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

Resting T cells negatively regulate osteoclast generation from peripheral blood monocytes

There is accumulating evidence that T cells may be involved in osteoclastogenesis in a variety of murine systems. However, the precise role of human T cells in the regulation of osteoclast generation is still unclear. To address this issue, we investigated the effect of resting peripheral T cells on receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast generation from human peripheral monocytes. Although osteoclasts were not generated in the culture of human peripheral blood mononuclear cells (PBMC) in the presence of RANKL and macrophage colony-stimulating factor (M-CSF), the addition of cyclosporine A (CsA), a potent inhibitor of T-cell function, resulted in the formation of an increasing number of lacunae resorption on dentine, suggesting T cells may inhibit osteoclast formation. In a coculture of T cells and monocytes, which were isolated from PBMC, T cells inhibited the osteoclast generation from monocytes, as determined by tartrate-resistant acid phosphatase (TRAP) staining and a pit assay using dentine. This inhibition of osteoclast generation by T cells was also observed in a culture of the parathyroid hormone-stimulated SaOS4/3 osteoblast cell line and monocytes. The culture in Transwell plates revealed that the cell-to-cell interaction was not required for the inhibition, suggesting that T-cell cytokines may be responsible for the inhibition. Among inhibitory T-cell cytokines on osteoclastogenesis, granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-gamma) were actively produced by CD4 T cells but not CD8 T cells in the coculture of T cells with monocytes, and the neutralizing antibodies to these cytokines partially rescued the T-cell-induced inhibition of osteoclast formation. Although CsA did not affect RANKL-induced osteoclast generation in the culture of monocytes alone, it completely rescued the T-cell-induced inhibition of osteoclast formation and strongly inhibited the production of GM-CSF and IFN-gamma. Thus, we demonstrate that resting T cells negatively regulate the osteoclast generation via production of GM-CSF and IFN-gamma by CD4 T cells and that CsA stimulates the osteoclast generation through the inhibition of the production of these cytokines. These findings provide new insight into therapeutic strategies for immunosuppression-induced bone loss in transplant and other diseases.

Effects of Low-Dose Cyclosporin on Osteogenesis of Human Demineralized Bone Grafts in a Surgically Created Mandibular Defect in Rats

BACKGROUND

Demineralized freeze-dried bone matrix (DFDBM) stimulates new bone formation; however, immune reactions from the residual antigens of prepared grafts might play a role in inducing osteogenesis. This study examined whether cyclosporine-A (CsA), an immunosuppressant, enhanced the DFDBM-induced new bone formation.

METHODS

After creating a bony defect in the posterior mandible, 40 male Sprague-Dawley rats were divided into four groups of 10 each: no graft with mineral oil (control); no graft with CsA in mineral oil; DFDBM with mineral oil; and DFDBM with CsA in mineral oil (combined therapy). CsA was administered at 2 mg/kg body weight. Five rats in each group were sacrificed at days 10 and 28 and tissue samples were taken for histological examination.

RESULTS

Soft tissue was observed in the defects of all animals without grafts, whereas the repaired hard tissue formed in the defects of animals with grafts. Histometery, which was performed only at day 10, revealed both DFDBM and CsA therapies produced a significant increase in the total area of repaired hard tissue. Only CsA therapy significantly increased the new bone area. Compared with the DFDBM group, the composition of the repaired hard tissue in the combined therapy group shifted; i.e., the new bone area increased but the residual particle area decreased. The cartilage formation was greater in the combined therapy group than the DFDBM group.

CONCLUSION

Within the limitations of this study, we suggest that the DFDBM grafts play a major role, which could be enhanced by CsA, in the induction of new bone formation, especially at an early phase.

Influence of cyclosporin A therapy on bone healing around titanium implants: a histometric and biomechanic study in rabbits

BACKGROUND

Immunosuppressive agents may induce severe changes on bone metabolism. The purpose of the present study was to evaluate the influence of the administration of cyclosporin A (CsA) on the bone tissue around titanium implants.

METHODS

Eighteen New Zealand rabbits were randomly divided into 2 groups of 9 each. The test group (CsA) received daily subcutaneous injection of CsA (10 mg/kg body weight) and the control group (CTL) received saline solution by the same administration route. Three days after therapy began, 2 implants (7.0 mm long and 3.75 mm in diameter) were inserted bilaterally at the region of the tibial methaphysis. After 4, 8, and 12 weeks the animals were sacrificed and biomechanical tests and histometrical procedures, consisting of the determination of the percentages of bone-implant contact and bone area within the limits of the implant threads, were performed.

RESULTS

Intergroup analysis showed that the removal torque and the percentage of bone contact with the implant surface for CsA group were significantly lower than those of the CTL group at 12 weeks (28.5 and 39.2 N cm, P = 0.01; 7.76% and 18.52%, P = 0.02, respectively).

CONCLUSION

The data from the present study suggest that long-term administration of cyclosporin A may negatively influence bone healing around dental implants.

Bone histopathology and densitometry comparison between cyclosporine a monotherapy and prednisolone plus azathioprine dual immunosuppression in renal transplant patients

BACKGROUND

No study has compared the bone histopathologic findings in renal transplant patients receiving cyclosporine A (CsA) monotherapy with those in patients receiving a non-CsA regimen. The aim of this study was to compare bone densitometry and histomorphometry findings in patients receiving CsA monotherapy versus those receiving azathioprine + prednisolone dual therapy.

METHODS

A bone biopsy and densitometry were performed in 13 patients receiving CsA monotherapy and 12 patients receiving azathioprine + prednisolone, who had been on these regimens since the time of transplantation. Fourteen men and 11 women, age 51+/-12 years, with 140+/-75 months since transplantation, were included.

RESULTS

A low bone mineral density (BMD) was observed in patients on both immunosuppressive schemes-most notably at the distal radius and less significantly at the lumbar spine. No significant differences in BMD were observed between immunosuppressive groups. Histopathologic analysis of the group as a whole revealed mixed uremic bone disease in 42%, adynamic bone in 29%, hyperparathyroid disease in 17%, and normal bone in 12%. Patients showed a slight increase in osteoclast number and function, decreased osteoblast number and function, and retardation of dynamic parameters. No differences in histopathologic diagnosis or histomorphometric findings were observed between the immunosuppressive therapy groups. In addition to the immunosuppressive drugs, male gender and old age negatively affected bone mass.

CONCLUSIONS

Both prednisolone and CsA were associated with slight osteoclast stimulation and osteoblast suppression and marked retardation of mineral apposition and bone formation rates. Both drugs were also associated with reduced BMD at the axial and appendicular skeleton, even though a nonsignificant trend to a better-preserved lumbar spine BMD was observed in the CsA group.

Bone remodeling after renal transplantation

Several studies have indicated that bone alterations after transplantation are heterogeneous. Short-term studies after transplantation have shown that many patients exhibit a pattern consistent with adynamic bone disease. In contrast, patients with long-term renal transplantation show a more heterogeneous picture. Thus, while adynamic bone disease has also been described in these patients, most studies show decreased bone formation and prolonged mineralization lag-time faced with persisting bone resorption, and even clear evidence of generalized or focal osteomalacia in many patients. Thus, the main alterations in bone remodeling are a decrease in bone formation and mineralization up against persistent bone resorption, suggesting defective osteoblast function, decreased osteoblastogenesis, or increased osteoblast death rates. Indeed, recent studies from our laboratory have demonstrated that there is an early decrease in osteoblast number and surfaces, as well as in reduced bone formation rate and delayed mineralization after transplantation. These alterations are associated with an early increase in osteoblast apoptosis that correlates with low levels of serum phosphorus. These changes were more frequently observed in patients with low turnover bone disease. In contrast, PTH seemed to preserve osteoblast survival. The mechanisms of hypophosphatemia in these patients appear to be independent of PTH, suggesting that other phosphaturic factors may play a role. However, further studies are needed to determine the nature of a phosphaturic factor and its relationship to the alterations of bone remodeling after transplantation.

