Rat Cranial Bone Defects Research Articles

Multiphoton imaging for quantification of mesenchymal stem cell survival and distribution in PEG granular hydrogel scaffolds post-implantation into rat cranial bone defects

Mesenchymal stem cells (MSCs) are promising candidates for cellular therapies aimed at promoting bone regeneration due to their secretory properties and osteoblastic differentiation capacity. However, typically < 5% of delivered MSCs are retained at the healing site within days of delivery via injection. In this work, granular PEG hydrogel scaffolds were used to deliver MSCs, labeled with fluorescent Quantum Dots, into critical-sized rat calvarial bone defects. The presence, survival, and distribution of MSCs within the hydrogel scaffold were evaluated with multiphoton microscopy at 3- and 7-days post-implantation. Additionally, endogenous cell infiltration into scaffolds was quantified, and markers for M1 and M2 macrophages were identified with immunohistochemistry. This multiphoton microscopy technique provides a quantitative analysis of exogenous MSC presence and survival and allows for micron-level spatial resolution of cell distribution throughout the implanted scaffolds. When ∼750,000 MSCs were implanted in a calvarial bone defect via PEG granular hydrogel scaffolds, ∼27% and ∼8% survived 3- and 7-days post-implantation, respectively. At 3- and 7-days post-implantation, exogenous MSCs and infiltrating endogenous cells, including M1 and M2 macrophages, were well distributed throughout the scaffolds. This multiphoton microscopy technique could be used to assess biomaterial delivery systems that can improve exogenous MSC presence and survival, facilitate endogenous cell infiltration, and investigate exogenous-endogenous cell interactions for bone regeneration therapies.

Injectable calcium phosphate cement integrated with BMSCs-encapsulated microcapsules for bone tissue regeneration

Injectable calcium phosphate cement (CPC) offers significant benefits for the minimally invasive repair of irregular bone defects. However, the main limitations of CPC, including its deficiency in osteogenic properties and insufficient large porosity, require further investigation and resolution. In this study, alginate-chitosan-alginate (ACA) microcapsules were used to encapsulate and deliver rat bone mesenchymal stem cells (rBMSCs) into CPC paste, while a porous CPC scaffold was established to support cell growth. Our results demonstrated that the ACA cell microcapsules effectively protect the cells and facilitate their transport into the CPC paste, thereby enhancing cell viability post-implantation. Additionally, the ACA + CPC extracts were found to stimulate osteogenic differentiation of rBMSCs. Furthermore, results from a rat cranial parietal bone defect model showed that ACA microcapsules containing exogenous rBMSCs initially improved thein situosteogenic potential of CPC within bone defects, providing multiple sites for bone growth. Over time, the osteogenic potential of the exogenous cells diminishes, yet the pores created by the microcapsules persist in supporting ongoing bone formation by recruiting endogenous cells to the osteogenic sites. In conclusion, the utilization of ACA loaded stem cell microcapsules satisfactorily facilitate osteogenesis and degradation of CPC, making it a promising scaffold for bone defect transplantation.

Mitochondria Transplantation to Bone Marrow Stromal Cells Promotes Angiogenesis During Bone Repair.

Angiogenesis is crucial for successful bone defect repair. Co-transplanting Bone Marrow Stromal Cells (BMSCs) and Endothelial Cells (ECs) has shown promise for vascular augmentation, but it face challenges in hostile tissue microenvironments, including poor cell survival and limited efficacy. In this study, the mitochondria of human BMSCs are isolated and transplanted to BMSCs from the same batch and passage number (BMSCsmito). The transplanted mitochondria significantly boosted the ability of BMSCsmito-ECs to promote angiogenesis, as assessed by in vitro tube formation and spheroid sprouting assays, as well as in vivo transplantation experiments in balb/c mouse and SD rat models. The Dll4-Notch1 signaling pathway is found to play a key role in BMSCsmito-induced endothelial tube formation. Co-transplanting BMSCsmito with ECs in a rat cranial bone defect significantly improves functional vascular network formation, and improve bone repair outcomes. These findings thus highlight that mitochondrial transplantation, by acting through the DLL4-Notch1 signaling pathway, represents a promising therapeutic strategy for enhancing angiogenesis and improving bone repair. Hence, mitochondrial transplantation to BMSCS as a therapeutic approach for promoting angiogenesis offers valuable insights and holds much promise for innovative regenerative medicine therapies.

