Matricellular proteins: Extracellular modulators of bone development, remodeling, and regeneration

Brain-Bone Crosstalk in a Murine Polytrauma Model Promotes Bone Remodeling but Impairs Neuromotor Recovery and Anxiety-Related Behavior

Traumatic brain injury (TBI) and long bone fractures are a common injury pattern in polytrauma patients and modulate each other's healing process. As only a limited number of studies have investigated both traumatic sites, we tested the hypothesis that brain-bone polytrauma mutually impacts neuro- and osteopathological outcomes. Adult female C57BL/6N mice were subjected to controlled cortical impact (CCI), and/or osteosynthetic stabilized femoral fracture (FF), or sham surgery. Neuromotor and behavioral impairments were assessed by neurological severity score, open field test, rotarod test, and elevated plus maze test. Brain and bone tissues were processed 42 days after trauma. CCI+FF polytrauma mice had increased bone formation as compared to FF mice and increased mRNA expression of bone sialoprotein (BSP). Bone fractures did not aggravate neuropathology or neuroinflammation assessed by cerebral lesion size, hippocampal integrity, astrocyte and microglia activation, and gene expression. Behavioral assessments demonstrated an overall impaired recovery of neuromotor function and persistent abnormalities in anxiety-related behavior in polytrauma mice. This study shows enhanced bone healing, impaired neuromotor recovery and anxiety-like behavior in a brain-bone polytrauma model. However, bone fractures did not aggravate TBI-evoked neuropathology, suggesting the existence of outcome-relevant mechanisms independent of the extent of brain structural damage and neuroinflammation.

Immunomodulatory multicellular scaffolds for tendon-to-bone regeneration

Limited motor activity due to the loss of natural structure impedes recovery in patients suffering from tendon-to-bone injury. Conventional biomaterials focus on strengthening the regenerative ability of tendons/bones to restore natural structure. However, owing to ignoring the immune environment and lack of multi-tissue regenerative function, satisfactory outcomes remain elusive. Here, combined manganese silicate (MS) nanoparticles with tendon/bone-related cells, the immunomodulatory multicellular scaffolds were fabricated for integrated regeneration of tendon-to-bone. Notably, by integrating biomimetic cellular distribution and MS nanoparticles, the multicellular scaffolds exhibited diverse bioactivities. Moreover, MS nanoparticles enhanced the specific differentiation of multicellular scaffolds via regulating macrophages, which was mainly attributed to the secretion of PGE2 in macrophages induced by Mn ions. Furthermore, three animal results indicated that the scaffolds achieved immunomodulation, integrated regeneration, and function recovery at tendon-to-bone interfaces. Thus, the multicellular scaffolds based on inorganic biomaterials offer an innovative concept for immunomodulation and integrated regeneration of soft/hard tissue interfaces.

Advances in the role and mechanism of fibroblasts in fracture healing

With the development of social population ageing, bone fracture has become a global public health problem due to its high morbidity, disability and mortality. Fracture healing is a complex phenomenon involving the coordinated participation of immigration, differentiation and proliferation of inflammatory cells, angioblasts, fibroblasts, chondroblasts and osteoblasts which synthesize and release bioactive substances of extracellular matrix components, Mortality caused by age-related bone fractures or osteoporosis is steadily increasing worldwide as the population ages. Fibroblasts play an important role in the process of fracture healing. However, it is not clear how the growth factors and extracellular matrix stiffness of the bone-regeneration microenvironment affects the function of osteoblasts and fibroblasts in healing process. Therefore, this article focuses on the role of fibroblasts in the process of fracture healing and mechanisms of research progress.

Analysis of Cellular Crosstalk and Molecular Signal between Periosteum-Derived Precursor Cells and Peripheral Cells During Bone Healing Process Using a Paper-Based Osteogenesis-On-A-Chip Platform

Periosteum-derived progenitor cells (PDPCs) are highly promising cell sources that are indispensable in the bone healing process. Adipose-derived stem cells (ADSCs) are physiologically close to periosteum tissue and release multiple growth factors to promote the bone healing process. Co-culturing PDPCs and ADSCs can construct periosteum-bone tissue microenvironments for the study of cellular crosstalk and molecular signal in the bone healing process. In the current work, a paper-based osteogenesis-on-a-chip platform was successfully developed to provide an in vitro three-dimensional coculture model. The platform was a paper substrate sandwiched between PDPC-hydrogel and ADSC-hydrogel suspensions. Cell secretion could be transferred through the paper substrate from one side to another side. Growth factors including BMP2, TGF-β, POSTN, Wnt proteins, PDGFA, and VEGFA were directly analyzed by a paper-based immunoassay. Cellular crosstalk was studied by protein expression on the paper substrate. Moreover, osteogenesis of PDPCs was investigated by examining the mRNA expressions of PDPCs after culture. Neutralizing and competitive assays were conducted to understand the correlation between growth factors secreted from ADSCs and the osteogenesis of PDPCs. In vitro periosteum-bone tissue microenvironment was established by the paper-based osteogenesis-on-a-chip platform. The proposed approach provides a promising assay of cellular crosstalk and molecular signal in 3D coculture microenvironment that may potentially lead to the development of effective bone regeneration therapy.

SPARC accelerates biliary tract cancer progression through CTGF-mediated tumor-stroma interactions: SPARC as a prognostic marker of survival after neoadjuvant therapy

PURPOSE

In biliary tract cancer (BTC), malignancy is strongest at the invasion front. To improve the BTC prognosis, the invasion front should be controlled. We evaluated tumor-stroma crosstalk at the tumor center and at the invasion front of BTC lesions. We investigated the expression of SPARC, a marker of cancer-associated fibroblasts, and determined its ability to predict BTC prognosis after neoadjuvant chemoradiotherapy (NAC-RT).

METHODS

We performed immunohistochemistry to evaluate SPARC expression in resected specimens from patients that underwent BTC surgery. We established highly invasive (HI) clones in two BTC cell lines (NOZ, CCLP1), and performed mRNA microarrays to compare gene expression in parental and HI cells.

RESULTS

Among 92 specimens, stromal SPARC expression was higher at the invasion front than at the lesion center (p = 0.014). Among 50 specimens from patients treated with surgery alone, high stromal SPARC expression at the invasion front was associated with a poor prognosis (recurrence-free survival: p = 0.033; overall survival: p = 0.017). Coculturing fibroblasts with NOZ-HI cells upregulated fibroblast SPARC expression. mRNA microarrays showed that connective tissue growth factor (CTGF) was upregulated in NOZ-HI and CCLP1-HI cells. A CTGF knockdown suppressed cell invasion in NOZ-HI cells. Exogeneous CTGF upregulated SPARC expression in fibroblasts. SPARC expression at the invasion front was significantly lower after NAC-RT, compared to surgery alone (p = 0.003).

CONCLUSION

CTGF was associated with tumor-stroma crosstalk in BTC. CTGF activated stromal SPARC expression, which promoted tumor progression, particularly at the invasion front. SPARC expression at the invasion front after NAC-RT may serve as a prognosis predictor.

