A progenitor cell is a biological cell that, like a stem cell, has a tendency
to differentiate into a specific type of cell, but is already more specific than
a stem cell and is pushed to differentiate into its "target" cell.
The most important difference between stem cells and progenitor cells is that
stem cells can replicate indefinitely, whereas progenitor cells can divide only
a limited number of times. Controversy about the exact definition remains and
the concept is still evolving. The terms "progenitor cell" and "stem
cell" are sometimes equated. Properties
Most progenitors are described as oligopotent. In this point of view, they
may be compared to adult stem cells. But progenitors are said to be in a further
stage of cell differentiation. They are in the “center” between stem cells and
fully differentiated cells. The kind of potency they have depends on the type of
their "parent" stem cell and also on their niche. Some progenitor cells were
found during research, and were isolated. After their marker was found,
it was proven that these progenitor could move through the body and migrate
towards the tissue where they are needed. Many properties are shared by
adult stem cells and progenitor cells. Progenitor cells are found in adult
organisms and they act as a repair system for the body. They replenish
special cells, but also maintain the blood, skin and intestinal tissues. They
can also be found in developing embryonic pancreatic tissue.
Function The majority of progenitor cells lie
dormant or possess little activity in the tissue in which they reside. They
exhibit slow growth and their main role is to replace cells lost by normal
attrition. In case of tissue injury, damaged or dead cells, progenitor cells
can be activated. Growth factors or cytokines are two substances that
trigger the progenitors to mobilize toward the damaged tissue. At the same
time, they start to differentiate into the target cells. Not all progenitors
are mobile and are situated near the tissue of their target differentiation.
When the cytokines, growth factors and other cell division enhancing
stimulators take on the progenitors, a higher rate of cell division is
introduced. It leads to the recovery of the tissue.
Examples The characterization or the defining
principle of progenitor cells, in order to separate them from others, is based
on the different cell markers rather than their morphological appearance.
Satellite cells found in muscles. They play a major role in muscle cell
differentiation and injury recoveries. Intermediate progenitor cells formed in
the subventricular zone. Some of these transit amplifying neural progenitors
migrate via rostral migratory stream to the olfactory bulb and differentiate
further into specific types of neural cells.
Bone marrow stromal cells, basal cell of epidermis have 10% of progenitor cell,
although they are often classed as stem cells due to their high plasticity and
potential for unlimited capacity for self-renewal.
Periosteum contains progenitor cells that develop into osteoblasts and
chondroblasts. Pancreatic progenitor cells are among
the most-studied progenitors. They are used in research to develop a cure
against diabetes type-1. Angioblasts or endothelial progenitor
cells. These are very important for research on fracture and wounds healing.
Blast cells are involved in generation of B- and T-lymphocytes, which
participate in immune responses. Development of the human cerebral
cortices Before embryonic day 40, progenitor
cells generate other progenitor cells; after that period, progenitor cells
produce only dissimilar mesenchymal stem cell daughters. The cells from a single
progenitor cell form a proliferative unit that creates one cortical column;
these columns contain a variety of neurons with different shapes.
See also Induced progenitor stem cells
References