Fig. 1.

Feedback-regulated tissue homeostasis and cell growth properties in the ordinary differential equations model. (A) Stem cells divide at a rate v producing either two stem cells with probability p or two differentiated cells with probability (1 - p). Differentiated cells die at a rate d and produce factors that inhibit self-renewal and division in stem cells. (B) Inhibited growth. If only differentiation feedback is lost, the population of stem cells and differentiated cells grows without bound at a slower than exponential rate. (B) Uninhibited growth. If both feedbacks are lost, stem cells and differentiated cells grow at a rate dominated by the same exponential. Time is expressed in units of , the expect duration of one cell cycle at equilibrium.