An immunoassay for type I collagen alpha 1 helicoidal peptide 620-633, a new marker of bone resorption in osteoporosis

Bisphosphonate Use May Reduce the Risk of Urolithiasis in Astronauts on Long‐Term Spaceflights

Long‐duration spaceflight is associated with an increased risk of urolithiasis, and the pain caused by urinary calculi could result in loss of human performance and mission objectives. The present study investigated the risk of urolithiasis in astronauts during 6 months on the International Space Station, and evaluated whether the suppression of bone resorption by the bisphosphonate, alendronate (ALN), can reduce the risk. A total of 17 astronauts were included into the analysis: exercise using the advanced resistive exercise device (ARED) plus weekly oral 70 mg alendronate (ARED+ALN group, n = 7) was compared to resistive exercise alone (ARED group, n = 10). Urine volume decreased in both groups during spaceflight but recovered after return. The ARED group showed increased urinary calcium excretion from the 15th to 30th day of spaceflight, whereas urinary calcium was slightly decreased in the ARED+ALN group. Urinary N‐terminal telopeptide (NTX) and helical peptide (HP) of type I collagen, as bone resorption markers, were elevated in the ARED group during and until 0 days after spaceflight, while there was no elevation in these parameters in the ARED+ALN group. Urinary oxalate and uric acid excretion tended to be higher in the ARED group than in the ARED+ALN group during spaceflight. These results demonstrate that astronauts on long‐duration spaceflights may be at high risk for the formation of urinary calcium oxalate and calcium phosphate stones through increased urinary excretion of oxalate and uric acid, from degraded type I collagen, as well as of calcium from enhanced bone resorption. Our findings suggest that increased bone resorption during spaceflight, as a risk factor for urinary calculus formation, could be effectively prevented by an inhibitor of bone resorption. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Bone turnover: Biology and assessment tools

Bone turnover includes two processes: resorption (removal of old bone) and formation (laying down of new bone). N-terminal propeptide of type I procollagen (PINP) and C-telopeptide of type I collagen (CTX-I) are markers of bone formation and resorption, respectively, that the International Osteoporosis Foundation and the International Federation of Clinical Chemistry recommend for clinical use. Bone turnover markers (BTM) are subject to sources of variability, including feeding (lower resorption) and recent fracture (increased levels of all markers). Controllable patient-related factors should be adapted as much as possible (eg blood collection after an overnight fast) to minimize pre-analytical variability. Uncontrollable factors should be considered in the interpretation of the BTM measurements. BTM do not improve prediction of bone loss or fracture within an individual. In osteoporotic patients, BTM may help to assess the response to anabolic and antiresorptive therapies, to assess compliance to the treatment, or to indicate possible secondary causes of osteoporosis. BTM reflect changes in bone metabolism induced by anti-osteoporotic treatment. Anti-resorptive drugs induce a rapid dose-dependent decrease in bone resorption, whereas bone formation stimulating medications increase the levels of bone formations markers. BTM may be used for monitoring anti-osteoporosis therapy. The expected effect during the anti-resorptive therapy is to decrease the PINP by at least 10 ng/mL and to attain the target level of less than 35 ng/mL. The expected effect during the bone formation-stimulating therapy is to increase the PINP by at least 10 ng/mL and to attain the target level of more than 69 ng/mL.

The selective cathepsin K inhibitor MIV-711 attenuates joint pathology in experimental animal models of osteoarthritis

BACKGROUND

MIV-711 is a highly potent and selective cathepsin K inhibitor. The current article summarizes the therapeutic effects of MIV-711 on joint pathology in rabbits subjected to anterior cruciate ligament transection (ACLT), and the prophylactic effects on joint pathology in dogs subjected to partial medial meniscectomy, two surgical models of osteoarthritis (OA).

METHODS

Starting 1 week after surgery, rabbits were dosed daily via oral gavage with either MIV-711 or vehicle (n = 7/group) for 7 weeks. The four treatment groups were: (1) sham + vehicle; (2) ACLT + vehicle; (3) ACLT + MIV-711, 30 µmol/kg and (4) ACLT + MIV-711, 100 µmol/kg. Subchondral bone and articular cartilage structures were assessed by µCT, histomorphometry, and scoring. Dogs subjected to partial medial meniscectomy received either MIV-711 (30 µmol/kg) or vehicle (n = 15/group) via oral gavage once daily, starting 1 day before meniscectomy, for 28 days. Cartilage degradation was assessed at the macroscopic and microscopic levels. The exposures of MIV-711 were assessed in both studies and biomarkers reflecting bone resorption (HP-1 in rabbits, CTX-I in dogs) and cartilage degradation (CTX-II) were measured.

