Bone Tissue Homeostasis Research Articles

Pathogen profile and MMP-3 levels in areas with varied attachment loss in generalized aggressive and chronic periodontitis.

IntroductionThe progression of periodontitis depends on the changes in bone and connective tissue homeostasis and the imbalance of the biofilm and the host immunoinflammatory response, particularly matrix metalloproteinases (MMP).Aim of the studyTo assess the probable relation between subgingival anaerobic flora and the expression of MMP-3 in patients with generalized aggressive periodontitis (AgP), chronic periodontitis (CP) and healthy subjects, and to evaluate these levels according to varied tissue loss severity.Material and methodsThe plaque index (PI), gingival index (GI), probing depth (PD) and clinical attachment levels (CAL) were evaluated. MMP levels obtained from gingival sulcus fluid (GCF) were measured with Enzyme Linked Immuno Assay (ELISA). The bacterial counts were determined with Parocheck®.ResultsHigher levels of MMP-3 in patients with AgP compared to subjects with CP and healthy individuals were observed. The microorganisms responsible of possible tissue destruction in both AgP and CP are red complex bacteria. T. denticola, T. forsythia, P. intermedia and F. nucleatum show positive correlation with MMP-3 levels.ConclusionsMMP-3 is a biomarker associated with AgP, and red complex bacteria levels are correlated with increasing periodontal tissue loss in both periodontitis forms. The diagnosis of aggressive periodontitis, or site-specific treatment strategies can be orchestrated based on the evaluation of MMP-3 and the bacterial counts in patients with periodontitis.

Wnt signaling in bone, kidney, intestine, and adipose tissue and interorgan interaction in aging

Over the last two decades, it has become increasingly apparent that Wnt signaling plays a critical role in development and adult tissue homeostasis in multiple organs and in the pathogenesis of many diseases. In particular, a crucial role for Wnt signaling in bone development and bone tissue homeostasis has been well recognized. Numerous genome-wide association studies confirmed the importance of Wnt signaling in controlling bone mass. Moreover, ample evidence suggests that Wnt signaling is essential for kidney, intestine, and adipose tissue development and homeostasis. Recent emerging evidence demonstrates that Wnt signaling may play a fundamental role in the aging process of those organs. New discoveries show that bone is not only the major reservoir for calcium and phosphate storage, but also the largest organ with multiple functions, including mineral and energy metabolism. The interactions among bone, kidney, intestine, and adipose tissue are controlled and regulated by several endocrine signals, including FGF23, klotho, sclerostin, osteocalcin, vitamin D, and leptin. Since the aging process is characterized by structural and functional decline in almost all tissues and organs, understanding the Wnt signaling-related interactions among bone, kidney, intestine, and adipose tissue in aging may shed light on the pathogenesis of age-related diseases.

Bone and Soft Tissue Turnover in Relation to All-cause Mortality in Postmenopausal Women.

The relationship between levels of extracellular matrix (ECM) turnover and mortality is currently unknown. The study aimed to determine if levels of ECM turnover are predictors of all-cause mortality in a large cohort of postmenopausal women. 5,855 postmenopausal Danish women enrolled in the Prospective Epidemiologic Risk Factor (PERF) study. Baseline demographics and serum were collected at registration. Dates of death were obtained from the Danish Death Registry. ECM turnover was evaluated by serological biomarkers measuring bone (telopeptide of type I collagen [CTX-1] and osteocalcin) and soft tissue (formation of type VI collagen [PRO-C6], MMP-degraded type IV collagen [C4M], formation of type III collagen [PRO-C3], and MMP-degraded type I collagen [C1M]) turnover. Multivariate Cox analyses were performed with 3, 5, and 15 years of follow-up. The association of bone turnover (CTX-1 and osteocalcin) with all-cause mortality was U-shaped for all time periods. After adjustment for possible confounders, the lowest quintile of bone formation and degradation remained significant for all time periods. We observed J-shaped association between all-cause mortality and PRO-C6, C4M, and PRO-C3, and there was a linear association between C1M and all-cause mortality. After adjustment for possible confounders, the highest quintile of the soft tissue turnover biomarkers (PRO-C6, C4M, PRO-C3, and C1M) remained significantly associated with all-cause mortality for all time periods. Both low and high levels of tissue turnover were associated with increased risk of all-cause mortality in postmenopausal women. Overall, these results highlight the importance of bone and soft tissue homeostasis.