Plasma Osteopontin Reflects Tissue Damage in Acute Pancreatitis

Several scoring systems for clinical prediction of the severity of acute pancreatitis (AP) have been proposed. Yet, there is still a need for an easy-to-measure biomarker. Osteopontin (OPN) may be released to the circulation early during tissue injury, but the significance of OPN in AP has not yet been established. We aimed to evaluate plasma levels of OPN in relation to the severity of AP. In 39 individuals with confirmed AP, plasma was collected on the day of admission and consecutively for three days thereafter. Sex- and age-matched healthy blood donors (n = 39) served as controls. Plasma OPN was measured by a commercial enzyme-linked immunosorbent assay. At admission, patients with AP displayed higher OPN, 156.4 ng/mL (IQR 111.8-196.2) compared to controls, 37.4 ng/mL (IQR 11.7-65.7) (p < 0.0001). However, OPN levels on admission could not discriminate between mild and moderate-to-severe disease (132.6 ng/mL vs. 163.4 ng/mL). Nevertheless, the changes in OPN within 24 h of admission and Day 2/3 were higher among patients with moderate/severe AP (33.7%) compared to mild AP (-8.1%) (p = 0.01). This indicates that OPN is a relevant biomarker reflecting tissue injury in AP. The increase in OPN over time suggests that serial OPN measurements could contribute to the early detection of at-risk patients. Prospective studies assessing OPN in relation to outcome in AP are warranted.

Bismuth-coated 80S15C bioactive glass scaffolds for photothermal antitumor therapy and bone regeneration

Background: Malignant bone tumors usually occur in young people and have a high mortality and disability rate. Surgical excision commonly results in residual bone tumor cells and large bone defects, and conventional radiotherapy and chemotherapy may cause significant side effects. In this study, a bifunctional Bi-BG scaffold for near-infrared (NIR)-activated photothermal ablation of bone tumors and enhanced bone defect regeneration is fabricated. Methods: In this study, we prepared the Bi-BG scaffold by in-situ generation of NIR-absorbing Bi coating on the surface of a 3D-printing bioactive glass (BG) scaffold. SEM was used to analyze the morphological changes of the scaffolds. In addition, the temperature variation was imaged and recorded under 808 nm NIR laser irradiation in real time by an infrared thermal imaging system. Then, the proliferation of rat bone mesenchymal stem cells (rBMSCs) and Saos-2 on the scaffolds was examined by CCK-8 assay. ALP activity assay and RT-PCR were performed to test the osteogenic capacity. For in vivo experiments, the nude rat tumor-forming and rat calvarial defect models were established. At 8 weeks after surgery, micro-CT, and histological staining were performed on harvested calvarial samples. Results: The Bi-BG scaffolds have outstanding photothermal performance under the irradiation of 808 nm NIR at different power densities, while no photothermal effects are observed for pure BG scaffolds. The photothermal temperature of the Bi-BG scaffold can be effectively regulated in the range 26-100°C by controlling the NIR power density and irradiation duration. Bi-BG scaffolds not only significantly induces more than 95% of osteosarcoma cell death (Saos-2) in vitro, but also effectively inhibit the growth of bone tumors in vivo. Furthermore, they exhibit excellent capability in promoting osteogenic differentiation of rBMSCs and finally enhance new bone formation in the calvarial defects of rats. Conclusion: The Bi-BG scaffolds have bifunctional properties of photothermal antitumor therapy and bone regeneration, which offers an effective method to ablate malignant bone tumors based on photothermal effect.

The role of Meteorin-like in skeletal development and bone fracture healing

Meteorin-like protein (Metrnl), homologous to the initially identified neurotrophic factor Meteorin, is a secreted, multifunctional protein. Here we used mouse models to investigate Metrnl's role in skeletal development and bone fracture healing. During development Metrnl was expressed in the perichondrium and primary ossification center. In neonates, single cell RNA-seq of diaphyseal bone demonstrated strongest expression of Metrnl transcript by osteoblasts. In vitro, Metrnl was osteoinductive, increasing osteoblast differentiation and mineralization in tissue culture models. In vivo, loss of Metrnl expression resulted in no change in skeletal metrics in utero, at birth, or during postnatal growth. Six-week-old Metrnl-null mice displayed similar body length, body weight, tibial length, femoral length, BV/TV, trabecular number, trabecular thickness, and cortical thickness as littermate controls. In 4-month-old mice, lack of Metrnl expression did not change structural stiffness, ultimate force, or energy to fracture of femora under 3-point-bending. Last, we investigated the role of Metrnl in bone fracture healing. Metrnl expression increased in response to tibial injury, however, loss of Metrnl expression did not affect the amount of bone deposited within the healing tissue nor did it change the structural parameters of healing tissue. This work identifies Metrnl as a dispensable molecule for skeletal development. However, the osteoinductive capabilities of Metrnl may be utilized to modulate osteoblast differentiation in cell-based orthopedic therapies.

Advances in bone turnover markers

Bone fragility fractures remain an important worldwide health and economic problem due to increased morbidity and mortality. The current methods for predicting fractures are largely based on the measurement of bone mineral density and the utilization of mathematical risk calculators based on clinical risk factors for bone fragility. Despite these approaches, many bone fractures remain undiagnosed. Therefore, current research is focused on the identification of new factors such as bone turnover markers (BTM) for risk calculation. BTM are a group of proteins and peptides released during bone remodeling that can be found in serum or urine. They derive from bone resorptive and formative processes mediated by osteoclasts and osteoblasts, respectively. Potential use of BTM in monitoring these phenomenon and therefore bone fracture risk is limited by physiologic and pathophysiologic factors that influence BTM. These limitations in predicting fractures explain why their inclusion in clinical guidelines remains limited despite the large number of studies examining BTM.

AT1 and AT2 Receptor Knockout Changed Osteonectin and Bone Density in Mice in Periodontal Inflammation Experimental Model

BACKGROUND

The aim of this study was to evaluate the role of AT1 and AT2 receptors in a periodontal inflammation experimental model.

METHODS

Periodontal inflammation was induced by LPS/Porphyromonas gingivalis. Maxillae, femur, and vertebra were scanned using Micro-CT. Maxillae were analyzed histopathologically, immunohistochemically, and by RT-PCR.

RESULTS

The vertebra showed decreased BMD in AT1 H compared with WT H (p < 0.05). The femur showed increased Tb.Sp for AT1 H and AT2 H, p < 0.01 and p < 0.05, respectively. The Tb.N was decreased in the vertebra (WT H-AT1 H: p < 0.05; WT H-AT2 H: p < 0.05) and in the femur (WT H-AT1 H: p < 0.01; WT H-AT2 H: p < 0.05). AT1 PD increased linear bone loss (p < 0.05) and decreased osteoblast cells (p < 0.05). RANKL immunostaining was intense for AT1 PD and WT PD (p < 0.001). OPG was intense in the WT H, WT PD, and AT2 PD when compared to AT1 PD (p < 0.001). AT1 PD showed weak immunostaining for osteocalcin compared with WT H, WT PD, and AT2 PD (p < 0.001). AT1 H showed significantly stronger immunostaining for osteonectin in fibroblasts compared to AT2 H (p < 0.01).

CONCLUSION

AT1 receptor knockout changed bone density, the quality and number of bone trabeculae, decreased the number of osteoblast cells, and increased osteonectin in fibroblasts.

Regeneration enhanced in critical-sized bone defects using bone-specific extracellular matrix protein

Extracellular matrix (ECM) products have the potential to improve cellular attachment and promote tissue-specific development by mimicking the native cellular niche. In this study, the therapeutic efficacy of an ECM substratum produced by bone marrow stem cells (BM-MSCs) to promote bone regeneration in vitro and in vivo were evaluated. Fluorescence-activated cell sorting analysis and phenotypic expression were employed to characterize the in vitro BM-MSC response to bone marrow specific ECM (BM-ECM). BM-ECM encouraged cell proliferation and stemness maintenance. The efficacy of BM-ECM as an adjuvant in promoting bone regeneration was evaluated in an orthotopic, segmental critical-sized bone defect in the rat femur over 8 weeks. The groups evaluated were either untreated (negative control); packed with calcium phosphate granules or granules+BM-ECM free protein and stabilized by collagenous membrane. Bone regeneration in vivo was analyzed using microcomputed tomography and histology. in vivo results demonstrated improvements in mineralization, osteogenesis, and tissue infiltration (114 ± 15% increase) in the BM-ECM complex group from 4 to 8 weeks compared to mineral granules only (45 ± 21% increase). Histological observations suggested direct apposition of early bone after 4 weeks and mineral consolidation after 8 weeks implantation for the group supplemented with BM-ECM. Significant osteoid formation and greater functional bone formation (polar moment of inertia was 71 ± 0.2 mm4 with BM-ECM supplementation compared to 48 ± 0.2 mm4 in untreated defects) validated in vivo indicated support of osteoconductivity and increased defect site cellularity. In conclusion, these results suggest that BM-ECM free protein is potentially a therapeutic supplement for stemness maintenance and sustaining osteogenesis.