HtrA3 paves the way for MSC migration and promotes osteogenesis

Mesenchymal stem cell (MSC) migration determines the healing capacity of bone and is crucial in promoting bone regeneration. Migration of MSCs is highly dependent on degradation of extracellular matrix by proteolytic enzymes. However, the underlying mechanisms of how enzymolysis paves the way for MSCs to migrate from their niche to the defect area is still not fully understood. Here, this study shows that high-temperature requirement A3 (HtrA3) overcomes the physical barrier and provides anchor points through collagen IV degradation, paving the way for MSC migration. HtrA3 is upregulated in MSCs at the leading edge of bone defect during the early stage of healing. HtrA3 degrades the surrounding collagen IV, which increases the collagen network porosity and increases integrin β1 expression. Subsequently, integrin β1 enhances the mechanotransduction of MSCs, thus remodeling the cytoskeleton, increasing cellular stiffness and nuclear translocation of YAP, eventually promoting the migration and subsequent osteogenic differentiation of MSCs. Local administration of recombinant HtrA3 in rat cranial bone defects significantly increases new bone formation and further validates the enhancement of MSC migration. This study helps to reveal the novel roles of HtrA3, explore potential targets for regenerative medicine, and offer new insights for the development of bioactive materials.

A Composite Hydrogel Functionalized by Borosilicate Bioactive Glasses and VEGF for Critical-Size Bone Regeneration.

Critical-size bone defects pose a formidable challenge in clinical treatment, prompting extensive research efforts to address this problem. In this study, an inorganic-organic multifunctional composite hydrogel denoted as PLG-g-TA/VEGF/Sr-BGNPs is developed, engineered for the synergistic management of bone defects. The composite hydrogel demonstrated the capacity for mineralization, hydroxyapatite formation, and gradual release of essential functional ions and vascular endothelial growth factor (VEGF) and also maintained an alkaline microenvironment. The composite hydrogel promoted the proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs), as indicated by increased expression of osteogenesis-related genes and proteins in vitro. Moreover, the composite hydrogel significantly enhanced the tube-forming capability of human umbilical vein endothelial cells (HUVECs) and effectively inhibited the process of osteoblastic differentiation of nuclear factor kappa-B ligand (RANKL)-induced Raw264.7 cells and osteoclast bone resorption. After the implantation of the composite hydrogel into rat cranial bone defects, the expression of osteogenic and angiogenic biomarkers increased, substantiating its efficacy in promoting bone defect repair in vivo. The commendable attributes of the multifunctional composite hydrogel underscore its pivotal role in expediting hydrogel-associated bone growth and repairing critical bone defects, positioning it as a promising adjuvant therapy candidate for large-segment bone defects.

Dimethyloxallyl glycine-loaded mesoporous bioactive glass/poly(D,L-lactide) composite scaffolds with ultrasound stimulation for promoting bone repair.

Introduction: Bone tissue engineering is considered the ideal approach for bone repair. Mesoporous bioactive glass (MBG) possesses the characteristics of high drug-loading capacity and bioactivity. Low-intensity pulsed ultrasound contributes to promoting fracture healing and bone defect repair, and dimethyloxalyl glycine (DMOG) is a small molecular inhibitor that can suppress prolyl hydroxylase, reducing the degradation of hypoxia-inducible factor. Methods: In this study, we proposed to prepare DMOG-loaded MBG/poly(D,L-lactide) composite scaffolds (DMOG-MBG/PDLLA) for promoting bone repair. The effects of ultrasound stimulation and DMOG release on the cell responses of rat bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) and bone repair in vivo were investigated. Results and Discussion: The results showed that both ultrasound stimulation and DMOG release could promote the proliferation, adhesion and differentiation of BMSCs and HUVECs, respectively. After the implantation of scaffolds in rat cranial bone defect model for 8 weeks, the results indicated that the combined ultrasound stimulation and DMOG release contributed to the highest ability for promoting bone repair. Hence, the DMOG-MBG/PDLLA scaffolds with ultrasound stimulation are promising for application in bone repair.