RESULTS

In ACLT rabbits, MIV-711 decreased HP-1 levels by up to 72% (p < 0.001) and CTX-II levels by up to 74% (p < 0.001) compared to ACLT vehicle controls. ACLT surgery significantly reduced the total thickness of the subchondral bone plate and reduced trabecular bone volume in the femur and tibia. These effects were reversed by MIV-711. ACLT resulted in cartilage thickening, which was attenuated by MIV-711. MIV-711 did not affect osteophyte formation or Mankin scores. In dogs, MIV-711 reduced CTX-I and CTX-II levels by 86% (p < 0.001) and 80% (p < 0.001), respectively. Synovial CTX-II levels were reduced by 55-57% (p < 0.001) compared to baseline. MIV-711-treated animals had 25-37% lower macroscopic scores in the femur condyles and 13-33% lower macroscopic scores in the tibial plateaus.

CONCLUSIONS

MIV-711 prevents subchondral bone loss and partially attenuates cartilage pathology in two animal models of OA. These beneficial effects of MIV-711 on joint pathology are observed in conjunction with decreases in bone and cartilage biomarkers that have been shown to be clinically attainable in human. The data support the further development of MIV-711 for the treatment of OA.

Odanacatib, effects of 16-month treatment and discontinuation of therapy on bone mass, turnover and strength in the ovariectomized rabbit model of osteopenia

Odanacatib (ODN) a selective and reversible cathepsin K inhibitor, inhibits bone resorption, increases bone mass and reduces fracture risk in women with osteoporosis. A 16-month (~7-remodeling cycles) study was carried out in treatment mode to assess the effects of ODN versus ALN on bone mass, remodeling status and biomechanical properties of lumbar vertebrae (LV) and femur in ovariectomized (OVX) rabbits. This study also evaluated the impact of discontinuing ODN on these parameters. Rabbits at 7.5months post-OVX were dosed for 16-months with ODN (7.5μM·h_0-24, in food) or ALN (0.2mg/kg/wk, s.c.) and compared to vehicle-treated OVX- (OVX+Veh) or Sham-operated animals. After 8months, treatment was discontinued in half of the ODN group. ODN treatment increased in vivo LV aBMD and trabecular (Tb) vBMD until reaching plateau at month 12 by 16% and 23% vs. baseline, respectively, comparable levels to that in Sham and significantly above OVX+Veh. LV BMD was also higher in ALN that plateaued around month 8 to levels below that in ODN or Sham. ODN treatment resulted in higher BMD, structure and improved biomechanical strength of LV and central femur (CF) to levels similar to Sham. ALN generally showed less robust efficacy compared to ODN. Neither ODN nor ALN influenced material properties at these bone sites following ODN or ALN treatment for 7 remodeling cycles in rabbits. ODN and ALN persistently reduced the bone resorption marker urinary helical peptide over study duration. While ALN reduced the bone formation marker BSAP, ODN treatment did not affect this marker. ODN also preserved histomorphometry-based bone formation indices in LV trabecular, CF endocortical and intracortical surfaces, at the levels of OVX+Veh. Discontinuation of ODN returned bone mass, structure and strength parameters to the comparable respective levels in OVX+Veh. Together, these data demonstrate efficacy and bone safety profile of ODN and suggests the potential long-term benefits of this agent over ALN with respect to accrued bone mass without long-term effects on bone formation.

