A progenitor cell
is a biological cell
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
that, like a stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
, 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 only divide 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.
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.
Like stem cells, mostly, they are formed and transported in a colony, with the right conditions for them to grow and differentiate into their target tissues. Progenitor cells also take in a lot of bacterias, good and bad, and digest them. Though sometimes it may be a good thing with sicknesses and other bacterias that would not be wanted in the body, the good bacteria are also digested, breaking down the immune system.
In contrast, 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. But still, controversy remains because embryonic stem cells are true stem cells in that they are pluripotent and show unlimited capacity for self-renewal. In contrast, many cells termed adult stem cell
Adult stem cells are undifferentiated cells, found throughout the body after embryonic development, that multiply by cell division to replenish dying cells and regenerate damaged tissues...
s would be better defined as progenitor cells, as their capacities for unlimited self-renewal and plasticity have not been comprehensively demonstrated.
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.
|| Stem Cell
|| Progenitor Cell
| Self-renewal in vivo
| Self-renewal in vitro
|| Unipotent, sometimes oligopotent
| Maintenance of self-renewal
|| Reaches maximum number of cells before differentiating
|| Does not reach maximum population
The majority of progenitor cells lie dormant or possess little activity in the tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
in which they reside. They exhibit slow growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...
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 factor
A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes....
s or cytokine
Cytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...
s are two substances which trigger the progenitors to mobilize towards 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.
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
The subventricular zone is a paired brain structure situated throughout the lateral walls of the lateral ventricles. It has been associated with having four distinct layers of variable thickness and cell density, as well as cellular composition....
. Some of these transit amplifying neural progenitors
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
migrate via rostral migratory stream
The rostral migratory stream is a pathway found in the brain of some animals along which neuronal precursors that originated in the subventricular zone of the brain migrate to reach the main olfactory bulb . This pathway has been studied in the rodent, rabbit, and both the squirrel and rheusus...
to the olfactory bulb and differentiate further into specific types of neural cells.
- Bone marrow stromal cells
Mesenchymal stem cells, or MSCs, are multipotent stem cells that can differentiate into a variety of cell types, including: osteoblasts , chondrocytes and adipocytes...
, basal cell of epidermis have 10% of progenitor cell, although they are often classed as stem cells due to their high plasticity and potentially unlimited capacity for self renewal.
Periosteum is a membrane that lines the outer surface of all bones, except at the joints of long bones. Endosteum lines the inner surface of all bones....
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 (EPC). These are very important for research on fracture and wounds healing.
Development of the human cerebral cortices
Before E40 (embryonic day 40), progenitor cells generate other progenitor cells; after that period progenitor cells produce only dissimilar daughters. The cells from a single progenitor cell form a proliferative unit that creates on cortical column; these columns contain a variety of neurons with different shapes.
- Barber CL, Iruela-Arispe ML(2006). The ever-elusive endothelial progenitor cell: identities, functions and clinical implications. Pediatric Researc 59, 722
- I. Todorov, , I. Nair, K. Ferreri, J. Rawson, A. Kuroda, M. Pascual, K. Omori, L. Valiente, C. Orr, I. Al-Abdullah, A. Riggs, F. Kandeel(2005). Multipotent Progenitor Cells Isolated From Adult Human Pancreatic Tissue. Transplant Proceedings 37, 3420-3421
- Raewyn M. Seaberg and Derek van der Kooy(2003). Stem and progenitor cells: the premature desertion of rigorous definitions. Trends in Neurosciences 26, 125-131