Preparation of an injectable and photocurable carboxymethyl cellulose/hydroxyapatite composite and its application in cranial regeneration.

Limited bone regeneration, uncontrollable degradation rate, mismatched defect zone and poor operability have plagued the reconstruction of irregular bone defect by tissue-engineered materials. A combination of biomimetic scaffolds with hydroxyapatite has gained great popularity in promoting bone regeneration. Therefore, we designed an injectable, photocurable and in-situ curing hydrogel by methacrylic anhydride -modified carboxymethyl cellulose (CMC-MA) loading with spherical hydroxyapatite (HA) to highly simulate the natural bony matrix and match any shape of damaged tissue. The prepared carboxymethyl cellulose-methacrylate/ hydroxyapatite(CMC-MA/HA) composite presented good rheological behavior, swelling ratio and mechanical property under light illumination. Meanwhile, this composite hydrogel promoted effectively proliferation, supported adhesion and upregulated the osteogenic-related genes expression of MC3T3-E1 cells in vitro, as well as the activity of the osteogenic critical protein, Integrin α1, ß1, Myosin 9, Myosin 10, BMP-2 and Smad 1 in Integrin/BMP-2 signal pathway. Together, the composite hydrogels realized promotion of bone regeneration, deformity improvement, and the enhanced new bone strength in skull defect. It also displayed a good histocompatibility and stability of subcutaneous implantation in vivo. Overall, this study laid the groundwork for future research into developing a novel biomaterial and a minimally invasive therapeutic strategies for reconstructing bone defects and contour deficiencies.

Intratumor delivery of amino-modified graphene oxide as a multifunctional photothermal agent for efficient antitumor phototherapy.

Due to the high selectivity and non-invasive property, phototherapy has attracted increasing attention in the treatment of cancer. Targeted delivery and retention of photoactive agents in tumor tissue is of great significance and importance for safe and efficient phototherapy. Herein, we report a multifunctional nanomaterial photothermal agent, namely amino-modified graphene oxide (AGO) for anti-oral cancer photothermal therapy (PTT). Compared to the parental graphene oxide (GO) which has a negative charge and weak photothermal effect, AGO possesses a positive charge (∼+50 mV) and the significantly enhanced photothermal effect. Positive charge allows AGO to efficiently interact with tumor cells and retain in tumor tissue after intratumor injection. The enhanced photothermal effect allows AGO to achieve the tunable and efficient PTT. In vitro results show that AGO (15 µg/mL) reduces the viability of HSC-3 cells (oral squamous cell carcinoma cell line) to 5% under near infrared (NIR) irradiation (temperature increased to 58.4 °C). In vivo antitumor study shows that intratumor delivery of AGO (200 µg/mouse) has no inhibition effects on tumor growth (454% of initial tumor size) without NIR. With a single dose of NIR irradiation, however, AGO significantly reduces the tumor size to 25% of initial size in 1 of 4 mice, and even induces the complete tumor ablation in 3 of 4 mice. Furthermore, the injected AGO falls off along with the scab after PTT. Our findings indicate that AGO is a potential nano-photothermal agent for tunable, convenient and efficient anticancer PTT.

Effect of dental follicles in minimally invasive open-eruption technique of labially impacted maxillary central incisors.

