The direct impact of pegvisomant on osteoblast functions and bone development

PURPOSE

Acromegaly is a chronic disease characterized by growth hormone (GH) hypersecretion, usually caused by a pituitary adenoma, resulting in elevated circulating levels of insulin-like growth factor type I (IGF-I). Pegvisomant (PEG), the GH-receptor (GHR) antagonist, is used in treating acromegaly to normalize IGF-I hypersecretion. Exposure to increased levels of GH and IGF-I can cause profound alterations in bone structure that are not completely reverted by treatment of GH hypersecretion. Indeed, there is evidence that drugs used for the treatment of acromegaly might induce direct effects on skeletal health regardless of biochemical control of acromegaly.

METHODS

We investigated, for the first time, the effect of PEG on cell proliferation, differentiation, and mineralization in the osteoblast cell lines MC3T3-E1 and hFOB 1.19 and its potential impact on bone development in zebrafish larvae.

RESULTS

We observed that PEG did not affect osteoblast proliferation, apoptosis, alkaline phosphatase (ALP) activity, and mineralization. After PEG treatment, the analysis of genes related to osteoblast differentiation showed no difference in Alp, Runx2, or Opg mRNA levels in MC3T3-E1 cells. GH significantly decreased cell apoptosis (- 30 ± 11%, p < 0.001) and increased STAT3 phosphorylation; these effects were suppressed by the addition of PEG in MC3T3-E1 cells. GH and PEG did not affect Igf-I, Igfbp2, and Igfbp4 mRNA levels in MC3T3-E1 cells. Finally, PEG did not affect bone development in zebrafish larvae at 5 days post-fertilization.

CONCLUSION

This study provides a first evidence of the impact of PEG on osteoblast functions both in vitro and in vivo. These findings may have clinically relevant implications for the management of skeletal health in subjects with acromegaly.

Genetic Deficiency of the Long Pentraxin 3 Affects Osteogenesis and Osteoclastogenesis in Homeostatic and Inflammatory Conditions

The long pentraxin 3 (PTX3) is a soluble glycoprotein made by immune and nonimmune cells endowed with pleiotropic functions in innate immunity, inflammation, and tissue remodeling. PTX3 has recently emerged as a mediator of bone turnover in both physiological and pathological conditions, with direct and indirect effects on osteoblasts and osteoclasts. This notwithstanding, its role in bone biology, with major regard to the osteogenic potential of osteoblasts and their interplay with osteoclasts, is at present unclear. Here, we investigated the contribution of this pentraxin to bone deposition in the osteogenic lineage by assessing collagen production, mineralization capacity, osteoblast maturation, extracellular matrix gene expression, and inflammatory mediators' production in primary osteoblasts from the calvaria of wild-type (WT) and Ptx3-deficient (Ptx3-/-) mice. Also, we evaluated the effect of PTX3 on osteoclastogenesis in cocultures of primary osteoblasts and bone marrow-derived osteoclasts. Our investigations were carried out both in physiological and inflammatory conditions to recapitulate in vitro aspects of inflammatory diseases of the bone. We found that primary osteoblasts from WT animals constitutively expressed low levels of the protein in osteogenic noninflammatory conditions, and genetic ablation of PTX3 in these cells had no major impact on collagen and hydroxyapatite deposition. However, Ptx3-/- osteoblasts had an increased RANKL/OPG ratio and CD44 expression, which resulted in in enhanced osteoclastogenesis when cocultured with bone marrow monocytes. Inflammation (modelled through administration of tumor necrosis factor-α, TNF-α) boosted the expression and accumulation of PTX3 and inflammatory mediators in WT osteoblasts. In these conditions, Ptx3 genetic depletion was associated with reduced collagen deposition and immune modulators' production. Our study shed light on the role of PTX3 in osteoblast and osteoclast biology and identified a major effect of inflammation on the bone-related properties of this pentraxin, which might be relevant for therapeutic and/or diagnostic purposes in musculoskeletal pathology.

Label-free multimodal nonlinear optical microscopy reveals features of bone composition in pathophysiological conditions

Bone tissue features a complex microarchitecture and biomolecular composition, which determine biomechanical properties. In addition to state-of-the-art technologies, innovative optical approaches allowing the characterization of the bone in native, label-free conditions can provide new, multi-level insight into this inherently challenging tissue. Here, we exploited multimodal nonlinear optical (NLO) microscopy, including co-registered stimulated Raman scattering, two-photon excited fluorescence, and second-harmonic generation, to image entire vertebrae of murine spine sections. The quantitative nature of these nonlinear interactions allowed us to extract accurate biochemical, morphological, and topological information on the bone tissue and to highlight differences between normal and pathologic samples. Indeed, in a murine model showing bone loss, we observed increased collagen and lipid content as compared to the wild type, along with a decreased craniocaudal alignment of bone collagen fibres. We propose that NLO microscopy can be implemented in standard histopathological analysis of bone in preclinical studies, with the ambitious future perspective to introduce this technique in the clinical practice for the analysis of larger tissue sections.

