It is assumed that production by differentiated cells of soluble receptors to cell growth factors may mediate a feedback mechanism controlling cell growth and differentiation in the body. Based on this assumption, it is hypothesized that with age a concentration of such soluble receptors in the body fluids gradually augments as a consequence of increasing a proportion of the differentiated cell pool.

In the old body, when present in the cellular microenvironment at relatively high concentrations these receptors might markedly diminish ligand binding to the membrane-bound counterparts in a competitive manner and, thereby, significantly reduce cell regeneration activity. Under such conditions, connective fibers rather than newly generated cells could be filling the niches forming because of cell death.