Pathologic gene expression in Gaucher disease: up-regulation of cysteine proteinases including osteoclastic cathepsin K

Regional Differences in the Small Intestinal Proteome of Control Mice and of Mice Lacking Lysosomal Acid Lipase

The metabolic contribution of the small intestine (SI) is still unclear despite recent studies investigating the involvement of single cells in regional differences. Using untargeted proteomics, we identified regional characteristics of the three intestinal tracts of C57BL/6J mice and found that proteins abundant in the mouse ileum correlated with the high ileal expression of the corresponding genes in humans. In the SI of C57BL/6J mice, we also detected an increasing abundance of lysosomal acid lipase (LAL), which is responsible for degrading triacylglycerols and cholesteryl esters within the lysosome. LAL deficiency in patients and mice leads to lipid accumulation, gastrointestinal disturbances, and malabsorption. We previously demonstrated that macrophages massively infiltrated the SI of Lal-deficient (KO) mice, especially in the duodenum. Using untargeted proteomics (ProteomeXchange repository, data identifier PXD048378), we revealed a general inflammatory response and a common lipid-associated macrophage phenotype in all three intestinal segments of Lal KO mice, accompanied by a higher expression of GPNMB and concentrations of circulating sTREM2. However, only duodenal macrophages activated a metabolic switch from lipids to other pathways, which were downregulated in the jejunum and ileum of Lal KO mice. Our results provide new insights into the process of absorption in control mice and possible novel markers of LAL-D and/or systemic inflammation in LAL-D.

Noninvasive DBS-Based Approaches to Assist Clinical Diagnosis and Treatment Monitoring of Gaucher Disease

Gaucher disease (GD) is an autosomal recessive inborn error of metabolism, belonging to the group of lysosomal storage diseases (LSDs). GD is caused by a defect in lysosomal glucocerebrosidase, responsible for glucosylceramide breakdown into glucose and ceramide. Because of this dysfunction, glucosylceramide progressively accumulates in the liver, spleen, bone marrow, bones, and in other tissues and organs, also causing anemia, hepatosplenomegaly, thrombocytopenia, and bone symptoms. Depending on neurological symptoms, GD is classified into three main types. Treatment options for LSDs, including enzyme replacement therapy, hematopoietic stem cell transplantation, small molecular weight pharmacologic chaperones, and, for some LSDs, gene therapy, are increasingly available. For this reason, many efforts are aimed at implementing newborn screening for LSDs since early detection accompanied by a prompt intervention has been demonstrated to be essential for reducing morbidity and mortality and for improved clinical outcomes. Herein, we report two siblings of preschool age, presenting with hepatosplenomegaly and thrombocytopenia. The initial suspicion of GD based on the clinical picture was further supported by biochemical confirmation, through newborn screening workflow, including first- and second-level testing on the same dried blood spot samples, and finally by molecular testing.

Glycoprotein non-metastatic protein B (GPNMB) plasma values in patients with chronic visceral acid sphingomyelinase deficiency

Acid sphingomyelinase deficiency (ASMD) is a rare LSD characterized by lysosomal accumulation of sphingomyelin, primarily in macrophages. With the recent availability of enzyme replacement therapy, the need for biomarkers to assess severity of disease has increased. Glycoprotein non-metastatic protein B (GPNMB) plasma levels were demonstrated to be elevated in Gaucher disease. Given the similarities between Gaucher disease and ASMD, the hypothesis was that GPNMB might be a potential biochemical marker for ASMD as well. Plasma samples of ASMD patients were analyzed and GPNMB plasma levels were compared to those of healthy volunteers. Visceral disease severity was classified as severe when splenic, hepatic and pulmonary manifestations were all present and as mild to moderate if this was not the case. Median GPNMB levels in 67 samples of 19 ASMD patients were 185 ng/ml (range 70-811 ng/ml) and were increased compared to 10 healthy controls (median 36 ng/ml, range 9-175 ng/ml, p < 0.001). Median plasma GPNMB levels of ASMD patients with mild to moderate visceral disease compared to patients with severe visceral disease differed significantly and did not overlap (respectively 109 ng/ml, range 70-304 ng/ml and 325 ng/ml, range 165-811 ng/ml, p < 0.001). Correlations with other biochemical markers of ASMD (i.e. chitotriosidase activity, CCL18 and lysosphingomyelin, respectively R = 0.28, p = 0.270; R = 0.34, p = 0.180; R = 0.39, p = 0.100) and clinical parameters (i.e. spleen volume, liver volume, diffusion capacity and forced vital capacity, respectively R = 0.59, p = 0.061, R = 0.5, p = 0.100, R = 0.065, p = 0.810, R = -0.38, p = 0.160) could not be established within this study. The results of this study suggest that GPNMB might be suitable as a biomarker of visceral disease severity in ASMD. Correlations between GPNMB and biochemical or clinical markers of ASMD and response to therapy have to be studied in a larger cohort.

Patient centered guidelines for the laboratory diagnosis of Gaucher disease type 1

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder due to the deficient activity of the acid beta-glucosidase (GCase) enzyme, resulting in the progressive lysosomal accumulation of glucosylceramide (GlcCer) and its deacylated derivate, glucosylsphingosine (GlcSph). GCase is encoded by the GBA1 gene, located on chromosome 1q21 16 kb upstream from a highly homologous pseudogene. To date, more than 400 GBA1 pathogenic variants have been reported, many of them derived from recombination events between the gene and the pseudogene. In the last years, the increased access to new technologies has led to an exponential growth in the number of diagnostic laboratories offering GD testing. However, both biochemical and genetic diagnosis of GD are challenging and to date no specific evidence-based guidelines for the laboratory diagnosis of GD have been published. The objective of the guidelines presented here is to provide evidence-based recommendations for the technical implementation and interpretation of biochemical and genetic testing for the diagnosis of GD to ensure a timely and accurate diagnosis for patients with GD worldwide. The guidelines have been developed by members of the Diagnostic Working group of the International Working Group of Gaucher Disease (IWGGD), a non-profit network established to promote clinical and basic research into GD for the ultimate purpose of improving the lives of patients with this disease. One of the goals of the IWGGD is to support equitable access to diagnosis of GD and to standardize procedures to ensure an accurate diagnosis. Therefore, a guideline development group consisting of biochemists and geneticists working in the field of GD diagnosis was established and a list of topics to be discussed was selected. In these guidelines, twenty recommendations are provided based on information gathered through a systematic review of the literature and two different diagnostic algorithms are presented, considering the geographical differences in the access to diagnostic services. Besides, several gaps in the current diagnostic workflow were identified and actions to fulfill them were taken within the IWGGD. We believe that the implementation of recommendations provided in these guidelines will promote an equitable, timely and accurate diagnosis for patients with GD worldwide.

Cysteine cathepsins: A long and winding road towards clinics

Biomedical research often focuses on properties that differentiate between diseased and healthy tissue; one of the current focuses is elevated expression and altered localisation of proteases. Among these proteases, dysregulation of cysteine cathepsins can frequently be observed in inflammation-associated diseases, which tips the functional balance from normal physiological to pathological manifestations. Their overexpression and secretion regularly exhibit a strong correlation with the development and progression of such diseases, making them attractive pharmacological targets. But beyond their mostly detrimental role in inflammation-associated diseases, cysteine cathepsins are physiologically highly important enzymes involved in various biological processes crucial for maintaining homeostasis and responding to different stimuli. Consequently, several challenges have emerged during the efforts made to translate basic research data into clinical applications. In this review, we present both physiological and pathological roles of cysteine cathepsins and discuss the clinical potential of cysteine cathepsin-targeting strategies for disease management and diagnosis.