Long-term effects on bone mineral density of pamidronate given at the time of renal transplantation

BACKGROUND

Fracture rate after renal transplantation is substantially increased, is a source of morbidity and mortality, and correlates with osteopenia. The rate of bone loss after transplantation is time dependent. While we recorded marked bone loss during the first year after renal transplantation, bone loss in long-term recipients (>24 months) was found to be similar to expected age-related decline. We have previously shown that treatment with pamidronate at the time of transplantation protected the skeleton over a 1-year study period.

METHODS

We have reexamined patients who participated in our original study, all of whom had been randomized to receive either placebo or pamidronate (0.5 mg/kg) at the time of transplantation and 1 month later. We now report 4-year data from 17 of the 26 original cohort. All patients received immunosuppression, comprising prednisolone, cyclosporine, and azathioprine.

RESULTS

We found that without prophylaxis bone loss at 4 years was substantial and significant at the femoral neck (mean loss was -12.3%) but was not significant at the lumbar spine (mean loss was -4.64%). Patients who received two doses of pamidronate experienced no statistically significant bone loss at either the femoral neck or the lumbar spine. Patient characteristics of the placebo and treatment groups were similar with the exception of serum parathyroid hormone concentrations, which remained higher at 4 years in the pamidronate-treated patients (15.8 +/- 3.7 pmol/L vs. 9.8 +/- 1.8 pmol/L, P < 0.05).

CONCLUSION

Without prophylaxis, most patients who continue to receive low dose glucocorticoids as part of maintenance immunosuppression manifest a substantial deficit in bone mineral density (BMD) at the femoral neck. In contrast, two doses of pamidronate given at the time of transplantation and 1 month later protected the skeleton from significant bone loss over the 4 years after transplantation.

Hyperphosphaturia after kidney transplantation in syngeneic rats: effects on nephrocalcinosis and bone metabolism?

BACKGROUND

Studies on kidney transplantation have thus far mainly dealt with surgical techniques, immunology, and transplant tolerance. Disturbed mineral metabolism after renal denervation has not received much attention. Basic physiological research in short-term experiments has shown that experimental renal denervation in rats leads to parathormone (PTH)-independent hyperphosphaturia (HPU). HPU and other metabolic complications also have been described after clinical kidney transplantation. Furthermore, there is an unexpected increase in the risk of bone fracture. However, these studies have examined an organism pre-damaged with regard to the parathyroid and immunosuppression. Experimental investigations in syngeneic rats were performed to see whether HPU also occurs after transplantation and thus after denervation and which target organs are involved.

METHODS

Thirty-six male Lewis rats subjected to laparotomy (n = 12), unilateral nephrectomy (n = 12), or unilateral transplantation and bilateral nephrectomy (n = 12) were observed for 18 weeks.

RESULTS

Animals that underwent transplantation had a significant loss of phosphate in the urine not associated with decreased calcium, phosphate, or magnesium in bone. Stability test showed no deterioration, despite a slight increase in the bone parameters of alkaline phosphatase, cyclic AMP, and hydroxyproline with unchanged calciotropic hormones. Nephrocalcinosis was not observed. Parallel to HPU, there was a compensatory reduction in fecal phosphate excretion.

CONCLUSIONS

The loss of phosphate after clinical kidney transplantation in the predamaged parathyroid hormone control system as well as immunosuppression and a surprising increase in the incidence of bone fractures may be explained by the denervation-related loss of phosphate. The lack of intestinal counter-regulation could be an important pathomechanism.

Bone disease in long-term adult kidney transplant patients with normal renal function

BACKGROUND

In successful renal transplantation, the degree of renal function recovery is usually incomplete and information is scarce about the abnormalities of mineral metabolism in long-term adult renal recipients with normal renal function. This study was designed to investigate bone mineral metabolism in patients with a long-term normal functioning kidney.

METHODS

Twenty-nine adult asymptomatic renal transplant (RT) recipients with stable graft function for more than 10 years and serum creatinine <2 mg/dL were studied. They were classified into two groups according to glomerular filtration rate: Group A (N = 12; nine men, three women)>70 mL/min (x: 126 +/- 55 mL/min) and Group B (N = 17; nine men, eight women) <70 mL/min (x: 56 +/- 11 mL/min). Circulating biochemical markers of bone remodelling, bone histomorphometry, and densitometry (lumbar spine and hip) were obtained to investigate bone disease in these patients.

RESULTS

Serum PTH was slightly elevated in 10 patients (83%) in group A. Serum PTH levels were positively related to serum calcium, osteocalcin, BAP, telopeptide, OH-proline, and creatinine. There was no histologic data to support overactivity on bone in this group of patients, with only one showing high bone turnover. Mineralization was prolonged in 34% of patients. Twenty-two patients (75%) exhibited normal bone turnover. In the group with GFR>70 mL/min the prevalence of mineralization defect in the presence of normal serum levels of calcitriol suggested vitamin D resistance. Lumbar and femoral neck osteoporosis was present in 25% and 33% of patients in group A, and 23% and 53% in group B, respectively. T-score at lumbar spine was negatively correlated with months since transplantation. Patients under treatment with cyclosporine (CsA) showed increased concentrations of osteocalcin and D-pyr and higher lumbar bone mineral density (BMD), but bone histomorphometry was not influenced by CsA.

CONCLUSION

Patients with long-term renal transplantation with normal renal function frequently present with slight increases in PTH, but without an effect on bone histology. CsA did not induce changes in bone histology and delayed mineralization was frequently observed.

Osteopenia and fractures in cystinotic children post renal transplantation

Many of the end-organ effects of cystinosis are known to be risk factors for osteopenia; these include deposition of cystine crystals in bone, hypothyroidism, diabetes mellitus, primary hypogonadism, urinary phosphate wasting, and chronic renal failure. While transplantation may correct the latter, it exposes the child to other risk factors for diminished bone mass, notably the use of high-dose glucocorticoids. Our objective was to determine if these multiple risk factors translate into an increased occurrence of osteopenia, as measured by dual-energy X-ray absorptiometry (DEXA), and/or fractures in this population. We examined the charts, X-rays, and bone mineral density (BMD) of all cystinotic patients post renal transplant for whom this information was available. Lumbar spine BMD was measured by DEXA scan (Hologic 4500). Z-scores were corrected for growth parameters using previously published reference data. Fracture history and pertinent serum markers of bone metabolism were also analyzed. Of the 63 renal transplants performed at our institution, 11 children were transplanted due to cystinosis. Nine of these patients, 5 male and 4 female, had had BMD evaluations, with an average age of 14.3 years (range 5-17 years) at the time of initial BMD post transplant. The mean interval between transplant and BMD evaluation was 39 months (range 3-90 months). Surprisingly, 7 of 9 patients had normal uncorrected BMD values (z-scores -1.92 to +0.02) and 7 of 9 patients had normal corrected values (z-scores -1.20 to +1.93). Three patients suffered from a total of eight fractures. Of the 3 fracture patients, 2 had normal BMD. All patients maintained good graft function and had normal calcium/phosphate mineral status. Of note, 3 of 5 male patients had evidence of primary testicular failure at earlier ages than often described, and this may be an unrecognized risk factor for bone disease in this population. Despite the numerous risk factors for developing osteopenia, these results suggest that the majority of cystinotic patients post renal transplant do not experience reduced bone mineral content as measured by DEXA. However, the significant fracture history among these patients demonstrates that DEXA cannot be used to assess fracture risk in patients with nephropathic cystinosis.

Bone disease after renal transplantation

Bone disease is common after renal transplantation. The main syndromes are bone loss with a consequent fracture rate of 3% per year, osteonecrosis of the hip, and bone pain. The causes of disease include preexisting uremic osteodystrophy (hyperparathyroidism, aluminum osteomalacia, beta2-associated amyloidosis, and diabetic osteopathy), postoperative glucocorticoid therapy, poor renal function, and ongoing hyperparathyroidism, as the result of either autonomous transformation of the parathyroid gland or ongoing physiologic stimuli. Cyclosporine A treatment, hyperphosphaturia, and a pathogenic vitamin D allele have also been implicated. Bone loss is particularly pronounced during the first year after operation, amounting to up to 9% of bone mass. The clinical and biochemical picture is consistent with a high turnover bone disease, but histomorphometric studies do not completely support this. Principal prophylactic options include preoperative osteodystrophy prophylaxis; postoperative calcium, vitamin D, or calcitriol therapy; estrogen therapy for postmenopausal women; and parathyroidectomy for medically intractable hyperparathyroidism. Recently, prophylactic biphosphonate treatment has shown promise, but the exact indications for treatment remain to be determined.

