title: Electron microscopy reveals the presence of viruses in mouse embryonic fibroblasts but neither in human embryonic fibroblasts nor in human mesenchymal cells used for hESC maintenance: toward an implementation of microbiological quality assurance program in stem cell banks.
abstract: Human embryonic stem cells (hESCs) are expected to open up new avenues in regenerative medicine by allowing the generation of transplantable cells to be used in future cell replacement therapies. Maintenance of hESCs in the presence of xenogenic compounds is likely to prevent their use in future therapeutic applications in humans. Recently, it has been claimed that human foreskin-derived human embryonic fibroblast (HEFs) and human adult marrow cells have the ability to support prolonged expansion of hESCs in culture similar to murine feeders. Here, to minimize the use of xenogenic components for hESC maintenance, we performed transmission electron microscopy-based microbiological studies in an attempt to implement a microbiological Quality Assurance Program in Stem Cell Banks by determining the potential presence of viral particles in MEFs compared with human HEFs and bone marrow-derived mesenchymal cells. We observed in three out of nine MEF samples (33.3%) viruses belonging to the Retroviridae family. Within the Retroviridae family, these viruses have a C morphology, which indicates they belong to the subfamily Orthoretroviridae. In contrast, no viral particles could be observed in either the HEF samples (n = 5) or the human BM-derived mesenchymal cells (n = 9) analyzed. Based on these experimental microbiological data, we recommend the implementation of microbiological Quality Assurance Programs by means of transmission electron microscopy as a routine technique to assess the potential presence of viral particles in any feeder cell used in stem cell banks and support the use of human cells rather than murine cells as feeders to maintain hESC cultures in an undifferentiated state.
authors.affiliation: Stem Cell Bank of Andalucía (Spanish Central Node), Centro de Investigaciones Biomédicas, Parque Tecnológico de las Ciencias de la Salud, Granada, Spain. fernando.cobo.sspa@juntadeandalucia.es
authors.forename: Fernando
authors.initials: F
authors.lastname: Cobo
authors.forename: José María
authors.initials: JM
authors.lastname: Navarro
authors.forename: Ma Inmaculada
authors.initials: MI
authors.lastname: Herrera
authors.forename: Amparo
authors.initials: A
authors.lastname: Vivo
authors.forename: David
authors.initials: D
authors.lastname: Porcel
authors.forename: Concepción
authors.initials: C
authors.lastname: Hernández
authors.forename: Manuel
authors.initials: M
authors.lastname: Jurado
authors.forename: Javier
authors.initials: J
authors.lastname: García-Castro
authors.forename: Pablo
authors.initials: P
authors.lastname: Menendez
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques / Q000592:standards*; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000648:ultrastructure / Q000821:virology*; D005347:Fibroblasts / Q000648:ultrastructure / Q000821:virology*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000648:ultrastructure / Q000821:virology*; D051379:Mice; D008854:Microscopy, Electron; D011786:Quality Control; D014015:Tissue Banks / Q000592:standards