A fibrocyte is an inactive
mesenchymal cell, that is, a cell showing minimal
cytoplasm
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
, limited amounts of
rough endoplasmic reticulum, and lacks biochemical evidence of
protein synthesis.
The term ''fibrocyte'' contrasts with the term ''fibroblast''.
Fibroblasts are activated
connective tissue
Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...
cells characterized by synthesis of proteins of the
fibrous matrix, particularly the
collagen
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
s. When tissue is injured, the predominant mesenchymal cells, the fibroblast, have been believed to be derived from the fibrocyte or possibly from
smooth muscle cells lining vessels and glands. Commonly, fibroblasts express smooth muscle
actin
Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ...
, a form of actin first found in smooth muscle cells and not found in resting fibrocytes. Fibroblasts expressing this form of actin are usually called "myo-fibroblasts."
Recently, the term "fibrocyte" has also been applied to a bloodborne cell able to leave the blood, enter tissue and become a fibroblast. As part of the more general topic of
stem cell biology, a number of studies have suggested that the blood contains marrow derived cells that can differentiate into fibroblasts. These cells have been reported to express the
hematopoietic cell surface markers
CD34
CD34 is a transmembrane phosphoglycoprotein protein encoded by the CD34 gene in humans, mice, rats and other species.
CD34 derives its name from the cluster of differentiation protocol that identifies cell surface antigens. CD34 was first desc ...
+,
CD45+, as well as
collagen
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
. These cells can migrate to wound sites, suggesting a role in
wound healing. There are several studies suggesting that fibrocytes mediate wound healing and fibrotic tissue repair.
See also
*
List of human cell types derived from the germ layers
References
{{Authority control
Eukaryotic cells