Phenotypic characterization and preclinical production of human lineage-negative cells for regenerative stem cell therapy

Effects of linagliptin on endothelial function and postprandial lipids in coronary artery disease patients with early diabetes: a randomized, placebo-controlled, double-blind trial

Background

Early glucose lowering intervention in subjects with type 2 diabetes mellitus was demonstrated to be beneficial in terms of micro- and macrovascular risk reduction. However, most of currently ongoing cardiovascular outcome trials are performed in subjects with manifest atherosclerosis and long-standing diabetes. Therefore, the aim of this study is to investigate the effects of the dipeptidylpeptidase-4 inhibitor linagliptin in subjects with coronary artery disease (CAD) but early type 2 diabetes mellitus (T2DM) on a set of cardiovascular surrogate measurements.

Methods

In this randomized, placebo-controlled, double-blind, single-center study, we included subjects with early diabetes (postchallenge diabetes (2 h glucose > 200 mg/dl) or T2DM treated with diet only or on a stable dose of metformin monotherapy and an HbA1c < 75 mmol/mol) and established CAD. Participants were randomized to receive either linagliptin (5 mg) once daily orally or placebo for 12 weeks. The primary outcome was the change in flow mediated dilatation (FMD). The secondary objective was to investigate the effect of linagliptin treatment on arginine bioavailability ratios [Global arginine bioavailability ratio (GABR) and arginine to ornithine ratio (AOR)]. Arginine, ornithine and citrulline were measured in serum samples with a conventional usual amino acid analysis technique, involving separation of amino acids by ion exchange chromatography followed by postcolumn continuous reaction with ninhydrin. GABR was calculated by l-arginine divided by the sum of (l-ornithine plus l-citrulline). The AOR was calculated by dividing l-arginine by l-ornithine levels. Group comparisons were calculated by using a two-sample t-test with Satterthwaite adjustment for unequal variances.

Results

We investigated 43 patients (21% female) with a mean age of 63.3 ± 8.2 years. FMD at baseline was 3.5 ± 3.1% in the linagliptin group vs. 4.0 ± 2.9% in the placebo group. The change in mean FMD in the linagliptin group was not significantly different compared to the change in the placebo group (0.43 ± 4.84% vs. − 0.45 ± 3.01%; p = 0.486). No significant improvements were seen in the arginine bioavailability ratios (GABR; p = 0.608 and AOR; p = 0.549).

Conclusion

Linagliptin treatment in subjects with CAD and early T2DM did not improve endothelial function or the arginine bioavailability ratios.

Trial registration ClinicalTrials.gov, NCT02350478 (https://clinicaltrials.gov/ct2/show/NCT02350478)

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0716-x) contains supplementary material, which is available to authorized users.

Selection of Tissue Factor-Deficient Cell Transplants as a Novel Strategy for Improving Hemocompatibility of Human Bone Marrow Stromal Cells

Intravascular transplantation of tissue factor (TF)-bearing cells elicits an instant blood-mediated inflammatory reaction (IBMIR) resulting in thrombotic complications and reduced engraftment. Here we studied the hemocompatibility of commonly used human white adipose tissue (WAT), umbilical cord (UC) and bone marrow stromal cells (BMSC) and devised a possible strategy for safe and efficient stromal cell transplantation.

Methods: Stromal cell identity, purity, and TF expression was tested by RTQ-PCR, flow cytometry and immunohistochemistry. Pro-coagulant activity and fibrin clot formation/stabilization was measured In Vitro by viscoelastic rotational plasma-thromboelastometry and in vivo by injecting sorted human stromal cells intravenously into rats. The impact of TF was verified in factor VII-deficient plasma and by sort-depleting TF/CD142⁺ BMSC.

Results: We found significantly less TF expression by a subpopulation of BMSC corresponding to reduced pro-coagulant activity. UC and WAT stroma showed broad TF expression and durable clotting. Higher cell numbers significantly increased clot formation partially dependent on coagulation factor VII. Depleting the TF/CD142⁺ subpopulation significantly ameliorated BMSC's hemocompatibility without affecting immunomodulation. TF-deficient BMSC did not produce thromboembolism in vivo, comparing favorably to massive intravascular thrombosis induction by TF-expressing stromal cells.

