An In Vitro Potency Assay for Monitoring the Immunomodulatory Potential of Stromal Cell-Derived Extracellular Vesicles.

The regenerative and immunomodulatory activity of mesenchymal stromal cells (MSCs) is partially mediated by secreted vesicular factors. Extracellular vesicles (EVs) exocytosed by MSCs are gaining increased attention as prospective non-cellular therapeutics for a variety of diseases. However, the lack of suitable in vitro assays to monitor the therapeutic potential of EVs currently restricts their application in clinical studies. We have evaluated a dual in vitro immunomodulation potency assay that reproducibly reports the inhibitory effect of MSCs on induced T-cell proliferation and the alloantigen-driven mixed leukocyte reaction of pooled peripheral blood mononuclear cells in a dose-dependent manner. Phytohemagglutinin-stimulated T-cell proliferation was inhibited by MSC-derived EVs in a dose-dependent manner comparable to MSCs. In contrast, inhibition of alloantigen-driven mixed leukocyte reaction was only observed for MSCs, but not for EVs. Our results support the application of a cell-based in vitro potency assay for reproducibly determining the immunomodulatory potential of EVs. Validation of this assay can help establish reliable release criteria for EVs for future clinical studies.

A Good Manufacturing Practice-grade standard protocol for exclusively human mesenchymal stromal cell-derived extracellular vesicles.

BACKGROUND AIMS: Extracellular vesicles (EVs) released by mesenchymal stromal cells (MSCs) may contribute to biological processes such as tissue regeneration, immunomodulation and neuroprotection. Evaluation of their therapeutic potential and application in future clinical trials demands thorough characterization of EV content and production under defined medium conditions, devoid of xenogenic substances and serum-derived vesicles. Addressing the apparent need for such a growth medium, we have developed a medium formulation based on pooled human platelet lysate (pHPL), free from animal-derived xenogenic additives and depleted of EVs. METHODS: Depletion of EVs from complete growth medium was achieved by centrifugation at 120 000 g for 3 h, which reduced RNA-containing pHPL EVs to below the detection limit. RESULTS: Bone marrow (BM)-derived MSCs propagated in this medium retained the characteristic surface marker expression, cell morphology, viability and in vitro osteogenic and adipogenic differentiation potential. The proliferation rate was not significantly affected after 48 h but was decreased by 13% after 96 h. EVs collected from BM-MSCs cultured in EV-depleted medium revealed a similar RNA pattern as EVs generated in standard pHPL EV-containing medium but displayed a more clearly defined pattern of proteins characteristic for EVs. Reduction of pHPL content from 10% to 2% or serum-/pHPL-free conditions strongly altered MSC characteristics and RNA content of released EV. CONCLUSIONS: The 10% pHPL-based EV-depleted medium is appropriate for purification of exclusively human MSC-derived EVs. With this Good Manufacturing Practice-grade protocol, characterization and establishment of protein and RNA profiles from MSC-derived EVs can now be achieved to identify active components in therapeutic EVs for future clinical application.

An alternative mini buffy coat preparation method for adult patients with extracorporeal photopheresis contraindications.

BACKGROUND: Extracorporeal photopheresis (ECP) is an important cell-based therapy for various diseases but is limited to patients eligible for apheresis. We developed an alternative mini buffy coat (BC) preparation method using the Spectra Optia® apheresis system and compared its efficacy of white blood cell (WBC) recovery with the standard mini BC preparation method already established for pediatric patients. METHODS: Whole blood (450 ± 45 mL) samples were collected from 30 randomly selected healthy volunteer blood donors and divided into two groups. In the first group, WBCs were separated with a fully automated separator device (Compomat G4® ). In the second group, BCs were separated with the bone marrow processing program of the Spectra Optia apheresis system. RESULTS: There were no significant differences in total leukocyte counts per product between the two groups. In contrast, lymphocyte counts per product were significantly higher (P < 0.001) in BCs separated from apheresis. CONCLUSION: Our novel technique resulted in similar WBC yields but higher lymphocyte yields than the standard mini BC preparation method. This method can serve as an alternative to WBC collection in conventional ECP for adult patients with apheresis contraindications. J. Clin. Apheresis 32:12-15, 2017. © 2016 Wiley Periodicals, Inc.