Better Osteoporotic Fracture Healing with Sintered Dicalcium Pyrophosphate (SDCP) Treatment: A Rat Femoral Fracture Model

The aim of this study was to evaluate the effect of sintered dicalcium pyrophosphate (SDCP) on fracture healing in an osteoporotic rat model. Female Sprague-Dawley rats (8 weeks old) were randomly allocated into five groups: sham-operated group, and bilateral ovariectomized group treated with SDCP, alendronate, calcitonin, or no treatment. Rats were sacrificed at 6 or 16 weeks after fracture. Fracture sites were examined by microcomputed tomography (microCT), histology, and mechanical testing. The results showed that SDCP mildly suppressed callus remodeling at 6 weeks, but not at 16 weeks. The lamellar bone in the callus area and new cortical shell formation in SDCP-treated group were similar to that of the sham group at 16 weeks after fracture, indicating there was no delayed callus remodeling into lamellar bone. At both 6 and 16 weeks after fracture, ultimate stress and elastic modulus were similar between the SDCP and sham groups, and the mechanical strength in these groups was better than that in other groups. Finally, analysis of the serum bone markers CTX-1 and P1NP suggested that SDCP decreased the bone turnover rate and promoted proper fracture healing. The effect of SDCP is superior to that of alendronate and calcitonin in the healing of osteoporotic fractures.

Study of the distribution by age group of serum cross-linked C-terminal telopeptide of type I collagen and procollagen type I N-propeptide in healthy Japanese women to establish reference values

Osteoporosis prevention is an important public health goal. Bone turnover markers are clinically measured to assess bone strength. C-terminal telopeptide of type I collagen (CTX) is released when collagens degrade and serves as an indicator of bone resorption. Simple CTX immunoassays are now available. However, serum CTX (sCTX) reference ranges for Japanese women are lacking. Procollagen type I N-propeptide (intact P1NP) reflects osteoblast activity, serving as a marker of bone formation. Because sCTX and intact P1NP are clinically applied as bone turnover markers, we determined reference ranges for both sCTX and intact P1NP in healthy Japanese women. We collected 228 blood samples from healthy Japanese women aged 19-83 years, grouped by age and menopausal status. We measured sCTX and intact P1NP and examined their correlation. sCTX values differed significantly between the two consecutive decade groups encompassing 19-39 years of age, intact P1NP values between 20 and 30 s, between post-menopausal 50 and 60 s, and between pre-and post-menopausal women in their 50 s. The mean sCTX of 91 healthy pre-menopausal women was 0.255 (0.100-0.653) ng/mL, the intact P1NP in 90 women 33.2 (17.1-64.7) μg/L. Corresponding values for post-menopausal women were 0.345 (0.115-1.030) ng/mL and 41.6 (21.9-79.1) μg/L. sCTX correlated with intact P1NP. Bone resorption markers are measured to assess anti-resorption agents, bone formation markers to assess the effects of bone-forming agents. The sCTX and intact P1NP reference values determined herein, in healthy Japanese women, are expected to be useful for osteoporosis treatment, assessment of fracture risk, and other clinical applications.

Inhibition of cathepsin K reduces cartilage degeneration in the anterior cruciate ligament transection rabbit and murine models of osteoarthritis

OBJECTIVE

To investigate the disease modifying effects of cathepsin K (CatK) inhibitor L-006235 compared to alendronate (ALN) in two preclinical models of osteoarthritis (OA).

METHODS

Skeletally mature rabbits underwent sham or anterior cruciate ligament transection (ACLT)-surgery and were treated with L-006235 (L-235, 10 mg/kg or 50 mg/kg, p.o., daily) or ALN (0.6 mg/kg, s.c., weekly) for 8-weeks. ACLT joint instability was also induced in CatK(-/-) versus wild type (wt) mice and treated for 16-weeks. Changes in cartilage degeneration, subchondral bone volume and osteophyte area were determined by histology and μ-CT. Collagen type I helical peptide (HP-I), a bone resorption marker and collagen type II C-telopeptide (CTX-II), a cartilage degradation marker were measured.

RESULTS

L-235 (50 mg/kg) and ALN treatment resulted in significant chondroprotective effects, reducing CTX-II by 60% and the histological Mankin score for cartilage damage by 46% in the ACLT-rabbits. Both doses of L-235 were more potent than ALN in protecting against focal subchondral bone loss, and reducing HP-I by 70% compared to vehicle. L-235 (50 mg/kg) and ALN significantly reduced osteophyte formation in histomorphometric analysis by 55%. The Mankin score in ACLT-CatK(-/-) mice was ~2.5-fold lower than the ACLT-wt mice and was not different from sham-CatK(-/-). Osteophyte development was not different among the groups.

