Activated protein C differentially regulates both viability and differentiation of osteoblasts mediated by bisphosphonates

Deficiency of protein C or protein S as a possible cause of osteoporosis

Proteins C and S are vitamin K-dependent anticoagulative factors that also exert a significant influence on bone quality. Clinical studies have linked the deficiency of proteins C and S to lower bone mineral density and the onset of femoral head osteonecrosis in children. Rare foundational studies analyzing this topic have demonstrated that activated protein C, upon binding to the endothelial protein C receptor expressed on the surface of osteoblasts, promotes osteoblast proliferation. It is also established that proteins C and S play crucial roles in proper collagen synthesis and in maintaining the number of osteoclasts and blood vessels. However, the association between protein C and/or S deficiency and the gradual onset of osteoporosis remains largely uninvestigated. Calculations based on data from peer-reviewed journals suggest that approximately one in every 10 individuals may develop osteoporosis due to congenital protein C or S deficiency. Moreover, when secondary causes of protein C and S deficiency are also considered, the proportion likely further increases. In this paper, we discuss the pathophysiological background of the potential relationship between protein C and S deficiency and the genesis of osteoporosis.

Biased and allosteric modulation of bone cell-expressing G protein-coupled receptors as a novel approach to osteoporosis therapy

On the cellular level, osteoporosis (OP) is a result of imbalanced bone remodeling, in which osteoclastic bone resorption outcompetes osteoblastic bone formation. Currently available OP medications include both antiresorptive and bone-forming drugs. However, their long-term use in OP patients, mainly in postmenopausal women, is accompanied by severe side effects. Notably, the fundamental coupling between bone resorption and formation processes underlies the existence of an undesirable secondary outcome that bone anabolic or anti-resorptive drugs also reduce bone formation. This drawback requires the development of anti-OP drugs capable of selectively stimulating osteoblastogenesis and concomitantly reducing osteoclastogenesis. We propose that the application of small synthetic biased and allosteric modulators of bone cell receptors, which belong to the G-protein coupled receptors (GPCR) family, could be the key to resolving the undesired anti-OP drug selectivity. This approach is based on the capacity of these GPCR modulators, unlike the natural ligands, to trigger signaling pathways that promote beneficial effects on bone remodeling while blocking potentially deleterious effects. Under the settings of OP, an optimal anti-OP drug should provide fine-tuned regulation of downstream effects, for example, intermittent cyclic AMP (cAMP) elevation, preservation of Ca²⁺ balance, stimulation of osteoprotegerin (OPG) and estrogen production, suppression of sclerostin secretion, and/or preserved/enhanced canonical β-catenin/Wnt signaling pathway. As such, selective modulation of GPCRs involved in bone remodeling presents a promising approach in OP treatment. This review focuses on the evidence for the validity of our hypothesis.

Testing active membranes for bone regeneration: A review

OBJECTIVES

Maxillofacial bone defects are the main hindering conditions for traditional dental implant strategies. Guided Bone Regeneration (GBR) is used to handle this situation. The principle of GBR is to use a membrane to prevent the colonization of soft tissue cells of the bone defect and favors the migration of osteogenic linages. Current membranes do not completely fulfill the requirements that an optimal membrane should have, sometimes resulting in non-predictable results. Thus, the need to develop an ideal membrane to perform this duty is clear. Recent developments in bio-manufacturing are driving innovations in membranes technology permitting the active participation of the membrane in the healing and regenerative process trough native tissue mimicking, drug-delivery and cells interaction, away from being a passive barrier. New membranes features need specific evaluation techniques, beyond the International Standard for membrane materials (last reviewed in 2004), being this the rationale for the present review. Nanotechnology application has completely shifted the way of analyzing structural characterization. New progresses on osteoimmmunomodulation have also switched the understanding of cells-membranes interaction.

DATA AND SOURCES

To propose an updated protocol for GBR membranes evaluation, critical reading of the relevant published literature was carried out after a MEDLINE/PubMed database search.

