Ana Stavljenić

Osteogenic protein-1 (bone morphogenetic protein-7) reduces severity of injury after ischemic acute renal failure in rat.

We have shown that osteogenic protein-1 (OP-1) (bone morphogenetic protein-7) is responsible for the induction of nephrogenic mesenchyme during embryonic kidney development. Gene knock-out studies showed that OP-1 null mutant mice die of renal failure within the first day of postnatal life. In the present study, we evaluated the effect of recombinant human OP-1 for the treatment of acute renal failure after 60 min bilateral renal artery occlusion in rats. Bioavailability studies in normal rats indicate that approximately 1.4 microg OP-1/ml is available in the circulation 1 min after intravenous administration of 250 microg/kg, which then declines steadily with a half life of 30 min. About 0.5% of the administered OP-1 dose/g tissue is targeted for OP-1 receptors in the kidney. We show that OP-1 preserves kidney function, as determined by reduced blood urea nitrogen and serum creatinine, and increased survival rate when administered 10 min before or 1 or 16 h after ischemia, and then at 24-h intervals up to 72 h after reperfusion. Histochemical and molecular analyses demonstrate that OP-1: (a) minimizes infarction and cell necrosis, and decreases the number of plugged tubules; (b) suppresses inflammation by downregulating the expression of intercellular adhesive molecule, and prevents the accumulation and activity of neutrophils; (c) maintains the expression of the vascular smooth muscle cell phenotype in pericellular capillaries; and (d) reduces programmed cell death during the recovery. Collectively, these data suggest that OP-1 prevents the loss of kidney function associated with ischemic injury and may provide a basis for the treatment of acute renal failure.

Discovery and Clinical Applications of Bone Morphogenetic Proteins

Significant progress has been made in the characterization of cartilage and bone differentiating proteins. A family of unique proteins known as bone morphogenetic proteins has been described, and there is ample evidence that they are directly responsible for de novo cartilage and bone formation in vivo. Extensive research is underway to develop appropriate and optimal delivery systems based on extracellular matrix components. It is likely that bone morphogenetic proteins will play a crucial role in bone and joint regeneration and repair.

HOLOGRAPHIC ANALYSIS OF THE HUMAN PELVIS

Twelve fresh human pelves with preserved lumbar spines, hip joints, and ligaments, were tested by double-exposure and sandwich-hoiogram interferometry. During physiologic loadings (50–300 N), the pelvis moved as a whole downward and backward. Iliac wings exhibited marked undulation, except for the central part, which showed minor deformations. The sacrum moved downward and rotated forward over an axis 5–9 cm below the promontorium. Removal of the sacroiliac interosseous ligaments eliminated all joint movements and caused a tighter contact between articular surfaces. Removal of the sacrotuberous and sacrospinous ligaments had no influence on the pelvic behavior. The magnitudes of deformrations as well as their underlying mineral contents were unequally distributed between the two pelvic sides. These results indicate that the sacroiliac interosseous ligamente are the main determinant of sacral movement. Asymmetric load transmittance to the hip joints might be responsible for the mineral content differences between the pelvic sides.

Relationship between Tubular and Tamm-Horsfall Proteinuria in Balkan Endemic Nephropathy

Excretion of low molecular mass proteins derived from blood plasma and Tamm-Horsfall protein, a specific renal protein, was determined in the subjects from the area of Balkan endemic nephropathy. A significantly higher excretion of Tamm-Horsfall protein was observed in the subjects with tubular type of proteinuria compared to the subjects with glomerular selective type proteinuria and the subjects with physiological type proteinuria.

Talc granulomatosis in the rat. Involvement of bone in the acute-phase response.

We investigated the dynamics of the acute-phase response (APR) and osteoblast trabecular surface in rats with subcutaneous inflammation provoked by magnesium silicate (talc). The first visible indicator of the APR was a rapid and profound hypozincemia, paralleled by a decrease in metaphyseal trabecular surfaces covered with osteoblasts in long bones. Both the intensity of serum APR and the decrease in osteoblast trabecular surface were directly proportional to the number of granulomas. Alterations in bone metabolism were specific for the inflammation, whereas mild hypozincemia and decrease in mononuclear and increase in polymorphonuclear peripheral white blood cell fractions developed in animals pair-fed with rats bearing two or four granulomas. Rats with talc granulomatosis had high serum ACTH and corticosterone levels, but neither adrenalectomy nor high doses of hydrocortisone could revert bone alterations in talc-injected animals. Glucocorticoids were necessary for the development of hypozincemia and hypercupremia seen in talc granulomatosis, as well as for normal bone metabolism. Inhibition of prostaglandin synthesis had no effect on bone alterations and serum APR in rats bearing talc-induced granulomas. We conclude that the decrease in bone formation constitutes an important aspect of the host acute-phase response in a rat model of talc granulomatosis.

