The morphological association between microcracks and osteocyte lacunae in human cortical bone

We studied the spatial relationship between the osteocyte lacunar-canalicular network and microdamage accumulation in bone matrix. Rib sections from 9 white women aged 50-60 were stained with basic fuchsin and examined using bright-field and fluorescence microscopy. The results showed that the numerical and length density of cracks were 5-fold higher in interstitial bone than in osteons (P<0.001). Osteocyte lacunar density was 17% lower in interstitial bone than in osteonal bone (P<0.001). In addition, the osteocyte lacunae in interstitial bone were significantly fewer (by 16%) in the area adjacent to microdamage as compared with the area remote from microdamage (P<0.001). The proportion of fields with lacunar density less than 728/mm2, the cut-off point calculated from ROC analysis, was 30% in osteonal bone, 55% in interstitial bone remote from microcracks and 83% adjacent to microcracks. The mean values of lacunar density in these bones were 10%, 22% and 27% lower than the cut-off point, respectively. The likelihood of microdamage was 3.8 times higher in bone with osteocyte lacunar density <728/mm2. About 73% of the crack profiles were spatially associated, at least partly, with bone fragments in which osteocyte lacunae were absent. We conclude that microdamage and osteocyte deficiency occur in the same bone regions; there is likely a causal relationship between them but we are unable to say which comes first.

Severely suppressed bone turnover: a potential complication of alendronate therapy

Alendronate, an inhibitor of bone resorption, is widely used in osteoporosis treatment. However, concerns have been raised about potential oversuppression of bone turnover during long-term use. We report on nine patients who sustained spontaneous nonspinal fractures while on alendronate therapy, six of whom displayed either delayed or absent fracture healing for 3 months to 2 yr during therapy. Histomorphometric analysis of the cancellous bone showed markedly suppressed bone formation, with reduced or absent osteoblastic surface in most patients. Osteoclastic surface was low or low-normal in eight patients, and eroded surface was decreased in four. Matrix synthesis was markedly diminished, with absence of double-tetracycline label and absent or reduced single-tetracycline label in all patients. The same trend was seen in the intracortical and endocortical surfaces. Our findings raise the possibility that severe suppression of bone turnover may develop during long-term alendronate therapy, resulting in increased susceptibility to, and delayed healing of, nonspinal fractures. Although coadministration of estrogen or glucocorticoids appears to be a predisposing factor, this apparent complication can also occur with monotherapy. Our observations emphasize the need for increased awareness and monitoring for the potential development of excessive suppression of bone turnover during long-term alendronate therapy.

Analytical and clinical validation of the 25 OH vitamin D assay for the LIAISON automated analyzer

OBJECTIVE

Methods to assess serum 25 OH vitamin D have improved in accuracy, precision, and ease of use. We describe the analytical and clinical validation of an automated, antibody- and microparticle-based, chemiluminescent immunoassay method for the determination of 25 OH vitamin D.

DESIGN AND METHODS

The LIAISON 25 OH Vitamin D assay is a rapid automated method with first results available in 40 min, and a subsequent throughput of 180 samples per hour. Assay performance characteristics of precision and recovery were determined according to the National Committee for Clinical Laboratory Standards (NCCLS) protocols. Analytical and functional sensitivity were determined according to standard protocols. Samples for method comparison studies were obtained from routine clinical samples submitted for 25 OH Vitamin D determination or from apparently healthy normal volunteers.

RESULTS

The detection limit for this assay was <2.0 nmol/L across three lots of materials. Functional sensitivity (inter-assay imprecision <20%) was 17.5 nmol/L. Total imprecision (CV) was <15% at 42.5-137.5 nmol/L. Mean (SD) recovery was 101% (13%). The assay was linear on dilution. Comparison with radioimmunoassay (RIA) yielded acceptable correlation (r = 0.88) and clinical equivalence in the range from 37.5 to 150 nmol/L.

CONCLUSIONS

The LIAISON 25 OH Vitamin D assay is a rapid, accurate, and precise tool for the measurement of 25 OH vitamin D.

Randomized controlled clinical trial of surgery versus no surgery in patients with mild asymptomatic primary hyperparathyroidism

