Defect Model Research Articles

Low-Intensity Pulsed Ultrasound Responsive Scaffold Promotes Intramembranous and Endochondral Ossification via Ultrasonic, Thermal, and Electrical Stimulation.

Multiple physical stimuli are expected to produce a synergistic effect to promote bone tissue regeneration. Low-intensity pulsed ultrasound (LIPUS) has been clinically used in bone repair for the mechanical stimulation that it provides. In addition, LIPUS can also excite the biomaterials to generate other physical stimuli such as thermal or electrical stimuli. In this study, a scaffold based on decellularized adipose tissue (DAT) is established by incorporating polydopamine-modified multilayer black phosphorus nanosheets (pDA-mBP@DAT). Their effect on bone repair under LIPUS stimulation and the potential mechanisms are further investigated. This scaffold possesses piezoelectric properties and generates a mild thermogenic stimulus when stimulated by LIPUS. With superior properties, this scaffold is demonstrated to have good cytocompatibility in vitro and in vivo. Simultaneously, LIPUS promotes cell attachment, migration, and osteogenic differentiation in the pDA-mBP@DAT scaffold. Furthermore, the combined use of pDA-mBP@DAT and LIPUS significantly affects the regenerative effect in rat models of critical-sized calvarial defects. The possible mechanisms include promoting osteogenesis and neovascularization and activating the Piezo1. This study presents insight into speeding up bone regeneration by the synergistic combination of LIPUS and pDA-mBP@DAT scaffolds.

Prediction Model for Flake Line Defects in Metallic Injection Molding: Considering Skin-Core Velocity and Alignment.

Metallic injection molding combines aluminum flake metallic pigments with polymers to directly produce components with metallic luster, improving production efficiency and reducing environmental impact. However, flake line defects that occur in regions where ribs or flow paths intersect remain a significant challenge. This study proposes a velocity model that considers the flow characteristics between the surface and core layers and an alignment model that incorporates the orientation of aluminum flakes to predict appearance defects. Through this approach, the mechanisms of appearance defect formation were systematized, and the appearance defects caused by flow velocity differences between the surface and core layers, flake alignment uniformity, and reflection angles were visualized. Both prediction models demonstrated a 50% prediction accuracy, successfully identifying two out of four observed defects. This research addresses the limitations of previous prediction methods, which only considered the surface layer, by introducing a novel approach that accounts for the core layer. It is expected to contribute to reducing defects and improving quality in industries requiring high-quality metallic appearances.

An injectable multi-functional composite bioactive hydrogel for bone regeneration via immunoregulatory and osteogenesis effects

Bone defects represent a prevalent and significant challenge in clinical practice. Given the inflammatory microenvironment at injury sites and the requirement for endogenous cell and tissue infiltration, there is an urgent need for an ideal biomaterial that can modulate inflammation and promote bone regeneration. We developed an innovative injectable hydrogel (CH@PUE&MSN) designed for immunomodulation and bone regeneration through in situ self-assembly, incorporating puerarin and chitosan with mesoporous silica nanoparticles. In vitro experiments demonstrated that this multifunctional injectable hydrogel promotes tissue cell regeneration, reduces inflammation, inhibits osteoclast formation, induces the migration and differentiation of bone marrow mesenchymal stem cells, and facilitates bone regeneration. Furthermore, we conducted an extensive in vivo evaluation using a bone defect model, employing advanced imaging and histological analyses. Our findings indicate that this multifunctional injectable hydrogel is a promising bioactive material for bone regeneration and presents a novel strategy for the clinical management of bone defects.

Isogenic Transplantation of Hybrid Artificial Pleural Tissue Consisting of Rat Cells and Polyglycolic Acid Nanofiber Sheet Induces Restoration of Mesothelial Defects in Rat Model.