Bone mineral density changes within six months of renal transplantation

BACKGROUND

The effective use of new steroid-sparing immunosuppressive regimens may lower cumulative glucocorticoid use among renal transplant recipients. However, it is unknown what effect this therapeutic trend has had on bone disease.

METHODS

Unselected newly transplanted inpatients (n=45) were identified and comprehensively evaluated for metabolic bone disease at a median of 16 days (range 9-33) posttransplant. A follow-up evaluation was conducted a median of 5.7 months (range 4.8-9.3) later. Follow-up values for bone mineral density (BMD) and select laboratories were compared with baseline values using nonparametric statistics. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to describe the associations of baseline characteristics, select laboratory values, and cumulative prednisone and cyclosporine use with spinal BMD loss and were calculated using logistic regression.

RESULTS

A significant decrease in intact parathyroid hormone (P<0.001) and a significant increase in calcitriol (P=0.02) were noted postengraftment. At follow-up, subjects had lost a mean of 2.4% BMD at the lumbar spine (P=0.003) but did not experience significant declines at the femoral neck. The highest tertiles of cumulative prednisone (OR=28.4; 95% CI 2.5-329 and OR=15.8; 95% CI 1.4-179, respectively) and past alcohol use (OR=9.3; 95% CI 1.46-58.5) were significantly associated with spinal BMD loss.

CONCLUSIONS

Significant loss in lumbar BMD occurred within 6 months of transplantation in more than one third of a prospective cohort of renal transplant recipients. Lumbar bone loss seemed to be mediated primarily by glucocorticoid dose and a history of alcohol use.

Skeletal effects of cyclosporin A are gender related in rats

The immunosuppressive drug cyclosporin A (CsA) is thought to be involved in the pathogenesis of posttransplantation osteoporosis. To evaluate further the skeletal effects of CsA, we treated aged male and female sham-operated and gonadectomized rats with low doses of CsA for 4 months. Here, we show that CsA is antiresorptive and bone-sparing in aged female rats but increases bone resorption and reduces bone mass in aged male rats. However, even in male rats, CsA treatment, at clinically relevant doses, increased bone resorption only transiently and did not result in pronounced long-term cancellous bone loss. The gender-specific skeletal effects of CsA were not modulated by sex hormones or gonadectomy. CsA did not influence sex steroid metabolism in male or female rats. However, endogenous estradiol in sham-operated female rats (and especially, exogenous administration of 17beta-estradiol in ovariectomized rats) markedly diminished blood levels of CsA, probably by increasing hepatic CsA metabolism. Although the mechanism for the gender-specific skeletal effects of CsA is still obscure, our findings may have important implications for clinical therapy with CsA.

Immunosuppressant therapy and bone loss in ligature-induced periodontitis--a study in rats

Immunosuppressive agents have been recognized as a factor affecting the soft tissues of the periodontium. However, little is known about their effect on periodontitis progression. The aim of the present study was to investigate the influence of cyclosporin A (CsA) administration, associated or not with nifedipine, on the bone loss resulting from a ligature-induced periodontitis in rats. Twenty-four adult male Wistar rats were used. After anesthesia, the mandibular first molar was randomly assigned to receive the cotton ligature in the sulcular area while the contralateral tooth was left unligated. The animals were randomly assigned to one of the following treatments: Group A--saline solution; Group B--CsA (10 mg/kg); Group C--nifedipine (50 mg/kg); Group D--CsA (10 mg/kg) plus nifedipine (50 mg/kg). Forty-five days later, the animals were sacrificed and the specimens routinely processed for serial decalcified sections. Intergroup analysis did not reveal significant differences regarding the bone loss volume in the ligated teeth between the experimental treatments (0.46 +/- 0.11, 0.63 +/- 0.32, 0.53 +/- 0.14, 0.50 +/- 0.18, for groups A, B, C and D, respectively--p > 0.05). However, intragroup analysis showed a greater bone loss volume in the ligated teeth than in the unligated ones (p < 0.05). Within the limits of the present study, the conclusion was that the administration of CsA, associated or not with nifedipine, may not influence bone loss in ligature-induced periodontitis in rats.

Serum osteoprotegerin is a major determinant of bone density development and prevalent vertebral fracture status following cardiac transplantation

Osteoprotegerin (OPG) is an antiresorptive cytokine and a key regulator of osteoclastogenesis and activity. Since OPG is downregulated by glucocorticoids and cyclosporine A in vitro we examined whether immunosuppressive therapy would play a role in the development of transplantation osteoporosis. We enrolled 57 cardiac transplant recipients (median time since transplantation, 3.2 years (1.1-11.5 years)) in this cross-sectional study. Standardized spinal X-rays as well as hip bone density measurements were performed in all patients. Serum OPG was determined using a commercially available ELISA. Vertebral fractures were present in 56% of the patients. Bone densities of all femoral neck subregions were correlated to serum OPG concentrations (r values between 0.40 and 0.48, all P < 0.005). Multiple regression analysis revealed OPG levels to be independently correlated to femoral neck Z scores (r = 0.49, P = 0.002). After adjustment for age, BMI, neck Z score, renal function, and months since transplantation, serum OPG was the only significant predictor of prevalent vertebral fractures (P = 0.001). In a separate 6-month prospective study of 14 heart transplant recipients receiving calcium and vitamin D serum OPG levels fell by 41% (P = 0.0004) after 3 months and 47% (P = 0.0001) after 6 months following cardiac transplantation. Bone loss at the lumbar spine and femoral neck after 6 months was correlated to the decrease in serum OPG at 6 months (r = 0.82, P < 0.0001, and r = 0.60, P = 0.02, respectively) as well as 3 months after cardiac transplantation (r = 0.65, P = 0.01, and r = 0.69, P = 0.006, respectively). Serum OPG alone accounted for 67% of the variance of lumbar spine bone density changes over the first 6 months posttransplantation. We conclude that serum OPG levels decline consistently in all patients following initiation of immunosuppressive therapy and are independently correlated with changes in bone density. We hypothesize that OPG plays a major role in the development of transplantation osteoporosis.

Cyclosporine A-induced hypercalciuria in calbindin-D28k knockout and wild-type mice

BACKGROUND

It is known that cyclosporine A (CsA) treatment induces high bone-turnover osteopenia and hypercalciuria. It has been proposed that down-regulation of renal calbindin-D28k by CsA results in renal calcium wasting. We investigated the role of the kidney and bone in CsA-induced hypercalciuria in calbindin-D28k knockout (KO) and wild-type (WT) mice.

METHODS

Two sets of experiments were performed. In experiment 1, KO and WT mice were treated with CsA 20 mg/kg/day intraperitoneally (IP) for 7 days. In experiment 2, to eliminate the CsA effect on bone resorption, pamidronate (APD) 2.5 mg/kg IP was given every 4 days with the first dose given 4 days prior to the 7-day course of CsA. Serum levels of creatinine, calcium, and osteocalcin, as well as renal calcium excretion were measured to assess CsA's effects on calcium homeostasis. Effects of CsA on the expression of calbindin-D28k, and two calcium channels in the apical membrane of the distal tubule, epithelial calcium channel (ECaC) and alpha1G-subunit of a voltage-dependent Ca channel (alpha1G), in the kidney were examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

KO mice had a threefold increase in renal calcium excretion when compared with WT mice at the baseline. This difference disappeared when calcium load was reduced by overnight fasting. After the CsA treatment, both WT and KO mice had a significant increase of renal calcium excretion (urine Ca/Cr ratio in WT, 0.11 +/- 0.01 to 1.29 +/- 0.17; in KO, 0.39 +/- 0.04 to 1.18 +/- 0.13; both P < 0.01). CsA treatment decreased renal calbindin-D28k mRNA by 61%, but did not affect the expression of ECaC and alpha1G. Baseline serum osteocalcin level of KO mice was significantly lower than that of WT mice. After CsA treatment, both groups had a 50% increase in the serum osteocalcin level, indicating increased bone turnover. When mice were treated with both CsA and APD, the increase in serum osteocalcin level was prevented, and renal calcium excretion was significantly lower than that in mice treated with CsA alone. However, there was still a significant increase in the urine Ca/Cr ratio in WT and KO mice compared with pretreatment levels (urine Ca/Cr in WT, 0.11 +/- 0.01 to 0.76 +/- 0.05, P < 0.01; in KO, 0.39 +/- 0.05 to 0.79 +/- 0.06; P < 0.01).