Parathyroidectomy is the definitive therapy for patients with symptomatic primary hyperparathyroidism. However, the role of surgery in mild asymptomatic primary hyperparathyroidism remains controversial. Accordingly, we conducted a prospective, randomized, controlled clinical trial of parathyroidectomy to determine the benefits of surgery vs. adverse effects of no surgery. Fifty-three patients were randomly assigned to either parathyroidectomy (n = 25) or regular follow-up (n = 28). Bone mineral density (BMD), biochemical indices of the disease, quality of life, and psychological function were measured at 6- or 12-month intervals for at least 24 months. Twenty-three of the 25 patients randomized to parathyroidectomy had surgery within the specified time of the protocol and three of the 28 patients randomized to regular follow-up had parathyroidectomy during follow-up. After parathyroidectomy, there was an increase in BMD of the spine (1.2%/yr, P < 0.001), femoral neck (0.4%/yr, P = 0.031), total hip (0.3%/yr, P = 0.07), and forearm (0.4%/yr, P < 0.001) and an expected fall in serum total and ionized calcium, serum PTH, and urine calcium (P < 0.001 for all). In contrast, patients followed up without surgery lost BMD at the femoral neck (-0.4%/yr, P = 0.117) and total hip (-0.6%/yr, P = 0.007) but gained at the spine (0.5%/yr; P = ns) and forearm (0.2%/yr, P = 0.047), with no significant changes in biochemical indices of disease. Consequently, a significant effect of parathyroidectomy on BMD was evident only at the femoral neck (a group difference of 0.8%/yr; P = 0.01) and total hip (a group difference of 1.0%/yr; P = 0.001) but not at the spine (a group difference of 0.6%/yr) or forearm (a group difference of 0.2%/yr). Quality-of-life scores as measured by a 36-item short-form health survey showed significant declines in five of the nine domains (social functioning, physical problem, emotional problem, energy, and health perception) in patients followed up without surgery but in only one of the nine domains (physical function) in the patients who had parathyroidectomy. Consequently, a modest measurable benefit of parathyroidectomy was evident in social and emotional role function (P = 0.007 and 0.012, respectively). Psychological function as assessed by the symptom checklist revised did not change significantly in either group, except for a significant decline in anxiety (P = 0.003) and phobia (P = 0.024) in patients who had surgery in comparison with those who did not. We conclude that it is feasible to conduct a randomized, controlled clinical trial of parathyroidectomy in patients with mild asymptomatic primary hyperparathyroidism, and measurable benefits of surgery on BMD, quality of life, and psychological function can be demonstrated. However, the small but significant benefits of parathyroidectomy must be weighed against the risks of surgery in these otherwise healthy individuals.

The mineralization index--a new approach to the histomorphometric appraisal of osteomalacia

The histomorphometric diagnosis of osteomalacia depends on the conjunction of two or three independent criteria but for several reasons, both clinical and pathophysiologic, it would be useful to have a single index of severity. Accordingly, using an extensive library of normal values in 143 healthy women, we constructed the mineralization index (MI), defined as [osteoid thickness (O.Th) (microm) + osteoid volume/bone volume (OV/BV) (%)] x 1.15 - osteoid mineralization rate (%/day) - [bone formation rate/bone surface (BFR/BS) (microm3/microm2/year) x 0.15]. MI was normally distributed with mean 8.0, SD 3.3, and range 0-15 (arbitrary units); it was unaffected by race, menopausal status, age or bone turnover, and was slightly lower in osteoporotic patients with nontraumatic vertebral fracture than in healthy white postmenopausal women (6.83 vs. 7.95). In hypovitaminosis D osteopathy (HVO) stage I, MI was normal in 18/26 cases (70%; HVOia), demonstrating more rigorously than before that osteoid accumulation is initially due entirely to secondary hyperparathyroidism and increased bone turnover. In the remaining 30% (HVOib), MI was increased, indicating the onset of impaired mineralization while bone formation was still increased and before the appearance of osteomalacia. In secondary hyperparathyroidism due to renal bone disease, 10/20 cases (50%) had normal MI and higher BFR than in HVOia (93 vs. 32), and there was a significant inverse correlation between MI and BFR. In patients with osteomalacia according to current criteria, MI ranged from 29.2 to 166.5; an MI of 30 had high sensitivity and specificity for the diagnosis of osteomalacia. Including all patients with HVO, there was a significant (P < 0.001) inverse correlation between MI and calcium x phosphate product, but the unexplained variance of >70% suggests that vitamin D deficiency impairs mineralization by multiple mechanisms. We conclude that the MI clarifies the early effects of vitamin D deficiency on bone and the relationship between different components of renal bone disease simplifies the histologic diagnosis of osteomalacia and may contribute to its management, and explicates the mechanisms of mineralization.

Management of vitamin d depletion in postmenopausal women

In the United States, the impact regarding the routine fortification of milk and other dairy products has been less than satisfactory in preventing vitamin D depletion in adults. As more individuals are being evaluated and treated for osteoporosis, it has become necessary to exclude vitamin D depletion as a cause, because of the likelihood that differences in vitamin D and calcium nutrition may modify the individual response to therapy. Increased prevalence of subclinical vitamin D depletion among vertebral and hip fracture patients and the beneficial effect of vitamin D therapy and calcium supplementation in preventing such fractures lend credence to this assumption. The prevalence of vitamin D depletion is increasing again, especially among older adults, precisely the group at greatest risk for osteoporotic fractures.

Reduced iliac cancellous osteocyte density in patients with osteoporotic vertebral fracture

Iliac cancellous osteocyte density declines with age, but its relationship to vertebral fracture pathogenesis is unknown. We performed iliac bone biopsy in 44 women with clinical vertebral fracture and 56 healthy women. The fracture patients had 34% fewer osteocytes but no reduction in percent occupied lacunae. Some patients destined to sustain vertebral fracture make cancellous bone with fewer osteocytes.

INTRODUCTION

Patient's with vertebral fracture have less bone than appropriate healthy controls, but other factors may contribute to bone fragility. Iliac cancellous osteocyte density declines with age in healthy women; we asked whether this variable differed between fracture patients and healthy controls.

