a detailed understanding of how TCDD exposure leads to the transcriptional up-regulation of cytochrome P450-dependent monooxygenases, we know little about how compounds like TCDD lead to a variety of AHR-dependent toxic end points such as liver pathology, terata, thymic involution, and cancer. Using an acute exposure protocol and the toxic response of the mouse liver as a model system, we have begun a detailed microarray analysis to describe the transcriptional changes that occur after various TCDD doses and treatment times. Through correlation analysis of time- and dose-dependent toxicological end points, we are able to identify coordinately responsive transcriptional events that can be defined as primary transcriptional events and downstream events that may represent mechanistically linked sequelae or that have potential as biomarkers of toxicity.

Human papillomavirus 16 E5 oncogene contributes to two stages of skin carcinogenesis.

High-risk human papillomaviruses (HPVs), which cause the vast majority of cervical cancer, other anogenital cancers, and a subset of head and neck squamous cell carcinomas, encode three oncogenes: E5, E6, and E7. To determine the oncogenic properties of HPV16 E5 in vivo, we previously generated K14E5 transgenic mice, in which expression of E5 was directed to the basal compartment of stratified squamous epithelia. In these mice, E5 induced epidermal hyperplasia and spontaneous skin tumors. In the current study, we determined how E5 contributes to tumor formation in the skin using a multistage model for skin carcinogenesis that specifies the role of genes in three stages: initiation, promotion, and malignant progression. Both initiation and promotion are required steps for papilloma formation. K14E5 mice treated with the initiating agent 7,12-dimethylbenz(a)anthracene (DMBA) developed more papillomas than like-treated nontransgenic mice, whereas neither K14E5 nor nontransgenic mice treated with the promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA) developed papillomas. K14E5 mice treated with both DMBA and TPA to induce large numbers of papillomas had a higher incidence and earlier onset of carcinoma progression compared with like-treated nontransgenic mice. Thus, HPV16 E5 contributes to two stages of skin carcinogenesis: promotion and progression. The progressive neoplastic disease in K14E5 mice differed from that in nontransgenic mice in that benign tumors converted from exophytic to endophytic papillomas before progressing to carcinomas. Initial genetic and immunohistopathologic analyses did not determine the underlying basis for this distinct morphology, which correlates with a highly penetrant neoplastic phenotype.