Scientific Resources

Endothelial progenitor cell (EPC) nomenclature remains ambiguous and there is a general lack of concordance in the stem cell field with many distinct cell subtypes continually grouped under the term EPC." It would be highly advantageous to agree on standards to confirm an endothelial progenitor phenotype and this should include detailed immunophenotyping potency assays and clear separation from hematopoietic angiogenic cells which are not endothelial progenitors. In this review we seek to discourage the indiscriminate use of "EPCs and instead propose precise terminology based on defining cellular phenotype and function. Endothelial colony forming cells and myeloid angiogenic cells are examples of two distinct and well-defined cell types that have been considered EPCs because they both promote vascular repair,albeit by completely different mechanisms of action. It is acknowledged that scientific nomenclature should be a dynamic process driven by technological and conceptual advances; ergo the ongoing EPC" nomenclature ought not to be permanent and should become more precise in the light of strong scientific evidence. This is especially important as these cells become recognized for their role in vascular repair in health and disease and in some cases progress toward use in cell therapy. Stem Cells Translational Medicine 2017;6:1316-1320. View Publication

OBJECTIVE To investigate the long-term effect of cryopreservation on hepatocyte function,as well as attempt to improve cell viability and function through the utilization of the hypothermic preservation solution,HypoThermosol (HTS),as the carrier solution. SUMMARY BACKGROUND DATA Advances in the field of bioartificial liver support have led to an increasing demand for successful,efficient means of cryopreservation of hepatocytes. METHODS Fresh rat hepatocytes were cryopreserved in suspension in culture media (Media-cryo group) or HTS (HTS-cryo group),both supplemented with 10% DMSO. Following storage up to 2 months in liquid nitrogen,cells were thawed and maintained in a double collagen gel culture for 14 days. Hepatocyte yield and viability were assessed up to 14 days postthaw. Serial measurements of albumin secretion,urea synthesis,deethylation of ethoxyresorufin (CYT P450 activity),and responsiveness to stimulation with interleukin-6 (IL-6) were performed. RESULTS Immediate postthaw viability was 60% in Media-cryo and 79% in HTS-cryo,in comparison with control (90%). Albumin secretion,urea synthesis and CYT P450 activity yielded 33%,55%,and 59% in Media-cryo and 71%,80%,and 88% in HTS-cryo,respectively,compared with control (100%). Assessment of cellular response to IL-6 following cryopreservation revealed a similar pattern of up-regulation in fibrinogen production and suppression of albumin secretion compared with nonfrozen controls. CONCLUSIONS This study demonstrates that isolated rat hepatocytes cryopreserved using HTS showed high viability,long-term hepatospecific function,and response to cytokine challenge. These results may represent an important step forward to the utilization of cryopreserved isolated hepatocytes in bioartificial liver devices. View Publication