METHODS

Two groups of women were assembled. Forty-four (mean age, 66.2 years) had unequivocal evidence of bone fragility manifested as painful nontraumatic vertebral fracture, and 56 (mean age, 62.2 years) were skeletally healthy. All subjects underwent iliac bone biopsy. From archival embedded biopsy cores, new sections were stained with Goldner's trichrome, in which we enumerated osteocyte-occupied lacunae (stained), empty lacunae (unstained), and total lacunae per bone area.

RESULTS

Cancellous osteocyte density was 34% lower in the fracture group than in the controls (p < 0.001); this difference was not a consequence of higher turnover, having less bone, or the small difference in age. The area under the receiver operating characteristic (ROC) curve for discrimination between the groups was >90% for osteocyte density and <75% for bone volume/tissue volume (BV/TV). The disease-related osteocyte deficit was accompanied by a proportionate reduction in empty lacunae and no change in percent occupied lacunae; therefore, it was not the result of premature death. Both superficial bone (<25 microm from the surface) and deep bone (>45 microm from the surface) were affected. In contrast, the age-related deficit is accompanied by an increase in empty lacunae and fall in percent osteocyte-occupied lacunae and occurs only in deep bone, but not in superficial bone.

CONCLUSIONS

In some patients destined to sustain spontaneous vertebral compression fracture, iliac cancellous bone is made with fewer osteocytes than normal; the mechanism of osteocyte incorporation into bone needs more detailed study. Osteocyte deficiency could contribute to bone fragility, either by impairing the detection of fatigue microdamage or by reducing canalicular fluid flow. Current practices of defining vertebral fracture based on morphometry alone regardless of symptoms, and diagnosing osteoporosis based on bone densitometry alone regardless of fracture history, should be reexamined.

Histomorphometric assessment of Haversian canal and osteocyte lacunae in different-sized osteons in human rib

There is no detailed information available concerning the variations in bone, the Haversian canal, and osteocyte populations in different-sized osteons. In this study a total of 398 secondary osteons were measured in archived rib sections from nine white men (20-25 years old). The sections were stained with basic fuchsin. The parameters included the osteon area (On.Ar), Haversian canal area (HC.Ar) and perimeter (HC.Pm), bone area (B.Ar), and osteocyte lacunar number (Lc.N). From these primary measurements the following indices were deduced: 1) lacunar number per bone area (Lc.N/B.Ar) and per osteon (Lc.N/On); 2) the ratio between Haversian canal perimeter and bone area (HC.Pm/B.Ar); and 3) the fraction of Haversian canal area (HC.Ar/On.Ar) and its complement, the fraction of bone area (B.Ar/On.Ar). The results showed that the osteons varied greatly in size, but very little in the fraction of bone area. Regression analyses showed that HC.Ar, HC.Pm, and Lc.N/On were positively associated with On.Ar (P < 0.001 for all). A significant negative correlation was found between On.Ar and Lc.N/B.Ar (P < 0.05) and HC.Pm/B.Ar (P < 0.0001). HC.Ar and HC.Pm increased significantly with increasing Lc.N/On (both P < 0.0001) rather than Lc.N/B.Ar. Lc.N/B.Ar had a significant positive correlation with HC.Ar/On.Ar (P < 0.05) and HC.Pm/B.Ar (P < 0.01). We conclude that: 1) the size of the osteon is determined by the quantum of bone removed by osteoclasts, 2) the osteon is well designed for molecular exchange, and 3) a well designed osteon may be produced via the regulation of bone apposition by osteocytes during the process of osteon refilling.

Forearm bone density in primary hyperparathyroidism: long-term follow-up with and without parathyroidectomy

OBJECTIVE

The long-term effects of primary hyperparathyroidism (PHPT), whether treated or untreated, on cortical bone are unclear, but the balance of evidence suggests that fracture risk is modestly increased in this patient group. We therefore compared changes in forearm cortical bone mineral density (BMD), at the site most relevant for PTH-mediated bone loss, in two groups of patients with PHPT; one with and one without surgery.

DESIGN AND PATIENTS

We followed the course of forearm bone mineral/bone width (BM/BW, g/cm2) measured by single-energy photon absorptiometry at the standard proximal site, and Z-scores (deviations from the mean value expected for age, sex and race, calculated from a large local reference population) in 108 patients who underwent successful surgery (mean duration 47 months, range 12-120 months) and 108 who remained unoperated (mean duration 52 months, range 12-132 months). Criteria for recommending surgery had been formulated in 1975 and were generally similar to those of the NIH consensus conference published in 1991. At the time of diagnosis the Z-score was significantly reduced in both groups, indicating an earlier period of accelerated cortical bone loss.

RESULTS

In the entire operated population there was no difference between the initial and final BM/BW. As the age-expected mean value declined, the Z-score became significantly less negative, and if the rate of change remained constant the values would have reached zero, indicating recovery of all bone lost as a result of the disease, after about 20 years. In the unoperated patients BM/BW fell significantly but there was no change in Z-score, indicating that the rate of bone loss was the same as expected for normal ageing.

CONCLUSIONS

It is reasonable to assume that cessation of further bone loss consequent on successful parathyroid surgery would eventually lead to abatement of the excess fracture risk, but the benefit to individual patients will depend mainly on their remaining life expectancy.