Amyloid Fibril and Clay Nanosheet Dual-Nanoengineered DNA Dynamic Hydrogel for Vascularized Bone Regeneration.

Dynamic hydrogels have attracted enormous interest for bone tissue engineering as they demonstrate reversible mechanics to better mimic biophysical cues of natural extracellular matrix (ECM) compared to traditional static hydrogels. However, the facile development of therapeutic dynamic hydrogels that simultaneously recapitulate the filamentous architecture of the ECM of living tissues and induce both osteogenesis and angiogenesis to augment vascularized bone regeneration remains challenging. Herein, we report a dual nanoengineered DNA dynamic hydrogel developed through the supramolecular coassembly of amyloid fibrils and clay nanosheets with DNA strands. The nanoengineered ECM-like fibrillar hydrogel network is facilely formed without a complicated and tedious molecular synthesis. Amyloid fibrils together with clay nanosheets synergistically enhance the mechanical strength and stability of the dynamic hydrogel and, more remarkably, endow the matrix with an array of tunable features, including shear-thinning, injectability, self-healing, self-supporting, and 3D printable properties. The QK peptide is further chemically grafted onto amyloid fibrils, and its sustainable release from the hydrogel matrix stimulates the tube formation and migration with human umbilical vein endothelial cells. Meanwhile, the nanoengineered hydrogel matrix promotes osteogenic differentiation of bone marrow mesenchymal stem cells due to the sustainable release of Si4+ and Mg2+ derived from clay nanosheets. Furthermore, the manipulation of enhanced vascularized bone regeneration by the dynamic hydrogel is revealed in a rat cranial bone defect model. This dual nanoengineered strategy envisions great promise in developing therapeutic dynamic hydrogels for improved and customizable bone regeneration.

Feather keratin-montmorillonite nanocomposite hydrogel promotes bone regeneration by stimulating the osteogenic differentiation of endogenous stem cells

Bone defects caused by bone trauma, infection, surgery, or other systemic diseases remain a severe challenge for the medical field. To address this clinical problem, different hydrogels were exploited to promote bone tissue regrowth and regeneration. Keratins are natural fibrous proteins found in wool, hair, horns, nails, and feather. Due to their unique characteristics of outstanding biocompatibility, great biodegradability, and hydrophilic, keratins have been widely applicated in different fields. In our study, the feather keratin-montmorillonite nanocomposite hydrogels that consist of keratin hydrogels serving as the scaffold support to accommodate endogenous stem cells and montmorillonite is synthesized. The introduction of montmorillonite greatly improves the osteogenic effect of the keratin hydrogels via bone morphogenetic protein 2 (BMP-2)/phosphorylated small mothers against decapentaplegic homolog 1/5/8 (p-SMAD 1/5/8)/runt-related transcription factor 2 (RUNX2) expression. Moreover, the incorporation of montmorillonite into hydrogels can improve the mechanical properties and bioactivity of the hydrogels. The morphology of feather keratin-montmorillonite nanocomposite hydrogels was shown by scanning electron microscopy (SEM) to have an interconnected porous structure. The incorporation of montmorillonite into the keratin hydrogels was confirmed by the energy dispersive spectrum (EDS). We prove that the feather keratin-montmorillonite nanocomposite hydrogels enhance the osteogenic differentiation of BMSCs. Furthermore, micro-CT and histological analysis of rat cranial bone defect demonstrated that feather keratin-montmorillonite nanocomposite hydrogels dramatically stimulated bone regeneration in vivo. Collectively, feather keratin-montmorillonite nanocomposite hydrogels can regulate BMP/SMAD signaling pathway to stimulate osteogenic differentiation of endogenous stem cells and promote bone defect healing, indicating their promising candidate in bone tissue engineering.

3D-Printed Bioactive Scaffold Loaded with GW9508 Promotes Critical-Size Bone Defect Repair by Regulating Intracellular Metabolism.