The Effects of Radiation and Hindlimb Unloading on Rat Bone Marrow Progenitor Cells

Bone marrow cells of mesenchymal origin play an important role in adaptation of physiological systems to space flight. Hematopoiesis, immunity, and homeostasis of bone tissue depend on their functional activity. An investigation that was carried out in the framework of the Bion and Bion-M programs showed a decrease of the number of rat bone marrow hematopoietic progenitors and the inhibition of lympho- and erythropoiesis when the granulocyte-macrophage linage was activated. A negative influence on nonhematopoietic bone marrow cells was also revealed. The pathogenetic influence of radiation and microgravity on the bone marrow progenitor cells has remained unclear so far. The goal of this research was to study the effect of a 30-day unloading and 6 days of γ-irradiation on rat bone marrow progenitor cells. The study was conducted on male rats of four groups: vivarium control (VC), hindlimb unloading (HU), irradiation (IR), and combined action (HU + IR). The following parameters have been examined: the number of bone marrow mononuclear cells, proliferative activity of marrow mononuclear cells, immunophenotype, number of hematopoietic CFU and CFU-f, and differentiation potency of hematopoietic and stromal bone marrow precursors. It was found that the cellularity and proliferation activity of rat bone marrow cells did not change under simulation of space flight. The number of CFU-f was decreased. Irradiation was accompanied by an increase in the hematopoietic cell share among total bone marrow mononuclear cells, while their activity was attenuated. The osteopotential of the stromal precursors was unchanged. Adipogenic differentiation was stimulated with irradiation. The functional activity of bone marrow progenitor cells was restored after 2 weeks of recovery. Thus, 30-day simulation of space flight factors negatively affected the morphofunctional properties of rat bone marrow progenitor cells. These effects were reversible upon 2 weeks of recovery.

Osteogenic Factor Runx2 Marks a Subset of Leptin Receptor-Positive Cells that Sit Atop the Bone Marrow Stromal Cell Hierarchy

Bone marrow mesenchymal stem and progenitor cells (BM-MSPCs) maintain homeostasis of bone tissue by providing osteoblasts. Although several markers have been identified for labeling of MSPCs, these labeled cells still contain non-BM-MSPC populations. Studies have suggested that MSPCs are observed as leptin receptor (LepR)-positive cells, whereas osteoblasts can be classified as positive for Runx2, a master regulator for osteoblastogenesis. Here, we demonstrate, using Runx2-GFP reporter mice, that the LepR-labeled population contains Runx2-GFPlow sub-population, which possesses higher fibroblastic colony-forming units (CFUs) and mesensphere capacity, criteria for assessing stem cell activity, than the Runx2-GFP− population. In response to parathyroid hormone (PTH), a bone anabolic hormone, LepR+Runx2-GFPlow cells increase Runx2 expression and form multilayered structures near the bone surface. Subsequently, the multilayered cells express Osterix and Type I collagen α, resulting in generation of mature osteoblasts. Therefore, our results indicate that Runx2 is weakly expressed in the LepR+ population without osteoblastic commitment, and the LepR+Runx2-GFPlow stromal cells sit atop the BM stromal hierarchy.

Bioactive Molecule-loaded Drug Delivery Systems to Optimize Bone Tissue Repair

Bioactive molecules such as peptides and proteins can optimize the repair of bone tissue; however, the results are often unpredictable when administered alone, owing to their short biological half-life and instability. Thus, the development of bioactive molecule-loaded drug delivery systems (DDS) to repair bone tissue has been the subject of intense research. DDS can optimize the repair of bone tissue owing to their physicochemical properties, which improve cellular interactions and enable the incorporation and prolonged release of bioactive molecules. These characteristics are fundamental to favor bone tissue homeostasis, since the biological activity of these factors depends on how accessible they are to the cell. Considering the importance of these DDS, this review aims to present relevant information on DDS when loaded with osteogenic growth peptide and bone morphogenetic protein. These are bioactive molecules that are capable of modulating the differentiation and proliferation of mesenchymal cells in bone tissue cells. Moreover, we will present different approaches using these peptide and protein-loaded DDS, such as synthetic membranes and scaffolds for bone regeneration, synthetic grafts, bone cements, liposomes, and micelles, which aim at improving the therapeutic effectiveness, and we will compare their advantages with commercial systems.

