Adult Stem Cells - Stem-Cell Nanoengineering - page 10

Adipocyte,
astrocyte, neuron,
cardiomycyte,
chondrocyte,
hepatocyte,
muscle,
osteoblast

Adipocyte,
chondrocyte, muscle,
osteoblast

Different
embryonic tissue
lineage, adipocyte,
osteocyte,
endothelial cell,
neuron,
chondrocyte

Bone
marrow

Synovial
membrane

Adipocyte,
chondrocyte, muscle,
osteoblast

Muscle

Teeth

Sources of
adult
mesenchymal
stem cells

Adipocyte, muscle,
chondrocyte,
osteoblast

Dermis

Blood

Adipocyte, osteoblast,
fibroblast

Pericyte

Chondrocyte

Adipocyte, chondrocyte,
osteoblast

Tr abecular bone

Periosteum

Adipose
tissue

Chondrocyte, osteoblast

Adipocyte, chondrocyte,
muscle, osteoblast,
stromal cell

Figure 1.2 Sources of adult mesenchymal stem cells and their potential of differentiation into
multilineage cell types.

marrow [63]. The two following characteristics of ADSCs have caught the attention of
scientists over the past few years: their immune privilege properties that are due to their lack
of human leukocyte antigen (HLA) DR (a class II major histocompatibility antigen - MHC
II) expression, which enable their use in therapeutic applications [64], as well as their
suppression of the proliferation of activated allogeneic lymphocytes [62, 65]. Other studies,
however, have demonstrated that these cells also possess immunosuppressive capacities,
as MSCs can lead to tumor growth and cell transformation [66, 67]. These contradictory
results demonstrate that further studies and protocols are necessary in order to identify the
effects of ADSCs on tumor formation [66, 68]. Seeliger et al. have demonstrated that hepa-
tocyte-like cells that are derived from adipose tissue offer a promising alternative approach
to the treatment of urgent metabolic liver dysfunctions or for in vitro use. The researchers
claim that hepatocyte-like cells have outstanding advantages as they maintain important
metabolic functions and many enzymatic activities during cryopreservation, which renders
them constantly available. As MSCs have an immunosuppressive capacity, the data obtained
by Seeliger et al. suggest that these cells can be applied autologously without any lifelong
immunosuppressive therapy being necessary [24].

Identification of MSCs
Mesenchymal stem cells are often identified by their morphology or by their phenotype, if
they have a fibroblast-like morphology. They can also be identified by several other means,
such as their differentiation potential into colony forming units (CFUs), which underlines
their proliferative capacity. In addition, the ability to adhere to plastic is another characteristic
marker for MSCs. Phenotypically, MSCs express various markers, but unfortunately none of
them is really specific to MSCs. However, it is generally agreed upon that adult human MSCs