Schwann cell plasticity regulates neuroblastic tumor cell differentiation via epidermal growth factor-like protein 8

Adult Schwann cells (SCs) possess an inherent plastic potential. This plasticity allows SCs to acquire repair-specific functions essential for peripheral nerve regeneration. Here, we investigate whether stromal SCs in benign-behaving peripheral neuroblastic tumors adopt a similar cellular state. We profile ganglioneuromas and neuroblastomas, rich and poor in SC stroma, respectively, and peripheral nerves after injury, rich in repair SCs. Indeed, stromal SCs in ganglioneuromas and repair SCs share the expression of nerve repair-associated genes. Neuroblastoma cells, derived from aggressive tumors, respond to primary repair-related SCs and their secretome with increased neuronal differentiation and reduced proliferation. Within the pool of secreted stromal and repair SC factors, we identify EGFL8, a matricellular protein with so far undescribed function, to act as neuritogen and to rewire cellular signaling by activating kinases involved in neurogenesis. In summary, we report that human SCs undergo a similar adaptive response in two patho-physiologically distinct situations, peripheral nerve injury and tumor development.

Genome-Wide Differentially Methylated Region Analysis to Reveal Epigenetic Differences of Articular Cartilage in Kashin-Beck Disease and Osteoarthritis

Kashin-Beck disease (KBD) is a degenerative osteoarticular disorder, and displays the significant differences with osteoarthritis (OA) regarding the etiology and molecular changes in articular cartilage. However, the underlying dysfunctions of molecular mechanisms in KBD and OA remain unclear. Here, we primarily performed the various genome-wide differential methylation analyses to reveal the distinct differentially methylated regions (DMRs) in conjunction with corresponding differentially methylated genes (DMGs), and enriched functional pathways in KBD and OA. We identified a total of 131 DMRs in KBD vs. Control, and 58 DMRs in OA vs. Controls, and the results demonstrate that many interesting DMRs are linked to DMGs, such as SMOC2 and HOXD3, which are all key genes to regulate cartilage/skeletal physiologic and pathologic process, and are further enriched in skeletal system and limb-associated pathways. Our DMR analysis indicates that KBD-associated DMRs has higher proportion than OA-associated DMRs in gene body regions. KBD-associated DMGs were enriched in wounding and coagulation-related functional pathways that may be stimulated by trace elements. The identified molecular features provide novel clues for understanding the pathogenetic and therapeutic studies of both KBD and OA.

Gene expression, immunohistochemical and microarchitectural evaluation of bone formation around two implant surfaces placed in bone defects filled or not with bone substitute material

Objective

The aim of this study is to evaluate through gene expression, immunohistochemical and microtomographic (micro-CT) analysis the response of peri-implant bone tissue around titanium implants with different surface treatments, placed in bone defects filled or not with bone substitute materials. In addition, to investigate the hypothesis that porous-hydrophilic surface induces a faster bone formation.

Materials and methods

Twenty-six animals were divided into two groups according to implant surface treatment. In each tibia, a bone defect was created followed by the placement of one implant. On the left tibia, the defect was filled with blood clot (BC), and on the right tibia, the defect was filled with biphasic hydroxyapatite/β-tricalcium-phosphate (HA/TCP) generating four subgroups: BC-N: bone defect filled with blood clot and porous surface titanium implant installed; BC-A: bone defect filled with blood clot and porous-hydrophilic surface titanium implant installed; HA/TCP-N: bone defect filled with bone substitute material and porous surface titanium implant installed; and HA/TCP-A: bone defect filled with bone substitute material and porous-hydrophilic surface titanium implant installed. The animals were submitted to euthanasia at 15, 30, and 60 days after implant installation. The expression of two genes was evaluated: RUNX2 and BSP. Immunohistochemical analyses were performed for detection of RUNX2, OPN, OCN, OPG, and RANKL antibodies and bone matrix proteins. Finally, four parameters were chosen for micro-CT analysis: trabecular number, separation and thickness, and connectivity density.

Results

Descriptive analysis showed similar findings among the experimental groups. Moreover, porous-hydrophilic surfaces presented a higher expression of RUNX2, which is probably an indicative of better osteogenesis; although the data from this study may be considered an insufficient support for a concrete statement.

Conclusion

Porous hydrophilic surface can improve and accelerate protein expression and bone formation.

Genetic and epigenetic regulation of osteopontin by cyclic adenosine 3' 5'-monophosphate in osteoblasts

Osteopontin (OPN) is not only a marker of osteoblasts but it is also related to cancer progression and inflammation. The expression of OPN increases in response to inflammatory cytokines, hormones, and mechanical stress. Among them, cyclic-AMP (cAMP) elevating agents stimulate OPN expression in the presence of 1, 25-OH vitamin D₃ (VD₃). We aimed to clarify the mechanism by which cAMP enhances OPN expression in osteoblastic cells. The OPN promoter (-2335 to +76, OPNp2335) exerted a cell type specific response to forskolin (FK) and VD₃. Sequential deletion analysis of OPNp revealed that the OPNp (-833 to +76) contained essential responsive regions to respond to cAMP signaling. In particular, both Vitamin D response element (VDRE, -758 to -743) and osteoblast-specific cis- acting element 2 (OSE2, -695 to -690) were essential for cAMP-mediated OPNp activity. The expression of vitamin D receptor (VDR), but not runt-related transcription factor 2 (Runx2), a nuclear receptor for OSE2, was induced by the treatment of the cells with FK. Although, VD₃-induced OPNp activity was slightly enhanced in VDR-overexpressing osteoblasts, it reached the same level as that of osteoblasts induced by both VD₃ and FK in the presence of histone deacetylase (HDAC) inhibitor. Moreover, we identified histone acetylation on the OPN promoter region by FK treatment. These results strongly suggest that OPNp activity is controlled by the cAMP signaling via genetic and epigenetic regulations.

