Biomedical Engineering Reference
In-Depth Information
Table 10.3 Some growth factors that may have signifi cant future therapeutic application, and the
conditions they aim to treat
Growth factor
Possible medical indication
TPO
Thrombocytopenia
EGF
Wound healing, skin ulcers
TGF-
Bone healing, skin ulcers, detached retinas
FGFs
Soft tissue ulcers, wound healing
Neurotrophic factors
Mainly conditions caused by/associated with neurodegeneration, including peripheral
neuropathies, amyotrophic lateral sclerosis and neurodegenerative diseases of the brain
The study of the process of haemopoiesis is rendered diffi cult by the fact that it is extremely dif-
fi cult to distinguish or separate individual stem cells from their products during the earlier stages
of differentiation. However, a picture of the process of differentiation is now beginning to emerge
(Figure 10.1). During the haemopoietic process, the stem cells differentiate, producing cells that
become progressively more restricted in their choice of developmental options.
The production of many mature blood cells begins when a fraction of the stem cells differentiates,
forming a specifi c cell type termed CFU-S (where CFU refers to colony-forming unit). These cells,
in turn, differentiate to yield CFU-GEMM cells, a mixed CFU that has the potential to differen-
tiate into a range of mature blood cell types, including granulocytes, monocytes, erythrocytes,
platelets, eosinophils and basophils. Note that lymphocytes are not derived from the CFU-GEMM
pathway, but differentiate via an alternative pathway from stem cells (Figure 10.1).
The details of haemopoiesis presented thus far prompt two very important questions: (1) How
is the correct balance between stem cell self-renewal and differentiation maintained? (2) What
forces exist that regulate the process of differentiation? The answer to both questions, in particular
the latter, is beginning to emerge in the form of a group of cytokines termed 'haemopoietic growth
factors'. This group includes:
several interleukins, which primarily affect production and differentiation of lymphocytes;
CSFs, which play a major role in the differentiation of stem-derived cells into neutrophils,
macrophages, megakaryocytes (from which platelets are derived), eosinophils and basophils;
EPO, which is essential in the production of red blood cells;
TPO, which is essential in the production of platelets.
Table 10.4 The range of blood cells that are ultimately produced upon
the differentiation of pluripotential stem cells (see text for details).
(Note that osteoclasts are multinucleated cells often associated with
small depressions on the surface of bone. They function to reabsorb
calcifi ed bone)
Neutrophils
T- and B-lymphocytes
Eosinophils
Erythrocytes
Basophils
Monocytes
Megakaryocytes
Osteoclasts
Search WWH ::




Custom Search