A progenitor cell is a biological cell that can differentiate into a specific cell type. Stem cells and progenitor cells have this ability in common. However, stem cells are less specified than progenitor cells. Progenitor cells can only differentiate into their "target" cell type. 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 identified as oligopotent. In this point of view, they can compare 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 research found that progenitor cells were mobile and that these progenitor cells 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.

Research

Progenitor cells have become a hub for research on a few different fronts. Current research on progenitor cells focuses on two different applications:

regenerative medicine Regenerative medicine deals with the "process of replacing, engineering or regenerating human or animal cells, tissues or organs to restore or establish normal function". This field holds the promise of engineering damaged tissues and organs by st ...

and cancer biology. Research on regenerative medicine has focused on progenitor cells, and stem cells, because their cellular

senescence Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word ''senescence'' can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence invol ...

contributes largely to the process of aging. Research on cancer biology focuses on the impact of progenitor cells on cancer responses, and the way that these cells tie into the immune response. The natural aging of cells, called their cellular senescence, is one of the main contributors to aging on an organismal level. There are a few different ideas to the cause behind why aging happens on a cellular level.

Telomere A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature mos ...

length has been shown to positively correlate to longevity. Increased circulation of progenitor cells in the body has also positively correlated to increased longevity and regenerative processes. Endothelial progenitor cells (EPCs) are one of the main focuses of this field. They are valuable cells because they directly precede endothelial cells, but have characteristics of stem cells. These cells can produce differentiated cells to replenish the supply lost in the natural process of aging, which makes them a target for aging therapy research. This field of regenerative medicine and aging research is still currently evolving. Recent studies have shown that haematopoietic progenitor cells contribute to immune responses in the body. They have been shown to respond a range of

inflammatory cytokine An inflammatory cytokine or proinflammatory cytokine is a type of signaling molecule (a cytokine) that is secreted from immune cells like helper T cells (Th) and macrophages, and certain other cell types that promote inflammation. They include i ...

s. They also contribute to fighting infections by providing a renewal of the depleted resources caused by the stress of an infection on the immune system. Inflammatory cytokines and other factors released during infections will activate haematopoietic progenitor cells to differentiate to replenish the lost resources.

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

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...

s. They play a major role in muscle cell differentiation and injury recoveries. *

Intermediate progenitor cell Intermediate progenitor cells (IPCs) are a type of progenitor cell in the developing cerebral cortex. They are multipolar cells produced by radial glial cells who have undergone asymmetric division. IPCs can produce neuron cells via neurogenesis ...

s formed in the

subventricular zone The subventricular zone (SVZ) is a region situated on the outside wall of each lateral ventricle of the vertebrate brain. It is present in both the embryonic and adult brain. In embryonic life, the SVZ refers to a secondary proliferative 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. *

Radial glial cell Radial glial cells, or radial glial progenitor cells (RGPs), are bipolar-shaped progenitor cells that are responsible for producing all of the neurons in the cerebral cortex. RGPs also produce certain lineages of glia, including astrocytes and ...

s found in developing regions of the brain, most notably the cortex. These progenitor cells are easily identified by their long radial process. * Bone marrow stromal cells found in the epidermis and make up 10% of progenitor cells. They are often classed as stem cells due to their high plasticity and potential for unlimited capacity for self-renewal. *

Periosteum The periosteum is a membrane that covers the outer surface of all bones, except at the articular surfaces (i.e. the parts within a joint space) of long bones. Endosteum lines the inner surface of the medullary cavity of all long bones. Structu ...

contains progenitor cells that develop into

osteoblasts Osteoblasts (from the Greek combining forms for " bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cells with a single nucleus that synthesize bone. However, in the process of bone formation, osteoblasts functi ...

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. *

Blast cell In cell biology, a precursor cell, also called a blast cell or simply blast, is a partially differentiated cell, usually referred to as a unipotent cell that has lost most of its stem cell properties. A precursor cell is also known as a proge ...

s are involved in generation of B- and

T-lymphocytes A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell r ...

, which participate in immune responses. * Boundary cap cells from the

neural crest Neural crest cells are a temporary group of cells unique to vertebrates that arise from the embryonic ectoderm germ layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, per ...

form a barrier between the cells of the central nervous system and cells of the peripheral nervous system. Boundary cap neural crest stem cells promote survival of mutant SOD1 motor neurons.

Development of the human cerebral cortices

Before embryonic day 40 (E40), 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.

References

{{DEFAULTSORT:Progenitor Cell Stem cells Biotechnology Cell biology Developmental biology Cloning

Properties

Research

Examples

Development of the human cerebral cortices

See also

References