CONCLUSION

Calbindin-D28k KO mice have diet-dependent hypercalciuria and a lower bone turnover rate. CsA treatment suppresses the expression of calbindin-D28k in mice, but has no effects on ECaC and alpha1G gene expression at the mRNA level. The pathogenesis of CsA-induced hypercalciuria involves both down-regulation of calbindin-D28k with subsequent impaired renal calcium reabsorption and CsA-induced high turnover bone disease. Additionally, our results suggest that mechanism(s) independent of calbindin-D28k within the kidney also may contribute to the CsA-induced calcium leak.

Risk factors for fractures in kidney transplantation

BACKGROUND

Risk factors for fracture after kidney transplantation need to be identified to target patients most likely to benefit from preventive measures.

METHODS

Medical records were reviewed for 1572 kidney transplants done at a single center between February, l963 and May, 2000 with 6.5+/-5.4 years of follow-up.

RESULTS

One or more fractures occurred in 300 (19.1%), with multiple fractures in 101 (6.4%). After excluding fractures of the foot or ankle (n=130 transplants, 8.3%), avascular necrosis (n=86, 5.5%), and vertebral fractures (n=28, 1.8%), there were one or more fractures in 196 (12.5%), with a cumulative incidence of 12.0%, 18.5%, and 23.0% at 5, 10, and 15 years, respectively. In multivariate Cox proportional hazards analysis, age had no effect on fractures in men. Compared with men and younger women, women 46-60 and >60 years old were, respectively, 2.11 (95% confidence interval 1.43-3.12, P=0.0002) and 3.47 (2.16-5.60, P<0.0001) times more likely to have fractures. Kidney failure from type 1 and 2 diabetes increased the risk by 2.08 (1.47-2.95, P<0.0001) and 1.92 (1.15-3.20, P=0.0131), respectively. A history of fracture pretransplant increased the risk by 2.15 (1.49-3.09, P<0.0001). Each year of pretransplant kidney failure increased the risk by 1.09 (1.05-1.14, P<0.0001). Obesity (body mass index >30 kg/m2) was associated with 55% (17-76%, P=0.0110) less risk. Different immunosuppressive medications, acute rejections, and multiple other factors were not independently associated with fractures.

CONCLUSIONS

The population of transplant patients at high risk for fracture can be identified using age/gender, pretransplant fracture history, diabetes, obesity, and years of pretransplant kidney failure.

Bone mineral density and height gain in children with chronic cholestatic liver disease undergoing transplantation

BACKGROUND

Osteodystrophy is a well-described complication of chronic liver disease. Previous reports in adults and children undergoing liver transplantation (LT) were discordant, with the former showing no improvement of bone disease in the first year after transplantation and the latter demonstrating remarkable benefit from it. Our aim was to perform a pilot study on osteodystrophy in children undergoing LT and evaluate the contribution of growth on bone mineral density (BMD) changes.

METHODS

We studied six patients (two male), with a median age at transplantation of 8.8 (range 3.8-16.6) years. Indications for transplantation were biliary atresia and progressive familial intrahepatic cholestasis (three patients each). BMD was studied with dual-energy x-ray absorptiometry and biochemical markers of liver and bone function in patients before and at 3, 6, and 12 months after LT.

RESULTS

Median L2-L4 spinal BMD was 0.54 g/cm2 (range 0.29-0.87) before LT, and 0.58 g/cm2 (0.27-0.86) at 3 months, 0.66 g/cm2 (0.36-1.00) at 6 months, and 0.76 g/cm2 (0.44-1.02) at 12 months after LT (P=0.005). Median height was 133 (range 93-167) cm before LT, and 134 (93-167) at 3 months, 136 (97-167) at 6 months, and 139 (102-167) at 12 months after LT. There was direct correlation between height gain and total body BMD improvement (r=0.929, P=0.007).

CONCLUSION

BMD in children with chronic cholestatic liver disease improves remarkably by 12 months after LT. Catch-up growth in children can account for the different effect of LT on bone density between adult and pediatric populations in the first year after surgery.

Periodontal changes in liver cirrhosis and post-transplantation patients. II: radiographic findings:

BACKGROUND

Liver disease and transplantation affect bone turnover. The role of cylosporin A (CsA) in aggravating bone loss is controversial. The aim of the present study was to examine the effect of liver cirrhosis, transplantation, and immunosuppressive therapy with either CsA or tacrolimus on alveolar bone height.

METHODS

The experimental group consisted of 13 liver cirrhosis (LC) patients. A second experimental group included 24 post-liver transplantation patients (PT) receiving CsA or tacrolimus. Seventeen healthy subjects formed a control group. Panoramic x-rays were taken and digitized using a computer-based measurement software to assess alveolar bone height of all available teeth.

RESULTS

Bone loss in the PT group (4.57+/-0.56 mm) was significantly higher than the control (C) (2.73+/-0.38 mm); however, it was significantly lower (P = 0.0005) than the LC (6.47+/-0.75 mm). Likewise, alveolar bone loss showed a trend for negative correlation (R = 0.404, P = 0.06) with the duration of immunosuppressive therapy post-liver transplantation.

CONCLUSIONS

Liver cirrhosis patients demonstrated greater bone loss compared to healthy controls. Restoration of liver functions following transplantation seems to have the potential to reverse some of these radiographic changes. Further longitudinal studies will be necessary to substantiate these findings.

A histomorphological investigation of the effect of cyclosporin on trabecular bone of the rat mandibular condyle

The effect of cyclosporin A (CSA) on the condylar trabecular bone was evaluated by microscopy. Twenty, 5-week-old male Sprague-Dawley rats were divided into a treated and a control group. Animals in the treated group received CSA, 15 mg/kg body weight, by gastric feeding daily for 4 weeks; controls received the vehicle only. Five animals from each group were killed at the end of weeks 2 and 4. After histological processing, 10 tissue sections from the mid-part of the mandibular condyle were examined. Generally, a histopathological osteopenia was observed around the condyle after CSA treatment, especially at the end of week 4. In the control animals, the trabecular bone volume steadily increased from weeks 2 to 4 (from 0.46+/-0.07 to 0.61+/-0.07 mm(3)/mm(3)). However, the bone volume was significantly less in the CSA group than in the control group at both times (0.33+/-0.02 vs 0.46+/-0.07 and 0.26+/-0.07 vs 0.61+/-0.07 mm(3)/mm(3) for CSA vs control group at the end of weeks 2 and 4, respectively). Conversely, an increased marrow volume was observed in the CSA group at both these times (0.60+/-0.02 vs 0.42+/-0.08 and 0.71+/-0.06 vs 0.31+/-0.06 mm(3)/mm(3) for CSA vs control group at the end of weeks 2 and 4, respectively). Decreases were also observed in trabecular thickness, osteoid seam width, osteoid volume and cortical bone width. Because trabecular bone mass, osteoid mass and cortical bone thickness all showed a decrease after CSA at both times, an inhibitory effect of CSA on trabecular bone formation in the mandibular condyle is proposed.