Impairment of the visceral pleura following thoracic surgery often leads to air leaks and intrathoracic adhesions. For preventing such complications, mesothelial cell proliferation at the pleural defects can be effective. To develop new materials for pleural defects restoration, we constructed a hybrid artificial pleural tissue (H-APLT) combining polyglycolic acid (PGA) nanofiber sheets with a three-dimensional culture of mesothelial cells and fibroblasts and evaluated its therapeutic efficacy in a rat pleural defect model. After rat lungs were harvested, pleural mesothelial cells and lung fibroblasts were cultured separately. To construct H-APLT, the cells were then coated with multiple layers of fibronectin and gelatin, followed by a single layer of mesothelial cells on top of multiple layers of fibroblasts accumulated onto a collagen-coated PGA nanofiber sheet. Left lateral thoracotomy was performed, and H-APLTs were transplanted into a rat model with pleural defects (N = 8). After 2-12 weeks of transplantation, lung resection and histological analyses were performed. H-APLTs exhibited a pleural structure with a highly integrated mesothelial layer invitro. After transplantation, all eight rats survived until sacrifice. At 12 weeks post-transplantation, the mesothelial layer on the lung surface was observed to be without defects with no intrathoracic adhesions detected. Successful isogenic engraftment of H-APLTs was achieved in a rat model of pleural defects. The combination of accumulated fibroblasts and collagen-coated PGA nanofiber sheets contributed to the maintenance of the mesothelial layer's structure and function, potentially preventing air leaks and intrathoracic adhesions.

Coixol-Loaded Hydrogels Promote Osteochondral Defect Repair via Modulation of Ferroptosis and Autophagy in Chondrocytes.

Osteoarthritis (OA) is a chronic multifactorial disease characterized by cartilage degeneration, pain, and reduced mobility. Current therapies primarily aim to relieve pain and restore function, but they often have limited effectiveness and side effects. Coixol, a bioactive compound from Coix lacryma-jobi L., exhibits anti-inflammatory and analgesic properties, suggesting potential benefits in OA treatment. This study explored the effects of coixol on OA chondrocytes. Primary chondrocytes from OA rats were isolated and treated with varying concentrations of coixol. Cell viability and proliferation were assessed by using CCK-8 assays. The expression of genes related to ferroptosis and autophagy was analyzed through RT-qPCR, Western blot, and immunofluorescence. Moreover, the study investigated the characteristics and performance of coixol-loaded PDLLA-PEG-PDLLA (PLEL)/gelatin sponge (GS) hydrogels (Coixol@PLEL/GS) for enhancing osteochondral defect repair by specifically targeting chondrocyte ferroptosis and autophagy. The characteristics of coixol-loaded PDLLA-PEG-PDLLA/gelatin sponge (Coixol@PLEL/GS) hydrogels were evaluated using cryo-scanning electron microscopy (SEM) or SEM, and coixol release kinetics were determined. In vivo, a rat osteochondral defect model was used to assess the efficacy of Coixol@PLEL/GS in osteochondral defect repair using International Cartilage Repair Society (ICRS) scores, Safranin O/Fast green staining, Toluidine blue staining, and immunofluorescence. Coixol significantly increased the viability and proliferation of OA chondrocytes in a dose-dependent manner. Furthermore, coixol inhibited ferroptosis and stimulated autophagy, as evidenced by the upregulation of related genes. In vivo, Coixol@PLEL/GS remarkably enhanced the repair of osteochondral defects compared to that of control groups. In conclusion, coixol protects OA chondrocytes by improving survival, inhibiting ferroptosis, and activating autophagy, highlighting its potential as a therapeutic strategy for OA treatment.

Biomechanically inspired composite hydrogel bioink enhances engineered cartilage formation