OBJECTIVES: To summarize the open-eruption technique of impacted anterior maxillary teeth, this study reports a technically improved operation on surgical exposure based on dental follicles and evaluates post-treatment periodontal health considering the effect of dental follicles. METHODS: Patients who underwent open-eruption technique with unilateral labially impacted maxillary central incisors were selected. The impacted teeth were assigned to the experimental group, and the contralateral unimpacted maxillary central incisors were assigned to the control group. In the surgical exposure, the new technique makes use of dental follicles to manage the soft tissue, so as to preserve soft tissue for better aesthetic results and healthier periodontal tissue. Tooth length, root length, alveolar bone loss, and alveolar bone thickness were recorded after the therapy. RESULTS: A total of 17 patients with unilateral maxillary central incisor impaction were successfully treated. The tooth length and root length of the two groups showed a statistically significant difference between the impacted and homonym teeth, with a shorter length in the impacted tooth (P<0.05). More labial alveolar bone loss was found in the experimental group compared with that in the control group (P<0.05). The outcomes of the cementoenamel junction width, pa- latal alveolar bone loss, and alveolar bone thickness did not indicate statistical significance between the experimental and control groups (P>0.05). CONCLUSIONS: In the surgical exposure, the new technique uses dental follicles to manage the soft tissue and preserve it for better aesthetic results and healthier periodontal tissues.

Hypoxia inducible factor-1 signaling pathway in macrophage involved angiogenesis in materials-instructed osteo-induction.

Although osteo-inductive materials are regarded as promising candidates for critical-sized bone repair, their clinical application is limited by ambiguous mechanisms. The hypoxia-inducible factor (HIF)-1 signaling pathway, which responds to hypoxic conditions, is involved in both angiogenesis and osteogenesis. Strategies harnessing HIF-1 signaling to promote angiogenesis have been applied and have succeeded in repairing segmental bone defects. Meanwhile, macrophages have been shown to have important immunoregulatory effects on material-induced osteo-induction and correlate with HIF-1 activity. Thus, it is reasonable to assume that HIF-activated macrophages may also play important roles in the angiogenesis of material-induced osteo-induction. To verify this assumption, a classical type of osteo-inductive calcium phosphate (TCPs) was utilized. First, using RNA sequencing, we found that hypoxia activated the HIF signaling pathway in macrophages, which contributed to angiogenesis in TCPs. In addition, after treatment with a conditioned medium extracted from the co-culture system of macrophages and TCPs under hypoxic conditions, the migration and tube formation ability of human umbilical vein endothelial cells (HUVECs) significantly increased. In vivo, inhibition of HIF-1 or clearance of macrophages could result in impaired angiogenesis in TCPs. Finally, more blood vessels were formed in the TCPs group than in the control group. In conclusion, this study elucidated the vital role of the HIF signaling pathway in infiltrating macrophages during early vessel growth in material-induced osteo-induction. It is beneficial in advancing the exploration of the related mechanism and providing possible support for optimizing the applicability of osteo-inductive materials in bone repair.

Three-dimensional printed model of impacted third molar for surgical extraction training.

OBJECTIVES: Extraction of impacted mandibular third molars is one of the most common surgical procedures performed at dental clinics; however effective training models for teaching oral surgery to dental students are limited. This study aimed to use three-dimension (3D) printing technology to develop an effective training model for impacted third molar extraction. METHODS: The data for the 3D model were digitally processed using high-resolution computed tomography, and two common, but different patterns of impacted third molars were simulated using computer-aided design. Thereafter, the model was printed using the 3D-printing technology, and the efficiency of the 3D-printed model and an animal model (pig mandible) were compared using a five-point Likert scale by 35 oral surgeons in the oral surgery department and 208 students of stomatology in the internship stage. RESULTS: The 3D-printed model consisted of three parts: a non-replaceable part (i.e., the body of the mandible and the teeth from the left first molar to the right first molar) and two replaceable parts (i.e., the part of the ascending ramus of the mandible, as well as the second and third molars). It was covered with a layer of rubber-like material to simulate the gingiva. For the comparison between the 3D-printed and animal models, a total of 205 questionnaires were collected. Both oral surgeons and students agreed that the 3D-printed model was better than the animal model in terms of total value and the anatomy of the bone and teeth, simulating the surgical procedure (p < 0.05), while the two models achieved similar results for haptic feedback of the soft tissue (p > 0.05). CONCLUSIONS: The 3D-printed model is realistic and effective for learning impacted third molar extraction and received positive feedback from students and oral surgeons. This model can significantly improve the pre-clinical skill training of dental students.

