Corticosteroid-induced changes in glucose metabolism of chondrocytes

Cartilage-flow phenomenon and evidence for it in perichondrial grafting

The cartilage-flow phenomenon has been frequently described but not in connection with transplantation procedures for treatment of cartilage lesions. Consequently, we examined this particular phenomenon in an experimental sheep model originally set up to study the use of perichondrial grafts for repair of full-thickness cartilage lesions. Osteochondral lesions were made in nonweight-bearing and weight-bearing areas of knee joints in 36 sheep. The defects were filled with autologous rib perichondrial grafts and secured by either collagen sponges or fibrin glue (n = 24 animals). Defects without perichondrial grafts served as controls (n = 12 animals). Following 1 week of immobilisation of the operated leg, the plaster was removed, and animals were allowed to move freely. Animals were killed after 2, 4, 12 and 16 weeks. Grafts including rims of original surrounding cartilage and bone were removed and investigated by means of macroscopy, histology and micromorphology, including scanning electron microscopy and analysis under polarized light. Cartilage flow was observed in all specimens by 4 weeks after drilling the defects, independent of the weight-bearing condition. These flow formations exhibited a bending of the collagen fibres centrally into the defects, reduction of metachromasia, cell cluster formation and areas of reduced cell density. Time-dependent flow formations were observed related to the weight-bearing condition and whether or not the defects had been grafted. In grafted, non-weight-bearing defects further cartilage flow was stopped 8 weeks after transplantation by the growing perichondrial transplants, which had filled the defects completely. In contrast, control defects exhibited further flow formations in both areas. The same was observed in grafted defects in the weight-bearing area. In defects without complete filling as not enough spontaneously growing fibrous tissue had arisen from the bottom of the defects, two different observations were made: either the defects exhibited a fungiform mass of fibrous tissue that had overgrown the lateral flow formations, or the central mass of fibrous tissue was overgrown by the lateral flow formations. In conclusion, cartilage flow seems to be a mechanically induced phenomenon at the rims of cartilage lesions that contributes little to the reduction of size of large osteochondral defects. There was no evidence for new cartilage proliferation or production of cartilaginous matrix at the rims of the lesions.

Autologous rib perichondrial grafts in experimentally induced osteochondral lesions in the sheep-knee joint: morphological results

The purpose of the present study was to examine the fate of autologous perichondrial grafts after transplantation into cartilage lesions in weight-bearing joints. Osteochondral lesions were made in the articular surface of knee joints in 36 sheep. The defects were filled with autologous rib perichondrial grafts which were secured by either collagen sponges (12 animals) or fibrin glue (12 animals). Defects without perichondrial grafts served as controls (12 animals). Following 1 week of immobilization of the operated leg, the plaster was removed and the animals were allowed to move freely. Animals were sacrificed after 4, 8, 12 and 16 weeks. The grafts were removed and investigated histologically. In contrast to weight-bearing areas and control defects, hyaline-like cartilage formation was seen in non-weight-bearing areas after 4 weeks. This newly formed cartilage revealed strong metachromasia following staining with acidic toluidine blue and reacted positively with periodic acid-Schiff, indicating de novo synthesis of proteoglycans and glycoproteins. Scanning electron microscopy and examinations with polarized light confirmed a hyaline cartilage-like architecture for the surface area as well as for the fibre orientation of the whole graft. Enzyme histochemistry for alkaline and acid phosphatase activity showed positive reactivity only at the base of the transplants.

