Bjarke Follin

Comparison of clinical grade human platelet lysates for cultivation of mesenchymal stromal cells from bone marrow and adipose tissue

Abstract Background: The utility of mesenchymal stromal cells (MSCs) in therapeutic applications for regenerative medicine has gained much attention. Clinical translation of MSC-based approaches requires in vitro culture-expansion to achieve a sufficient number of cells. The ideal cell culture medium should be devoid of any animal derived components. We have evaluated whether human Platelet Lysate (hPL) could be an attractive alternative to animal supplements. Methods: MSCs from bone marrow (BMSCs) and adipose tissue-derived stromal cells (ASCs) obtained from three donors were culture expanded in three different commercially available hPL fulfilling good manufacturing practice criteria for clinical use. BMSCs and ASCs cultured in Minimum Essential Medium Eagle-alpha supplemented with 5% PLT-Max (Mill Creek), Stemulate™ PL-S and Stemulate™ PL-SP (COOK General Biotechnology) were compared to standard culture conditions with 10% fetal bovine serum (FBS). Cell morphology, proliferation, phenotype, genomic stability, and differentiation potential were analyzed. Results: Regardless of manufacturer, BMSCs and ASCs cultured in hPL media showed a significant increase in proliferation capacity compared to FBS medium. In general, the immunophenotype of both BMSCs and ASCs fulfilled International Society for Cellular Therapy (ISCT) criteria after hPL media expansion. Comparative genomic hybridization measurements demonstrated no unbalanced chromosomal rearrangements for BMSCs or ASCs cultured in hPL media or FBS medium. The BMSCs and ASCs could differentiate into osteogenic, adipogenic, or chondrogenic lineages in all four culture conditions. Conclusion: All three clinically approved commercial human platelet lysates accelerated proliferation of BMSCs and ASCs and the cells meet the ISCT mesenchymal phenotypic requirements without exhibiting chromosomal aberrations.

Identical effects of VEGF and serum-deprivation on phenotype and function of adipose-derived stromal cells from healthy donors and patients with ischemic heart disease

BackgroundAdipose-derived stromal cells (ASCs) stimulated with vascular endothelial growth factor (VEGF) and serum-deprived, are applied in the first in-man double-blind placebo-controlled MyStromalCell Trial, as a novel therapeutic option for treatment of ischemic heart disease (IHD). This in vitro study explored the effect of VEGF and serum deprivation on endothelial differentiation capacity of ASCs from healthy donors and IHD patients.MethodsASCs stimulated with rhVEGFA165 in serum-deprived medium for one to three weeks were compared with ASCs in serum-deprived (2% fetal bovine serum) or complete medium (10% fetal bovine serum). Expression of VEGF receptors, endothelial and stem cell markers was measured using qPCR, flow cytometry and immunocytochemistry. In vitro tube formation and proliferation was also measured.ResultsASCs from VEGF-stimulated and serum-deprived medium significantly increased transcription of transcription factor FOXF1, endothelial marker vWF and receptor VEGFR1 compared with ASCs from complete medium. ASCs maintained stem cell characteristics in all conditions. Tube formation of ASCs occurred in VEGF-stimulated and serum-deprived medium. The only difference between healthy and patient ASCs was a variation in proliferation rate.ConclusionsASCs from IHD patients and healthy donors proved equally inclined to differentiate in endothelial direction by serum-deprivation, however with no visible additive effect of VEGF stimulation. The treatment did not result in complete endothelial differentiation, but priming towards endothelial lineage.

Human adipose-derived stromal cells in a clinically applicable injectable alginate hydrogel: Phenotypic and immunomodulatory evaluation

BACKGROUND AIMS Clinical trials have documented beneficial effects of mesenchymal stromal cells from bone marrow and adipose tissue (ASCs) as treatment in patients with ischemic heart disease. However, retention of transplanted cells is poor. One potential way to increase cell retention is to inject the cells in an in situ cross-linked alginate hydrogel. METHODS ASCs from abdominal human tissue were embedded in alginate hydrogel and alginate hydrogel modified with Arg-Gly-Asp motifs (RGD-alginate) and cultured for 1 week. Cell viability, phenotype, immunogenicity and paracrine activity were determined by confocal microscopy, dendritic cell co-culture, flow cytometry, reverse transcriptase quantitative polymerase chain reaction, Luminex multiplex, and lymphocyte proliferation experiments. RESULTS ASCs performed equally well in alginate and RGD-alginate. After 1 week of alginate culture, cell viability was >93%. Mesenchymal markers CD90 and CD29 were reduced compared with International Society for Cellular Therapy criteria. Cells sedimented from the alginates during cultivation regained the typical level of these markers, and trilineage differentiation was performed by standard protocols. Hepatocyte growth factor mRNA was increased in ASCs cultivated in alginates compared with monolayer controls. Alginates and alginates containing ASCs did not induce dendritic cell maturation. ASCs in alginate responded like controls to interferon-gamma stimulation (licensing), and alginate culture increased the ability of ASCs to inhibit lymphocyte proliferation. DISCUSSION ASCs remain viable in alginates; they transiently change phenotype in alginate hydrogel but regain the phenotype of monolayer controls upon release. Cells maintain their paracrine potential while in alginates; the combination of ASCs and alginate is non-immunogenic and, in fact, immunosuppressive.

