Page 1755 - Hematology_ Basic Principles and Practice ( PDFDrive )

C H A P T E R 99

MESENCHYMAL STROMAL CELLS

Jacques Galipeau

Alexander Friedenstein first described, in 1974, fibroblast-like in Development of MSC-like Cells as a Cellular Pharmaceutical
colony-forming units (CFU-F) isolated from the bone marrow for GVHD”.
(BM) by plastic adherence in tissue culture plates that could support
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hematopoiesis in vitro. The culture-expanded progeny derived from
CFU-F could proliferate robustly and differentiate into mesenchymal ENDOGENOUS MESENCHYMAL STEM CELLS
lineages. In 1991, Arnold Caplan from Case Western Reserve Uni-
versity introduced the term mesenchymal stem cells (hereafter MSCs) The estimated frequency of CFU-F progenitors relative to total
to name this unique cell population, referring to their mesenchymal nucleated cells in marrow is approximately 1 : 100,000 to 1 : 240,000.
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plasticity and potential use in bone repair. He and others then Despite their relative rarity, endogenous marrow MSCs are active
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proceeded to demonstrate that these cells could differentiate into components of the BM hematopoietic niche. They are mainly
several mesenchymal lineages, such as bone, cartilage, muscle, and localized in the endosteum of the bone where they give rise to peri-
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fat, and serve as progenitor cells for nonhematopoietic tissues. cytes, myofibroblasts, osteocytes, and endothelial cells, as well as all
The intrinsic mesenchymal plasticity deployed by culture-expanded functional elements of the BM stroma supporting HSCs and progeni-
MSCs informed the notion that they could be used in regenerative tor cells development. MSCs have also been identified in vivo as
medicine for the treatment of congenital mesenchymal disorders perivascular cells expressing the STRO1, CD146 and 3G5 antigens.
such as osteogenesis imperfecta (OI). Based on the ability of MSCs to Despite a close relationship between these two cell types in terms of
migrate to the bone and differentiate into osteoblasts, Edwin Horwitz surface phenotype and qualitative in vitro assays, MSCs in general
et al hypothesized that the infusion of whole BM containing mesen- lack the contractility of pericytes and may show marked differences
chymal progenitors could attenuate if not cure OI. In 1999 the first in gene expression. In addition, some have described a neuroectoder-
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clinical study was conducted on three infants with severe deforming mal origin of MSCs through either Sox1 neuroepithelial cells or
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OI infused with unmanipulated BM graft from human leukocyte Nestin precursors. MSCs also express fibronectin, laminin, collagen,
antigen (HLA)–identical or single antigen-mismatched siblings fol- and proteoglycans, which are part of the extracellular matrix of the
lowing a myeloablative regimen. All patients presented hematopoietic BM stroma. Importantly, MSCs directly interact with hematopoietic
engraftment, and new bone formation could be seen in bone biopsies cells via an array of surface markers and cytokines, which regulate
performed 3 months after implantation. Total body bone mineraliza- different aspects of HSC development: quiescence, proliferation, and
tion and growth were increased, while fracture incidence was reduced differentiation. Cell–cell contact between MSCs and hematopoietic
in the first 6 months following BM transplantation. Encouraged by cells is mediated by several adhesion molecules such as intercellular
these results, this group conducted a second clinical trial published in adhesion molecule (ICAM)-1, ICAM-2, ICAM-3, vascular cell adhe-
2002, in which OI infants were not only given BM transplant, but sion molecule (VCAM)-1, leukocyte function–associated antigen
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were also infused with in vitro expanded allogeneic MSCs. Of the (LFA)-3, CD44, and CD72. Among factors secreted, MSCs were
six infants treated, five presented MSC engraftment in BM—albeit shown to express hematopoietic growth factors such as bone mor-
at a very low frequency—accompanied by a net increase in growth. phologic protein 4 (BMP4), Flt-3, leukemia inhibitory factor (LIF),
However, only one child had a substantial increase in total body oncostatin M (OSM), stem cell factor (SCF), stromal cell-derived
mineralization. Since no changes were observed in the only patient factor-1 (SDF-1), and transforming growth factor-β (TGF-β), and
in whom injected MSCs did not engraft, the beneficial effects seen in interleukins such as interleukin (IL)-1, IL-6, IL-7, IL-8, IL-11, IL-14,
the other infants can presumably be attributed to the infused MSCs and IL-15. CFU-F–forming cells from BM can be obtained through
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and their paracrine effect. Contemporaneous to the OI studies, a the prospective isolation of CD45 MSCs with anti-STRO1, anti-
first-in-human clinical use of culture-expanded autologous marrow CD271, or anti-CD146 antibodies, or selection for nestin-expressing
MSCs by Hillard Lazarus was conducted in 1995 as adoptive cell cells. Nevertheless, not enough data concerning purified MSCs are
therapy for support of hematopoiesis in the setting of autologous available to assume that endogenous MSC progenitors possess the
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peripheral blood stem cell transplantation (SCT). In addition same immune regulatory properties of ex vivo expanded culture-
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to their trophic effects on hematopoiesis, intravenous transfusion adapted MSCs. Therefore, almost the entire amount of data con-
of MSCs were later shown to deploy robust immune suppressive cerning the immunological properties of MSCs refers to adherent
properties in a nonhuman primate model of skin allotransplantation, expanded, culture-adapted MSCs.
which augured a 2004 case report from the Karolinska Institute by
Katarina LeBlanc describing the anecdotal yet substantial effect of
haploidentical MSCs on steroid-resistant grade IV acute graft-versus- BONE MARROW MESENCHYMAL STEM CELL
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host disease (GVHD) in a 9-year-old boy (Fig. 99.1). This report MANUFACTURE AND PHENOTYPE
was followed by a series of phase II studies of allogeneic MSCs
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in prevention and treatment of acute, steroid-refractory GVHD. The manufacture of MSCs in large numbers requires collection
However, a phase III clinical trial of an industrial random donor and processing of marrow followed by ex vivo culture expansion in
MSC product in steroid-resistant acute GVHD reported in 2009 that serum-containing growth media. Typical processing protocols involve
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it failed to meet its primary endpoint of durable GVHD remission. Ficoll enrichment of mononuclear cells from liquid BM aspirates
Notwithstanding, culture-expanded MSC-like cells derived from and subsequent plating of unfractionated nucleated cells onto plastic
marrow, adipose tissue, or umbilical cord are under intense clinical tissue culture plates maintained within humidified incubators set at
study for ailments falling roughly into three categories: adjunct to 37°C and 5% CO 2. Within a week or so, plastic adherent CFU-F
hematopoietic stem cell (HSC) transplantation, autoimmune and arise, and subsequent passaging depletes nonadherent myelolym-
inflammatory disease, and tissue repair. See box titled “Considerations phoid cells and gives rise to a homogenous polyclonal population of

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