BackgroundMesenchymal stem cells (MSCs) are a mixture of progenitors that are heterogeneous in their regenerative potential. Development of MSC therapies with consistent efficacy is hindered by the absence of an immunophenotype of MSC heterogeneity. This study evaluates decoy TRAIL receptor CD264 as potentially the first surface marker to detect cellular aging in heterogeneous MSC cultures.MethodsCD264 surface expression, regenerative potential, and metrics of cellular aging were assessed in vitro for marrow MSCs from 12 donors ages 20–60 years old. Male and female donors were age matched.Expression of CD264 was compared with that of p16, p21, and p53 during serial passage of MSCs.ResultsWhen CD264+ cell content was 20% to 35%, MSC cultures from young (ages 20–40 years) and older (ages 45–60 years) donors proliferated rapidly and differentiated extensively. Older donor MSCs containing < 35% CD264+ cells had a small size and negligible senescence despite the donor’s advanced chronological age. Above the 35% threshold, CD264 expression inversely correlated with proliferation and differentiation potential. When CD264+ cell content was 75%, MSCs were enlarged and mostly senescent with severely compromised regenerative potential. There was no correlation of the older donors’ chronological age to either CD264+ cell content or the regenerative potential of the donor MSCs. CD264 was upregulated after p53 and had a similar expression profile to that of p21 during serial passage of MSCs. No sex-linked differences were detected in this study.ConclusionsThese results suggest that CD264 is a surface marker of cellular age for MSCs, not the chronological age of the MSC donor. CD264 is first upregulated in MSCs at an intermediate stage of cellular aging and remains upregulated as aging progresses towards senescence. The strong inverse correlation of CD264+ cell content to the regenerative potential of MSCs has possible application to assess the therapeutic potential of patient MSCs, standardize the composition and efficacy of MSC therapies, and facilitate aging research on MSCs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-017-0649-4) contains supplementary material, which is available to authorized users.

In vivo mesenchymal stem cell (MSC) survival is relevant to therapeutic applications requiring engraftment and potentially to nonengraftment applications as well. MSCs are a mixture of progenitors at different stages of cellular aging, but the contribution of this heterogeneity to the survival of MSC implants is unknown. Here, we employ a biomarker of cellular aging, the decoy TRAIL receptor CD264, to compare the survival kinetics of two cell populations in human bone marrow MSC (hBM‐MSC) cultures. Sorted CD264+ hBM‐MSCs from two age‐matched donors have elevated β‐galactosidase activity, decreased differentiation potential and form in vitro colonies inefficiently relative to CD264− hBM‐MSCs. Counterintuitive to their aging phenotype, CD264+ hBM‐MSCs exhibited comparable survival to matched CD264− hBM‐MSCs from the same culture during in vitro colony formation and in vivo when implanted ectopically in immunodeficient NIH III mice. In vitro and in vivo survival of these two cell populations were independent of colony‐forming efficiency. These findings have ramifications for the preparation of hBM‐MSC therapies given the prevalence of aging CD264+ cells in hBM‐MSC cultures and the popularity of colony‐forming efficiency as a quality control metric in preclinical and clinical studies with MSCs.

Preclinical animal studies are essential to the development of safe and effective stem cell therapies. Bioluminescence imaging (BLI) is a powerful tool in animal studies that enables the real-time longitudinal monitoring of stem cells in vivo to elucidate their regenerative properties. This review describes the application of BLI in preclinical stem cell research to address critical challenges in producing successful stem cell therapeutics. These challenges include stem cell survival, proliferation, homing, stress response, and differentiation. The applications presented here utilize bioluminescence to investigate a variety of stem and progenitor cells in several different in vivo models of disease and implantation. An overview of luciferase reporters is provided, along with the advantages and disadvantages of BLI. Additionally, BLI is compared to other preclinical imaging modalities and potential future applications of this technology are discussed in emerging areas of stem cell research.

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The cover image is based on the Article Type Survival of aging CD264+ and CD264− populations of human bone marrow mesenchymal stem cells is independent of colony‐forming efficiency by Kim O'Connor et al., https://doi.org/10.1002/bit.27195.