Author/Authors :
xu, jun university of california - department of medicine, San Diego, usa , cong, min capital medical university - beijing friendship hospital, Beijing, China , park, tae jun yonsei university college of medicine - department of internal medicine, Seoul, Korea , scholten, david university hospital aachen - department of medicine iii, Aachen, Germany , brenner, david a. university of california - department of medicine, San Diego, USA , kisseleva, tatiana university of california - department of surgery, San Diego, USA
Abstract :
Since the discovery of fibrocytes in 1994 by Dr. Bucala and colleagues, these bone marrow (BM)-derived collagen Type I producing CD45+ cells remain the most fascinating cells of the hematopoietic system.Despite recent reports on the emerging contribution of fibrocytes to fibrosis of parenchymal and nonparenchymalorgans and tissues, fibrocytes remain the most understudied pro-fibrogenic cellular population.In the past years fibrocytes were implicated in the pathogenesis of liver, skin, lung, and kidney fibrosisby giving rise to collagen type I producing cells/myofibroblasts. Hence, the role of fibrocytes in fibrosisis not well defined since different studies often contain controversial results on the number of fibrocytesrecruited to the site of injury versus the number of fibrocyte-derived myofibroblasts in the same fibroticorgan. Furthermore, many studies were based on the in vitro characterization of fibrocytes formed afteroutgrowth of BM and/or peripheral blood cultures. Therefore, the fibrocyte function(s) still remain(s) lack ofunderstanding, mostly due to (I) the lack of mouse models that can provide complimentary in vivo real-timeand cell fate mapping studies of the dynamic differentiation of fibrocytes and their progeny into collagentype I producing cells (and/or possibly, other cell types of the hematopoietic system); (II) the complexityof hematopoietic cell differentiation pathways in response to various stimuli; (III) the high plasticity ofhematopoietic cells. Here we summarize the current understanding of the role of CD45+ collagen type I+BM-derived cells in the pathogenesis of liver injury. Based on data obtained from various organs undergoingfibrogenesis or other type of chronic injury, here we also discuss the most recent evidence supporting thecritical role of fibrocytes in the mediation of pro-fibrogenic and/or pro-inflammatory responses.