Randomized trial of parathyroidectomy in mild, asymptomatic primary hyperparathyroidism as measured by the SF-36 health survey

Background

Management of patients with asymptomatic primary hyperparathyroidism (HPT) remains controversial despite a National Institutes of Health consensus statement on this issue. As part of the above statement, a randomized clinical trial was recommended since none exist to address this issue.

Methods

Informed consent was obtained from 53 asymptomatic patients with confirmed primary HPT who agreed to participate in this randomized clinical trial of parathyroidectomy versus observation. Upon entry to the study and 24 months later the patients completed the SF-36 health survey which is an instrument that measures nine different levels of function. Scores were tabulated and the difference over 24 months between operated and non-operated patients was compared with Student's t test.

Results

Fifty-three patients (42 women and 11 men) with asymptomatic, mild primary HPT (serum calcium 10·1–11·5 mg dl−1) who agreed to participate were randomized into either a surgical group or an observation group. Mean serum calcium for these patients was 10·3 mg dl−1. The only demographic difference between the groups was age; the operated group was older (66·7 versus 62·6 years; P &lt; 0·03). Scores on three of the nine domains (health perception, emotional problems and social functioning) on the SF-36 were significantly different (P &lt; 0·05), all favouring the operated group.

Conclusion

Improved function, as measured by the SF-36 health assessment tool, is seen after parathyroidectomy compared with non-operated patients. This work supports surgical management of mild primary HPT at the time of diagnosis since many patients have reversible non-classical symptoms of the disease.

Relationships between osteocyte density and bone formation rate in human cancellous bone

Iliac cancellous osteocyte density decreases with age in deep bone but not in superficial bone, most likely because of remodeling. It has been suggested that osteocytes can inhibit bone remodeling. Accordingly, we examined the relationship between osteocyte density and bone formation rate in 92 healthy women. In superficial bone (<25 microm from the surface), we found a weak but significant (p < 0.03) inverse correlation between BFR/BS and Ot. N/B.Ar that was unaffected by menopause and independent of age. A weaker positive relationship with empty lacunar density improved significance. The data appear to suggest a negative feedback loop, but osteocytes explain only 10% of the variance in BFR/BS, and 97% of the variance in osteocyte density is explained by total lacunar density. This measure of initial osteocyte density during bone formation has a high coefficient of variation (20%) indicating large individual differences. We conclude that: (1) our data support the proposal that osteocytes can inhibit bone remodeling; (2) osteocyte density in superficial bone depends mainly on initial osteocyte density during bone formation and is maintained but not regulated by bone remodeling; and (3) the inverse relationship between BFR/BS and osteocyte density may reflect the homeostatic need to maintain calcium exchangeability in the lining cell-osteocyte syncytium.

Role of vitamin D and calcium nutrition in disease expression and parathyroid tumor growth in primary hyperparathyroidism: a global perspective

Since the classic description by Fuller Albright in the 1940s, primary hyperparathyroidism has evolved from a disease with classic signs and symptoms to a disease in search of symptoms! Since that time, two major events have occurred. First, in the United States, United Kingdom, and in most European countries, there has been a steady rise in the apparent incidence of the disease. Second, there has been a dramatic shift in the pattern of presentation. A majority of patients with primary hyperparathyroidism in countries with multichannel screening panels are asymptomatic. Skeletal and renal complications are uncommon, and osteitis fibrosa is rare. In contrast, the clinical presentation of primary hyperparathyroidism has changed very little in other regions such as the East, the Middle East, and some parts of the southern hemisphere over the same period of observation. Accordingly, we assessed the influence of vitamin D and calcium nutrition on the disease expression and parathyroid tumor growth in patients with primary hyperparathyroidism from different parts of the world. Between 1945 and 1950, both the prevalence of osteitis fibrosa and parathyroid tumor weight declined dramatically in the United States, coinciding with fortification of milk with vitamin D. In contrast, osteitis fibrosa and parathyroid tumor weight changed very little in parts of the world where vitamin D depletion is endemic. Furthermore, for a comparable degree of vitamin D depletion, Asian Indians have significantly larger tumors compared with Americans (3.95 +/- 2.23 vs. 0.66 +/- 2.84 g; p < 0.001). Within the United States, blacks have larger tumors compared with whites (0.78 +/- 2.87 vs. 0.58 +/- 2.78 g; p < 0.01). However, the slopes of regression between serum 25-hydroxyvitamin D, the best index of vitamin D nutrition, and parathyroid tumor weight, the best available index of parathyroid growth, were not significantly different between Asian Indians, whites, and blacks. We conclude that vitamin D and calcium nutrition of the population affect both the clinical expression and parathyroid tumor growth in patients with primary hyperparathyroidism. It will be of interest to see if the pattern of presentation of primary hyperparathyroidism changes when better nutritional policies are implemented in developing countries.

