Origin and Differentiative Capacities of Cells in the Blastema of the Regenerating Salamander Limb

Abstract

The salamander limb regenerate develops from a mesenchymatous bud of cells called the blastema. This review briefly considers the local origin and major features of blastemal cells and then discusses their role in the histogenesis of the regenerate. The capacity of blastemal cells to form the various cell types of the regenerate is first considered in general terms, with the discussion focusing on three major alternatives: blastemal cells form (a) cartilage only, (b) connective tissues only, or (c) essentially all internal tissues of the regenerate. The differentiative properties of blastemal cells originating from known cell types are then considered in detail. Cartilage is of particular interest in this regard, because it has been utilized as a pure cell type. Results from the study of mixed tissues, including muscle and connective tissue of the fin, are also presented. Information gained from the study of known cell types participating in regeneration is discussed in terms of the mechanisms responsible for the stability of cellular differentiation and in terms of the flow of cells from stump tissues into the regenerate.