Cyclosporin-A in vivo produces severe osteopenia in the rat: effect of dose and duration of administration

Rapid loss of vertebral mineral density after renal transplantation

BACKGROUND

Osteopenia is a major complication of renal transplantation. Immunosuppressive regimens including cyclosporine, which permit the use of lower doses of glucocorticoids, may reduce glucocorticoid-induced osteopenia.

METHODS

We prospectively studied the magnitude, distribution, and mechanism of bone loss in 20 adults who received renal allografts from living related donors, who had good renal function, and who were treated with azathioprine, cyclosporine, and low doses of prednisone. We measured serum biochemical markers of bone metabolism, determined the bone mineral density of the second, third, and fourth lumbar vertebrae and the shaft of the radius, and analyzed the histomorphometric features of iliac bone at the time of transplantation and six months later. Measurements of vertebral mineral density were repeated 18 months after transplantation in 17 of the patients.

RESULTS

After transplantation, the mean serum concentrations of parathyroid hormone, phosphorus, and alkaline phosphatase decreased and the serum calcitriol concentration increased. The mean (+/- SD) bone mineral density of the vertebrae had decreased 6.8 +/- 5.6 percent 6 months after transplantation (P less than 0.05) and 8.8 +/- 7.0 percent 18 months after transplantation. In contrast, the bone mineral density of the radius had increased six months after transplantation (P less than 0.05). The histomorphometric studies showed that the rate of bone formation decreased from 50.5 +/- 44.8 to 23.1 +/- 13.8 microns3 per square micrometer per year (P less than 0.05), and the formation period lengthened from 70 +/- 42 to 146 +/- 144 days (P less than 0.05). Consequently, the amount of bone replaced during a remodeling cycle diminished.

CONCLUSIONS

Osteopenia associated with renal transplantation remains a problem in the cyclosporine era. The loss of vertebral bone in our subjects was due to an imbalance in bone remodeling consistent with a toxic effect of glucocorticoids.

Osteoporosis associated with rheumatoid arthritis: pathogenesis and management

Rheumatoid arthritis is associated with both localized and generalized osteoporosis. Localized osteoporosis can be considered to be caused by local disease mechanisms, including the generation of factors from activation of the cytokine pathway. The etiology of generalized osteoporosis has been difficult to elucidate, particularly because of the lack of sensitive techniques to measure bone mineral density. The introduction of single- and dual-photon absorptiometry and quantitative computed tomography has allowed more accurate assessment of bone mineral density. In general, bone mineral density loss at appendicular sites does not correlate well with axial bone density loss. Corticosteroid treatment exaggerates the development of osteoporosis in up to 40% of patients with rheumatoid arthritis. Sex hormone status, physical activity, disease duration, and functional class are all significant predictors for the development of osteoporosis. Current therapy for prevention and treatment is based largely on theoretical considerations. Physical activity should be encouraged once acute joint inflammation has settled. Postmenopausal women and amenorrheic premenopausal women will benefit from cyclical estrogen replacement. Patients with low serum 1,25-dihydroxy vitamin D3 levels, and males with low serum testosterone levels, are candidates for replacement therapy with the appropriate hormones. In patients who are receiving corticosteroids the dose should be limited, and oral calcium supplements are of benefit. The use of the newer corticosteroid deflazacort, and disease-modifying immunosuppressive drugs, are discussed. Other therapeutic options which should be considered, although published trials are scarce, are calcitonin and the diphosphonates. Further studies are awaited concerning the optimum prevention and treatment of osteoporosis associated with rheumatoid arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth inhibition by cyclosporine A in vivo and in vitro

Cyclosporine A is a commonly used immunosuppressant in organ transplant. However, in addition to its nephro- and hepato-toxicity, we now report that it also exerts growth inhibiting effects in vivo and in vitro. Rats treated with daily Cyclosporine A I.P. injections of 10 mg or 20 mg/kg body weight gained weight at significantly lower rates than controls over a six week period. This growth retardation was completely reversible. By 6 weeks post treatment, the body weights of the treated animals were the same as controls. In contrast, rats treated with lower doses of cyclosporine A (5 mg/kg) did not suffer any growth retardation throughout. In vitro, rat primary cultured fibroblasts treated with greater than 1 microgram/ml Cyclosporine A suffered 25-60% cell loss in the post-log phase but the cytotoxic effect was not apparent during the log phase of growth. Fibroblasts treated with less than or equal to 1 microgram/ml of Cyclosporine A did not suffer any cell loss. In conclusion, Cyclosporine A exerts growth inhibitory effects in vivo when given at greater than 5 mg/kg body weight and cytotoxic effects in vitro at greater than 1 microgram/ml.

