Osteogenic differentiation of mesenchymal stem cells in biodegradable sponges composed of gelatin and β-tricalcium phosphate

Fabrication of vascularized tissue-engineered bone models using triaxial bioprinting

Bone tissue is a highly vascularized tissue. When constructing tissue-engineered bone models, both the osteogenic and angiogenic capabilities of the construct should be carefully considered. However, fabricating a vascularized tissue-engineered bone to promote vascular formation and bone generation, while simultaneously establishing nutrition channels to facilitate nutrient exchange within the constructs, remains a significant challenge. Triaxial bioprinting, which not only allows the independent encapsulation of different cell types while simultaneously forming nutrient channels, could potentially emerge as a strategy for fabricating vascularized tissue-engineered bone. Moreover, bioinks should also be applied in combination to promote both osteogenesis and angiogenesis. In this study, employing triaxial bioprinting, we used a blend bioink of gelatin methacryloyl (GelMA), sodium alginate (Alg), and different concentrations of nano beta-tricalcium phosphate (nano β-TCP) encapsulated MC3T3-E1 preosteoblasts as the outer layer, a mixed bioink of GelMA and Alg loaded with human umbilical vein endothelial cells (HUVEC) as the middle layer, and gelatin as a sacrificial material to form nutrient channels in the inner layer to fabricate vascularized bone constructs simulating the microenvironment for bone and vascular tissues. The results showed that the addition of nano β-TCP could adjust the mechanical, swelling, and degradation properties of the constructs. Biological assessments revealed the cell viability of constructs containing different concentrations of nano β-TCP was higher than 90% on day 7, The cell-laden constructs containing 3% (w/v) nano β-TCP exhibited better osteogenic (higher Alkaline phosphatase activity and larger Osteocalcin positive area) and angiogenic (the gradual increased CD31 positive area) potential. Therefore, using triaxial bioprinting technology and employing GelMA, Alg, and nano β-TCP as bioink components could fabricate vascularized bone tissue constructs, offering a novel strategy for vascularized bone tissue engineering.

3D printed polycaprolactone/β-tricalcium phosphate/carbon nanotube composite - Physical properties and biocompatibility

Three-dimensional (3D) printing is a bio-fabrication technique used to process tissue-engineered scaffolds for bone repair and remodeling. Polycaprolactone (PCL)/β-tricalcium phosphate (TCP) has been used as a base and osteoconductive biomaterial for bone tissue engineering in the past decades. The current study reveals the fabrication of a polycaprolactone (PCL)/β-tricalcium phosphate (TCP) scaffold by incorporating carbon nanotubes (CNT) via 3D printing. The physical properties and cytocompatibility of a new type of tissue engineering composite from polycaprolactone/β-tri-calcium phosphate/carbon nanotubes were investigated, and it was an absorbable scaffold prepared via furnace deposition 3D printing technology. The scaffold was designed with CAD software, and the composite material was fabricated via 3D printing. The printed composite material was tested for mechanical strength, scanning electron microscope (SEM) analysis, porosity calculation, systemic toxicity test, hemolysis rate determination, and effect on the proliferation of rat adipose-derived stem cells cultured in vitro. A composite scaffold with a length of 15 mm, width of 10 mm, and height of 5 mm was manufactured through CAD software drawing and 3D printing technology. Scanning electron microscopy measurements and analysis of the internal pore size of the stent are appropriate; the pores are interconnected, and the mechanical strength matches the strength of human cancellous bone. The calculated porosity of the stent was >60%, non-toxic, and non-hemolytic. The proliferation activity of the ADSC co-cultured with different scaffold materials was as follows: polycaprolactone/β-tricalcium phosphate/0.2% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate/0.1% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate/0.3% carbon nanotube scaffolds > polycaprolactone/β-tricalcium phosphate scaffolds (P < 0.05). The results showed that polycaprolactone/β-tricalcium phosphate/0.2% carbon nanotube scaffolds promoted the adhesion and proliferation of ADSC. The combination of 3D printing technology and CAD software can be used to print personalized composite stents, which have the characteristics of repeatability, high precision, and low cost. Through 3D printing technology, combining a variety of materials with each other can provide the greatest advantages of materials. The waste of resources was avoided. The prepared polycaprolactone/β-tri-calcium phosphate/0.2% carbon nanotube scaffold has a good pore structure and mechanical properties that mimic human cancellous bone, is non-toxic and non-hemolytic, and is effective in promoting ADSC proliferation in vitro. Given this correspondence, 3D printed scaffold shows good biocompatibility and strength, and the fabrication method provides a proof of concept for developing scaffolds for bone tissue engineering applications.

Bone-Regeneration Therapy Using Biodegradable Scaffolds: Calcium Phosphate Bioceramics and Biodegradable Polymers

Calcium phosphate-based synthetic bone is broadly used for the clinical treatment of bone defects caused by trauma and bone tumors. Synthetic bone is easy to use; however, its effects depend on the size and location of the bone defect. Many alternative treatment options are available, such as joint arthroplasty, autologous bone grafting, and allogeneic bone grafting. Although various biodegradable polymers are also being developed as synthetic bone material in scaffolds for regenerative medicine, the clinical application of commercial synthetic bone products with comparable performance to that of calcium phosphate bioceramics have yet to be realized. This review discusses the status quo of bone-regeneration therapy using artificial bone composed of calcium phosphate bioceramics such as β-tricalcium phosphate (βTCP), carbonate apatite, and hydroxyapatite (HA), in addition to the recent use of calcium phosphate bioceramics, biodegradable polymers, and their composites. New research has introduced potential materials such as octacalcium phosphate (OCP), biologically derived polymers, and synthetic biodegradable polymers. The performance of artificial bone is intricately related to conditions such as the intrinsic material, degradability, composite materials, manufacturing method, structure, and signaling molecules such as growth factors and cells. The development of new scaffold materials may offer more efficient bone regeneration.

Attributes of Nanomaterials and Nanotopographies for Improved Bone Tissue Engineering and Regeneration

Bone tissue engineering (BTE) is a multidisciplinary area that can solve the limitation of conventional grafting methods by developing viable and biocompatible bone replacements. The three essential components of BTE, i.e., Scaffold material and Cells and Growth factors altogether, facilitate support and guide for bone formation, differentiation of the bone tissues, and enhancement in the cellular activities and bone regeneration. However, there is a scarcity of the appropriate materials that can match the mechanical property as well as functional similarity to native tissue, considering the bone as hard tissue. In such scenarios, nanotechnology can be leveraged upon to achieve the desired aspects of BTE, and that is the key point of this review article. This review article examines the significant areas of nanotechnology research that have an impact on regeneration of bone: (a) scaffold with nanomaterials helps to enhance physicochemical interactions, biocompatibility, mechanical stability, and attachment; (b) nanoparticle-based approaches for delivering bioactive chemicals, growth factors, and genetic material. The article begins with the introduction of components and healing mechanisms of bone and the factors associated with them. The focus of this article is on the various nanotopographies that are now being used in scaffold formation, by describing how they are made, and how these nanotopographies affect the immune system and potential underlying mechanisms. The advantages of 4D bioprinting in BTE by using nanoink have also been mentioned. Additionally, we have investigated the importance of an in silico approach for finding the interaction between drugs and their related receptors, which can help to formulate suitable systems for delivery. This review emphasizes the role of nanoscale approach and how it helps to increase the efficacy of parameters of scaffold as well as drug delivery system for tissue engineering and bone regeneration.

Research Progress of Design Drugs and Composite Biomaterials in Bone Tissue Engineering

Bone, like most organs, has the ability to heal naturally and can be repaired slowly when it is slightly injured. However, in the case of bone defects caused by diseases or large shocks, surgical intervention and treatment of bone substitutes are needed, and drugs are actively matched to promote osteogenesis or prevent infection. Oral administration or injection for systemic therapy is a common way of administration in clinic, although it is not suitable for the long treatment cycle of bone tissue, and the drugs cannot exert the greatest effect or even produce toxic and side effects. In order to solve this problem, the structure or carrier simulating natural bone tissue is constructed to control the loading or release of the preparation with osteogenic potential, thus accelerating the repair of bone defect. Bioactive materials provide potential advantages for bone tissue regeneration, such as physical support, cell coverage and growth factors. In this review, we discuss the application of bone scaffolds with different structural characteristics made of polymers, ceramics and other composite materials in bone regeneration engineering and drug release, and look forward to its prospect.

