Enhanced Osteogenic Behavior of ADSCs Produced by Deproteinized Antler Cancellous Bone and Evidence for Involvement of ERK Signaling Pathway

Bone Tissue Engineering Strategies for Alveolar Cleft: Review of Preclinical Results and Guidelines for Future Studies

The current standard of care for an alveolar cleft defect is an autogenous bone graft, typically from the iliac crest. Given the limitations of alveolar bone graft surgery, such as limited supply, donor site morbidity, graft failure, and need for secondary surgery, there has been growing interest in regenerative medicine strategies to supplement and replace traditional alveolar bone grafts. Though there have been preliminary clinical studies investigating bone tissue engineering methods in human subjects, lack of consistent results as well as limitations in study design make it difficult to determine the efficacy of these interventions. As the field of bone tissue engineering is rapidly advancing, reconstructive surgeons should be aware of the preclinical studies informing these regenerative strategies. We review preclinical studies investigating bone tissue engineering strategies in large animal maxillary or mandibular defects and provide an overview of scaffolds, stem cells, and osteogenic agents applicable to tissue engineering of the alveolar cleft. An electronic search conducted in the PubMed database up to December 2021 resulted in 35 studies for inclusion in our review. Most studies showed increased bone growth with a tissue engineering construct compared to negative control. However, heterogeneity in the length of follow up, method of bone growth analysis, and inconsistent use of positive control groups make comparisons across studies difficult. Future studies should incorporate a pediatric study model specific to alveolar cleft with long-term follow up to fully characterize volumetric defect filling, cellular ingrowth, bone strength, tooth movement, and implant support.

Substrate stiffness can affect the crosstalk between adipose derived mesenchymal stem cells and macrophages in bone tissue engineering

Purpose: This study aimed to explore the effect of biomaterials with different stiffness on Adipose Derived Mesenchymal Stem Cells (ADSC)-macrophage crosstalk in bone tissue engineering and its role in bone repair. Methods: Biomaterials with Young's modulus of 64 and 0.2 kPa were selected, and the crosstalk between ADSCs and macrophages was investigated by means of conditioned medium treatment and cell co-culture, respectively. Polymerase chain reaction (PCR) and flow cytometry were used to evaluate the polarization of macrophages. Alkaline phosphatase (ALP) and alizarin red staining (ARS) solutions were used to evaluate the osteogenic differentiation of ADSCs. Transwell assay was used to evaluate the chemotaxis of ADSCs and macrophages. Moreover, mass spectrometry proteomics was used to analyze the secreted protein profile of ADSCs of different substrates and macrophages in different polarization states. Results: On exploring the influence of biomaterials on macrophages from ADSCs on different substrates, we found that CD163 and CD206 expression levels in macrophages were significantly higher in the 64-kPa group than in the 0.2-kPa group in conditioned medium treatment and cell co-culture. Flow cytometry showed that more cells became CD163+ or CD206+ cells in the 64-kPa group under conditioned medium treatment or cell co-culture. The Transwell assay showed that more macrophages migrated to the lower chamber in the 64-kPa group. The proteomic analysis found that ADSCs in the 64-kPa group secreted more immunomodulatory proteins, such as LBP and RBP4, to improve the repair microenvironment. On exploring the influence of biomaterials on ADSCs from macrophages in different polarization states, we found that ALP and ARS levels in ADSCs were significantly higher in the M2 group than in the other three groups (NC, M0, and M1 groups) in both conditioned medium treatment and cell co-culture. The Transwell assay showed that more ADSCs migrated to the lower chamber in the M2 group. The proteomic analysis found that M2 macrophages secreted more extracellular remodeling proteins, such as LRP1, to promote bone repair. Conclusion: In bone tissue engineering, the stiffness of repair biomaterials can affect the crosstalk between ADSCs and macrophages, thereby regulating local repair immunity and affecting bone repair.