TRAP5b and RANKL/OPG Predict Bone Pathology in Patients with Gaucher Disease

Background and objective: Bone involvement occurs in 75% of patients with Gaucher disease (GD), and comprises structural changes, debilitating pain, and bone density abnormalities. Osteoporosis is a silent manifestation of GD until a pathologic fracture occurs. Thus, early diagnosis is crucial for identifying high-risk patients in order to prevent irreversible complications. Methods: Thirty-three patients with GD were assessed prospectively to identify predictive markers associated with bone density abnormalities, osteopenia (OSN), and osteoporosis (OSR). Subjects were categorized into three cohorts based on T- or Z-scores of bone mineral density (BMD). The first GD cohort consisted of those with no bone complications (Z-score ≥ −0.9; T-scores ≥ −1), the second was the OSN group (−1.8 ≥ Z-score ≥ −1; −2.5 ≥ T-score ≥ −1), and the third was the OSR group (Z-score ≤ −1.9; T-scores ≤ −2.5). Serum levels of TRAP5b, RANKL, OPG, and RANK were quantified by enzyme-linked immunosorbent assays. Results: TRAP5b levels were increased in GD patients, and showed a positive correlation with GD biomarkers, including plasma glucosylsphingosine (lyso-Gb1) and macrophage activation markers CCL18 and chitotriosidase. The highest level of TRAP5b was measured in patients with osteoporosis. The elevation of RANKL and RANKL/OPG ratio correlated with osteopenia in GD. Conclusion: TRAP5b, RANKL, and RANKL/OPG elevation indicate osteoclast activation in GD. TRAP5b is a potential bone biomarker for GD with the ability to predict the progression of bone density abnormalities.

Semaphorin 7A: A novel marker of disease activity in Gaucher disease

Gaucher disease (GD) is a recessively inherited lysosomal storage disorder in which sphingolipids accumulates in the macrophages that transform into Gaucher cells. A growing body of evidence indicates that red blood cells (RBCs) represent important actors in GD pathophysiology. We previously demonstrated that altered RBC properties including increased Lyso-GL1 levels, dyserythropoiesis, and iron metabolism defect in GD patients contribute to anemia and hyperferritinemia. Since RBC defects also correlated well with markers of GD severity and were normalized under enzyme replacement therapy (ERT), the identification of molecules that are deregulated in GD RBCs represents an important issue in the search of pertinent markers of the disease. Here, we found a decreased expression of the GPI-anchored cell surface protein Semaphorin 7A (Sema7A) in RBCs from untreated GD (GD UT) patients, in parallel with increased levels of the soluble form in the plasma. Sema7A plays a role in neural guidance, atherosclerosis, and inflammatory diseases and represents a promigratory cue in physiological and pathological conditions. We showed that the decreased expression of Sema7A in RBCs correlated with their abnormal properties and with markers of GD activity. Interestingly, ERT restored the level of Sema7A to normal values both in RBCs and in plasma from GD patients. We then proposed that SemaA7A represents a simple and pertinent marker of inflammation in GD. Finally, because Sema7A is known to regulate the activity of immune cells, the increased level of soluble Sema7A in GD patients could propagate inflammation in several tissues.

Aberrant progranulin, YKL-40, cathepsin D and cathepsin S in Gaucher disease

In Gaucher disease, several macrophage-specific biomarkers have been validated for use in the clinic. However, Gaucher disease is more complex involving system-wide pathophysiology beyond the macrophage, and based on gene array analysis in our Gaucher disease mouse model and other emerging pathophysiologic insights, we evaluated serum levels of cathepsins D and S, YKL-40 and progranulin in Gaucher disease patients. We assessed their biomarker potential in Gaucher disease and compared them to established Gaucher disease biomarkers, chitotriosidase, chemokine ligand 18 (CCL18), and other indicators of disease severity and response to therapy. Mean YKL-40 and cathepsin D and S levels were significantly higher in Gaucher disease patients compared to healthy controls; in contrast, mean progranulin levels were lower in Gaucher disease patients compared to healthy controls. Enzyme replacement therapy resulted in a significant reversal of elevated cathepsin D and S but there was no change in progranulin and YKL-40 levels. Patients with persistent splenomegaly after long-term enzyme replacement therapy had significantly higher serum YKL-40 than patients with smaller spleens (63.0 ± 6.4 ng/ml vs. 46.4 ± 4.3 ng/ml, p = .03). Serum YKL-40 levels were higher in subjects with severe bone involvement (Hermann Score 3 to 5) compared to those with milder bone involvement (Hermann Score 1 to 2) (70.1 ± 4.3 ng/ml vs. 48.1 ± 3.7 ng/ml, p = .0002). YKL-40 was only weakly associated with chitotriosidase (r = 0.2, p = .008) and CCL18 (r = 0.3, p = .0004), and cathepsin S was moderately associated with chitotriosidase (r = 0.4, p = .01) and CCL18 (r = 0.6, p < .0001). Receiver operating curves for progranulin and YKL-40 demonstrated areas under the curves of 0.80 and 0.70, respectively. In conclusion, while these biomarkers do not meet robust properties of established macrophage-specific biomarkers, they may inform severity of skeletal disease, contribution of fibrosis to residual splenomegaly, and other disease manifestations. These findings, including markedly low progranulin levels that do not change upon enzyme replacement therapy, are intriguing to prompt further investigations to decipher their role in pathophysiology and relevance to diverse phenotypes of Gaucher disease.

A Human Stem Cell Model of Fabry Disease Implicates LIMP-2 Accumulation in Cardiomyocyte Pathology

Here, we have used patient-derived induced pluripotent stem cell (iPSC) and gene-editing technology to study the cardiac-related molecular and functional consequences of mutations in GLA causing the lysosomal storage disorder Fabry disease (FD), for which heart dysfunction is a major cause of mortality. Our in vitro model recapitulated clinical data with FD cardiomyocytes accumulating GL-3 and displaying an increased excitability, with altered electrophysiology and calcium handling. Quantitative proteomics enabled the identification of >5,500 proteins in the cardiomyocyte proteome and secretome, and revealed accumulation of the lysosomal protein LIMP-2 and secretion of cathepsin F and HSPA2/HSP70-2 in FD. Genetic correction reversed these changes. Overexpression of LIMP-2 directly induced the secretion of cathepsin F and HSPA2/HSP70-2, implying causative relationship, and led to massive vacuole accumulation. In summary, our study has revealed potential new cardiac biomarkers for FD, and provides valuable mechanistic insight into the earliest pathological events in FD cardiomyocytes.