Conclusion: We demonstrate that plasma-based thromboelastometry provides a reliable tool to detect pro-coagulant activity of therapeutic cells. Selecting TF-deficient BMSC is a novel strategy for improving cell therapy applicability by reducing cell dose-dependent IBMIR risk. The particularly strong pro-coagulant activity of UC and WAT preparations sounds an additional note of caution regarding uncritical systemic application of stromal cells, particularly from non-hematopoietic extravascular sources.

A robust potency assay highlights significant donor variation of human mesenchymal stem/progenitor cell immune modulatory capacity and extended radio-resistance

The inherent immunomodulatory capacity of mesenchymal stem/progenitor cells (MSPCs) encouraged initiation of multiple clinical trials. Release criteria for therapeutic MSPCs cover identity, purity and safety but appropriate potency assessment is often missing. Reports on functional heterogeneity of MSPCs created additional uncertainty regarding donor and organ/source selection. We established a robust immunomodulation potency assay based on pooling responder leukocytes to minimize individual immune response variability. Comparing various MSPCs revealed significant potency inconsistency and generally diminished allo-immunosuppression compared to dose-dependent inhibition of mitogenesis. Gamma-irradiation to block unintended MSPC proliferation did not prohibit chondrogenesis and osteogenesis in vivo, indicating the need for alternative safety strategies.

Positive contrast of SPIO-labeled cells by off-resonant reconstruction of 3D radial half-echo bSSFP

This article describes a new acquisition and reconstruction concept for positive contrast imaging of cells labeled with superparamagnetic iron oxides (SPIOs). Overcoming the limitations of a negative contrast representation as gained with gradient echo and fully balanced steady state (bSSFP), the proposed method delivers a spatially localized contrast with high cellular sensitivity not accomplished by other positive contrast methods. Employing a 3D radial bSSFP pulse sequence with half-echo sampling, positive cellular contrast is gained by adding artificial global frequency offsets to each half-echo before image reconstruction. The new contrast regime is highlighted with numerical intravoxel simulations including the point-spread function for 3D half-echo acquisitions. Furthermore, the new method is validated on the basis of in vitro cell phantom measurements on a clinical MRI platform, where the measured contrast-to-noise ratio (CNR) of the new approach exceeds even the negative contrast of bSSFP. Finally, an in vivo proof of principle study based on a mouse model with a clear depiction of labeled cells within a subcutaneous cell islet containing a cell density as low as 7 cells/mm(3) is presented. The resultant isotropic images show robustness to motion and a high CNR, in addition to an enhanced specificity due to the positive contrast of SPIO-labeled cells.

Intramuscular transplantation and survival of freshly isolated bone marrow cells following skeletal muscle ischemia-reperfusion injury

BACKGROUND

Delayed treatment cellular therapies offer an attractive means to treat extremity injuries involving acute skeletal muscle ischemia-reperfusion injury (I/R). Bone marrow is a rich source of stem and progenitor cells with the potential to improve skeletal muscle regeneration. The extent to which bone marrow cells (BMCs) may be useful for I/R is not known. The purposes of this study were twofold: (1) to evaluate BMC survival following intramuscular injection 0, 2, 7, and 14 days after injury and (2) to determine whether BMCs improve functional recovery following I/R.

METHODS

Magnetic-activated cell sorting was used to isolate lineage-negative (Lin⁻) BMCs and enrich for stem and progenitor cells. To evaluate in vivo cell survival following I/R, Lin⁻ BMCs were injected intramuscularly 0, 2, 7, and 14 days after I/R, and bioluminescent imaging was performed for up to 28 days after cell injections. To assess their ability to improve muscle regeneration, intramuscular injections were performed 2 days after injury, and in vivo muscle function was assessed 14 days later.

RESULTS

Lin⁻ BMCs survived throughout the study period regardless of the timing of delivery. Intramuscular injection of Lin⁻ BMCs did not improve maximal isometric torque (300 Hz); however, both saline-injected and Lin⁻ BMC-injected muscles exhibited an increase in the twitch-tetanus ratio, suggesting that damage incurred with the intramuscular injections may have had deleterious consequences for functional recovery.