Review of Plasma Processing for Polymers and Bio-Materials Using a Commercial Frequency (50/60 Hz)-Generated Discharge

This manuscript introduces the properties and diverse applications of plasma generated using commercial frequencies of 50/60 Hz. Commercial frequency (CF) derived plasma exhibits characteristics similar to DC discharge but with an electrical polarity and a non-continuous discharge. Due to the low-frequency nature, the reactor configurations usually are capacitively coupled plasma type. The advantages of this method include its simple power structure, low-reaction temperature, and low substrate damage. The electrical polarity can prevent charge buildup on the substrates and deposited films, thereby reducing substrate damage. The simple, low-cost, and easy-to-operate power structure makes it suitable for laboratory-scale usage. Additionally, the various applications, including plasma-enhanced vapor deposition, sputtering, dielectric barrier discharge, and surface modification, and their outcomes in the CF-derived plasma processes are summarized. The conclusion drawn is that the CF-derived plasma process is useful for laboratory-scale utilization due to its simplicity, and the results of the plasma process are also outstanding.

Assessing Biomaterial-Induced Stem Cell Lineage Fate by Machine Learning-Based Artificial Intelligence

Current functional assessment of biomaterial-induced stem cell lineage fate in vitro mainly relies on biomarker-dependent methods with limited accuracy and efficiency. Here a "Mesenchymal stem cell Differentiation Prediction (MeD-P)" framework for biomaterial-induced cell lineage fate prediction is reported. MeD-P contains a cell-type-specific gene expression profile as a reference by integrating public RNA-seq data related to tri-lineage differentiation (osteogenesis, chondrogenesis, and adipogenesis) of human mesenchymal stem cells (hMSCs) and a predictive model for classifying hMSCs differentiation lineages using the k-nearest neighbors (kNN) strategy. It is shown that MeD-P exhibits an overall accuracy of 90.63% on testing datasets, which is significantly higher than the model constructed based on canonical marker genes (80.21%). Moreover, evaluations of multiple biomaterials show that MeD-P provides accurate prediction of lineage fate on different types of biomaterials as early as the first week of hMSCs culture. In summary, it is demonstrated that MeD-P is an efficient and accurate strategy for stem cell lineage fate prediction and preliminary biomaterial functional evaluation.

Properties of Coatings Based on Calcium Phosphate and Their Effect on Cytocompatibility and Bioactivity of Titanium Nickelide

Coatings based on calcium phosphate with thicknesses of 0.5 and 2 μm were obtained by high-frequency magnetron sputtering on NiTi substrates in an argon atmosphere. The coating was characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, and in vitro cytocompatibility and bioactivity studies. A biphasic coating of tricalcium phosphate (Ca₃(PO₄)₂) and hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) with a 100% degree of crystallinity was formed on the surface. The layer enriched in calcium, phosphorus, and oxygen was observed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Scanning electron microscopy showed that the surface structure is homogeneous without visible defects. The 2 µm thick coating obtained by sputtering with a deposition time of 4 h and a deposition rate of 0.43 µm/h is uniform, contains the highest amount of the calcium phosphate phase, and is most suitable for the faster growth of cells and accelerated formation of apatite layers. Samples with calcium phosphate coatings do not cause hemolysis and have a low cytotoxicity index. The results of immersion in a solution simulating body fluid show that NiTi with the biphasic coating promotes apatite growth, which is beneficial for biological activity.

Osteogenic Differentiation of Canine Adipose Derived Mesenchymal Stem Cells on B-TCP and B-TCP/Collagen Biomaterials

Mesenchymal stem cells are adult stem cells that have the ability to differentiate into osteogenic, chondrogenic, adipogenic and myogenic lineages. In the field of orthopedics and traumatology, mesenchymal stem cells in combination with biomaterials are used especially for the treatment of bone fractures and diseases in both humans and animals. The purpose of this study is to promote growth, proliferation and osteogenic differentiation of mesenchymal stem cells that were isolated from the adipose tissue of canines on B-TCP (Beta-tricalcium phosphate) and B-TCP/Collagen biomaterials. MTT analysis was performed to test the cell adhesion and proliferation on B-TCP and B-TCP/Collagen biomaterials that were used to mimic the extracellular matrix of three-dimensional bone tissue. Scanning electron microscope analysis was performed to show general surface characters of B-TCP and B-TCP /Collagen biomaterials. The osteoinductive capacities of the B-TCP and B-TCP/Collagen biomaterials were determined by alkaline phosphatase and Von Kossa stainings, and RT-PCR analysis. The ALP activity of the B-TCP/Col containing material was significantly higher than the B-TCP on the first days. In terms of gene expression, there were no significant differences except 14th-day SPARC gene expression. The results of Von Kossa staining indicate that B-TCP/Col has above the desired level degradation capacity. As a result of this research, although it is advantageous in terms of alkaline phosphatase activity and osteogenic gene expression compared to B-TCP material, it is thought that B-TCP/Collagen biomaterial should be developed for use in bone tissue engineering due to its high degradation property.

A Simple Preparation Method of Gelatin Hydrogels Incorporating Cisplatin for Sustained Release

The objective of this study was to develop a new preparation method for cisplatin (CDDP)-incorporated gelatin hydrogels without using chemical crosslinking nor a vacuum heating instrument for dehydrothermal crosslinking. By simply mixing CDDP and gelatin, CDDP-crosslinked gelatin hydrogels (CCGH) were prepared. CDDP functions as a crosslinking agent of gelatin to form the gelatin hydrogel. Simultaneously, CDDP is incorporated into the gelatin hydrogel as a controlled release carrier. CDDP's in vitro and in vivo anticancer efficacy after incorporation into CCGH was evaluated. In the in vitro system, the CDDP was released gradually due to CCGH degradation with an initial burst release of approximately 16%. CDDP metal-coordinated with the degraded fragment of gelatin was released from CCGH with maintaining the anticancer activity. After intraperitoneal administration of CCGH, CDDP was detected in the blood circulation while its toxicity was low. Following intraperitoneal administration of CCGH in a murine peritoneal dissemination model of human gastric cancer MKN45-Luc cell line, the survival time was significantly prolonged compared with free CDDP solution. It is concluded that CCGH prepared by the CDDP-based crosslinking of gelatin is an excellent sustained release system of CDDP to achieve superior anticancer effects with minimal side effects compared with free CDDP solution.

Octacalcium Phosphate/Gelatin Composite (OCP/Gel) Enhances Bone Repair in a Critical-sized Transcortical Femoral Defect Rat Model

BACKGROUND

Bone grafting is widely used to treat large bone defects. A porous composite of a bioactive octacalcium phosphate material with gelatin sponge (OCP/Gel) has been shown to biodegrade promptly and be replaced with new bone both in animal models of a membranous bone defect and a long bone defect. However, it is unclear whether OCP/Gel can regenerate bone in more severe bone defects, such as a critical-size transcortical defect.

QUESTIONS/PURPOSES

Using an in vivo rat femur model of a standardized, transcortical, critical-size bone defect, we asked: Compared with a Gel control, does OCP/Gel result in more newly formed bone as determined by (1) micro-CT evaluation, (2) histologic and histomorphometric measures, and (3) osteocalcin staining and tartrate-resistant acid phosphatase staining?