Gaucher Disease in Bone: From Pathophysiology to Practice

Gaucher disease (GD) is a rare, genetic lysosomal disorder leading to lipid accumulation and dysfunction in multiple organs. Involvement of the skeleton is one of the most prevalent aspects of GD and a major cause of pain, disability, and reduced quality of life. Uniform recommendations for contemporary evaluation and management are needed. To develop practical clinical recommendations, an international group of experienced physicians conducted a comprehensive review of 20 years' of the literature, defining terms according to pathophysiological understanding and pointing out best practice and unmet needs related to the skeletal features of this disorder. Abnormalities of bone modeling, reduced bone density, bone infarction, and plasma cell dyscrasias accompany the displacement of healthy adipocytes in adult marrow. Exposure to excess bioactive glycosphingolipids appears to affect hematopoiesis and the balance of osteoblast and osteoclast numbers and activity. Imbalance between bone formation and breakdown induces disordered trabecular and cortical bone modeling, cortical bone thinning, fragility fractures, and osteolytic lesions. Regular assessment of bone mineral density, marrow infiltration, the axial skeleton and searching for potential malignancy are recommended. MRI is valuable for monitoring skeletal involvement: It provides semiquantitative assessment of marrow infiltration and the degree of bone infarction. When MRI is not available, monitoring of painful acute bone crises and osteonecrosis by plain X-ray has limited value. In adult patients, we recommend DXA of the lumbar spine and left and right hips, with careful protocols designed to exclude focal disease; serial follow-up should be done using the same standardized instrument. Skeletal health may be improved by common measures, including adequate calcium and vitamin D and management of pain and orthopedic complications. Prompt initiation of specific therapy for GD is crucial to optimizing outcomes and preventing irreversible skeletal complications. Investing in safe, clinically useful, and better predictive methods for determining bone integrity and fracture risk remains a need. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Gene expression profile in patients with Gaucher disease indicates activation of inflammatory processes

Gaucher disease (GD) is a rare inherited metabolic disease caused by pathogenic variants in the GBA1 gene. So far, the pathomechanism of GD was investigated mainly in animal models. In order to delineate the molecular changes in GD cells we analysed gene expression profile in cultured skin fibroblasts from GD patients, control individuals and, additionally, patients with Niemann-Pick type C disease (NPC). We used expression microarrays with subsequent validation by qRT-PCR method. In the comparison GD patients vs. controls, the most pronounced relative fold change (rFC) in expression was observed for genes IL13RA2 and IFI6 (up-regulated) and ATOH8 and CRISPLD2 (down-regulated). Products of up-regulated and down-regulated genes were both enriched in genes associated with immune response. In addition, products of down-regulated genes were associated with cell-to-cell and cell-to-matrix interactions, matrix remodelling, PI3K-Akt signalling pathway and a neuronal survival pathway. Up-regulation of PLAU, IFIT1, TMEM158 and down-regulation of ATOH8 and ISLR distinguished GD patients from both NPC patients and healthy controls. Our results emphasize the inflammatory character of changes occurring in human GD cells indicating that further studies on novel therapeutics for GD should consider anti-inflammatory agents.

Gaucher disease iPSC-derived osteoblasts have developmental and lysosomal defects that impair bone matrix deposition

Gaucher disease (GD) is caused by bi-allelic mutations in GBA1, the gene that encodes acid β-glucocerebrosidase (GCase). Individuals affected by GD have hematologic, visceral and bone abnormalities, and in severe cases there is also neurodegeneration. To shed light on the mechanisms by which mutant GBA1 causes bone disease, we examined the ability of human induced pluripotent stem cells (iPSC) derived from patients with Types 1, 2 and 3 GD, to differentiate to osteoblasts and carry out bone deposition. Differentiation of GD iPSC to osteoblasts revealed that these cells had developmental defects and lysosomal abnormalities that interfered with bone matrix deposition. Compared with controls, GD iPSC-derived osteoblasts exhibited reduced expression of osteoblast differentiation markers, and bone matrix protein and mineral deposition were defective. Concomitantly, canonical Wnt/β catenin signaling in the mutant osteoblasts was downregulated, whereas pharmacological Wnt activation with the GSK3β inhibitor CHIR99021 rescued GD osteoblast differentiation and bone matrix deposition. Importantly, incubation with recombinant GCase (rGCase) rescued the differentiation and bone-forming ability of GD osteoblasts, demonstrating that the abnormal GD phenotype was caused by GCase deficiency. GD osteoblasts were also defective in their ability to carry out Ca2+-dependent exocytosis, a lysosomal function that is necessary for bone matrix deposition. We conclude that normal GCase enzymatic activity is required for the differentiation and bone-forming activity of osteoblasts. Furthermore, the rescue of bone matrix deposition by pharmacological activation of Wnt/β catenin in GD osteoblasts uncovers a new therapeutic target for the treatment of bone abnormalities in GD.

Glycoprotein Non-Metastatic Protein B: An Emerging Biomarker for Lysosomal Dysfunction in Macrophages

Several diseases are caused by inherited defects in lysosomes, the so-called lysosomal storage disorders (LSDs). In some of these LSDs, tissue macrophages transform into prominent storage cells, as is the case in Gaucher disease. Here, macrophages become the characteristic Gaucher cells filled with lysosomes laden with glucosylceramide, because of their impaired enzymatic degradation. Biomarkers of Gaucher cells were actively searched, particularly after the development of costly therapies based on enzyme supplementation and substrate reduction. Proteins selectively expressed by storage macrophages and secreted into the circulation were identified, among which glycoprotein non-metastatic protein B (GPNMB). This review focusses on the emerging potential of GPNMB as a biomarker of stressed macrophages in LSDs as well as in acquired pathologies accompanied by an excessive lysosomal substrate load in macrophages.

Validating glycoprotein non-metastatic melanoma B (gpNMB, osteoactivin), a new biomarker of Gaucher disease

In the spleens of Gaucher disease mice and patients, there is a striking elevation of expression of glycoprotein non-Metastatic Melanoma B (gpNMB). We conducted a study in a large cohort of patients with Gaucher disease to assess the utility of serum levels of soluble fragment of gpNMB as a biomarker of disease activity. There was >15-fold elevation of gpNMB in sera of untreated patients with Gaucher disease. gpNMB levels correlated with overall disease severity as well as the severity of individual organ compartments: liver, spleen, bone and hematological disease. Imiglucerase enzyme replacement therapy resulted in significant reduction of gpNMB. Serum levels of gpNMB were highly correlated with accumulation of bioactive lipid substrate of Gaucher disease, glucosylsphingosine as well as established biomarkers, chitotriosidase and chemokine, CCL18. Our results suggest utility of gpNMB as a biomarker of Gaucher disease to monitor individual patients and cohorts of patients for disease progression or response to therapy. Investigation of gpNMB in Gaucher disease pathophysiology is likely to illuminate our understanding disease mechanisms.

Elevation of glycoprotein nonmetastatic melanoma protein B in type 1 Gaucher disease patients and mouse models

Gaucher disease is caused by inherited deficiency of lysosomal glucocerebrosidase. Proteome analysis of laser‐dissected splenic Gaucher cells revealed increased amounts of glycoprotein nonmetastatic melanoma protein B (gpNMB). Plasma gpNMB was also elevated, correlating with chitotriosidase and CCL18, which are established markers for human Gaucher cells. In Gaucher mice, gpNMB is also produced by Gaucher cells. Correction of glucocerebrosidase deficiency in mice by gene transfer or pharmacological substrate reduction reverses gpNMB abnormalities. In conclusion, gpNMB acts as a marker for glucosylceramide‐laden macrophages in man and mouse and gpNMB should be considered as candidate biomarker for Gaucher disease in treatment monitoring.