Current therapies for articular cartilage defects or degeneration (osteoarthritis) remain unsatisfactory. There are significant clinical demands for the development of more efficient approaches to enhance the repair or regeneration of articular cartilage lesions. In this study, a newly defined alginate-gelatin (A-G) composite bioink was synthesized using the carbodiimide chemistry crosslinking method. Then, the dual-crosslinking (DC) bioscaffolds containing both chemical and ionic networks were fabricated by 3D-bioprinting technique and Ca2+ treatment. The optimized networks formed in the DC bioscaffolds provided a desirable Young’s modulus and geometric constraints, which were superior to that of the single-crosslinking (SC) control group to mimic the mechanical properties of the pericellular matrix (PCM) of native articular cartilage. Chondrocytes exhibited above 95% viability and higher proliferation rate in the 3D printed A-G-DC bioscaffolds than in the alginate-only group after 7 days in vitro culture. Chondrogenic differentiation in vitro was improved in the A-G-DC bioscaffolds than that of the alginate-only group, indexed by upregulation of chondrogenic marker gene expression including Sox9, Col2a1, Comp and Aggrecan. In the subcutaneous transplantation model and osteochondral defect model in mice with severe combined immunodeficiency (SCID), the A-G-DC bioscaffolds exhibited enhanced chondrogenesis and repair capacity than the alginate-only or none-implant control group, characterized by the increased expression of SOX9 and collagen type II (Col II) and higher ICRS II scores, respectively. These findings demonstrated that the biomechanically inspired A-G composite bioink and the 3D-printed A-G-DC bioscaffolds possess excellent cell biocompatibility, satisfactory biomechanical properties and chondrogenesis promotion capacity, which have the potential to be applied to enhance cartilage regeneration for patients with articular cartilage lesions.

3D Printed Titanium Scaffolds with Bi-Directional Gradient QK-Functionalized Surface.

3D printed titanium scaffold has promising applications in orthopedics. However, the bioinert titanium presents challenges for promoting vascularization and tissue growth within the porous scaffold for stable osteointegration. In this study, a modular porous titanium scaffold is created using 3D printing and a gradient-surface strategy to immobilize QK peptide on the surface with a bi-directional gradient distribution. This design featured high peptide density in the interior and low peptide density on both ends, aiming to induce cell migration from ends to interior and subsequently enhance vascularization and osteointegration within the scaffold. In vitro results showed that besides the inherent bioactivity, the gradient distribution of QK positively correlated with endothelial cell migration and promoted angiogenesis. In vivo assay was performed by a segmental bone defect model in rabbit and a spine repair model in sheep. Various staining and Micro-CT results demonstrated that compared to that with uniformly QK-functionalized surface, the scaffold with bi-directional gradient QK-functionalized surface (Ti-G) significantly encouraged new tissue growth toward the interior of the scaffold, subsequently facilitated angiogenesis and osteointegration. This study provides an effective strategy for enhancing the bioactivity of peptide-functionalized scaffolds through the concept of bi-directional gradients, and holds potential for various 3D printed scaffolds.

Kartogenin Enhances Chondrogenic Differentiation of iPSC Derived MSCs (iMSCs) and Improves Outcomes in an Osteochondral Defect Model in Male Rats.

Osteochondral defects (OCD) pose a significant clinical challenge due to the limited self-repair capacity of cartilage, leading to pain, joint dysfunction, and progression to osteoarthritis. Cellular implantations of adult mesenchymal stem cells (MSCs) enhanced with treatment of factors, such as small molecule Kartogenin (KGN) to promote chondrogenic differentiation, are promising but these cells often encounter hypertrophy during differentiation, compromising long-term stability. Induced pluripotent stem cell-derived MSCs (iMSCs) offer greater proliferative and differentiation capacity than MSCs and may provide a superior source of cells for cartilage repair. We hypothesized that treatment of iMSCs with TGFβ3 and KGN would enhance chondrogenic differentiation and that implanting these pellets into a rat OCD model would promote de novo cartilage regeneration and reduce pain behavior. We pellet cultured iMSCs derived from articular chondrocytes and treated with various conditions of TGFβ3 and KGN. We then assessed the in vivo performance of the pellets using a trochlear osteochondral defect in male Lewis rats. Co-treatment of iMSC pellets with TGFβ3 and KGN showed more pronounced chondrogenic differentiation than sequential treatment and exhibited stronger expression of chondrogenic genes. Implantation of the TGFβ3/KGN-treated iMSC pellets into OCD resulted in modest repair, as observed via gross morphology, effectively prevented the onset of joint hyperalgesia, and helped to maintain normal gait out to 12 weeks post-implantation compared to untreated OCD rats. Our study highlights the potential of KGN to enhance iMSC pellet chondrogenesis, offering a scaffold-free, cell-based therapy that could simplify clinical translation and improve outcomes for patients with cartilage injuries.

