Transforming growth factor-beta 1 (TGF-β1) prevents the age-dependent decrease in bone formation in human osteoblast/implant cultures

Advances of Blood Coagulation Factor XIII in Bone Healing

The biologic process of bone healing is complicated, involving a variety of cells, cytokines, and growth factors. As a result of bone damage, the activation of a clotting cascade leads to hematoma with a high osteogenic potential in the initial stages of healing. A major factor involved in this course of events is clotting factor XIII (FXIII), which can regulate bone defect repair in different ways during various stages of healing. Autografts and allografts often have defects in clinical practice, making the development of advanced materials that support bone regeneration a critical requirement. Few studies, however, have examined the promotion of bone healing by FXIII in combination with biomaterials, in particular, its effect on blood coagulation and osteogenesis. Therefore, we mainly summarized the role of FXIII in promoting bone regeneration by regulating the extracellular matrix and type I collagen, bone-related cells, angiogenesis, and platelets, and described the research progress of FXIII = related biomaterials on osteogenesis. This review provides a reference for investigators to explore the mechanism by which FXIII promotes bone healing and the combination of FXIII with biomaterials to achieve targeted bone tissue repair.

The roles of cellular and molecular components of a hematoma at early stage of bone healing

Bone healing is a complex repair process that commences with the formation of a blood clot at the injured bone, termed hematoma. It has evidenced that a lack of a stable hematoma causes delayed bone healing or non-union. The hematoma at the injured bone constitutes the early healing microenvironment. It appears to dictate healing pathways that ends in a regenerative bone. However, the hematoma is often clinically removed from the damaged site. Conversely, blood-derived products have been used in bone tissue engineering for treating critical sized defects, including fibrin gels and platelet-rich plasma. A second generation of platelet concentrate that is based on leukocyte and fibrin content has also been developed and introduced in market. Conflicting effect of these products in bone repair are reported. We propose that the bone healing response becomes dysregulated if the blood response and subsequent formation and properties of a hematoma are altered. This review focuses on the central structural, cellular, and molecular components of a fracture hematoma, with a major emphasis on their roles in regulating bone healing mechanism, and their interactions with mesenchymal stem cells. New angles towards a better understanding of these factors and relevant mechanisms involved at the beginning of bone healing may help to clarify limited or adverse effects of blood-derived products on bone repair. We emphasize that the recreation of an early hematoma niche with critical compositions might emerge as a viable therapeutic strategy for enhanced skeletal tissue engineering.

Aging impairs osteoblast differentiation of mesenchymal stem cells grown on titanium by favoring adipogenesis

Aging negatively affects bone/titanium implant interactions. Our hypothesis is that the unbalance between osteogenesis and adipogenesis induced by aging may be involved in this phenomenon.

Controlling whole blood activation and resultant clot properties by carboxyl and alkyl functional groups on material surfaces: a possible therapeutic approach for enhancing bone healing

Most research virtually ignores the important role of a blood clot in supporting bone healing.

Fibroblast growth factor-2 and bone morphogenetic protein-2 have a synergistic stimulatory effect on bone formation in cell cultures from elderly mouse and human bone

Combined regimens of fibroblast growth factor-2 (FGF-2) and bone morphogenetic protein-2 (BMP-2) were investigated to stimulate osteogenic differentiation. In young mouse calvaria-derived cells, FGF-2 (0.16ng/mL) in combination with BMP-2 (50ng/mL) did not enhance mineralization, but in old mouse cells it resulted in more mineralization than BMP-2 alone. In young long bone mouse cultures, FGF-2 enhanced mineralization relative to BMP-2 alone, but in old cultures, lower dose of FGF-2 (0.016ng/mL) was necessary. In neonatal mouse calvarial cells, sequential delivery of low-dose FGF-2 and low-dose BMP-2 (5ng/mL) was more stimulatory than co-delivery. In young human cultures, 0.016ng/mL of FGF-2 did not enhance mineralization, in combination with 5ng/mL of BMP-2, but in older cultures, codelivery of FGF-2 and BMP-2 was superior to BMP-2 alone. In conclusion, BMP-2 treatment alone was sufficient for maximal mineralization in young osteoblast cultures. However, coadministration of FGF-2 and BMP-2 increases mineralization more than BMP-2 alone in cultures from old and young mouse long bones and old humans but not in young mouse calvarial cultures.

