**1. Introduction**

316 Advances in Hematopoietic Stem Cell Research

To LB, Haylock DN, Simmons PJ, Juttner CA. (1997). The biology and clinical uses of blood

Toru Ogata, Hidenori Shibamura, Gerard Tromp, Moumita Sinha, MStat, Katrina A. B.

Cheng-Ho Tsai, Hung-I Yeh, Yusan Chou, Hsin-Fu Liu, Tzu-Yao Yang , Jyh-Chwan Wang et

Gavin S. Wilkie, Kirsten S. Dickson and Nicola K. Gray. (2003). Regulation of mRNA

Ingrid G. Winkler and Jean-Pierre Levesque. (2006). Mechanisms of hematopoietic stem cell

A Zafiropoulos, N Crikas, A M Passam and D A Spandidos. (2004). CXCL12–3'A in the

Zhang B, Ye S., Herrmann SM, Eriksson P, de Maat M, Evans A, et al. (1999). Functional

development of sporadic breast cancer. J. Med. Genet; 41; e59

of coronary atherosclerosis. Circulation; 99:1788– 94.

case–control study. International Journal of Cardiology; 73 :191–95.

Goddard et al. (2005). Genetic analysis of polymorphisms in biologically relevant candidate genes in patients with abdominal aortic aneurysms. J Vasc Surg; 41:

al. (2000). G protein b3 subunit variant and essential hypertension in Taiwan – a

translation by 5'- and 3'-UTR-binding factors .TRENDS in Biochemical Sciences;

mobilization:When innate immunity assails the cells that make blood and bone.

polymorphism in the regulatory region of gelatinase B gene in relation to severity

stem cells. Blood; 89:2233–58.

Experimental Hematology; 34:996–1009.

1036–42.

28:182-88.

Fibrocytes constitute a unique population of mesenchymal progenitor cells from hematopoietic origin. They display a unique spectrum of immune and molecular characteristics such as the simultaneous expression of mesenchymal (collagen types I and III, fibronectin), leukocyte (CD45), monocyte (CD14), and hematopoietic stem cell (CD34) markers. Fibrocytes were initially described in the context of wound repair and since their original description in 1994, our understanding and knowledge of this novel cell population has grown considerably. They have the potential to differentiate into fibroblasts and myofibroblasts among other mesenchymal cells such adipocytes, osteoblasts, and chondrocytes. Fibrocytes are a rich source of inflammatory cytokines, growth factors, and chemokines that provide important intercellular signals within the local tissue microenvironment. Moreover, fibrocytes possess the immunological features typical of an antigen-presenting cell (APC), and they have the capacity for the presentation of antigens to naïve T-cells.

The aim of this chapter is to present a comprehensive overview over the history and recent findings on the biology of fibrocytes as well as their putative participation in fibrotic disorders.