Standardization of MRI and Scintigraphic Scores for Assessing the Severity of Bone Marrow Involvement in Adult Patients With Type 1 Gaucher Disease

OBJECTIVE

MRI and (99m)Tc-sestamibi scintigraphy are used to estimate bone marrow infiltration in patients with Gaucher disease (GD), but comparison of data obtained at different institutions is difficult because different scores are employed for semiquantitative assessment. We developed normalized scores for comparing data both within a single method (MRI) and between different methods (MRI versus scintigraphy).

MATERIALS AND METHODS

We evaluated 51 patients with type 1 GD (26 women, 25 men; mean age ± SD, 36.3 ± 10.9 years old). T1- and T2-weighted turbo spin-echo sequences at 1.5 T served to derive the bone marrow burden score (0-16), the vertebra-disk ratio (VDR), the Terk score (0-3), and the Spanish-MRI score (S-MRI, 0-24). Scintigraphy was scored between 0 and 8. Each score was normalized into four categories: 0 = normal, 1 = mild, 2 = intermediate, 3 = severe involvement. Interobserver and intraobserver agreements were evaluated by kappa statistics; nonparametric statistics with Bonferroni correction assessed correlations among the various original and normalized scores.

RESULTS

Interobserver agreement was excellent for the original scores (κ = 0.730-0.843) and even more so for the normalized scores (κ = 0.775-0.940). Intraobserver agreement kappa values ranged from 0.753 to 0.937 for the original scores and 0.851 to 1.000 for the normalized scores. Highly significant correlations were found among the various original scores (r = 0.42-0.86, p values between 0.0296 and < 0.0001), except for VDR versus S-MRI and Terk. Normalization generally induced marginal reductions in statistical significance, whereas S-MRI versus VDR reached statistical significance with the normalized scores.

CONCLUSION

Our data indicate no significant loss of statistical information is caused by the normalization we employed. Our approach therefore facilitates comparison of different scores obtained in different institutions with different imaging modalities.

Evaluation of neopterin as a biomarker for the monitoring of Gaucher disease patients

OBJECTIVES

Biomarker research is an important area of investigation in Gaucher disease, caused by an inherited deficiency of a lysosomal enzyme, glucocerebrosidase. We evaluated the usefulness of neopterin, as a novel biomarker reflecting chronic inflammation and immune system activation in Gaucher disease and analysed its evolution in response to enzyme replacement therapy (ERT).

METHODS

Circulating plasma neopterin levels in 31 patients with non-neuronopathic Gaucher disease were measured before and after the onset of ERT and were compared with those of 18 healthy controls. Plasma chitotriosidase activity was also monitored, as a reference biomarker, against which we evaluated the evolution of neopterin.

RESULTS

Neopterin levels were significantly increased in treatment-naïve patients (mean 11.90 ± 5.82 nM) compared with controls (6.63 ± 5.59 nM, Mann-Whitney U test P = 0.001), but returned to normal levels (6.92 ± 4.66 nM) following ERT. Investigating the diagnostic value of neopterin by receiver operating characteristic analysis, we found a cut-off value of 7.613 nM that corresponds to an area under the curve of 0.780 and indicates a good discrimination capacity, with a sensitivity of 0.774 and a specificity of 0.778.

DISCUSSION

Our results suggest that measurement of circulating neopterin may be considered as a novel test for the confirmation of diagnosis and monitoring of the efficacy of therapeutic intervention in Gaucher disease. Plasma neopterin levels reflect the global accumulation and activation of Gaucher cells and the extent of chronic immune activation in this disorder.

CONCLUSION

Neopterin may be an alternative storage cell biomarker in Gaucher disease, especially in chitotriosidase-deficient patients.

Bilateral Femoral Osteolytic Lesions in a Patient with Type 3 Gaucher Disease

Type 3 Gaucher disease (GD) manifests with hematologic, neurological and skeletal involvement including Erlenmeyer flask bone deformities, osteopenia, painful bone crises and fractures. We describe bilateral symmetric osteolytic lesions in a 23 year old with type 3 GD, chronically treated with enzyme replacement therapy. These atypical bone findings, previously reported in two similar patients with type 3 GD, expand our understanding of the evolving natural history of GD in the post-treatment era.

Osteopontin: a potential biomarker of Gaucher disease

Gaucher disease (GD) is one of the most prevalent lysosomal storage disorders and the disorder that has the greatest immune system involvement. Pathologic lipid accumulation in macrophages accounts for a small amount of the additional tissue mass in the liver and spleen. The additional increase may be related to an inflammatory response because Gaucher cells secrete inflammatory mediators. Osteopontin (OPN) is a protein identified in cancer cells and in bone cells that is produced by several types of immune cells including T-cells and macrophages. We report here elevated OPN levels in the plasma of type 1 GD patients and its sensitive response to enzyme replacement therapy. The mean OPN value of GD patients receiving ERT was similar to the values of controls and patients with other lysosomal disorders. When comparing untreated and treated GD patients, the p value was <0.001. In GD, OPN appears to be more sensitive to ERT than chitotriosidase and can be used during the follow-up of patients who are chitotriosidase deficient. Additional extended studies are required to relate variations in the OPN levels to clinical findings and response to therapy in GD patients.

Evaluation of bone involvement in patients with Gaucher disease: a semi-quantitative magnetic resonance imaging method (using ROI estimation of bone lesion) as an alternative method to semi-quantitative methods used so far

OBJECTIVE

The aim of this study was to evaluate bone involvement in patients with Gaucher disease (GD) and to propose a novel semi-quantitative magnetic resonance imaging (MRI) staging.

METHODS

MRI of the lumbar spine, femur, and tibia was performed in 24 patients with GD and 24 healthy controls. We also measured circulating levels of C-C motif ligand-3 (CCL-3) chemokine, C-telopeptide of collagen type-1 (CTX), and tartrate-resistant acid phosphatase isoform type-b (TRACP-5b).

RESULTS

We used the following staging based on MRI data: stage I: region of interest (ROI) 1/2 of normal values and bone infiltration up to 30%; stage II: ROI 1/3 of normal values and bone infiltration from 30 to 60%; stage III: ROI 1/4 of normal values and bone infiltration from 60% to 80%; and stage IV: detection of epiphyseal infiltration, osteonecrosis and deformity regardless of the ROI's values. All but two patients had abnormal MRI findings: 9 (37.5%), 6 (25%), 3 (12.5%), and 4 (16.7%) had stages I-IV, respectively. Patients with GD had elevated chitotriosidase, serum TRACP-5b, and CCL-3 levels (P < 0.001).

CONCLUSIONS

We propose an easily reproducible semi-quantitative scoring system and confirm that patients with GD have abnormal MRI bone findings and enhanced osteoclast activity possibly due to elevated CCL-3.

Identification of a biomarker in cerebrospinal fluid for neuronopathic forms of Gaucher disease

Gaucher disease, a recessive inherited metabolic disorder caused by defects in the gene encoding glucosylceramidase (GlcCerase), can be divided into three subtypes according to the appearance of symptoms associated with central nervous system involvement. We now identify a protein, glycoprotein non-metastatic B (GPNMB), that acts as an authentic marker of brain pathology in neurological forms of Gaucher disease. Using three independent techniques, including quantitative global proteomic analysis of cerebrospinal fluid (CSF) in samples from Gaucher disease patients that display neurological symptoms, we demonstrate a correlation between the severity of symptoms and GPNMB levels. Moreover, GPNMB levels in the CSF correlate with disease severity in a mouse model of Gaucher disease. GPNMB was also elevated in brain samples from patients with type 2 and 3 Gaucher disease. Our data suggest that GPNMB can be used as a marker to quantify neuropathology in Gaucher disease patients and as a marker of treatment efficacy once suitable treatments towards the neurological symptoms of Gaucher disease become available.