Biomimetic mineralizable collagen hydrogels for dynamic bone matrix formation to promote osteogenesis

The simulation of the native bone matrix formation process is crucial for the construction of the cellular microenvironment for bone regeneration. However, it is still challenging to design bioactive materials that simultaneously mimic the composition and dynamic mineralization process of the bone matrix, let alone realize osteoinduction by a biomimetic dynamic microenvironment. In this study, we prepared a biomimetic mineralizable collagen hydrogel (CAV) and explored the effects of a dynamic mineralized matrix on the osteogenesis of stem cells both in vitro and in vivo. We showed the feasibility of the biomimetic CAV hydrogel to induce mineralization in simulated media including simulated body fluid (SBF), glycerol phosphate calcium salt hydrate (CaGP) solution and cell co-cultured systems. The participation of cells in the mineralization process is more likely to induce matrix remodeling due to the synergistic effects of CAV mineralization and cellular secretion, resulting in higher matrix strength. We also demonstrated that the biomimetic mineralized hydrogel could up-regulate osteogenic genes and protein expression of bone marrow mesenchymal stem cells (BMSCs), thus enhancing osteogenesis in vivo. The interactions between the mineralizable hydrogel and cells play an important role in regulating dynamic matrix mineralization and osteogenesis. Our findings prove that the biomimetic mineralizable hydrogel is a promising candidate for implantable orthopedic applications and provides essential implications for the future design of materials for bone regeneration.

p53's Extended Reach: The Mutant p53 Secretome

p53 suppresses tumorigenesis by activating a plethora of effector pathways. While most of these operate primarily inside of cells to limit proliferation and survival of incipient cancer cells, many extend to the extracellular space. In particular, p53 controls expression and secretion of numerous extracellular factors that are either soluble or contained within extracellular vesicles such as exosomes. As part of the cellular secretome, they execute key roles in cell-cell communication and extracellular matrix remodeling. Mutations in the p53-encoding TP53 gene are the most frequent genetic alterations in cancer cells, and therefore, have profound impact on the composition of the tumor cell secretome. In this review, we discuss how the loss or dominant-negative inhibition of wild-type p53 in concert with a gain of neomorphic properties observed for many mutant p53 proteins, shapes a tumor cell secretome that creates a supportive microenvironment at the primary tumor site and primes niches in distant organs for future metastatic colonization.

Modulation of bone turnover aberration: A target for management of primary osteoporosis in experimental rat model

Osteoporosis is a skeletal degenerative disease characterised by abnormal bone turnover with scant bone formation and overabundant bone resorption. The present approach was intended to address the potency of nanohydroxyapatite (nHA), chitosan/hydroxyapatite nanocomposites (nCh/HA) and silver/hydroxyapatite nanoparticles (nAg/HA) to modulate bone turnover deviation in primary osteoporosis induced in the experimental model. Characterisation techniques such as TEM, zeta-potential, FT-IR and XRD were used to assess the morphology, the physical as well as the chemical features of the prepared nanostructures. The in vivo experiment was conducted on forty-eight adult female rats, randomised into 6 groups (8 rats/group), (1) gonad-intact, (2) osteoporotic group, (3) osteoporotic + nHA, (4) osteoporotic + nCh/HA, (5) osteoporotic + nAg/HA and (6) osteoporotic + alendronate (ALN). After three months of treatment, serum sclerostin (SOST), bone alkaline phosphatase (BALP) and bone sialoprotein (BSP) levels were quantified using ELISA. Femur bone receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) and cathepsin K (CtsK) mRNA levels were evaluated by quantitative RT-PCR. Moreover, alizarin red S staining was applied to determine the mineralisation intensity of femur bone. Findings in the present study indicated that treatment with nHA, nCh/HA or nAg/HA leads to significant repression of serum SOST, BALP and BSP levels parallel to a significant down-regulation of RANKL and CtsK gene expression levels. On the other side, significant enhancement in the calcification intensity of femur bone has been noticed. The outcomes of this experimental setting ascertained the potentiality of nHA, nCh/HA and nAg/HA as promising nanomaterials in attenuating the excessive bone turnover in the primary osteoporotic rat model. The mechanisms behind the efficacy of the investigated nanostructures involved the obstacle of serum and tissue indices of bone resorption besides the strengthening of bone mineralisation.

Accelerated evolution and diversifying selection drove the adaptation of cetacean bone microstructure

BACKGROUND

The transition from land to sea by the ancestor of cetaceans approximately 50 million years ago was an incredible evolutionary event that led to a series of morphological, physiological, and behavioral adaptations. During this transition, bone microstructure evolved from the typical terrestrial form to the specialized structure found in modern cetaceans. While the bone microstructure of mammals has been documented before, investigations of its genetic basis lag behind. The increasing number of cetaceans with whole-genome sequences available may shed light on the mechanism underlying bone microstructure evolution as a result of land to water transitions.

RESULTS

Cetacean bone microstructure is consistent with their diverse ecological behaviors. Molecular evolution was assessed by correlating bone microstructure and gene substitution rates in terrestrial and aquatic species, and by detecting genes under positive selection along ancestral branches of cetaceans. We found that: 1) Genes involved in osteoclast function are under accelerated evolution in cetaceans, suggestive of important roles in bone remodeling during the adaptation to an aquatic environment; 2) Genes in the Wnt pathway critical for bone development and homeostasis show evidence of divergent evolution in cetaceans; 3) Several genes encoding bone collagens are under selective pressure in cetaceans.

CONCLUSIONS

Our results suggest that evolutionary pressures have shaped the bone microstructure of cetaceans, to facilitate life in diverse aquatic environments.

How many aqueous humor outflow pathways are there?

The aqueous humor (AH) outflow pathways definition is still matter of intense debate. To date, the differentiation between conventional (trabecular meshwork) and unconventional (uveoscleral) pathways is widely accepted, distinguishing the different impact of the intraocular pressure on the AH outflow rate. Although the conventional route is recognized to host the main sites for intraocular pressure regulation, the unconventional pathway, with its great potential for AH resorption, seems to act as a sort of relief valve, especially when the trabecular resistance rises. Recent evidence demonstrates the presence of lymphatic channels in the eye and proposes that they may participate in the overall AH drainage and intraocular pressure regulation, in a presumably adaptive fashion. For this reason, the uveolymphatic route is increasingly thought to play an important role in the ocular hydrodynamic system physiology. As a result of the unconventional pathway characteristics, hydrodynamic disorders do not develop until the adaptive routes cannot successfully counterbalance the increased AH outflow resistance. When their adaptive mechanisms fail, glaucoma occurs. Our review deals with the standard and newly discovered AH outflow routes, with particular attention to the importance they may have in opening new therapeutic strategies in the treatment of ocular hypertension and glaucoma.

S, Hegde A, ES SP, Johnson RP, Das SP, Vazirally S, Rekha PD. Effect of calcium glucoheptonate on proliferation and osteogenesis of osteoblast-like cells in vitro

Calcium is the key macromineral having a role in skeletal structure and function, muscle contraction, and neurotransmission. Bone remodeling is maintained through a constant balance between calcium resorption and deposition. Calcium deficiency is resolved through calcium supplementation, and among the supplements, water-soluble organic molecules attracted great pharmaceutical interest. Calcium glucoheptonate is a highly water-soluble organic calcium salt having clinical use; however, detailed investigations on its biological effects are limited. We assessed the effects of calcium glucoheptonate on cell viability and proliferation of osteoblast-like MG-63 cells. Calcium uptake and mineralization were evaluated using Alizarin red staining of osteoblast-like MG-63 cells treated with calcium glucoheptonate. Expression of osteogenic markers were monitored by western blotting, immunofluorescence, and qRT-PCR assays. Increased proliferation and calcium uptake were observed in the MG-63 cells treated with calcium glucoheptonate. The treatment also increased the expression of osteopontin and osteogenic genes such as collagen-1, secreted protein acidic and cysteine rich (SPARC), and osteocalcin. Calcium glucoheptonate treatment did not exert any cytotoxicity on colorectal and renal epithelial cells, indicating the safety of the treatment. This is the first report with evidence for its beneficial effect for pharmaceutical use in addressing calcium deficiency conditions.