Profiling insulin like factor 3 (INSL3) signaling in human osteoblasts

BACKGROUND

Young men with mutations in the gene for the INSL3 receptor (Relaxin family peptide 2, RXFP2) are at risk of reduced bone mass and osteoporosis. Consistent with the human phenotype, bone analyses of Rxfp2(-/-) mice showed decreased bone volume, alterations of the trabecular bone, reduced mineralizing surface, bone formation, and osteoclast surface. The aim of this study was to elucidate the INSL3/RXFP2 signaling pathways and targets in human osteoblasts.

METHODOLOGY/PRINCIPAL FINDINGS

Alkaline phosphatase (ALP) production, protein phosphorylation, intracellular calcium, gene expression, and mineralization studies have been performed. INSL3 induced a significant increase in ALP production, and Western blot and ELISA analyses of multiple intracellular signaling pathway molecules and their phosphorylation status revealed that the MAPK was the major pathway influenced by INSL3, whereas it does not modify intracellular calcium concentration. Quantitative Real Time PCR and Western blotting showed that INSL3 regulates the expression of different osteoblast markers. Alizarin red-S staining confirmed that INSL3-stimulated osteoblasts are fully differentiated and able to mineralize the extracellular matrix.

CONCLUSIONS/SIGNIFICANCE

Together with previous findings, this study demonstrates that the INSL3/RXFP2 system is involved in bone metabolism by acting on the MAPK cascade and stimulating transcription of important genes of osteoblast maturation/differentiation and osteoclastogenesis.

Effects of autogenous growth factors on heterotopic bone formation of osteogenic cells in small animal model

AIMS

This study used a new approach to investigate the effective concentrations of growth factors released from platelet concentrate (PC) on the bone formation capacity of osteogenically differentiated rat bone marrow stromal cells (rBMSCs).

MATERIALS AND METHODS

Rat BMSCs and whole blood were harvested from 40 adult male Spraque-Dawly rats. Rat BMSCs were expanded in an osteogenic medium and seeded on inert collagenous bovine bone matrix (ICBM). Growth factors released from degranulated PC (GFs) containing TGF-β1 1 (25ng/ml)-10ng (250ng/ml) and rhBMP-2 400ng (10μg/ml) were suspended in 40μl platelet poor plasma (PPP) and applied on the ICBM-rBMSC constructs or ICBM only, respectively. The constructs were then transplanted in autologous hosts for 4 weeks. Concurrently, osteoblastic differentiation of rBMSCs on ICBM-rBMSC-PPP constructs was characterized in vitro.

RESULTS

Rat BMSCs in osteogenic medium exhibited phenotypes of mature osteoblasts. The amount of newly formed bone among groups of ICBM-rBMSC-PPP with and without GFs was not significantly different (p>0.05) and was significantly lower than a group of ICBM-PPP-BMP-2 (p<0.05).

CONCLUSIONS

Autogenous GFs had no effect on the capacity of rBMSCs to form new bone. The ability to measure the bone formation capacity of transplanted autologous cells and growth factors in a small animal model was demonstrated.

Prolonged and repeated upright posture promotes bone formation in rat lumbar vertebrae

STUDY DESIGN

Both forelimbs of rats were amputated and these rats were kept in the custom-made cages to keep prolonged and repeated upright posture. Changes of bone were observed in the lumbar vertebrae at three different time points after the surgery. OBJECTIVE.: To investigate the effect of prolonged and repeated upright posture on bone formation of rat lumbar vertebrae.

SUMMARY OF BACKGROUND DATA

Previous studies show long-term and repeated load-induced bone formation, but there are no clear evidences to indicate whether or not long-term and repeated assumption of the upright posture could result in bone formation at rat lumbar vertebrae.

