Myogenic and Chondrogenic Cell Populations in the Axolotl Limb Regeneration Blastema

97 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.Methods have been developed for culturing axolotl limb blastema cells in vitro in order to study the differentiative abilities of cells in various spatial regions of the blastema. These methods have been combined with observations of blastema development in vivo. By means of labeled tissue grafting, cells derived from dedifferentiation of stump cartilage were shown to be located primarily in the core of the undifferentiated blastema though substantial numbers of them were found in the blastema periphery as well. Since dedifferentiated cartilage cells are found only in cartilage at later stages of regeneration, this suggests that the blastema can regulate its cellular composition through redistribution or death of these peripherally located cells. Autoradiography of radioactive sulfate uptake into regenerating limbs on stumps from which the skeletal elements had been surgically removed was used to illustrate the regeneration of cartilage from cells of other than skeletal tissues. Cartilage redifferentiates immediately distal to stump muscle tissue in these limbs rather than immediately distal to bone or cartilage as in normal limbs. Culturing explants from undifferentiated blastemas arising on the surgically altered limb stumps was used to demonstrate that these blastemas contain abnormally high numbers of muscle-derived, myogenic cells in their proximal chondrogenic regions, although their final pattern of regenerated cartilage in vivo is entirely normal. This again suggests regulation of blastema cell subpopulations by their redistribution, elimination, or metaplasia. Blastema cells were also cultured in vitro following their disaggregation into single-cell suspensions. Cells from proximal portions of undifferentiated blastemas rapidly re-aggregated into compact masses, indicating that their cell surface properties differ from those of distal cells. Cultures of cells from blastema regions which form cartilage in vivo also formed precartilage matrix in vitro. When the limb stumps lacked skeletal elements however, cells from the proximal normally chondrogenic region produced much less precartilage matrix in vitro.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD