TABLE 1.

DEFINITIONS OF CELL TYPES

Stem cell	Cells with unlimited self renewal, dividing asymmetrically to produce an identical daughter cell and a more differentiated progenitor.
Bone marrow stem cell	Comprises hematopoietic and mesenchymal stem cells.
Hematopoietic stem cell	Stem cell able to form all cells of the blood lineage.
Mesenchymal stem cell	Stromal stem cell able to produce supporting cells including bone, fat, and cartilage.
Fibroblast	Main mature cell type involved in the production of the extracellular matrix and collagen of tissues.
Myofibroblast	Fibroblasts can be activated (e.g., by transforming growth factor β) to form these cells, which produce extracellular matrix but also have the ability to contract. Stain for α-smooth muscle actin.
Fibrocytes	Circulating peripheral cells of bone marrow origin. Often described as blood-derived fibroblasts. Express a characteristic pattern of markers including the leukocyte common antigen CD45, the hematopoietic marker CD34, and collagen 1.