An injectable and antibacterial calcium phosphate scaffold inhibiting Staphylococcus aureus and supporting stem cells for bone regeneration.

Staphylococcus aureus (S. aureus) is the major pathogen for osteomyelitis, which can lead to bone necrosis and destruction. There has been no report on antibacterial calcium phosphate cement (CPC) against S. aureus. The aims of this study were to: (1) develop novel antibacterial CPC-chitosan-alginate microbead scaffold; (2) investigate mechanical and antibacterial properties of CPC-chitosan-penicillin-alginate scaffold; (3) evaluate the encapsulation and delivery of human umbilical cord mesenchymal stem cells (hUCMSCs). Flexural strength, elastic modulus and work-of-fracture of the CPC-chitosan-penicillin-alginate microbeads scaffold and CPC-chitosan scaffold were evaluated. Penicillin release profile and antibacterial effects on S. aureus were determined. The hUCMSC delivery and release from penicillin-alginate microbeads were investigated. Injectable CPC-chitosan-penicillin-alginate microbeads scaffold was developed for the first time. CPC-chitosan-penicillin-alginate microbeads scaffold had a flexural strength of 3.16 ± 0.55 MPa, matching that of cancellous bone. With sustained penicillin release, the new scaffold had strong antibacterial effects on S. aureus, with an inhibition zone diameter of 32.2 ± 2.5 mm, greater than that of penicillin disk control (15.1 ± 2.0 mm) (p < 0.05). Furthermore, this injectable and antibacterial scaffold had no toxic effects, yielding excellent hUCMSC viability, which was similar to that of CPC control without antibacterial activity (p > 0.05). CPC-chitosan-penicillin-microbeads scaffold had injectability, good strength, strong antibacterial effects, and good biocompatibility to support stem cell viability for osteogenesis. CPC-chitosan-penicillin-microbeads scaffold is promising for dental, craniofacial and orthopedic applications to combat infections and promote bone regeneration.

Controlled Delivery of Growth Factor by Hierarchical Nanostructured Core-Shell Nanofibers for the Efficient Repair of Critical-Sized Rat Calvarial Defect.

Electrospun nanofibers have received much attention as bone tissue-engineered scaffolds for their capacity to mimic the structure of natural extracellular matrix (ECM). Most studies have reproduced nanofibers with smooth surface for tissue engineering. This is quite different from the triple-helical nanotopography of natural collagen nanofibrils. In this study, hierarchical nanostructures were coated on the surface of drug-loaded core-shell nanofibers to mimic natural collagen nanofibrils. The nanoshish-kebab (SK) structure was decorated regularly on the surface of the nanofibers, and the inner-loaded bone morphogenetic protein 2 (BMP2) exhibited a gentle release pattern, similar to a zero-order release pattern in kinetics. The in vitro study also showed that the SK structure could accelerate cell proliferation, attachment, and osteogenic differentiation. Four groups of scaffolds were implanted in vivo to repair critical-sized rat calvarial defects: (1) PCL/PVA (control); (2) SK-PCL/PVA; (3) PCL/PVA-BMP2; and (4) SK-PCL/PVA-BMP2. Much more bone was formed in the SK-PCL/PVA group (24.57 ± 3.81%) than in the control group (1.21 ± 0.23%). The BMP2-loaded core-shell nanofibers with nanopatterned structure (SK-PCL/PVA-BMP2) displayed the best repair efficacy (76.38 ± 4.13%), followed by the PCL/PVA-BMP2 group (39.86 ± 5.74%). It was believed that the hierarchical nanostructured core-shell nanofibers could promote osteogeneration and that the SK structure showed synergistic ability with nanofiber-loaded BMP2 in vivo for bone regeneration. Thus, this BMP2-loaded core-shell nanofiber scaffold with hierarchical nanostructure holds great potential for bone tissue engineering applications.

