The effect of hydrocortisone on the growth of chick bone rudiments in chemically defined medium

Physiologic Medium Maintains the Homeostasis of Immature Bovine Articular Cartilage Explants in Long-Term Culture

The ability to maintain living articular cartilage tissue in long-term culture can serve as a valuable analytical research tool, allowing for direct examination of mechanical or chemical perturbations on tissue behavior. A fundamental challenge for this technique is the recreation of the salient environmental conditions of the synovial joint in culture that are required to maintain native cartilage homeostasis. Interestingly, conventional media formulations used in explanted cartilage tissue culture investigations often consist of levels of metabolic mediators that deviate greatly from their concentrations in synovial fluid. Here, we hypothesize that the utilization of a culture medium consisting of near-physiologic levels of several highly influential metabolic mediators (glucose, amino acids, cortisol, insulin, and ascorbic acid) will maintain the homeostasis of cartilage explants as assessed by their mechanical properties and extracellular matrix contents. Results demonstrate that the aforementioned mediators have a strong effect on the mechanical and biochemical stability of skeletally immature bovine cartilage explants. Most notably, 1) in the absence of cortisol, explants exhibit extensive swelling and tissue softening and 2) in the presence of supraphysiologic levels of anabolic mediators (glucose, amino acids, insulin), explants exhibit increased matrix accumulation and tissue stiffening. In contrast, the administration of physiologic levels of these mediators (as present in native synovial fluid) greatly improves the stability of live cartilage explants over one month of culture. These results may have broad applicability for articular cartilage and other musculoskeletal tissue research, setting the foundation for important culture formulations required for examinations into tissue behavior.

The effect of cortisol on porcine articular tissues in organ culture

(1) The effects of hydrocortisone succinate (1.0--0.01 micrograms HC/ml of medium) on porcine articular tissues in organ culture have been studied by histological and biochemical methods. (2) 1.0 and 0.1 micrograms HC/ml considerably inhibited the severe breakdown of matrix that occurs in living and dead cartilage explained in contact with synovial tissue. (3) The depletion of matrix in living cartilage cultivated in the same dish as but not in contact with synovial tissue, is much diminished when the medium contains 1.0 or 0.1 micrograms HC/ml. (4) Cartilage grown in the used medium of synovial tissue loses both proteoglycan and hydroxyproline; the addition of HC to the used medium has little (1.0 microgram HC/ml) or 0.1 microgram HC/ml) no inhibitory effect. If, however, the used medium is from synovial tissue that has been cultured in the presence of 1.0 or 0.1 micrograms HC/ml, loss of proteoglycan and collagen from the cartilage is much reduced. (5) In isolated cartilage in normal medium there is outgrowth of cells from the cut surface and some loss of proteoglycan and collagen; outgrowth is completely, and loss of matrix components partially suppressed by 1.0 micrograms HC/ml. (6) Isolated synovial tissue cultured in normal medium shrinks to about one-third of its original size, loses much of its collagen and secretes neutral metallo-proteinases into the medium; in the presence of 1.0 microgram HC/ml these changes are largely prevented. The explants also secrete an inhibitor of metallo-proteinases the production of which is not reduced by HC.

Light and electron microscopic observations on hydrocortisone-induced cleft palate in hamsters

Palatal histogenesis in hydrocortisone-treated hamster fetuses was studied by both light and electron microscopy. At an early stage in the hydrocortisone-affected fetuses, when the palatal shelves hung vertically on either side of the tongue, necortic changes could be seen in some of the basal epithelial cells which lay adjacent to the fragmented basal lamina. The normal looking cells lay on an intact basal lamina and were attached to the contiguous necrotic cells by desmosomes. With horizontal reorientation of the palatal shelves and their approach to the midline, cellular necrosis and fragmentation of the basal lamina increased. When compared with normal cells, the hydrocortisone-affected ones were seen to be lighter, to contain fewer ribosomes and no lysosomes. At a later stage, when midline palatal fusion was lacking, the epithelium underwent stratification and keratinization while the necrotic debris was removed by mesenchymal macrophages. It appears that the normal process of protein synthesis is inhibited following hydrocortisone administration and that this, in turn, during palatogenesis, disrupts normal cellular differentiation and the integrity of the basal lamina, which are associated with the production of a cleft palate.

The uptake and metabolism of (32-P)pyrophosphate by mouse calvaria in vitro

In order to study the uptake and metabolism of PP(i) by bone, (32)PP(i) was added to the medium surrounding explanted mouse calvaria maintained in organ culture. Most of the PP(i) was hydrolysed during incubation, but there was a measurable entry of intact PP(i) into bone. When (32)P(i) was added to the medium, synthesis of PP(i) and organic phosphates from P(i) was observed in bone. There was no detectable passage of PP(i) from bone into the medium. These results are discussed in terms of two models of pyrophosphate hydrolysis and exchange. Some quantitative estimates about the fate of PP(i) in bone were made.