Characterization of cytosolic glucocorticoid receptor of fetal rat epiphyseal chondrocytes

The cytosolic glucocorticoid receptor of 21st gestational day rat epiphyseal chondrocytes has been evaluated. The receptor, a single class of glucocorticoid binding component approached saturation, utilizing [3H]triamcinolone acetonide ([3H]TA) as the radiolabeled ligand, at approximately 1.8-2.0 x 10(-8) M. The dissociation constant (Kd) reflected high-affinity binding, equaling 4.0 +/- 1.43 x 10(-9) M (n = 7) for [3H]TA. The concentration of receptor estimated from Scatchard analysis was approximately 250 fmol/mg cytosolic protein and when calculated on a sites/cell basis equalled 5800 sites/cell. The relative binding affinities of steroid for receptor were found to be triamcinolone acetonide greater than corticosterone greater than hydrocortisone greater than progesterone greater than medroxyprogesterone acetate much greater than 17 alpha-hydroxyprogesterone much greater than testosterone greater than 17 beta-estradiol. Cytosolic preparations activated in vitro by warming (25 degrees C for 20 min) were shown to exhibit an increased affinity for DNA-cellulose. 46% of the total specifically bound activated ligand-receptor complex was bound to DNA-cellulose. Cytosol maintained at 0-4 degrees C in the presence of 10 mM molybdate or activated in vitro in the presence of molybdate, bound to DNA-cellulose at 8 and 10% respectively. DEAE-Sephadex elution profiles of the nonactivated receptor were indicative of a single binding moiety which eluted from the columns at 0.4 M KCl. Elution profiles of activated receptor were suggestive of an activation induced receptor lability. The 0.4 M KCl peak was diminished, while a concomitant increase in the 0.2 M KCl peak was only modestly discernible. Evaluation of endogenous proteolytic activity in chondrocyte cytosol using [methyl-14C]casein as substrate show a temperature-dependent proteolytic activity with a pH optimum of 5.9-6.65. The proteolytic activity was susceptible to heat inactivation and was inhibitable, by 20 mM EDTA. The sedimentation coefficient of the nonactivated receptor was 9.3s (n = 6) on sucrose density gradients and exhibited steroid specificity and a resistance to activation induced molecular alterations when incubated in the presence of 10 mM molybdate. Receptor activation in vitro, in the absence of molybdate induced an increased receptor susceptibility to proteolytic attack and/or enhanced ligand receptor dissociation as evidenced by a diminution of the 9.3s binding form without a concomitant increase in 5s or 3s receptor fragments.

Effect of swimming on bone growth and development in young rats

The effect of chronic swimming on bone modelling was studied. Forty female Sabra rats (5 weeks old) were randomly assigned to the following experimental groups: 30 rats were trained to swim (water bath 35 +/- 1 degree C, one h daily, five times a week) for 20 weeks--20 of them loaded with lead weights (1% body weight) while the rest (10 animals) swam load free. Ten sedentary rats matched for age and weight served as controls. At the end of the twenty-week swimming period, all rats were sacrificed, both humeri bones were dissected and prepared for the following examinations: morphometric, bone density (BD), bone mineral content (BMC), compression tests and cross-sectional geometrical parameters, histomorphometry and biochemical analysis of minerals (Ca, Pi, Mg, Zn). All measured parameters were found to be significantly higher (P less than 0.05) in the swimming rats irrespective of load, as compared with the controls. Bone weight was higher by 19%, bone volume by 11%, bone length by 2.8%, cortical area by 16%, BD by 7% and BMC by 15%. The compression breaking force at the distal shaft of the humerus was higher by 24% in the trained group, while the ultimate compressive stress was not significantly different. Maximal and minimal moment of inertia at the distal diaphysis were 33.4 and 40% higher, respectively, for the swimming groups than the controls. Ca, Pi, Mg and Zn levels per total humeral bone were significantly higher in the exercising rats. The histomorphometry and cross-sectional data emphasize longitudinal and transversal growth. These data indicate that swimming exercise exerts a positive effect on bone growth and development in young rats.

