Lucas G. Chase

PDGF, TGF-beta, and FGF signaling is important for differentiation and growth of mesenchymal stem cells (MSCs): transcriptional profiling can identify markers and signaling pathways important in differentiation of MSCs into adipogenic, chondrogenic, and osteogenic lineages.

We compared the transcriptomes of marrow-derived mesenchymal stem cells (MSCs) with differentiated adipocytes, osteocytes, and chondrocytes derived from these MSCs. Using global gene-expression profiling arrays to detect RNA transcripts, we have identified markers that are specific for MSCs and their differentiated progeny. Further, we have also identified pathways that MSCs use to differentiate into adipogenic, chondrogenic, and osteogenic lineages. We identified activin-mediated transforming growth factor (TGF)-beta signaling, platelet-derived growth factor (PDGF) signaling and fibroblast growth factor (FGF) signaling as the key pathways involved in MSC differentiation. The differentiation of MSCs into these lineages is affected when these pathways are perturbed by inhibitors of cell surface receptor function. Since growth and differentiation are tightly linked processes, we also examined the importance of these 3 pathways in MSC growth. These 3 pathways were necessary and sufficient for MSC growth. Inhibiting any of these pathways slowed MSC growth, whereas a combination of TGF-beta, PDGF, and beta-FGF was sufficient to grow MSCs in a serum-free medium up to 5 passages. Thus, this study illustrates it is possible to predict signaling pathways active in cellular differentiation and growth using microarray data and experimentally verify these predictions.

A novel serum-free medium for the expansion of human mesenchymal stem cells.

IntroductionHuman multipotent mesenchymal stem cell (MSC) therapies are being tested clinically for a variety of disorders, including Crohns disease, multiple sclerosis, graft-versus-host disease, type 1 diabetes, bone fractures, and cartilage defects. However, despite the remarkable clinical advancements in this field, most applications still use traditional culture media containing fetal bovine serum. The ill-defined and highly variable nature of traditional culture media remains a challenge, hampering both the basic and clinical human MSC research fields. To date, no reliable serum-free medium for human MSCs has been available.MethodsIn this study, we developed and tested a serum-free growth medium on human bone marrow-derived MSCs through the investigation of multiple parameters including primary cell isolation, multipassage expansion, mesoderm differentiation, cellular phenotype, and gene-expression analysis.ResultsSimilar to that achieved with traditional culture medium, human MSCs expanded in serum-free medium supplemented with recombinant human platelet-derived growth factor-BB (PDGF-BB), basic fibroblast growth factor (bFGF), and transforming growth factor (TGF)-β1 showed extensive propagation with retained phenotypic, differentiation, and colony-forming unit potential. To monitor global gene expression, the transcriptomes of bone marrow-derived MSCs expanded under serum-free and serum-containing conditions were compared, revealing similar expression profiles. In addition, the described serum-free culture medium supported the isolation of human MSCs from primary human marrow aspirate with continual propagation.ConclusionsAlthough the described serum-free MSC culture medium is not free of xenogeneic components, this medium provides a substitute for serum-containing medium for research applications, setting the stage for future clinical applications.

Toward a Clinical-Grade Expansion of Mesenchymal Stem Cells from Human Sources: A Microcarrier-Based Culture System Under Xeno-Free Conditions

The immunomodulatory properties of mesenchymal stem cells (MSCs) make them attractive therapeutic agents for a wide range of diseases. However, the highly demanding cell doses used in MSC clinical trials (up to millions of cells/kg patient) currently require labor intensive methods and incur high reagent costs. Moreover, the use of xenogenic (xeno) serum-containing media represents a risk of contamination and raises safety concerns. Bioreactor systems in combination with novel xeno-free medium formulations represent a viable alternative to reproducibly achieve a safe and reliable MSC doses relevant for cell therapy. The main goal of the present study was to develop a complete xeno-free microcarrier-based culture system for the efficient expansion of human MSC from two different sources, human bone marrow (BM), and adipose tissue. After 14 days of culture in spinner flasks, BM MSC reached a maximum cell density of (2.0±0.2)×10⁵ cells·mL⁻¹ (18±1-fold increase), whereas adipose tissue-derived stem cells expanded to (1.4±0.5)×10⁵ cells·mL⁻¹ (14±7-fold increase). After the expansion, MSC expressed the characteristic markers CD73, CD90, and CD105, whereas negative for CD80 and human leukocyte antigen (HLA)-DR. Expanded cells maintained the ability to differentiate robustly into osteoblast, adipocyte, and chondroblast lineages upon directed differentiation. These results demonstrated the feasibility of expanding human MSC in a scalable microcarrier-based stirred culture system under xeno-free conditions and represent an important step forward for the implementation of a Good Manufacturing Practices-compliant large-scale production system of MSC for cellular therapy.