Age and distance from the surface but not menopause reduce osteocyte density in human cancellous bone

Previous studies of osteocyte density in human cancellous bone have relied mainly on autopsy samples and have demonstrated an age-related decline in men, but there are insufficient data in women. Using previously obtained transiliac bone biopsies from 94 healthy white women, aged 20-73 years, 38 premenopausal and 56 postmenopausal, we measured osteocytes and lacunae in ten randomly selected areas using 5-microm-thick sections stained with Goldner trichrome. For each subject, the number of osteocytes (Ot.N/B.Ar), empty lacunae (EL.N/B.Ar), and total lacunae (Tt.L.N/B.Ar) per bone area, and the proportion of occupied lacunae (Ot.N/Tt.L.N), were calculated. In 92 cases the measurements were made separately in superficial bone (<25 microm from the surface) and in deep bone (>45 microm from the surface). Mean values and differences between extreme values (DEV) for each variable were computed from the ten measured areas. In addition, confocal microscopic examination was performed on 100 microm sections. We found that Ot.N/B.Ar, Tt.L.N/B.Ar, and Ot.N/Tt.L.N decreased, but EL.N/B.Ar increased significantly with age (p < 0.001). The rates of decline were most rapid initially, falling exponentially with increasing age; the linear regressions for all four variables were significant in premenopausal, but not postmenopausal, women. At all ages, there were significantly more osteocytes in superficial than in deep bone; there was no significant decline with age in superficial bone, but a steeper exponential decline in deep bone than in whole trabeculae. DEV did not change with age for any variable. Confocal images revealed that the morphology of the osteocyte network was heterogeneous in different regions and trabeculae. The trabeculae with lower osteocyte density contained acellular areas, especially in interstitial bone. We conclude: (1) osteocyte density declines with age in women as it does in men; (2) the decline occurs exclusively in deep bone, not in superficial bone, suggesting that it is the age of the bone rather than the age of the subject that is important; (3) the rate of age-related decline falls exponentially with age and is not significant in postmenopausal women alone; (4) except for the differences between superficial and deep bone, the pattern of osteocyte distribution within and between trabeculae was not affected by age or menopause; and (5) the data raise the possibility that one function of remodeling in iliac cancellous bone is to maintain osteocyte viability.

Huntingtin interacting protein 1 Is a clathrin coat binding protein required for differentiation of late spermatogenic progenitors

Huntingtin-interacting protein 1 (HIP1) interacts with huntingtin, the protein whose gene is mutated in Huntington's disease. In addition, a fusion between HIP1 and platelet-derived growth factor beta receptor causes chronic myelomonocytic leukemia. The HIP1 proteins, including HIP1 and HIP1-related (HIP1r), have an N-terminal polyphosphoinositide-interacting epsin N-terminal homology, domain, which is found in proteins involved in clathrin-mediated endocytosis. HIP1 and HIP1r also share a central leucine zipper and an actin binding TALIN homology domain. Here we show that HIP1, like HIP1r, colocalizes with clathrin coat components. We also show that HIP1 physically associates with clathrin and AP-2, the major components of the clathrin coat. To further understand the putative biological role(s) of HIP1, we have generated a targeted deletion of murine HIP1. HIP1(-/-) mice developed into adulthood, did not develop overt neurologic symptoms in the first year of life, and had normal peripheral blood counts. However, HIP1-deficient mice exhibited testicular degeneration with increased apoptosis of postmeiotic spermatids. Postmeiotic spermatids are the only cells of the seminiferous tubules that express HIP1. These findings indicate that HIP1 is required for differentiation, proliferation, and/or survival of spermatogenic progenitors. The association of HIP1 with clathrin coats and the requirement of HIP1 for progenitor survival suggest a role for HIP1 in the regulation of endocytosis.

Sustained-release sodium fluoride in the treatment of the elderly with established osteoporosis

BACKGROUND

We ascertained the safety and efficacy of fluoride in augmenting spinal bone mass and reducing spinal fractures in older women with established osteoporosis. We compared a combination of sustained-release sodium fluoride, calcium citrate, and cholecalciferol (SR-NaF group) with calcium and cholecalciferol alone (control group).

METHODS

Eighty-five ambulatory women aged 65 years or older with 1 or more nontraumatic vertebral compression fractures were enrolled in a 42-month randomized, double-blind, placebo-controlled trial. Primary outcome measures were vertebral fracture rate, bone mass, and safety.

RESULTS

The vertebral fracture rate determined by means of computer assistance in the SR-NaF group was significantly lower than that in the control group (relative risk [RR], 0.32; 95% confidence interval [CI], 0.14-0.73; P =.007). Results of visual adjudicated inspection also confirmed a significant reduction in fracture rate (RR, 0.40; 95% CI, 0.17-0.95; P =.04). Bone mineral density in L2 through L4 increased significantly from baseline in the SR-NaF group by 5.4% (95% CI, 2.7%-8.2%; P<.001), and by 3.2% in the control group (95% CI, 0.8%-5.6%; P =.01). The between-group differences in bone mineral density were not significant. The femoral neck and total hip bone mineral density remained stable in the SR-NaF group and was not significantly different from that of the control group. There were no significant differences in adverse effects between groups.

CONCLUSION

The SR-NaF group significantly decreased the risk for vertebral fractures and increased spinal bone mass without reducing bone mass at the femoral neck and total hip.