CONCLUSION

Although BMCs injected intramuscularly survived cell transplantation, they failed to improve muscle function following I/R. The ability of BMCs to persist in injured muscle following I/R lends to the possibility that with further development, their full potential can be realized.

Oxygen sensing mesenchymal progenitors promote neo-vasculogenesis in a humanized mouse model in vivo

Despite insights into the molecular pathways regulating hypoxia-induced gene expression, it is not known which cell types accomplish oxygen sensing during neo-vasculogenesis. We have developed a humanized mouse model of endothelial and mesenchymal progenitor co-transplantation to delineate the cellular compartments responsible for hypoxia response during vasculogenesis. Mesenchymal stem/progenitor cells (MSPCs) accumulated nuclear hypoxia-inducible transcription factor (HIF)-1α earlier and more sensitively than endothelial colony forming progenitor cells (ECFCs) in vitro and in vivo. Hypoxic ECFCs showed reduced function in vitro and underwent apoptosis within 24h in vivo when used without MSPCs. Surprisingly, only in MSPCs did pharmacologic or genetic inhibition of HIF-1α abrogate neo-vasculogenesis. HIF deletion in ECFCs caused no effect. ECFCs could be rescued from hypoxia-induced apoptosis by HIF-competent MSPCs resulting in the formation of patent perfused human vessels. Several angiogenic factors need to act in concert to partially substitute mesenchymal HIF-deficiency. Results demonstrate that ECFCs require HIF-competent vessel wall progenitors to initiate vasculogenesis in vivo and to bypass hypoxia-induced apoptosis. We describe a novel mechanistic role of MSPCs as oxygen sensors promoting vasculogenesis thus underscoring their importance for the development of advanced cellular therapies.

Pro-angiogenic induction of myeloid cells for therapeutic angiogenesis can induce mitogen-activated protein kinase p38-dependent foam cell formation

BACKGROUND AIMS

Clinical trials for therapeutic angiogenesis use blood- or bone marrow-derived hematopoietic cells, endothelial progenitor cells (EPC) and mesenchymal stromal cells (MSC) for vascular regeneration. Recently concerns have emerged that all three cell types could also contribute to atherosclerosis by foam cell formation. Therefore, we asked whether human myelomonocytic cells, EPC or MSC can accumulate lipid droplets (LD) and develop into foam cells.

METHODS

LD accumulation was quantified by flow cytometry, confocal microscopy and cholesterol measurement in each of the cell types. The impact of an initial pro-angiogenic induction on subsequent foam cell formation was studied to mimic relevant settings already used in clinical trials. The phosphorylation state of intracellular signaling molecules in response to the pro-angiogenic stimulation was determined to delineate the operative mechanisms and establish a basis for interventional strategies.

RESULTS

Foam cells were formed by monocytes but not by EPC or MSC after pro-angiogenic induction. Mitogen-activated protein kinase (MAPK) p38 phosphorylation was enhanced and kinase inhibition almost abrogated intracellular LD accumulation in monocytes.

CONCLUSIONS

These data suggest that hematopoietic cell preparations containing monocytes bear the risk of foam cell formation after pro-angiogenic induction. Instead, EPC and MSC may drive vascular regeneration without atherogenesis aggravation. A thorough understanding of cell biology is necessary to develop new strategies combining pro-angiogenic and anti-atherogenic effects during cell therapy.

Isolation and animal serum free expansion of human umbilical cord derived mesenchymal stromal cells (MSCs) and endothelial colony forming progenitor cells (ECFCs)

The umbilical cord is a rich source for progenitor cells with high proliferative potential including mesenchymal stromal cells (also termed mesenchymal stem cells, MSCs) and endothelial colony forming progenitor cells (ECFCs). Both cell types are key players in maintaining the integrity of tissue and are probably also involved in regenerative processes and tumor formation. To study their biology and function in a comparative manner it is important to have both cells types available from the same donor. It may also be beneficial for regenerative purposes to derive MSCs and ECFCs from the same tissue. Because cellular therapeutics should eventually find their way from bench to bedside we established a new method to isolate and further expand progenitor cells without the use of animal protein. Pooled human platelet lysate (pHPL) replaced fetal bovine serum in all steps of our protocol to completely avoid contact of the cells to xenogeneic proteins. This video demonstrates a methodology for the isolation and expansion of progenitor cells from one umbilical cord. All materials and procedures will be described.