METHODS

Thirty-four 12-week-old male Sprague-Dawley rats (weight 356 ± 25.6 g) were used. Gel and OCP/Gel composites were prepared in our laboratory. Porous cylinders 3 mm in diameter and 4 mm in height were manufactured from both materials. The OCP/Gel and Gel cylinders were implanted into a 3-mm-diameter transcortical critical-size bone defect model in the left rat femur. The OCP/Gel and Gel were randomly assigned, and the cylinders were implanted. The biological responses of the defect regions were evaluated radiologically and histologically. At 4 and 8 weeks after implantation, CT evaluation, histological examination of decalcified samples, and immunostaining were quantitatively performed to evaluate new bone formation and remaining bone graft substitutes and activity of osteoblasts and osteoclast-like cells (n = 24). Qualitative histological evaluation was performed on undecalcified samples at 3 weeks postimplantation (n = 10). CT and decalcified tissue analysis was not performed blinded, but an analysis of undecalcified specimens was performed under blinded conditions.

RESULTS

Radiologic analysis revealed that the OCP/Gel group showed radiopaque regions around the OCP granules and at the edge of the defect margin 4 weeks after implantation, suggesting that new bone formation occurred in two ways. In contrast, the rat femurs in the Gel group had a limited radiopaque zone at the edge of the defect region. The amount of new bone volume analyzed by micro-CT was higher in the OCP/Gel group than in the Gel group at 4 and 8 weeks after implantation (​​4 weeks after implantation: OCP/Gel versus Gel: 6.1 ± 1.6 mm 3 versus 3.4 ± 0.7 mm 3 , mean difference 2.7 [95% confidence interval (CI) 0.9 to 4.5]; p = 0.002; intraclass correlation coefficient [ICC] 0.72 [95% CI 0.29 to 0.91]; 8 weeks after implantation: OCP/Gel versus Gel: 3.9 ± 0.7 mm 3 versus 1.4 ± 1.1 mm 3 , mean difference 2.5 [95% CI 0.8 to 4.3]; p = 0.004; ICC 0.81 [95% CI 0.47 to 0.94]). Histologic evaluation also showed there was a higher percentage of new bone formation in the OCP/Gel group at 4 and 8 weeks after implantation (​​4 weeks after implantation: OCP/Gel versus Gel: 31.2% ± 5.3% versus 13.6% ± 4.0%, mean difference 17.6% [95% CI 14.2% to 29.2%]; p < 0.001; ICC 0.83 [95% CI 0.53 to 0.95]; 8 weeks after implantation: OCP/Gel versus Gel: 28.3% ± 6.2% versus 9.5% ± 1.9%, mean difference 18.8% [95% CI 11.3% to 26.3%]; p < 0.001; ICC 0.90 [95% CI 0.69 to 0.97]). Bridging of the defect area started earlier in the OCP/Gel group than in the Gel group at 4 weeks after implantation. Osteocalcin immunostaining showed that the number of mature osteoblasts was higher in the OCP/Gel group than in the Gel group at 4 weeks (OCP/Gel versus Gel: 42.1 ± 6.5/mm 2 versus 17.4 ± 5.4/mm 2 , mean difference 24.7 [95% CI 16.2 to 33.2]; p < 0.001; ICC 0.99 [95% CI 0.97 to 0.99]). At 4 weeks, the number of osteoclast-like cells was higher in the OCP/Gel composite group than in the Gel group (OCP/Gel versus Gel: 3.2 ± 0.6/mm 2 versus 0.9 ± 0.4/mm 2 , mean difference 2.3 [95% CI 1.3 to 3.5]; p < 0.001; ICC 0.79 [95% CI 0.35 to 0.94]).

CONCLUSION

OCP/Gel composites induced early bone remodeling and cortical bone repair in less time than did the Gel control in a rat critical-size, transcortical femoral defect, suggesting that OCP/Gel could be used as a bone replacement material to treat severe bone defects.

CLINICAL RELEVANCE

In a transcortical bone defect model of critical size in the rat femur, the OCP/Gel composite demonstrated successful bone regeneration. Several future studies are needed to evaluate the clinical application of this interesting bone graft substitute, including bone formation capacity in refractory fracture and spinal fusion models and the comparison of bone strength after repair with OCP/Gel composite to that of autologous bone.

Human gelatin-based composite hydrogels for osteochondral tissue engineering and their adaptation into bioinks for extrusion, inkjet, and digital light processing bioprinting

The investigation of novel hydrogel systems allows for the study of relationships between biomaterials, cells, and other factors within osteochondral tissue engineering. Three-dimensional (3D) printing is a popular research method that can allow for further interrogation of these questions via the fabrication of 3D hydrogel environments that mimic tissue-specific, complex architectures. However, the adaptation of promising hydrogel biomaterial systems into 3D-printable bioinks remains a challenge. Here, we delineated an approach to that process. First, we characterized a novel methacryloylated gelatin composite hydrogel system and assessed how calcium phosphate and glycosaminoglycan additives upregulated bone- and cartilage-like matrix deposition and certain genetic markers of differentiation within human mesenchymal stem cells (hMSCs), such as RUNX2 and SOX9. Then, new assays were developed and utilized to study the effects of xanthan gum and nanofibrillated cellulose, which allowed for cohesive fiber deposition, reliable droplet formation, and non-fracturing digital light processing (DLP)-printed constructs within extrusion, inkjet, and DLP techniques, respectively. Finally, these bioinks were used to 3D print constructs containing viable encapsulated hMSCs over a 7 d period, where DLP printed constructs facilitated the highest observed increase in cell number over 7 d (∼2.4×). The results presented here describe the promotion of osteochondral phenotypes via these novel composite hydrogel formulations, establish their ability to bioprint viable, cell-encapsulating constructs using three different 3D printing methods on multiple bioprinters, and document how a library of modular bioink additives affected those physicochemical properties important to printability.

Synergistic Effect of Whitlockite Scaffolds Combined with Alendronate to Promote Bone Regeneration

BACKGROUND

Due to the increasing aging of society, the number of patients suffering from senile diseases is increasing. Patients suffering from osteoporosis, which is a representative senile disease, take a long time to recover from fractures, and the resulting mortality rate is very high. Alendronate (Ald), which is widely used as a treatment for osteoporosis, alleviates osteoporosis by inhibiting osteoclasts. In addition, whitlockite (WH) promotes the osteogenic differentiation of bone cells and improves bone regeneration. Therefore, we intended to bring about a synergistic effect by using these substances together.

METHODS

In this study, a scaffold composed of gelatin/heparin was fabricated and applied to effectively use WH and Ald together. A scaffold was constructed using gelatin and heparin was used to effectively utilize the cations released from WH. In addition, it formed a porous structure for effective bone regeneration. In vitro and in vivo osteoclast inhibition, osteogenic differentiation, and bone regeneration were studied using the prepared scaffolds.

RESULTS

The inhibition of osteoclast was much higher when WH and Ald were applied in combination rather than individually. The highest level of osteogenic differentiation was observed when both substances were applied simultaneously. In addition, when applied to bone regeneration through the mouse calvarial defect model, combined treatment showed excellent bone regeneration.

CONCLUSION

Therefore, this study showed the synergistic effect of WH and Ald, and it is suggested that better bone regeneration is possible by applying this treatment to bones with fractures that are difficult to regenerate.

Cobalt-doped bioceramic scaffolds fabricated by 3D printing show enhanced osteogenic and angiogenic properties for bone repair

Background

The bone regeneration of artificial bone grafts is still in need of a breakthrough to improve the processes of bone defect repair. Artificial bone grafts should be modified to enable angiogenesis and thus improve osteogenesis. We have previously revealed that crystalline Ca₁₀Li(PO₄)₇ (CLP) possesses higher compressive strength and better biocompatibility than that of pure beta-tricalcium phosphate (β-TCP). In this work, we explored the possibility of cobalt (Co), known for mimicking hypoxia, doped into CLP to promote osteogenesis and angiogenesis.

Methods

We designed and manufactured porous scaffolds by doping CLP with various concentrations of Co (0, 0.1, 0.25, 0.5, and 1 mol%) and using 3D printing techniques. The crystal phase, surface morphology, compressive strength, in vitro degradation, and mineralization properties of Co-doped and -undoped CLP scaffolds were investigated. Next, we investigated the biocompatibility and effects of Co-doped and -undoped samples on osteogenic and angiogenic properties in vitro and on bone regeneration in rat cranium defects.