Lipid and Lipoprotein Contents of Human Follicular Fluid

The concentrations of total cholesterol, phospholipids, triacylglycerols and lipoproteins were measured in 87 follicular fluids obtained from 35 women undergoing in vitro fertilization and embryo transfer. The results were correlated with the levels of progesterone in follicular fluid. Two different types of ovarian stimulation were used. High density lipoproteins were the dominant lipoproteins found in the preovulatory follicular fluid. Low density lipoproteins were absent or appeared in trace amounts. Significantly higher triacylglycerol and high density lipoprotein levels were found when stimulation with human menopausal gonadotropins and chorionic gonadotropin was applied, as compared to the clomiphene citrate-menopausal gonadotropin-chorionic gonadotropin menstrual cycle. In both groups, extracorporal fertilization resulted in cleavage of oocytes and embryo transfer. No significant correlation between any follicular fluid lipid and progesterone concentration was found. The lipids estimated in the follicular fluid appeared to have no influence on the oocyte fertilizability. The presence of triacylglycerols and high density lipoproteins in the follicular fluid may indicate follicular wall permeability under the treatment with menopausal gonadotropins.

1a,25-Dihydroxyvitamin D3 stimulates alkaline phosphatase activity and inhibits soft-tissue proliferation in implants of bone matrix.

To test the importance of vitamin D metabolites on intramuscular implants of demineralized bone, four-month-old rats were given either 1a,25-(OH)2D3 or 24R,25-(OH)2D3, or a combination of both metabolites, and sacrificed at intervals ranging from five to 35 days after implantation. Histologically there was a reduced ingrowth of mesenchymal cells into the implanted matrix cylinders in the presence of 1a,25-(OH)2D3; the reduction was followed by decreased total DNA and protein values until the 16th experimental day. At 35 days postimplantation, the quantity of new bone was the same in all treated groups. However, 1a,25-(OH)2D3 increased the alkaline phosphatase activity 60%-110% (depending on the denominator used). The metabolite 24R,25-(OH)2R3 had no effect on cell growth or the alkaline phosphatase activity. These results provide evidence for the inhibitory effect of 1a,25-(OH)2D3 on mesenchymal cell growth and its stimulatory effect on osteoblasts, which are responsible for increased alkaline phosphatase activity and new bone formation in vivo.

The influence of early parathyroidectomy on aluminum-induced rickets in growing uremic rats

Rats were subjected to a two-stage 5/6 nephrectomy and treated with aluminum for 2 and 4 weeks with a cumulative dose of 4.2 and 8.4 mg of aluminum, respectively. Other animals were parathyroidectomized and loaded with 8.4 mg of aluminum for 4 weeks. Histomorphometry and electron microscopy (tibiae), aluminum tissue (bone, kidney, liver) determination, serum (Ca, Mg, Zn, P, urea, creatinine, alkaline phosphatase, 1,25(OH)2D3, PTH) and urine (creatinine, A1) revealed that: (a) a dose of 8.4 mg aluminum was sufficient to induce rickets within 4 weeks of treatment and was associated with decreased serum calcitriol values and high aluminum accumulation within organs (electron-dense material was found in osteoblasts only); (b) previous parathyroidectomy prevented the occurrence of any aluminum-induced alteration of bone. It was associated with higher calcitriol and phosphorus values than in corresponding non-parathyroidectomized rats and significantly reduced aluminum accumulation within organs. The results was influenced neither by a drop in serum calcium values nor by different degrees of renal failure. We suggest that aluminum-induced rickets in growing uremic rats is prevented or delayed when previous parathyroidectomy has been performed.

Tamm-horsfall protein determination in Balkan endemic nephropathy

SummaryData on the excretion of Tamm-Horsfall protein (THP) in subjects living in an area of Balkan endemic nephropathy (BEN) are reported. The study subjects were divided into groups as follows: diseased, suspect, “at risk” and others, according to previously adopted criteria. The THP excretion in “at risk” subjects was found to be significantly higher as compared to control subjects. The difference between these two groups could not be registered by any other clinical or laboratory diagnostic methods. No difference in the excretion of THP was observed between the groups of others and control subjects. According to the results obtained, the excretion of THP may be considered a possibly useful additional diagnostic test for the detection of subjects with the latent, early subclinical phase of BEN. On the other hand, the data obtained shed some more light on the still obscure pathogenesis and natural history of BEN.

Acute zinc deficiency and trabecular bone loss in rats with talc granulomatosis

Subcutaneous inflammation induced by magnesium silicate (talc) leads to the suppression of bone elongation, osteoblast insufficiency, and subsequent bone loss in rats. Since bone and immunological changes in talc granulomatosis are similar to those observed in zinc deficiency, we investigated the kinetics of zinc tissue distribution and the effects of zinc supplementation on the development of bone loss in rats with talc-induced inflammation. Decrease in serum zinc concentration was observed between 5 and 15 h in rats with talc granulomatosis. It was paralleled by the accumulation of zinc in the liver and rapid disappearance of osteoblasts from the trabecular bone surfaces. However, talc-injected rats supplemented parenterally and orally with zinc sulfate exhibited a decrease in osteoblast trabecular surface comparable to that of unsupplemented rats bearing granulomas despite normalized serum zinc concentrations. Zinc supplementation slightly increased osteoblast trabecular surface in all supplemented groups, but this effect was not significant. We conclude that zinc is the earliest indicator of the acute-phase response in rats with talc granulomatosis. Although zinc appears to be important for the normal function of bone cells, there is no causative relationship between acute zinc deficiency and decreased osteoblast number and activity in rats with talc granulomatosis.