Conditioned medium from fresh and demineralized bone enhances osteoclastogenesis in murine bone marrow cultures

Biofunctionalization of Collagen Barrier Membranes with Bone-Conditioned Medium, as a Natural Source of Growth Factors, Enhances Osteoblastic Cell Behavior

A key principle of guided bone regeneration (GBR) is the use of a barrier membrane to prevent cells from non-osteogenic tissues from interfering with bone regeneration in patients with hard tissue deficiencies. The aim of the study was to investigate whether the osteoinductive properties of bone-conditioned medium (BCM) obtained from cortical bone chips harvested at the surgical site can be transferred to a native bilayer collagen membrane (nbCM). BCM extracted within 20 or 40 min, which corresponds to a typical implant surgical procedure, and BCM extracted within 24 h, which corresponds to BCM released from the autologous bone chips in situ, contained significant and comparable amounts of TGF-β1, IGF-1, FGF-2, VEGF-A, and IL-11. Significant (p < 0.001) quantities of BMP-2 were only detected in the 24-h BCM preparation. The bioactive substances contained in the BCM were adsorbed to the nbCMs with almost 100% efficiency. A fast but sequential release of all investigated proteins occurred within 6-72 h, reflecting their stepwise involvement in the natural regeneration process. BCM-coated nbCM significantly (p < 0.05) increased the migratory, adhesive, and proliferative capacity of primary human bone-derived cells (hBC), primary human periodontal ligament cells (hPDLC), and an osteosarcoma-derived osteoblastic cell line (MG-63) compared to cells cultured on BCM-free nbCM. The high proliferative rates of MG-63 cells cultured on BCM-free nbCM were not further potentiated by BCM, indicating that BCM-coated nbCM has no detrimental effects on cancer cell growth. BCM-coated nbCM caused significant (p < 0.05) induction of early osteogenic marker gene expression and alkaline phosphatase activity, suggesting an important role of BCM-functionalized nbCM in the initiation of osteogenesis. The 24-h BCM loaded on the nbCM was the only BCM preparation that caused significant induction of late osteogenic marker gene expression. Altogether, our data define the pre-activation of collagen membranes with short-term-extracted BCM as a potential superior modality for treating hard tissue deficiencies via GBR.

Cellular responses to deproteinized bovine bone mineral biofunctionalized with bone-conditioned medium

OBJECTIVES

The aim of the study was to investigate whether the osteoinductive properties of bone-conditioned medium (BCM) harvested from cortical bone chips within a clinically relevant short-term period can enhance the biologic characteristics of deproteinized bovine bone mineral (DBBM) in vitro.

MATERIALS AND METHODS

To assess the biofunctionalization of DBBM, the adhesive, proliferative, and differentiation properties of mesenchymal stromal ST2, pre-osteoblastic MC3T3-E1, and primary bone-derived cells grown on BCM-coated DBBM were examined by crystal violet staining of adherent cells, BrdU ELISA, and qRT-PCR, respectively.

RESULTS

BCM extracted within 20 min or 24 h in either Ringer's solution (BCM-RS) or RS mixed with autologous serum (BCM-RS + S) increased the adhesive properties of all three cell types seeded on DBBM. The 20-min BCM-RS preparation appeared more potent than the 24-h preparation. BCM-RS made within 20 min or 24 h had strong pro-proliferative effects on all cell types grown on DBBM. RS + S alone exhibited a considerable pro-proliferative effect, suggesting an impact of the serum on cellular growth. DBBM coated with BCM-RS or BCM-RS + S, made within 20 min or 24 h each, caused a significant induction of osteogenic differentiation marker expression with a higher potency of the BCM-RS + S. Finally, a strong additive effect of fresh bone chips combined with BCM-coated DBBM on the osteogenic differentiation of the three cell types was observed.

CONCLUSIONS

Altogether, the data strongly support the biofunctionalization of DBBM with BCM extracted within a clinically relevant time window of 20 min.

CLINICAL RELEVANCE

Pre-activation of non-osteoinductive biomaterials with BCM, prepared from autologous bone chips during a guided bone regeneration (GBR) procedure, bears the potential of an optimal treatment modality for bone defects in daily practice.

Urothelium with barrier function differentiated from human urine-derived stem cells for potential use in urinary tract reconstruction

Background

Autologous urothelial cells are often obtained via bladder biopsy to generate the bio-engineered urethra or bladder, while urine-derived stem cells (USC) can be obtained by a non-invasive approach. The objective of this study is to develop an optimal strategy for urothelium with permeability barrier properties using human USC which could be used for tissue repair in the urinary tract system.

Methods

USC were harvested from six healthy adult individuals. To optimize urothelial differentiation, five different differentiation methods were studied. The induced cells were assessed for gene and protein expression markers of urothelial cells via RT-PCR, Western blotting, and immunofluorescent staining. Barrier function and ultrastructure of the tight junction were assessed with permeability assays and transmission electron microscopy (TEM). Induced cells were both cultured on trans-well membranes and small intestinal submucosa, then investigated under histology analysis.