Histone Demethylase KDM6B Promotes Chondrogenic Differentiation Potential of Stem Cells from the Apical Papilla Via HES1.

Mesenchymal stem cell (MSC)-based therapies have emerged as a promising approach for treating articular cartilage injuries. However, enhancing the chondrogenic differentiation potential of MSCs remains a significant challenge. KDM6B, a histone demethylase that specifically removes H3K27me3 marks, is essential in controlling the maturation of chondrocytes. In this study, we examined how KDM6B influences chondrogenic differentiation in SCAPs and investigated the underlying mechanisms involved. SCAPs were utilized. Alcian Blue staining, pellet culture, and cell transplantation in rabbit knee cartilage defect models assessed MSC chondrogenic differentiation. Western blot, Real-time RT-PCR, and Microarray analysis examined the underlying molecular mechanisms. KDM6B promotes the expression of Aggrecan, COL2A1, COL5, glycosaminoglycans, and collagen fibers, while also increasing the COL2/COL1 ratio in SCAPs. In vivo, SCAPs overexpressing KDM6B significantly enhanced the repair and regeneration of knee cartilage and subchondral bone, with higher levels of glycosaminoglycan and COL5 expression observed within the tissue. KDM6B promotes the chondrogenic differentiation potential of SCAPs by repressing HES1. In addition, knock-down of HES1 enhanced the chondrogenic differentiation of SCAPs. KDM6B enhances the differentiation of SCAPs into chondrocytes and demonstrated its effectiveness in the repair and regeneration of cartilage tissue and subchondral bone in vivo experiments. These findings provide an important foundation for future research on the use of dental tissue-derived stem cells to treat cartilage injuries.

Histopathologic Marks of Tongue in a Mouse Model of Oculopharyngeal Muscular Dystrophy Suggest Biomechanical Defects.

The tongue facilitates vital activities such as swallowing. Difficulty swallowing (dysphagia) is common in the elderly population and in patients with adult-onset neuromuscular disease. In oculopharyngeal muscular dystrophy (OPMD), dysphagia is often the first symptom. OPMD is an autosomal-dominant myopathy caused by a trinucleotide-expansion mutation in the gene encoding nuclear poly(A)-binding protein (PABPN)-1. Expanded-mutant PABPN1 forms insoluble nuclear aggregates that reduce the levels of the soluble form. Clinical tongue involvement in OPMD has been documented but is poorly understood. Histopathologic analysis of the tongue in an OPMD mouse model was done by light and electron microscopy combined with RNA sequencing. PABPN1 nuclear aggregates were found at moderate levels, whereas deposition of insoluble PABPN1 in blood vessels was prominent already at age 4 months. Muscle wasting of the tongue was age associated. RNA signatures of the OPMD tongue were enriched for mitochondrial and cytoskeletal genes. Electron microscopy revealed abnormalities in sarcomere and mitochondria organization in A17/+ mice, suggesting an energy and contractile deficit in OPMD tongue. This detailed analysis of the histopathology of the tongue in the A17/+ mouse model opens new avenues for understanding the mechanisms of dysphagia.

Thermosensitive-based synergistic antibacterial effects of novel LL37@ZPF-2 loaded poloxamer hydrogel for infected skin wound healing.

Trauma healing is the process of healing after the body has been subjected to an external force and the skin and other tissues have become dissected or defective, showing the synergistic effect of various processes. Therefore, the investigation of innovative wound dressings has significant research and clinical implications. In this study, we constructed a zinc based metal-organic framework (MOF) and loaded with antimicrobial peptide LL37 to prepare LL37@ZPF-2 (ZPF = zeolite pyrimidine backbone), which was subsequently integrated with Poloxamer 407 to fabricate LL37@ZPF-2 thermosensitive hydrogel. Our study showed that in-situ packaging method can achieve encapsulation rate of 98 % and 15 % of drug loading for LL37. LL37@ZPF-2 demonstrated a higher inhibitory potency against S.aureus compared to E.coli. The Poloxamer 407-gel exhibits thermo-responsive sol-to-gel phase transition behaviors with a phase transition temperature (Tsol/gel) of ∼ 28.01℃, making it an appropriate material for wound healing. The composite hydrogel has excellent biocompatibility and hemocompatibility. A full-thickness skin defect model was built to confirm that LL37@ZPF-2 thermosensitive hydrogel dressing could inhibit bacterial growth, reduce the risk of wound infection, and stimulate angiogenesis and collagen deposition, resulting in a wound healing rate of 94.4 % on day 7 and complete healing on day 10. Our findings demonstrate that the novel thermosensitive LL37@ZPF-2 hydrogel confers good antibacterial activity, promoting cell migration and infected-wound healing properties, providing a promising platform for wound healing.