Tissue specific metabolism of 1alpha,25-dihydroxy-20-epi-vitamin D3 into new metabolites with significant biological activity: studies in rat osteosarcoma cells (UMR 106 and ROS 17/2.8)

In a recent study, we investigated the metabolism of 1alpha,25-dihydroxy-20-epi-vitamin D3 (1alpha,25(OH)2-20-epi-D3), a potent synthetic vitamin D3 analog in the isolated perfused rat kidney and proposed that the enhanced biological activity of 1alpha,25(OH)2-20-epi-D3 is in part due to its metabolism into stable bioactive intermediary metabolites derived via the C-24 oxidation pathway (Siu-Caldera et al. [1999] J. Steroid. Biochem. Mol. Biol. 71:111-121). It is now well established that 1alpha,25(OH)2D3 and its analogs are metabolized in target tissues not only via the C-24 oxidation pathway but also via the C-3 epimerization pathway. As the perfused rat kidney does not express the C-3 epimerization pathway, we could not identify other possible bioactive metabolites of 1alpha,25(OH)2-20-epi-D3 such as 1alpha,25(OH)2-20-epi-3-epi-D3, derived via the C-3 epimerization pathway. Therefore, we studied the metabolism of 1alpha,25(OH)2-20-epi-D3 in rat osteosarcoma cells (UMR 106) which express both the C-24 oxidation and the C-3 epimerization pathways. Our results indicate that 1alpha,25(OH)2-20-epi-D3 is metabolized in UMR 106 cells into several metabolites which included not only the previously known metabolites of the C-24 oxidation pathway but also three new metabolites which were labeled as metabolites X, Y1, and Y2. Metabolite X was unequivocally identified as 1alpha,25(OH)2-20-epi-3-epi-D3. Even though definite structure identification of the metabolites, Y1 and Y2 was not achieved in our present study, we determined that the metabolite Y1 is produced from 1alpha,25(OH)2-20-epi-D3 and the metabolite Y2 is produced from 1alpha,25(OH)2-20-epi-3-epi-D3. We also noted the production of both 1alpha,25(OH)2-20-epi-3-epi-D3 and the two metabolites Y1 and Y2 in different rat osteosarcoma cells (ROS 17/2.8) which express only the C-3 epimerization pathway but not the C-24 oxidation pathway. Furthermore, we investigated the metabolism of 1alpha,25(OH)2-20-epi-D3 in the isolated perfused rat kidney in an earlier study. The results of this study indicated that the rat kidney unlike rat osteosarcoma cells did not produce either 1alpha,25(OH)2-20-epi-3-epi-D3 or the metabolites Y1 and Y2. Thus, it appears that the metabolites Y1 and Y2, like 1alpha,25(OH)2-20-epi-3-epi-D3, are produced only in specific tissues. Preliminary biological activity of each new metabolite is assessed by measuring its ability to generate VDR-mediated gene transcription. 1alpha,25(OH)2-20-epi-3-epi-D3 was found to be almost equipotent to 1alpha,25(OH)2-20-epi-D3 while the metabolites, Y1 and Y2 were found to be less active. The metabolite Y1 when compared to the metabolite Y2 has higher biological activity and its potency is almost equal to 1alpha,25(OH)2D3. In summary, we report for the first time tissue specific metabolism of 1alpha,25(OH)2-20-epi-D3 into several bioactive metabolites which are derived not only via the previously established C-24 oxidation and C-3 epimerization pathways but also via a new pathway. (c) 2001 Wiley-Liss, Inc.

Vasculogenic impotence. Arterial and venous surgery

Arterial revascularization and venous ligation procedures have been introduced within the past 2 decades. Each procedure has in common with the other the fact that initial applications of the operations were widespread among the population of men with vasculogenic erectile dysfunction. In each case, disappointing long-term results led to more limited use of surgery targeting specific groups that clearly would benefit from the procedures. The wider application of these procedures in vasculogenic erectile dysfunction is not supported by the available results. The Clinical Guidelines Panel of the American Urological Association supported this view in 1996 after a meta-analysis of literature reports and declared that venous and arterial surgery was not justified in routine use, especially in patients with arteriosclerosis. Further studies are likely to refine patient selection but are unlikely to expand the therapeutic use of these procedures.

Vascular endothelial growth factor restores corporeal smooth muscle function in vitro

PURPOSE

The therapeutic use of vasculogenic growth factors has been successfully demonstrated in models of organ ischemia. We determined whether vascular endothelial growth factor (VEGF) would reverse corporeal smooth muscle dysfunction in the hypercholesterolemic rabbit model of erectile dysfunction.

MATERIALS AND METHODS

A total of 36 New Zealand White rabbits were fed a normal (12) or 1% cholesterol (24) diet and treated after 6 weeks with 0.9 mg. VEGF or vehicle. At 6 weeks 24 rabbits received a single intracavernous dose and 12 received a single intravenous bolus of either drug. Ten days after injection corporeal smooth muscle function was analyzed after relaxation to acetylcholine and sodium nitroprusside using isometric tension studies. Corporeal sections were assessed for smooth muscle content with f-actin staining and VEGF expression by immunohistochemical study and enzyme-linked immunosorbent assay.