Innovative treatments for lysosomal diseases

Striking therapeutic advances for lysosomal diseases have harnessed the biology of this organelle and illustrate its central rôle in the dynamic economy of the cell. Further Innovation will require improved protein-targetting or realization of therapeutic gene- and cell transfer stratagems. Rescuing function before irreversible injury, mandates a deep knowledge of clinical behaviour as well as molecular pathology – and frequently requires an understanding of neuropathology. Whether addressing primary causes, or rebalancing the effects of disordered cell function, true therapeutic innovation depends on continuing scientific exploration of the lysosome. Genuine partnerships between biotech and the patients affected by this extraordinary family of disorders continue to drive productive pharmaceutical discovery.

In vitro and in vivo comparative and competitive activity-based protein profiling of GH29 α-l-fucosidases

GH29 α-l-fucosidases catalyze the hydrolysis of α-l-fucosidic linkages. Deficiency in human lysosomal α-l-fucosidase (FUCA1) leads to the recessively inherited disorder, fucosidosis. Herein we describe the development of fucopyranose-configured cyclophellitol aziridines as activity-based probes (ABPs) for selective in vitro and in vivo labeling of GH29 α-l-fucosidases from bacteria, mice and man. Crystallographic analysis on bacterial α-l-fucosidase confirms that the ABPs act by covalent modification of the active site nucleophile. Competitive activity-based protein profiling identified l-fuconojirimycin as the single GH29 α-l-fucosidase inhibitor from eight configurational isomers.

[Cathepsin K as a biomarker of bone involvement in type 1 Gaucher disease]

BACKGROUND AND OBJECTIVE

Gaucher disease is an inherited disorder caused by deficit of acid β-glucocerebrosidase, responsible for the degradation of glucosylceramide to ceramide and glucose. Although the disorder is primarily hematologic, bone is the second most commonly affected structure. Cathepsin K (CATK) is an enzyme involved in bone remodelling process. It has been proposed that determination of its serum concentrations may provide additional information to other biomarkers.

PATIENTS AND METHODS

The study included 20 control subjects and 20 Gaucher type 1 patients from Andalusia and Extremadura regions. We analyzed the biomarkers of bone remodelling: the bone alkaline phosphatase (B-ALP), the N-terminal propeptide of type 1 procollagen (P1NP), the β carboxyterminal telopeptide of type 1 collagen (CTx) and the CATK through electrochemiluminescence and immunoassay techniques.

RESULTS

There is an increase in levels of CATK, CATK/P1NP and CATK/B-ALP ratios in type 1 Gaucher patients compared to the control group. Considering the existence of skeletal manifestations in the patient group, the CATK and CATK/P1NP ratio showed higher levels in patients with bone damage compared to those without it.

CONCLUSIONS

Although imaging studies are the gold standard for monitoring bone disease in type 1 Gaucher patients, the utility of CATK should be considered as a possible indicator of bone damage in these patients. Furthermore, this parameter can be used in the monitoring of the treatment of bone pathology.

Inhibition of UDP-glucosylceramide synthase in mice prevents Gaucher disease-associated B-cell malignancy

Clonal B-cell proliferation is a frequent manifestation of Gaucher disease - a sphingolipidosis associated with a high risk of multiple myeloma and non-Hodgkin lymphoma. Gaucher disease is caused by genetic deficiency of acid β-glucosidase, the natural substrates of which (β-d-glucosylceramide and β-d-glucosylsphingosine) accumulate, principally in macrophages. Mice with inducible deficiency of β-glucosidase [Gba(tm1Karl/tm1Karl)Tg(MX1-cre)1Cgn/0] serve as an authentic model of human Gaucher disease; we have recently reported clonal B-cell proliferation accompanied by monoclonal serum paraproteins and cognate tumours in these animals. To explore the relationship between B-cell malignancy and the biochemical defect, we treated Gaucher mice with eliglustat tartrate (GENZ 112638), a potent and selective inhibitor of the first committed step in glycosphingolipid biosynthesis. Twenty-two Gaucher mice received 300 mg/kg of GENZ 112638 daily for 3-10 months from 6 weeks of age. Plasma concentrations of β-d-glucosylceramide and the unacylated glycosphingolipid, β-d-glucosylsphingosine, declined. After administration of GENZ 112638 to Gaucher mice for 3-10 months, serum paraproteins were not detected and there was a striking reduction in the malignant lymphoproliferation: neither lymphomas nor plasmacytomas were found in animals that had received the investigational agent. In contrast, 14 out of 60 Gaucher mice without GENZ 112638 treatment developed these tumours; monoclonal paraproteins were detected in plasma from 18 of the 44 age-matched mice with Gaucher disease that had not received GENZ 112638. Long-term inhibition of glycosphingolipid biosynthesis suppresses the development of spontaneous B-cell lymphoma and myeloma in Gaucher mice.

Management of bone disease in Gaucher disease type 1: clinical practice

Gaucher disease is a rare autosomal recessive disorder of glycosphingolipid metabolism resulting from deficient activity of the lysosomal enzyme beta-glucocerebrosidase that causes accumulation of glucosylceramide in tissue macrophage with damage to hematological, visceral, and skeletal organ systems. Severity and progression may vary independently among these domains, necessitating individualized therapy. Skeletal involvement is highly prevalent and often associated with intense pain, impaired mobility, and reduced quality of life. Enzyme replacement therapy improves parameters in all affected domains, but skeletal involvement requires longer treatment and higher dosages to obtain significant results. Despite numerous papers on bone complications in patients with Gaucher disease, there are no specific indications on how to assess properly bone involvement in such condition, the frequency of assessment, the use of markers for osteoblast and osteoclast activity, or the administration of bisphosphonates or other symptomatic drugs in adult and pediatric patients. Starting from a re-evaluation of cases with bone involvement, we have identified some common errors in the diagnostic approach and management. The aim of this paper was to propose a methodological and critical approach to the diagnosis, follow-up and treatment of bone disease in patients with Gaucher disease type 1.

Gaucher disease and bone manifestations

Gaucher disease is a relatively rare metabolic disease caused by the inherited deficiency of the lysosomal enzyme glucocerebrosidase. Gaucher disease affects multiple organs, among which is the skeleton. Bone involvement occurs frequently in Gaucher disease, and is one of its most debilitating features, reducing the quality of life of patients. Bone status is an important consideration for treatment to ameliorate symptoms and reduce the risk of irreversible complications. We have conducted a systematic review of all the various aspects of Gaucher disease, focusing on different skeletal manifestations, pathophysiology of bone alterations, clinical symptoms, and current diagnostic and therapeutic approaches.

Gaucher disease and its treatment options

OBJECTIVE

To review the epidemiology, pathophysiology, and treatments of Gaucher disease (GD), focusing on the role of enzyme replacement therapy (ERT), andsubstrate reduction therapy (SRT).

DATA SOURCES

A literature search through PubMed (1984-May 2013) of English language articles was performed with terms: Gaucher's disease, lysosomal storage disease. Secondary and tertiary references were obtained by reviewing related articles.

STUDY SELECTION AND DATA EXTRACTION

All articles in English identified from the data sources, clinical studies using ERT, SRT and articles containing other interesting aspects were included.