The Emerging Roles of Long Noncoding RNAs in Bone Homeostasis and Their Potential Application in Bone-Related Diseases.

Increasing evidence has announced the emerging roles of long noncoding RNAs (lncRNAs) in modulating bone homeostasis due to their potential regulating effects on bone-related cells' proliferation, migration, differentiation and apoptosis. Thus, lncRNAs have been considered as a promising gene tool to facilitate the bone regeneration process and then to predict and cure bone-related diseases such as osteosarcoma, osteoporosis, and osteoarthritis. In this review, we first enumerated several kinds of dysregulated lncRNAs and concisely summarized their regulating role in bone formation as well as resorption process. The related mechanisms were also discussed, respectively. Then, the positive or negative behavior of these lncRNAs in bone-related diseases was elucidated. This review provides an in-depth sight about the lncRNA's clinical values and limitations, which is conducive to explore new gene targets and further establish new therapeutic strategies for bone-related disease.

Macrophage polarization plays roles in bone formation instructed by calcium phosphate ceramics.

To investigate the roles of macrophages in material-instructed bone formation, two calcium phosphate (TCP) ceramics with the same chemistry but various scales of surface topography were employed in this study. After being implanted subcutaneously in FVB mice for 8 weeks, TCPs (TCP ceramics with submicron surface topography) gave rise to bone formation, while TCPb (TCP ceramics with micron surface topography) did not, showing the crucial role of surface topography scale in material-instructed bone formation. Depletion of macrophages with liposomal clodronate (LipClod) blocked such bone formation instructed by TCPs, confirming the role of macrophages in material-instructed bone formation. Macrophage cells (i.e. RAW 264.7 cells) cultured on TCPs in vitro polarized to tissue repair macrophages as evidenced by gene expression and cytokine production, while polarizing to pro-inflammatory macrophages on TCPb. Submicron surface topography of TCP ceramics directed macrophage polarization via PI3K/AKT pathways with the synergistic regulation of integrin ß1. Finally, the tissue repair macrophage polarization on TCPs resulted in osteogenic differentiation of mesenchymal stem cells in vitro. At early implantation in FVB mice, TCPs recruited more macrophages which polarized towards tissue repair macrophages with time. The present data demonstrate the important roles of macrophage polarization in bone formation instructed by calcium phosphate ceramics.

Experimental and simulation studies of strontium/fluoride-codoped hydroxyapatite nanoparticles with osteogenic and antibacterial activities.

Multiple ions codoping may effectively modulate physicochemical and biological properties of hydroxyapatite (HA) for diverse biomedical applications. This study synthesized strontium (Sr)-, fluorine (F)- doped, and Sr/F-codoped HA nanoparticles by a hydrothermal method, and investigated the effect of ion doping on characteristics of HA, including crystallinity, crystal size, lattice parameters, and substitution sites by experiments and simulation with density functional theory (DFT) methods. It was found that, Sr doping increased the lattice parameters of HA whereas F doping decreased these parameters. Additionally, F doping enhanced the structural stability of the Sr-doped HA. F doping created excellent antibacterial properties to effectively inhibit growth of Streptococcus mutans. An appropriate Sr doping level endowed HA with optimum osteogenic ability to promote osteoblastic differentiation of bone marrow stem cells. These suggest that, Sr/F codoping is an effective approach to synthesizing HA-based materials with both antibacterial and osteogenic properties. More broadly, HA nanomaterials with specific characteristics may be designed for meeting diverse requirements from biomedical applications.

[A review of peri-implant microbiology].

Dental implants represent the majority of treatment strategies used to replace missing teeth. However, peri-implant diseases caused by disturbance in peri-implant microbiological balance are among the reasons for implant failure. Since the 1980s, peri-implant microorganisms have been a hot research topic in dental microbiology. The bacterial ecology between the disease and health largely differs, which directly or indirectly increases the risk of peri-implant diseases. Accordingly, the determination of the 'core microbiome' of peri-implantitis and peri-implant mucositis is a key point of recent research.

