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This article summarizes the recent activity of the International Stem Cell Banking Initiative (ISCBI) held at the California Institute for Regenerative Medicine (CIRM) in California (June 26, 2016) and the Korean National Institutes for Health in Korea (October 19-20, 2016). Through the workshops, ISCBI is endeavoring to support a new paradigm for human medicine using pluripotent stem cells (hPSC) for cell therapies. Priority considerations for ISCBI include ensuring the safety and efficacy of a final cell therapy product and quality assured source materials, such as stem cells and primary donor cells. To these ends, ISCBI aims to promote global harmonization on quality and safety control of stem cells for research and the development of starting materials for cell therapies, with regular workshops involving hPSC banking centers, biologists, and regulatory bodies. Here, we provide a brief overview of two such recent activities, with summaries of key issues raised. Stem Cells Translational Medicine 2017;6:1956-1962., (© 2017 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)

To date, all human embryonic stem cells (hESCs) available for research require unidentified soluble factors secreted from feeder layers to maintain the undifferentiated state and pluripotency. Activation of STAT3 by leukemia inhibitory factor is required to maintain "stemness" in mouse embryonic stem cells, but not in hESCs, suggesting the existence of alternate signaling pathways for self-renewal and pluripotency in human cells. Here we show that activin A is secreted by mouse embryonic feeder layers (mEFs) and that culture medium enriched with activin A is capable of maintaining hESCs in the undifferentiated state for >20 passages without the need for feeder layers, conditioned medium from mEFs, or STAT3 activation. hESCs retained both normal karyotype and markers of undifferentiated cells, including Oct-4, nanog, and TRA-1-60 and remained pluripotent, as shown by the in vivo formation of teratomas.

The preservation of "stemness" in mouse embryonic stem (mES) cells is maintained through a signal transduction pathway that requires the gp130 receptor, the interleukin-6 (IL-6) family of cytokines, and the Janus Kinase-signal transducer and activator (JAK/STAT) pathway. The factors and signaling pathways that regulate "stemness" in human embryonic stem (hES) cells remain to be elucidated. Here we report that STAT3 activation is not sufficient to block hES cell differentiation when the cells are grown on mouse feeder cells or when they are treated with conditioned media from feeder cells. Human ES cells differentiate in the presence of members of the IL-6 family of cytokines including leukemia inhibitory factor (LIF) and IL-6 or in the presence of the designer cytokine hyper-IL-6, which is a complex of soluble interleukin-6 receptor (IL-6R) and IL-6 with greatly enhanced bioactivity. Human ES cells express LIF, IL-6, and gp130 receptors, as well as the downstream signaling molecules. Stimulation of human and mouse ES cells with gp130 cytokines resulted in a robust phosphorylation of downstream ERK1, ERK2, and Akt kinases, as well as the STAT3 transcription factor. Loss of the pluripotency markers Nanog, Oct-4, and TRA-1-60 was observed in hES cells during gp130-dependent signaling, indicating that signaling through this pathway is insufficient to prevent the onset of differentiation. These data underscore a fundamental difference in requirements of murine versus hES cells. Furthermore, the data demonstrate the existence of an as-yet-unidentified factor in the conditioned media of mouse feeder layer cells that acts to maintain hES cell renewal in a STAT3-independent manner.

Genes required to maintain pluripotency in human embryonic stem (hES) cells are largely unknown, with the exception of OCT-4, a homolog of mouse Oct-4, which is critical for the establishment of the embryonic inner cell mass and the generation of totipotent mouse embryonic stem (mES) cell lines. In the current study, we identified two genes with expression similar to OCT-4, in that they are largely restricted to pluripotent hES cells, premeiotic germ lineage cells, and testicular germ cell tumor cells. Furthermore, we determined that upon hES cell differentiation, their expression is downregulated. The genes we identified in the current study include the human stella-related (STELLAR) gene, which encodes a highly divergent protein (with just 32.1% identity to mouse stella over the 159 amino acid sequence) that maps to human chromosome 12p13. Notably, human STELLAR is located distal to a previously uncharacterized homeobox gene, which is the human homolog of the recently identified murine gene, Nanog, and proximal to the GDF3 locus, whose transcription is restricted to germ cell tumor cells. Our characterization of STELLAR, NANOG, and GDF3 suggests that they may play a similar role in humans as in mice, in spite of their remarkable evolutionary divergence.

The filarial parasite Onchocerca volvulus is the causative agent of river blindness. The adult worms produce microfilariae (mf), which are responsible for the disease pathogenesis; mf activate the complement system, but the activation stops before the formation of terminal complement complexes. Because of the arrest of complement activation, this study analyzed binding of the main alternative pathway regulator, factor H (fH), to the mf. The mf bound fH after incubation in nonimmune human serum or with purified radiolabeled fH. In the presence of factor I, mf-bound fH promoted the cleavage of complement 3 molecule b (C3b) to iC3b. An analysis with recombinant constructs of fH showed that the C-terminal short consensus repeats (SCRs) 8-20 of fH bound to mf, whereas the N-terminal SCRs 1-7 containing the complement-regulatory domains in SCRs 1-5 did not. Thus, mf of the nematode O. volvulus may evade human complement by binding fH and by promoting inactivation of C3b into iC3b.