Feasibility, trueness and precision of intraoral scanners in digitizing maxillectomy defects with exposed zygomatic implants in situ: An in vitro 3D comparative study.

To in-vitro evaluate the feasibility and accuracy (trueness and precision) of various intraoral scanners (IOS) to digitize maxillectomy defect models with exposed zygomatic implants in situ. Six partially edentulous and edentulous maxillectomy defect models with 2 zygomatic implants each were obtained. References scans were obatined by using a laboratory scanner (inEos X5; Dentsply Sirona). Three IOS, Trios 3, Trios 4 (3Shape A/S), and Primescan (Dentsply Sirona) were used first to digitize the entire model including implants and then to only scan the exposed part of zygomatic implants. The feasibility was assessed by evaluating the intraoral scanner's ability to accurately capture the maxillectomy defects and zygomatic implants, compared to a reference standard. Trueness and precision were evaluated using software's global best-fit alignment (GOM Inspect, GOM GmbH). Multifactorial analysis of variance (ANOVA) was used to compare the mean 3D deviation according to different scanners, groups, and model types. The significance level used in the analyses was 5 % (α=0.05). All scanners showed adequate feasibility to scan the entire maxillectomy defects and exposed implants regardless of the structural complexity. The results of trueness showed that Primescan has the smallest 3D deviations (0.0252 mm) followed by Trios 4 (0,0275 mm), and then Trios 3 (0.0318 mm) (p < 0.001). The results of precision showed that Primescan had the smallest 3D deviations (0.0026 mm) followed by Trios 3 (0,0080 mm), and then Trios 4 (0,0097 mm) (p < 0.001). Intraoral scanners differ in feasibility, trueness and accuracy of all scans, with Primescan providing the best combination of feasibility, trueness and accuracy, followed by Trios 4 and Trios 3. Scanning maxillectomy defects with various exposed zygomatic implants can be feasible and accurate using intraoral scanners (Trios 3, Trios 4, and Primescan). The use of intraoral scanners for implant-prosthetic rehabilitation of maxillectomy defect can be a feasible alternative that can improve and simplify the workflow.

Oyster Shell Powder/PCL Composite Scaffolds Loaded with Psoralen Nanospheres Promote Large Bone Defect Repair.

Research on bone substitutes for repairing bone defects has drawn increasing attention, and the efficacy of three-dimensional (3D) printed bioactive porous scaffolds for bone defect repair has been well documented. Our previous studies have shown that psoralen can promote osteogenesis by activating the Wnt/β-catenin and BMP/Smad signaling pathways and their crosstalk effects, and psoralen nanospheres have a good osteogenesis-promoting effect in vitro with low cytotoxicity. The Chinese medicine oyster shell powder, characterized by its porous structure, strong adsorption, and unique bioactivity, has potential in fracture-promoting repair materials. However, the effect of loading psoralen nanospheres onto oyster shell powder/polycaprolactone (OSP/PCL) scaffolds to repair bone defects is unclear. In this study, composite scaffolds consisting of OSP PCL were prepared by 3D printing, and psoralen nanospheres were adhered to the scaffolds. The characterization features of the composite scaffold system were investigated in vitro concerning the biocompatibility of bone mesenchymal stem cells (BMSCs). The efficacy of the composite scaffolds for repairing bone defects was explored in vivo through a rat cranial bone defect model. The results showed that the composite scaffolds were homogeneous porous structures with high mechanical strength and could be adhered well by the psoralen-loaded nanospheres. In vitro studies showed that the scaffolds had good biocompatibility with BMSCs and positively affected the expression of osteogenic differentiation-related proteins. In vivo studies showed that the composite scaffolds could more effectively promote the formation of new bone in the defect area (Φ5 mm) compared to the pure PCL scaffolds. At the same time, the composite scaffolds containing psoralen had a more significant stimulating effect on the healing of the cranial defects compared with the OSP/PCL scaffolds without psoralen.

