Graft Scaffold Research Articles

26. A New Regenerative Paradigm for Interval Autologous Cranioplasty: The Cell-Augmented Scaffold-Enhanced (CASE) Cranioplasty

Purpose: Autologous interval cranioplasty has become the standard of care following decompressive craniectomy. Replantation of the stored bone graft has infection and bone resorption rates upwards of 30%. We propose a new paradigm for autologous cranioplasty incorporating novel regenerative techniques that aims to improve fidelity of grafts and reduce infection and resorption. Methods: An IRB-approved cohort of 11 consecutive patients who underwent Cell-Augmented Scaffold-Enhanced (CASE) regenerative cranioplasty were compared to 14 who underwent traditional autologous cranioplasty. All were followed for at least 6 months postoperatively. For the CASE cranioplasty, frozen autologous bone graft was thawed and washed in accordance with institutional protocol. Tenets of standard interval cranioplasty were followed. Cell-augmentation of the autologous bone graft scaffold was performed; channels were created in the diploic space, then packed with a 1:1 mixture of fresh autologous bone graft harvested from surrounding cranium and bone allograft. Traditional technique followed tenets of cranioplasty but without channeling nor cell augmentation. Primary outcome measures included post-operative graft infection, bone resorption after >6 months and need for graft explantation. Patient demographics and operative data were also collected. Quantitative statistics performed include Student’s independent t-test and Χ2 analysis with a significance level set to p = 0.05. Descriptive statistics include relative risks (RR) with 95% confidence interval (95%CI), means and standard deviations (SD). Results: Clinical evaluation for ≥ 6 months postoperatively demonstrated a bone graft infection rate of 0% for CASE subjects versus 14.3% (n=2) for traditional patients; RR for post-operative infection was 1.17 [95%CI 0.94-1.45]. No patients had bone resorption requiring reoperation or explantation from the CASE cohort, while 2 subjects (14.3%) from the traditional cohort required explantation (RR 1.17, 95%CI 0.94-1.45) due to graft infection. There was no statistically significant difference in gender, etiology, interval time from craniectomy to cranioplasty, nor dimension of defect between the groups. CASE subjects were found to be incidentally older (58 years vs 42, p = 0.02). Mean duration of surgery was 221.3min (SD±52.6min) for CASE subjects vs 119.9 (SD±53.6min) for traditional (p<0.01). Conclusion: Cell-Augmented Scaffold-Enhanced cranioplasty represents a safe novel paradigm modification to standard autologous interval cranioplasty technique with reduced rates of post-operative infection and reoperation for explantation.

Biomechanical Effects of 3D-Printed Bioceramic Scaffolds With Porous Gradient Structures on the Regeneration of Alveolar Bone Defect: A Comprehensive Study.

In the repair of alveolar bone defect, the microstructure of bone graft scaffolds is pivotal for their biological and biomechanical properties. However, it is currently controversial whether gradient structures perform better in biology and biomechanics than homogeneous structures when considering microstructural design. In this research, bioactive ceramic scaffolds with different porous gradient structures were designed and fabricated by 3D printing technology. Compression test, finite element analysis (FEA) revealed statistically significant differences in the biomechanical properties of three types of scaffolds. The mechanical properties of scaffolds approached the natural cancellous bone, and scaffolds with pore size decreased from the center to the perimeter (GII) had superior mechanical properties among the three groups. While in the simulation of Computational Fluid Dynamics (CFD), scaffolds with pore size increased from the center to the perimeter (GI) possessed the best permeability and largest flow velocity. Scaffolds were cultured in vitro with rBMSC or implanted in vivo for 4 or 8 weeks. Porous ceramics showed excellent biocompatibility. Results of in vivo were analysed by using micro-CT, concentric rings and VG staining. The GI was superior to the other groups with respect to osteogenicity. The Un (uniformed pore size) was slightly inferior to the GII. The concentric rings analysis demonstrated that the new bone in the GI was distributed in the periphery of defect area, whereas the GII was distributed in the center region. This study offers basic strategies and concepts for future design and development of scaffolds for the clinical restoration of alveolar bone defect.

Large Glenoid Defects Treated by Multiple Bioresorbable Pinning-Assisted Bone-Grafting in Reverse Shoulder Arthroplasty.