Bone disease after liver transplantation

1. Bone disease is a common problem in patients with chronic liver disease and liver transplants. 2. The cause of bone disease in these patients is multifactorial. 3. Bone disease worsens initially after liver transplantation, with subsequent improvement over time. However, bone disease in liver transplant recipients is common with long-term follow-up. 4. Evaluation of these patients should include metabolic and hormonal evaluations in conjunction with dual energy x-ray absorptiometry or bone mineral density evaluation. 5. Treatment with calcium, vitamin D, and hormonal supplements should be considered when appropriate for patients awaiting and after liver transplantation. The use of bisphosphanates and calcitonin also should be considered, although published studies in these populations are few in number.

Bisphosphonates in renal osteodystrophy

The present review considers the role that bisphosphonates might have in patients with renal failure. Although bisphosphonates are widely used to reduce fracture risk in patients with osteoporosis, few studies have documented their effect in patients with renal osteodystrophy. The pathogenesis of bone loss after renal transplantation and the role of the recently identified osteoprotegerin/receptor activating nuclear factor-kappaB system is described. Inhibition of bone resorption may prove beneficial when high bone turnover is present, but there are potential drawbacks to widespread use of bisphosphonates. These issues are discussed, with emphasis placed on reports published within the past 18 months.

[Immunosuppressive therapy and bone metabolism after kidney transplantation]

The success of transplant medicine due to improvements of immunosuppressive therapy has led to a significant increase of patient and organ survival. With the increasing number of transplantations, however, long term complications, often affecting the skeletal system, are becoming more frequent. Bone alterations often exist prior to transplantation in patients with chronic renal failure. There are two types of renal osteopathy, including "low-turnover bone disease", consisting of osteomalacia, and adynamic bone disease, and "high-turnover bone disease" due to the development of secondary hyperparathyroidism. Many patients show evidence of both disorders (mixed bone disease). During the first months after transplantation patients lose bone mass rapidly. One of the major factors responsible for the development of osteoporosis is thought to be the intensive immunosuppressive therapy during that period, steroids in particular seem to play an important role. To what extent other medications influence bone metabolism has not been established. Currently there are no studies about a standardized therapy and treatment relies mainly on experience with other forms of osteoporosis.

Cyclosporin-induced gingival overgrowth at the newly formed edentulous ridge in rats: a morphological and histometric evaluation

BACKGROUND

Since cyclosporin A (CsA)-induced overgrowth seldom occurs at sites distant from teeth, the periodontal ligament has been considered significant. The aim of this study was to examine overgrowth occurrence at the edentulous ridge--the sites without the ligament--after CsA therapy in rats.

METHODS

After extracting all right maxillary molars, 16 Sprague-Dawley rats underwent a 2-week healing period. The animals were separated into CsA and control groups. CsA rats received 15 mg/kg of CsA by gastric feeding for 4 weeks, while the control group received only mineral oil. At the end of study, all animals were sacrificed and stone models were immediately obtained by rubber-based impressions. The edentulous ridge morphology, including the bucco-lingual width and the vertical height, was measured on the models. For histometry, 10 sections were selected from the edentulous ridge of each animal after undecalcified tissue preparation. The soft tissue areas of the edentulous ridge and the trabecular bone morphology of the dental alveolus were measured.

RESULTS

CsA therapy produced a significant increase of the ridge width and height, measured from the stone models, when compared to the control group. Under histometry, CsA resulted in a significant increase of the epithelium, connective tissue, and total soft tissue areas. The measured trabecular bone volume was affected by both examining factors: the drug therapy and the location of the dental alveolus. CsA therapy produced a significant loss of bone volume but a significant increase of the bone-specific surface area. Although the mean osteoid volume was similar between CsA and control groups, a significant decrease of the fractional formation surface in the CsA group was revealed.

CONCLUSIONS

An enlarged edentulous ridge and an altered dental alveolar bone morphology were observed in CsA-treated animals at the end of the study; therefore, we suggest that CsA may induce not only a soft tissue overgrowth but also an alveolar bone alteration at the edentulous ridge. The hypothesis that tooth or periodontal ligament is an essential component for the overgrowth development is questioned.

Transforming growth factor-beta administration modifies cyclosporine A-induced bone loss

Cyclosporine A (CsA), a potent immunosuppressant used in transplantation, induces increased formation with excess resorption in the rat with resultant osteopenia. These findings are confirmed in the human model. Transforming growth factor-beta (TGF-beta) is reported to be involved in the coupling of bone formation with resorption and in vivo and in vitro stimulates osteoblasts, and in vitro inhibits osteoclasts. CsA stimulates secretion of TGF-beta1 in humans, which, while improving immunosuppression, may also contribute to renal toxicity. This study was performed determine whether exogenously administered TGF-beta would modify the bone effects of CsA. Male Sprague-Dawley rats, 6 months of age, were randomized to receive: TGF-beta and CsA vehicle (group A); TGF-beta 5 microg/kg three times per week and CsA vehicle (group B); TGF-beta vehicle and CsA 10 mg/kg (group C); or TGF-beta 5 microg/kg three times per week and CsA 10 mg/kg (group D). These were compared with control over 28 days. CsA, but not TGF-beta, increased serum 1,25(OH)(2)D levels throughout the study. CsA increased osteocalcin (BGP), but TGF-beta negated this effect. Histomorphometry confirmed the known effects of CsA, whereas TGF-beta alone had no effect. However, in combination, TGF-beta blocked CsA's effect and increased osteoblast recruitment and activity, as reflected by increased percent mineralizing surface, percent osteoid perimeter, bone formation rate (bone volume referent), and activation frequency. Thus, it appears as if TGF-beta administration may have potential in modulating the deleterious bone effects of CsA.

Effects of cyclosporin A on dental alveolar bone: a histomorphometric study in rats

BACKGROUND

We have previously reported cyclosporin A (CA)-induced osteopenia around the dental alveoli of the mandibular incisors of rats. The drug-induced tooth displacement and the regional anatomical complexity around the mandibular incisors might complicate the local effects of CA. Therefore, the purpose of this study was to evaluate the dental alveolar bone histomorphology around maxillary secondary molars in CA-treated rats and to further elucidate the effects of CA on the dental alveolus.

METHODS

Twenty Sprague-Dawley rats were assigned to a CA and a control group. Animals in the CA group received CA (15 mg/kg) daily and the control rats received only mineral oil. At the end of weeks 2 and 4, five animals in each group were sacrificed. Dental alveoli around the maxillary second molar region were frontally sectioned and stained with toluidine blue by undecalcified histological processing. Ten serial tissue sections, 80 microm apart, were selected for histometric evaluation. Bone volume, bone-specific surface, and osteoid formation were measured at buccal, apical, and palatal locations in dental alveolus.

RESULTS

Overall bone mass in dental alveolus decreased more in the CA group than in the control group at both observation intervals. All histometric measurements, except the bone-specific surface, were significantly affected by the alveolar location (palatal, apical, and buccal) and CA therapy (P= 0.004 and <0.001, 0.001 and <0.001, 0.004 and <0.001 for drug therapy and location of the dental alveolus in bone volume, marrow volume, and the ratio of bone surface to volume, respectively). Decreased bone volume, but increased marrow volume, were noted in the CA group compared to the control group. Although the alveolar bone surface area did not differ between the CA group and the control group, greater alveolar surface-to-volume ratio was noted in the CA group. For osteoid, more decreased volume, seam width, and fractional formation surface were observed in the CA group compared to the control group (P <0.001, <0.001, and = 0.046 in osteoid volume, seam width volume, and formation surface, respectively).

CONCLUSIONS

Because the bone mass and the osteoid formation in the dental alveolus around the maxillary molar region showed a decrease after CA exposure, we conclude that this drug has inhibitory effects on the dental alveoli.

Treatment of established bone loss after renal transplantation with etidronate

BACKGROUND

Osteoporosis is a well-documented complication of organ transplantation. Bisphosphonates have been shown to be effective in preventing corticosteroid-induced osteoporosis in renal transplant recipients, but data are lacking for treatment of established osteoporosis. This study reports our clinical experience of treatment with the bisphosphonate etidronate in a single renal transplant center.

METHODS

To establish the effectiveness of etidronate in treating established low bone mineral density (BMD), all newly transplanted patients treated with etidronate were compared with controls. Twenty-five patients treated with etidronate (14 males, 11 females) and 24 controls (15 males, 9 females) were identified from the cohort of patients who underwent transplantation between January 1, 1994, and December 31, 1996.