Direct effects of octreotide on osteoblast cell proliferation and function

PURPOSE

Octreotide (OCT) is a first-generation somatostatin analog (SSA) used in the treatment of acromegaly and neuroendocrine tumors (NETs). In both diseases, OCT interacts with somatostatin receptors 2 and 5 (SSTR2 and SSTR5), inhibiting hormone hypersecretion and cell proliferation. Skeletal health is an important clinical concern in acromegaly and NETs, since acromegalic osteopathy and NET bone metastasis occur in a remarkable number of patients. While OCT's effect on NET and pituitary cells has been extensively investigated, its direct action on bone cells remains unknown.

METHODS

Here, we investigated OCT direct effects on cell proliferation, differentiation, mineralization, and chemoattractant capacity of murine primary osteoblasts and osteoblast cell line MC3T3-E1.

RESULTS

OCT inhibited osteoblasts and MC3T3-E1 cell proliferation (- 30 ± 16%, and - 22 ± 4%, both p < 0.05 vs control) and increased MC3T3-E1 cell apoptosis (+ 76 ± 32%, p < 0.05 vs control). The anti-proliferative action of OCT was mediated by SSTR2 and SSTR5 in MC3T3-E1, while its pro-apoptotic effect was abrogated in SSTR2-silenced cells. The analysis of genes related to the early and late phases of osteoblast differentiation showed that OCT did not affect Alp, Runx2, Bglap, Spp1, and Sost levels in MC3T3-E1 cells. Similarly, OCT did not affect ALP activity, mineralization, and osteoclastogenic induction. Finally, Vegfa expression decreased in OCT-treated MC3T3-E1 cells and OCT inhibited pancreatic NET cell migration toward the osteoblast-conditioned medium.

CONCLUSION

This study provides the first evidence of the direct action of OCT on osteoblasts which may have clinically relevant implications for the management of skeletal health in subjects with acromegaly and metastatic NETs.

3D Cocultures of Osteoblasts and Staphylococcus aureus on Biomimetic Bone Scaffolds as a Tool to Investigate the Host-Pathogen Interface in Osteomyelitis

Osteomyelitis (OM) is an infectious disease of the bone primarily caused by the opportunistic pathogen Staphylococcus aureus (SA). This Gram-positive bacterium has evolved a number of strategies to evade the immune response and subvert bone homeostasis, yet the underlying mechanisms remain poorly understood. OM has been modeled in vitro to challenge pathogenetic hypotheses in controlled conditions, thus providing guidance and support to animal experimentation. In this regard, traditional 2D models of OM inherently lack the spatial complexity of bone architecture. Three-dimensional models of the disease overcome this limitation; however, they poorly reproduce composition and texture of the natural bone. Here, we developed a new 3D model of OM based on cocultures of SA and murine osteoblastic MC3T3-E1 cells on magnesium-doped hydroxyapatite/collagen I (MgHA/Col) scaffolds that closely recapitulate the bone extracellular matrix. In this model, matrix-dependent effects were observed in proliferation, gene transcription, protein expression, and cell–matrix interactions both of the osteoblastic cell line and of bacterium. Additionally, these had distinct metabolic and gene expression profiles, compared to conventional 2D settings, when grown on MgHA/Col scaffolds in separate monocultures. Our study points to MgHA/Col scaffolds as biocompatible and bioactive matrices and provides a novel and close-to-physiology tool to address the pathogenetic mechanisms of OM at the host–pathogen interface.

Altered Bone Status in Rett Syndrome

Rett syndrome (RTT) is a monogenic neurodevelopmental disorder primarily caused by mutations in X-linked MECP2 gene, encoding for methyl-CpG binding protein 2 (MeCP2), a multifaceted modulator of gene expression and chromatin organization. Based on the type of mutation, RTT patients exhibit a broad spectrum of clinical phenotypes with various degrees of severity. In addition, as a complex multisystem disease, RTT shows several clinical manifestations ranging from neurological to non-neurological symptoms. The most common non-neurological comorbidities include, among others, orthopedic complications, mainly scoliosis but also early osteopenia/osteoporosis and a high frequency of fractures. A characteristic low bone mineral density dependent on a slow rate of bone formation due to dysfunctional osteoblast activity rather than an increase in bone resorption is at the root of these complications. Evidence from human and animal studies supports the idea that MECP2 mutation could be associated with altered epigenetic regulation of bone-related factors and signaling pathways, including SFRP4/WNT/β-catenin axis and RANKL/RANK/OPG system. More research is needed to better understand the role of MeCP2 in bone homeostasis. Indeed, uncovering the molecular mechanisms underlying RTT bone problems could reveal new potential pharmacological targets for the treatment of these complications that adversely affect the quality of life of RTT patients for whom the only therapeutic approaches currently available include bisphosphonates, dietary supplements, and physical activity.