Results

With increasing Co-doping level, the compressive strength of Co-doped CLP scaffolds decreased in comparison with that of undoped CLP scaffolds, especially when the Co-doping concentration increased to 1 mol%. Co-doped CLP scaffolds possessed excellent degradation properties compared with those of undoped CLP scaffolds. The (0.1, 0.25, 0.5 mol%) Co-doped CLP scaffolds had mineralization properties similar to those of undoped CLP scaffolds, whereas the 1 mol% Co-doped CLP scaffolds shown no mineralization changes. Furthermore, compared with undoped scaffolds, Co-doped CLP scaffolds possessed excellent biocompatibility and prominent osteogenic and angiogenic properties in vitro, notably when the doping concentration was 0.25 mol%. After 8 weeks of implantation, 0.25 mol% Co-doped scaffolds had markedly enhanced bone regeneration at the defect site compared with that of the undoped scaffold.

Conclusion

In summary, CLP doped with 0.25 mol% Co²⁺ ions is a prospective method to enhance osteogenic and angiogenic properties, thus promoting bone regeneration in bone defect repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12938-021-00907-2.

A novel gelatin/chitooligosaccharide/demineralized bone matrix composite scaffold and periosteum-derived mesenchymal stem cells for bone tissue engineering

Background

A novel biodegradable scaffold including gelatin (G), chitooligosaccharide (COS), and demineralized bone matrix (DBM) could play a significant part in bone tissue engineering. The present study aimed to investigate the biological characteristics of composite scaffolds in combination of G, COS, and DBM for in vitro cell culture and in vivo animal bioassays.

Methods

Three-dimensional scaffolds from the mixture of G, COS, and DBM were fabricated into 3 groups, namely, G, GC, and GCD using a lyophilization technique. The scaffolds were cultured with mesenchymal stem cells (MSCs) for 4 weeks to determine biological responses such as cell attachment and cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition, cell morphology, and cell surface elemental composition. For the in vivo bioassay, G, GC, and GCD, acellular scaffolds were implanted subcutaneously in 8-week-old male Wistar rats for 4 weeks and 8 weeks. The explants were assessed for new bone formation using hematoxylin and eosin (H&E) staining and von Kossa staining.

Results

The MSCs could attach and proliferate on all three groups of scaffolds. Interestingly, the ALP activity of MSCs reached the greatest value on day 7 after cultured on the scaffolds, whereas the calcium assay displayed the highest level of calcium in MSCs on day 28. Furthermore, weight percentages of calcium and phosphorus on the surface of MSCs after cultivation on the GCD scaffolds increased when compared to those on other scaffolds. The scanning electron microscopy images showed that MSCs attached and proliferated on the scaffold surface thoroughly over the cultivation time. Mineral crystal aggregation was evident in GC and greatly in GCD scaffolds. H&E staining illustrated that G, GC, and GCD scaffolds displayed osteoid after 4 weeks of implantation and von Kossa staining confirmed the mineralization at 8 weeks in G, GC, and GCD scaffolds.

Conclusion

The MSCs cultured in GCD scaffolds revealed greater osteogenic differentiation than those cultured in G and GC scaffolds. Additionally, the G, GC, and GCD scaffolds could promote in vivo ectopic bone formation in rat model. The GCD scaffolds exhibited maximum osteoinductive capability compared with others and may be potentially used for bone regeneration.

Abnormal macrophage polarization impedes the healing of diabetes-associated tooth sockets

Patients with poorly controlled type 2 diabetes mellitus (T2DM) often experience delayed tooth extraction socket (TES) healing. Delayed healing is often associated with an aberrant inflammatory response orchestrated by either M1 pro-inflammatory or M2 anti-inflammatory macrophages. However, the precise mechanism for the attenuated TES healing remains unclear. Here we used diet-induced T2DM mice as a model to study TES. Compared with the control group, the T2DM group showed delayed TES healing and diminished expression of osteogenic and angiogenic genetic profiles. Meanwhile, we detected a more inflammatory profile, with more M1 macrophages and TNF-α expression and less M2 macrophages and PPARγ expression, in TES in the T2DM group when compared to control mice. In vitro co-culture models showed that M1 macrophages inhibited the osteogenic capacity of bone marrow stromal cells and the angiogenic capacity of endothelial cells while M2 macrophages showed an opposite effect. In addition, we constructed a gelatin/β-TCP scaffold with IL-4 to induce macrophage transformation towards M2 polarization. In vitro analyses of the hybrid scaffold revealed sustained release of IL-4 and a phenotype switch to M2 macrophages. Finally, we demonstrated that sustained IL-4 release significantly increased expression of osteogenic and angiogenic genetic profiles and improved TES healing in T2DM mice. Together, we report that increased M1 and decreased M2 macrophage polarization may be responsible for delayed TES healing in T2DM patients through abnormal expression of TNF-α and PPARγ. This imbalance negatively influences osteogenesis and angiogenesis, two of the most important biological factors in bone wound healing. Enhancing M2 macrophage polarization with IL-4 delivery system may represent a potential strategy for promoting the healing of TES in T2DM patients.

Addition of glycerol enhances the flexibility of gelatin hydrogel sheets; application for in utero tissue engineering

Gelatin hydrogels are naturally derived scaffolds useful for tissue engineering because of their cytocompatibility and controllable degradability. However, they are brittle and inflexible when dry, which limits their use for in utero tissue engineering in large animal models. Therefore, in this study, we attempted to generate flexible gelatin sheets by adding various plasticizers with different molecular weights (MW). We systematically evaluated the flexibility, sustainability, and potential clinical utility of the resulting flexible gelatin sheets. Gelatin sheets with low-MW plasticizers, such as monosaccharides or sugar alcohols, showed a reduced tensile modulus in dynamic viscoelasticity, which reflected their actual flexibility. Wet gelatin sheets containing plasticizers showed higher tensile strength than the nonplasticizer control, although wet gelatin sheets under all conditions had a much lower tensile strength than dry gelatin sheets. In a functional study, gelatin sheets containing glycerol, which has the lowest MW among sugar alcohols, showed encouraging results, such as good fit to the curvature of the experimental animal, biocompatibility, and suitability for endoscopic approaches. The findings of this study should enable the expansion of future applications for flexible gelatin sheets.

Three-Dimensional Culture System of Cancer Cells Combined with Biomaterials for Drug Screening

Simple Summary

For the research and development of drug discovery, it is of prime importance to construct the three-dimensional (3D) tissue models in vitro. To this end, the enhancement design of cell function and activity by making use of biomaterials is essential. In this review, 3D culture systems of cancer cells combined with several biomaterials for anticancer drug screening are introduced.

Abstract

Anticancer drug screening is one of the most important research and development processes to develop new drugs for cancer treatment. However, there is a problem resulting in gaps between the in vitro drug screening and preclinical or clinical study. This is mainly because the condition of cancer cell culture is quite different from that in vivo. As a trial to mimic the in vivo cancer environment, there has been some research on a three-dimensional (3D) culture system by making use of biomaterials. The 3D culture technologies enable us to give cancer cells an in vitro environment close to the in vivo condition. Cancer cells modified to replicate the in vivo cancer environment will promote the biological research or drug discovery of cancers. This review introduces the in vitro research of 3D cell culture systems with biomaterials in addition to a brief summary of the cancer environment.

Electrospinning Nanofiber-Reinforced Aerogels for the Treatment of Bone Defects

Objective: Application of aerogels in bone tissue engineering is an emerging field, while the reports of electrospinning nanofiber-reinforced aerogels are limited. This research aimed at fabricating the nanofiber-reinforced aerogels and evaluating their physiochemical and biological properties. Approach: The chitosan (CS) aerogels incorporated with cellulose acetate (CA) and poly (ɛ-caprolactone) (PCL) nanofibers were fabricated via ball milling and freeze-drying techniques. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectrum, X-ray photoelectron spectroscopy (XPS), compressive experiment, and in vitro experiment were conducted to assess their physiochemical properties and biological behavior. Results: The SEM examination showed that satisfying morphology was attained in the CA/PCL/CS aerogels with incorporation of CA/PCL nanofibers and CS solution. The results of FT-IR and XPS indicated the perfect incorporation of CA, PCL, and CS. A compressive experiment confirmed that the CA/PCL/CS aerogels enhanced the compressive modulus of the pure CS aerogel. For in vitro experiment, the CA/PCL/CS composite scaffolds were proven to possess better cytocompatibility compared with the pure CS. Also, cells on the CA/PCL/CS showed well-extended morphology and could infiltrate into a porous scaffold. Furthermore, confocal experiment revealed that the CA/PCL/CS could also promote the osteogenic differentiation of MC3T3-E1 cells. Innovation: This study fabricated the nanofiber-reinforced aerogels mainly to optimize the cell/material interaction of the pure CS scaffold. Conclusion: The CA/PCL nanofibers not only improved the mechanical property of the CS aerogel to some extent but also facilitated cell adhesion and osteogenic differentiation. Thus, it could be considered a promising candidate for bone tissue engineering.