Disparate effects of acute and chronic infection with SIVmac239 or SHIV-89.6P on macaque plasmacytoid dendritic cells

Blood plasmacytoid dendritic cells (pDCs) contribute to both innate and adaptive immune responses by secreting high levels of IFN-alpha following acute bacterial and viral infections and indirectly by augmenting cell-mediated immunity. Cross-sectional studies have shown that the number of circulating pDCs in HIV patients, compared to that in uninfected individuals, is reduced. However, since the time of infection is usually unknown in HIV-infected patients, pDC-virus interactions that occur immediately after virus exposure are poorly understood. The current study investigated pDC dynamics during acute and chronic infections of macaques with either SIVmac239 or the pathogenic SIV-HIV chimera, SHIV-89.6P, as models for HIV infection. In three rhesus and three pig-tailed macaques infected intravenously with SIVmac239, the percentages of pDCs in blood declined 2- to 6-fold during the first 6 weeks after infection and remained depressed throughout the disease course. Surprisingly, no consistent, comparable decline in peripheral blood pDCs was observed in six macaques infected with SHIV-89.6P. In this latter group, percentages of pDCs did not correlate with CD4(+) T cells, but there was an inverse relationship with viral load. In addition, when compared to naïve controls, the percentages of pDCs were reduced in spleens and peripheral lymph nodes of SIVmac239- but not SHIV-89.6P-infected animals that had progressed to AIDS. Proviral DNA was detected during the acute phase in pDCs isolated from macaques infected with either virus. These results imply that, even though macaque pDCs can be infected by both SIVmac239 and SHIV-89.6P, the subsequent effects on in vivo pathogenesis differ. The underlying mechanism(s) for these differences is unclear, but the selection of SIV or SHIV as a challenge virus might influence the outcome of some studies, such as those evaluating vaccines or the therapeutic efficacy of drugs.

Human platelet lysate can replace fetal bovine serum for clinical-scale expansion of functional mesenchymal stromal cells

BACKGROUND

Human multipotent mesenchymal stromal cells (MSCs) are promising candidates for a growing spectrum of regenerative and immunomodulatory cellular therapies. Translation of auspicious experimental results into clinical applications has been limited by the dependence of MSC propagation from fetal bovine serum (FBS).

STUDY DESIGN AND METHODS

The capacity of human platelet lysate (HPL) to replace FBS for clinical-scale MSC propagation was analyzed.

RESULTS

HPL could be efficiently produced from buffy coats. Multiplex analyses allowed a distinct HPL growth factor profile to be delineated. With a previously established two-step clinical-scale procedure, HPL was reproducibly more efficient than FBS in supporting MSC outgrowth. With only 3 x 10(5) primary culture-derived MSCs, a mean of 4.36 x 10(8) HPL-MSCs (range, 3.01 x 10(8)-5.40 x 10(8)) was obtained within a single secondary 11- to 13-day culture step. Although morphologically distinct, HPL-MSCs and FBS-MSCs did not differ significantly in terms of immunophenotype, differentiation potential in vitro, and lack of tumorigenicity in nude mice in vivo.

CONCLUSIONS

Replacing FBS with HPL prevents bovine prion, viral, and zoonose contamination of the stem cell product. This new efficient FBS-free two-step procedure for clinical-scale MSC propagation may represent a major step toward challenging new stem cell therapies.

Two steps to functional mesenchymal stromal cells for clinical application

BACKGROUND

Ex vivo expansion of multipotent mesenchymal stromal cells (MSCs) is a prerequisite for evaluating their therapeutic potential in ongoing clinical trials. Even large volumes of starting material and extended culture periods, however, do not necessarily produce 2 x 10(6) MSCs per kg per adult patient. A new two-step procedure has been devised to propagate more than 1 x 10(8) MSCs from small marrow volumes within fewer than 4 weeks.