Identification of a common reference gene pair for qPCR in human mesenchymal stromal cells from different tissue sources treated with VEGF

BackgroundHuman mesenchymal stromal cells from the bone marrow (BMSCs) are widely used as experimental regenerative treatment of ischemic heart disease, and the first clinical trials using adipose-derived stromal cells (ASCs) are currently being conducted. Regenerative mechanisms of BMSCs and ASCs are manifold and in vitro pretreatment of the cells with growth factors has been applied to potentially enhance these properties. When characterizing the transcriptional activity of these cellular mechanisms in vitro it is important to consider the effect of the growth factor treatment on reference genes (RGs) for the normalization of qPCR data.ResultsBMSCs and ASCs were stimulated with vascular endothelial growth factor A-165 (VEGF) for one week, and compared with un-stimulated cells from the same donor. The stability of nine RGs through VEGF treatment as well as the donor variation was assessed using the GenEx software with the subprograms geNorm and Normfinder.The procedure of stepwise elimination was validated by poor performance of eliminated RGs in a normalization experiment using vWF as target gene. Normfinder found the TATA box binding protein (TBP) to be the most stable single RG for both BMSCs and ASCs. The optimal number of RGs for ASCs was two, and the lowest variance for vWF normalization was found using TBP and YWHAZ. For BMSCs, the optimal number of RGs was four, while the two-RG combination producing the most similar results was TBP and YWHAZ.ConclusionsA common reference gene, TBP, was found to be the most stable standalone gene, while TBP and YWHAZ were found to be the best two-RG combination for qPCR analyses for both BMSCs and ASCs through the VEGF stimulation. The presented stepwise elimination procedure was validated, while we found the final normalization experiment to be essential.

Cryopreserved Off‐the‐Shelf Allogeneic Adipose‐Derived Stromal Cells for Therapy in Patients with Ischemic Heart Disease and Heart Failure—A Safety Study

The present first‐in‐human clinical trial evaluated the safety and feasibility of a newly developed and cryopreserved Cardiology Stem Cell Centre adipose‐derived stromal cell (CSCC_ASC) product from healthy donors for intramyocardial injection in ten patients with ischemic heart disease and ischemic heart failure (IHF). Batches of CSCC_ASC were isolated from three healthy donors by liposuction from abdominal adipose tissue. Adipose mesenchymal stromal cells were culture expanded in bioreactors without the use of animal constituents, cryopreserved, and stored in vials in nitrogen dry‐storage containers until use.

Senescence and quiescence in adipose-derived stromal cells: Effects of human platelet lysate, fetal bovine serum and hypoxia.

BACKGROUND AIMS Adipose-derived stromal cells (ASCs) are attractive sources for cell-based therapies. The hypoxic niche of ASCs in vivo implies that cells will benefit from hypoxia during in vitro expansion. Human platelet lysate (hPL) enhances ASC proliferation rates, compared with fetal bovine serum (FBS) at normoxia. However, the low proliferation rates of FBS-expanded ASCs could be signs of senescence or quiescence. We aimed to determine the effects of hypoxia and hPL on the expansion of ASCs and whether FBS-expanded ASCs are senescent or quiescent. METHODS ASCs expanded in FBS or hPL at normoxia or hypoxia until passage 7 (P7), or in FBS until P5 followed by culture in hPL until P7, were evaluated by proliferation rates, cell cycle analyses, gene expression and β-galactosidase activity. RESULTS hPL at normoxia and hypoxia enhanced proliferation rates and expression of cyclins, and decreased G0/G1 fractions and expression of p21 and p27, compared with FBS. The shift from FBS to hPL enhanced cyclin levels, decreased p21 and p27 levels and tended to decrease G0/G1 fractions. CONCLUSION Hypoxia does not add to the effect of hPL during ASC expansion with regard to proliferation, cell cycle regulation and expression of cyclins, p21 and p27. hPL rejuvenates FBS-expanded ASCs with regard to cell cycle regulation and expression of cyclins, p21 and p27. This indicates a reversible arrest. Therefore, we conclude that ASCs expanded until P7 are not senescent regardless of culture conditions.