This procedure is performed with the patient under general anesthesia and in the beach-chair position, via a deltopectoral approach. After placing the structural graft, 5 to 10 provisional 1.5-mm Kirschner wires are inserted through the graft up the medal cortical bone of the scapula. The Kirschner wires are subsequently replaced with bioresorbable (BR) pins (1.5-mm Fixsorb Pin; TEIJIN). If more wires are needed, another set of 4 to 5 RB pins is inserted to gain initial stability. After placing the graft, the glenoid component is implanted as usual. Traditionally, 1 or 2 screws are inserted in the periphery of the graft to obtain stability. The screws either must be inserted at an angle that does not impede placement of the implant2 or are removed before the placement of the glenoid implant. One or a maximum of 2 long screws are inserted through the graft and glenoid3, meaning that the screw(s) must be aimed at a very narrow space between the central post and screws. Otherwise, these screws will represent an obstacle to the placement of the glenoid implant. In addition to facilitating initial graft stability, this procedure promotes graft incorporation. Typically, when performing this procedure, a total of 15 to 20 temporary Kirschner wires are placed in sets, with 5 to 7 wires per set. Of these, the most stable wires, usually 8 to 10 in total, are replaced by BR pins. The resultant bone holes, whether filled or unfilled with the BR pins, may promote neovascularization and osteoinduction, enabling long-lasting remodeling of and improved incorporation of the bone graft. A prior study compared the use of MBP versus angulated bony-increased offset (BIO) graft, assessing graft incorporation according to the size of the remaining graft on axial radiographs, with full incorporation defined as >75% of the original graft size1,2. In that study, all 13 patients in the MBP group showed full graft incorporation compared with only 9 (47%) of 19 patients in the angulated BIO group (p < 0.001)1. Expose all 4 quadrants of the glenoid in cases of type-2 deformity. Accurate orientation of the MBP is important.Expose the upper and lower 2 quadrants of the glenoid in cases of type-3 deformity. The bases of the scapular spine and axillary border serve as a graft scaffold.Preserve circumferential soft tissues in cases of type-3 deformity because these tissues will serve to contain cancellous bone graft.Keep the Kirschner wire that extends the most medially (reaching the most medial cortical bone of the scapula) as a future guidewire for drilling of the central peg hole. RSA = reverse shoulder arthroplastyMBP = multiple bioresorbable pinningBIO = bony-increased offsetBR = bioresorbableTSA = total shoulder arthroplastyCT = computed tomographyK-wire = Kirschner wireROM = range of motionP.O. = postoperative.

Near-field electrospinning of polydioxanone small diameter vascular graft scaffolds

The ideal “off the shelf” tissue engineering, small-diameter (SD) vascular graft hinges on designing a scaffold to act as a template that facilitates transmural ingrowth of capillaries to regenerate an endothelized neointimal surface. Towards this goal, we explored two types of near-field electrospun (NFES) polydioxanone (PDO) architectures, as SD vascular graft scaffolds. The first architecture type consisted of a 200 × 200 μm and 500 × 500 μm grid geometry with random fiber infill, while the second architecture consisted of aligned fibers written in a 45°/45° and 20°/70° offset from the long axis written, both on a 4 mm diameter cylindrical mandrel. These vascular graft scaffolds were evaluated for their effective pore size, mechanical properties, and platelet-material interactions compared to traditionally electrospun (TES) scaffolds and Gore-Tex® vascular grafts. It was found that effective pore size, given by 9.9 and 97 μm microsphere filtration through the scaffold wall for NFES scaffolds, was significantly more permeable compared to TES scaffolds and Gore-Tex® vascular grafts. Furthermore, ultimate tensile strength, percent elongation, suture retention, burst pressure, and Young's modulus were all tailorable compared to TES scaffold characterization. Lastly, platelet adhesion was attenuated on NFES scaffolds compared to TES scaffold which approximates the low level of platelet adhesion measured on Gore-Tex®, with all samples showing minimal platelet activation given by P-selectin surface expression. Together, these results suggest a highly tailorable process for the creation of the next generation of small-diameter vascular grafts.

The Effect of Low-Temperature Thermal Processing on Bovine Hydroxyapatite Bone Substitutes, toward Bone Cell Interaction and Differentiation.

Ideal bone grafting scaffolds are osteoinductive, osteoconductive, and encourage osteogenesis through the remodeling processes of bone resorption, new bone formation, and successful integration or replacement; however, achieving this trifecta remains challenging. Production methods of bone grafts, such as thermal processing, can have significant effects on the degree of cell-surface interactions via wide-scale changes in the material properties. Here, we investigated the effects of small incremental changes at low thermal processing temperatures on the degree of osteoclast and osteoblast attachment, proliferation, and differentiation. Bovine bone scaffolds were prepared at 100, 130, 160, 190, and 220 °C and compared with a commercial control, Bio-Oss®. Osteoclast attachment and activity were significantly higher on lower temperature processed bone and were not present ≥190 °C. The highest osteoblast proliferation and differentiation were obtained from treatments at 130 and 160 °C. Similarly, qRT2-PCR assays highlighted osteoblasts attached to bone processed at 130 and 160 °C as demonstrating the highest osteogenic gene expression. This study demonstrated the significant effects of small-scale processing changes on bone graft materials in vitro, which may translate to a tailored approach of cellular response in vivo.