Effects of interleukin-1 alpha and cyclosporin A in vivo and in vitro on bone and lymphoid tissues in mice

The purpose of this study was to investigate the effects of interleukin-1 alpha (IL-1 alpha) infusion and the ability of cyclosporin A (CYA) to alter IL-1 alpha-induced effects on bone in vivo and in vitro and lymphoid organs in vivo. Mice were administered: IL-1 alpha (2, 4, or 6 days), CYA (6 days), or IL-1 alpha and CYA (6 days). Hypercalcemia was induced in mice treated with IL-1 alpha compared to controls and CYA treated mice, and decreased urinary calcium excretion was present in IL-1 alpha and CYA groups. Osteoclastic bone resorption was increased with a resultant loss of total bone area and bone formation (as measured by mineral apposition rate) was decreased in mice infused with IL-1 alpha. Although CYA-treatment increased bone formation as compared to IL-1 alpha-treatment; CYA in combination with IL-1 alpha did not alter the reduction in mineral apposition rate caused by IL-1 alpha, IL-1 alpha also stimulated bone resorption in vitro which was significantly inhibited by cyclosporin A. IL-1 alpha-induced splenic granulopoiesis, peripheral blood neutrophilia, thymic atrophy, and lymphoid hyperplasia in lymph nodes. CYA-treatment resulted histologically in a severe depletion of lymphocytes in the thymus, a moderate depletion of lymphocytes in lymph nodes but no difference in the histology of the spleen compared to controls. In summary, interleukin-1 alpha was effective in stimulating hypercalcemia and bone resorption both in vivo and in vitro but cyclosporin A was effective in inhibiting IL-1 alpha-mediated bone resorption only in vitro. IL-1 alpha also had marked effects on spleen, thymus, and circulating blood cells; however, most parameters were not affected by the concurrent administration of cyclosporin A.

Physiological and pharmacological regulation of biological calcification

Biological calcification is a highly regulated process which occurs in diverse species of microorganisms, plants, and animals. Calcification provides tissues with structural rigidity to function in support and protection, supplies the organism with a reservoir for physiologically important ions, and also serves in a variety of specialized functions. In the vertebrate skeleton, hydroxyapatite crystals are laid down on a backbone of type I collagen, with the process being controlled by a wide range of noncollagenous proteins present in the local surroundings. In bone, cells of the osteoblast lineage are responsible for the synthesis of the bone matrix and many of these regulatory proteins. Osteoclasts, on the other hand, are continually resorbing bone to both produce changes in bone shape and maintain skeletal integrity, and to establish the ionic environment needed by the organism. The proliferation, differentiation, and activity of these cells is regulated by a number of growth factors and hormones. While much has already been discovered over the past few years about the involvement of various regulators in the process of mineralization, the identification and functional characterization of these factors remains an area of intense investigation. As with any complex, biological system that is in a finely tuned equilibrium under normal conditions, problems can occur. An imbalance in the processes of formation and resorption can lead to calcification disorders, and the resultant diseases of the skeletal system have a major impact on human health. A number of pharmacological agents have been, and are being, investigated for their therapeutic potential to correct these defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of patients and side effects during cyclosporine therapy for cutaneous disorders

Cyclosporine has been used in the experimental treatment of multiple inflammatory diseases of presumed autoimmune origin, including insulin-dependent diabetes mellitus, uveitis, rheumatoid arthritis, inflammatory bowel diseases, Graves' disease, and myasthenia gravis. In dermatology, the drug has been used successfully as primary therapy for psoriasis and psoriatic arthritis, alopecia areata, pyoderma gangrenosum, Behçet's disease, atopic dermatitis, and lichen planus. At a dose of 3 to 5 mg/kg per day, cyclosporine is well tolerated by most patients. However, because of concerns about its potential short- and long-term side effects, patients who use this drug require close monitoring. This review discusses appropriate clinical and laboratory evaluations, common and unusual side effects and their management, drugs that might alter the pharmacokinetics of cyclosporine metabolism, and criteria for dosage adjustments.

Cyclosporin A and tissue antigen matching in bone transplantation. Fibular allografts studied in the dog

We studied the mechanical, metabolic, and histologic properties of short-term nonvascularized cortical bone grafts in a canine fibular graft model. Sham operated nonvascularized autotransplanted and allotransplanted bones were compared. The allografts were performed between dog leukocyte antigen (DLA) class I and II matched; DLA class I and II mismatched; and cyclosporin A (CsA) treated, DLA class I and II mismatched animals. Cyclosporin was given for 1 month, and all the animals were followed for 3 months after surgery. Mechanical properties were investigated using standard torsional tests, metabolic kinetics were assessed using isotopic prelabeling techniques, and histomorphometric analysis of cross-sectional area properties and sequential fluorochrome labels were performed. Autografts were mechanically stronger and stiffer than all the types of allograft. CsA-treated, DLA-mismatched allografts performed better than matched allografts. These in turn were stronger than non-CsA-treated, mismatched allografts, which underwent nearly complete resorption. These relationships were preserved in the metabolic and histologic analyses. In this short-term animal study, although DLA matching resulted in a slight improvement in graft outcome, mismatched grafts in dogs receiving a short course of cyclosporin A fared even better.