Development of hybrid scaffold: Bioactive glass nanoparticles/chitosan for tissue engineering applications

Bone tissue engineering is gaining popularity as an alternative method for the treatment of osseous defects. A number of biodegradable polymers have been explored for tissue engineering purposes. A new family of biodegradable polymer/bioactive glass composite materials has been designed to be used in bone regeneration approaches. In this work, a hybrid scaffold of chitosan (CH) and bioactive glass nanoparticles (BGN) was prepared by the freeze-gelation method. This method has been studied by adjusting the concentration of acetic acid; this process can influence the structure properties of the scaffold. In this work, several BGN/CH composites have been prepared by varying the proportion of BGN in the hybrid scaffold (20, 40, 60, and 80%). Brunauer-Emmett-Teller results showed the increased surface area and porosity volume of our composite with decreasing BGN proportion. BGN/CH hybrid scaffold was characterized by using physicochemical techniques. Obtained results showed a macroporous morphology of the scaffold with a pore size of about 200 μm, and a homogeneous distribution of the BGN in the CH matrix. X-ray diffraction study confirmed the amorphous state of the BGN/CH hybrid scaffold. Interaction between CH and BGNs in the composite was confirmed. The in vitro assays showed adequate degradation properties, which is essential for the potential replacement by the new tissue. The in vitro bioactivity studies confirmed the formation of an apatite layer on the surface of the hybrid scaffold, which results in a direct bone bonding of the implant. These results indicate that BGN/CH hybrid scaffold developed is a potential candidate for bone tissue engineering.

A Co-Culture System of Three-Dimensional Tumor-Associated Macrophages and Three-Dimensional Cancer-Associated Fibroblasts Combined with Biomolecule Release for Cancer Cell Migration

The objective of this study is to design a cancer invasion model by making use of cancer-associated fibroblasts (CAF) or tumor-associated macrophages (TAM) and gelatin hydrogel microspheres (GM) for the sustained release of drugs. The GM containing adenosine (A) (GM-A) were prepared and cultured with TAM to obtain three-dimensional (3D) TAM aggregates incorporating GM-A (3D TAM-GM-A). The GM-A incorporation enabled TAM to enhance the secretion level of vascular endothelial growth factor. When co-cultured with HepG2 liver cancer cells in an invasion assay, the 3D TAM-GM-A promoted the invasion rate of cancer cells. In addition, the E-cadherin expression level decreased to a significantly greater extent compared with that co-cultured with TAM aggregates incorporating GM, whereas the significantly higher expression of N-cadherin and Vimentin was observed. This indicates that the epithelial-mesenchymal transition event was induced. The GM containing transforming growth factor-β1 (TGF-β1) were prepared to incorporate into 3D CAF (3D CAF-GM-TGF-β1). Following a co-culture of mixed 3D CAF-GM-TGF-β1 and 3D TAM-GM-A and every HepG2, MCF-7 breast cancer cell, or WA-hT lung cancer cell, the invasion rate of every cancer cell enhanced depending on the mixing ratio of 3D TAM-GM-A and 3D CAF-GM-TGF-β1. The amount of matrix metalloproteinase-2 (MMP-2) secreted also enhanced, and the enhancement was well corresponded with that of cancer cell invasion rate. The higher MMP secretion assists the breakdown of basement membrane, leading to the higher rate of cancer cell invasion. This model is a promising 3D culture system to evaluate the invasion ability of various cancer cells in vitro. Impact statement This study proposes a cell culture system to enhance the tumor-associated macrophage function based on the combination of three-dimensional (3D) cell aggregates and gelatin hydrogel microspheres (GM) for adenosine delivery. An additional combination of 3D cancer-associated fibroblasts incorporating GM containing transforming growth factor-β1 allowed cancer cells to enhance their invasion rate. This co-culture system is promising to evaluate the ability of cancer cell invasion for anticancer drug screening.

Octacalcium phosphate bone substitute materials: Comparison between properties of biomaterials and other calcium phosphate materials

Octacalcium phosphate (OCP) is a material that can be converted to hydroxyapatite (HA) under physiological environments and is considered a mineral precursor to bone apatite crystals. The structure of OCP consists of apatite layers stacked alternately with hydrated layers, and closely resembles the structure of HA. The performance of OCP as a bone substitute differs from that of HA materials in terms of their osteoconductivity and biodegradability. OCP manifests a cellular phagocytic response through osteoclast-like cells similar to that exhibited by the biodegradable material β-tricalcium phosphate (β-TCP). The use of OCP for human cranial bone defects involves using its granule or composite form with one of the natural polymers, viz., the reconstituted collagen. This review article discusses the differences and similarities in these calcium phosphate (Ca-P)-based materials from the viewpoint of the structure and their material chemistry, and attempts to elucidate why Ca-P materials, particularly OCP, display unique osteoconductive property.

A cancer invasion model of cancer-associated fibroblasts aggregates combined with TGF-β1 release system

Introduction

The objective of this study is to design a cancer invasion model where the cancer invasion rate can be regulated in vitro.

Methods

Cancer-associated fibroblasts (CAF) aggregates incorporating gelatin hydrogel microspheres (GM) containing various concentrations of transforming growth factor-β1 (TGF-β1) (CAF-GM-TGF-β1) were prepared. Alpha-smooth muscle actin (α-SMA) for the CAF aggregates was measured to investigate the CAF activation level by changing the concentration of TGF-β1. An invasion assay was performed to evaluate the cancer invasion rate by co-cultured of cancer cells with various CAF-GM-TGF-β1.

Results

The expression level of α-SMA for CAF increased with an increased in the TGF-β1 concentration. When co-cultured with various types of CAF-GM-TGF-β1, the cancer invasion rate was well correlated with the α-SMA level. It is conceivable that the TGF-β1 concentration could modify the level of CAF activation, leading to the invasion rate of cancer cells. In addition, at the high concentrations of TGF-β1, the effect of a matrix metalloproteinase (MMP) inhibitor on the cancer invasion rate was observed. The higher invasion rate would be achieved through the higher MMP production.

Conclusions

The present model is promising to realize the cancer invasion whose rate can be modified by changing the TGF-β1 concentration.

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This invasion model would be a promising tool for anti-cancer drug screening.

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TGF-β1 was controlled release from gelatin hydrogel microspheres.

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CAF were activated by increased TGF-β1 concentration.

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There was a good correlation between invasion rate and TGF-β1 concentration.

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Higher invasion rate would be achieved through matrix metalloproteinase production.