METHODS

The forelimbs of 30 rats were amputated when they were 1 month old. These rats were kept in the custom-made cages and were forced to stand upright on their hindlimbs and tails to obtain water and food. Normal rats of the same ages kept in regular cages were used as control. The rats were sacrificed at 5, 7, and 9 months after the surgery and lumbar vertebrae samples were harvested for micro-computed tomographic (CT), histological, and immunohistochemical studies. Total RNA isolated from these samples were used for real-time polymerase chain reaction of type I collagen (Col1α2), type X collagen (Col10α1), transforming growth factor-β1 (TGF-β1) and its related nuclear transcript factor runt-related transcription factor 2 (Runx2), as well as the biomarker of angiogenesis and vascular invasion, which is also a prerequisite for endochondral bone formation: vascular endothelial growth factor (VEGF).

RESULTS

Micro-CT and histological studies showed increased trabecular bone density and increased osteoblast quantities of lumbar vertebrae after surgery. Immunostaining revealed increased protein expression of type I collagen, type X collagen, TGF-β, and VEGF. Real-time polymerase chain reaction showed upregulated expression of Col1α2, Col10α1, VEGF, TGF-β1, and Runx2 mRNA.

CONCLUSION

Upright posture induces bone acquisition in the rats' lumbar spine, primarily through the mode of the endochondral ossification, which is associated with increased loading, activated VEGF, and TGF-β1 signaling.

Serum transforming growth factor beta-1 post hip fracture repair in elderly patients

BACKGROUND

To determine the kinetics of serum transforming growth factor beta-1 (TGF-β1) in aged hip fracture patients during a month post-op. and determine its relationship to complications and cognitive status.

METHODS

Forty-one elderly patients were prospectively followed. Serum TGF-β1 was obtained during the first 10h post-fracture (baseline) and pre-surgery, 48-60 h post-op., 7 and 30 days post-op.

RESULTS

Mean age was 81.8±7.7, range 68-97 years. A significant increase in serum TGF-β1 (from baseline) was observed on the seventh day post-op., lasting for at least 1 month (p = 0.004). Sixteen patients experienced post-op. complications. Serum TGF-β1 of patients with complications was significantly higher compared to patients without complications (p = 0.039). More complications were found in impaired mental status (IMS) patients (9/12) compared to cognitively normal patients (10/29), (p = 0.037). However, no differences were found in serum TGF-β1 between IMS and normal patients, nor was a correlation found between age and TGF-β1 production. No differences were found between genders.

CONCLUSIONS

There is a distinct increase in serum TGF-β1, a week post hip fracture repair, lasting for at least a month, which is significantly higher in patients with post-op. complications. TGF-β1 seems to be essential to the healing process post hip fracture repair; still its clinical applications have as yet to be determined.

Fibroblast growth factor-2 stimulates the proliferation of mesenchyme-derived progenitor cells from aging mouse and human bone

The potential of fibroblast growth factor-2 (FGF-2) to stimulate osteoprogenitors in aging bone was investigated. Previous work showed a decrease in bone formation in cell cultures derived from bone of elderly female patients, but not in cells from age-matched male or younger female patients, with transforming growth factor β increasing bone formation but not increasing osteoprogenitors. In the present study, FGF-2 was shown to significantly stimulate, in a dose-dependent manner, proliferation of mesenchyme-derived progenitor cells from bones of young and old mouse and humans. In proliferation assays, human cells were more responsive to lower concentrations (0.0016 ng/mL) of FGF-2 than mouse cells, but proliferation was less in cells from older bone. Immunofluorescence microscopy revealed that FGF-2 increased and prevented the decline in cells expressing activated leukocyte cell adhesion molecule, a novel marker for early lineage osteoblasts, but not α-smooth muscle actin. FGF-2 may have therapeutic potential for stimulating osteoblast progenitors in aging.

Preparation and characterization of selenium incorporated anodic conversion coatings on titanium surfaces for biomedical applications

An anodic spark deposition process was used for preparation of inorganic, glass-ceramic like conversion coatings. The microstructure of the layers was characterized by surface and solid state techniques such as scanning electron microscopy, electron probe microanalysis and Raman spectroscopy. The porous coatings, typically up to 8 mum thick, consist mainly of titanium oxides and amounts of incorporated electrolyte constituents like Se, Ca or P. Beside nano crystalline anatase phases, a mostly amorphous structure is proposed in which network-forming [PO(4)] tetrahedras and [TiO(6)] octahedras in various degrees of condensation are connected. A drastic modification of the film structure was observed when selenium was incorporated into the glassy oxide structure of the coating. In these cases no nano crystalline phases of titanium oxides or other chemical compounds were detected. First cell culture investigations show a significant improvement of the biological properties. Cell proliferation and TGF-beta-expression of these coatings in comparison with commercial pure titanium (CPT) with native titanium oxide films were examined.