A light-cured injectable composite hydrogel based on chitosan and decellularized matrix modulates stem cell aggregation behavior for accelerating cartilage defect repair.

Cartilage repair remains a formidable challenge because of its limited regenerative capacity. Construction of a biomimetic hydrogel matrix that can induce cell aggregation is a promising therapeutic option. Cell aggregates are more beneficial than dissociated cells for improving survival and chondrogenic differentiation, thereby facilitating cartilage repair. Herein, we report a light-cured injectable composite hydrogel with cellular aggregation properties for cartilage defect repair that combines methacrylated chitosan (CSMA) and a methacrylate-modified decellularized extracellular matrix (dECMMA). The CSMA promotes cell aggregate formation by enhancing cadherin expression. The dECMMA retains many inherent components and bioactive factors, thereby providing a more natural microenvironment for cell proliferation and differentiation. By precisely adjusting the compositions of the CSMA and dECMMA, it was possible to fine-tune their physicochemical properties and biochemical cues. The results showed that a composite hydrogel composed of 2% (m/v) CSMA and 5% (m/v) dECMMA exhibited good injectability, appropriate degradability and mechanical properties, and regulated the formation of bone marrow mesenchymal stem cell aggregates. Transplantation of the composite hydrogel loaded with bone marrow mesenchymal stem cells (BMSCs) into a cartilage defect model demonstrated effective hyaline cartilage repair. Thus, light-cured injectable composite hydrogels embedded with BMSCs holds clinical promise for cartilage defect repair.

Endocytosis-mediated healing: recombinant human collagen type III chain-induced wound healing for scar-free recovery

Abstract Scar formation can be effectively prevented when the proportion of collagen type I (Col I)/type III (Col II) is reduced. Unlike Col III, recombinant human collagen type III chain (RHC III chain) does not possess a triple helical structure. This study aimed to elucidate the capacity of fibroblasts to uptake RHC III chain, reduce the Col I/Col III ratio, and determine its effects on wound healing and scar. RHC III chain demonstrates qualified cell compatibility. In cell experiments, immunofluorescence and Western Blot (WB) analyses revealed an increase in the polyhistidine tag level, indicating that RHC III chain in internalized by these cells. Transmission electron microscopy (TEM) showed increased intracellular phagocytic activity, indicating that RHC III chain enters fibroblasts by endocytosis. The immunofluorescence and WB showed that Col III synthesis enhanced, and Col I/Col III ratio reduced. However, the polyhistidine tag disappeared with time, indicating that RHC III chain degraded within cells and then synthesized into Col III. The content of newly synthesized Col III increases, but Real-time fluorescence quantitative showed a decrease in Col III related gene content suggests the formation of negative feedback. However, due to the sufficient raw materials, the amount of Col III synthesis is still increasing, leading to the reduction of the ratio of type I collagen/type III collagen, which beneficial to wound healing and reduce scar hyperplasia. In animal experiments, the SD rat full-thickness skin defect model of Wound suggests that RHC III chain also takes effect through endocytosis and ultimately promotes wound healing. The rabbit ear scar model suggests that RHC III chain inhibits scar proliferation by reducing the ratio of Col I/Col III. In summary, RHC III chain was endocytosed by fibroblasts to promote native Col III synthesis, as well as promote wound healing and reduce scar hyperplasia.

Polydeoxynucleotide-Loaded Visible Light Photo-Crosslinked Gelatin Methacrylate Hydrogel: Approach to Accelerating Cartilage Regeneration.

