Identification of the first homozygous intragenic deletion in the YY1AP1 gene in a consanguineous family: New insights into the phenotypic variability associated with Grange syndrome.

Grange syndrome (GRNG-MIM#135580) is a rare recessive disorder associating variable features including diffuse vascular stenosis, brachysyndactyly, osteopenia with increased bone fragility, cardiac malformations, and variable developmental delay. Since its first description in 1998, only 15 individuals from 10 families have been reported, carrying homozygous or compound heterozygous frameshift or nonsense variants in YY1AP1. In a patient with cutaneous and bone syndactyly and a hemorrhagic stroke at the age of 16 months, consistent with a clinical diagnosis of GRNG, we performed exome sequencing after negative array-CGH and congenital limb malformation panel results. Copy number variant analysis from exome data identified a homozygous intragenic out-of-frame deletion of 1.84 kb encompassing exons seven and eight of YY1AP1, confirming a molecular diagnosis of GRNG. Genetic counseling led to the identification of additional family members compatible with GRNG. Here, we provide new insights into the phenotypic variability associated with GRNG and highlight the utility of the detection of small copy number variants to identify the molecular causes of heterogeneous malformative genetic disorders.

Cost of exome analysis in patients with intellectual disability: a micro-costing study in a French setting.

BACKGROUND: With the development of next generation sequencing technologies in France, exome sequencing (ES) has recently emerged as an opportunity to improve the diagnosis rate of patients presenting an intellectual disability (ID). To help French policy makers determine an adequate tariff for ES, we aimed to assess the unit cost per ES diagnostic test for ID from the preparation of the pre-analytical step until the report writing step and to identify its main cost drivers. METHODS: A micro-costing bottom-up approach was conducted for the year 2018 in a French setting as part of the DISSEQ study, a cost-effectiveness study funded by the Ministry of Health and performed in collaboration with the GAD (Génétique des Anomalies du Développement), a genetic team from the Dijon University Hospital, and a public sequencing platform, the Centre National de Recherche en Génomique Humaine (CNRGH). The analysis was conducted from the point of view of these two ES stakeholders. All of the resources (labor, equipment, disposables and reagents, reusable material) required to analyze blood samples were identified, collected and valued. Several sensitivity analyses were performed. RESULTS: The unit nominal cost per ES diagnostic test for ID was estimated to be €2,019.39. Labor represented 50.7% of the total cost. The analytical step (from the preparation of libraries to the analysis of sequences) represented 88% of the total cost. Sensitivity analyses suggested that a simultaneous price decrease of 20% for the capture kit and 50% for the sequencing support kit led to an estimation of €1,769 per ES diagnostic test for ID. CONCLUSION: This is the first estimation of ES cost to be done in the French setting of ID diagnosis. The estimation is especially influenced by the price of equipment kits, but more generally by the organization of the centers involved in the different steps of the analysis and the time period in which the study was conducted. This information can now be used to define an adequate tariff and assess the efficiency of ES. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT03287206 on September 19, 2017.

Clinical Reliability of point-of-care tests to support community based acute ambulatory care.

OBJECTIVE: To ensure clinicians can rely on point-of-care testing results, we assessed agreement between point-of-care tests for creatinine, urea, sodium, potassium, calcium, Hb, INR, CRP and subsequent corresponding laboratory tests. PARTICIPANTS: Community-dwelling adults referred to a community-based acute ambulatory care unit. INTERVENTIONS: The Abbott i-STATTM (Hb, clinical chemistry, INR) and the AfinionTM Analyser (CRP) and corresponding laboratory analyses. OUTCOMES: Agreement (Bland-Altman) and bias (Passing-Bablok regression). RESULTS: Among 462 adults we found an absolute mean difference between point-of-care and central laboratory analyses of 6.4g/L (95%LOA -7.9 to +20.6) for haemoglobin, -0.5mmol/L (95%LOA -4.5 to +3.5) for sodium, 0.2mmol/L (95%LOA -0.6 to +0.9) for potassium, 0.0mmol/L (95%LOA -0.3 to +0.3) for calcium, 9.0 µmol/L (95%LOA -18.5 to +36.4) for creatinine, 0.0mmol/L (95%LOA -2.7 to +2.6) for urea, -0.2 (95%LOA -2.4 to +2.0) for INR, -5.0 mg/L (95%LOA -24.4 to +14.4) for CRP. CONCLUSIONS: There was acceptable agreement and bias for these analytes, except for haemoglobin and creatinine.