Human type H vessels are a sensitive biomarker of bone mass

Vascularization is fundamental for bone formation and bone tissue homeostasis. However, in human subjects, a direct molecular relationship has not been identified between angiogenesis and agents that promote bone disease or factors related to age. Osteopenia is a condition in which bone mineral density is lower than normal, and it represents a sign of normal aging. Here we tested whether the type H vessel, which was recently identified as strongly positive for CD31 and Endomucin (CD31hiEmcnhi) in mice, is an important indicator of aging and osteopenia in human subjects. We found that age-dependent losses of type H vessels in human bone sections conform to the observations in aged mice. The abundance of human type H vessels and osteoprogenitors may be relevant to changes in the skeletal microarchitecture and advanced osteopenia. Furthermore, ovariectomized mice, a widely used model for postmenopausal osteoporosis, exhibited significantly reduced type H vessels accompanied by reduced osteoprogenitors, which is consistent with impaired bone microarchitecture and osteoporosis, suggesting that this feature is an indicator of bone mass independent of aging. More importantly, administration of desferrioxamine led to significantly increased bone mass via enhanced angiogenesis and increased type H vessels in ovariectomized mice. Altogether, these data represent a novel finding that type H vessels are regulated in aged and osteopenia subjects. The abundance of human type H vessels is an early marker of bone loss and represents a potential target for improving bone quality via the induction of type H vessels.

Macrophage and osteoclast polarization in bisphosphonate associated necrosis and osteoradionecrosis

PurposeBisphosphonate-related osteonecrosis of the jaw (BRONJ) is a complication of antiresorptive therapy with nitrogen-containing bisphosphonates (BP). With various suggestions as to pathogenesis, the etiology of BRONJ is not sufficiently understood. Osteoclasts and their precursors, that is, macrophages, are the main target cells of BP. BP can repolarize regeneration- and healing-associated M2 macrophages towards the tissue destructive M1-type. The current study aims to elucidate differences in macrophage and osteoclast polarization in BRONJ, osteoradionecrosis (ORN) and healthy control specimens. Materials and methodsA total of 39 jaw bone samples (18 BRONJ, 8 ORN and 13 healthy controls) were processed for immunohistochemistry to detect CD68-, CD11c- and CD163-positive cells. Macrophages and osteoclasts were distinguished on the basis of morphological differences. Samples were digitized, and the macrophage and osteoclast cell counts were quantitatively analyzed. ResultsIn jaw bone affected by BRONJ, a significantly increased macrophage infiltration and M1 polarization of macrophages can be seen. The density of CD68-expressing osteoclasts is significantly increased in BRONJ specimens compared to ORN and to healthy controls. ConclusionsA bisphosphonate-derived shift of macrophage polarization towards M1-polarized macrophages might impair bone tissue homeostasis and thus contribute to the pathogenesis of BRONJ. The observed increase in osteoclast density might be caused by BP-induced prolonged osteoclast survival.

Latest perspectives on macrophages in bone homeostasis.

Knowledge about macrophages residing in the bone, also known as osteal macrophages or osteomacs, is still limited. A hallmark of this peculiar myeloid population is the expression of macrophage markers distinct from the markers found on osteoclast surface. In bone, osteomacs are in contact with osteoblasts, where they are involved in regulating bone homeostasis. However, additional macrophage subtypes already present in the bone marrow or recruited from the blood circulation could have further functions, which could be all important for the maintenance of the bone architecture and its associated functions. Indeed, bone marrow macrophages have been found to eliminate apoptotic cells, particularly apoptotic osteoblasts through a process named efferocytosis. This phagocytic process plays an essential role in bone tissue homeostasis and new bone formation. In addition, bone marrow macrophages can influence the hematopoietic stem cell (HSC) niches. They contribute to the regulation of the HSC progenitor cell maintenance, mobilization, and function. To do so, macrophages secrete cytokines in steady state or during stress conditions. These cytokines influence hematopoiesis either by a direct effect on HSCs or through the control of stromal cells that are essential for the HSC niches. Interestingly, the similarities between the niches for HSCs and the niche for metastatic tumor cells support the possibility that bone-resident macrophages could control the homing of tumor cells and their proliferation within the bone. In general, macrophage role during metastatic processes is well described; however, their direct involvement in bone metastasis is a rising research area. In this review, we will highlight the macrophage functions in the skeleton, in the maintenance of the HCS niches, and their importance in bone metastasis.