The process of bone regeneration is complicated, and it is still a major clinical challenge to regenerate critical-size bone defects caused by severe trauma, infection, and tumor resection. Intracellular metabolism has been found to play an important role in the cell fate decision of skeletal progenitor cells. GW9508, a potent agonist of the free fatty acid receptors GPR40 and GPR120, appears to have a dual effect of inhibiting osteoclastogenesis and promoting osteogenesis by regulating intracellular metabolism. Hence, in this study, GW9508 was loaded on a scaffold based on biomimetic construction principles to facilitate the bone regeneration process. Through 3D printing and ion crosslinking, hybrid inorganic-organic implantation scaffolds were obtained after integrating 3D-printed β-TCP/CaSiO3 scaffolds with a Col/Alg/HA hydrogel. The 3D-printed β-TCP/CaSiO3 scaffolds had an interconnected porous structure that simulated the porous structure and mineral microenvironment of bone, and the hydrogel network shared similar physicochemical properties with the extracellular matrix. The final osteogenic complex was obtained after GW9508 was loaded into the hybrid inorganic-organic scaffold. To investigate the biological effects of the obtained osteogenic complex, in vitro studies and a rat cranial critical-size bone defect model were utilized. Metabolomics analysis was conducted to explore the preliminary mechanism. The results showed that 50 μM GW9508 facilitated osteogenic differentiation by upregulating osteogenic genes, including Alp, Runx2, Osterix, and Spp1 in vitro. The GW9508-loaded osteogenic complex enhanced osteogenic protein secretion and facilitated new bone formation in vivo. Finally, the results from metabolomics analysis suggested that GW9508 promoted stem cell differentiation and bone formation through multiple intracellular metabolism pathways, including purine and pyrimidine metabolism, amino acid metabolism, glutathione metabolism, and taurine and hypotaurine metabolism. This study provides a new approach to address the challenge of critical-size bone defects.

BMP-2@PNH-TA hydrogel with osteogenic and antibacterial properties for integrated photothermal therapy

Progress toward developing next-generation biomaterials applied in complex bone defect is expected to effectively integrate osteogenic and anti-bacteria capability. However, current biomaterials often achieve the two functions separately. Inspired by photothermal effect, exogenous light-induced thermal variations can efficiently facilitate bone regeneration and bacteria eradication. Here, a bioactive hydrogel BMP-2@PNH-TA with simultaneously osteogenic and anti-bacterial capacities is presented, which is based on the near infrared (NIR) induced photothermal effect to perform integrated photothermal therapy (PTT). In detail, photothermal effect and photothermal-controlled release of osteogenic and anti-bacterial factors through sponge-like effect could exert integrated influence on bone regeneration under complex situation. The composite hydrogel can mediate pro-osteogenesis under mild temperature and controlled release of BMP-2 and tannin in response to NIR stimulation with low power, while efficiently eradicate bacteria via controlled release of O-HACC and thermal effect with high power. The customized PTT strategy significantly shortened the duration time of bone regeneration up to almost 50% in rat cranial bone defect. It is anticipated that the concept of integrated PTT for bone regeneration will cast new insights into developing high-performance therapeutic strategy with combined biological functions.

Phosphoserine-loaded chitosan membranes promote bone regeneration by activating endogenous stem cells.

Bone defects that result from trauma, infection, surgery, or congenital malformation can severely affect the quality of life. To address this clinical problem, a phosphoserine-loaded chitosan membrane that consists of chitosan membranes serving as the scaffold support to accommodate endogenous stem cells and phosphoserine is synthesized. The introduction of phosphoserine greatly improves the osteogenic effect of the chitosan membranes via mutual crosslinking using a crosslinker (EDC, 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide). The morphology of PS-CS membranes was shown by scanning electron microscopy (SEM) to have an interconnected porous structure. The incorporation of phosphoserine into chitosan membranes was confirmed by energy dispersive spectrum (EDS), Fourier Transforms Infrared (FTIR), and X-ray diffraction (XRD) spectrum. The CCK8 assay and Live/Dead staining, Hemolysis analysis, and cell adhesion assay demonstrated that PS-CS membranes had good biocompatibility. The osteogenesis-related gene expression of BMSCs was higher in PS-CS membranes than in CS membranes, which was verified by alkaline phosphatase (ALP) activity, immunofluorescence staining, and real-time quantitative PCR (RT-qPCR). Furthermore, micro-CT and histological analysis of rat cranial bone defect demonstrated that PS-CS membranes dramatically stimulated bone regeneration in vivo. Moreover, H&E staining of the main organs (heart, liver, spleen, lung, or kidney) showed no obvious histological abnormalities, revealing that PS-CS membranes were no additional systemic toxicity in vivo. Collectively, PS-CS membranes may be a promising candidate for bone tissue engineering.

