Hematopoietic Stem Cells

These are the stem cells that make up the origin of blood elements. They can be isolated from bone marrow, peripheral blood, and umbilical cord blood.

The major surface markers are CD34, CD14, CD45 and CD133. The precursor cells, also the ancestor of hematopoietic stem cells, are called hemangioblast. Some of these precursor cells transform into hematopoietic stem cells, the source of blood cells, while others progress to endothelial progenitor cells.

Recent studies have shown that hematopoteic stem cells also play important roles in the process of vascular formation, called angiogenesis.

The most important source of hematopoietic stem cells is undoubtedly the bone marrow. In addition to blood diseases, they nowadays started to be used in clinical practice for the regeneration of damaged heart muscle after acute myocardial infarction. Hematopoietic stem cells remain silent in a closed microenvironment in the bone marrow, called the niche. When they move out of this environment, the process of differentiation into progenitor cells begins.

Umbilical Cord Blood

Umbilical cord blood derived hematopoietic stem cells recently started to be successfully used allogeneically in many types of blood diseases and cancer cases. Many universities have now established a cord blood bank within their structures. Cord blood derived stem cells are younger and healthier stem cells with a greater proliferation potential. Tissue compatibility criteria are much less and tissue rejection reactions are very rare. In other words, successful results can be obtained even if they do not match the individual's genetic HLA structure.

Normally, the stem cells remaining silent in healthy tissue are activated by endocrine and paracrine factors released into the environment after injury and begin to migrate to the injured environment. First, the proliferation of stem cells is triggered depending on the signal they receive, they then reach the site of damage through the blood and differentiate into the cell that is needed. Being in the silent state is thought to protect stem cells against DNA damage. On the first day of tissue damage, very different amounts and types of growth factors and mediators are secreted from injured tissue or activated platelets. Of these, transforming growth factor beta (TGF-β) has been shown to have significant effects on mesenchymal stem cells. TGF-β activates, awakens and calls the stem cells residing in adipose tissue or bone marrow.