[Research progress in the mechanism of protein factors in regulating bone remodeling].

Objective: To review the role and mechanism of protein factors in bone remodeling, and provides theoretical basis for further elucidating the pathogenesis and clinical treatment of bone-related diseases. Methods: The relevant research results at home and abroad in recent years were extensively consulted, analyzed, and summarized. Results: Bone remodeling is an important physiological process to maintain bone homeostasis. Protein, as an important stimulator in bone remodeling, regulates the balance between bone resorption and bone formation. Conclusion: At present, the research on the mechanism of protein in bone remodeling is insufficient. Therefore, it is necessary to further study the specific time, process, and interaction network of protein in bone remodeling, and to confirm its mechanism in bone remodeling, so as to reveal and treat the pathogenesis of bone-related diseases.

Angiogenic and osteogenic regeneration in rats via calcium phosphate scaffold and endothelial cell co-culture with human bone marrow mesenchymal stem cells (MSCs), human umbilical cord MSCs, human induced pluripotent stem cell-derived MSCs and human embryonic stem cell-derived MSCs.

Angiogenesis is a limiting factor in regenerating large bone defects. The objective of this study was to investigate angiogenic and osteogenic effects of co-culture on calcium phosphate cement (CPC) scaffold using human umbilical vein endothelial cells (hUVECs) and mesenchymal stem cells (MSCs) from different origins for the first time. hUVECs were co-cultured with four types of cell: human umbilical cord MSCs (hUCMSCs), human bone marrow MSCs (hBMSCs) and MSCs from induced pluripotent stem cells (hiPSC-MSCs) and embryonic stem cells (hESC-MSCs). Constructs were implanted in 8 mm cranial defects of rats for 12 weeks. CPC without cells served as control 1. CPC with hBMSCs served as control 2. Microcapillary-like structures were successfully formed on CPC in vitro in all four co-cultured groups. Microcapillary lengths increased with time (p < 0.05). Osteogenic and angiogenic gene expressions were highly elevated and mineralization by co-cultured cells increased with time (p < 0.05). New bone amount and blood vessel density of co-cultured groups were much greater than controls (p < 0.05) in an animal study. hUVECs co-cultured with hUCMSCs, hiPSC-MSCs and hESC-MSCs achieved new bone and vessel density similar to hUVECs co-cultured with hBMSCs (p > 0.1). Therefore, hUCMSCs, hiPSC-MSCs and hESC-MSCs could serve as alternative cell sources to hBMSCs, which require an invasive procedure to harvest. In conclusion, this study showed for the first time that co-cultures of hUVECs with hUCMSCs, hiPSC-MSCs, hESC-MSCs and hBMSCs delivered via CPC scaffold achieved excellent osteogenic and angiogenic capabilities in vivo. The novel co-culture constructs are promising for bone reconstruction with improved angiogenesis for craniofacial/orthopaedic applications. Copyright © 2017 John Wiley & Sons, Ltd.

Application of Bidirectional Distraction Osteogenesis for the Treatment of Mandibular Micriognathia Caused by Temporomandibular Joint Ankylosis.

BACKGROUND: Temporomandibular joint (TMJ) ankylosis is a joint disorder that refers to bone or fibrous adhesion of the anatomic joint components and the ensuing loss of function. When it happens on children, it is always accompanied by dentofacial deformities. The objective of this study was to describe the authors' experience of bidirectional distraction osteogenesis for the treatment of mandibular deformities caused by TMJ ankylosis. METHODS: Sixteen patients with TMJ ankylosis and severe secondary mandibular deformities were treated with bidirectional distraction osteogenesis and release of joint from January 2013 to December 2015. Clinical outcomes were assessed based on the oral function, radiography, and medical photography. RESULTS: No reankylosis was found during the follow-up period. Sufficient volume and density new bone had been formed after the consolidation period. All patients have maintained stable improvement in oral function during the follow-up period. Most of the patients achieved satisfactory outcomes. CONCLUSIONS: Bidirectional transport distraction osteogenesis technique is a good and effective therapeutic option in treatment of bilateral or unilateral TMJ ankylosis patients associated with mandibular micrognathia.