Self-Prepared Hyaluronic Acid/Alkaline Gelatin Composite with Nano-Hydroxyapatite and Bone Morphogenetic Protein for Cranial Bone Formation.

New bone-forming substitute materials are highly useful in dental implantology. The purpose of this study was to prepare cross-linked hyaluronic acid (cHLA)/cross-linked alkaline gelatin (cAG)/nano-hydroxyapatite (nHAp)/bone morphogenic protein (BMP) constructs; and evaluate their bone-forming capabilities in rat cranial bone defects. The cHLA and cAG liquids processed with an epoxy cross-linker were blended with a 3:1 volume ratio, followed by freeze-drying. The dry composites were further infiltrated with water containing nHAp only (BMP (-)) or with water containing nHAp and BMP (BMP (+)). Prepared wet constructs (BMP (-) and BMP (+)) were implanted in rat cranial bone defects, while defects only were also made, and animals were fed for 8 weeks, followed by subsequent soft X-ray measurements and histological observations. The X-ray results showed that BMP (+) constructs disappeared, though caused inward extension of peripherical bone from defect edges with an increase in length of approximately 24%, larger than those of BMP (-) constructs and defect only with approximately 17% and 8% increments, respectively (p &lt; 0.05). Histological observations of BMP (+) construct samples clearly indicated active bone extension consisting of an array of island-like bones. It was concluded that cHLA/cAG/nHAp/BMP could be used as novel bone-substitute materials.

Preparation of Collagen/Hydroxyapatite Composites Using the Alternate Immersion Method and Evaluation of the Cranial Bone-Forming Capability of Composites Complexed with Acidic Gelatin and b-FGF.

Bone-substitute materials are essential in dental implantology. We prepared collagen (Col)/hydroxyapatite (Hap)/acidic gelatin (AG)/basic fibroblast growth factor (b-FGF) constructs with enhanced bone-forming capability. The Col/Hap apatite composites were prepared by immersing Col sponges alternately in calcium and phosphate ion solutions five times, for 20 and 60 min, respectively. Then, the sponges were heated to 56 °C for 48 h. Scanning electron microscopy/energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analyses showed that the Col/Hap composites contained poorly crystalline Hap precipitates on the Col matrix. Col/Hap composite granules were infiltrated by AG, freeze-dried, and immersed in b-FGF solution. The wet quaternary constructs were implanted in rat cranial bone defects for 8 weeks, followed by soft X-ray measurements and histological analysis. Animal studies have shown that the constructs moderately increase bone formation in cranial bone defects. We found that an alternate immersion time of 20 min led to the greatest bone formation (p &lt; 0.05). Constructs placed inside defects slightly extend the preexisting bone from the defect edges and lead to the formation of small island-like bones inside the defect, followed by disappearance of the constructs. The combined use of Col, Hap, AG, and b-FGF might bring about novel bone-forming biomaterials.

Tissue engineered bone via templated hBMSCs mineralization and its application for bone repairing.

To develop bone implants, a novel tissue-engineered bone was constructed via templated human bone mesenchymal stem cells (hBMSCs) mineralization. Firstly, an osteoid-like template (Os-template) with aligned collagen fibers was prepared and followed by seeding hBMSCs to mimic the process of bone formation. After being cultured over weeks, the cells produced collagen fibers in an orderly aligned osteomorphic fashion. Further, a novel tissue-engineered bone with mineralized collagen fiber (mOs-ECM) was subsequently achieved after cell mineralization, showing a high degree of osteomimicry in terms of both composition and structure. When applied to the rat cranial bone defect model, the mOs-ECM significantly promoted the new bone formation and fused with the host bone. The study indicated that microscopic cell mineralization could be guided by artificially designed templates and successfully fabricated a macroscopic implant with a pronounced effect on bone repairing.