RESULTS

There was no difference in mean age, weight, or cumulative dose of corticosteroids between the treatment and control groups. The baseline BMD measurement was performed at 10.4 +/- 5.3 months after transplantation for treated patients and at 10.7 +/- 4.5 months for controls (P=0.78). Over the subsequent 1-year study period, patients treated with etidronate demonstrated a greater increase in BMD at sites with a preponderance of trabecular bone. Lumbar spine BMD increased 4.3 +/- 6.1% in the treatment group versus 0.55 +/ -5.3% in controls (P<0.03) and trochanter BMD increased 10.3 +/- 11.9% and 2.2 +/- 5.7%, respectively, in the treatment and control groups (P<0.02).

CONCLUSIONS

This study establishes the effectiveness of etidronate for treatment of low BMD in renal transplant recipients. Patients selected for treatment had lower baseline BMD than control subjects, yet still showed a clinically important increase in BMD.

Cyclosporin A affects extracellular matrix synthesis and degradation by mouse MC3T3-E1 osteoblasts in vitro

BACKGROUND

Immunosuppressant therapy is thought to be a major contributor to post-transplant bone disease. Histological data and serum parameters suggest that Cyclosporin A (CsA) treatment causes osteopenia as a result of an altered bone turnover, but the pathogenic mechanisms of this process remain unclear. We investigate if CsA affects cell turnover and extracellular matrix (ECM) synthesis and degradation in MC3T3-E1 osteoblasts, as a surrogate model for in vivo events.

METHODS

Cells were exposed to increasing doses of CsA (0, 0.5, 1 and 5 microg/ml). Proliferation was evaluated by bromodeoxyuridine (BrdU) incorporation, viability by Trypan Blue exclusion and apoptosis by ELISA. Type I collagen was measured by ELISA and reverse transcription-polymerase chain reaction (RT-PCR), matrix metalloproteinases (MMP) by zymography and RT-PCR, and tissue inhibitors of MMP (TIMP) by reverse zymography.

RESULTS

CsA exposure for 48 h decreased osteoblast number in a dose-dependent manner in the absence of apoptosis or cytotoxicity. CsA at a dose of 5 microg/ml for 72 h caused decreased collagen type I mRNA expression and protein accumulation. While MMP-2 remained unaffected, MMP-9 activity increased. TIMP-1 activity was unaffected, while a dose-dependent increase of TIMP-2 was observed.

CONCLUSIONS

These data suggest that CsA alters ECM synthesis and degradation in MC3T3-E1 osteoblasts by decreasing type I collagen production and increasing MMP-9 activity. The combination of increased MMP-9 with unchanged TIMP-1 activity could reduce the osteoid matrix available for mineralization. In addition, decreased proliferation could further reduce the number of cells synthesizing new osteoid matrix and thus contribute to the process of bone loss.

Transdermal oestrogen therapy protects postmenopausal liver transplant women from osteoporosis. A 2-year follow-up study

BACKGROUND/AIMS

Hormone replacement therapy (HRT) prevents osteoporosis in postmenopausal women by inhibiting bone resorption, but the benefits of oestrogen therapy in liver transplant patients have not been studied.

METHODS

The effect of transdermal HRT was studied in 33 postmenopausal liver transplant women. The main outcome measure was the change in bone mineral density (BMD) which was measured annually for 2 years. The effect on bone turnover was studied by assessment of the serum aminoterminal propeptide of type I procollagen (PINP).

RESULTS

The mean lumbar BMD increased from 0.816 at baseline to 0.858 and to 0.878 g/cm2 (P < 0.001) after 1 and 2 years of therapy, respectively. The BMD of the femoral neck increased from 0.665 to 0.690 g/cm2 (P < 0.006). During the first and second years, the mean BMD of the lumbar spine increased by 5.3 and 1.2%, while that of the femoral neck increased by 3.3 and 1.2%. After 2 years of HRT, only one-fifth of the patients had osteoporosis, whereas over half of the women had osteoporosis at baseline. The median serum PINP decreased by 47% at 1 year and remained decreased at 2 years compared with baseline levels.

CONCLUSION

Transdermal HRT decreased the turnover rate of mineralized bone matrix. Transplant women responded with increased BMD, just like healthy postmenopausal women.

Bone mass and mineral metabolism in liver transplant patients treated with FK506 or cyclosporine A

The purpose of this study was to compare the effects of Cyclosporine A (CyA) and FK506 on bone mass and mineral metabolism in liver transplantation (LT) patients. A prospective study was performed on 18 male patients who underwent LT treated with CyA, and 7 LT patients who received FK506. Bone mineral density (BMD) of the lumbar spine and proximal femur (DPX-L) was measured before and at 6, 12, and 24 months after transplantation. Moreover, intact parathyroid hormone (PTH) and 25-hydroxyvitamin D (25OHD) levels were determined at the same time. The cumulative dose of glucocorticoids was calculated in all patients. At 6 months, lumbar BMD decreased 5.2 +/- 1.2% (P = 0.0005) and 2.9 +/- 2.1% (p = ns) in CyA and FK506 groups, respectively. Lumbar BMD reached baseline values at 1 year in the FK506 group and 2 years after LT in the CyA group. Moreover, significant intergroup differences in femoral neck BMD changes after 2 years of transplant were observed (CyA: -5.2 +/- 1.97 versus FK506: +1.55 +/- 2.2%; P = 0.039). In the first year posttransplant both groups showed a marked increase in PTH and 25OHD levels. The mean cumulative dose of glucocorticoids was higher in the CyA group (CyA group 11.06 +/- 0.46 g versus FK 506 group 6.71 +/- 0.42 g; P < 0.001), and multiple linear regression analysis showed a negative correlation between BMD changes at the lumbar spine and mean cumulative dose of glucocorticoids (P = 0.022). In conclusion, our data suggest that after liver transplantation treatment with FK506 shows a more favorable long-term effect on bone mass evolution than CyA therapy. These differences seem to be associated with the lower dose of glucocorticoids used in the FK506 group.

The endothelin receptor antagonist, L-754,142 does not prevent cyclosporine A-induced osteopenia in rats

Cyclosporine A (CsA) is a potent immunosuppressive agent widely used to prevent allograft rejection. In vivo administration of CsA is associated with the development of high-turnover osteopenia. Endothelin-1 (ET), a vasoconstrictive peptide, has been implicated in CsA-induced nephrotoxicity and hypertension. Recent evidence suggests that endothelin plays a pivotal role in bone metabolism. The present study was designed to investigate whether L-754,142 (ETRA), the combined endothelin A and B receptor antagonist, when given to rats, would favorably modify the bone loss caused by CsA. Fifty, 5-month-old male Sprague-Dawley rats were randomly divided into five groups of 10 rats each. The first group served as a basal control. The remaining four groups received, by daily gavage for 28 days, (1) a combined CsA and ETRA vehicle, (2) CsA, 10 mg/kg, (3) ETRA, 30 mg/kg, and (4) CsA, 10 mg/kg and ETRA, 30 mg/kg, respectively. Rats were weighed and venous blood was collected on days 0, 14, 28 for determination of BUN, creatinine, calcium, PTH, osteocalcin, and 1,25(OH)2 D. Tibiae, after double labeling, were removed following sacrifice for histomorphometry. Both CsA-treated rats and CsA/ETRA-treated rats demonstrated trabecular osteopenia with raised serum osteocalcin, and 1,25(OH)2D levels when compared to control animals (P < 0.05). Rats given CsA alone developed renal impairment, as shown by an increased BUN. The combination group did not develop renal impairment. The results suggest that endothelin may contribute to the development of CsA-induced nephrotoxicity, which was prevented by ETRA, but does not seem to play a role in CsA-induced osteopenia.