STUDY DESIGN AND METHODS

The influence of log fold decreased MSC seeding (2500, 250, 25, 2.5/cm(2)) on clinical-scale expansion, MSC phenotype, and immunomodulatory function combined with multiplex cytokine display was analyzed. Maintenance of MSC characteristics was tested in fibroblast colony-forming unit and differentiation assays.

RESULTS

Reduced seeding density boosted MSC propagation. Low-density expanded MSCs were CD29+, CD73+, CD90+, CD105+, CD14-, CD34-, CD45-, HLA-DR-; retained their differentiation potential; and inhibited lymphocyte proliferation. This was accompanied by deregulated cytokine production. Seeding 0.7 x 10(6) to 1 x 10(6) MSCs derived from a 10- to 13-day primary culture at a low density of 28 to 40 per cm(2) permitted propagation of 1.5 x 10(8) to 3.7 x 10(8) functional MSCs within a 13- to 15-day secondary expansion step.

CONCLUSION

Primary seeding of only 10-mL marrow aspirates on approximately 0.2-m(2) culture area (Step 1) followed by expansion on 2.5 m(2) (Step 2) is sufficient to consistently generate at least 1.5 x 10(8) MSCs in fetal bovine serum-supplemented medium within less than 4 weeks. The efficiency of this two-step procedure for clinical-scale MSC propagation may facilitate rational clinical testing of MSC-based therapies.

Humanized system to propagate cord blood-derived multipotent mesenchymal stromal cells for clinical application

Background: Umbilical cord blood (UCB) is an easily accessible alternative source for multipotent mesenchymal stromal cells (MSCs) and is generally believed to provide MSCs with a higher proliferative potential compared with adult bone marrow. Limitations in cell number and strict dependence of expansion procedures from selected lots of fetal bovine serum have hampered the progress of clinical applications with UCB-derived MSCs. Methods: We analyzed the isolation and proliferative potential of human UCB MSCs compared with bone marrow MSCs under optimized ex vivo culture conditions. We further investigated human platelet lysate as an alternative to replace fetal bovine serum for clinical-scale MSC expansion. Clonogenicity was determined in colony-forming units-fibroblast assays. MSC functions were tested in hematopoiesis support, vascular-like network formation and immune modulation potency assays. Results: MSCs could be propagated from UCB with and without fetal bovine serum. MSC propagation was effective in 46% of UCB samples. Once established, the proliferation kinetics of UCB MSCs did not differ significantly from that of bone marrow MSCs under optimized culture conditions, resulting in more than 50 population doublings after 15 weeks. A clinical quantity of 100 million MSCs with retained differentiation potential could be obtained from UCB MSCs within approximately 7 weeks. Ex vivo expansion of hematopoietic UCB-derived CD34+ cells as well as immune inhibition and vascular-like network formation could be shown for UCB MSCs propagated under both culture conditions. Conclusion: We demonstrate for the first time that human MSCs can be obtained and propagated to a clinical quantity from UCB in a completely bovine serum-free system. Surprisingly, our data argue against a generally superior proliferative potential of UCB MSCs. Functional data indicate the applicability of clinical-grade UCB MSCs propagated with human platelet lysate-conditioned medium for hematopoiesis support, immune regulation and vascular regeneration.

Diagnostic value of V?2-positive T-cell expansion in toxic shock syndrome

BACKGROUND

diagnostic dilemma in toxic shock syndrome (TSS) is that the results of microbiologic investigations are often not available immediately because of the need for incubation, or no obvious entry point can be found.

METHODS

We describe three patients with a clinical diagnosis of TSS in whom microbiologic tests were negative.

RESULTS

All patients had complicated courses with vasopressor-dependent shock, renal and respiratory failure, and disseminated intravascular coagulation for at least 1 week. In all three patients, diagnosis was considerably faster with the assessment of the expansion of T-cell-receptor Vbeta2-positive T cells (> 15%) than by Centers for Disease Control and Prevention (CDC) diagnosis, because of the complicated clinical picture or the delay caused by waiting for the results of microbiologic investigations.