Histamine receptor H1 and dermatopontin: new downstream targets of the vitamin D receptor

In this study, we used multipotential MSCs and microarray assays to follow the changing patterns of gene expression as MSCs were differentiated to osteoblasts. We analyzed co-expressed gene groups to identify new targets for known transcription factor VDR during differentiation. The roles of two genes (histamine receptor H1 and dermatopontin) as downstream targets for the VDR were confirmed by gel electromotility shift, siRNA inhibition, and chromatin immunoprecipitation assays.

INTRODUCTION

Osteogenesis is stringently controlled by osteoblast-specific signaling proteins and transcription factors. Mesenchymal stem or multipotential stromal cells from bone marrow (MSCs) have been shown to differentiate into osteoblasts in the presence of vitamin D(3).

MATERIALS AND METHODS

We used MSCs and microarray assays to follow the changing patterns of gene expression as MSCs were differentiated to osteoblasts. The data were analyzed with a previously developed strategy to identify new downstream targets of the vitamin D receptor (VDR), known osteogenesis transcription factor. Hierarchical clustering of the data identified 15 distinct patterns of gene expression. Three genes were selected that expressed in the same time-dependent pattern as osteocalcin, a known target for the VDR: histamine receptor H1 (HRH1), Spondin 2 (SPN), and dermatopontin (DPT). RT-PCR, electromotility shift, siRNA inhibition assays, and chromatin immunoprecipitation assays were used to analyze the role of VDR in activation of DPT and HRH1 during differentiation.

RESULTS AND CONCLUSIONS

RT-PCR assays confirmed that the genes were expressed during differentiation of MSCs. The roles of two genes as downstream targets for the VDR were confirmed by gel electromotility shift and chromatin immunoprecipitation assays that showed the presence of VDR complex binding sequences. Overexpression of VDR in MG-63 osteosarcoma cells induced the expression of HRH1 and DPT. Inhibition studies with siRNA to DPT and HRH1 showed a decrease in MSC differentiation to osteogenic lineage. In addition, osteogenic differentiation of MSCs was inhibited by the HRH1 inhibitor mepyramine but not the HRH2 inhibitor ranitidine. In conclusion, we show that analysis of co-expressed gene groups is a good tool to identify new targets for known transcription factors.

Inhibition of Alveolar Osteitis in Mandibular Tooth Extraction Sites Using Platelet-Rich Plasma

Alveolar osteitis (AO), also known as dry socket, continues to be a complication of tooth removal. Platelet-rich plasma (PRP) can be used to accelerate both soft and hard tissue healing. This paper is a retrospective review of the benefits of PRP in AO prevention. PRP was obtained from patients for use in the postremoval alveolar sockets of mandibular molar extraction sites. Statistical analysis of 904 extraction sites with and without PRP use was examined. PRP significantly reduced the incidence of AO by 62.1%, from 9.57% in patients not receiving PRP to 3.63% in patients who received PRP (P = .00043). PRP use had benefits in all subpopulations. The odds of AO occurring in patients not receiving PRP treatment following tooth extraction was 2.81 times greater than in patients receiving PRP treatment immediately following tooth extraction. Four statistically significant risk factors for AO were identified: complete impaction, oral contraceptive use, bruxism, and failure to administer PRP. The application of PRP can significantly reduce the incidence of AO even in patients with risk factors for AO, such as removal of impacted teeth, bruxism, and oral contraceptive use. PRP may be of benefit because it helps initiate clot formation, provides growth factors to facilitate the healing process, and contains concentrated white blood cells to inhibit infection. The use of PRP following tooth extraction is a simple, cost-effective technique that can be used to decrease the incidence of AO and therefore decrease postoperative pain.