Osteocyte Alterations Induce Osteoclastogenesis in an In Vitro Model of Gaucher Disease.

Gaucher disease (GD) is caused by mutations in the glucosylceramidase β (GBA 1) gene that confer a deficient level of activity of glucocerebrosidase (GCase). This deficiency leads to the accumulation of the glycolipid glucocerebroside in the lysosomes of cells, mainly in the monocyte/macrophage lineage. Its mildest form is Type I GD, characterized by non-neuronopathic involvement. Bone compromise is the most disabling aspect of the Gaucher disease. However, the pathophysiological aspects of skeletal alterations are not yet fully understood. The bone tissue homeostasis is maintained by a balance between resorption of old bone by osteoclasts and new bone formation by osteoblasts. A central player in this balance is the osteocyte as it controls both processes. We studied the involvement of osteocytes in an in vitro chemical model of Gaucher disease. The osteocyte cell line MLO-Y4 was exposed to conduritol-β-epoxide (CBE), an inhibitor of GCase, for a period of 7, 14 and 21 days. Conditioned media from CBE-treated osteocytes was found to induce osteoclast differentiation. GCase inhibition caused alterations in Cx43 expression and distribution pattern and an increase in osteocyte apoptosis. Osteoclast differentiation involved osteocyte apoptotic bodies, receptor activator of nuclear factor κ-B ligand (RANKL) and soluble factors. Thus, our results indicate that osteocytes may have a role to play in the bone pathophysiology of GD.

Clinical aspects and importance of nutrition in homeostasis of the bone tissue

Substantial changes have occurred in the nutritional management of many diseases in the last twenty years. Introduction of standards, clinical review and implementation of evidence based practice led to re-evaluation of some established dietary interventions. The most common form of osteoporosis is the primary osteoporosis, which is the result of the bone loss and deterioration of bone structure, as people age. Bone loss and osteoporosis can be prevented through adequate nutrition, physical activity, and, if necessary, appropriate treatment. This review will focus on nutritional and clinical aspects of bone tissue homeostasis, with references to physiological and pathophysiological processes.

Circulating microRNA Signatures in Patients With Idiopathic and Postmenopausal Osteoporosis and Fragility Fractures.

Established bone turnover markers do not reflect fracture risk in idiopathic male and premenopausal osteoporosis and the role of microRNAs (miRNAs) in these patients is currently unclear. miRNAs are a class of small non-coding RNAs that regulate gene expression and bone tissue homeostasis. They are considered a new class of endocrine regulators with promising potential as biomarkers. Evaluation of circulating miRNA signatures in male and female subjects with idiopathic and postmenopausal osteoporotic low-traumatic fractures. This was a case-control study of cross-sectional design of 36 patients with prevalent low-traumatic fractures and 39 control subjects Main Outcome Measures: One hundred eighty-seven miRNAs were quantified in serum by qPCR, compared between groups and correlated with established bone turnover markers. Significant differences in serum levels of circulating miRNAs were identified in all three subgroups (46 in premenopausal, 52 in postmenopausal, 55 in male). A set of 19 miRNAs was consistently regulated in all three subgroups. Eight miRNAs [miR-152-3p, miR-30e-5p, miR-140-5p, miR-324-3p, miR-19b-3p, miR-335-5p, miR-19a-3p, miR-550a-3p] were excellent discriminators of patients with low-traumatic fractures, regardless of age and sex, with area under the curve values > 0.9. The 11 remaining miRNAs showed area under the curve values between 0.81 and 0.89. Correlation analysis identified significant correlations between miR-29b-3p and P1NP, and miR-365-5p and iPTH, TRAP5b, P1NP and Osteocalcin, as well as BMDL1-L4 and miR-19b-3p, miR-324-3p, miR-532-5p, and miR-93-5p. Specific serum miRNA profiles are strongly related to bone pathologies. Therefore miRNAs might be directly linked to bone tissue homeostasis. In particular, miR-29b-3p has previously been reported as regulator of osteogenic differentiation and could serve as a novel marker of bone turnover in osteoporotic patients as a member of a miRNA signature.