Impact of Implant Surface Micropatterns on Epithelial Cell Behavior.

PURPOSE: This study investigated the effect of topography on cell behavior by screening polydimethylsiloxane (PDMS) molds with different nanoscale micropatterns to determine the ideal surface characteristics for attachment of human epithelial cells. MATERIALS AND METHODS: A soft PDMS mold with regular dot arrays was fabricated based on an aluminum oxide template with ordered nanotube arrays and used as a substrate for cell culture. Cell proliferation, spread, and morphology, as well as features of the extracellular matrix and the actin cytoskeleton were assessed. DISCUSSION: Cells grown on 100-nm regular dot arrays had the highest proliferation rate and spread, with the longest pseudopodia; they showed robust actin distribution relative to the control group. CONCLUSION: Three-dimensional PDMS microstructures with 100 nm regular dot arrays were the most effective surface for epithelial cell attachment. These findings can aid in the manufacture of superior materials for use in implants to better integrate into recipient tissue.

Novel hiPSC-based tri-culture for pre-vascularization of calcium phosphate scaffold to enhance bone and vessel formation.

Vascularization of tissue-engineered bone is a critical step in maintaining cell viability and advancing cell performance in vivo. In this study, a novel tri-culture system was developed to elicit pre-vascularization of calcium phosphate cement (CPC) scaffold in which human induced pluripotent stem cell-derived mesenchymal stem cells (hiPSMSCs) were seeded together with human umbilical vein endothelial cells (HUVECs) and pericytes. In a two-step methodology design, we first performed osteoinduction of the seeded hiPSMSCs on the CPC scaffold and then incorporated HUVECs and pericytes to the hiPSMSC-colonized CPC scaffold under a favorable culturing condition, with an objective to form a stable and functional capillary-like vascular network that sustained the engineered osseous tissue. The angiogenic and osteogenic effects of various culture strategies were studied and compared in nude rat model with cranial bone defects: (1) CPC scaffold alone (CPC control); (2) Pericyte-seeded CPC (CPC-pericytes); (3) HUVEC-seeded CPC (CPC-HUVECs); (4) hiPSMSC-seeded CPC (CPC-hiPSMSCs); (5) HUVECs co-cultured with hiPSMSCs on CPC (bi-culture group) and (6) HUVECs and pericytes co-cultured with hiPSMSCs on CPC (tri-culture group). After 12weeks, tri-culture group showed the highest amount of new bone (new bone area fraction of (45.3±2.7) %, p<0.05) and vessel formation (new blood vessel density of (50.7±3.8) vessels/mm2, p<0.05) in all groups. Our results demonstrated that the tri-culture strategy was effective in promoting angiogenesis and osteogenesis for bone tissue engineering.

Preparation and Evaluations of Mangiferin-Loaded PLGA Scaffolds for Alveolar Bone Repair Treatment Under the Diabetic Condition.