TSP1 and TSP2 deficiencies affect LOX protein distribution in the femoral diaphysis and pro-peptide removal in marrow-derived mesenchymal stem cells in vitro

Thrombospondin-1 and 2 have each been implicated in collagen fibrillogenesis. We addressed the possibility that deficits in lysyl oxidase (LOX) contribute to the extracellular matrix (ECM) phenotype of TSP-deficient bone. We examined detergent insoluble (mature cross-linked) and soluble (newly secreted) ECM fractions prepared from diaphyseal cortical bone. Detergent-insoluble hydroxyproline content, an indicator of cross-linked collagen content and LOX function, was reduced in female TSP-deficient bones. In male diaphyses, only TSP2 deficiency affected insoluble hydroxyproline content. Western blot suggested that removal of the LOX-pro-peptide (LOPP), an indication of LOX activation, was not affected by TSP status. Instead, the distribution of pro-LOX and mature LOX between immature and mature ECM was altered by TSP-status. LOX was also examined in primary marrow-derived mesenchymal stem cells (MSC) treated with ascorbate. Relative LOPP levels were elevated compared to WT in MSC conditioned medium from female TSP-deficient mice. When cells were serum starved to limit LOX pro-peptide removal, pro-LOX levels were elevated in TSP2-/- cells compared to wild-type. This phenotype was associated with a transient increase in BMP1 levels in TSP2-/- conditioned medium. TSP2 was detected in bone tissue and osteoblast cell culture. TSP1 was only detected in insoluble ECM prepared from WT diaphyseal bone samples. Our data suggest that the trimeric thrombospondins contribute to bone matrix quality by regulating the distribution of pro and mature LOX between newly secreted, immature ECM and mature, cross-linked ECM.

Outer-inner dual reinforced micro/nano hierarchical scaffolds for promoting osteogenesis

Biomimetic scaffolds have been extensively studied for guiding osteogenesis through structural cues. Inspired by the natural bone growth process, we have employed a hierarchical outer-inner dual reinforcing strategy, which relies on the interfacial ionic bond interaction between amine/calcium and carboxyl groups, to build a nanofiber/particle dual strengthened hierarchical silk fibroin scaffold. This scaffold can provide an applicable form of osteogenic structural cue and mimic the natural bone forming process. Owing to the active interaction between compositions located in the outer pore space and the inner pore wall, the scaffold has over 4 times improvement in the mechanical properties, followed by a significant alteration of the cell-scaffold interaction pattern, demonstrated by over 2 times elevation in the spreading area and enhanced osteogenic activity potentially involving the activities of integrin, vinculin and Yes-associated protein (YAP). The in vivo performance of the scaffold identified the inherent osteogenic effect of the structural cue, which promotes rapid and uniform regeneration. Overall, the hierarchical scaffold is promising in promoting uniform bone regeneration through its specific structural cue endowed by its micro-nano construction.

ZnO nanoparticles inhibit the activity of Porphyromonas gingivalis and Actinomyces naeslundii and promote the mineralization of the cementum

Background

Zinc oxide nanoparticles (ZnONPs) have been widely studied as bactericidal reagents. However, it is still challenging to use ZnONPs as a root canal sealant to eliminate infecting microorganisms in the root canal system. This study aimed at understanding the antibacterial and biofilm effects of ZnONPs in the infected root canal and their effect on cell function.

Methods

This study aimed to develop a better understanding of the antibacterial effects of ZnONPs in the infected root canal and their effect on cell function. Experiments were performed in two stages; the first stage included inhibition zone tests and the minimum inhibitory concentration (MIC) test, which were performed to examine the antibacterial activity of ZnONPs against Porphyromonas gingivalis (P. gingivalis) and Actinomyces Naeslundii (A. naeslundii) bacteria in vitro. ZnONPs were further evaluated for their biocompatibility using normal mouse NIH3T3 and OCCM-30 cells by the cell-based MTT assay. In addition, the influence of ZnONPs on matrix metalloproteinases in NIH3T3 cells and their inhibiting factors (Mmp13 and Timp1) were measured using the real-time PCR technique and western blot method.

Results

The MIC of ZnONPs against P. gingivalis and A. naeslundii were confirmed to be 10 μg/mL and 40 μg/mL, respectively. The MTT assay showed that ZnONPs were nontoxic. The RT-PCR and western blotting results showed that Mmp13 was downregulated and Timp1 expression was increased. Meanwhile, ZnONPs were shown to increase the expression of the OCCM-30 osteogenesis-related factors Bsp and Runx2. Finally, there was no significant change in the morphology of NIH3T3 and OCCM-30 cells after the addition of different concentrations of ZnONPs for different periods of time.

Conclusion

ZnONPs have excellent antibacterial activity against P. gingivalis and A. naeslundii and have low cell cytotoxicity in vitro.

Human mesenchymal stromal cells in adhesion to cell-derived extracellular matrix and titanium: Comparative kinome profile analysis

The extracellular matrix (ECM) physically supports cells and influences stem cell behaviour, modulating kinase-mediated signalling cascades. Cell-derived ECMs have emerged in bone regeneration as they reproduce physiological tissue-architecture and ameliorate mesenchymal stromal cell (MSC) properties. Titanium scaffolds show good mechanical properties, facilitate cell adhesion, and have been routinely used for bone tissue engineering (BTE). We analyzed the kinomic signature of human MSCs in adhesion to an osteopromotive osteoblast-derived ECM, and compared it to MSCs on titanium. PamChip kinase-array analysis revealed 63 phosphorylated peptides on ECM and 59 on titanium, with MSCs on ECM exhibiting significantly higher kinase activity than on titanium. MSCs on the two substrates showed overlapping kinome profiles, with activation of similar signalling pathways (FAK, ERK, and PI3K signalling). Inhibition of PI3K signalling in cells significantly reduced adhesion to ECM and increased the number of nonadherent cells on both substrates. In summary, this study comprehensively characterized the kinase activity in MSCs on cell-derived ECM and titanium, highlighting the role of PI3K signalling in kinomic changes regulating osteoblast viability and adhesion. Kinome profile analysis represents a powerful tool to select pathways to better understand cell behaviour. Osteoblast-derived ECM could be further investigated as titanium scaffold-coating to improve BTE.

Mineralization in micropores of calcium phosphate scaffolds

With the increasing demand for novel bone repair solutions that overcome the drawbacks of current grafting techniques, the design of artificial bone scaffolds is a central focus in bone regeneration research. Calcium phosphate scaffolds are interesting given their compositional similarity with bone mineral. The majority of studies focus on bone growth in the macropores (>100 µm) of implanted calcium phosphate scaffolds where bone structures such as osteons and trabeculae can form. However, a growing body of research shows that micropores (<50 µm) play an important role not only in improving bone growth in the macropores, but also in providing additional space for bone growth. Bone growth in the micropores of calcium phosphate scaffolds offers major mechanical advantages as it improves the mechanical properties of the otherwise brittle materials, further stabilizes the implant, improves load transfer, and generally enhances osteointegration. In this paper, we review evidence in the literature of bone growth into micropores, emphasizing on identification techniques and conditions under which bone components are observed in the micropores. We also review theories on mineralization and propose mechanisms, mediated by cells or not, by which mineralization may occur in the confined micropore space of calcium phosphate scaffolds. Understanding and validating these mechanisms will allow to better control and enhance mineralization in micropores to improve the design and efficiency of bone implants. STATEMENT OF SIGNIFICANCE: The design of synthetic bone scaffolds remains a major focus for engineering solutions to repair damaged and diseased bone. Most studies focus on the design of and growth in macropores (>100 µm), however research increasingly shows the importance of microporosity (<50 µm). Micropores provide an additional space for bone growth, which provides multiple mechanical advantages to the scaffold/bone composite. Here, we review evidence of bone growth into micropores in calcium phosphate scaffolds and conditions under which growth occurs in micropores, and we propose mechanisms that enable or facilitate growth in these pores. Understanding these mechanisms will allow researchers to exploit them and improve the design and efficiency of bone implants.