DATA SYNTHESIS

GD is the most common inherited LSD, characterized by a deficiency in the activity of the enzyme acid β-glucosidase, which leads to accumulation of glucocerebroside within lysosomes of macrophages, leading to hepatosplenomegaly, bone marrow suppression, and bone lesions. GD is classified into 3 types: type 1 GD (GD1) is chronic and non-neuronopathic, accounting for 95% of GDs, and types 2 and 3 (GD2, GD3) cause nerve cell destruction. Regular monitoring of enzyme chitotriosidase and pulmonary and activation-regulated chemokines are useful to confirm the diagnosis and effectiveness of GD treatment.

CONCLUSIONS

There are 4 treatments available for GD1: 3 ERTs and 1 SRT. Miglustat, an SRT, is approved for mild to moderate GD1. ERTs are available for moderate to severe GD1 and can improve quality of life within the first year of treatment. The newest ERT, taliglucerase alfa, is plant-cell derived that can be produced on a large scale at lower cost. Eliglustat tartrate, another SRT, is under phase 3 clinical trials. No drugs have been approved for GD2 or GD3.

Bone disease in patients with Gaucher disease

Gaucher disease is an inborn error of metabolism due to a deficiency of the lysosomal enzyme glucocerebrosidase. As a result of this deficiency, the substrate glucocerebroside accumulates in the liver, spleen, bone and bone marrow. Bone involvement can lead to abnormalities in bone growth, bone remodeling, bone infarcts, aseptic necrosis, osteonecrosis, increased fracture risk and lytic bone lesions. Patients may experience bone pain and bone crises related to bone infarcts. There is evidence of abnormal bone metabolism in both bone resorption and bone formation based upon biochemical abnormalities found in patients. In addition, both immunological and coagulation abnormalities have in part been implicated in the causation of bone disease. Treatment with enzyme replacement therapy and substrate reduction therapy has led to improvement in both the symptoms and the radiographic abnormalities seen in these patients. It is unknown whether these treatments lower fracture risk.

Ambroxol improves lysosomal biochemistry in glucocerebrosidase mutation-linked Parkinson disease cells

Heterozygous GBA gene mutations are the most frequent Parkinson’s disease risk factor. Using Parkinson’s disease patient derived fibroblasts McNeill et al. show that heterozygous GBA mutations reduce glucosylceramidase activity, and are associated with endoplasmic reticulum and oxidative stress. Ambroxol treatment improved glucosylceramidase activity and reduced oxidative stress in these cells.

Gaucher disease is caused by mutations in the glucocerebrosidase gene, which encodes the lysosomal hydrolase glucosylceramidase. Patients with Gaucher disease and heterozygous glucocerebrosidase mutation carriers are at increased risk of developing Parkinson’s disease. Indeed, glucocerebrosidase mutations are the most frequent risk factor for Parkinson’s disease in the general population. Therefore there is an urgent need to understand the mechanisms by which glucocerebrosidase mutations predispose to neurodegeneration to facilitate development of novel treatments. To study this we generated fibroblast lines from skin biopsies of five patients with Gaucher disease and six heterozygous glucocerebrosidase mutation carriers with and without Parkinson’s disease. Glucosylceramidase protein and enzyme activity levels were assayed. Oxidative stress was assayed by single cell imaging of dihydroethidium. Glucosylceramidase enzyme activity was significantly reduced in fibroblasts from patients with Gaucher disease (median 5% of controls, P = 0.0001) and heterozygous mutation carriers with (median 59% of controls, P = 0.001) and without (56% of controls, P = 0.001) Parkinson’s disease compared with controls. Glucosylceramidase protein levels, assessed by western blot, were significantly reduced in fibroblasts from Gaucher disease (median glucosylceramidase levels 42% of control, P < 0.001) and heterozygous mutation carriers with (median 59% of control, P < 0.001) and without (median 68% of control, P < 0.001) Parkinson’s disease. Single cell imaging of dihydroethidium demonstrated increased production of cytosolic reactive oxygen species in fibroblasts from patients with Gaucher disease (dihydroethidium oxidation rate increased by a median of 62% compared to controls, P < 0.001) and heterozygous mutation carriers with (dihydroethidium oxidation rate increased by a median of 68% compared with controls, P < 0.001) and without (dihydroethidium oxidation rate increased by a median of 70% compared with controls, P < 0.001) Parkinson’s disease. We hypothesized that treatment with the molecular chaperone ambroxol hydrochloride would improve these biochemical abnormalities. Treatment with ambroxol hydrochloride increased glucosylceramidase activity in fibroblasts from healthy controls, Gaucher disease and heterozygous glucocerebrosidase mutation carriers with and without Parkinson’s disease. This was associated with a significant reduction in dihydroethidium oxidation rate of ∼50% (P < 0.05) in fibroblasts from controls, Gaucher disease and heterozygous mutation carriers with and without Parkinson’s disease. In conclusion, glucocerebrosidase mutations are associated with reductions in glucosylceramidase activity and evidence of oxidative stress. Ambroxol treatment significantly increases glucosylceramidase activity and reduces markers of oxidative stress in cells bearing glucocerebrosidase mutations. We propose that ambroxol hydrochloride should be further investigated as a potential treatment for Parkinson’s disease.

Reduced glucocerebrosidase is associated with increased α-synuclein in sporadic Parkinson's disease

Heterozygous mutations in GBA1, the gene encoding lysosomal glucocerebrosidase, are the most frequent known genetic risk factor for Parkinson's disease. Reduced glucocerebrosidase and α-synuclein accumulation are directly related in cell models of Parkinson's disease. We investigated relationships between Parkinson's disease-specific glucocerebrosidase deficits, glucocerebrosidase-related pathways, and α-synuclein levels in brain tissue from subjects with sporadic Parkinson's disease without GBA1 mutations. Brain regions with and without a Parkinson's disease-related increase in α-synuclein levels were assessed in autopsy samples from subjects with sporadic Parkinson's disease (n = 19) and age- and post-mortem delay-matched controls (n = 10). Levels of glucocerebrosidase, α-synuclein and related lysosomal and autophagic proteins were assessed by western blotting. Glucocerebrosidase enzyme activity was measured using a fluorimetric assay, and glucocerebrosidase and α-synuclein messenger RNA expression determined by quantitative polymerase chain reaction. Related sphingolipids were analysed by mass spectrometry. Multivariate statistical analyses were performed to identify differences between disease groups and regions, with non-parametric correlations used to identify relationships between variables. Glucocerebrosidase protein levels and enzyme activity were selectively reduced in the early stages of Parkinson's disease in regions with increased α-synuclein levels although limited inclusion formation, whereas GBA1 messenger RNA expression was non-selectively reduced in Parkinson's disease. The selective loss of lysosomal glucocerebrosidase was directly related to reduced lysosomal chaperone-mediated autophagy, increased α-synuclein and decreased ceramide. Glucocerebrosidase deficits in sporadic Parkinson's disease are related to the abnormal accumulation of α-synuclein and are associated with substantial alterations in lysosomal chaperone-mediated autophagy pathways and lipid metabolism. Our data suggest that the early selective Parkinson's disease changes are likely a result of the redistribution of cellular membrane proteins leading to a chronic reduction in lysosome function in brain regions vulnerable to Parkinson's disease pathology.

