The Collagenous Hemopoietic Microenvironment

The collagens of the connective tissues serve to support a variety of tissue architectures throughout the body.1 The various structural elements of the collagens preserve the physical and functional integrity of the various tissues. In general, the distribution as well as architectural disposition of collagens differ greatly from one connective tissue to another and may be correlated with specific roles. In this capacity, the collagenous hematopoietic stroma mechanically supports the blood cells and regulates the cellular migration. Blood cells follow circulatory pathways meticulously laid out in time and place.2–4 Yet, it is only recently that our understanding of the complex role of collagen and cell-matrix interactions that influences cytodifferentiation, mitogenesis, and morphogenesis has truly come of age.5–8 With respect to the regulation of hemopoiesis, it is known that the hemopoietic microenvironment influences the growth and differentiation of hematopoietic cells. Although still somewhat poorly defined, we shall see that this microenvironment contains structural well-defined extracellular collagenous components.