Craniofacial and central nervous system malformations induced by triamcinolone acetonide in nonhuman primates: II. Craniofacial pathogenesis

This study further defines the craniofacial malformations induced by triamcinolone acetonide in the rhesus monkey. Ten timed-mated pregnant rhesus monkeys (Macaca mulatta) received intramuscular injections of 10 mg/kg TAC on days 23, 25, 27, 29, and 31 of gestation. Results of previous experiments with rhesus and bonnet monkeys and baboons indicated that specific craniofacial and brain malformations could be induced with TAC during this period of pregnancy (Hendrickx et al., '80). Stage-matched TAC-treated and control embryos (stages 17-18 and 22) and age-matched TAC-treated and control fetuses (50, 60, and 70 days gestation) were removed by hysterotomy. Stage 17-18 TAC embryos appeared grossly normal but histologic evaluation revealed a shortened anlage of the posterior cranial base. Stage 22 TAC embryos and all TAC fetuses exhibited craniofacial dysmorphia and encephalocele. The developing sphenoid was the earliest affected and most severely malformed bone. Its defects included reduced anterioposterior and transverse dimensions, reduced orbitosphenoid and alisphenoid, abnormal pituitary fossa, and reduced dorsum and tuberculum sellae. In addition, shortening of the posterior cranial base and decreased cranial base angle was a consistent finding in the treated embryos and fetuses. Decreased ossification and remodeling in the facial bones and abnormal position due to the malformed sphenoid occurred.

Glucocorticoid-induced changes in the activity of cartilage alkaline phosphatase

Glucocorticoid hormones are known to exert distinct inhibitory effects upon cartilage metabolism and endochondral bone growth. This study examined the influence of triamcinolone hexacetonide, a long-acting synthetic analogue off cortisol, on the activity of non-specific alkaline phosphatase i condylar cartilage of neonatal mice. Four-day-old mice received a single dose (10 mg/kg) of the hormone and the activity of beta-glycerophosphatase was assayed 3 and 6 days thereafter. Whereas no significant changes were noted in the enzyme's specific activity, distinct alterations were observed in the latter's distributional pattern. By 48 hours cells along both the proliferative and chondroblastic zones exhibited a significant enhancement of alkaline phosphatase activity. This increase in enzyme activity was most prominent along the cells' plasmalemma and within their adjacent matrix. Thus, glucocorticoid hormones possess a significant stimulatory effect upon alkaline phosphatase activity in very young cartilage cells which in turn might affect the mineralization process.

Long bone growth during prolonged intermittent corticosteroid treatment and subsequent rehabilitation

Immature A/J mice were treated for up to 7 weeks intermittent doses of triamcinolone hexacetonide and were thereafter allowed to recover for 7 weeks. Qualitative and quantitative morphological measurements were performed on the epiphyseal cartilage plate and diaphyseal bone of the humerus. By the third injection significant structural changes were noted in the cartilaginous tissue followed by a complete cessation of bone growth. The hormonal inhibitory effect on long bone growth lasted throughout the experimental period. However, at the end of the recovery period the length of the humerus was 96% of the normal. In contrast, the humeral width at midshaft and the width of its medullary cavity revealed slower recovery, achieving only 80% of the control values. Following rehabilitation, the growth of experimental epiphyseal plates exceeded that of nontreated animals as their width and the number of hypertrophic chondrocytes were 131% and 125% of their controls respectively. Thus, in A/J mice (a highly susceptible inbred strain of mice) intermittent (every four days) administration of a long-acting corticosteroid hormone arrested endochondral and periosteal bone formation; the former, however, underwent full recovery following the termination of the hormonal treatment.

Mandibular growth retardation in corticosteroid-treated juvenile mice

Juvenile mice were treated for up to eight weeks with weekly doses of a synthetic analogue of cortisol:triamcinolone hexacetonide. The mandibular condylar cartilage was studied histologically and histochemically at regular intervals. Morphometric measurements were performed along the mandibular posterior vertical dimension (condylar process and ramus). By the second injection significant morphological changes were noted in the condylar cartilage, followed by retardation of bone growth. The most distinctive feature in the cartilage of triamcinolone-treated mice was a marked increase in the dimension of its mineralized zone concomitant with a significant increase in the number of hypertrophic chondrocytes. The role of condylar cartilage in mandibular growth is discussed.