Immunosuppressant use without bone loss--implications for bone loss after transplantation

Cyclosporine A (CsA) is associated with posttransplantation bone disease. Immunosuppressant drugs such as sirolimus (SRL), which are more potent and less deleterious than CsA, are being developed. Previous experiments have shown that SRL although immunosuppressive, is relatively bone sparing. The use of low doses of CsA and SRL in combination has displayed in vivo synergism. This study was initiated to examine the effect of low-dose CsA and SRL on bone metabolism, thereby hopefully providing a bone sparing immunosuppressive regimen for transplant recipients. One hundred and nineteen rats were divided into groups: basal, vehicle, CsA high dose, CsA low dose, SRL low dose, and combination low-dose CsA and SRL. The basal group was killed on day 0 for histomorphometry. The experimental groups were weighed and bled on days 0, 28, 56, and 84 and were killed on day 84 for histomorphometry. Serial assays for blood urea nitrogen (BUN), creatinine, and osteocalcin were performed. Osteocalcin was raised on days 28 and 56 in the high dose CsA group. Histomorphometry showed osteopenia with high-dose CsA. Low-dose CsA was relatively bone sparing, while low-dose SRL and combined low-dose CsA did not cause bone loss. In conclusion, the synergistic combination of low-dose CsA and SRL has the potential of providing both bone sparing and immunosuppressive benefits.

Post-transplant distal-limb bone-marrow oedema: MR imaging and therapeutic considerations

BACKGROUND

In recent years a previously unrecognized pain syndrome of the distal lower limbs after organ transplantation has been noted. A relationship to cyclosporin A was suspected, but no clear aetiology and pathogenesis have been established.

METHODS

During the last 30 months we diagnosed the pain syndrome in 10 patients after renal transplantation. We prospectively followed and evaluated the patients during their clinical courses and through pathological laboratory findings and magnetic resonance imaging (MRI).

RESULTS

In all patients symptoms developed within 6 months of transplantation after otherwise uncomplicated clinical courses without graft rejection episodes. Impressive bone-marrow oedema on MRI as well as elevated serum alkaline phosphatase was seen in all patients, and often exceeded the duration of clinical symptoms. All patients were instructed to avoid stress to the extremities through immobility, and steroid doses were tapered down. Within 14 weeks, eight patients were free of symptoms. Two patients have not experienced remission after 3 and 4 months respectively. None of the patients developed signs of osteonecrosis.

CONCLUSION

Post-transplant distal limb bone-marrow oedema presents with distinct clinical findings and signs of bone-marrow oedema on MRI. Proven standard treatment does not exist. In our experience the elevation of the extremities, the strict avoidance of physical strain, and a stepwise withdrawal of steroids facilitates progressive disappearance of symptoms. Long-term damage to the affected ostial structures has not been seen, in contrast to avascular femoral-head necrosis.

Bone loss after renal transplantation: role of hyperparathyroidism, acidosis, cyclosporine and systemic disease

In order to determine risk factors for bone loss after renal transplantation, dual energy X-ray absorptiometry was performed in 125 renal transplant patients. The bone mineral density (BMD) was expressed as a percentage of the normal population (BMD%) and Z-score (SD from normal). The whole body, lumbar spine and femoral neck BMD% (Z-score) values were 93.9 +/- 8.9 (-0.90 SD), 91.6 +/- 14.9 (-0.98 SD) and 87 +/- 15.3 (-1.0 SD)%, respectively. Low BMD% was associated with low creatinine clearance ( < 40 mL/min: 91.6 +/- 7.9, > 40 mL/min: 95.6 +/- 8.0, p < 0.01), repeated graft loss (0: 94.4 +/- 9.1, > 1: 87.4 +/- 9.3, p < 0.05), long dialysis duration ( < 1 yr: 95.2 +/- 7.9, > 5: 90.1 +/- 10.6, p < 0.05), acidosis (bicarbonate < 21 mmol/L: 89.6 +/- 8.0, > 27: 96.7 +/- 7.2, p < 0.01), secondary and tertiary hyperparathyroidism ( < 50 ng/L: 95.9 +/- 7.1, > 200: 87.7 +/- 5.0, p < 0.01), raised alkaline phosphatase ( < 200 units/L: 95.7 +/- 7.2, > 300: 85.6 +/- 13.2, p < 0.001), osteocalcin ( < 50 microg/L: 95.2 +/- 6.7, > 100: 89.3 +/- 7.6, p < 0.01) and urinary deoxypyridinoline (< 5 nM/mM creatinine: femoral neck 89.6 +/- 10.7, > 10: 82.1 +/- 20.1, p < 0.05), low 25-OH-vitamin D ( < 10 microg/L: 91.3 +/- 9.8, > 20: 96.9 +/- 7.4, p < 0.001) and high cyclosporine concentration (0 ng/L: 98.3 +/- 7.0, > 150: 92.1 +/- 9.3, p < 0.05). Patients with clinical atherosclerosis (91.7 +/- 8.6 vs. 95.4 +/- 8.8, p < 0.01), hypoalbuminemia ( < 550 micromol/L: 87.6 +/- 13.2, > 550: 94.2 +/- 7.8, p < 0.01), renovascular disease (89.7 +/- 5.7 vs. 95.0 +/- 5.7, p < 0.05) and diabetic nephropathy (femoral neck 76.6 +/- 8.8 vs. 89.3 +/- 15.1, p < 0.01) had lower bone masses. High bone mass was associated with previous dialysis alphacalcidol therapy (0: 92.2 +/- 7.5, > 3 microg/wk: 97.3 +/- 6.9, p < 0.05). No relationships with transplantation duration, 1,25-OH-vitamin D, aluminium, calcium or steroid dose were found. No involutional changes in tertiary hyperparathyroidism could be discerned.

CONCLUSION

The major threats to bone mass after renal transplantation appear to be ongoing hyperparathyroid bone disease, low renal function, acidosis, systemic disease and hypo-vitaminosis D.

Lesser reduction in bone mineral density by the immunosuppressant, FK506, compared with cyclosporine in rats

BACKGROUND

Posttransplantation osteopenia leading to osteoporosis induced commonly by treatment with immunosuppressants including cyclosporine (CsA) is a severe complication and results in lowering the quality of life in patients receiving organ transplantation. FK506 is a newly developed immunosuppressant and is currently being used for the prevention of rejection after organ transplantation. In this study, to investigate whether FK506 as well as CsA would cause osteopenia or not, we evaluated the effect of FK506 on bone mineral density and several parameters relevant to bone metabolism in comparison with that of CsA using normal rats.

METHODS

Ten-week-old male Sprague-Dawley rats were treated with FK506 (vehicle, 1 mg/kg, and 3.2 mg/kg) or CsA (vehicle, 10 mg/kg, and 32 mg/kg) by daily oral gavage for 28 days. Bone mineral density of the femur, plasma insulin-like growth factor I (IGF-I), and urinary deoxypyridinoline were determined by peripheral quantitative computerized tomography, radioimmunoassay, and enzyme-linked immunosorbent assay, respectively.

RESULTS

The reduction in bone mineral density of the femur was observed in both FK506- and CsA-treated rats. The reduction in CsA-treated rats, however, was statistically significant and strikingly severe, whereas that in FK506-treated rats was much less severe than CsA. Plasma IGF-I levels were significantly elevated in FK506-treated rats but not in CsAtreated rats. Urinary deoxypyridinoline levels were unchanged in FK506-treated rats but elevated in CsA-treated rats.

CONCLUSIONS

Compared with CsA, FK506 does not appear to induce severe osteopenia by high-turnover bone metabolism in the rat by mediating via IGF-I induction in part. The results suggest that FK506 may exert favorable effects on bone metabolism in patients with organ transplantation compared with CsA. To assess this idea, further clinical investigations focused on bone metabolism will be required.