CONCLUSION

Inhibition of CatK provides significant benefits in ACLT-model of OA, including: 1) protection of subchondral bone integrity, 2) protection against cartilage degradation and 3) reduced osteophytosis. Preclinical evidence supports the role of CatK as a potential therapeutic target for the treatment of OA.

Critical analysis of biomarkers in the current periodontal practice

Periodontal disease is a chronic microbial infection that triggers inflammation-mediated loss of the periodontal ligament and alveolar bone that supports the teeth. Because of the increasing prevalence and associated comorbidities, there is a need for the development of new diagnostic tests that can detect the presence of active disease, predict future disease progression, and evaluate the response to periodontal therapy, thereby improving the clinical management of periodontal patients. The diagnosis of active phases of periodontal disease and the identification of patients at risk for active disease represent challenges for clinical investigators and practitioners. Advances in diagnostic research are moving toward methods whereby the periodontal risk can be identified and quantified by objective measures using biomarkers. Patients with periodontitis may have elevated circulating levels of specific inflammatory markers that can be correlated to the severity of the disease. Advances in the use of oral fluids as possible biological samples for objective measures of the current disease state, treatment monitoring, and prognostic indicators have boosted saliva- and other oral-based fluids to the forefront of technology. Gingival crevicular fluid (GCF) is an inflammatory exudate that can be collected at the gingival margin or within the gingival crevice. This article highlights recent advances in the use of biomarker-based disease diagnostics that focus on the identification of active periodontal disease from plaque biofilms, GCF, and saliva.

Bone turnover and type I collagen C-telopeptide isomerization in adult osteogenesis imperfecta: associations with collagen gene mutations

INTRODUCTION

Increased bone fragility in osteogenesis imperfecta (OI) is not totally accounted for by decreased bone mineral density (BMD), and alterations of type I collagen (Col I) are believed to play a role. Newly synthesized Col I comprises non isomerized C-telopeptide (alphaCTX), but with bone matrix maturation alphaCTX is converted to its isomerized beta form (betaCTX). Urinary alpha/betaCTX ratio has been proposed to reflect collagen maturation. We investigated changes in bone turnover and Col I isomerization in adult patients with OI and their relationship with Col I gene mutations.

PATIENTS AND METHODS

Sixty four adult patients [25 women, 39 men mean age (SD): 36.2 (11.6) years] with OI participating in a randomized study and 64 healthy controls of similar age and gender distribution were investigated. In patients with OI and controls, we measured the following biochemical markers of bone metabolism: serum type I collagen N-propeptide (PINP) an index of Col I synthesis, osteocalcin a marker of osteoblastic activity, urinary Col I helical peptide, a marker reflecting the degradation of the helical portion of Col I, urinary alphaCTX and urinary and serum betaCTX. Based on the putative functional effects of Col I gene mutations which were identified in 56 OI subjects, patients were divided in those with haploinsufficiency (n=29), patients presenting with helical domain alterations (n=17) and others (n=10).

RESULTS

Compared to healthy controls, patients with OI had decreased levels of PINP (-22.7%, p<0.0001), increased osteocalcin (+73%, p<0.0001) and increased Col I helical peptide (+58%, p=0.0007). Urinary alphaCTX was increased (+31%, p=0.03) whereas urinary (-15%, p=0.022) and serum (-9.9%, p=0.0056) betaCTX were significantly decreased, resulting in a 49% (p<0.001) higher urinary alpha/betaCTX ratio. Patients with Col I gene mutations resulting in haploinsufficiency had lower PINP levels than patients with helical domain alterations (26.4+/-15.3 vs 41.6+/-27.4 ng/ml, p=0.0043) and controls (p<0.01).

CONCLUSION

Adults with OI are characterized by decreased Col I synthesis - especially those with haploinsufficiency mutations - increased Col I degradation and decreased Col I C-telopeptide isomerization.