CONCLUSIONS

Our results indicate that diagnostic procedures incorporating Vbeta2-positive T cells could be a useful tool for the diagnosis of TSS.

Immune cells mimic the morphology of endothelial progenitor colonies in vitro

Endothelial progenitor cells (EPC) are considered powerful biologic markers for vascular function and cardiovascular risk, predicting events and death from cardiovascular causes. Colony-forming units of endothelial progenitor cells (CFU-EC) are used to quantify EPC circulating in human peripheral blood. The mechanisms underlying colony formation and the nature of the contributing cells are not clear. We performed subtractive CFU-EC analyses to determine the impact of various blood cell types and kinetics of protein and gene expression during colony formation. We found that CFU-EC mainly comprise T cells and monocytes admixed with B cells and natural killer cells. The combination of purified T cells and monocytes formed CFU-EC structures. The lack of colonies after depletion or functional ablation of T cells or monocytes was contrasted with effective CFU-EC formation in the absence of CD34+ cells. Microarray analyses revealed activation of immune function-related biological processes without changes in angiogenesis-related processes during colony formation. In concordance with a regenerative function, soluble factors derived from CFU-EC cultures supported vascular network formation in vitro. Recognizing CFU-EC formation as the result of a functional cross between T cells and monocytes shifts expectations of vascular regenerative medicine. Our data support the move from a view of circulating EPC toward models that include a role for immune cells in vascular regeneration. Disclosure of potential conflicts of interest is found at the end of this article.

In search of a stem cell hierarchy in the human breast and its relevance to breast cancer evolution

By deliberate analogy with the well-established concept of hematopoiesis, the term "mammopoiesis" is occasionally used to describe the development of the different cellular lineages and functional units in the mammary gland. The use of this term signifies a strong bias towards the idea that tissue homeostasis during mammary development, pregnancy, lactation and involution is brought about by the action of somatic stem cells characterized by longevity and multipotency. The progenies hereof eventually differentiate into structurally and functionally well-defined ductal-lobular units. During the past two decades evidence of such a notion in the mouse has developed from being largely circumstantial based on non-clonal in vivo experiments to a quite elaborate characterization of individual candidate stem cells by a number of different properties. Within tumor biology this has led to a renaissance of the concept of tumors as caricatures of tissue renewal. Thus, recent molecular classification of breast cancer based on genome wide expression analysis operates with different subtypes with specific reference to the normal luminal epithelial and myoepithelial/basal lineages in the breast. Apparently some tumors are lineage restricted and others differentiate more broadly as if they have preserved some stem-like properties. This holds promise for the existence of a stem cell hierarchy, the understanding of which may prove to be instrumental in further dissecting the histogenesis of breast cancer evolution. Most attention has been devoted to the question of different cellular origins of cancer subtypes and different susceptibilities of possible stem cells to gain or loss of oncogenes and tumor suppressor genes, respectively. Invaluable progress has been made over the past two decades in culture technology not only in terms of population doubling and clonal growth, but also the availability of lineage specific markers, cell sorting, and three-dimensional functional assays for tissue specific morphogenesis. Transcriptional profiling of stem cell zones has unraveled a hitherto unknown preservation of signaling pathways for maintenance of stem cell properties across tissue boundaries and species. Somatic stem cells have therefore been narrowed down to specific anatomic locations not only in rapidly renewing tissues such as skin and skin derivatives, but also in tissues with slower turnover times, such as lung, kidney and prostate. It is therefore now possible to integrate this information in a search for similar cells within the breast. Even if cell turnover after birth is provided exclusively by dividing lineage-restricted cells, more information about the robustness of breast differentiation programs during tumor progression is still very much required. Complete knowledge of the primary cell of origin of breast cancer and the mechanisms that influence differentiation programs during tumor initiation, promotion and progression may be crucial for the development of novel non-toxic therapies that influence tumor cell behaviour. The scope of this review is to discuss reports that have begun to elucidate the topographic location, key cellular type and lineage fidelity in culture and xenograft models of candidate human breast stem cells and their differentiated progenies with particular emphasis on comparison with the differentiation programs of tumor subtypes.