17β-estradiol regulates the differentiation of cementoblasts via Notch signaling cascade

Estrogen has been well recognized as a key factor in the homeostasis of bone and periodontal tissue, but the way it regulates the activities of cementoblasts, the cell population maintaining cementum has not been fully understood. In this study, we examined the expression of estrogen receptor in OCCM-30 cells and the effect of 17β-estradiol (E2) on the proliferation and differentiation of OCCM-30 cells. We found that both estrogen receptor α and β were expressed in OCCM-30 cells. E2 exerted no significant influence on the proliferation of OCCM-30 cells, but inhibited the transcription and translation of BSP and Runx2 in the early phase of osteogenic induction except the BSP mRNA. Afterwards in the late phase of osteogenic induction, E2 enhanced the transcription and translation of BSP and Runx2 and promoted the calcium deposition.In addition, the expression level of Notch1, NICD and Hey1 mRNAs responded to exogenous E2 in a pattern similar to that of the osteoblastic markers. DAPT could attenuate the effect of E2 on the expression of osteoblastic markers. These findings indicated that E2 might regulate the differentiation of cementoblasts via Notch signaling.

Hippo signaling protein MST1 regulates osteoclast differentiation by interacting with integrin linked kinase (ILK) and modulating actin structures

Hippo signaling is implicated in balancing cell proliferation, differentiation and death in multiple organs. However, its role in specific bone cell types such as osteoclasts, and its significance in maintaining overall bone tissue homeostasis remain largely unknown. In this study, we investigated the role of the Hippo pathway in osteoclast differentiation. Human primary monocyte cells were treated with receptor activator nuclear factor kappaB ligand (RANKL) and evaluated for osteoclast differentiation by marker protein analysis, tartrate-resistant acid phosphate (TRAP) and resorption assays. Our results showed that Ste20-like kinase 1 (MST1) underwent the maximum change after RANKL treatments and is negatively associated with osteoclast differentiation. Furthermore, proteomic approaches involving coimmunoprecipitation and mass spectrometry identified MST1 interaction with integrin-linked kinase (ILK) which is lost during RANKL induced differentiation. Finally, using RNAi and ectopic expression experiments we observed that MST1-ILK interaction negatively inhibits osteoclast differentiation at the level of actin ring structure formation, which is facilitated by ILK. Together, our data highlight a role for the Hippo pathway protein, MST1, in negatively regulating osteoclast differentiation through its interaction with integrin signaling. Given that integrin signaling is progressively implicated in pathological osteolysis, augmenting this pathway could have therapeutic implications.

The expression and function of microRNAs in bone homeostasis.

microRNAs (miRNAs) are a class of small, endogenous, non-coding single strand RNAs. miRNAs are involve in multiple developmental events during embryogenesis and adult tissue homeostasis. miRNAs regulate epigenetic regulating genes through post-transcriptional regulation and that epigenetic factors mediate the regulation of miRNA. Bone tissue homeostasis is maintained through the dynamic balance between osteoclastic bone resorption and osteoblastic bone formation. And miRNAs are important regulators of bone resorbing activity mediated by osteoclasts, as well as osteoblast proliferation and differentiation. This review summarizes recent studies bone-regulating miRNAs, which are divided into two major branches: the osteogenesis regulator and the osteoclastogenesis regulator. miRNAs can positively or negatively regulate osteogenesis and osteoclastogenesis. This review also discusses how miRNAs, target genes, intracellular effectors and transcription factors affect both the bone homeostasis and bone homeostasis processes. Disrupted the function of miRNAs is related to some bone diseases, such as osteoporosis. Studying the mechanisms underlying the role of miRNAs in the bone and mineral field may reveal potential therapeutic targets for treating metabolic bone disorders, bone loss and bone diseases.

Vascularization Strategies for Bone Regeneration

The functional regeneration of thick vascularized tissues such as bone and muscle is complicated by the large volume of lost tissue, challenging biomechanical environment, and the need to reproduce the highly organized structure of both the native tissue extracellular matrix and its vascular support system. Stem cell or progenitor cell delivery approaches, for example, continue to be plagued by low viability and engraftment in part due to the initial absence of a vascular supply. Recognition of diffusion limitations in thick tissues has prompted regenerative strategies that seek to accelerate establishment of a functional vasculature. The successful design of robust regeneration strategies for these challenging clinical scenarios will rely on a thorough understanding of interactions between construct design parameters and host biological and biomechanical factors. Here, we discuss the critical role of vascularization in normal bone tissue homeostasis and repair, vascular network adaptation to the local biomechanical environment, and the future directions of revascularization approaches being developed and integrated with bone regeneration strategies.