Secondary findings from whole-exome/genome sequencing evaluating stakeholder perspectives. A review of the literature.

With the development of next generation sequencing, beyond identifying the cause of manifestations that justified prescription of the test, other information with potential interest for patients and their families, defined as secondary findings (SF), can be provided once patients have given informed consent, in particular when therapeutic and preventive options are available. The disclosure of such findings has caused much debate. The aim of this work was to summarize all opinion-based studies focusing on SF, so as to shed light on the concerns that this question generate. A review of the literature was performed, focusing on all PubMed articles reporting qualitative, quantitative or mixed studies that interviewed healthcare providers, participants, or society regarding this subject. The methodology was carefully analysed, in particular whether or not studies made the distinction between actionable and non-actionable SF, in a clinical or research context. From 2010 to 2016, 39 articles were compiled. A total of 14,868 people were interviewed (1259 participants, 6104 healthcare providers, 7505 representatives of society). When actionable and non-actionable SF were distinguished (20 articles), 92% of respondents were keen to have results regarding actionable SF (participants: 88%, healthcare providers: 86%, society: 97%), against 70% (participants: 83%, healthcare providers: 62%, society: 73%) for non-actionable SF. These percentages were slightly lower in the specific situation of children probands. For respondents, the notion of the «patient's choice¼ is crucial. For healthcare providers, the importance of defining policies for SF among diagnostic lab, learning societies and/or countries is outlined, in particular regarding the content and extension of the list of actionable genes to propose, the modalities of information, and the access to information about adult-onset diseases in minors. However, the existing literature should be taken with caution, since most articles lack a clear definition of SF and actionability, and referred to hypothetical scenarios with limited information to respondents. Studies conducted by multidisciplinary teams involving patients with access to results are sadly lacking, in particular in the medium term after the results have been given. Such studies would feed the debate and make it possible to measure the impact of such findings and their benefit-risk ratio.

TBL1XR1 mutations in Pierpont syndrome are not restricted to the recurrent p.Tyr446Cys mutation.

Pierpont syndrome is a rare and sporadic syndrome, including developmental delay, facial characteristics, and abnormal extremities. Recently, a recurrent de novo TBL1XR1 variant (c.1337A > G; p.Tyr446Cys) has been identified in eight patients by whole-exome sequencing. A dominant-negative effect of this mutation is strongly suspected, since patients with TBL1XR1 deletion and other variants predicting loss of function do not share the same phenotype. We report two patients with typical Pierpont-like syndrome features. Exome sequencing allowed identifying a de novo heterozygous missense TBL1XR1 variant in both patients, different from those already reported: p.Cys325Tyr and p.Tyr446His. The localization of these mutations and clinical features of Pierpont-like syndrome suggest that their functional consequences are comparable with the recurrent mutation previously described, and provided additional data to understand molecular mechanisms of TBL1XR1 anomalies.

INTU-related oral-facial-digital syndrome type VI: A confirmatory report.

Oral-facial-digital (OFD) syndromes are a subgroup of ciliopathies distinguished by the co-occurrence of hamartomas and/or multiple frenula of the oral region and digital anomalies. Several clinical forms of OFD syndromes are distinguished by their associated anomalies and/or inheritance patterns, and at least 20 genetic types of OFD syndromes have been delineated. We describe here a child with preaxial and postaxial polydactyly, lingual hamartoma, a congenital heart defect, delayed development and cerebellar peduncles displaying the molar tooth sign. Whole-exome sequencing and SNP array identified compound heterozygous variants in the INTU gene, which encodes a protein involved in the positioning of the ciliary basal body. INTU is a subunit of the CPLANE multiprotein complex essential for the assembly of IFT-A particles and intraflagellar transport. This report of a second patient with INTU-related OFD syndrome and the further delineation of its neuroimaging and skeletal phenotype now allow INTU-related OFD syndromes to be classified within the OFD syndrome type VI group. Patients display a phenotype similar to that of mice with a hypomorphic mutation of Intu, but with the addition of a heart defect.

Truncating variants of the DLG4 gene are responsible for intellectual disability with marfanoid features.

