It has been observed in several tissues that direct isolation of cells in serum-free media and
on nonadhesive substrates results in the formation of spherical clusters of cells known as
free-floating spheres. Such free-floating spheres have been hypothesized to contain
undifferentiated multipotent progenitor cells. Our goal was to isolate and characterize such
free-floating spheres from HTM cell primary cultures. For this purpose, HTM cells were
incubated in serum-free media and on a nonadhesive substrate. Individual free-floating …