Optimization of the use of a pharmaceutical grade xeno-free medium for in vitro expansion of human mesenchymal stem/stromal cells

Three-Dimensional Spheroid Culture of Human Mesenchymal Stem Cells: Offering Therapeutic Advantages and In Vitro Glimpses of the In Vivo State

As invaluable as the standard 2-dimensional (2D) monolayer in vitro cell culture system has been, there is increasing evidence that 3-dimensional (3D) non-adherent conditions are more relevant to the in vivo condition. While one of the criteria for human mesenchymal stem cells (MSCs) has been in vitro plastic adherence, such 2D culture conditions are not representative of in vivo cell-cell and cell-extracellular matrix (ECM) interactions, which may be especially important for this progenitor/stem cell of skeletal and connective tissues. The 3D spheroid, a multicellular aggregate formed under non-adherent 3D in vitro conditions, may be particularly suited as an in vitro method to better understand MSC physiological processes, since expression of ECM and other adhesion proteins are upregulated in such a cell culture system. First used in embryonic stem cell in vitro culture to recapitulate in vivo developmental processes, 3D spheroid culture has grown in popularity as an in vitro method to mimic the 3-dimensionality of the native niche for MSCs within tissues/organs. In this review, we discuss the relevance of the 3D spheroid culture for understanding MSC biology, summarize the biological outcomes reported in the literature based on such this culture condition, as well as contemplate limitations and future considerations in this rapidly evolving and exciting area.

Producing vesicle-free cell culture additive for human cells extracellular vesicles manufacturing

A new paradigm has emerged recently, which consists in shifting from cell therapy to a more flexible acellular "extracellular vesicle (EV) therapy" approach, thereby opening a new and promising field in nanomedicine. Important technical limitations have still to be addressed for the large-scale production of clinical-grade EV. Cells are cultured in media supplemented with human platelet lysate (hPL) (xenogenic-free) or GMP-grade fetal calf serum (FCS). However, these additives contain high amounts of EV that cannot be separated from cell-secreted -EV. Therefore, cells are generally maintained in additive-free medium during the EV secretion phase, however this can substantially limit their survival. In the present work, we developed a method to prepare vesicle-free hPL (EV-free hPL) or vesicle-free FCS (EV-free FCS) using tangential flow filtration (TFF). We show a very efficient EV depletion (>98%) for both pure hPL and FCS, with a highly conserved protein content. Culture medium containing our EV-free additives supported the survival of human bone marrow MSC (BM-MSC). MSC could survive at least 216 h, their conditioned medium being collected and changed every 72 h. Both the cell survival and the cumulative EV production were substantially higher than in the starving conditions classically used for EV production. In EV-free hPL containing medium, we show that purified EV kept their morphologic and molecular characteristics throughout the production. Finally, we tested our additives with 3 other cell types, human primary Endothelial Colony Forming Cells (ECFC) and two non-adherent human cell lines, Jurkat and THP-1. We confirmed that both EV-free hPL and FCS were able to maintain cell survival and EV production for at least 216 h. Our method provides therefore a new option to help producing large amounts of EV from virtually any mammalian cells, particularly those that do not tolerate starvation. This method can apply to any animal serum for research and development purpose. Moreover, EV-free hPL is clinical-grade compatible and allows preparing xenobiotic-free media for massive therapeutic EV production in both 2D (cell plates) and 3D (bioreactor) setting.

Tri-Lineage Differentiation Potential of Osteosarcoma Cell Lines and Human Bone Marrow Stromal Cells from Different Anatomical Locations

The bone cancer osteosarcoma, found mainly in adolescents, routinely forms around the growth plate/metaphysis of long bones. Bone marrow composition changes with age, shifting from a more hematopoietic to an adipocyte-rich tissue. This conversion occurs in the metaphysis during adolescence, implicating a link between bone marrow conversion and osteosarcoma initiation. To assess this, the tri-lineage differentiation potential of human bone marrow stromal cells (HBMSCs) isolated from the femoral diaphysis/metaphysis (FD) and epiphysis (FE) was characterized and compared to two osteosarcoma cell lines, Saos-2 and MG63. Compared to FE-cells, FD-cells showed an increase in tri-lineage differentiation. Additionally, differences were found between the Saos-2 cells exhibiting higher levels of osteogenic differentiation, lower adipogenic differentiation, and a more developed chondrogenic phenotype than MG63, with the Saos-2 being more comparable to FD-derived HBMSCs. The differences found between the FD and FE derived cells are consistent with the FD region containing more hematopoietic tissue compared to the FE. This may be related to the similarities between FD-derived cells and Saos-2 cells during osteogenic and chondrogenic differentiation. These studies reveal distinct differences in the tri-lineage differentiations of 'hematopoietic' and 'adipocyte rich' bone marrow, which correlate with specific characteristics of the two osteosarcoma cell lines.