Mechanisms of the anabolic effects of teriparatide on bone: insight from the treatment of a patient with pycnodysostosis

Pycnodysostosis is an extremely rare genetic osteosclerosis caused by cathepsin K deficiency. We hypothesized that teriparatide, a potent anabolic agent used in the treatment of osteoporosis, might reduce skeletal fragility by activating bone turnover. We studied a typical case of pycnodysostosis in a 37-yr-old woman who exhibited short stature, skull and thorax deformities, and a history of severe fragility fractures. Cathepsin K gene sequencing was performed. Before and after 6 mo of 20 microg/d teriparatide, biochemical markers of bone turnover were measured, and 3D bone structure and microarchitecture was assessed in vivo by HR-pQCT. Qualitative and quantitative analysis of transiliac bone biopsies were performed, and the degree of mineralization was evaluated by quantitative microradiography. In vitro assessment of bone resorption was performed after separation and differentiation of CD14(+) monocytes from peripheral blood. Bone structure assessed by HR-pQCT on the radius and tibia showed augmentation of cortical and trabecular density. Transiliac bone biopsy showed highly increased bone mass (+63% versus age- and sex-matched controls), a decrease in bone remodeling without evidence of active osteoblasts, and a severe decrease in the dynamic parameters of bone formation (mineralizing surfaces, -90% and bone formation rate, -93% versus age- and sex-matched controls). This depressed bone turnover probably explained the increased degree of mineralization. The presence of a novel missense mutation leading to an A141V amino acid substitution confirmed a genetic defect of cathepsin K as the cause of the disease. The deficiency of active osteoclasts was confirmed by an in vitro study that showed a decreased concentration of CD14(+) monocytes (the precursor of osteoclasts) in blood. These osteoclasts had low resorptive activity when incubated on bone slices. After 6 mo of teriparatide, the structure, microarchitecture, and turnover of bone--assessed by HR-pQCT, histology, and bone turnover markers--remained unchanged. Our data strongly suggest that some features of the osteoclastic phenotype--that are absent in pycnodysostosis--are a prerequisite for the anabolic effect of PTH on osteoblasts.

HGF inhibits BMP-induced osteoblastogenesis: possible implications for the bone disease of multiple myeloma

The bone disease in multiple myeloma is caused by an uncoupling of bone formation from bone resorption. A key difference between patients with and patients without osteolytic lesion is that the latter have fewer and less active osteoblasts. Hepatocyte growth factor (HGF) is often produced by myeloma cells and is found at high concentrations in the bone marrow of patients with multiple myeloma. Here we show that HGF inhibited bone morphogenetic protein (BMP)-induced in vitro osteoblastogenesis. Thus, HGF inhibited BMP-induced expression of alkaline phosphatase in human mesenchymal stem cells (hMSCs) and the murine myoid cell line C2C12, as well as mineralization by hMSCs. Furthermore, the expression of the osteoblast-specific transcription factors Runx2 and Osterix was reduced by HGF treatment. HGF promoted proliferation of hMSCs, and the BMP-induced halt in proliferation was overridden by HGF, keeping the cells in a proliferative, undifferentiating state. BMP-induced nuclear translocation of receptor-activated Smads was inhibited by HGF, providing a possible explanation of how HGF inhibits BMP signaling. The in vitro data were supported by the observation of a negative correlation between HGF and a marker of osteoblast activity, bone-specific alkaline phosphatase (rho = -0.45, P = .008), in sera from 34 patients with myeloma. These observations suggest that HGF inhibits bone formation in multiple myeloma.

Non-enzymatic glycation of bone collagen modifies osteoclastic activity and differentiation

Type I collagen, the major organic component of bone matrix, undergoes a series of post-translational modifications that occur with aging, such as the non-enzymatic glycation. This spontaneous reaction leads to the formation of advanced glycation end products (AGEs), which accumulate in bone tissue and affect its structural and mechanical properties. We have investigated the role of matrix AGEs on bone resorption mediated by mature osteoclasts and the effects of exogenous AGEs on osteoclastogenesis. Using in vitro resorption assays performed on control- and AGE-modified bone and ivory slices, we showed that the resorption process was markedly inhibited when mature osteoclasts were seeded on slices containing matrix pentosidine, a well characterized AGE. More specifically, the total area resorbed per slice, and the area degraded per resorption lacuna created by osteoclasts, were significantly decreased in AGE-containing slices. This inhibition of bone resorption was confirmed by a marked reduction of the release of type I collagen fragments generated by the collagenolytic enzymes secreted by osteoclasts in the culture medium of AGE-modified mineralized matrices. This effect is likely to result from decreased solubility of collagen molecules in the presence of AGEs, as documented by the reduction of pepsin-mediated digestion of AGE-containing collagen. We found that AGE-modified BSA totally inhibited osteoclastogenesis in vitro, most likely by impairing the commitment of osteoclast progenitors into pre-osteoclastic cells. Although the mechanisms remain unknown, AGEs might interfere with osteoclastic differentiation and activity through their interaction with specific cell-surface receptors, because we showed that both osteoclast progenitors and mature osteoclasts expressed different AGEs receptors, including receptor for AGEs (RAGEs). These results suggest that AGEs decreased osteoclast-induced bone resorption, by altering not only the structural integrity of bone matrix proteins but also the osteoclastic differentiation process. We suggest that AGEs may play a role in the alterations of bone remodeling associated with aging and diabetes.