RESULTS

Endothelium dependent (acetylcholine) and nitric oxide mediated (sodium nitroprusside) smooth muscle relaxation were impaired in cholesterol fed animals (p = 0.021 and 0.003, respectively). Intracavernous VEGF treatment restored sodium nitroprusside mediated relaxation to normal (p = 0.015) and intravenous VEGF restored acetylcholine and sodium nitroprusside mediated relaxation (p = 0.014 and 0.018, respectively). Decreased smooth muscle content was noted in cholesterol fed animals versus normal diet controls (p = 0.008), which was not affected by VEGF treatment (p = 0.450). Corporeal endothelial cell content was increased after intracavernous but not intravenous VEGF treatment (p = 0.001 and 0.385, respectively). VEGF expression was augmented after treatment with recombinant VEGF (p <0.001).

CONCLUSIONS

VEGF administration variably mitigated the impairment of corporeal smooth muscle relaxation in the hypercholesterolemic rabbit model of erectile dysfunction.

The biological activities of 1alpha,25-dihydroxyvitamin D3 and its synthetic analog 1alpha,25-dihydroxy-16-ene-vitamin D3 in normal human osteoblastic cells and human osteosarcoma SaOS-2 cells are modulated by 17-beta estradiol and dependent on stage of differentiation

We compared the effects of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and its analog, 1alpha,25-dihydroxy-16-ene-vitamin D3 [1alpha,25(OH)2-16-ene-D3], as well as their interactions with 17-beta estradiol (E2) on osteoblastic function in our human normal (HOB) and osteosarcoma SaOS-2 cell models representing two different stages of differentiation, the more differentiated HOB+DEX cells and SaOS+DEX cells, and the corresponding less differentiated HOB-DEX and SaOS-DEX cells. The differential effects of 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-D3 and the modulation by E2 on ALP activity in HOB-DEX and HOB+DEX cells were small but significant. The most significant effects were seen in SaOS+DEX cells, in which 1alpha,25(OH)2-16-ene-D3 was 100-fold more potent than 1alpha,25(OH)2D3, the maximal enhancement being exerted at 0.1 nM and 10 nM, respectively. E2 enhanced the stimulatory effects of both compounds, with ALP being increased 2-fold at 0.1 nM (p<0.001). Osteocalcin (OC) production in HOB-DEX cells was stimulated 1.3 to 1.4-fold by 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-D3 at a concentration of 0.01 nM, with E2 inhibiting the effect of 1alpha,25(OH)2-16-ene-D3. In SaOS-DEX and SaOS+DEX cells, 1alpha,25(OH)2D3 and 1alpha,25(OH)2-16-ene-D3 stimulated OC production 1.6-fold at 0.1 nM with E2 slightly enhancing the effect of 1alpha,25(OH)2D3. Western blot analysis of 1alpha,25(OH)2D3 receptor (VDR) levels showed that in SaOS+DEX cells, the effect of 1alpha,25(OH)2D3 was larger than that of 1alpha,25(OH)2-16-ene-D3. These results show that 1alpha,25(OH)2-16-ene-D3 is biologically active in human osteoblasts.

Metabolism of 1alpha,25-dihydroxyvitamin D(3) in human promyelocytic leukemia (HL-60) cells: in vitro biological activities of the natural metabolites of 1alpha,25-dihydroxyvitamin D(3) produced in HL-60 cells

The secosteroid hormone, 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)], induces differentiation of the human promyelocytic leukemia (HL-60) cells into monocytes/macrophages. At present, the metabolic pathways of 1alpha,25(OH)(2)D(3) and the biologic activity of its various natural intermediary metabolites in HL-60 cells are not fully understood. 1alpha,25(OH)(2)D(3) is metabolized in its target tissues via modifications of both the side chain and the A-ring. The C-24 oxidation pathway, the main side chain modification pathway initiated by hydroxylation at C-24 leads to the formation of the end product, calcitroic acid. The C-23 and C-26 oxidation pathways, the minor side chain modification pathways initiated by hydroxylations at C-23 and C-26 respectively together lead to the formation of the end product, 1alpha,25(OH)(2)D(3)-lactone. The C-3 epimerization pathway, the newly discovered A-ring modification pathway is initiated by epimerization of the hydroxyl group at C-3 to form 1alpha,25-dihydroxy-3-epi-vitamin-D(3). We performed the present study first to examine in detail the metabolism of 1alpha,25(OH)(2)D(3) in HL-60 cells and then to assess the ability of the various natural intermediary metabolites of 1alpha,25(OH)(2)D(3) in inducing differentiation and in inhibiting clonal growth of HL-60 cells. We incubated HL-60 cells with [1beta-(3)H] 1alpha,25(OH)(2)D(3) and demonstrated that these cells metabolize 1alpha,25(OH)(2)D(3) mainly via the C-24 oxidation pathway and to a lesser extent via the C-23 oxidation pathway, but not via the C-3-epimerization pathway. Three of the natural intermediary metabolites of 1alpha,25(OH)(2)D(3) derived via the C-24 oxidation pathway namely, 1alpha,24(R),25-trihydroxyvitamin D(3), 1alpha,25-dihydroxy-24-oxovitamin D(3) and 1alpha,23(S),25-trihydroxy-24-oxovitamin D(3) [1alpha,23(S),25(OH)(3)-24-oxo-D(3)] were almost as potent as 1alpha,25(OH)(2)D(3) in terms of their ability to differentiate HL-60 cells into monocytes/macrophages. We then selected 1alpha,23(S),25(OH)(3)-24-oxo-D(3) which has the least calcemic activity among all the three aforementioned natural intermediary metabolites of 1alpha,25(OH)(2)D(3) to examine further its effects on these cells. Our results indicated that 1alpha,23(S),25(OH)(3)-24-oxo-D(3) was also equipotent to its parent in inhibiting clonal growth of HL-60 cells and in inducing expression of CD11b protein. In summary, we report that 1alpha,25(OH)(2)D(3) is metabolized in HL-60 cells into several intermediary metabolites derived via both the C-24 and C-23 oxidation pathways but not via the C-3 epimerization pathway. Some of the intermediary metabolites derived via the C-24 oxidation pathway are found to be almost equipotent to 1alpha,25(OH)(2)D(3) in modulating growth and differentiation of HL-60 cells. In a previous study, the same metabolites when compared to 1alpha,25(OH)(2)D(3) were found to be less calcemic. Thus, the findings of our study suggest that some of the natural metabolites of 1alpha,25(OH)(2)D(3) may be responsible for the final expression of the noncalcemic actions that are presently being attributed to their parent, 1alpha,25(OH)(2)D(3).