Periostin in Bone Regeneration

Bone regeneration is an efficient regenerative process depending on the recruitment and activation of skeletal stem cells that allow cartilage and bone formation leading to fracture consolidation. Periosteum, the tissue located at the outer surface of bone is now recognized as an essential player in the bone repair process and contains skeletal stem cells with high regenerative potential. The matrix composition of the periosteum defines its roles in bone growth, in cortical bone modeling and remodeling in response to mechanical strain, and in bone repair. Periostin is a key extracellular matrix component of the periosteum involved in periosteum functions. In this chapter, we summarize the current knowledge on the bone regeneration process, the role of the periosteum and skeletal stem cells, and Periostin functions in this context. The matricellular protein Periostin has several roles through all stages of bone repair: in the early days of repair during the initial activation of stem cells within periosteum, in the active phase of cartilage and bone deposition in the facture callus, and in the final phase of bone bridging and reconstitution of the stem cell pool within periosteum.

Bone physiology as inspiration for tissue regenerative therapies

The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.

Effects of nicotine on the metabolism and gene expression profile of Sprague‑Dawley rat primary osteoblasts

Smoking is a risk factor associated with bone and oral diseases, particularly periodontitis. Nicotine, the major toxic component of tobacco, is able to affect the quality and quantity of bone. Osteoblasts serve an important role in bone formation. Thus far, the effects of nicotine on metabolism‑associated gene and protein expression in osteoblasts have been controversial and the mechanisms remain unclear. The present study assessed alterations in osteogenic activity by performing a Cell Counting kit‑8 assay to investigate proliferation, Annexin V‑fluorescein isothiocyanate/propidium iodide staining to investigate apoptosis, alizarin red staining to investigate the formation of mineralized nodules, reverse transcription‑quantitative polymerase chain reaction and western blotting to investigate the mRNA and protein levels of collagen I, alkaline phosphatase, bone osteocalcin, bone sialoprotein and osteopontin; and mRNA microarray expression analysis, Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analysis to investigate the whole genome expression profile of Sprague‑Dawley (SD) rat primary osteoblasts following treatment with different concentrations of nicotine. The results demonstrated that nicotine inhibited proliferation, promoted early apoptosis and inhibited mineralized nodule formation in a dose‑dependent manner by regulating alkaline phosphatase activity and the expression of osteoblast metabolism‑associated genes and proteins. According to microarray analysis, several genes associated with bone metabolism and genes in the Hedgehog and Notch signaling pathways were downregulated significantly in nicotine‑treated osteoblasts. The results of the present study indicated that nicotine may serve an inhibitory, dose‑dependent role in SD rat primary osteoblasts that may be caused by the perturbation of genes and signaling pathways associated with bone formation. These results may provide a theoretical basis for future research regarding bone metabolism and targeted treatment of oral diseases associated with smoking.

Tailored biomimetic hydrogel based on a photopolymerised DMP1/MCF/gelatin hybrid system for calvarial bone regeneration

Searching for effective osteoinduction factors with higher specificity and biosafety for the preparation of biomimetic materials, which mimic the natural bone extracellular matrix (ECM), seems to be an optimum strategy for achieving ideal bone regeneration.

Cardiac biomarkers in diabetes mellitus: New dawn for risk stratification?

Type 2 diabetes mellitus (T2DM) remains a leading cause of cardiovascular (CV) events and diseases worldwide. The aim of the review is to summarize our knowledge regarding clinical implementation of the biomarker-based strategy of the CV risk assessment in T2DM patient population. There is large body of evidence regarding use of the cardiac biomarkers to risk stratification at higher CV risk individuals who belongs to general population and cohort with established CV disease. Although T2DM patients have higher incidence of macrovascular and microvascular CV complications than the general population, whether cardiac biomarkers would be effective to risk stratification of the T2DM is not fully understood. The role of natriuretic peptides, galectin-3, interleukins, growth differentiation factor-15, as well as biomarkers of endothelial dysfunction are widely discussed. In conclusion, future directions, which associate with discovering of novel biomarkers and their best combinations to provide additional predictive information beyond other traditional CV risk factors, are discussed.

Evaluation of periostin and factors associated with new bone formation in ankylosing spondylitis: Periostin may be associated with the Wnt pathway

OBJECTIVE

Periostin has been shown to be involved in bone anabolism through the regulation of Wnt-β-catenin signaling. It may be one of the pathogenic mechanisms in syndesmophyte formation in ankylosing spondylitis (AS). The aim of this study was to evaluate serum periostin levels in patients with AS and to assess relationships among biomarkers of bone formation and periostin in disease outcomes, particularly radiographic changes.

METHODS

Ninety-seven consecutive AS patients (78% male) and 48 healthy controls (75% male) were included in the study. Serum periostin, dickkopf-1 (DKK-1), sclerostin and vascular endothelial growth factor (VEGF) levels were measured using commercially available enzyme-linked immunosorbent assay kits. Disease-related characteristics of patients were assessed using Ankylosing spondylitis disease activity score - C-reactive protein (ASDAS-CRP), Bath AS Disease Activity Index, Bath AS Functional Index and Bath AS metrology index. Radiographs were scored using the modified New York criteria and modified Stokes AS spinal score (mSASSS).

RESULTS

Compared with control subjects, patients with AS had significantly lower serum levels of periostin (P < 0.001) and sclerostin (P < 0.001), but higher serum levels of VEGF (P < 0.001) and high-sensitivity CRP (P < 0.001). Serum periostin (P = 0.005) and sclerostin levels (P = 0.016) were significantly lower in patients with very high disease activity according to ASDAS-CRP. Current age (P = 0.009), age at symptom onset (P = 0.021) and hip joint involvement (P = 0.012) were independently associated with the development of syndesmophyte, in contrast to biomarkers of bone metabolism that we evaluated.

CONCLUSION

Our results suggest that periostin is down-regulated in AS patients with highly active disease and may contribute to disease pathogenesis through an interaction with Wnt signaling.

The Effect of Reduced Graphene Oxide-Coated Biphasic Calcium Phosphate Bone Graft Material on Osteogenesis

This study was conducted to evaluate the effect of biphasic calcium phosphate (BCP) coated with reduced graphene oxide (rGO) as bone graft materials on bone regeneration. The rGO-coated BCP bone graft material was fabricatied by mixing rGO and BCP at various concentrations. The surface charge of rGO-coated BCP was measured to be -14.43 mV, which formed a static electrostatic interaction. Cell viabilities were significantly diminished at higher concentrations of ≥100 μg/mL. The calvarial defects of 48 rats were implanted rGO-coated BCPs at a weight ratio of 2:1000 (rGO2), 4:1000 (rGO4), and 10:1000 (rGO10), repectively. BCP was used as a control group. The micro-CT and histological analysis were performed to evaluate new bone formation at 2 and 8 weeks after surgery. The results showed that the new bone volume (mm³) was significantly higher in the experimental groups than in the control group. Histological analysis showed that new bone areas (%) were significantly higher in the rGO2 and rGO10 than in the control, and significantly higher in rGO4 than in the rGO2 and rGO10. Conclusively, the rGO-coated BCP was found to be effective on osteogenesis and the concentration of the composite was an important factor.