TCIRG1 Associated Congenital Neutropenia

▪Severe congenital neutropenia (SCN) is a rare autosomal dominant hematopoietic disorder with an estimated incidence of 1 in 200,000 for individuals of European descent. Although several causal genes have been identified, the genetic basis for >30% of cases remains unknown. We report finding a novel single nucleotide variant (SNV) R736S identified in TCIRG1, utilizing SNP chip analysis, whole exome sequencing and confirmatory Sanger sequencing, in a multi-generation family (median blood neutrophil counts 0.486 x 109/L, range 0.074 to 1.235 x 109/L for 11 affected members and 3.808 x 109/L, range 1.548 to 6.488 x 109/L for 7 unaffected members). There is a perfect cosegregation of the variant with neutropenia in this family; all 11 affected, but none of the unaffected individuals share this novel variant.TCIRG1 is located at 11q13 and encodes the vacuolar H+-ATPase a3 subunit, a 116-kD component of V-ATPases called OC116, and is essential for bone tissue maintenance and homeostasis. Homozygous or compound heterozygous mutations in this gene cause autosomal recessive malignant osteopetrosis (arOP) characterized by bone resorption defect due to osteoclast malfunction. Interestingly, the same gene, through an alternative splicing and usage of an alternative initiation codon in exon 7, gives rise to another protein, i.e., TIRC7, which is a T cell-specific membrane protein demonstrated to play an essential role for T-lymphocyte activation and immune response. Recent publications suggest the existence of additional splice variants expressed in various tissues in normal volunteers. SCN due to mutations in TCIRG1 have not been previously described.The arginine (R) to serine (S) substitution is a critical change because arginine at position 736 is essential for proton translocation and is evolutionarily highly conserved with a Genomic Evolutionary Rate Profiling (GERP) score = 3.78. Although direct structural data on TCIRG1's protein products are lacking, the effect of this mutation on the protein structure is predicted to be “probably damaging” by Polyphen (an automatic tool for prediction of possible impact of an amino acid substitution on the structure and function of the protein).Western blot analysis of protein products of this gene performed using peripheral blood mononuclear cells show reduced expression of TCIRG1 protein in the affected family members from this family utilizing a commercially available polyclonal antibody developed against the N-terminal cytoplasmic domain of human OC116. The ∼45kDa TCIRG1 product was down-regulated by 26%, 49%, and 35% in the 3 affected individuals, compared to 2 normal controls. Another antibody, raised against the TCIRG1 fragment 121aa-220aa, detects a ∼120 kDa protein band with similar expression levels in both affected individuals and healthy controls. These assays confirm the multi-product nature of TCIRG1 and suggest deregulatory involvement of this protein in the pathogenesis of the neutropenia in this family.Sanger sequencing of additional 20 unrelated SCN patients known to be negative for mutations in the known causal genes, revealed two different SNVs in TCIRG1 in two unrelated SCN patients, based on Minor Allele Frequency < 0.5% and high conservation among mammals (GERP score > 3). The first variant, g.16065 G>A, (IVS 14 -1G>A), is located in the acceptor splice site of the intron 14, and predicted to alter the splicing. The second variant, c.479 G>A (p.GLY160GLU), is located in exon 5 and predicted to be possibly damaging by Polyphen. No other SNV's predicted to alter protein structure have been found.We conclude that mutations in TCIRG1 are a rare but important cause of autosomal dominant congenital neutropenia. Further studies are in progress to define the pathophysiological mechanisms for neutropenia and the importance of the vATPases in maintaining the integrity of neutrophil production and deployment. Disclosures:No relevant conflicts of interest to declare.