Articular cartilage faces challenges in self-repair due to the lack of blood vessels and limited chondrocyte concentration. Polydeoxyribonucleotide (PDRN) shows promise for promoting chondrocyte growth and cartilage regeneration, but its delivery has been limited to injections. Continuous PDRN delivery is crucial for effective cartilage regeneration. This study explores using gelatin methacrylate (gelMA) hydrogel, crosslinked with visible light and riboflavin 5'-phosphate sodium (RF) as a photoinitiator, for sustained PDRN release. GelMA hydrogel's synthesis was confirmed through spectrophotometric techniques, demonstrating successful methacrylate group incorporation. PDRN-loaded gelMA hydrogels displayed varying pore sizes, swelling ratios, degradation rates, and mechanical properties based on gelMA concentration. They showed sustained PDRN release and biocompatibility, with the 14% gelMA-PDRN composition performing best. Glycosaminoglycan (GAG) activity was higher in PDRN-loaded hydrogels, indicating a positive effect on cartilage formation. RT-PCR analysis revealed increased expression of cartilage-specific genes (COL2, SOX9, AGG) in gelMA-PDRN. Histological assessments in a rabbit cartilage defect model demonstrated superior regenerative effects of gelMA-PDRN hydrogels. This study highlights the potential of gelMA-PDRN hydrogels in cartilage tissue engineering, providing a promising approach for effective cartilage regeneration.

Analysis of the Effect of Human Type I Collagen-Derived Peptide on Bone Regenerative Capacity and Comparison with Various Collagen Materials In Vivo.

Background and Objectives: Autologous bone grafting is the first choice for reconstructive surgery in bone defects due to trauma or malignant tumors. However, there is an increasing demand for minimally invasive alternatives involving bone regeneration using artificial materials. Biomimetic materials that replicate the body's microscopic structure, such as Cellnest®, are gaining attention. Cellnest is a xeno-free recombinant peptide based on human type I collagen, containing a rich Arg-Gly-Asp (RGD) motif related to cell adhesion. The aim of this study was to compare the effects of Cellnest with existing collagen materials (Pelnac®, Integra®, Terudermis®) on bone regeneration and elucidate the underlying mechanisms. Materials and Methods: In vivo experiments involved a rat model of calvarial bone defects, in which Cellnest and other collagen materials were implanted into the defect area. Bone formation was assessed after 4 weeks using micro-computed tomography (micro-CT) and histological analysis. In vitro experiments included the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), adhesion, and migration assays, and a real-time polymerase chain reaction using rapidly expanding cells (RECs) to explore the mechanisms of Cellnest's bone regenerative capacity. Results: The micro-CT analysis showed that the regenerated bone area was significantly greater in the Cellnest group (72.3%) than in the Pelnac® (25.5%), Integra® (31.6%), and Terudermis® (38.3%) groups. The histological analysis confirmed similar trends, with Cellnest showing 42.2% bone regeneration, outperforming the other materials. The in vitro assays revealed that Cellnest promoted cell proliferation, adhesion, and migration. Gene expression analysis demonstrated that Cellnest significantly increased the levels of the bone formation markers ALP and COL1. Conclusions: Cellnest, a human type I collagen-like peptide rich in RGD motifs, enhances bone regeneration by promoting MSC adhesion and migration, and bone formation-related gene expression. The findings suggest its potential as an effective material for bone defect reconstruction.

Biodegradable PHBVHHx-PEG/Collagen Hydrogel Scaffolds for Cartilage Repair.