A Three-Dimensional Printed Polycaprolactone–Biphasic-Calcium-Phosphate Scaffold Combined with Adipose-Derived Stem Cells Cultured in Xenogeneic Serum-Free Media for the Treatment of Bone Defects

The efficacy of a three-dimensional printed polycaprolactone–biphasic-calcium-phosphate scaffold (PCL–BCP TDP scaffold) seeded with adipose-derived stem cells (ADSCs), which were cultured in xenogeneic serum-free media (XSFM) to enhance bone formation, was assessed in vitro and in animal models. The ADSCs were isolated from the buccal fat tissue of six patients using enzymatic digestion and the plastic adherence method. The proliferation and osteogenic differentiation of the cells cultured in XSFM when seeded on the scaffolds were assessed and compared with those of cells cultured in a medium containing fetal bovine serum (FBS). The cell–scaffold constructs were cultured in XSFM and were implanted into calvarial defects in thirty-six Wistar rats to assess new bone regeneration. The proliferation and osteogenic differentiation of the cells in the XSFM medium were notably better than that of the cells in the FBS medium. However, the efficacy of the constructs in enhancing new bone formation in the calvarial defects of rats was not statistically different to that achieved using the scaffolds alone. In conclusion, the PCL–BCP TDP scaffolds were biocompatible and suitable for use as an osteoconductive framework. The XSFM medium could support the proliferation and differentiation of ADSCs in vitro. However, the cell–scaffold constructs had no benefit in the enhancement of new bone formation in animal models.

Influences of Xeno-Free Media on Mesenchymal Stem Cell Expansion for Clinical Application

Mesenchymal stem/stromal cells (MSCs) are multipotent somatic stem/progenitor cells that can be isolated from various tissues and have attracted increasing attention from the scientific community. This is due to MSCs showing great potential for incurable disease treatment, and most applications of MSCs involve tissue degeneration and treatment of immune- and inflammation-mediated diseases. Conventional MSC cultures contain fetal bovine serum (FBS), which is a common supplement for cell development but is also a risk factor for exposure to animal-derived pathogens. To avoid the risks resulting from the xenogeneic origin and animal-derived pathogens of FBS, xeno-free media have been developed and commercialized to satisfy MSC expansion demands for human clinical applications. This review summarized and provided an overview of xeno-free media that are currently used for MSC expansion. Additionally, we discussed the influences of different xeno-free media on MSC biology with particular regard to cell morphology, surface marker expression, proliferation, differentiation and immunomodulation. The xeno-free media can be serum-free and xeno-free media or media supplemented with some human-originating substances, such as human serum, human platelet lysates, human umbilical cord serum/plasma, or human plasma-derived supplements for cell culture medium. These media have capacity to maintain a spindle-shaped morphology, the expression of typical surface markers, and the capacity of multipotent differentiation and immunomodulation of MSCs. Xeno-free media showed potential for safe use for human clinical treatment. However, the influences of these xeno-free media on MSCs are various and any xeno-free medium should be examined prior to being used for MSC cultures.

The Manufacture of GMP-Grade Bone Marrow Stromal Cells with Validated In Vivo Bone-Forming Potential in an Orthopedic Clinical Center in Brazil

In vitro-expanded bone marrow stromal cells (BMSCs) have long been proposed for the treatment of complex bone-related injuries because of their inherent potential to differentiate into multiple skeletal cell types, modulate inflammatory responses, and support angiogenesis. Although a wide variety of methods have been used to expand BMSCs on a large scale by using good manufacturing practice (GMP), little attention has been paid to whether the expansion procedures indeed allow the maintenance of critical cell characteristics and potency, which are crucial for therapeutic effectiveness. Here, we described standard procedures adopted in our facility for the manufacture of clinical-grade BMSC products with a preserved capacity to generate bone in vivo in compliance with the Brazilian regulatory guidelines for cells intended for use in humans. Bone marrow samples were obtained from trabecular bone. After cell isolation in standard monolayer flasks, BMSC expansion was subsequently performed in two cycles, in 2- and 10-layer cell factories, respectively. The average cell yield per cell factory at passage 1 was of 21.93 ± 12.81 × 106 cells, while at passage 2, it was of 83.05 ± 114.72 × 106 cells. All final cellular products were free from contamination with aerobic/anaerobic pathogens, mycoplasma, and bacterial endotoxins. The expanded BMSCs expressed CD73, CD90, CD105, and CD146 and were able to differentiate into osteogenic, chondrogenic, and adipogenic lineages in vitro. Most importantly, nine out of 10 of the cell products formed bone when transplanted in vivo. These validated procedures will serve as the basis for in-house BMSC manufacturing for use in clinical applications in our center.