Combined treatment with cyclosporin A and cortisone acetate minimizes the adverse bone effects of either agent alone

Although cyclosporin A (CsA) and cortisone acetate (CRT) adversely affect bone, their combined effect on bone is unknown. Sprague Dawley rats were therefore administered either vehicle or CsA (7.5 mg/kg/day) by gavage and saline or CRT (2 mg/100 mg/day) by s.c. injection for 28 days. Group A received vehicle plus saline, group B CsA plus saline, group C vehicle plus CRT, and group D CsA/CRT. Serial bloods were sampled over a 28-day period for ionized calcium (Ca), PTH, 1,25 dihydroxyvitamin D (1,25(OH)2D), and bone gla protein (BGP osteocalcin) and tibia were examined on day 28 for histomorphometry. Results were compared with group A. Ca and PTH levels in groups B, C, and D were similar to those in group A during the study period. Group B had lower body weights, elevated levels of BGP, and an increase in 1,25(OH)2D. Group C developed weight loss and a decrease in BGP and 1,25(OH)2D. Group D had weight loss, BGP levels between those of group A and group C, and 1,25(OH)2D values similar to group A. Bone histomorphometry revealed high turnover osteopenia in group B and hyperostosis in group C with a decrease in bone formation and osteoclastlike cells. Combination therapy returned these to control values. In conclusion, the adverse effects of either CsA or CRT on bone in rats are minimized by combined therapy.

1,25 Dihydroxyvitamin D3 modifies cyclosporine-induced bone loss

We have previously shown that cyclosporin A (CsA) produces high bone remodeling with resorption exceeding formation and loss of bone volume in the rat. This may have important clinical implications where CsA is widely used in organ transplantation. 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) is a bone mineralizing hormone which also has immune modifying properties. Consequently, we studied the effect of combined CsA and 1,25(OH)2D3 administration over 28 days in four groups of rats. Group A received vehicle (n = 10), group B CsA (15 mg/kg) (n = 10) alone, group C 1,25(OH)2D3 plus CsA (n = 15), and group D 1,25(OH)2D3 alone (20 ng/100 g) (n = 15). Rats were bled periodically at day 0, 7, 14, and 28 and Ca, parathyroid hormone (PTH), 1,25(OH)2D, osteocalcin (bone Gla-protein, BGP), BUN, and creatinine were measured. Rats were sacrificed on day 28 and bones were examined histomorphometrically. Compared to controls, CsA resulted in significant elevation of BGP and a transient increase in 1,25(OH)2D with excess bone remodeling and loss of bone volume. 1,25(OH)2D3 administration produced hypercalcemia, a significant rise in BGP, with suppression of PTH and increased osteoid volume. Combined therapy prevented the loss of bone volume probably due to increased osteoid tissue and enhanced osteoblast activity. Renal dysfunction, a side-affect of CsA, was not a factor. In conclusion, 1,25(OH)2D3 combined with CsA restores bone volume which is accompanied by increases in serum calcium and BGP.

Hyperostosis induced by the bisphosphonate (2-PEBP) in the oophorectomized rat

To prevent the high turnover bone remodeling associated with acute estrogen deficiency, the bisphosphonate [2-(2-pyridinyl) ethylidene-BP] (2-PEBP) was administered to oophorectomized (OX) rats. Three groups of 15 rats each (250 g) were studied. Group (Gp) A was sham operated, Gp B was OX, and Gp C received 2-PEBP (1.72 mg/kg/day) intraperitoneally for 3 days commencing 4 days postoophorectomy. Oophorectomy was confirmed with serum estradiol measurements. Blood samples were collected on days -7, 0, 7, 14, 21, and 28 for ionized calcium (Ca2+), PTH, and serum bone gla protein (BGP). Rats received tetracycline for bone histomorphometric labeling. All results were compared to Gp A. Body weight increased significantly in Gps B and C (P less than 0.005 by day 28). There was no significant difference in Ca2+, and PTH levels in Gps B and C were similar to Gp A. BGP levels were significantly higher on day 28 in Gp B (P less than 0.05). In Gp C, BGP levels were significantly decreased on days 7, 21, and 28 (P less than 0.03). Gp B revealed increased bone turnover without loss of bone volume (BV/TV). BV/TV was significantly increased in Gp C despite a decrease in parameters of bone formation and normal osteoclast number. In conclusion, 2-PEBP in the OX rat inhibited bone resorption more than formation with resultant hyperostosis. Serum BGP appeared to be a good marker of the changes observed on bone histomorphometry.