Recently, there has been increased attention on the treatment of cartilage repair. Overall, we constructed PHBVHHx-COL, a composite hydrogel of PHBVHHx-co-PEG and collagen, and evaluated its cartilage repair efficacy through in vitro and invivo studies using hydrogel loaded with peripheral blood-derived mesenchymal stem cells (PBMSCs). Rheological properties and compressive mechanical properties of the hydrogels were systematically evaluated. The cytocompatibility of the hydrogels was evaluated using the Cell Counting Kit-8 test, live/dead staining, scratch test, and transwell test. The effect of chondrogenic differentiation of PBMSCs on hydrogels was evaluated using immunofluorescence staining and reverse transcription-polymerase chain reaction. Furthermore, the invivo cartilage repair ability of the hydrogels was confirmed following in situ injections in rabbit chondral defect models. Finally, the induced polarization of the hydrogel scaffold on macrophages was explored by the expression of CD86 and CD206. In vitro experimental results confirmed that PHBVHHx-COL-gel led to better cell migration, proliferation, and chondrogenic differentiation than PHBVHHx-PEG and COL hydrogels. Hematoxylin and eosin staining indicated that the tissue of the repaired area in the PHBVHHx-COL group was nearly in fusion with the surrounding normal tissue and the reconstruction of subchondral bone was good. Safranin-O staining and COL-2 immunohistochemistry indicated that the tissue of the repaired area in the PHBVHHx-COL group had more cartilage-specific matrix secretion. The PHBVHHx-COL group exhibited more M2 macrophage infiltration and less M1 macrophage presentation than the other groups. This study demonstrated that PHBVHHx-COL scaffolds loaded with PBMSCs significantly promoted the repair of cartilage injury through immune regulation by M2 polarization and could be potential candidates for cartilage tissue engineering.

Injectable enzyme-crosslinking antioxidant hydrogel for stem cells protection and application in skeletal muscle regeneration

Repair of large and irregular skeletal muscle defects by cell therapy has been one of the major challenges in tissue engineering and regenerative medicine because of some major hurdles including stem cell death, function decline rapidly, and low retention in situ. Commercially available hydrogels for encapsulating stem cells are usually not suitable for uses in deep and irregular defects due to the limitations of crosslinking approaches as well as that of antioxidant properties. In this work, an injectable and self-healing hydrogel was developed, which is composed of caffeic acid grafted-gelatin molecules cross-linked through laccase catalysis reaction. Mechanical properties, swelling and degradation rates, cell compatibility, ROS-scavenging ability, and anti-senescence potentials of the hydrogels were characterized and investigated with varying caffeic acid contents. Result showed that the hydrogels hold features of strong capacity of scavenging reactive oxygen species, appropriated mechanical modulus falling in the range of that for bone marrow, and relative low oxygen microenvironment, which enabled the hydrogels to reduce the senescence of bone marrow-derived mesenchymal stem cells (BMSCs) and preserved their stemness. When applied to a mouse model of large and deep skeletal muscle defects, the hydrogel encapsulation increased BMSC retention in situ, improved the cell viability, and differentiation function, promoting myofiber regeneration, vascularization, and M2 macrophage polarization. In conclusion, this study highlights the superior ability of the hydrogel to preserve BMSCs’ stemness and enhance their therapeutic potential, offering a promising strategy for BMSCs protection and application to the repair of deep and large skeletal muscle defects in situ.

Functionalized Periosteum-Derived Microsphere-Hydrogel with Sequential Release of E7 Short Peptide/miR217 for Large Bone Defect Repairing.

Large bone defects are still a persistent challenge in orthopedics. The availability limitations and associated complications of autologous and allogeneic bone have prompted an increasing reliance on tissue engineering and regenerative medicine. In this study, we developed an injectable scaffold combining an acellular extracellular periosteal matrix hydrogel with poly(d,l-lactate-co-glycol-acetate) microspheres loaded with the E7 peptide and miR217 (miR217/E7@MP-GEL). Characterization of the composites included morphological analysis by scanning electron microscopy, degradation and swelling tests, invitro and invivo biological evaluation, and the biological activity evaluation of mesenchymal stem cells (MSCs) through their effects on cell recruitment, proliferation, and osteogenic differentiation. The designed hydrogels demonstrated good physical and chemical properties that are cytocompatible and suitable for cell recruitment. Invitro studies confirmed the high biological activity of the release agent, which markedly enhanced the proliferation and osteogenic differentiation of MSCs. Invivo application to a rat model of a femur defect exhibited a significant increase in bone volume and density over 7 weeks, resulting in enhanced bone regeneration. Acellular periosteum-based hydrogels combined with the E7 peptide and miR217-loaded poly(d,l-lactate-co-glycol-acetate) microspheres can promote effective bone regeneration through the recruitment, proliferation, and osteogenic differentiation of MSCs, which provides a promising approach for the treatment of large bone defects.