Serum-free, xeno-free culture media maintain the proliferation rate and multipotentiality of adipose stem cells in vitro

BACKGROUND AIMS Human adipose stem cells (ASC) are an abundant, readily available population of multipotent progenitor cells that reside in adipose tissue. ASC have been shown to have therapeutic applicability in pre-clinical studies, but a standardized expansion method for clinical cell therapy has yet to be established. Isolated ASC are typically expanded in medium containing fetal bovine serum (FBS); however, sera and other culturing reagents of animal origin in clinical therapy pose numerous safety issues, including possible infections and severe immune reactions. METHODS To identify optimal conditions for ex vivo expansion of ASC, the effects of seven serum-free (SF) and xeno-free (XF) media were investigated with both FBS and allogeneic human serum (alloHS; as a control media). Surface marker expression, proliferation, morphology and differentiation analyzes were utilized for investigating the effects of media on ASC. RESULTS The proliferation and morphology analysis demonstrated significant differences between ASC cultured in SF/XF culture media compared with serum-containing culture media, with medium prototype StemPro MSC SFM XenoFree providing significantly higher proliferation rates than ASC cultured in media containing serum, while still maintaining the differentiation potential and surface marker expression profile characteristic of ASC. CONCLUSIONS Looking forward, fully defined XF media formulations will provide the means for the development and approval of safer clinical cell therapy treatments. However, to fully recognize the capacity of these XF culture media, further pre-clinical safety and efficacy studies must be performed.

Differentiating Human Multipotent Mesenchymal Stromal Cells Regulate microRNAs: Prediction of microRNA Regulation by PDGF During Osteogenesis

OBJECTIVE Human multipotent mesenchymal stromal cells (MSC) have the potential to differentiate into multiple cell types, although little is known about factors that control their fate. Differentiation-specific microRNAs may play a key role in stem cell self-renewal and differentiation. We propose that specific intracellular signaling pathways modulate gene expression during differentiation by regulating microRNA expression. MATERIALS AND METHODS Illumina mRNA and NCode microRNA expression analyses were performed on MSC and their differentiated progeny. A combination of bioinformatic prediction and pathway inhibition was used to identify microRNAs associated with platelet-derived growth factor (PDGF) signaling. RESULTS The pattern of microRNA expression in MSC is distinct from that in pluripotent stem cells, such as human embryonic stem cells. Specific populations of microRNAs are regulated in MSC during differentiation targeted toward specific cell types. Complementary mRNA expression analysis increases the pool of markers characteristic of MSC or differentiated progeny. To identify microRNA expression patterns affected by signaling pathways, we examined the PDGF pathway found to be regulated during osteogenesis by microarray studies. A set of microRNAs bioinformatically predicted to respond to PDGF signaling was experimentally confirmed by direct PDGF inhibition. CONCLUSION Our results demonstrate that a subset of microRNAs regulated during osteogenic differentiation of MSCs is responsive to perturbation of the PDGF pathway. This approach not only identifies characteristic classes of differentiation-specific mRNAs and microRNAs, but begins to link regulated molecules with specific cellular pathways.

Development and Characterization of a Clinically Compliant Xeno-Free Culture Medium in Good Manufacturing Practice for Human Multipotent Mesenchymal Stem Cells

Human multipotent mesenchymal stem cell (MSC) therapies are currently being tested in clinical trials for Crohns disease, multiple sclerosis, graft‐versus‐host disease, type 1 diabetes, bone fractures, cartilage damage, and cardiac diseases. Despite remarkable progress in clinical trials, most applications still use traditional culture media containing fetal bovine serum or serum‐free media that contain serum albumin, insulin, and transferrin. The ill‐defined and variable nature of traditional culture media remains a challenge and has created a need for better defined xeno‐free culture media to meet the regulatory and long‐term safety requirements for cell‐based therapies. We developed and tested a serum‐free and xeno‐free culture medium (SFM‐XF) using human bone marrow‐ and adipose‐derived MSCs by investigating primary cell isolation, multiple passage expansion, mesoderm differentiation, cellular phenotype, and gene expression analysis, which are critical for complying with translation to cell therapy. Human MSCs expanded in SFM‐XF showed continual propagation, with an expected phenotype and differentiation potential to adipogenic, chondrogenic, and osteogenic lineages similar to that of MSCs expanded in traditional serum‐containing culture medium (SCM). To monitor global gene expression, the transcriptomes of bone marrow‐derived MSCs expanded in SFM‐XF and SCM were compared, revealing relatively similar expression profiles. In addition, the SFM‐XF supported the isolation and propagation of human MSCs from primary human marrow aspirates, ensuring that these methods and reagents are compatible for translation to therapy. The SFM‐XF culture system allows better expansion and multipotentiality of MSCs and serves as a preferred alternative to serum‐containing media for the production of large scale, functionally competent MSCs for future clinical applications.