Enhanced differentiation of osteoclasts from mononuclear precursors in patients with Gaucher disease

Gaucher disease (GD) is an autosomal recessive disorder caused by deficiency of β-glucocerebrosidase. Storage of glucosylceramide in reticuloendothelial cells results in multiorgan pathology including bone disease. Established skeletal disease may remain problematic despite Gaucher-specific treatment. Both osteopenia and osteonecrosis have been described but the underlying pathophysiology, in particular the role of monocyte-derived osteoclasts is not well defined. The objective of this study was to explore the effect of glucocerebrosidase deficiency, inhibition and replacement on osteoclast development and function. In cultures derived from GD patients, or where GBA was chemically inhibited multinucleate giant cells expressing markers of osteoclast differentiation occurred earlier and in greater numbers compared to normal controls and the functional capacity of osteoclasts for bone resorption was enhanced. Increases in osteoclast number and activity correlated with radiological markers of active bone disease. Abnormalities were reversed by addition of specific therapies and were attenuated by co-culture with cells derived from healthy controls (HCs). Numbers of osteoblast lineage cells in the peripheral blood were mismatched to osteoclast precursors indicating uncoupling of osteoblast-osteoclast regulation which may further impact on bone remodelling. Elucidation of the underlying mechanisms of these changes will suggest rational therapies for the most disabling aspect of this condition.

Gaucher disease

Gaucher disease is an autosomal recessive condition due to glucocerebrosidase deficiency responsible for the lysosomal accumulation of glucosylceramide, a complex lipid derived from cell membranes, mainly in macrophages. It is due to mutations mostly in the GBA gene, although saposine C deficiency is due to mutations in the PSAP gene. It encompasses an extremely heterogeneous spectrum of clinical involvement from the fetus to adulthood. Splenomegaly, blood cytopenia, and bone involvement are the main manifestations of Gaucher disease, but nervous system degeneration is observed in about 5-10% of patients. The accumulation in neurons of glucosylceramide and its derivative, psychosine, are thought to underlie neuronal dysfunction and death, although Gaucher cells that mostly accumulate such substances are mainly macrophages. Enzyme replacement therapy dramatically improves the outcome of patients because of its extreme efficacy in the treatment of the systemic involvement. However, it has only limited effects on most neurological signs.

Analysis of crucial molecules involved in herniated discs and degenerative disc disease

OBJECTIVES

Herniated discs and degenerative disc disease are major health problems worldwide. However, their pathogenesis remains obscure. This study aimed to explore the molecular mechanisms of these ailments and to identify underlying therapeutic targets.

MATERIAL AND METHODS

Using the GSE23130 microarray datasets downloaded from the Gene Expression Omnibus database, differentially co-expressed genes and links were identified using the differentially co-expressed gene and link method with a false discovery rate ,0.25 as a significant threshold. Subsequently, the underlying molecular mechanisms of the differential co-expression of these genes were investigated using Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. In addition, the transcriptional regulatory relationship was also investigated.

RESULTS

Through the analysis of the gene expression profiles of different specimens from patients with these diseases, 539 differentially co-expressed genes were identified for these ailments. The ten most significant signaling pathways involving the differentially co-expressed genes were identified by enrichment analysis. Among these pathways, apoptosis and extracellular matrix-receptor interaction pathways have been reported to be related to these diseases. A total of 62 pairs of regulatory relationships between transcription factors and their target genes were identified as critical for the pathogenesis of these diseases.

CONCLUSION

The results of our study will help to identify the mechanisms responsible for herniated discs and degenerative disc disease and provides a theoretical basis for further therapeutic study.

Abnormal properties of red blood cells suggest a role in the pathophysiology of Gaucher disease

Gaucher disease (GD) is a lysosomal storage disorder caused by glucocerebrosidase deficiency. It is notably characterized by splenomegaly, complex skeletal involvement, ischemic events of the spleen and bones, and the accumulation of Gaucher cells in several organs. We hypothesized that red blood cells (RBCs) might be involved in some features of GD and studied the adhesive and hemorheologic properties of RBCs from GD patients. Hemorheologic analyses revealed enhanced blood viscosity, increased aggregation, and disaggregation threshold of GD RBCs compared with control (CTR) RBCs. GD RBCs also exhibited frequent morphologic abnormalities and lower deformability. Under physiologic flow conditions, GD RBCs adhered more strongly to human microvascular endothelial cells and to laminin than CTR. We showed that Lu/BCAM, the unique erythroid laminin receptor, is overexpressed and highly phosphorylated in GD RBCs, and may play a major role in the adhesion process. The demonstration that GD RBCs have abnormal rheologic and adhesion properties suggests that they may trigger ischemic events in GD, and possibly phagocytosis by macrophages, leading to the appearance of pathogenic Gaucher cells.

Reduced cathepsins B and D cause impaired autophagic degradation that can be almost completely restored by overexpression of these two proteases in Sap C-deficient fibroblasts

Saposin (Sap) C deficiency, a rare variant form of Gaucher disease, is due to mutations in the Sap C coding region of the prosaposin (PSAP) gene. Sap C is required as an activator of the lysosomal enzyme glucosylceramidase (GCase), which catalyzes glucosylceramide (GC) degradation. Deficit of either GCase or Sap C leads to the accumulation of undegraded GC and other lipids in lysosomes of monocyte/macrophage lineage. Recently, we reported that Sap C mutations affecting a cysteine residue result in increased autophagy. Here, we characterized the basis for the autophagic dysfunction. We analyzed Sap C-deficient and GCase-deficient fibroblasts and observed that autophagic disturbance was only associated with lack of Sap C. By a combined fluorescence microscopy and biochemical studies, we demonstrated that the accumulation of autophagosomes in Sap C-deficient fibroblasts is not due to enhanced autophagosome formation but to delayed degradation of autolysosomes caused, in part, to decreased amount and reduced enzymatic activity of cathepsins B and D. On the contrary, in GCase-deficient fibroblasts, the protein level and enzymatic activity of cathepsin D were comparable with control fibroblasts, whereas those of cathepsin B were almost doubled. Moreover, the enhanced expression of both these lysosomal proteases in Sap C-deficient fibroblasts resulted in close to functional autophagic degradation. Our data provide a novel example of altered autophagy as secondary event resulting from insufficient lysosomal function.

Modulation of bone turnover in orchidectomized rats treated with raloxifene and risedronate

Osteoporosis is a reduction in bone mineral density (BMD). It develops less often in men than in women. This study aimed to evaluate the bone protective effects of raloxifene (RAL), risedronate (RIS), and their combination on osteoporotic male rats. Forty male Wister rats (12 weeks) were randomly divided into five groups: sham-operated group (n = 8), orchidectomized (ORX) group (n = 7), RAL group (n = 9), RIS group (n = 7) and RAL + RIS group (n = 7). RAL was orally administered at 3 mg/kg three times/week, and RIS was given subcutaneously at 5 μg/kg, twice weekly. After 6 weeks of treatment, serum cathepsin-K, alkaline (ALP) and acid phosphatase activities, serum osteocalcin, serum Ca²⁺, and Pi were determined. Urinary Ca²⁺ and deoxypyridinoline levels, BMD, and Ca²⁺ content of femur ash were estimated. Histochemical localization of ALP activity of tibia and histomorphometry was examined. As compared to sham, ORX rats showed a significant increase in bone turnover markers, and histochemical activity of ALP was increased markedly in proximal tibia of ORX rats, whereas BMD and Ca²⁺ content of femur ash were reduced after ORX. These changes were modulated after treatment with RAL and RIS or both to ORX rats; BMD of femur was improved by each treatment, and bone turnover markers were reduced as compared to ORX vehicle group. We concluded that orchidectomy induced osteoporosis and increased bone turnover in male rats because of withdrawal of sex hormones. Both RAL and RIS could treat osteoporosis in ORX rats; they reduced bone turnover markers and maintained BMD.