Assessment of urinary N-telopeptide: Point-of-care testing, sample types, and relationship to urinary helical peptide excretion

BACKGROUND

A point-of-care (POC) device would be useful in the space program for measuring N-telopeptide (NTX), a marker of bone resorption. This study was done to establish whether NTX measurements from a POC device compare favorably with standard (ELISA) techniques. We also compared results from fresh and frozen urine samples, samples collected on consecutive days, and second voids (of the day) and 24-h urine pools. Helical peptide (HP), another crosslink, was compared in second voids and 24-h urine pools.

METHODS

Ten subjects collected urine for 96 h. NTX was measured with the POC device and by ELISA, and HP measured by ELISA. Seven subjects collected 24-h urine pools, and samples were analyzed fresh and after 27 days of freezing.

RESULTS

Excretion of NTX was greater (P<0.05) when measured by the POC device than when measured by ELISA, but was not different between second voids and 24-h urine pools, or among days. HP was similar in second voids and 24-h pools. Less NTX (P<0.05) was found in fresh 24-h pools [mean (S.D.) values, 38.4 (11.6) and 33.6 (9.2) nmol/mmol creatinine for the POC device and ELISA] than in previously frozen 24-h pools [42.7 (17.4) and 41.5 (12.5) nmol/mmol creatinine for the POC device and ELISA].

CONCLUSIONS

Comparisons between NTX measurements from frozen and fresh samples and those analyzed by POC and ELISA techniques should be made with caution.

Diagnosis of renal osteodystrophy

The idiom renal osteodystrophy (ROD) represents a heterogeneous pattern of bone disturbances caused by chronic renal insufficiency and concomitant diseases. For the clinical decision of therapy it is most important to differentiate between high and low or adynamic turnover ROD because the therapeutically consequences of these two ends of the ROD spectrum are fundamentally different. Bone histology remains the gold standard for the exact classification of ROD. Serological markers of bone metabolism are not suited for the accurate nomenclature of ROD but are useful for the sequential follow up of ROD after a clear diagnosis has been made. Similarly, radiological diagnosis of ROD using dual energy X-ray absorptiometry (DEXA) or quantitative computer tomography scan (q-CT) is inaccurate and thus more suited for the routine follow up of established disease. Besides mineralization, bone strength and the rate of fractures are strongly determined by the architecture of the bone matrix. This information, however, is also only available on bone biopsy sections and cannot be estimated by non-invasive diagnostic methods. In summary, bone biopsy should be used more liberally for correct classification of bone disease. The sequential follow up and guidance of therapy success can be performed by non-invasive procedures such as biochemical bone marker determination in blood. X-ray imaging and densitometry is suitable only for sequential evaluation of osteoporosis.

Bone markers and current laboratory assays

Metastasis of cancer to bone leads to significant alterations in normal bone remodelling that are reflected in changes in bone turnover markers. These markers are classically defined as markers of bone resorption or formation; markers of bone resorption are measures of osteoclastic activity, whereas markers of bone formation are measures of osteoblastic activity. Recently, there has been growing interest in the use of these markers in metastatic bone disease (MBD), and an increasing number of studies have investigated the potential use of these markers in diagnosis, monitoring of disease progression and treatment, and prediction of outcome. In this review, we briefly discuss the biology of bone metastases as well as describe the bone turnover markers and their possible role in aiding clinicians in the treatment of patients with MBD.