CONCLUSIONS

The main findings are that a potential active membrane should be assessed in its nanostructure, physicochemical and nanomechanical properties, bioactivity and antibacterial, osteoblasts proliferation, differentiation and mineralization. Immunomodulation testing for macrophages recruitment and M2 phenotype promotion in osteoblasts co-culture has to be achieved to completely analyze membranes/tissue interactions.

miR-628-3p regulates osteoblast differentiation by targeting RUNX2: Possible role in atrophic non-union

Atrophic non-union is a serious complication of fractures. The underlying biological mechanisms involved in its pathogenesis are not yet completely understood. MicroRNAs (miRNAs or miRs) are a type of endogenous small non-coding RNA, which participate in various physiological and pathophysiological processes. In this study, differentially expressed miRNAs were screened in patients with atrophic nonunion. In total, 4 miRNAs (miR-149^*, miR-221, miR-628-3p and miR-654-5p) were upregulated and 7 miRNAs (let-7b^*, miR-220b, miR-513a-3p, miR-551a, miR-576-5p, miR-1236 and kshv-miR-K12-6-5p) were downregulated at the fracture sites in patients with atrophic non-union. Among the upregulated miRNAs, miR-628-3p and miR-654-5p expression was found to be persistently decreased during osteoblast differentiation, indicating their possible inhibitory effect on osteogenesis. Gain-of-function experiment demonstrated that miR-628-3p, but not miR-654-5p, attenuated osteoblast differentiation. Further, in silico analysis revealed that runt-related transcription factor 2 (RUNX2), the master transcript factor for osteoblast differentiation, was the target of miR-628-3p, which had two binding site-condense regions in the 3′ untranslated region. The exact binding site of miR-628-3p was further identified with luciferase reporter assay. In addition, the overexpression of miR-628-3p appeared to be associated with the suppression of RUNX2 expression at both the mRNA and protein level, suggesting that miR-628-3p inhibits osteoblast differentiation via RUNX2. On the whole, the findings of this study provide evidence of the upregulation of miR-628-3p in patients with atrophic non-union and that miR-628-3p may exert an inhibitory effect on osteogenesis via the suppression of its target gene, RUNX2. The study provides valuable insight into the pathogenesis of atrophic non-union and suggests new potential therapeutic targets for the treatment of this disorder.

Genomic structure and marker-derived gene networks for growth and meat quality traits of Brazilian Nelore beef cattle

BACKGROUND

Nelore is the major beef cattle breed in Brazil with more than 130 million heads. Genome-wide association studies (GWAS) are often used to associate markers and genomic regions to growth and meat quality traits that can be used to assist selection programs. An alternative methodology to traditional GWAS that involves the construction of gene network interactions, derived from results of several GWAS is the AWM (Association Weight Matrices)/PCIT (Partial Correlation and Information Theory). With the aim of evaluating the genetic architecture of Brazilian Nelore cattle, we used high-density SNP genotyping data (~770,000 SNP) from 780 Nelore animals comprising 34 half-sibling families derived from highly disseminated and unrelated sires from across Brazil. The AWM/PCIT methodology was employed to evaluate the genes that participate in a series of eight phenotypes related to growth and meat quality obtained from this Nelore sample.

RESULTS

Our results indicate a lack of structuring between the individuals studied since principal component analyses were not able to differentiate families by its sires or by its ancestral lineages. The application of the AWM/PCIT methodology revealed a trio of transcription factors (comprising VDR, LHX9 and ZEB1) which in combination connected 66 genes through 359 edges and whose biological functions were inspected, some revealing to participate in biological growth processes in literature searches.

CONCLUSIONS

The diversity of the Nelore sample studied is not high enough to differentiate among families neither by sires nor by using the available ancestral lineage information. The gene networks constructed from the AWM/PCIT methodology were a useful alternative in characterizing genes and gene networks that were allegedly influential in growth and meat quality traits in Nelore cattle.

Euodia sutchuenensis Dode extract stimulates osteoblast differentiation via Wnt/β-catenin pathway activation

The Wnt/β-catenin pathway has a role in osteoblast differentiation and bone formation. We screened 100 plant extracts and identified an extract from Euodia sutchuenensis Dode (ESD) leaf and young branch as an effective activator of the Wnt/β-catenin pathway. ESD extract increased β-catenin levels and β-catenin nuclear accumulation in murine primary osteoblasts. The ESD extract also increased mRNA levels of osteoblast markers, including RUNX2, BMP2 and COL1A1, and enhanced alkaline phosphatase (ALP) activity in murine primary osteoblasts. Both ESD extract-induced β-catenin increment and ALP activation were abolished by β-catenin knockdown, confirming that the Wnt/β-catenin pathway functions in osteoblast differentiation. ESD extract enhanced terminal osteoblast differentiation as shown by staining with Alizarin Red S and significantly increased murine calvarial bone thickness. This study shows that ESD extract stimulates osteoblast differentiation via the Wnt/β-catenin pathway and enhances murine calvarial bone formation ex vivo.