Marfanoid habitus (MH) combined with intellectual disability (ID) is a genetically and clinically heterogeneous group of overlapping disorders. We performed exome sequencing in 33 trios and 31 single probands to identify novel genes specific to MH-ID. After the search for variants in known disease-causing genes and non-disease-causing genes with classical approaches, we searched for variants in non-disease-causing genes whose pLI was above 0.9 (ExAC Consortium data), in which truncating variants were found in at least 3 unrelated patients. Only DLG4 gene met these criteria. Data from the literature and various databases also indicated its implication in ID. DLG4 encodes post-synaptic density protein 95 (PSD-95), a protein expressed in various tissues, including the brain. In neurons, PSD-95 is located at the post-synaptic density, and is associated with glutamatergic receptor signaling (NMDA and AMPA). PSD-95 probably participates in dendritogenesis. Two patients were heterozygous for de novo frameshift variants and one patient carried a a consensus splice site variant. Gene expression studies supported their pathogenicity through haploinsufficiency and loss-of-function. Patients exhibited mild-to-moderate ID, similar marfanoid features, including a long face, high-arched palate, long and thin fingers, pectus excavatum, scoliosis and ophthalmological manifestations (nystagmus or strabismus). Our study emphasizes the role of DLG4 as a novel post-synaptic-associated gene involved in syndromic ID associated with MH.

Okur-Chung neurodevelopmental syndrome: Eight additional cases with implications on phenotype and genotype expansion.

Okur-Chung syndrome is a neurodevelopmental condition attributed to germline CSNK2A1 pathogenic missense variants. We present 8 unreported subjects with the above syndrome, who have recognizable dysmorphism, varying degrees of developmental delay and multisystem involvement. Together with 6 previously reported cases, we present a case series of 7 female and 7 male subjects, highlighting the recognizable facial features of the syndrome (microcephaly, hypertelorism, epicanthic fold, ptosis, arched eyebrows, low set ears, ear fold abnormality, broad nasal bridge and round face) as well as frequently occurring clinical features including neurodevelopmental delay (93%), gastrointestinal (57%), musculoskeletal (57%) and immunological (43%) abnormalities. The variants reported in this study are evolutionary conserved and absent in the normal population. We observed that the CSNK2A1 gene is relatively intolerant to missense genetic changes, and most variants are within the protein kinase domain. All except 1 variant reported in this cohort are spatially located on the binding pocket of the holoenzyme. We further provide key recommendations on the management of Okur-Chung syndrome. To conclude, this is the second case series on Okur-Chung syndrome, and an in-depth review of the phenotypic features and genomic findings of the condition with suggestions on clinical management.

Pantoprazole, a proton pump inhibitor, does not prevent botulinum toxin induced disuse osteopenia in mice.

OBJECTIVES: Pantoprazole is a proton pump inhibitor that has been shown to inhibit bone resorption. The aim of the study was to investigate whether pantoprazole can prevent development of botulinum toxin (BTX)-induced disuse osteopenia in mice. METHODS: Forty-eight 16-week-old female C57BL/6J mice were randomized into 4 groups (n=12): Base, Ctrl, BTX, and BTX+Pan. The Base group was euthanized at study start. The BTX and BTX+Pan groups were immobilized by injections with BTX in one hind limb. The BTX+Pan group was injected i.p. daily with 100 mg pantoprazole per kg bodyweight. The mice were euthanized after 3 weeks of treatment. The skeletal status was investigated by DEXA, µCT, mechanical testing, dynamic bone histomorphometry, and RT-qPCR. The bone sites investigated were tibia, femur, L5 vertebra, and humerus. RESULTS: Injections of BTX induced a pronounced and significant loss of bone density, microstructure, and strength in the immobilized hind limb. Furthermore, the localized intramuscular injections of BTX lead to a slight loss of bone and bone strength at the L5 vertebra and humerus. Treatment with pantoprazole did not have any bone protective or deleterious effects. CONCLUSION: Pantoprazole was unable to prevent the development of BTX induced disuse osteopenia in skeletally mature female C57BL/6J mice.

Further delineation of a rare recessive encephalomyopathy linked to mutations in GFER thanks to data sharing of whole exome sequencing data.