MiRNA Profiling and Its Potential Roles in Rapid Growth of Velvet Antler in Gansu Red Deer (Cervus elaphus kansuensis)

A significant variety of cell growth factors are involved in the regulation of antler growth, and the fast proliferation and differentiation of various tissue cells occur during the yearly regeneration of deer antlers. The unique development process of velvet antlers has potential application value in many fields of biomedical research. Among them, the nature of cartilage tissue and the rapid growth and development process make deer antler a model for studying cartilage tissue development or rapid repair of damage. However, the molecular mechanisms underlying the rapid growth of antlers are still not well studied. MicroRNAs are ubiquitous in animals and have a wide range of biological functions. In this study, we used high-throughput sequencing technology to analyze the miRNA expression patterns of antler growth centers at three distinct growth phases, 30, 60, and 90 days following the abscission of the antler base, in order to determine the regulatory function of miRNA on the rapid growth of antlers. Then, we identified the miRNAs that were differentially expressed at various growth stages and annotated the functions of their target genes. The results showed that 4319, 4640, and 4520 miRNAs were found in antler growth centers during the three growth periods. To further identify the essential miRNAs that could regulate fast antler development, five differentially expressed miRNAs (DEMs) were screened, and the functions of their target genes were annotated. The results of KEGG pathway annotation revealed that the target genes of the five DEMs were significantly annotated to the "Wnt signaling pathway", "PI3K-Akt signaling pathway", "MAPK signaling pathway", and "TGF-β signaling pathway", which were associated with the rapid growth of velvet antlers. Therefore, the five chosen miRNAs, particularly ppy-miR-1, mmu-miR-200b-3p, and novel miR-94, may play crucial roles in rapid antler growth in summer.

In vivo evaluation of deer antler trabecular bone as a reconstruction material for bone defects

Availability of graft materials to fill up osseous defects has always been a concern in orthopaedic surgeries. Deer antler material is a primary bone structure that is easy to collect and could serve as a xenograft. This study examines the behaviour of red deer antler trabecular cylinders in critical size distal femoral epiphyseal defects in 11 rabbits, and evaluates the effect of the decellularization protocols. Two preparation regimes (A and B) were used, with and without lipids and proteins. Radiographs were taken immediately after surgery and after euthanasia 12 weeks post-implantation. Histological evaluation was performed on non-decalcified 10-μm sections with a van Gieson picro-fuchsin staining protocol. A region of interest was defined for each histological section, evaluating the inflammatory reaction, the fibrosis process, and the osteogenesis. Each histological section was microradiographed to evaluate bone contact, presence of synostosis, remodelling and ossification processes. All antler cylinders were successfully implanted. Final radiographic analysis demonstrated osteointegration of most implants at various stages. Light to moderate inflammation around the grafts was noted with only one case showing full encapsulation. A variable degree of intimacy between implant and host bone was evidenced, with bone remodelling and osteogenesis of various intensity being present in all implanted sites. No differences were found between group A and B. Removal of lipids and proteins in the grafts surprisingly did not seem to matter. Decellularization and sterilization protocols may be advocated. Although it presents several limitations, this study shows some promising results regarding antler trabecular bone osteointegration.

Design of two natural deproteinized bovine bone scaffolds and evaluation of the effect of initial cell seeding density on repairing bone defects

Engineering functional bone using combinations of cells, scaffolds, and bioactive factors is a promising strategy for the bone-tissue regeneration, while challenge remains. Chemical methods deproteinizing natural bovine cancellous bone to remove immunogenic are poorly understood, and the cell seeding density to promote bone formation still needs to be clarified. In this study, 8.0 × 8.0 × 2.0 mm bovine cancellous bones were either treated with H₂ O₂ for 8 hr or pepsin for 24 hr and then inoculated with MC3T3-E1 osteoblasts with two cell densities (1 × 10⁶ cells/ml or 4 × 10⁶ cells/ml)separately. We compared the appearance of the bones treated by the two chemical deproteinizing methods, as well as the proliferation ability of the inoculating cell density at 1 × 10⁶ cells/ml. Moreover, scanning electron microscopy was done to analyze the growth of cells on the surface of the material, and an alkaline phosphatase assay was performed to assess osteogenic differentiation. We showed that both treated bones treatments are biocompatible, but bones treated with H₂ O₂ were more conducive to osteoblast differentiation and ALP secretion, especially when seeded at the higher cell density at 4 × 10⁶ cells/ml. We concluded that chemical deproteinized bovine cancellous bones met the basic bone graft material requirements. Cell seeding density is an important factor to promote the material's osteogenic ability, with H₂ O₂ -deproteinized bones exhibiting enhanced osteoblast differentiation.