In Vitro Expansion and Characterization of Mesenchymal Stromal Cells from Peritoneal Dialysis Effluent in a Human Protein Medium

The therapeutic potential of mesenchymal stromal cells (MSCs) from various tissue origins have extensively been explored in both experimental and clinical studies, and peritoneal dialysis effluent-derived MSC (pMSC) may be an easily obtainable MSC source for clinical applications. In this study, we expanded and characterized the pMSCs after expansion in a human protein culture medium. The pMSCs were expanded in plastic dishes with the human protein medium. MSC marker expression was examined by flow cytometry. Spherical formation was tested by hanging drop method, and osteogenic, adipogenic, and chondrogenic differentiation capacities were confirmed by positive staining with Alizarin red, Oil red O, and Alcian blue, respectively. Here, we showed that after four passages of culturing in plastic dishes, pMSCs in the human protein medium displayed a homogeneous pattern of classical MSC markers (positive: CD29, CD44, CD73, CD90, and CD166; negative: CD14, CD34, CD45, CD79a, CD105, CD146, CD271, HLA-DR, SSEA-4, and Stro-1), while in the standard medium, pMSCs from some donors were CD45 or HLA-DR positive. For nonclassical MSC markers, pMSCs were CD200 positive from all the donors, negative for CD163, CD271, CD36, and CD248, and either positive or negative for CD274 and CD140b. Further, pMSCs from the human protein medium had the spherical formation capacity and multipotent differentiation capacity in vitro. In conclusion, upon expansion in a human protein medium, pMSCs showed a differential MSC marker expression profile from those of bone marrow or adipose tissue-derived MSCs and could maintain the multipotency. The therapeutic potential of the pMSCs requires further investigation.

Fetal bovine serum-free culture of endothelial progenitor cells-progress and challenges

Two decades after the first report on endothelial progenitor cells (EPC), their key role in postnatal vasculogenesis and vascular repair is well established. The therapeutic potential of EPC and their growing use in clinical trials calls for the development of more robust, reproducible, and safer methods for the in vitro expansion and maintenance of these cells. Despite many limitations associated with its usage, fetal bovine serum (FBS) is still widely applied as a cell culture supplement. Although different approaches aiming at establishing FBS-free culture have been developed for many cell types, adequate solutions for endothelial cells, and for EPC in particular, are still scarce, possibly due to the multiple challenges that have to be faced when culturing these cells. In this review, we provide a brief overview on the therapeutic relevance of EPC and critically analyse the available literature on FBS-free endothelial cell culture methods, including xeno-free, serum-free, and chemically defined systems.

Xeno-free pre-vascularized spheroids for therapeutic applications

Spheroid culture has gained increasing popularity, arising as a promising tool for regenerative medicine applications. Importantly, spheroids may present advantages over single-cell suspensions in cell-based therapies (CT). Unfortunately, most growth media used for spheroid culture contain animal origin-components, such as fetal bovine serum (FBS). The presence of FBS compromises the safety of CT and presents economic and ethical constraints. SCC (supplement for cell culture) is a novel xeno-free (XF) industrial cell culture supplement, derived from well-controlled pooled human plasma and processed under good manufacturing practice rules. Here, we developed a XF SCC-based formulation for 2D-culture of outgrowth endothelial cells (OEC), and then used it for generating co-culture spheroids of OEC and mesenchymal stem cells (MSC). XF MSC-OEC spheroids were characterized in detail and compared to spheroids cultured in FBS-supplemented medium. XF spheroids presented comparable integrity, size and morphology as the reference culture. The use of both media resulted in spheroids with similar structure, abundant extracellular matrix deposition and specific patterns of OEC distribution and organization. Notably, XF spheroids presented significantly enhanced angiogenic potential, both in vitro (fibrin sprouting assay) and in vivo (CAM assay). These findings are particularly promising in the context of potential therapeutic applications.