Vascular Endothelial Growth Factor Mimetic Peptide and Parathyroid Hormone (1-34) Delivered via a Blue-Light-Curable Hydrogel Synergistically Accelerate Bone Regeneration.

Safe and effective biomaterials are in urgent clinical need for tissue regeneration and bone repair. While numerous advances have been made on hydrogels promoting osteogenesis in bone formation, co-stimulation of the angiogenic pathways in this process remains to be exploited. Here, we have developed a gelatin-based blue-light-curable hydrogel system, functionalized with an angiogenic vascular endothelial growth factor (VEGF) mimetic peptide, KLTWQELYQLKYKGI (KLT), and an osteoanabolic peptide, parathyroid hormone (PTH) 1-34. We have discovered that the covalent modification of gelatin scaffold with peptides can modulate the physical properties and biological activities of the produced hydrogels. Furthermore, we have demonstrated that those two peptides orchestrate synergistically and promote bone regeneration in a rat cranial bone defect model with remarkable efficacy. This dual-peptide-functionalized hydrogel system may serve as a promising lead to functional biomaterials in bone repair and tissue engineering.

Preparation of photothermal-sensitive PDGF@ZIF-8-PDA@COL/PLGA-TCP composite scaffolds for bone defect repair

The repair of bone defects has long been a challenging and significant health question. Here, collagen hydrogel incorporating platelet-derived growth factor (PDGF)-loaded photopolymerizable ZIF-8-PDA nanoparticles (PDGF@ZIF-8-PDA@COL hydrogel) was prepared and perfused into 3D printed poly (lactide-co-glycolide)-tricalcium phosphate (PLGA-TCP) scaffolds. The resulting PDGF@ZIF-8-PDA@COL/PLGA-TCP composite scaffolds were applied as a bone substitute for cranial bone defect repair. The photopolymerizable ZIF-8-PDA nanoparticles had a mean size of 226.2 ± 5.3 nm with photothermal conversion capacity. PDGF@ZIF-8-PDA@COL/PLGA-TCP composite scaffolds showed a slower release of PDGF compared to PDGF release from collagen hydrogels. The composite scaffolds exhibited excellent antibacterial properties and good in vitro osteoconductive capacity. The osteoconductive activities of PDGF@ZIF-8-PDA@COL/PLGA-TCP composite scaffolds were also investigated in a rat cranial bone defect model in vivo by micro-CT imaging, hematoxylin and eosin staining, Masson’s trichrome staining, and immunohistochemical staining of osteogenesis-related markers. The PDGF@ZIF-8-PDA@COL/PLGA-TCP composite scaffolds accelerated cranial bone formation and gradually degraded over time. All these results provided strong evidence that PDGF@ZIF-8-PDA@COL/PLGA-TCP composite scaffolds might be a promising system for bone defect repair.

MBG/ PGA-PCL composite scaffolds provide highly tunable degradation and osteogenic features

It remains a challenge to achieve satisfactory balance between biodegradability and osteogenic capacity in biosynthetic bone grafts. In this study, we aimed to address this challenge by incorporating mesoporous bioactive glass (MBG) into poly(caprolactone-co-glycolide) (PGA-PCL) at gradient ratios. MBG/PGA-PCL (PGC/M) scaffolds with MBG incorporation ratio at 0, 10%, 25% and 40% (PGC/M0-40) were synthesized using a modified solvent casting-particulate leaching method, and their physiochemical and biological properties were comprehensively evaluated. PGC/M scaffolds exhibited highly perforated porous structure with a large-pore size of 300–450 μm, with ordered MBGs of around 6.0 nm mesopores size uniformly dispersed. The increase in MBG incorporation ratio significantly improved the scaffold surface hydrophilicity, apatite-formation ability and pH stability, increased the weight loss rate while insignificantly influenced the molecular chains degradation of PGA-PCL component, and facilitated the attachment, spreading, viability and proliferation of rat bone marrow stromal cells (rBMSCs) on scaffolds. Moreover, rBMSCs cultured on PGC/M10-40 scaffolds demonstrated enhanced ALP activity and osteogenesis-related gene expression in a MBG dose-dependent manner as compared with those cultured on PGC/M0 scaffolds. When implanted to the rat cranial bone defect, PGC/M25 and PGC/M40 scaffolds induced significantly better bone repair as compared to PGC/M0 and PGC/M10 scaffolds. Besides, the biodegradability of PGC/M scaffolds correlated with the MBG incorporation ratio. These data suggested this novel PGC/M scaffolds as promising bone repair biomaterial with highly tunable hydrophilicity, bioactivity, cytocompatibility, osteogenic activity as well as biodegradability.