BACKGROUND: Alterations in GFER gene have been associated with progressive mitochondrial myopathy, congenital cataracts, hearing loss, developmental delay, lactic acidosis and respiratory chain deficiency in 3 siblings born to consanguineous Moroccan parents by homozygosity mapping and candidate gene approach (OMIM#613076). Next generation sequencing recently confirmed this association by the finding of compound heterozygous variants in 19-year-old girl with a strikingly similar phenotype, but this ultra-rare entity remains however unknown from most of the scientific community. MATERIALS AND METHODS: Whole exome sequencing was performed as part of a "diagnostic odyssey" for suspected mitochondrial condition in 2 patients, presenting congenital cataracts, progressive encephalomyopathy and hypotrophy and detected unreported compound heterozygous variants in GFER. RESULTS: Thanks to an international data sharing, we found 2 additional patients carrying compound heterozygous variants in GFER. Reverse phenotyping confirmed the phenotypical similarities between the 4 patients. Together with the first literature reports, the review of these 8 cases from 4 unrelated families enables us to better describe this apparently homogeneous disorder, with the clinical and biological stigmata of mitochondrial disease. CONCLUSION: This report highlights the clinical utility of whole exome sequencing and reverse phenotyping for the diagnosis of ultra-rare diseases and underlines the importance of a broad data sharing for accurate clinical delineation of previously unrecognized entities.

Autosomal recessive truncating MAB21L1 mutation associated with a syndromic scrotal agenesis.

We report on a boy with a rare malformative association of scrotum agenesis, ophthalmological anomalies, cerebellar malformation, facial dysmorphism and global development delay. The reported patient was carrying a homozygous frameshift in MAB21L1 detected by whole-exome sequencing, considered as the most likely disease-causing variant. Mab21l1 knockout mice present a strikingly similar malformative association of ophthalmological malformations of the anterior chamber and preputial glands hypoplasia. We hypothesize that MAB21L1 haploinsufficiency cause a previously undescribed syndrome with scrotal agenesis, ophthalmological anomalies, facial dysmorphism and gross psychomotor delay as remarkable hallmarks. Four cases from the literature were reported with features suggestive of a similar and recognizable clinical entity. We hypothesize that MAB21L1 should be the culprit gene in these patients.

Alterations in gene expression precede sarcopenia and osteopenia in botulinum toxin immobilized mice.

OBJECTIVES: To investigate alteration of bone and muscle gene expression at different time points during 3 weeks of botulinum toxin (BTX) induced immobilization and how this correlate with conventional analysis of bone and muscle. METHODS: Thirty-five 16-week-old female C57BL/6-mice were investigated; 15 were injected with BTX, 15 served as age-matched controls, and 5 as baseline. 5 BTX-injected and 5 control mice were euthanized after 1, 2, and 3 weeks. Analysis included RT-qPCR, dynamic bone histomorphometry, DEXA, µCT, mechanical testing, and muscle cell cross-sectional-area (CSA). RESULTS: Genes related to osteoblasts were expressed at a lower level after 1 week, but not after 2 and 3 weeks of disuse. Moreover, genes related to osteoclasts were expressed at a higher level after 1 and 2 weeks of disuse, whereafter they approached the level of the controls. Genes related to muscle atrophy were upregulated 1 and 2 weeks after the BTX-injection, but not after 3 weeks. In contrast, deterioration of bone microstructure and strength, and reduction in muscle cell CSA were most evident after 3 weeks of disuse. CONCLUSIONS: Gene expression should be investigated during the first two weeks of immobilization, whereas changes in bone microstructure and muscle cell CSA are most prominent after 3 weeks of immobilization.

[Gordon syndrome: The importance of measuring blood pressure in children]. / Syndrome de Gordon : de l'importance de mesurer la pression artérielle chez l'enfant.

Gordon's syndrome, or type II pseudo-hypoaldosteronism, is a rare cause of arterial hypertension in children. However, it is important to diagnose this syndrome because of the spectacular efficacy of thiazide diuretics. The typical clinical picture of Gordon syndrome includes, apart from arterial hypertension and dyskaliemia, hyperchloremia metabolic acidosis, hypercalciuria, a low rate of renin, and most frequently, a normal or high rate of aldosterone. Dental abnormalities and growth retardation can also be associated. In most cases, it is inherited in an autosomal dominant pattern. We report on a 7-year-old girl who was discovered with arterial hypertension during a consultation for chronic diarrhea. The association of growth retardation, hyperkaliemia, and metabolic acidosis oriented the diagnosis. Starting a thiazide diuretic helped control the arterial hypertension and the kaliemia in a spectacular manner. The genetic analysis proved the existence of a splice mutation on exon 9 of the CUL3 gene coding for cullin 3. This mutation is de novo.

Autosomal recessive IFT57 hypomorphic mutation cause ciliary transport defect in unclassified oral-facial-digital syndrome with short stature and brachymesophalangia.