The State of the Art and Prospects for Osteoimmunomodulatory Biomaterials

The critical role of the immune system in host defense against foreign bodies and pathogens has been long recognized. With the introduction of a new field of research called osteoimmunology, the crosstalk between the immune and bone-forming cells has been studied more thoroughly, leading to the conclusion that the two systems are intimately connected through various cytokines, signaling molecules, transcription factors and receptors. The host immune reaction triggered by biomaterial implantation determines the in vivo fate of the implant, either in new bone formation or in fibrous tissue encapsulation. The traditional biomaterial design consisted in fabricating inert biomaterials capable of stimulating osteogenesis; however, inconsistencies between the in vitro and in vivo results were reported. This led to a shift in the development of biomaterials towards implants with osteoimmunomodulatory properties. By endowing the orthopedic biomaterials with favorable osteoimmunomodulatory properties, a desired immune response can be triggered in order to obtain a proper bone regeneration process. In this context, various approaches, such as the modification of chemical/structural characteristics or the incorporation of bioactive molecules, have been employed in order to modulate the crosstalk with the immune cells. The current review provides an overview of recent developments in such applied strategies.

Biomineralizaion of hydroxyapatite on polyethylene terephthalate artificial ligaments promotes graft-bone healing after anterior cruciate ligament reconstruction: An in vitro and in vivo study

The purpose of the present study is to modify the polyethylene terephthalate ligament with hydroxyapatite via biomineralization and to investigate its effect on graft-bone healing. After biomineralization of hydroxyapatite, the surface characterization of polyethylene terephthalate ligament was examined by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and water contact angle measurements. The compatibility and osteoinduction, along with the underlying signaling pathway involved of hydroxyapatite-polyethylene terephthalate ligament, were evaluated in vitro. Moreover, a rabbit anterior cruciate ligament reconstruction model was established, and the polyethylene terephthalate or hydroxyapatite-polyethylene terephthalate artificial ligament was implanted into the knee. The micro-computed tomography analysis, histological, and immunohistochemical examination as well as biomechanical test were performed to investigate the effect of hydroxyapatite coating in vivo. The results of scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction showed that the hydroxyapatite was successfully deposited on the polyethylene terephthalate ligament. Water contact angle of the hydroxyapatite-polyethylene terephthalate group was significantly smaller than that of the polyethylene terephthalate group. The in vitro study showed that hydroxyapatite coating significantly improved adhesion and proliferation of MC3T3-E1 cells. The osteogenic differentiation of cells was also enhanced through the activation of ERK1/2 pathway. The micro-computed tomography, histological, and immunohistochemical results showed that biomineralization of hydroxyapatite significantly promoted new bone and fibrocartilage tissue formation at 12 weeks postoperatively. Moreover, the failure load and stiffness in the hydroxyapatite-polyethylene terephthalate group were higher than that in the polyethylene terephthalate group. Therefore, biomineralizaion of hydroxyapatite enhances the biocompatibility and osseointegration of the polyethylene terephthalate artificial ligament, thus promoting graft-bone healing for anterior cruciate ligament reconstruction through the activation of ERK1/2 pathway.

Suppressing inflammation and enhancing osteogenesis using novel CS-EC@Ca microcapsules

The aim of this study was to investigate the suppression of inflammation and enhancement of osteogenesis using chitosan-coated calcium hydroxide-loaded microcapsules (CS-EC@Ca microcapsules) in vivo. Circular defects were created in the mandibular bones of rabbits and filled with Ca(OH)₂ , Bio-oss, or CS-EC@Ca microcapsules, and rabbits without drug implantation served as the controls. Lipopolysaccharides were injected in situ daily in all groups for 7 days. Mandibular bones were investigated at 4 and 12 weeks after surgery using micro-CT, histological observations, and real-time PCR analysis. At the postoperation, there was more substantial nascent bone in the microcapsule and Bio-oss groups than in the control group. The recovery of the rabbits in the Ca(OH)₂ group was slower than the control group, as determined using micro-CT and histological staining. Osteocalcin and collagen type I production was not significantly different between the microcapsule and Bio-oss groups (p > 0.05), but the expression levels of the two molecules were significantly increased compared to the control and Ca(OH)₂ groups at postoperation (p < 0.05). The mRNA transcript levels of inflammatory factors in the microcapsule group had the most reduced expression of IL-6 and TNF-α (p < 0.05). The microcapsules significantly reduced inflammation and promoted osteogenesis in this rabbit model of inflammatory bone destruction. Our findings indicate that CS-EC@Ca microcapsules hold potential for use in apical periodontitis treatment. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3222-3230, 2018.

