In vitro chondrogenesis and cell viability

Abstract

Anterior somites cultured with (NSA) or without (SA) notochord, and posterior somites cultured with (NSP) or without notochord (SP) were compared with respect to changes in their DNA content, their potential to synthesize the active sulfate principle phosphoadenosine phosphosulfate (PAPS), and their ability to accumulate 35S-sulfate. Chondrogenesis was observed in the NSA, NSP, and SP explants, but was rarely noted in the SA explants. A decrease in DNA content during the initial 48 hr of culture was common to all explants. After this initial decrease, DNA content increased most in those explants forming cartilage. The synthesis of PAPS by cell-free extracts of each type of somite explant also decreased during the initial period of culture. Only extracts of those explants undergoing chondrogenesis showed increases in PAPS synthesis with continued culture. Each type of somite explant accumulated 35S-sulfate into chondroitin sulfate during the first hours of culture. The non-chondrogenic SA explants accumulated little 35S-sulfate during the period of culture. At varying times after 24 hr the chondrifying explants (NSA, SP, and NSP) initiated an increased rate of accumulation of 35S-sulfate. Cartilage nodules, increases in DNA content, PAPS synthesis and 35S-sulfate accumulation occurred within the same 24 hr period, during the 2nd day in NSP explants, the 3rd day in NSA explants, and between the 3rd and 4th day for SP explants. A hypothesis of in vitro somite chondrogenesis based on differential cell viability is presented.