Bioactive gelatin cryogels with BMP‐2 biomimetic peptide and VEGF: A potential scaffold for synergistically induced osteogenesis

A poor biocompatibility and bioactivity of invasive materials remains major problems for biomaterial-based therapy. In this study, we introduced gelatin scaffolds carrying both bone morphogenetic protein-2 (BMP-2) biomimetic peptide and vascular endothelial growth factor-165 (VEGF) that achieved controlled release, cell attachment, proliferation and differentiation. To promote osteogenesis with VEGF, we designed the BMP-2 biomimetic peptide that comprised BMP-2 core sequence oligopeptide (SSVPT), phosphoserine, and synthetic cell adhesion factor (RGDS). In vitro cell experiments, the scaffold was conducive to the adhesion and proliferation of rat bone marrow mesenchymal stem cells (rBMSCs). The micro-CT 3D reconstruction of the rat cranial bone defect model showed that bone regeneration patterns occurred from one side edge towards the center area implanted with the prepared cryogel, and tissue section staining analysis demonstrated that the scaffold with double-growth factor can synergistically accelerate bone regeneration. These findings suggested that the obtained gelatin cryogel could serve as a cell-responsive platform for biomaterial-based nonbearing bone repair.

Bone Tissue Regeneration by Collagen Scaffolds with Different Calcium Phosphate Coatings: Amorphous Calcium Phosphate and Low-Crystalline Apatite.

Surface-mineralized collagen sponges have attracted much attention as scaffolds for bone tissue engineering. Recently, we developed amorphous calcium phosphate (ACP) and low-crystalline apatite coating processes on collagen sponges. In the present study, we applied these coating processes to granular collagen sponges (referred to as Col) to compare the bone tissue regeneration capabilities of ACP-coated and apatite-coated Col (referred to as Col-ACP and Col-Ap, respectively) using a rat cranial bone defect model. According to micro-CT and histological analyses, Col-Ap enhanced bone tissue regeneration compared to Col, whereas Col-ACP did not. These results not only demonstrated the superior bone tissue regeneration capability of Col-Ap, but also indicated limitations of the in vitro simulated body fluid (SBF) test used in our previous study. Despite the apatite-forming ability of Col-ACP in SBF, it was ineffective in improving bone tissue regeneration in vivo, unlike Col-Ap, most likely due to the quick resorption of the ACP coating in the defect site. The present results clarified the importance of the coating stability in vivo and revealed that the low-crystalline apatite coating was more beneficial than the ACP coating in the fabrication of surface-mineralized collagen sponges for use as bone tissue engineering scaffolds.

Biomaterials with structural hierarchy and controlled 3D nanotopography guide endogenous bone regeneration.

Biomaterials without exogenous cells or therapeutic agents often fail to achieve rapid endogenous bone regeneration with high quality. Here, we reported a class of three-dimensional (3D) nanofiber scaffolds with hierarchical structure and controlled alignment for effective endogenous cranial bone regeneration. 3D scaffolds consisting of radially aligned nanofibers guided and promoted the migration of bone marrow stem cells from the surrounding region to the center in vitro. These scaffolds showed the highest new bone volume, surface coverage, and mineral density among the tested groups in vivo. The regenerated bone exhibited a radially aligned fashion, closely recapitulating the scaffold's architecture. The organic phase in regenerated bone showed an aligned, layered, and densely packed structure, while the inorganic mineral phase showed a uniform distribution with smaller pore size and an even distribution of stress upon the simulated compression. We expect that this study will inspire the design of next-generation biomaterials for effective endogenous bone regeneration with desired quality.