The 13 subtypes of oral-facial-digital syndrome (OFDS) belong to the heterogeneous group of ciliopathies. Disease-causing genes encode for centrosomal proteins, components of the transition zone or proteins implicated in ciliary signaling. A unique consanguineous family presenting with an unclassified OFDS with skeletal dysplasia and brachymesophalangia was explored. Homozygosity mapping and exome sequencing led to the identification of a homozygous mutation in IFT57, which encodes a protein implicated in ciliary transport. The mutation caused splicing anomalies with reduced expression of the wild-type transcript and protein. Both anterograde ciliary transport and sonic hedgehog signaling were significantly decreased in subjects' fibroblasts compared with controls. Sanger sequencing of IFT57 in 13 OFDS subjects and 12 subjects with Ellis-Van Creveld syndrome was negative. This report identifies the implication of IFT57 in human pathology and highlights the first description of a ciliary transport defect in OFDS, extending the genetic heterogeneity of this subgroup of ciliopathies.

Transaxillary robotic thyroidectomy: Belgian team learning from the first 50 cases.

BACKGROUND: In search for less invasive operative techniques, the da Vinci Robot System was introduced in thyroid surgery. Previous studies have reported on safety, effectiveness and improved cosmetics of transaxillary endoscopic thyroidectomy procedures in selected cases. METHODS: We report on the first 50 patients that have been treated with a gasless transaxillary robot-assisted thyroidectomy in a Belgian institution. We describe the implementation, the operative technique and results of robotic thyroid surgery. RESULTS: 48 hemithyroidectomy and 2 total thyroidectomy procedures were performed. The mean ultrasound dimensions of the nodules were 3.4 ± 1.0 cm (range 1.0-8.0 cm). The mean operative time was significantly longer than with a conventional open approach: 215 min ± 55 min (range 133 min-347 min). No major complications were observed. All patients were "satisfied" about the cosmetic outcome. CONCLUSION: Transaxillary robotic thyroid surgery is demanding, but feasible. Selected patients can benefit from this technique with an optimal cosmetic outcome. Ideal indication in the hand of our team is a hemithyroidectomy for benign nodules ranging up to 5 cm.

Age-related changes in vertebral and iliac crest 3D bone microstructure--differences and similarities.

UNLABELLED: Age-related changes of vertebra and iliac crest 3D microstructure were investigated, and we showed that they were in general similar. The 95th percentile of vertebral trabecular thickness distribution increased with age for women. Surprisingly, vertebral and iliac crest bone microstructure was only weakly correlated (r = 0.38 to 0.75), despite the overall similar age-related changes. INTRODUCTION: The purposes of the study were to determine the age-related changes in iliac and vertebral bone microstructure for women and men over a large age range and to investigate the relationship between the bone microstructure at these skeletal sites. METHODS: Matched sets of transiliac crest bone biopsies and lumbar vertebral body (L2) specimens from 41 women (19-96 years) and 39 men (23-95 years) were micro-computed tomography (µCT) scanned, and the 3D microstructure was quantified. RESULTS: For both women and men, bone volume per total volume (BV/TV), connectivity density (CD), and trabecular number (Tb.N) decreased significantly, while structure model index (SMI) and trabecular separation (Tb.Sp) increased significantly with age at either skeletal site. Vertebral trabecular thickness (Tb.Th) was independent of age for both women and men, while iliac Tb.Th decreased significantly with age for men, but not for women. In general, the vertebral and iliac age-related changes were similar. The 95th percentile of the Tb.Th distribution increased significantly with age for women but was independent of age for men at the vertebral body, while it was independent of age for either sex at the iliac crest. The Tb.Th probability density functions at the two skeletal sites became significantly more similar with age for women, but not for men. The microstructural parameters at the iliac crest and the vertebral bodies were only moderately correlated from r = 0.38 for SMI in women to r = 0.75 for Tb.Sp in men. CONCLUSION: Age-related changes in vertebral and iliac bone microstructure were in general similar. The iliac and vertebral Tb.Th distributions became more similar with age for women. Despite the overall similar age-related changes in trabecular bone microstructure, the vertebral and iliac bone microstructural measures were only weakly correlated (r = 0.38 to 0.75).

Diagnostic and medical strategy for renovascular hypertension: report from a monocentric pediatric cohort.