Matrix Metalloproteinases in Bone Resorption, Remodeling, and Repair

Matrix metalloproteinases (MMPs) are the major protease family responsible for the cleavage of the matrisome (global composition of the extracellular matrix (ECM) proteome) and proteins unrelated to the ECM, generating bioactive molecules. These proteins drive ECM remodeling, in association with tissue-specific and cell-anchored inhibitors (TIMPs and RECK, respectively). In the bone, the ECM mediates cell adhesion, mechanotransduction, nucleation of mineralization, and the immobilization of growth factors to protect them from damage or degradation. Since the first description of an MMP in bone tissue, many other MMPs have been identified, as well as their inhibitors. Numerous functions have been assigned to these proteins, including osteoblast/osteocyte differentiation, bone formation, solubilization of the osteoid during bone resorption, osteoclast recruitment and migration, and as a coupling factor in bone remodeling under physiological conditions. In turn, a number of pathologies, associated with imbalanced bone remodeling, arise mainly from MMP overexpression and abnormalities of the ECM, leading to bone osteolysis or bone formation. In this review, we will discuss the functions of MMPs and their inhibitors in bone cells, during bone remodeling, pathological bone resorption (osteoporosis and bone metastasis), bone repair/regeneration, and emergent roles in bone bioengineering.

Comparative proteomic profiling of human osteoblast-derived extracellular matrices identifies proteins involved in mesenchymal stromal cell osteogenic differentiation and mineralization

The extracellular matrix (ECM) is a dynamic component of tissue architecture that physically supports cells and actively influences their behavior. In the context of bone regeneration, cell-secreted ECMs have become of interest as they reproduce tissue-architecture and modulate the promising properties of mesenchymal stem cells (MSCs). We have previously created an in vitro model of human osteoblast-derived devitalized ECM that was osteopromotive for MSCs. The aim of this study was to identify ECM regulatory proteins able to modulate MSC differentiation to broaden the spectrum of MSC clinical applications. To this end, we created two additional models of devitalized ECMs with different mineralization phenotypes. Our results showed that the ECM derived from osteoblast-differentiated MSCs had increased osteogenic potential compared to ECM derived from undifferentiated MSCs and non-ECM cultures. Proteomic analysis revealed that structural ECM proteins and ribosomal proteins were upregulated in the ECM from undifferentiated MSCs. A similar response profile was obtained by treating osteoblast-differentiating MSCs with Activin-A. Extracellular proteins were upregulated in Activin-A ECM, whereas mitochondrial and membrane proteins were downregulated. In summary, this study illustrates that the composition of different MSC-secreted ECMs is important to regulate the osteogenic differentiation of MSCs. These models of devitalized ECMs could be used to modulate MSC properties to regulate bone quality.

Identification of novel genes associated with fracture healing in osteoporosis induced by Krm2 overexpression or Lrp5 deficiency

The aim of the present study was to screen potential key genes associated with osteoporotic fracture healing. The microarray data from the Gene Expression Omnibus database accession number GSE51686, were downloaded and used to identify differentially expressed genes (DEGs) in fracture callus tissue samples obtained from the femora of type I collagen (Col1a1)-kringle containing transmembrane protein 2 (Krm2) mice and low density lipoprotein receptor-related protein 5^−/− (Lrp5^−/−) transgenic mice of osteoporosis compared with those in wild-type (WT) mice. Enrichment analysis was performed to reveal the DEG function. In addition, protein-protein interactions (PPIs) of DEGs were analyzed using the Search Tool for the Retrieval of Interacting Genes database. The coexpression associations between hub genes in the PPI network were investigated, and a coexpression network was constructed. A total of 841 DEGs (335 upregulated and 506 downregulated) were identified in the Col1a1-Krm2 vs. the WT group, and 50 DEGs (16 upregulated and 34 downregulated) were identified in the Lrp5^−/− vs. the WT group. The DEGs in Col1a1-Krm2 mice were primarily associated with immunity and cell adhesion (GO: 0007155) functions. By contrast, the DEGs in Lrp5^−/− mice were significantly associated with muscle system process (GO: 0003012) and regulation of transcription (GO: 0006355). In addition, a series of DEGs demonstrated a higher score in the PPI network, and were observed to be coexpressed in the coexpression network, and included thrombospondin 2 (Thbs2), syndecan 2 (Sdc2), FK506 binding protein 10 (Fkbp10), 2–5-oligoadneylate synthase-like protein 2 (Oasl2), interferon induced protein with tetratricopeptide repeats (Ifit) 1 and Ifit2. Thbs2 and Sdc2 were significantly correlated with extracellular matrix-receptor interactions. The results suggest that Thbs2, Sdc2, Fkbp10, Oasl2, Ifit1 and Ifit2 may serve important roles during the fracture healing process in osteoporosis. In addition, this is the first study to demonstrate that Sdc2, Fkbp10, Oasl2, Ifit1 and Ifit2 may be associated with osteoporotic fracture healing.

Evolution of the Marrow Adipose Tissue Microenvironment

Adipocytes of the marrow adipose tissue (MAT) are distributed throughout the skeleton, are embedded in extracellular matrix, and are surrounded by cells of the hematopoietic and osteogenic lineages. MAT is a persistent component of the skeletal microenvironment and has the potential to impact local processes including bone accrual and hematopoietic function. In this review, we discuss the initial evolution of MAT in vertebrate lineages while emphasizing comparisons to the development of peripheral adipose, hematopoietic, and skeletal tissues. We then apply these evolutionary clues to define putative functions of MAT. Lastly, we explore the regulation of MAT by two major components of its microenvironment, the extracellular matrix and the nerves embedded within. The extracellular matrix and nerves contribute to both rapid and continuous modification of the MAT niche and may help to explain evolutionary conserved mechanisms underlying the coordinated regulation of blood, bone, and MAT within the skeleton.

Associations between FGF21, osteonectin and bone turnover markers in type 2 diabetic patients with albuminuria

AIM

We measured the levels of bone turnover markers (BTMs) in patients with early diabetic nephropathy from type 2 diabetes mellitus (T2DM), and investigated the associations of BTMs with adipokines, serum fibroblast growth factor-21 (FGF21) and osteonectin.

METHODS

We included 159 males and 300 females with T2DM in this cross-sectional study. Clinical characteristics, BTMs and adipokines levels were measured.

RESULTS

One-hundred and ninety-two (41.8%) patients presented with albuminuria. Patients with albuminuria had significantly higher levels of serum osteonectin (P<0.0001) and FGF21 (P=0.0125) than those with normoalbuminuria. Serum levels of P1NP were slightly lower among patients with albuminuria (P=0.031), but the difference disappeared after adjusting for FBG, PBG, and HbA1c. Serum FGF21 levels were independently and negatively related to eGFR (overall β=-0.161, P=0.001; albuminuria group β=-0.240, P=0.001) but not related to uACR. While Osteonectin was independently and positively related to uACR (overall β=0.209, P=0.001; albuminuria group β=0.170, P=0.021). The levels of serum FGF21 were independently inversely related with P1NP (overall β=-0.192, P<0.0001; albuminuria group β=-0.195, P=0.031).

CONCLUSIONS

Our results suggest that persistent hyperglycemia may inhibit bone formation. Both osteonectin and FGF21 were associated with early nephropathy in T2DM patients, albeit with different patterns.

In phyllodes tumors of the breast expression of SPARC (osteonectin/BM40) mRNA by in situ hybridization correlates with protein expression by immunohistochemistry and is associated with tumor progression

Secreted protein acidic and rich in cysteine (SPARC) plays an essential role in tumor invasion and metastasis. The present work was undertaken to detect expression of SPARC mRNA in phyllodes tumors (PTs) and its association with SPARC protein expression. This study also evaluated expression of SPARC mRNA and its correlation between grade and clinical behavior of PTs. In addition, we assessed in PTs the association of expression of SPARC with that of matrix metalloproteinase (MMP)-2 and of MMP-9. SPARC mRNA expression was determined by RNAscope in situ hybridization (ISH) in 50 benign, 22 borderline, and 10 malignant PTs using a tissue microarray. Furthermore, we applied immunohistochemistry (IHC) to examine expression of SPARC, MMP-2, and MMP-9. SPARC mRNA appeared to be concentrated mainly in the stromal compartment of PTs. IHC staining patterns of SPARC protein showed concordance with SPARC mRNA ISH results. Stromal SPARC expression increased continuously as PTs progress from benign through borderline to malignant PTs, both at mRNA (using ISH) (P = 0.044) and protein level (using IHC) (P = 0.000). The recurrence percentage was higher in the stromal SPARC mRNA or protein-positive group than in the SPARC-negative group but this difference was not statistically significant. Stromal SPARC mRNA and protein expression was associated with PT grade and correlated with MMP-2 expression. These results indicate that SPARC-mediated degradation of the extracellular matrix, and its possible association with MMPs, might contribute to progression of PTs.