Uncoupling of osteoblast–osteoclast regulation in a chemical murine model of Gaucher disease

Gaucher disease (GD) is caused by mutations in the GBA gene that confer a deficient level of activity of glucocerebrosidase (GCase). This deficiency leads to accumulation of the glycolipid glucocerebroside in the lysosomes of cells of monocyte/macrophage system. Type I GD is the mildest form and is characterized by the absence of neuronopathic affection. Bone compromise in Gaucher disease patients is the most disabling aspect of the disease. However, pathophysiological aspects of skeletal alterations are still poorly understood.The homeostasis of bone tissue is maintained by the balanced processes of bone resorption by osteoclasts and formation by osteoblasts. We decided to test whether bone resorption and/or bone formation could be altered by the use of a chemical in vitro murine model of Gaucher disease.We used two sources of cells from monocyte/macrophages lineage isolated from normal mice, splenocytes (S) and peritoneal macrophages (PM), and were exposed to CBE, the inhibitor of GCase (S-CBE and PM-CBE, respectively). Addition of both conditioned media (CM) from S-CBE and PM-CBE induced the differentiation of osteoclasts precursors from bone marrow to mature and functional osteoclasts. TNF-α could be one of the factors responsible for this effect. On the other hand, addition of CM to an osteoblast cell culture resulted in a reduction in expression of alkaline phosphatase and mineralization process. In conclusion, these results suggest implication of changes in both bone formation and bone resorption and are consistent with the idea that both sides of the homeostatic balance are affected in GD.

Comparative analysis of gingival crevicular fluid neopterin levels in health and periodontal disease: A biochemical study

Periodontitis involves intricate interactions of the biofilm with the host immunoinflammatory response and subsequent alterations in bone and connective tissue homeostasis. Neopterin is a marker, belonging to the class of pteridines, which is associated with cell-mediated immunity. It is produced by interferon-γ stimulated macrophages. The levels of neopterin in body fluids are elevated in infections, autoimmune diseases, malignancies and allograft rejections. This investigation was designed to estimate the levels of neopterin in gingival crevicular fluid (GCF) in health, chronic gingivitis and chronic periodontitis. Thirty subjects were divided into three groups of ten subjects each as with healthy periodontium (Group 1), chronic gingivitis (Group 2) and chronic periodontitis (Group 3). The GCF samples were obtained from the subjects by placing color-coded calibrated, volumetric, micro-capillary pipettes extracrevicularly. The samples were placed in plastic vials and stored at -70°C until the time of neopterin estimation using enzyme immunoassay. The mean neopterin level in Group 3 (126.28 ± 37.70 nmol/L) is significantly higher than the mean neopterin level in Group 1 (48.66 ± 18.82 nmol/L) and Group 2 (70.68 ± 18.26 nmol/L) (P < 0.05). However, there is no significant relationship between neopterin levels and various clinical parameters in each study group (P > 0.05). The results of our study indicate that the neopterin levels in GCF are positively associated with periodontal disease, which may provide a useful tool in monitoring its progression. Nevertheless, further longitudinal studies are required with larger sample sizes in which neopterin levels are progressively estimated and compared to baseline values.

Regulatory role of mesenchymal stem cells in osteoclast differentiation

Mesenchymal stem cells (MSCs) are adult totipotent cells that can differentiate into osteoblasts and chondrocytes. Based on this property, they are theoretically useful for treatment of bone erosive diseases such as rheumatoid arthritis (RA) including joint repair. MSCs constitutively produce a variety of cytokines and growth factors, which explain their immunomodulatory effects on inflammatory cells. Recent clinical trials have shown their efficacy in graft versus host disease. However, whether MSCs can be used for treatment of RA remains unclear. Especially, there is a need to identify and characterize all soluble mediators, i.e., the “trophic effects” ” ” ” of MSCs on the differentiation of osteoclasts, which are involved in bone destruction in RA. We reported previously that human MSCs suppress osteoclast differentiation by constitutive production of osteoprotegerin, the decoy receptor of RANKL. Our results further highlighted the potential usefulness of MSCs for RA treatment by preventing the progression of bone damage by inhibiting osteoclast differentiation. The next step in the clinical application of MSCs includes identifying the best tissue source for these cells and refinement of RA treatment methodology. Recent studies have confirmed that MSCs are important for both bone and synovial tissue homeostasis acting as precursors of osteoblasts and chondrocytes and through their trophic effects. Taken together, MSCs are a hopeful tool to combat joint inflammation and enhance joint repair in RA, ensuring complete cure of this devastating disease.