Mesenchymal stem cell assays and applications.

Research on mesenchymal stem cells (MSC) is progressing with increasing popularity. Currently there are a significant number of clinical trials exploring the use of MSCs for the treatment of various diseases including graft-versus-host disease, Crohns disease, myocardial infarction, stroke, bone defects, diabetes, and wound repair (www.-clinicaltrials.gov). At the same time, there are questions associated with MSCs in terms of their isolation, culture expansion, phenotype, multipotential differentiation, and transplantation efficiency. This chapter outlines the current status of the field and emphasizes the need for clearly defined protocols to better define the function and use of MSCs in cell therapy.

Mesenchymal stem cell therapy

Scaling-up Ex-vivo Expansion of Mesenchymal Stem/Stromal Cells for Cellular Therapies.- Mesenchymal Stromal Cell Mechanisms of Immunomodulation and Homing.- Mesenchymal Stem Cell Exosomes: The Future MSC-based Therapy?.- The Biology of Mesenchymal Stem Cells in Health and Disease and its Relevance to MSC-based Cell Delivery Therapies.- Pulmonary Clinical Applications for Mesenchymal Stem Cells.- Stem Cell Therapy for Bone Disorders.- Mesenchymal Stem Cell Therapies for Bone and Tendon Conditions.- Mesenchymal Stromal Cells (MSC) and the Repair of Cartilage Tissue.- Mesenchymal Stem Cells and Haematopoietic Stem Cell Culture.- Mesenchymal Stem Cells for Treatment and Prevention of Graft-Versus-Host Disease and Graft Failure after Hematopoietic Stem Cell Transplantation and Future Challenges.- Mesenchymal Stromal Cell Therapy in Crohns Disease.- Application of Mesenychymal Stem Cells in Amyotrophic Lateral Sclerosis.- Mesenchymal Stem Cell Therapy for Heart Disease.- Advances in Lentivector-based Cell Therapy with Mesenchymal Stem Cells.- Genetically Engineered Mesenchymal Stem Cells for Cell and Gene Therapy.- Optimal Tissue Sources of Mesenchymal Stromal Cells for Clinical Trials.- Regulatory Considerations Applicable to Manufacturing of Human Placenta-derived Mesenchymal Stromal Cells (MSC) Used in Clinical Trials in Australia and Comparison to USA and European Regulatory Frameworks.- Mesenchymal Stem Cell Therapy for Peripheral Vascular Diseases.- Mesenchymal Stromal Cells in the Clinic: What do the clinical trials say?.

Characterization of serotonin 5-hydroxytryptamine-1A receptor activation using a phospho-extracellular-signal regulated kinase 2 sensor

The activation of G-protein-coupled receptors (GPCRs) can result in the stimulation of numerous signaling networks that extend beyond canonical secondary messenger-dependent pathways. It is well-established that many of these diverse networks converge on the MAPK pathway, resulting in the activation of extracellular-signal regulated kinase 1/2 (ERK). Since the link between GPCRs and ERK can be modulated via both G-protein-dependent and -independent mechanisms, measurement of ERK phosphorylation may serve as an ideal surrogate for GPCR activation. We have combined BacMam-mediated gene delivery of the GFP-ERK2 with a time-resolved Foerster resonance energy transfer (TR-FRET) immunoassay for the measurement of intracellular phospho-ERK2 levels. Together these technologies enable a flexible platform for measuring GPCR and MAPK activation in the cell line of interest. This technology has been applied to the measurement of activation of the serotonin 5-hydroxytryptamine-1A (5-HT(1A)) receptor expressed in CHO-K1 cells. In addition to demonstrating the flexibility of this assay platform, we provide the first reported profile for 5-HT(1A) receptor-mediated ERK activation using a panel of known Parkinsons disease drugs. Our results demonstrate the value of using ERK activation as a downstream sensor for GPCR function, providing an attractive complement to upstream endpoints such as ligand occupancy and binding of GTPgammaS.