Repair of bone defects in rat radii with a composite of allogeneic adipose-derived stem cells and heterogeneous deproteinized bone

Background

In the bone tissue engineering domain, seed cells, scaffold and cell-scaffold composites are three focuses. In this study, the feasibility of using allogeneic adipose-derived stem cells(ADSCs) combined with heterogeneous deproteinized bone (HDB) to repair segmental radial defects was investigated by observing the repair of the defect area.

Methods

ADSCs were cultured in vitro, purified, antigen-detected and osteogenic differentiation potency-measured; then, the ADSCs of the third generation were seeded into HDB to prepare an ADSCs-HDB composite partly with osteogenesis induced cells. Sixty Wistar rats were randomly divided into four groups with 15 in each group. A bone defect (4 mm in length) was created at the left radius in each rat. Two kinds of ADSCs-HDB composites were implanted in the ADSCs osteogenesis group or ADSCs group; HDB was implanted in the negative control group; nothing was filled in the blank control group. The bone defect repair was evaluated by gross observation, molybdenum target X-ray examination and histological analyses after surgery.

Results

Gross observation: the bone defect area was completely filled and difficult to recognize in the ADSCs osteogenesis group. The connection of the ADSCs group was strong, but the implants were clearly identifiable. The joints of the negative control group were slightly thick but the connection was unstable. In the blank control group, kermesinus tissue was between the two ends and bones were not connected after 8 weeks. Molybdenum target X-ray examinations: In the ADSCs osteogenesis group, evident bridges in the graft were observed in the defects in the fourth week; the defects were filled with new bone completely and a marrow cavity appeared at 8 weeks. In the ADSCs group, there were some callus formations, but the radial defect was still obvious at 8 weeks. In the negative control group, fracture lines were clear. In the blank control group, no osseous bridges were observed, which resulted in bone nonunion eventually in 8 weeks. There were significant differences in the callus density between experimental groups and the blank control group at 4 and 8 weeks (P < 0.01). Histological measures showed that the rate and quality of the new bone formation and remodelling was significantly different between the experimental and control groups.

Conclusions

A composite of ADSCs-HDB has a strong osteogenic ability. It can repair segmental bone defects well and is promising to serve as grafting material in bone tissue engineering.

MAPK signaling has stage-dependent osteogenic effects on human adipose-derived stem cells in vitro

OVERVIEW

The use of pro-osteogenic growth factors, such as BMP2, in human adipose-derived stem cell (ASC) osteogenesis is well described. Because these growth factors work via signal transduction pathways, such as the mitogen-activated protein kinase (MAPK) cascade, a study of the relationship between MAPK signaling and ASC osteogenesis was conducted.

MATERIALS AND METHODS

ERK, JNK, and p38MAPK activation were measured in ASCs osteo-induced using either dexamethasone or vitamin D3 and correlated with mineralization. Activation and mineralization were also measured without dexamethasone or using the glucocorticoid, cortisone. The expression of the MAPK phosphatase, MKP1, and its relationship to mineralization was also assessed. The effect of decreasing MAPK activation on mineralization through the use of exogenous inhibitors was examined along with siRNA-knockdown and adenoviral overexpression of ERK1/2. Finally, the effect of ERK1/2 overexpression on ASCs induced on PLGA scaffolds was assessed.