Highly active analogs of 1alpha,25-dihydroxyvitamin D(3) that resist metabolism through C-24 oxidation and C-3 epimerization pathways

The secosteroid hormone 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] is metabolized in its target tissues through modifications of both the side chain and the A-ring. The C-24 oxidation pathway, the main side chain modification pathway is initiated by hydroxylation at C-24 of the side chain and leads to the formation of the end product, calcitroic acid. The C-23 and C-26 oxidation pathways, the minor side chain modification pathways are initiated by hydroxylations at C-23 and C-26 of the side chain and lead to the formation of the end product, calcitriol lactone. The C-3 epimerization pathway, the newly discovered A-ring modification pathway is initiated by epimerization of the hydroxyl group at C-3 of the A-ring to form 1alpha,25(OH)(2)-3-epi-D(3). A rational design for the synthesis of potent analogs of 1alpha,25(OH)(2)D(3) is developed based on the knowledge of the various metabolic pathways of 1alpha,25(OH)(2)D(3). Structural modifications around the C-20 position, such as C-20 epimerization or introduction of the 16-double bond affect the configuration of the side chain. This results in the arrest of the C-24 hydroxylation initiated cascade of side chain modifications at the C-24 oxo stage, thus producing the stable C-24 oxo metabolites which are as active as their parent analogs. To prevent C-23 and C-24 hydroxylations, cis or trans double bonds, or a triple bond are incorporated in between C-23 and C-24. To prevent C-26 hydroxylation, the hydrogens on these carbons are replaced with fluorines. Furthermore, testing the metabolic fate of the various analogs with modifications of the A-ring, it was found that the rate of C-3 epimerization of 5,6-trans or 19-nor analogs is decreased to a significant extent. Assembly of all these protective structural modifications in single molecules has then produced the most active vitamin D(3) analogs 1alpha,25(OH)(2)-16,23-E-diene-26,27-hexafluoro-19-nor-D(3) (Ro 25-9022), 1alpha,25(OH)(2)-16,23-Z-diene-26,27-hexafluoro-19-nor-D(3) (Ro 26-2198), and 1alpha,25(OH)(2)-16-ene-23-yne-26,27-hexafluoro-19-nor-D(3) (Ro 25-6760), as indicated by their antiproliferative activities.

Randomized trial of parathyroidectomy in mild asymptomatic primary hyperparathyroidism: patient description and effects on the SF-36 health survey

BACKGROUND

The treatment of patients with asymptomatic primary hyperparathyroidism remains controversial despite a National Institutes of Health consensus statement. This statement also recommended a randomized clinical trial because none exists to address this issue.

METHODS

Informed consent was obtained from 53 asymptomatic patients with confirmed asymptomatic primary hyperparathyroidism who participated in this randomized trial of parathyroidectomy versus observation. Patients completed the SF-36 Health Survey, an instrument that measures wellness, every 6 months for 2 years. Average annual changes were compared.

RESULTS

Fifty-three patients (42 female, 11 male) with asymptomatic, mild (serum calcium level, 10.1-11.5 mg/dL) asymptomatic primary hyperparathyroidism who agreed to participate were randomized into either a surgical group or an observation group. The mean calcium level was 10.31 mg/dL. The only demographic difference between groups was age, with the operative group being older (66.7 vs 62.6 years; P <.03). The scores on 2 of the 9 domains of the SF-36 were significantly different (P <.007 and <.012, respectively); both favored the operative group.

CONCLUSIONS

Improved function is seen after parathyroidectomy when compared with patients who did not undergo operation. This study supports surgical management of mild primary hyperparathyroidism at the time of diagnosis because many patients have reversible nonclassic symptoms of the disease.