Immunosuppression with FK506 increases bone induction in demineralized isogeneic and xenogeneic bone matrix in the rat

The aim of the present study was to investigate a systemic induction of bone formation in rats by immunosuppression with FK506 (1 mg/kg body weight intraperitoneally [ip]) in a model of osteoinduction of isogeneic and xenogeneic demineralized bone matrix (DBM) for a period of 28 days. In particular, alterations of in vitro cytokine synthesis and changes of lymphocyte subsets were studied. DBM was implanted intramuscularly in the abdominal wall of Lewis rats (seven per group). Blood was sampled on days -7, 0, 7, and 28 for determination of in vitro tumor necrosis factor a (TNF-alpha) synthesis and lymphocyte subsets by flow cytometry (CD3+, CD4+, CD8+, CD45+, ED9+, and Ia+ antibodies). Ossicles of de novo formed bone and the tibias were removed on day 28 after double tetracycline labeling for histomorphometric analysis. Immunosuppression with FK506 significantly decreased lipopolysaccharide (LPS)-stimulated in vitro cytokine synthesis after 7 days and 28 days (p < 0.05). Compared with control animals FK506 treatment significantly increased the volume of induced bone in isogeneic (2.1 +/- 0.3 mm3 vs. 10.8 +/- 0.9 mm3) and xenogeneic (O mm3 vs. 4.7 +/- 0.8 mm3) DBM. Bone histomorphometry of the tibias revealed that immunosuppression increased both bone formation and bone resorption, accompanied by a significant reduction in the relative trabecular area (Tb.Ar). FK506 caused a decrease in the counts of CD8+ T cells probably because of destruction or dislocation of these cells. This suggests that the amount of CD8+ cells and the degree of T cell activation in terms of mean fluorescence intensity (MFI) may be associated with bone metabolism. In support of this, statistical analysis revealed a significant positive correlation between parameters of bone formation as well as bone resorption and the CD4+/CD8+ ratio. There was a significant negative correlation between parameters of remodeling of the metaphysis of the tibia and induced bone volume (BV), respectively, and MFI values of CD3+/Ia+ cells. These findings suggest an important role of T lymphocytes in bone formation and bone resorption in vivo. FK506 caused a marked increase of bone formation in DBM. However, the conclusion that immunosuppression increases fracture healing warrants further investigation.

Bone mineral density in lung-transplant recipients before and after graft: prevention of lumbar spine post-transplantation-accelerated bone loss by pamidronate

BACKGROUND

Lung-transplant recipients are at risk of osteoporosis. They may have low bone mass even before posttransplantation immunosuppressive therapy. We studied bone mineral density (BMD) before and after lung transplantation and compared the efficacy of antiresorptive therapies to calcium and vitamin D supplementation.

METHODS

Areal BMD was assessed in 42 patients awaiting lung transplantation and measured again after surgery at 6 (n = 29), and at 12 months (n = 20). Nineteen patients received antiresorptive therapy (30 mg pamidronate IV every 3 months (n = 14), or hormonal replacement therapy (n = 5)), and 10 patients received only calcium and vitamin D supplements.

RESULTS

Mean age- and gender-adjusted lumbar spine (LS) and femoral neck (FN) BMD was significantly decreased prior to transplantation (- 0.6 +/- 0.2, p< 0.01, and - 1.5 +/- 0.2 standard deviation, p < 0.001, respectively). At that time, 29% were osteoporotic (T-score < - 2.5 below the peak bone mass), while 55% were below - 1.0 T-score. Antiresorptive therapy decreased the rate of LS bone loss during the first 6 months and led to a significant increase of BMD at 1 year, with LS changes of + 0.2 +/- 0.1 vs - 0.4 +/- 0.1 Z-score in the calcium-vitamin D group (p< 0.002), and + 0.2 +/- 0.1 vs - 0.04 +/- 0.1 for FN (NS). One out of 20 patients experienced clinically evident fractures during antiresorptive therapy, and 3 out of 12 in the calcium-vitamin D group.

CONCLUSION

A significant proportion of patients awaiting lung transplantation was osteoporotic or osteopenic. Antiresorptive therapy (pamidronate or hormone-replacement therapy (HRT)) prevented accelerated LS bone loss after graft.

Long-term care of the liver transplant recipient

Many liver transplant recipients are now reaching survival beyond 5 years from the liver transplant procedure, and many others are alive more than a decade from acquiring their new liver. Orthotopic liver transplant recipients enjoy the benefits of normal liver function, but a variety of metabolic and other medical problems often develop that require diagnosis and adequate management. These problems include hyperlipidemia, obesity, diabetes mellitus, renal disfunction, arterial hypertension, bone disease and neuropsychiatric syndromes. The gastroenterologist, internist, or local family physician is frequently called on to identify and treat these postoperative complications in conjunction with physicians at the transplant center.

Bone disease in patients with long-term renal transplantation and normal renal function

Renal osteodystrophy may persist during the early years after renal transplantation. However, information on bone status after a successful long-term renal transplantation is limited. We examined biochemical parameters, bone mineral density (BMD), and bone histomorphometry in 25 asymptomatic men with normal renal function after 7.5 +/- 5.7 years of a renal transplantation. Serum calcium, phosphorus, alkaline phosphatase, and 1,25(OH)(2)D(3) levels and urinary calcium level and cyclic andenosine monophosphate excretion were within normal range in all patients. Serum intact parathyroid hormone (PTH) level was elevated in 11 subjects (133.6 +/- 78 pg/mL) and normal in the other 14 subjects (47.9 +/- 13.6 pg/mL). Mean BMD at the lumbar spine and femoral neck was low in the entire group. However, it progressively increased as time after transplantation increased, approaching normal values after 10 years. Bone histomorphometric analysis showed bone resorption, osteoid volume, and osteoid surface greater than normal range in the majority of patients. Bone formation rate and mineralization surface were low, and mineralization time was delayed in most patients. These lesions were more severe in patients after 3 to 4 years of transplantation but improved with time and approached normal values after a period of 10 years. PTH values did not correlate with bone histological characteristics or BMD. These results show that the bone alterations observed after long-term renal transplantation consist of a mixed bone disease in which features of high bone turnover coexist with altered bone formation and delayed mineralization. These findings may result from the combined effect of preexisting bone disease and immunosuppressive therapy.

High prevalence of low bone turnover and occurrence of osteomalacia after kidney transplantation

Kidney transplantation corrects most of the metabolic abnormalities that cause renal osteodystrophy. However, many transplanted patients develop osteoporosis and other bone lesions that are related, at least in part, to their immunosuppressive regimen. The precise histologic patterns of bone disease after transplantation are not well defined. In a study designed to investigate this issue, 57 adult posttransplant patients agreed to undergo bone biopsies and blood drawings. There were 32 men and 25 women, mean age 45 +/- 2 yr, who had received a kidney transplantation 5.6 +/- 0.8 yr before biopsy. History of bone pain, fractures, and avascular necrosis was found in 22, 12, and 7 patients, respectively. Serum creatinine was 1.68 +/- 0.1 mg/dl, 21% of patients were hypercalcemic, 63.2% had elevated parathyroid hormone (PTH) (>65 pg/ml), and 91.2% had normal calcitriol levels. Cancellous bone volume/tissue volume was below normal compared to age- and gender-matched control subjects in 56.1% of patients. Bone turnover (activation frequency) was low in 45.6%, normal in 28.1%, and elevated in 26.3% of patients. Bone formation rate/bone surface was low in 59.7%, normal in 35%, and elevated in 5. 3% of the patients. Erosion surface/bone surface was high in 21.1% of patients. Mineralization was prolonged in 87.5% of patients, including 9 patients with osteomalacia and 12 patients with focal osteomalacia. Cumulative and maintenance doses of prednisone and time elapsed since transplantation correlated negatively with bone volume and bone turnover (r = -0.32 to -0.59, P < 0.05 to 0.01), whereas cumulative doses of cyclosporine or azathioprine, age, gender, or serum PTH levels did not. Regression analysis identified prednisone as the main factor responsible for low bone volume and bone turnover (r = 0.54 and r = 0.43, P < 0.01). No factors were found to predict delayed mineralization. The present study shows that low bone volume, low bone turnover, and generalized or focal osteomalacia are frequent histologic features in transplanted patients. The effects of age, gender, PTH, and cyclosporine on bone volume and bone turnover are apparently overridden by the prominent effects of glucocorticoids. The prevalence of mineralization defect in the presence of normal serum levels of calcidiol and calcitriol suggests vitamin D resistance and deserves further study.