Miscellaneous non-inflammatory musculoskeletal conditions. Gaucher disease and bone

Gaucher disease (GD) is an inherited lysosomal storage disorder affecting multiple organs. Non-neuronopathic GD, the most common form, can present with hepatosplenomegaly, anaemia, bleeding tendencies, thrombocytopenia, skeletal pathologies, growth retardation and, in severe cases, with pulmonary disease. The bone manifestations include bone infarcts, avascular bone necrosis, lytic lesions, osteosclerosis, fractures due to osteoporosis and, rarely, acute osteomyelitis. Bone pain of varying intensity, fractures and joint collapses increase the patients' morbidity and impair their mobility and quality of life. Currently available therapies - enzyme replacement therapy and substrate reduction therapy - have shown to improve blood count and the visceral manifestations within a short time. Beneficial effects have also been documented on bone pain, bone crises and the extent of osteoporosis. The article focusses on the bone pathologies of GD including its pathophysiology, current diagnostics, clinical management and therapeutic effects of enzyme replacement therapy, substrate reduction therapy and bone-specific therapies.

The cellular pathology of lysosomal diseases

With a constitutive recycling function and the capacity to digest exogenous material as well as endogenous organelles in the process of autophagy, lysosomes are at the heart of the living cell. Dynamic interactions with other cellular components ensure that the lysosomal compartment is a central point of convergence in countless diverse diseases. Inborn lysosomal (storage) diseases represent about 70 genetically distinct conditions, with a combined birth frequency of about 1 in 7500. Many are associated with macromolecular storage, causing physical disruption of the organelle and cognate structures; in neurons, ectopic dendritogenesis and axonal swelling due to distension with membraneous tubules and autophagic vacuoles are observed. Disordered autophagy is almost universal in lysosomal diseases but biochemical injury due to toxic metabolites such as lysosphingolipid molecules, abnormal calcium homeostasis and endoplasmic reticulum stress responses and immune-inflammatory processes occur. However, in no case have the mechanistic links between individual clinico-pathological manifestations and the underlying molecular defect been precisely defined. With access to the external fluid-phase and intracellular trafficking pathways, the lysosome and its diseases are a focus of pioneering investment in biotechnology; this has generated innovative orphan drugs and, in the case of Gaucher's disease, effective treatment for the haematological and visceral manifestations. Given that two-thirds of lysosomal diseases have potentially devastating consequences in the nervous system, future therapeutic research will require an integrative understanding of the unitary steps in their neuro pathogenesis. Informative genetic variants illustrated by patients with primary defects in this organelle offer unique insights into the central role of lysosomes in human health and disease. We provide a conspectus of inborn lysosomal diseases and their pathobiology; the cryptic evolution of events leading to irreversible changes may be dissociated from the cellular storage phenotype, as revealed by the outcome of therapeutic gene transfer undertaken at different stages of disease.

Biomarkers for osteonecrosis in Gaucher disease

INTRODUCTION

The search for surrogate biomarkers of osteonecrosis, a disabling complication of Gaucher disease, has intensified in the last decade. Biomarkers that predict osteonecrosis and monitor the effectiveness of therapies would improve clinical practice and enrich the molecular exploration of this disorder.

AREAS COVERED

Here we discuss advances in biomarker research with special reference to those biomarkers associated with Gaucher disease and investigated in the context of enzyme therapy. Much progress has been made in the diversification of treatment for the condition and several biomarker molecules, which may ultimately improve risk assessment for osteonecrosis, have been identified.

EXPERT OPINION

The discovery of prospective biomarkers of osteonecrosis such as CCL18/PARC, CXCL8/IL-8, CCL5/RANTES, CCL3/MIP-1α, CCL4/MIP-1β, particularly during recurrent episodes occurring despite enzyme treatment, has the potential radically to change practices in the management of Gaucher disease and should improve therapeutic monitoring and prognostic evaluation. Ultimately, exploration of this field will provide the basis for a refined mechanistic understanding of pathogenesis.

Bilateral symmetrical cortical osteolytic lesions in two patients with Gaucher disease

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder characterized by the reduced or absent activity of glucocerebrosidase. The disease is split into three types. Type 3, or chronic neuronopathic GD, manifests with heterogeneous clinical presentations. Skeletal manifestations of GD can include abnormal bone remodeling resulting in the characteristic Erlenmeyer flask deformities, painful bone crises, osteopenia, and an increased frequency of fractures. Osteolytic lesions can also occur but are rare and tend to be large, expanding intramedullary lesions with cortical thinning. We present two adolescent patients with type 3 GD who developed bilateral symmetrical cortical osteolytic lesions. The lesions in both cases demonstrate predominant cortical scalloping with fairly indolent growth. Neither patient manifests some of the more common bony manifestations of GD--bone crises or osteonecrosis. These atypical and unique skeletal findings in two unrelated probands with type 3 GD further expand the extent of phenotypic variation encountered in this single gene disorder.

Bone marrow microenvironment in an in vitro model of Gaucher disease: consequences of glucocerebrosidase deficiency

Gaucher disease (GD) is a lysosomal storage disorder due to glucocerebrosidase (GBA) deficiency. Mechanisms leading to the emergence of hematological and skeletal manifestations observed in GD are poorly explained. Bone marrow (BM) mesenchymal stem cells (MSCs) are multipotent progenitors that participate in the regulation of bone mass. MSCs should thus represent a cell population involved in the development or progression of bone disease in GD. In a chemical model of GD obtained with Conduritol β epoxide (CBE), a specific inhibitor of GBA activity, we functionally characterized BM MSCs and specifically analyzed their capacity to differentiate into osteoblasts. GBA deficiency obtained with CBE treatment, leads to a dramatic impairment of MSCs proliferation and to morphological abnormalities. Although the capacity of MSCs to differentiate into osteoblasts was not modified, the levels of several soluble factors that regulate bone metabolism were increased in MSCs treated with CBE, compared with untreated MSCs. Moreover, addition of conditioned media from CBE-treated MSCs on monocyte-derived osteoclasts cultured on bone matrix leads to an increase of resorption areas. These data suggested that, in GD, MSCs represents a stem cell population that is likely to be involved in bone pathogenesis.

Biomarkers in the diagnosis of lysosomal storage disorders: proteins, lipids, and inhibodies

A biomarker is an analyte indicating the presence of a biological process linked to the clinical manifestations and outcome of a particular disease. In the case of lysosomal storage disorders (LSDs), primary and secondary accumulating metabolites or proteins specifically secreted by storage cells are good candidates for biomarkers. Clinical applications of biomarkers are found in improved diagnosis, monitoring disease progression, and assessing therapeutic correction. These are illustrated by reviewing the discovery and use of biomarkers for Gaucher disease and Fabry disease. In addition, recently developed chemical tools allowing specific visualization of enzymatically active lysosomal glucocerebrosidase are described. Such probes, coined inhibodies, offer entirely new possibilities for more sophisticated molecular diagnosis, enzyme replacement therapy monitoring, and fundamental research.