The aim of the present study was to prepare and evaluate a sustained-release mangiferin scaffold for improving alveolar bone defect repair in diabetes. Mangiferin-loaded poly(D,L-lactide-co-glycolide) (PLGA) scaffolds were prepared using a freeze-drying technique with ice particles as the porogen material. The produced scaffolds were examined using a scanning electron microscope (SEM). Drug content and drug release were detected using a spectrophotometer. Degradation behaviors were monitored as a measure of weight loss and examined using SEM. Then, the scaffolds were incubated with rat bone marrow stromal cells under the diabetic condition in vitro, and cell viability was assessed using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Afterward, the scaffolds were implanted into alveolar bone defects of diabetic rats, and bone repair was examined using hematoxylin and eosin staining. The fabricated scaffolds showed porous structures, with average pore size range from 111.35 to 169.45 µm. A higher PLGA concentration led to decreased average pore size. A lower PLGA concentration or a higher mangiferin concentration resulted in increased drug content. The prepared scaffolds released mangiferin in a sustained manner with relatively low initial burst during 10 weeks. Their degradation ratios gradually increased as degradation proceeded. The mangiferin-loaded scaffolds attenuated cell viability decrease under the diabetic condition in vitro. Moreover, they increased histological scorings of bone regeneration and improved delayed alveolar bone defect healing in diabetic rats. These results suggest that the produced mangiferin-loaded scaffolds may provide a potential approach in the treatment of impaired alveolar bone healing in diabetes.

Screening the Expression Changes in MicroRNAs and Their Target Genes in Mature Cementoblasts Stimulated with Cyclic Tensile Stress.

Cementum is a thin layer of cementoblast-produced mineralized tissue covering the root surfaces of teeth. Mechanical forces, which are produced during masticatory activity, play a paramount role in stimulating cementoblastogenesis, which thereby facilitates the maintenance, remodeling and integrity of cementum. However, hitherto, the extent to which a post-transcriptional modulation mechanism is involved in this process has rarely been reported. In this study, a mature murine cementoblast cell line OCCM-30 cells (immortalized osteocalcin positive cementoblasts) was cultured and subjected to cyclic tensile stress (0.5 Hz, 2000 µstrain). We showed that the cyclic tensile stress could not only rearrange the cell alignment, but also influence the proliferation in an S-shaped manner. Furthermore, cyclic tensile stress could significantly promote cementoblastogenesis-related genes, proteins and mineralized nodules. From the miRNA array analyses, we found that 60 and 103 miRNAs were significantly altered 6 and 18 h after the stimulation using cyclic tensile stress, respectively. Based on a literature review and bioinformatics analyses, we found that miR-146b-5p and its target gene Smad4 play an important role in this procedure. The upregulation of miR-146b-5p and downregulation of Smad4 induced by the tensile stress were further confirmed by qRT-PCR. The direct binding of miR-146b-5p to the three prime untranslated region (3' UTR) of Smad4 was established using a dual-luciferase reporter assay. Taken together, these results suggest an important involvement of miR-146b-5p and its target gene Smad4 in the cementoblastogenesis of mature cementoblasts.

Independent effects of the chemical and microstructural surface properties of polymer/ceramic composites on proliferation and osteogenic differentiation of human MSCs.