Electrospun poly(3-hydroxybutyrate-co-4-hydroxybutyrate) /Octacalcium phosphate Nanofibrous membranes for effective guided bone regeneration

Membranes used in guided bone regeneration (GBR) are required to exhibit high mechanical strength, biocompatibility, biodegradation, osteogenic and osteoinductive potential. In our study, poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(P(3HB-co-4HB))/octacalcium phosphate (OCP) (P(3HB-co-4HB)/OCP) nanofibrous membranes were fabricated by electrospinning with two different P(3HB-co-4HB) to OCP ratios (P(3HB-co-4HB):OCP = 95:5 wt% and 90:10 wt%, termed P(3HB-co-4HB)/OCP(5)and P(3HB-co-4HB)/OCP (10), respectively) for GBR. The developed P(3HB-co-4HB)/OCP nanofibrous membranes were analysed for their osteogenic and osteoinductive properties using mesenchymal stem cells (MSCs) in vitro and in a calvarial bone defect rat model. The composite P(3HB-co-4HB)/OCP nanofibrous membranes showed decreased fibre size and enhanced tensile strength compared with those of P(3HB-co-4HB) nanofibrous membranes. In the in vitro studies, the P(3HB-co-4HB)/OCP membranes facilitated cell growth and osteoblastic differentiation of MSCs and were superior to P(3HB-co-4HB) membranes. After covered on the calvarial bone defects, P(3HB-co-4HB)/OCP membranes facilitated greater neobone formation than P(3HB-co-4HB) membranes did, as the result of histological evaluation and micro-CT analysis with higher bone volume/total volume (BV/TV) ratio and bone mineral density (BMD). P(3HB-co-4HB)/OCP(10) membranes with higher OCP content showed greater stiffness and osteoinductivity than P(3HB-co-4HB)/OCP (5)membranes, demonstrating the role of OCP in the composite membranes. These results indicated that electrospun P(3HB-co-4HB)/OCP nanofibrous membranes hold promise for the clinical application of GBR.

Biodegradable Polymers as Drug Delivery Systems for Bone Regeneration

Regenerative medicine has been widely researched for the treatment of bone defects. In the field of bone regenerative medicine, signaling molecules and the use of scaffolds are of particular importance as drug delivery systems (DDS) or carriers for cell differentiation, and various materials have been explored for their potential use. Although calcium phosphates such as hydroxyapatite and tricalcium phosphate are clinically used as synthetic scaffold material for bone regeneration, biodegradable materials have attracted much attention in recent years for their clinical application as scaffolds due their ability to facilitate rapid localized absorption and replacement with autologous bone. In this review, we introduce the types, features, and performance characteristics of biodegradable polymer scaffolds in their role as DDS for bone regeneration therapy.

Multimaterial Dual Gradient Three-Dimensional Printing for Osteogenic Differentiation and Spatial Segregation

In this study of three-dimensional (3D) printed composite β-tricalcium phosphate (β-TCP)-/hydroxyapatite/poly(ɛ-caprolactone)-based constructs, the effects of vertical compositional ceramic gradients and architectural porosity gradients on the osteogenic differentiation of rabbit bone marrow-derived mesenchymal stem cells (MSCs) were investigated. Specifically, three different concentrations of β-TCP (0, 10, and 20 wt%) and three different porosities (33% ± 4%, 50% ± 4%, and 65% ± 3%) were examined to elucidate the contributions of chemical and physical gradients on the biochemical behavior of MSCs and the mineralized matrix production within a 3D culture system. By delaminating the constructs at the gradient transition point, the spatial separation of cellular phenotypes could be specifically evaluated for each construct section. Results indicated that increased concentrations of β-TCP resulted in upregulation of osteogenic markers, including alkaline phosphatase activity and mineralized matrix development. Furthermore, MSCs located within regions of higher porosity displayed a more mature osteogenic phenotype compared to MSCs in lower porosity regions. These results demonstrate that 3D printing can be leveraged to create multiphasic gradient constructs to precisely direct the development and function of MSCs, leading to a phenotypic gradient. Impact Statement In this study, three-dimensional (3D) printed ceramic/polymeric constructs containing discrete vertical gradients of both composition and porosity were fabricated to precisely control the osteogenic differentiation of mesenchymal stem cells. By making simple alterations in construct architecture and composition, constructs containing heterogenous populations of cells were generated, where gradients in scaffold design led to corresponding gradients in cellular phenotype. The study demonstrates that 3D printed multiphasic composite constructs can be leveraged to create complex heterogeneous tissues and interfaces.

Osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells encapsulated in Thai silk fibroin/collagen hydrogel: a pilot study in vitro

Background

Silk fibroin (SF) can be processed into a hydrogel. SF/collagen hydrogel may be a suitable biomaterial for bone tissue engineering.

Objectives

To investigate in vitro biocompatibility and osteogenic potential of encapsulated rat bone marrow-derived mesenchymal stem cells (rat MSCs) in an injectable Thai SF/collagen hydrogel induced by oleic acid–poloxamer 188 surfactant mixture in an in vitro pilot study.

Methods

Rat MSCs were encapsulated in 3 groups of hydrogel scaffolds (SF, SF with 0.05% collagen [SF/0.05C], and SF with 0.1% collagen [SF/0.1C]) and cultured in a growth medium and an osteogenic induction medium. DNA, alkaline phosphatase (ALP) activity, and calcium were assayed at periodically for up to 5 weeks. After 6 weeks of culture the cells were analyzed by scanning electron microscopy and energy dispersive spectroscopy.

Results

Although SF hydrogel with collagen seems to have less efficiency to encapsulate rat MSCs, their plateau phase growth in all hydrogels was comparable. Inability to maintain cell viability as cell populations declined over 1–5 days was observed. Cell numbers then plateaued and were maintained until day 14 of culture. ALP activity and calcium content of rat MSCs in SF/collagen hydrogels were highest at day 21. An enhancing effect of collagen combined with the hydrogel was observed for proliferation and matrix formation; however, benefits of the combination on osteogenic differentiation and biomineralization are as yet unclear.

Conclusion

Rat MSCs in SF and SF/collagen hydrogels showed osteogenic differentiation. Accordingly, these hydrogels may serve as promising scaffolds for bone tissue engineering.

Nanohybrid Scaffold of Chitosan and Functionalized Graphene Oxide for Controlled Drug Delivery and Bone Regeneration

Nanohybrid scaffolds of chitosan have been designed for controlled drug delivery and bone regeneration. Sulfonated graphene oxide has been used to develop the nanohybrids. Nanohybrid scaffolds show highly hydrophilic character and greater mechanical strength as compared to pure chitosan. Nanohybrid scaffolds show an interconnected uniform porous network structure exhibiting sustained release kinetics of the antibacterial drug, tetracycline hydrochloride. Nanohybrids are found to be highly biocompatible in nature and are able to support and proliferate MG63 osteoblast cells and thereby induce bone tissue regeneration. The in-vivo bone healing study shows that the developed nanohybrid scaffolds have the potential to regenerate the bone faster without any side effects as compared to pure scaffolds. Hence, the developed nanohybrid scaffold has good potential as a controlled drug delivery vehicle and in bone tissue engineering for faster healing.

Vertical ridge augmentation using a porous composite of uncalcined hydroxyapatite and poly-DL-lactide enriched with types 1 and 3 collagen

BACKGROUND

Previous studies have shown that porous composite blocks containing uncalcined hydroxyapatite (u-HA; 70 wt%) with a scaffold of poly-DL-lactide (PDLLA, 30 wt%) are biodegradable, encourage appropriate bone formation, and are suitable for use as a bone substitute in vertical ridge augmentation. The present study aimed to accelerate osteogenesis in vertical ridge formation by adding types 1 and 3 collagen to the u-HA/PDLLA blocks and assessing the effect.

MATERIAL AND METHODS

The bone substitute in the present study comprised porous composite blocks of u-HA (70 wt%) with a PDLLA (27-29 wt%) scaffold and enriched with types 1 and 3 collagen (1.7 ~ 3.4 wt%). The control blocks were composed of u-HA (70 wt%) and PDLLA (30 wt%). The materials were formed into 8-mm diameter, 2-mm high discs and implanted onto the cranial bones of six rabbits. The animals were sacrificed 4 weeks after implantation, and histological and histomorphometrical analyses were performed to quantitatively evaluate newly formed bone.

RESULTS

New bone formation occurred with both block types, showing direct contact with the original bone. Mean ± standard deviation bone formation was significantly greater in the experimental blocks (25.6% ± 4.8%) than in the control blocks (17.0% ± 4.7%).

CONCLUSIONS

Histological and histomorphometrical observations indicated that new bone was formed with both block types. The u-HA/PDLLA block with types 1 and 3 collagen is a more promising candidate for vertical ridge augmentation than the u-HA/PDLLA alone block.