RESULTS

ASC mineralization in dexamethasone or vitamin D3-induced ASCs correlated with both increased ERK1/2 and JNK1/2 activation. ASCs induced without dexamethasone also mineralized, with JNK1/2 signaling possibly mediating this event. No link between cortisone induction and MAPK signaling could be ascertained. ASCs treated with ERK, JNK, or p38MAPK inhibitors showed decreased osteogenic gene expression and diminished mineralization. Mineralization levels were also affected by viruses designed to inhibit or augment ERK1/2 expression and activity. Finally, ASC mineralization appeared to be a balance between the MAPK kinase activity and MKP1.

CONCLUSIONS

It is likely that MAPK signaling plays a significant role in ASC osteogenesis, affecting differentiation in kinase- and stage-specific manners.

Alveolar bone tissue engineering in critical-size defects of experimental animal models: a systematic review and meta-analysis

Regeneration of large, 'critical-size' bone defects remains a clinical challenge. Bone tissue engineering (BTE) is emerging as a promising alternative to autogenous, allogeneic and biomaterial-based bone grafting. The objective of this systematic review was to answer the focused question: in animal models, do cell-based BTE strategies enhance regeneration in alveolar bone critical-size defects (CSDs), compared with grafting with only biomaterial scaffolds or autogenous bone? Following PRISMA guidelines, electronic databases were searched for controlled animal studies reporting maxillary or mandibular CSD and implantation of mesenchymal stem cells (MSCs) or osteoblasts (OBs) seeded on biomaterial scaffolds. A random effects meta-analysis was performed for the outcome histomorphometric new bone formation (%NBF). Thirty-six studies were included that reported on large- (monkeys, dogs, sheep, minipigs) and small-animal (rabbits, rats) models. On average, studies presented with an unclear-to-high risk of bias and short observation times. In most studies, MSCs or OBs were used in combination with alloplastic mineral-phase scaffolds. In five studies, cells were modified by ex vivo gene transfer of bone morphogenetic proteins (BMPs). The meta-analysis indicated statistically significant benefits in favour of: (1) cell-loaded vs. cell-free scaffolds [weighted mean difference (WMD) 15.59-49.15% and 8.60-13.85% NBF in large- and small-animal models, respectively]; and (2) BMP-gene-modified vs. unmodified cells (WMD 10.06-20.83% NBF in small-animal models). Results of cell-loaded scaffolds vs. autogenous bone were inconclusive. Overall, heterogeneity in the meta-analysis was high (I2  > 90%). In summary, alveolar bone regeneration is enhanced by addition of osteogenic cells to biomaterial scaffolds. The direction and estimates of treatment effect are useful to predict therapeutic efficacy and guide future clinical trials of BTE. Copyright © 2016 John Wiley & Sons, Ltd.

A New Method for Xenogeneic Bone Graft Deproteinization: Comparative Study of Radius Defects in a Rabbit Model

Background and Objectives

Deproteinization is an indispensable process for the elimination of antigenicity in xenograft bones. However, the hydrogen peroxide (H₂O₂) deproteinized xenograft, which is commonly used to repair bone defect, exhibits limited osteoinduction activity. The present study was designed to develop a new method for deproteinization and compare the osteogenic capacities of new pepsin deproteinized xenograft bones with those of conventional H₂O₂ deproteinized ones.

Methods

Bones were deproteinized in H₂O₂ or pepsin for 8 hours. The morphologies were compared by HE staining. The content of protein and collagen I were measured by the Kjeldahl method and HPLC-MS, respectively. The physical properties were evaluated by SEM and mechanical tests. For in vivo study, X-ray, micro-CT and HE staining were employed to monitor the healing processes of radius defects in rabbit models transplanted with different graft materials.

Results

Compared with H₂O₂ deproteinized bones, no distinct morphological and physical changes were observed. However, pepsin deproteinized bones showed a lower protein content, and a higher collagen content were preserved. In vivo studies showed that pepsin deproteinized bones exhibited better osteogenic performance than H₂O₂ deproteinized bones, moreover, the quantity and quality of the newly formed bones were improved as indicated by micro-CT analysis. From the results of histological examination, the newly formed bones in the pepsin group were mature bones.

Conclusions

Pepsin deproteinized xenograft bones show advantages over conventional H₂O₂ deproteinized bones with respect to osteogenic capacity; this new method may hold potential clinical value in the development of new biomaterials for bone grafting.