UNLABELLED: Within the general aim of finding affordable and sustainable regenerative solutions for damaged and diseased tissues and organs, significant efforts have been invested in developing synthetic alternatives to natural bone grafts, such as autografts. Calcium phosphate (CaP) ceramics are among widely used synthetic bone graft substitutes, but their mechanical properties and bone regenerative capacity are still outperformed by their natural counterparts. In order to improve the existing synthetic bone graft substitutes, it is imperative to understand the effects of their individual properties on a biological response, and to find a way to combine the desired properties into new, improved functional biomaterials. To this end, we studied the independent effects of the chemical composition and surface microstructure of a poly(lactic acid)/hydroxyapatite (PLA/HA) composite material on the proliferation and osteogenic differentiation of clinically relevant bone marrow-derived human mesenchymal stromal cells (hMSCs). While the molecular weight of the polymer and presence/absence of the ceramic phase were used as the chemical variables, a soft embossing technique was used to pattern the surfaces of all materials with either pits or pillars with identical microscale dimensions. The results indicated that, while cell morphology was affected by both the presence and availability of HA and by the surface microstructure, the effect of the latter parameter on cell proliferation was negligible. The osteogenic differentiation of hMSCs, and in particular the expression of bone morphogenetic protein 2 (BMP-2) and osteopontin (OP) were significantly enhanced when cells were cultured on the composite based on low-molecular-weight PLA, as compared to the high-molecular-weight PLA-based composite and the two pure polymers. The OP expression on the low-molecular-weight PLA-based composite was further enhanced when the surface was patterned with pits. Taken together, within this experimental set up, the individual effect of the chemistry, and in particular of the presence of CaP, was more pronounced than the individual effect of the surface microstructure, although their combined effects were, in some cases, synergistic. The approach presented here opens new routes to study the interactions of biomaterials with the biological environment in greater depths, which can serve as a starting point for developing biomaterials with improved bioactivity. STATEMENT OF SIGNIFICANCE: The aim of the this study was to obtain insight into independent effects of the chemical composition and surface microstructure of a poly(lactic acid)/hydroxyapatite (PLA/HA) composite material on the morphology, proliferation and osteogenic differentiation of clinically relevant bone marrow-derived human mesenchymal stromal cells (hMSCs). While the need for synthetic alternatives for natural bone in bone regenerative strategies is rapidly increasing, the clinical performance of synthetic biomaterials needs to be further improved. To do this successfully, we believe that a better understanding of the relationship between a property of a material and a biological response is imperative. This study is a step forward in this direction, and we are therefore convinced that it will be of interest to the readers of Acta Biomaterialia.

Osteoprotegerin gene-modified BMSCs with hydroxyapatite scaffold for treating critical-sized mandibular defects in ovariectomized osteoporotic rats.

UNLABELLED: Women with postmenopausal osteoporosis are at a high risk for fracture as their bone resorption rate exceeds bone formation rate, resulting in decreased bone mineral density and microarchitectural deterioration. Osteoprotegerin (OPG), a known therapeutic agent capable of inhibiting osteoclastogenesis, has been used in treatment of chronic bone resorptive diseases. On the other hand, bone mesenchymal stem cells (BMSCs) play an important role in bone formation. To inhibit excessive bone resorption and increase bone formation, we developed a novel therapeutic strategy by genetically modifying BMSCs for OPG delivery. The OPG gene-modified BMSCs were seeded on hydroxyapatite (HA) scaffolds to promote bone regeneration in critical-sized mandibular bone defects in ovariectomy (OVX) induced osteoporotic rats. Rat BMSCs were infected with human OPG adenoviruses (OPG-BMSCs). The gene-modified cells expressed higher OPG gene level than the control Ad-BMSCs (p<0.05) and maintained high expression of OPG protein for more than 2weeks. Our in vitro bone resorption experiment demonstrated that OPG-BMSCs were capable to suppress osteoclast differentiation and subsequently inhibit osteoclast-mediated bone resorption. The micro-CT and histological results showed that HA-OPG-BMSC constructs boosted bone formation and reduced osteoclastogenesis in OVX rat mandibular bone defects. In conclusion, the novel OPG-BMSC-HA constructs were demonstrated to be able to orchestrate bone-forming BMSCs and bone-resorbing osteoclasts, with the potential for osteoporotic-related bone defect reconstruction applications. STATEMENT OF SIGNIFICANCE: Women with postmenopausal osteoporosis are at a high risk for fracture as their bone resorption rate exceeds bone formation rate. Osteoprotegerin (OPG), a known therapeutic agent capable of inhibiting osteoclast cells, has been used in treatment of chronic bone resorptive diseases. To inhibit excessive bone resorption and increase bone formation, we developed a novel therapeutic strategy by genetically modifying bone marrow stem cells (BMSCs) for OPG delivery and seeding the cells on a hydroxyapatite (HA) scaffold for in vivo bone defect repair. The novel OPG-BMSC-HA constructs were able to orchestrate bone-forming BMSCs and bone-resorbing osteoclasts, demonstrating good potential for osteoporosis-related bone defect reconstruction treatments.