The effects of prostaglandin A1 and prostaglandin B1 on the differentiation of cartilage in the chick embryo

Quantitative analysis of angiogenesis and growth of bone: effect of indomethacin exposure in a combined in vitro-in vivo approach

Nonsteroidal anti-inflammatory agents have been used experimentally and clinically to suppress a variety of physiological events, including angiogenesis and formation of bone. The exact mechanisms by which indomethacin alters skeletal tissue generation are unknown, due in part to methodological limitations. By the use of an organ culture assay and an animal model using intravital microscopy in mice bearing dorsal skinfold chambers, the effect of indomethacin on growth and angiogenesis of neonatal femora was characterized over 16 days. In both assays, femora significantly elongated with time (P < 0.05). The in vitro growth rate was more rapid than in vivo and dependent on the serum concentration, culture medium and age of mice. Although enhancing the serum content promoted cellular proliferation in organ culture, it dose-dependently suppressed femoral elongation, leading at 20% fetal calf serum to growth rates identical to those observed in vivo. Indomethacin supplementation (2 and 10 mg l-1) significantly accelerated longitudinal femoral growth in organ culture (P < 0.05), whereas in vivo indomethacin (2 mg kg-1) did not modulate either angiogenesis or elongation of bone. Our in vitro data propose a central role of serum in the regulation of bone formation. Although indomethacin altered femoral growth in vitro, our findings do not suggest that indomethacin suppresses angiogenesis or growth of bone in vivo. The complexity of physiological events in vivo may be obscuring a detectable effect.

Effects of retinoic acid treatment on release of arachidonic acid by chondrogenic cells in response to ionophore A23187

Chondrogenic differentiation in mouse limb bud mesenchymal cells cultured at high density was suppressed by supplementation of the medium with retinoic acid in a dose-dependent fashion. Cells prelabeled with (3H) arachidonic acid were treated with 0.3 microgram/ml retinoic acid. Treatment with retinoic acid increased the (3H) fatty acid in the triglyceride fraction. Furthermore, treatment with retinoic acid enhanced the release of (3H) fatty acid upon stimulation of these cells with the divalent ionophore A23187. These data permit the suggestion that there may be a correlation between altered lipid metabolism and retinoic acid's ability to disrupt chondrogenic differentiation.

Arachidonate metabolism during chondrogenesis in vitro

Chick embryo limb bud mesenchyme cells undergoing chondrogenesis in vitro were labeled with [3H] arachidonic acid and [14C] palmitic acid, and stimulated by mechanical means to convert a portion of their incorporated [3H] to radiolabeled compounds which co-chromatographed with authentic prostaglandins in the appropriate thin layer chromatography system. Chondrogenesis was (1) inhibited by concentrations of indomethacin or eicosa-5,8,11,14-tetraynoic acid which inhibited conversion of [3H] to prostaglandinlike compounds; and (2) stimulated by prostaglandin E2. We interpret these data to mean that (1) cells undergoing chondrogenesis in vitro are able to metabolize endogenous arachidonic acid to prostaglandins, and (2) synthesis of prostaglandinlike compounds is requisite to chondrogenesis in vitro.