Changes in the levels of putrescine, spermidine, and spermine and their biosynthetic enzymes, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAM-decarboxylase) were studied during matrix-induced endochondral bone and bone marrow development. Ribonucleic acid (RNA) synthesis was studied by [3H]uridine incorporation into an acid-precipitable fraction. ODC and SAM-decarboxylase activity exhibited similar peaks on Day 3 and on Days 8 and 9 after matrix implantation and were correlated with corresponding peaks of [3H]thymidine incorporation during proliferation of chondroprogenitor and osteoprogenitor cells, respectively. In contrast an increase in SAM-decarboxylase but not ODC was observed during hematopoietic bone marrow formation while the incorporation of [3H]thymidine in these cells remained high. The concentrations of all three polyamines were low on Day 1 and rose to peak values during osteogenesis on Day 11 and declined thereafter. Putrescine, but not spermidine or spermine, also exhibited an earlier smaller but broad peak on Days 3-7 during mesenchymal cell proliferation and cartilage differentiation. Incorporation of [3H]uridine into acid-precipitable material exhibited two peaks on Days 5 and 11 during early phase of chondrogenesis and osteogenesis. The peak levels of putrescine, spermidine, and spermine on Day 11 coincided with increased RNA synthesis during osteogenesis. Autoradiographic localization of [3H]thymidine indicated a stimulation of cell proliferation adjacent to matrix particles prior to chondrogenesis and osteogenesis. Osteogenic precursor cells tended to be in close apposition to chondrolytic foci on Day 11.
ASJC Scopus subject areas
- Developmental Biology