Additive effect of combined pollutants to UV induced skin OxInflammation damage. Evaluating the protective topical application of a cosmeceutical mixture formulation

Since the skin is one of the targets of the harmful effects of environmental insults, several studies have investigated the effects of outdoor stressors on cutaneous tissue. Ozone (O3), particulate matter (PM), and ultraviolet radiation (UV) have all been shown to induce skin damage through disruption of tissue redox homeostasis, resulting in the so called "OxInflammation" condition. However, few studies have explored whether these stressors can act synergistically in cutaneous tissues. In the present work, we evaluated whether O3, PM, and UV, which are the most common environmental skin insults, act synergistically in inducing skin damage, and whether this effect could be prevented through topical application of a cosmeceutical formulation mixture (CF Mix) containing 15% vitamin C (l-ascorbic acid), 1% vitamin E (α-tocopherol), and 0.5% ferulic acid. Human skin explants obtained from three different subjects were sequentially exposed to 200 mJ UV light, 0.25 ppm O3 for 2 h, and 30 min of diesel engine exhaust (DEE), alone or in combination for 4 days (time point D1 and D4). We observed a clear additive effect of O3 and DEE in combination with UV in increasing levels of several oxidative (4HNE, HO-1) and inflammatory (COX2, NF-κB) markers and loss of barrier-associated proteins, such as filaggrin and involucrin. Furthermore, daily topical pre-treatment with the CF Mix prevented upregulation of the inflammatory and oxidative markers and the loss of both involucrin and filaggrin. In conclusion, this study is the first to investigate the combined effects of three of the most harmful outdoor stressors on human skin and suggests that daily topical application may prevent pollution-induced skin damage.

Alterations of mitochondrial bioenergetics, dynamics, and morphology support the theory of oxidative damage involvement in autism spectrum disorder

Autism spectrum disorder (ASD) has been hypothesized to be a result of the interplay between genetic predisposition and increased vulnerability to early environmental insults. Mitochondrial dysfunctions appear also involved in ASD pathophysiology, but the mechanisms by which such alterations develop are not completely understood. Here, we analyzed ASD primary fibroblasts by measuring mitochondrial bioenergetics, ultrastructural and dynamic parameters to investigate the hypothesis that defects in these pathways could be interconnected phenomena responsible or consequence for the redox imbalance observed in ASD. High levels of 4-hydroxynonenal protein adducts together with increased NADPH (nicotinamide adenine dinucleotide phosphateoxidase) activity and mitochondrial superoxide production coupled with a compromised antioxidant response guided by a defective Nuclear Factor Erythroid 2-Related Factor 2 pathway confirmed an unbalanced redox homeostasis in ASD. Moreover, ASD fibroblasts showed overactive mitochondrial bioenergetics associated with atypical morphology and altered expression of mitochondrial electron transport chain complexes and dynamics-regulating factors. We suggest that many of the changes observed in mitochondria could represent compensatory mechanisms by which ASD cells try to adapt to altered energy demand, possibly resulting from a chronic oxinflammatory status.

Homogentisic acid affects human osteoblastic functionality by oxidative stress and alteration of the Wnt/β-catenin signaling pathway

Alkaptonuria (AKU) is a rare disease correlated with deficiency of the enzyme homogentisate 1,2 dioxygenase, which causes homogentisic acid (HGA) accumulation. HGA is subjected to oxidation/polymerization reactions, leading to the production of a peculiar melanin-like pigmentation (ochronosis) after chronic inflammation, which is considered as a triggering event for the generation of oxidative stress. Clinical manifestations of AKU are urine darkening, sclera pigmentation, early severe osteoarthropathy, and cardiovascular and renal complication. Despite major clinical manifestations of AKU being observed in the bones and skeleton, the molecular and functional parameters are so far unknown in AKU. In the present study, we used human osteoblasts supplemented with HGA as a AKU cellular model. We observed marked oxidative stress, and for the first time, we were able to correlate HGA deposition with an impairment in the Wnt/β-catenin signaling pathway, opening a range of possible therapeutic strategies for a disease still lacking a known cure.