UNLABELLED: Renovascular hypertension accounts for 5-10 % of hypertension cases in children; there is currently no consensus on treatment. Here, we report on our clinical experience with this disease and outline the different pathways in which to investigate it. We report retrospectively on ten children diagnosed with renovascular hypertension at the University Hospital of Nantes from 2001 to 2012. The main findings were obtained by fortuitous screening of children aged 2 months to 14 years old with neurofibromatosis (n = 2) and fibromuscular dysplasia (n = 8). The hypertension was always severe yet asymptomatic. Lesions were complicated in nine out of ten cases and included bilateral, multiple, mid-aortic syndrome and aneurysm. Doppler ultrasound associated with computed tomography allowed for a precise diagnosis in seven out of ten cases. Where ambiguities persisted, they were highlighted by arteriography, the gold standard investigation. Medical treatment was insufficient, leading to invasive procedures in nine out of ten children: 2 nephrectomies, 2 autotransplantations, and 21 repetitive percutaneous transluminal angioplasties. After invasive procedures, blood pressure control improved in four cases and was resolved in three. CONCLUSION: Arteriography remains to be the gold standard technique for renovascular hypertension in children and can be combined with angioplasty when medical treatment is rendered obsolete. The role of computed tomography is controversial. Despite the heterogeneity of the children studied, we present a general medical and therapeutic management pathway for the treatment of this disease.

Growth hormone mitigates loss of periosteal bone formation and muscle mass in disuse osteopenic rats.

Growth hormone (GH) is a potent anabolic agent capable of increasing both bone and muscle mass. The aim was to investigate whether GH could counteract disuse-induced loss of bone and muscle mass in a rat model. Paralysis was induced by injecting 4 IU Botox (BTX) into the muscles of the right hind limb. Sixty female Wistar rats, 14 weeks old, were divided into the following groups: baseline, controls, BTX, BTX+GH, and GH. GH was given at a dosage of 5 mg/kg/d for 4 weeks. Compared with controls, BTX resulted in lower periosteal bone formation rate (BFR/BS,-79%, P<0.001), bone mineral density (aBMD, -13%, P<0.001), trabecular bone volume (BV/TV, -26%, P<0.05), and mid-femoral bone strength (-12%, P<0.05). In addition, BTX reduced rectus femoris muscle mass (-69%, P<0.001) and muscle cell cross sectional area (CSA) (-73%, P<0.001) compared with controls. GH counteracted disuse-induced losses of periosteal BFR/BS (2-fold increase vs. BTX, P<0.001), whereas no effect on aBMD, trabecular BV/TV, or bone strength was found. In addition, GH partly prevented loss of muscle mass (+29% vs. BTX, P<0.001), and tended to prevent loss of muscle CSA (+11%, P=0.064). In conclusion, GH mitigates disuse-induced loss of periosteal BFR/BS at the mid-femur and rectus femoris muscle mass.

No effect of risedronate on articular cartilage damage in the Dunkin Hartley guinea pig model of osteoarthritis.

OBJECTIVES: To investigate whether treatment with a bisphosphonate would influence the subchondral bone plate stiffness and the development of cartilage damage in Dunkin Hartley guinea pigs, which develop osteoarthritis (OA) spontaneously. METHOD: Fifty-six 3-month-old male Dunkin Hartley guinea pigs were randomized into a baseline group and six groups receiving either the bisphosphonate risedronate (30 µg/kg) or vehicle five times a week for 6, 12, or 24 weeks. The medial condyle of the right stifle joint was investigated by histology, using the Osteoarthritis Research Society International (OARSI) score, along with static and dynamic histomorphometry. The subchondral bone plate of the left tibia was tested mechanically with indentation testing. Degradation products of C-terminal telopeptides of type II collagen (CTX-II) were measured in serum. RESULTS: The OARSI score did not differ between risedronate-treated and control animals at any time point. The fraction of bone surfaces covered with osteoclasts (Oc.S/BS) was significantly suppressed in risedronate-treated animals at all time points, as were the fractions of mineralizing surfaces (MS/BS) and osteoid-covered surfaces (OS/BS), and also serum CTX-II. This was accompanied by a significant increase in the epiphyseal content of calcified tissue and in the thickness of the subchondral bone plate. However, this did not result in a stiffer subchondral bone at any time point. DISCUSSION: The risedronate treatment inhibited osteoclastic resorption of calcified cartilage in the primary spongiosa under the epiphyseal growth plate, explaining the risedronate-mediated decrease in CTX-II. Moreover, the serum CTX-II level was not related to the OA-induced articular cartilage degradation seen in this model. CONCLUSIONS: Risedronate did not influence the OARSI score and subchondral plate stiffness, but decreased serum CTX-II in Dunkin Hartley guinea pigs.