Organically modified hydroxyapatite (ormoHAP) nanospheres stimulate the differentiation of osteoblast and osteoclast precursors: a co-culture study

Isolated nanospheres consisting of organically modified hydroxyapatite (ormoHAP), prepared by an electric field-assisted ion double migration process, were embedded in foamed gelatin to form a composite scaffold. Degradation rates have been demonstrated to correlate with the crosslinking degree (40%, 80%) as well as with the mineral content of the scaffolds (0%, 20%, 40%). A human co-culture model of osteoblasts and osteoclasts, derived from bone marrow stromal cells and monocytes, respectively, without external addition of the factors RANKL and M-CSF, was run for up to 42 d in order to characterize the action of the ormoHAP-gelatin scaffolds on the co-culture. Examination was performed by quantitative biochemical methods (DNA, LDH, ALP, TRAP5b), gene expression analysis (ALP, BSP II, RANKL, IL-6, VTNR, CTSK, TRAP, OSCAR, CALCR) and confocal laser scanning microscopy (cell nuclei, actin, CD68, TRAP). Results confirm that ormoHAP embedded in the gelatin matrix enhanced TRAP 5b activity. As a feedback, ALP activity and gene expression of BSP II of osteoblasts increased. Finally, a sequence of cell cross-talk actions is suggested, which can explain the behavior of the formed vital co-culture and moreover the influence of the presence and concentration of ormoHAP.

Egg shell-derived calcium phosphate/carbon dot nanofibrous scaffolds for bone tissue engineering: Fabrication and characterization

Recent exciting findings of the particular properties of Carbon dot (CDs) have shed light on potential biomedical applications of CDs-containing composites. While CDs so far have been widely used as biosensors and bioimaging agents, in the present study for the first time, we evaluate the osteoconductivity of CDs in poly (ε-caprolactone) (PCL)/polyvinyl alcohol (PVA) [PCL/PVA] nanofibrous scaffolds. Moreover, further studies were performed to evaluate egg shell-derived calcium phosphate (TCP3) and its cellular responses, biocompatibility and in vitro osteogenesis. Scaffolds were fabricated by simultaneous electrospinning of PCL with three different types of calcium phosphate, PVA and CDs. Fabricated scaffolds were characterized by Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), contact angle measurement and degradation assessment. SEM, the methyl thiazolyl tetrazolium (MTT) assay, and alkaline phosphatase (ALP) activity test were performed to evaluate cell morphology, proliferation and osteogenic differentiation, respectively. The results demonstrated that while the addition of just 1 wt% CDs and TCP3 individually into PCL/PVA nanocomposite enhanced ALP activity and cell proliferation rate (p < 0.05), the synergetic effect of CDs/TCP3 led to highest osteogenic differentiation and proliferation rate compared to other scaffolds (p < 0.05). Hence, CDs and PCL/PVA-TCP3 could serve as a potential candidate for bone tissue regeneration.

Enzymatically Cross-Linked Silk Fibroin-Based Hierarchical Scaffolds for Osteochondral Regeneration

Osteochondral (OC) regeneration faces several limitations in orthopedic surgery, owing to the complexity of the OC tissue that simultaneously entails the restoration of articular cartilage and subchondral bone diseases. In this study, novel biofunctional hierarchical scaffolds composed of a horseradish peroxidase (HRP)-cross-linked silk fibroin (SF) cartilage-like layer (HRP-SF layer) fully integrated into a HRP-SF/ZnSr-doped β-tricalcium phosphate (β-TCP) subchondral bone-like layer (HRP-SF/dTCP layer) were proposed as a promising strategy for OC tissue regeneration. For comparative purposes, a similar bilayered structure produced with no ion incorporation (HRP-SF/TCP layer) was used. A homogeneous porosity distribution was achieved throughout the scaffolds, as shown by micro-computed tomography analysis. The ion-doped bilayered scaffolds presented a wet compressive modulus (226.56 ± 60.34 kPa) and dynamic mechanical properties (ranging from 403.56 ± 111.62 to 593.56 ± 206.90 kPa) superior to that of the control bilayered scaffolds (189.18 ± 90.80 kPa and ranging from 262.72 ± 59.92 to 347.68 ± 93.37 kPa, respectively). Apatite crystal formation, after immersion in simulated body fluid (SBF), was observed in the subchondral bone-like layers for the scaffolds incorporating TCP powders. Human osteoblasts (hOBs) and human articular chondrocytes (hACs) were co-cultured onto the bilayered structures and monocultured in the respective cartilage and subchondral bone half of the partitioned scaffolds. Both cell types showed good adhesion and proliferation in the scaffold compartments, as well as adequate integration of the interface regions. Osteoblasts produced a mineralized extracellular matrix (ECM) in the subchondral bone-like layers, and chondrocytes showed GAG deposition. The gene expression profile was different in the distinct zones of the bilayered constructs, and the intermediate regions showed pre-hypertrophic chondrocyte gene expression, especially on the BdTCP constructs. Immunofluorescence analysis supported these observations. This study showed that the proposed bilayered scaffolds allowed a specific stimulation of the chondrogenic and osteogenic cells in the co-culture system together with the formation of an osteochondral-like tissue interface. Hence, the structural adaptability, suitable mechanical properties, and biological performance of the hierarchical scaffolds make these constructs a desired strategy for OC defect regeneration.

Preparation of gelatin hydrogel sponges incorporating bioactive glasses capable for the controlled release of fibroblast growth factor-2

Gelatin hydrogel sponges incorporating bioactive glasses (Gel-BG) were fabricated. We evaluated the characteristics of Gel-BG as scaffolds from the perspective of their mechanical properties and the formation of hydroxyapatite by the incorporation of bioactive glasses (BG). In addition, the Gel-BG degradation and the profile of fibroblast growth factor-2 (FGF-2) release from the Gel-BG were examined. Every Gel-BG showed an interconnected pore structure with the pore size range of 180-200 µm. The compression modulus of sponges incorporating BG increased. The time profiles of degradation for the 72-h crosslinked gelatin hydrogel sponges incorporating 10 wt% BG (Gel-BG(10)) and 50 wt% BG (Gel-BG(50)) were analogous to that of the 24-h crosslinked gelatin hydrogel sponge without BG (Gel-BG(0)). In measuring the release of FGF-2 from Gel-BG, the Gel-BG(10) and Gel-BG(50) showed almost analogous 100% cumulative release within 28 days in vivo. Additionally, a bioactivity evaluation showed that the presence of gelatin does not affect the in vitro bioactivity of Gel-BG. These sponges showed mechanical and chemical functionality as scaffolds, featuring both the controlled release of FGF-2 and the induction of hydroxyapatite crystallization.

A biomaterial with a channel-like pore architecture induces endochondral healing of bone defects

Biomaterials developed to treat bone defects have classically focused on bone healing via direct, intramembranous ossification. In contrast, most bones in our body develop from a cartilage template via a second pathway called endochondral ossification. The unsolved clinical challenge to regenerate large bone defects has brought endochondral ossification into discussion as an alternative approach for bone healing. However, a biomaterial strategy for the regeneration of large bone defects via endochondral ossification is missing. Here we report on a biomaterial with a channel-like pore architecture to control cell recruitment and tissue patterning in the early phase of healing. In consequence of extracellular matrix alignment, CD146+ progenitor cell accumulation and restrained vascularization, a highly organized endochondral ossification process is induced in rats. Our findings demonstrate that a pure biomaterial approach has the potential to recapitulate a developmental bone growth process for bone healing. This might motivate future strategies for biomaterial-based tissue regeneration.

Mesenchymal stem cells and porous β-tricalcium phosphate composites prepared through stem cell screen-enrich-combine(-biomaterials) circulating system for the repair of critical size bone defects in goat tibia

BACKGROUND

Efficacious bone substitute is essential for the treatment of a critical size bone defect. Currently, the bone substitutes commonly used in clinical practice lack osteogenic capacity and the therapeutic efficacy is not ideal. Herein, a novel stem cell screen-enrich-combine(-biomaterials) circulating system (SECCS) was introduced to provide the substitutes with osteogenic ability. The stem cell screening, enrichment, and recombination with substitutes could be integrated during the surgical operation. Using SECCS, the bioactive mesenchymal stem cells (MSCs) and porous β-tricalcium phosphate (β-TCP) composites (MSCs/β-TCP) were rapidly prepared for critical size bone defect repair and validated in goat models of critical size tibia defects.