Extracellular Matrix Reorganization During Wound Healing and Its Impact on Abnormal Scarring

Significance: When a cutaneous injury occurs, the wound heals via a dynamic series of physiological events, including coagulation, granulation tissue formation, re-epithelialization, and extracellular matrix (ECM) remodeling. The final stage can take many months, yet the new ECM forms a scar that never achieves the flexibility or strength of the original tissue. In certain circumstances, the normal scar is replaced by pathological fibrotic tissue, which results in hypertrophic or keloid scars. These scars cause significant morbidity through physical dysfunction and psychological stress. Recent Advances and Critical Issues: The cutaneous ECM comprises a complex assortment of proteins that was traditionally thought to simply provide structural integrity and scaffolding characteristics. However, recent findings show that the ECM has multiple functions, including, storage and delivery of growth factors and cytokines, tissue repair and various physiological functions. Abnormal ECM reconstruction during wound healing contributes to the formation of hypertrophic and keloid scars. Whereas adult wounds heal with scarring, the developing foetus has the ability to heal wounds in a scarless fashion by regenerating skin and restoring the normal ECM architecture, strength, and function. Recent studies show that the lack of inflammation in fetal wounds contributes to this perfect healing. Future Directions: Better understanding of the exact roles of ECM components in scarring will allow us to produce therapeutic agents to prevent hypertrophic and keloid scars. This review will focus on the components of the ECM and their role in both physiological and pathological (hypertrophic and keloid) cutaneous scar formation.

Activated protein C (APC) can increase bone anabolism via a protease-activated receptor (PAR)1/2 dependent mechanism

Activated Protein C (APC) is an anticoagulant with strong cytoprotective properties that has been shown to promote wound healing. In this study APC was investigated for its potential orthopedic application using a Bone Morphogenetic Protein 2 (rhBMP-2) induced ectopic bone formation model. Local co-administration of 10 µg rhBMP-2 with 10 µg or 25 µg APC increased bone volume at 3 weeks by 32% (N.S.) and 74% (p<0.01) compared to rhBMP-2 alone. This was associated with a significant increase in CD31+ and TRAP+ cells in tissue sections of ectopic bone, consistent with enhanced vascularity and bone turnover. The actions of APC are largely mediated by its receptors endothelial protein C receptor (EPCR) and protease-activated receptors (PARs). Cultured pre-osteoblasts and bone nodule tissue sections were shown to express PAR1/2 and EPCR. When pre-osteoblasts were treated with APC, cell viability and phosphorylation of ERK1/2, Akt, and p38 were increased. Inhibition with PAR1 and sometimes PAR2 antagonists, but not with EPCR blocking antibodies, ameliorated the effects of APC on cell viability and kinase phosphorylation. These data indicate that APC can affect osteoblast viability and signaling, and may have in vivo applications with rhBMP-2 for bone repair.

Zoledronic acid at subtoxic dose extends osteoblastic stage span of primary human osteoblasts

OBJECTIVE

This study aimed to check the effect of zoledronic acid (ZA) at subtoxic dose on human osteoblasts (HOs) in terms of cell viability, apoptosis occurrence, and differentiation induction. ZA belongs to the family of bisphosphonates (BPs), largely used in the clinical practice for the treatment of bone diseases, often associated with jaw osteonecrosis onset. Their pharmacological action consists in the direct block of the osteoclast-mediated bone resorption along with indirect action on osteoblasts.

MATERIALS AND METHODS

HOs were treated choosing the highest limit concentration (10(-5) M) which does not induce toxic effects. Live/dead staining, flow cytometry, mitochondrial membrane potential assay, osteocalcin western blotting, gp38 RT-PCR, collagen type I, PGE2, and IL-6 ELISA assays were performed.

RESULTS

Similar viability level between control and ZA-treated samples is found along with no significant increase of apoptotic and necrotic cells in ZA-treated sample. To establish if an early apoptotic pathway was triggered, Bax expression and mitochondrial membrane potential were evaluated finding a higher protein expression in control sample and a good integrity of mitochondrial membrane in both experimental points. Type I collagen secretion and alkaline phosphatase (ALP) activity appear increased in ZA-treated sample, osteocalcin expression level is reduced in ZA-treated cells, whereas no modifications of gp38 mRNA level are evidenced. No statistical differences are identified in PGE2 secretion level whereas IL-6 secretion is lower in ZA-treated HOs with respect to control ones.

CONCLUSIONS

These results highlight that ZA, delaying the osteoblastic differentiation process versus the osteocytic lineage, strengthens its pharmacological activity enhancing bone density.

CLINICAL RELEVANCE

The knowledge of ZA effects on osteoblasts at subtoxic dose allows to improve therapeutic protocols in order to strengthen drug pharmacological activity through a combined action on both osteoclastic and osteoblastic cells.