Mechanical fibrinogen-depletion supports heparin-free mesenchymal stem cell propagation in human platelet lysate.

BACKGROUND: Pooled human platelet lysate (pHPL) is an efficient alternative to xenogenic supplements for ex vivo expansion of mesenchymal stem cells (MSCs) in clinical studies. Currently, porcine heparin is used in pHPL-supplemented medium to prevent clotting due to plasmatic coagulation factors. We therefore searched for an efficient and reproducible medium preparation method that avoids clot formation while omitting animal-derived heparin. METHODS: We established a protocol to deplete fibrinogen by clotting of pHPL in medium, subsequent mechanical hydrogel disruption and removal of the fibrin pellet. After primary culture, bone-marrow and umbilical cord derived MSCs were tested for surface markers by flow cytometry and for trilineage differentiation capacity. Proliferation and clonogenicity were analyzed for three passages. RESULTS: The proposed clotting procedure reduced fibrinogen more than 1000-fold, while a volume recovery of 99.5 % was obtained. All MSC types were propagated in standard and fibrinogen-depleted medium. Flow cytometric phenotype profiles and adipogenic, osteogenic and chondrogenic differentiation potential in vitro were independent of MSC-source or medium type. Enhanced proliferation of MSCs was observed in the absence of fibrinogen but presence of heparin compared to standard medium. Interestingly, this proliferative response to heparin was not detected after an initial contact with fibrinogen during the isolation procedure. CONCLUSIONS: Here, we present an efficient, reproducible and economical method in compliance to good manufacturing practice for the preparation of MSC media avoiding xenogenic components and suitable for clinical studies.

Iron depletion with a novel apheresis system in patients with hemochromatosis.

BACKGROUND: Phlebotomy represents the standard treatment option for iron overload in hemochromatosis (HC). Recently, red blood cell (RBC) apheresis has increasingly been used to remove iron. In this study we evaluated the depletion program of the newly developed Spectra Optia device. STUDY DESIGN AND METHODS: Adult male patients (n = 11) with HC were RBC depleted with the Spectra Optia device (Terumo BCT). In total, 24 procedures were performed. A volume of 300 to 550 mL of RBCs was withdrawn per single treatment. RESULTS: No significant adverse events were recorded. A median blood volume of 857.3 ± 23.3 mL was processed. The median procedure time was 12.0 ± 0.4 minutes. The mean reduction of Hct value in each procedure was approximately 6% (Hct pre 42.6 ± 0.5% vs. Hct post 36.6 ± 0.6%) and iron removed per procedure was 405.2 ± 23.3 mg. CONCLUSION: The Spectra Optia device proved to be highly efficient in depleting RBCs in HC patients and allows for short procedure time. The Optia device can be safely used in this clinical setting. We recommend its use in case of severe iron overload if rapid iron depletion needs to be achieved and in case of cardiac compromise due to less blood volume removed.

Expression of the non-gastric H+/K+ ATPase ATP12A in normal and pathological human prostate tissue.

Altered cellular proton handling and cell volume regulation are hallmarks of tumorigenesis. To investigate a possible involvement of the non-gastric H(+)/K(+) ATPase ATP12A (ATP1AL1) in prostate cancer, we performed immunohistochemistry in formalin-fixed, paraffin-embedded histological sections from benign and malignant human prostate lesions. Normal prostate tissue displayed a membrane-bound ATP12A staining with focal accumulated pattern, whereas in the benign prostate hyperplasia (BPH) and cancerous prostate tissue (tumor grade I-III) the protein appears to be displaced in the luminal cells of the glandular epithelium. Hence, the expression pattern of ATP12A is markedly altered in BPH and prostate cancer. To test for altered gene expression of ATP12A we performed quantitative reverse transcriptase PCR (QRT-PCR) in normal (tumor-free) prostate tissue, BPH and tumor stages I-III using a prostate cancer cDNA array. However, no significantly different expression levels could be detected in the various disease states compared to normal tissue, which contrasts the findings from immunohistochemistry and points to the possibility of altered post-translational processing and/or sorting of the protein. We further show that ATP12A mRNA is expressed at different levels in PC-3 and LNCaP prostate cancer cells, with a significant ~26-fold higher expression in the latter cell type. Protein expression in these tumor cell lines was verified by Western blot.