Angiogenesis PET Tracer Uptake (68Ga-NODAGA-E[(cRGDyK)]2) in Induced Myocardial Infarction in Minipigs

Angiogenesis is part of the healing process following an ischemic injury and is vital for the post-ischemic repair of the myocardium. Therefore, it is of particular interest to be able to noninvasively monitor angiogenesis. This might, not only permit risk stratification of patients following myocardial infarction, but could also facilitate development and improvement of new therapies directed towards stimulation of the angiogenic response. During angiogenesis endothelial cells must adhere to one another to form new microvessels. αvβ3 integrin has been found to be highly expressed in activated endothelial cells and has been identified as a critical modulator of angiogenesis. 68Ga-NODAGA-E[c(RGDyK)]2 (RGD) has recently been developed by us as an angiogenesis positron-emission-tomography (PET) ligand targeted towards αvβ3 integrin. In the present study, we induced myocardial infarction in Göttingen minipigs. Successful infarction was documented by 82Rubidium-dipyridamole stress PET and computed tomography. RGD uptake was demonstrated in the infarcted myocardium one week and one month after induction of infarction by RGD-PET. In conclusion, we demonstrated angiogenesis by noninvasive imaging using RGD-PET in minipigs hearts, which resemble human hearts. The perspectives are very intriguing and might permit the evaluation of new treatment strategies targeted towards increasing the angiogenetic response, e.g., stem-cell treatment.

Development of large-scale manufacturing of adipose-derived stromal cells for clinical applications using bioreactors and human platelet lysate

Abstract In vitro expanded adipose-derived stromal cells (ASCs) are a useful resource for tissue regeneration. Translation of small-scale autologous cell production into a large-scale, allogeneic production process for clinical applications necessitates well-chosen raw materials and cell culture platform. We compare the use of clinical-grade human platelet lysate (hPL) and fetal bovine serum (FBS) as growth supplements for ASC expansion in the automated, closed hollow fibre quantum cell expansion system (bioreactor). Stromal vascular fractions were isolated from human subcutaneous abdominal fat. In average, 95 × 106 cells were suspended in 10% FBS or 5% hPL medium, and loaded into a bioreactor coated with cryoprecipitate. ASCs (P0) were harvested, and 30 × 106 ASCs were reloaded for continued expansion (P1). Feeding rate and time of harvest was guided by metabolic monitoring. Viability, sterility, purity, differentiation capacity, and genomic stability of ASCs P1 were determined. Cultivation of SVF in hPL medium for in average nine days, yielded 546 × 106 ASCs compared to 111 × 106 ASCs, after 17 days in FBS medium. ASCs P1 yields were in average 605 × 106 ASCs (PD [population doublings]: 4.65) after six days in hPL medium, compared to 119 × 106 ASCs (PD: 2.45) in FBS medium, after 21 days. ASCs fulfilled ISCT criteria and demonstrated genomic stability and sterility. The use of hPL as a growth supplement for ASCs expansion in the quantum cell expansion system provides an efficient expansion process compared to the use of FBS, while maintaining cell quality appropriate for clinical use. The described process is an obvious choice for manufacturing of large-scale allogeneic ASC products.

Angiogenesis PET Tracer Uptake (68Ga-NODAGA-E[(cRGDyK)]2) in Induced Myocardial Infarction and Stromal Cell Treatment in Minipigs

Angiogenesis is considered integral to the reparative process after ischemic injury. The αvβ3 integrin is a critical modulator of angiogenesis and highly expressed in activated endothelial cells. 68Ga-NODAGA-E[(cRGDyK)]2 (RGD) is a positron-emission-tomography (PET) ligand targeted towards αvβ3 integrin. The aim was to present data for the uptake of RGD and correlate it with histology and to further illustrate the differences in angiogenesis due to porcine adipose-derived mesenchymal stromal cell (pASC) or saline treatment in minipigs after induction of myocardial infarction (MI). Three minipigs were treated with direct intra-myocardial injection of pASCs and two minipigs with saline. MI was confirmed by 82Rubidium (82Rb) dipyridamole stress PET. Mean Standardized Uptake Values (SUVmean) of RGD were higher in the infarct compared to non-infarct area one week and one month after MI in both pASC-treated (SUVmean: 1.23 vs. 0.88 and 1.02 vs. 0.86, p < 0.05 for both) and non-pASC-treated minipigs (SUVmean: 1.44 vs. 1.07 and 1.26 vs. 1.04, p < 0.05 for both). However, there was no difference in RGD uptake, ejection fractions, coronary flow reserves or capillary density in histology between the two groups. In summary, indications of angiogenesis were present in the infarcted myocardium. However, no differences between pASC-treated and non-pASC-treated minipigs could be demonstrated.