METHODS

Twelve goats with right hind limb tibia defects of 30 mm were randomly divided into two groups: six (the experimental group) were treated with MSCs/β-TCP prepared by SECCS and the other six goats (the control group) were treated with pure porous β-TCP. The repair effect was assessed by x-ray, computed tomography (CT), micro-CT, histology and histomorphology 6 months after the operation. In addition, the enrichment efficacy of MSCs and the characteristics of the MSCs/β-TCP prepared by SECCS were evaluated.

RESULTS

The SECCS could compound about 81.3 ± 3.0% of the MSCs in bone marrow to the porous β-TCP without affecting the cell viability. The average number of MSCs for retransplantation was 27,655.0 ± 5011.6 for each goat from the experimental group. In vitro, satisfactory biocompatibility of the MSCs/β-TCP was performed, with the MSCs spreading adequately, proliferating actively, and retaining the osteogenic potential. In vivo, the defect repair by MSCs/β-TCP with good medullary cavity recanalization and cortical remodeling was significantly superior to that of pure porous β-TCP.

CONCLUSIONS

The MSCs/β-TCP prepared through SECCS demonstrated significant therapeutic efficacy in goat models of critical size bone defect. This provides a novel therapeutic strategy for critical size bone defects caused by severe injury, infection, and bone tumor resection with a high profile of safety, effectiveness, simplicity, and ease.

Bone Regeneration of Osteoporotic Vertebral Body Defects Using Platelet-Rich Plasma and Gelatin β-Tricalcium Phosphate Sponges

The objective of the present study was to investigate the effect of platelet-rich plasma (PRP) combined with gelatin β-tricalcium phosphate (β-TCP) sponge on bone generation in a lumbar vertebral body defect of ovariectomized rat. After creating critical-size defects in the center of the anterior vertebral body, the defects were filled with the following materials: (1) no material (control group), (2) gelatin β-TCP sponge with PRP (PRP sponge group), and (3) gelatin β-TCP sponge with phosphate-buffered saline (PBS sponge group). Microcomputed tomography and histological evaluation were performed immediately after surgery and at 4, 8, and 12 weeks to assess bone regeneration. Biomechanical test was also performed at postoperative week 12. In the PRP sponge group, both imaging and histological examination showed that visible osteogenesis was first induced and additional growth of bone tissue was observed in the transplanted sponge, compared with the PBS sponge group. There was no negative effect of either PRP sponge or PBS sponge transplantation on bone tissue generation around the periphery of the defect. Biomechanical test showed increased stiffness of the affected vertebral bodies in the PRP sponge group. These results indicate that PRP-impregnated gelatin β-TCP sponge is effective for facilitating bone regeneration in lumbar vertebral bone defect under osteoporotic condition. PRP combined with gelatin β-TCP sponges could be potentially useful for developing a new approach to vertebroplasty for osteoporotic vertebral fracture.

Treatment of osteomyelitis defects by a vancomycin-loaded gelatin/β-tricalcium phosphate composite scaffold

OBJECTIVE

In the present study, we aimed to assess whether gelatin/β-tricalcium phosphate (β-TCP) composite porous scaffolds could be used as a local controlled release system for vancomycin. We also investigated the efficiency of the scaffolds in eliminating infections and repairing osteomyelitis defects in rabbits.

METHODS

The gelatin scaffolds containing differing amounts of of β-TCP (0%, 10%, 30% and 50%) were prepared for controlled release of vancomycin and were labelled G-TCP0, G-TCP1, G-TCP3 and G-TCP5, respectively. The Kirby-Bauer method was used to examine the release profile. Chronic osteomyelitis models of rabbits were established. After thorough debridement, the osteomyelitis defects were implanted with the scaffolds. Radiographs and histological examinations were carried out to investigate the efficiency of eliminating infections and repairing bone defects.

RESULTS

The prepared gelatin/β-TCP scaffolds exhibited a homogeneously interconnected 3D porous structure. The G-TCP0 scaffold exhibited the longest duration of vancomycin release with a release duration of eight weeks. With the increase of β-TCP contents, the release duration of the β-TCP-containing composite scaffolds was decreased. The complete release of vancomycin from the G-TCP5 scaffold was achieved within three weeks. In the treatment of osteomyelitis defects in rabbits, the G-TCP3 scaffold showed the most efficacious performance in eliminating infections and repairing bone defects.

CONCLUSIONS

The composite scaffolds could achieve local therapeutic drug levels over an extended duration. The G-TCP3 scaffold possessed the optimal porosity, interconnection and controlled release performance. Therefore, this scaffold could potentially be used in the treatment of chronic osteomyelitis defects.Cite this article: J. Zhou, X. G. Zhou, J. W. Wang, H. Zhou, J. Dong. Treatment of osteomyelitis defects by a vancomycin-loaded gelatin/β-tricalcium phosphate composite scaffold. Bone Joint Res 2018;7:46-57. DOI: 10.1302/2046-3758.71.BJR-2017-0129.R2.

Gelatin positively regulates the immunosuppressive capabilities of adipose-derived mesenchymal stem cells

This characteristics of adipose-derived mesenchymal stem cells (Ad-MSCs) can be selectively enhanced by altering the culture environment. We evaluated the effects of gelatin on Ad-MSCs when used in combination with culture media. Ad-MSCs were initially cultured in 0%, 0.5%, 1%, 2%, and 4% gelatin in Dulbecco's modified Eagle's medium (DMEM) to evaluate cell proliferation. This expression of inflammatory, antiinflammatory, antioxidant, and osteogenic markers was then assessed by rtPCR in Ad-MSCs cultured in 0.5% gelatin in DMEM (GMSCs), and without gelatin (MSCs), for 5 and 10 days. We found that 0.5% gelatin significantly increased the proliferation rate of Ad-MSCs after 24 h of incubation, up until 72 h. GMSCs had upregulated IL-10, VEGF, and HO-1 after 5 and 10 days of incubation, while IL-6 and TNF-α were upregulated after 5 days and then significantly decreased after 10 days of incubation. The osteogenic factors BMP-7, AXIN, and β-catenin were significantly upregulated in GMSCs after 5 and 10 days. Notably, there was 5- to 8-fold higher expression of BMP-7 in GMSCs than in MSCs. We conclude that culture medium containing 0.5% gelatin enhances the proliferation rate, induces immunosuppression, and activates BMP-7 and the wnt/AXIN/β-catenin pathway in Ad-MSCs.

Development and Assessment of a 3D-Printed Scaffold with rhBMP-2 for an Implant Surgical Guide Stent and Bone Graft Material: A Pilot Animal Study

In this study, a new concept of a 3D-printed scaffold was introduced for the accurate placement of an implant and the application of a recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded bone graft. This preliminary study was conducted using two adult beagles to evaluate the 3D-printed polycaprolactone (PCL)/β-tricalcium phosphate (β-TCP)/bone decellularized extracellular matrix (bdECM) scaffold conjugated with rhBMP-2 for the simultaneous use as an implant surgical guide stent and bone graft material that promotes new bone growth. Teeth were extracted from the mandible of the beagle model and scanned by computed tomography (CT) to fabricate a customized scaffold that would fit the bone defect. After positioning the implant guide scaffold, the implant was placed and rhBMP-2 was injected into the scaffold of the experimental group. The two beagles were sacrificed after three months. The specimen block was obtained and scanned by micro-CT. Histological analysis showed that the control and experimental groups had similar new bone volume (NBV, %) but the experimental group with BMP exhibited a significantly higher bone-to-implant contact ratio (BIC, %). Within the limitations of this preliminary study, a 3D-printed scaffold conjugated with rhBMP-2 can be used simultaneously as an implant surgical guide and a bone graft in a large bone defect site. Further large-scale studies will be needed to confirm these results.