Results

Differentiated USC expressed significantly higher levels of urothelial-specific transcripts and proteins (Uroplakin III and Ia), epithelial cell markers (CK20 and AE1/AE3), and tight junction markers (ZO-1, ZO-2, E-cadherin, and Cingulin) in a time-dependent manner, compared to non-induced USC. In vitro assays using fluorescent dye demonstrated a significant reduction in permeability of differentiated USC. In addition, transmission electron microscopy confirmed appropriate ultrastructure of urothelium differentiated from USC, including tight junction formation between neighboring cells, which was similar to positive controls. Furthermore, multilayered urothelial tissues formed 2 weeks after USC were differentiated on intestine submucosal matrix.

Conclusion

The present study illustrates an optimal strategy for the generation of differentiated urothelium from stem cells isolated from the urine. The induced urothelium is phenotypically and functionally like native urothelium and has proposed uses in in vivo urological tissue repair or in vitro urethra or bladder modeling.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1035-6) contains supplementary material, which is available to authorized users.

Bone-conditioned medium contributes to initiation and progression of osteogenesis by exhibiting synergistic TGF-β1/BMP-2 activity

Guided bone regeneration (GBR) often utilizes a combination of autologous bone grafts, deproteinized bovine bone mineral (DBBM), and collagen membranes. DBBM and collagen membranes pre-coated with bone-conditioned medium (BCM) extracted from locally harvested autologous bone chips have shown great regenerative potential in GBR. However, the underlying molecular mechanism remains largely unknown. Here, we investigated the composition of BCM and its activity on the osteogenic potential of mesenchymal stromal cells. We detected a fast and significant (P < 0.001) release of transforming growth factor-β1 (TGF-β1) from autologous bone within 10 min versus a delayed bone morphogenetic protein-2 (BMP-2) release from 40 min onwards. BCMs harvested within short time periods (10, 20, or 40 min), corresponding to the time of a typical surgical procedure, significantly increased the proliferative activity and collagen matrix production of BCM-treated cells. Long-term (1, 3, or 6 days)-extracted BCMs promoted the later stages of osteoblast differentiation and maturation. Short-term-extracted BCMs, in which TGF-β1 but no BMP-2 was detected, reduced the expression of the late differentiation marker osteocalcin. However, when both growth factors were present simultaneously in the BCM, no inhibitory effects on osteoblast differentiation were observed, suggesting a synergistic TGF-β1/BMP-2 activity. Consequently, in cells that were co-stimulated with recombinant TGF-β1 and BMP-2, we showed a significant stimulatory and dose-dependent effect of TGF-β1 on BMP-2-induced osteoblast differentiation due to prolonged BMP signaling and reduced expression of the BMP-2 antagonist noggin. Altogether, our data provide new insights into the molecular mechanisms underlying the favorable outcome from GBR procedures using BCM, derived from autologous bone grafts.

‘Bone-conditioned medium’ could improve oral bone regeneration therapy by promoting the proliferation and maturation of bone-forming cells. Building on recent research demonstrating the benefits of using cell culture medium prepared with bone chips (BCM) in such treatments, researchers led by Maria Asparuhova of the University of Bern, Switzerland, set out to elucidate the medium’s mechanisms. The team found that BCM incubated with bone chips for short periods—as little as ten minutes—contained heightened levels of signaling protein TGF-β1, which enhanced mouse bone marrow cell proliferation while downregulating maturation. BCM incubated for longer periods also generated increased levels of another protein, BMP-2, which boosted the maturation of bone-forming cells. This study reveals a sequential role of these two factors in oral bone development, and the potential physiological actions of BCM when used in regenerative therapies.

Human bone graft cytocompatibility with mesenchymal stromal cells is comparable after thermal sterilization and washing followed by γ-irradiation: an in vitro study

Human bone allografts present a better alternative to autografts in terms of minimization of the harvesting procedure complications. Prior to the use in clinical applications, they require sterilization which aims to reduce bioburden. This often comes at the expense of their biological properties as carriers of cells. In this study, we evaluated the cytocompatibility of human bone allografts processed and sterilized by three different methods with mesenchymal stromal cells. Bone morphology, biological and biochemical properties of the extracted bone-conditioned medium and viability of cells were assessed. We found that chemical sterilization had a strong negative effect on cell viability, whereas thermal sterilization and washing with subsequent γ-irradiation both resulted in a bone graft compatible with the progenitor cells. Moreover, washing of the bone prior to sterilization allowed solid removal of cell debris and other bone marrow components. Taken together, our findings demonstrate the importance of a proper choice of the bone graft processing method for the production of the biomaterial suitable for tissue engineering.

Gene markers of fracture healing in early stage and the regulatory mechanism during the process using microarray analysis

BACKGROUND

The aim of this study was to explore crucial markers and uncover the regulatory mechanisms of fracture healing in the early stage.

METHODS

Gene expression profile of GSE45156 was downloaded, in which 3 fractured samples and 3 unfractured samples were used in our present study. Based on the threshold value, differentially expressed genes (DEGs) were selected between two kinds of samples using limma package in R. Enrichment analysis of these DEGs was performed by DAVID software. Furthermore, protein-protein interaction (PPI) network was established integrating information in STRING database, and visualized by Cytoscape software.