Regression of bone and cartilage loss in adjuvant arthritic rats after treatment with cyclosporin A

To test the effect of cyclosporin A (CsA) on arthritis-related bone resorption, we studied 30 female rats with adjuvant-induced arthritis (AIA). The animals were randomly assigned to 5 groups of 6 animals each; they received daily oral doses of 3, 5, 10, or 15 mg/kg CsA or placebo for 10 days. The parameters studied were (a) caliper measurements of hindpaw swelling, (b) radiometric densitometry of caudal vertebrae, (c) quantitative histomorphometry of radiographed vertebrae, and (d) glycosaminoglycan measurements in femoral condyles. A significant dose-dependent regression of articular swelling occurred in rats given 5, 10, and 15 mg/kg CsA, and this was concomitant with improvement in bone density. These results correlated with those of quantitative bone morphometry. Thus, trabecular volume was significantly reduced in AIA rats, but restoration to virtually normal values occurred with CsA doses between 5 and 15 mg/kg. The protective effect of CsA on articular damage was supported by the dose-dependent progressive improvement in total femoral condyle glycosaminoglycan content. The favorable effect of CsA on AIA is likely due to a blockade of T cell activation via an inhibition of production of lymphokines such as interleukin-2 and gamma-interferon. The consequent cessation of the immune reaction would lead to a reduction in the release of cytokines, such as interleukin-1, that are likely to be the mediators of the pathologic bone and cartilage breakdown that is characteristic of arthritic disease.

Cyclosporines: correlation of immunosuppressive activity and inhibition of bone resorption

Cyclosporine A (CsA) is a potent immunosuppressive agent that inhibits stimulated bone resorption in vitro. To study the mechanism of this effect, we have compared CsA with several cyclosporine analogs that vary in immunosuppressive potency. CsA as well as another potent immunosuppressive analog, CsG, inhibited parathyroid hormone (PTH) and interleukin-1 (IL-1)-stimulated resorption of fetal rat limb bones. The nonimmuno-suppressive analogs CsH and CsF did not inhibit PTH or IL-1-stimulated bone resorption. Likewise, the weakly immunosuppressive analog CsD did not significantly inhibit PTH-stimulated bone resorption. Although other mechanisms cannot be excluded, our data are consistent with the concept that bone resorption may involve an immune cell-derived mediator.

Bone-derived proteins

The diagnosis and treatment of metabolic bone disease has been limited by a lack of understanding of bone cell physiology and of suitable markers for various bone cell functions in different diseases. The identification of noncollagenous proteins and their measurement in serum has added to our knowledge. At this stage, of all the bone-derived proteins, bone Gla protein (BGP) is apparently the most useful, but it is best used in conjunction with other tests. The diagnostic usefulness of other noncollagenous proteins, procollagen, and local factors still remains to be documented.

Cyclosporin A in the oophorectomized rat: unexpected severe bone resorption

Local factors, such as interleukin-1, may mediate the accelerated bone remodeling in the acute estrogen-deficient rat. Cyclosporin A (CsA), which in vitro inhibits some of these local factors, was administered to oophorectomized (OX) rats in an attempt to modify this high turnover state. Three groups of 15 rats were studied. Group A was sham operated, group B was OX, and group C was OX and received CsA (15 mg/kg per day) by gavage commencing 4 days postoophorectomy for 28 days. Estradiol levels were determined to confirm oophorectomy. Blood was sampled on days -7, 0, 7, 14, 21, and 28 for ionized calcium (Ca2+), 1,25-(OH)2-vitamin D, PTH, and bone gla protein (BGP). Rats received tetracycline hydrochloride for bone histomorphometric labeling. All results were compared to group A. Body weight was increased in group B (p less than 0.003) but not in group C. There was no difference in Ca2+ or PTH between the groups. BGP levels were higher in group B by day 28 (p less than 0.005); BGP levels were increased in group C from days 7-28 (p less than 0.002). 1,25-(OH)2-vitamin D was significantly increased in group C (p less than 0.0001) but not in group B. Tibial bone histomorphometry revealed increased measurements of bone formation and osteoclast number without a loss of bone volume (BV/TV) in group B. Group C showed a dramatic increase in bone turnover with significant loss of BV/TV (p less than 0.001). In conclusion, CsA in the OX rat resulted in unexpected enhanced bone remodeling with high BGP levels and severe bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)