Diagnostic biomarkers for oral and periodontal diseases

This article provides an overview of periodontal disease diagnosis that uses clinical parameters and biomarkers of the disease process.This article discusses the use of biomarkers of disease that can be identified at the tissue, cellular, and molecular levels and that are measurable in oral fluids such as saliva and gingival crevicular fluid. Biomarkers identified from these biologic fluids include microbial, host response, and connective tissue-related molecules that can target specific pathways of local alveolar bone resorption. Future prospects for oral fluid-based diagnostics that use micro-array and microfluidic technologies are presented.

Osteoporosis, a unitary hypothesis of collagen loss in skin and bone

Progress in osteoporosis has been stultified by repetitive, statistic-driven studies and catechistic reviews; in the absence of concept and hypothesis research is aimless, and the trivial associations it continually reveals, has led to the cul-de-sac of multifactorialism. A return to hypothesis-led research which seeks major causal defects and the conclusive therapies that arise from them is essential. The hypothesis proposed evolved from research into the mechanism of senile purpura. This predicted a causal loss of skin collagen that was contrary to contemporary opinion, but was confirmed when collagen was expressed absolutely, instead as a percentage or ratio: women have less collagen than men and it decreases by 1% a year in exposed and unexposed skin. Corticosteroids (which also produce shear purpura) reduce skin collagen and androgen and virilism increase it; growth hormone produces the greatest increase, and there is a decrease in hypopituitarism. All these changes in skin collagen correspond to changes in bone density, and the circumstances are too various for coincidence. This led to the hypothesis that the changes found in skin collagen also occur in bone collagen, leading to the associated changes in bone density; thus a loss of collagen in skin and bones with aging is the causal counterpart to loss of bone density in senile osteoporosis. If this is correct then, as with aging, androgen and virilisation, corticosteroids, growth hormone and hypopituitarism, changes in bone density should correspond to systemic changes in skin collagen. This correspondence is found to occur in osteogenesis imperfecta and Ehlers-Danlos syndrome, two genetically discrete families of disordered collagen production, and other situations, e.g., scurvy and homocystinuria. A primary loss of collagen in osteoporotic bones is an essential prediction of the hypothesis; in fact this loss is well established but, inexplicably, it has been assumed to be secondary to the bone loss. Because of the comparable changes in skin and bones, the hypothesis implies that skin collagen could be used to predict the state of the bones and their response to treatment. It also implies androgen should be an effective treatment of osteoporosis, and growth hormone even more effective (likewise, of course, skin aging). More importantly, skin collagen and the production of collagen by skin fibroblasts could be used for the assay and industrial development of more potent, if not less toxic treatments and prevention of loss of bone (and skin) substance.

Excretion of collagen derived peptides is increased in women with stress urinary incontinence

AIMS

The objective of this study was to demonstrate that weakened pelvic floor support of the lower genitourinary tract in women with stress urinary incontinence (SUI) is due to increased collagenolysis. When fibrillar collagen is degraded, pyridinium (PYD) crosslinks are released and excreted in the urine. Degradation of collagen also results in peptide fragments of various lengths which are excreted in the urine. Degradation of mature fibrillar collagen and collagen which has not been crosslinked can be assessed independently by measurement of both PYD and collagen-derived peptides in the urine.

METHODS

Twenty-four hour urine collections were obtained from women with SUI (n = 23) and women without urinary incontinence (n = 39). Urinary PYD concentration was assayed by ELISA. The urinary concentration of helical peptide alpha1 (I) 620-633 fragments derived from collagen was assayed by competitive enzyme immunoassay. Values were normalized to creatinine.

RESULTS

The mean urine PYD concentration for women with SUI (110.8 +/- 19.7 nM/mM creatinine) was not significantly different than that for women without SUI (85.2 +/- 13.7 nM/mM creatinine). The mean urine concentration of helical peptide alpha1 (I) 620-633 for women with SUI (0.80 +/- 0.13 microg/mg creatinine) was significantly (P < 0.02) higher than that for women without SUI (0.49 +/- 0.06 microg/mg creatinine).

CONCLUSIONS

These data suggest that collagenolytic activity in women with SUI is elevated compared to continent controls, as measured by urinary helical peptide alpha1 (I) 620-633 excretion. The lack of difference in urinary PYD excretion between the two populations suggests that the increased collagenolytic activity in women with SUI, compared to continent controls, is restricted to uncrosslinked collagen.