RESULTS

We identified a set of 960 DEGs including 509 up-regulated and 451 downregulated genes. Biological processes involving RNA splicing and cell cycle were significantly enriched for the up-regulated genes such as Snrpd2, Eftud2, Plk1 and Bub1b, whereas skeletal system development and bone development processes were predominant for down-regulated genes like Ubc. In the constructed PPI network, all the five genes were the predominant nodes, of which Snrpd2 was linked to Eftud2, while Bub1b was to interact with Plk1.

CONCLUSION

Five candidate genes crucial for indicating the process of fracture in early stage were identified. Eftud2, Snrpd2, Bub1b and Plk1 might function through the involvement of cell-cycle-related BP, while Ubc might influence the protein degradation during bone development. However, more experimental validations are needed to confirm these results.

Bone conditioned media (BCM) improves osteoblast adhesion and differentiation on collagen barrier membranes

BACKGROUND

The use of autogenous bone chips during guided bone regeneration procedures has remained the gold standard for bone grafting due to its excellent combination of osteoconduction, osteoinduction and osteogenesis. Recent protocols established by our group have characterized specific growth factors and cytokines released from autogenous bone that have the potential to be harvested and isolated into bone conditioned media (BCM). Due to the advantageous osteo-promotive properties of BCM, the aims of the present study was to pre-coat collagen barrier membranes with BCM and investigate its effect on osteoblast adhesion, proliferation and differentiation for possible future clinical use.

METHODS

Scanning electron microscopy (SEM) was first used to qualitative assess BCM protein accumulation on the surface of collagen membranes. Thereafter, undifferentiated mouse ST2 stromal bone marrow cells were seeded onto BioGide porcine derived collagen barrier membranes (control) or barrier membranes pre-coated with BCM (test group). Control and BCM samples were compared for cell adhesion at 8 h, cell proliferation at 1, 3 and 5 days and real-time PCR at 5 days for osteoblast differentiation markers including Runx2, alkaline phosphatase (ALP), osteocalcin (OCN) and bone sialoprotein (BSP). Mineralization was further assessed with alizarin red staining at 14 days post seeding.

RESULTS

SEM images demonstrated evidence of accumulated proteins found on the surface of collagen membranes following coating with BCM. Analysis of total cell numbers revealed that the additional pre-coating with BCM markedly increased cell attachment over 4 fold when compared to cells seeded on barrier membranes alone. No significant difference could be observed for cell proliferation at all time points. BCM significantly increased mRNA levels of osteoblast differentiation markers including ALP, OCN and BSP at 5 days post seeding. Furthermore, barrier membranes pre-coated with BCM demonstrated a 5-fold increase in alizarin red staining at 14 days.

CONCLUSION

The results from the present study suggest that the osteoconductive properties of porcine-derived barrier membranes could be further improved by BCM by significantly increasing cell attachment, differentiation and mineralization of osteoblasts in vitro. Future animal testing is required to fully characterize the additional benefits of BCM for guided bone regeneration.

Pre-coating deproteinized bovine bone mineral (DBBM) with bone-conditioned medium (BCM) improves osteoblast migration, adhesion, and differentiation in vitro

OBJECTIVES

Autogenous bone grafting has remained the gold standard for bone augmentation procedures with ability to release growth factors to the surrounding microenvironment. Recent investigations have characterized these specific growth factors released by autogenous bone chips with further isolation into a "bone-conditioned medium" (BCM). The aim of the present investigation was to utilize autologous growth factors from bone chips (BCM) in combination with deproteinized bovine bone mineral (DBBM) and investigate the ability for BCM to enhance osteoblast behavior.

MATERIALS AND METHODS

Mouse ST2 cells were seeded on (1) DBBM particles alone or (2) DBBM + BCM. Thereafter, samples were compared for cell recruitment, adhesion, proliferation, and real-time PCR for osteoblast differentiation markers including Runx2, collagen 1 alpha 2 (COL1A2), alkaline phosphatase (ALP), and osteocalcin (OCN). Alizarin red staining was used to assess mineralization.

RESULTS

Coating BCM on DBBM particles improved cell migration of ST2 cells and significantly enhanced a 2-fold increase in cell adhesion. While no significant increase in cell proliferation was observed, BCM significantly increased mRNA levels of COL1A2, ALP, and OCN at 3 days post seeding. Furthermore, a 3-fold increase in alizarin red staining was observed on DBBM particles pre-coated with BCM.

CONCLUSION

Pre-coating DBBM with BCM enhanced the osteoconductive properties of DBBM by mediating osteoblast recruitment, attachment, and differentiation towards bone-forming osteoblasts. Future animal study is necessary to further characterize the added benefit of BCM as an autogenous growth factor source for combination therapies.

CLINICAL RELEVANCE

The application of BCM in combination with biomaterials may serve as an autogenous growth factor source for bone regeneration.