Osteonectin (SPARC) Expression in Vascular Calcification: In Vitro and Ex Vivo Studies

Osteonectin, also termed SPARC, is a noncollagenous protein of bone matrix. Since there are controversial results regarding its role during the process of vascular calcification, we investigated osteonectin expression in our in vitro calcification model. Rat vascular smooth muscle cells (VSMCs) were challenged with high phosphate (5 mmol/L Pi) and analyzed quantifying calcium levels, through immunohistochemical studies, and studying gene expression. We detected a peak of osteonectin expression at day 7 in cell treated with high phosphate. The time course of calcium deposition, reflected the expression of osteonectin, resulting extensively present at day 7. On the contrary, the expression of the mitotic marker Ki-67 had a peak at day 4, showing no correlation between osteonectin and cell proliferation. Moreover, 7 days was the time point in which Cbfα1/RUNX-2 had its maximal expression. Furthermore, ascorbic acid increased osteonectin expression, supporting a procalcifying role for this protein. Next we decided to study osteonectin expression ex vivo in fetal, adult not calcified, and adult calcific vessels. Immunohistochemical studies demonstrated a spread and strong reactivity in VSMCs of a 20-week fetus, confirming that osteonectin may have a potential role in regulation of mitosis and in cell differentiation. In adult not calcified arteries, osteonectin was constitutively expressed and its levels increased in atherosclerotic and in calcified plaques, where it could have a regulatory role in the calcification process. Our in vitro and ex vivo data show osteonectin expression during the calcification process and suggest its potential role as procalcifying factor.

Proinflammatory Cytokines Regulate Cementogenic Differentiation of Periodontal Ligament Cells by Wnt/Ca(2+) Signaling Pathway

Periodontal inflammation can inhibit cell differentiation of periodontal ligament cells (PDLCs), resulting in decreased bone/cementum regeneration ability. The Wnt signaling pathway, including canonical Wnt/β-catenin signaling and noncanonical Wnt/Ca(2+) signaling, plays essential roles in cell proliferation and differentiation during tooth development. However, little is still known whether noncanonical Wnt/Ca(2+) signaling cascade could regulate cementogenic/osteogenic differentiation capability of PDLCs within an inflammatory environment. Therefore, in this study, human PDLCs (hPDLCs) and their cementogenic differentiation potential were investigated in the presence of cytokines. The data demonstrated that both cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) inhibited cell proliferation, relative alkaline phosphatase activity, bone/cementum-related gene/protein expression, and canonical Wnt pathway-related gene/protein expression in hPDLCs. Interestingly, both cytokines upregulated the noncanonical Wnt/Ca(2+) signaling-related gene and protein expression in hPDLCs. When the Wnt/Ca(2+) pathway was blocked by Ca(2+)/calmodulin-dependent protein kinase II inhibitor KN93, even in the presence of IL-6 and TNF-α, cementogenesis could be stimulated in hPDLCs. Our data indicate that the Wnt/Ca(2+) pathway plays an inhibitory role on PDLC cementogenic differentiation in inflammatory microenvironments. Therefore, targeting the Wnt/Ca(2+) pathway may provide a novel therapeutic approach to improve periodontal regeneration for periodontal diseases.

Inhibition of Transforming Growth Factor-β Activation Diminishes Tumor Progression and Osteolytic Bone Disease in Mouse Models of Multiple Myeloma

Transforming growth factor (TGF)-β supports multiple myeloma progression and associated osteolytic bone disease. Conversion of latent TGF-β to its biologically active form is a major regulatory node controlling its activity. Thrombospondin1 (TSP1) binds and activates TGF-β. TSP1 is increased in myeloma, and TSP1-TGF-β activation inhibits osteoblast differentiation. We hypothesized that TSP1 regulates TGF-β activity in myeloma and that antagonism of the TSP1-TGF-β axis inhibits myeloma progression. Antagonists (LSKL peptide, SRI31277) derived from the LSKL sequence of latent TGF-β that block TSP1-TGF-β activation were used to determine the role of the TSP1-TGF-β pathway in mouse models of myeloma. TSP1 binds to human myeloma cells and activates TGF-β produced by cultured human and mouse myeloma cell lines. Antagonists delivered via osmotic pump in an intratibial severe combined immunodeficiency CAG myeloma model or in a systemic severe combined immunodeficiency CAG-heparanase model of aggressive myeloma reduced TGF-β signaling (phospho-Smad 2) in bone sections, tumor burden, mouse IL-6, and osteoclasts, increased osteoblast number, and inhibited bone destruction as measured by microcomputed tomography. SRI31277 reduced tumor burden in the immune competent 5TGM1 myeloma model. SRI31277 was as effective as dexamethasone or bortezomib, and SRI31277 combined with bortezomib showed greater tumor reduction than either agent alone. These studies validate TSP1-regulated TGF-β activation as a therapeutic strategy for targeted inhibition of TGF-β in myeloma.

Signaling of extracellular matrices for tissue regeneration and therapeutics

Cells receive important regulatory signals from their extracellular matrix (ECM) and the physical property of the ECM regulates important cellular behaviors like cell proliferation, migration and differentiation. A large part of tissue formation and regeneration depends on cellular interaction with its ECM. A comprehensive understanding of the mechanistic biochemical pathway of the ECM components is necessary for the design of a biomaterial scaffold for tissue engineering. Depending on the type of tissue, the ECM requirement might be different and this would influence its downstream intracellular cell signaling. Here, we reviewed the ECM and its signaling pathway by discussing: 1) classification of the ECM into hard, elastic and soft tissue based on its physical properties, 2) proliferation and differentiation control of the ECM, 3) roles of membrane receptor and its intracellular regulation factor, 4) ECM remodeling via inside-out signaling. By providing a comprehensive overview of the ECM's role in mechanotransduction and the self-regulatory effect of cells back on the ECM, we hope to provide a better insight of the physical and biochemical cues from the ECM. A sound understanding on the in vivo ECM has implication on the choice of materials and surface coating of biomimetic scaffolds used for tissue regeneration and therapeutics in a cell-free scaffold.

Extracellular matrix structure

Extracellular matrix (ECM) is a non-cellular three-dimensional macromolecular network composed of collagens, proteoglycans/glycosaminoglycans, elastin, fibronectin, laminins, and several other glycoproteins. Matrix components bind each other as well as cell adhesion receptors forming a complex network into which cells reside in all tissues and organs. Cell surface receptors transduce signals into cells from ECM, which regulate diverse cellular functions, such as survival, growth, migration, and differentiation, and are vital for maintaining normal homeostasis. ECM is a highly dynamic structural network that continuously undergoes remodeling mediated by several matrix-degrading enzymes during normal and pathological conditions. Deregulation of ECM composition and structure is associated with the development and progression of several pathologic conditions. This article emphasizes in the complex ECM structure as to provide a better understanding of its dynamic structural and functional multipotency. Where relevant, the implication of the various families of ECM macromolecules in health and disease is also presented.