Extracellular matrix-derived and low-cost proteins to improve polyurethane-based scaffolds for vascular grafts

Vascular graft surgeries are often conducted in trauma cases, which has increased the demand for scaffolds with good biocompatibility profiles. Biodegradable scaffolds resembling the extracellular matrix (ECM) of blood vessels are promising vascular graft materials. In the present study, polyurethane (PU) was blended with ECM proteins collagen and elastin (Col-El) and gelatin (Gel) to produce fibrous scaffolds by using the rotary jet spinning (RJS) technique, and their effects on in vitro properties were evaluated. Morphological and structural characterization of the scaffolds was performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Micrometric fibers with nanometric rugosity were obtained. Col-El and Gel reduced the mechanical strength and increased the hydrophilicity and degradation rates of PU. No platelet adhesion or activation was observed. The addition of proteins to the PU blend increased the viability, adhesion, and proliferation of human umbilical vein endothelial cells (HUVECs). Therefore, PU-Col-El and PU-Gel scaffolds are promising biomaterials for vascular graft applications.

Effects of Vitamin A (Retinol) Release from Calcium Phosphate Matrices and Porous 3D Printed Scaffolds on Bone Cell Proliferation and Maturation

Vitamin A is a fat-soluble compound widely known for vision health. Highly variable reports on its effects on bone health have necessitated further research to truly understand its role on bone cell proliferation. Retinol, one bioactive form of vitamin A, is incorporated into synthetic bone graft scaffolds for low load-bearing clinical bone treatment. The objective of this work is to understand the effects of retinol on osteoblast and osteoclast cells when embedded within calcium phosphate matrices, including interconnected porous 3D printed tricalcium phosphate scaffolds. Results show that hydrophobic retinol can be released from bone scaffolds when a combination of biodegradable polymers, polycaprolactone and polyethylene glycol, are employed as drug carriers. The release of retinol in vitro can support a 20 ± 1% increase in osteoblast (bone-forming) cell proliferation with proper cell adhesion and filopodial extensions. Osteoclast cell morphology is necrosed and torn with a reduction in proliferation at approximately 6 ± 1% when retinol is present. In addition, inhibition of osteoclastic resorption pit bays is noted using scanning electron microscopy. With the scaffolds' round pore interconnectivity facilitating retinol release, this system can provide an alternative to traditional bone grafts while additionally supporting bone healing through enhanced osteoblast cell proliferation and inhibition of osteoclast resorption activity.

Clinical and quality-of-life outcomes of a combined synthetic scaffold and autogenous tissue graft procedure for articular cartilage repair in the knee

BackgroundInjuries to the articular cartilage of the knee often fail to heal properly due to the hypocellular and avascular nature of this tissue. Subsequent disability can limit participation in sports and decrease quality of life. Subchondral bone perforations are used for the treatment of small defects. Filling out the central portion in larger lesions becomes difficult, and scaffolds can be used as adjuvants, providing a matrix onto which the defect can be filled in completely. Also, autogenous cartilage grafts can be combined, acting as an inducer and improving healing quality, all in a single procedure.MethodsThis observational study evaluated the clinical and quality-of-life outcomes of patients with articular cartilage lesions of the knee undergoing repair via a microfracture technique combined with a synthetic scaffold and autogenous cartilage graft, with transosseous sutures and fibrin glue fixation, at 12 months of follow-up. Secondarily, it assessed whether combined procedures, previous surgical intervention, traumatic aetiology, lesion location, and age affect outcomes. The sample consisted of adult patients (age 18–66 years) with symptoms consistent with chondral or osteochondral lesions, isolated or multiple, ICRS grade III/IV, 2–12 cm2 in size. Patients with corrected angular deviations or instabilities were included. Those with BMI > 40 kg/m2, prior total or subtotal (> 30%) meniscectomy, second-look procedures, and follow-up < 6 months were excluded. Pain (VAS), physical activity (IKDC), osteoarthritis (WOMAC), and general quality of life (SF-36) were assessed.Results64 procedures were included, comprising 60 patients. There was significant improvement (P < 0.05) in VAS score (5.92–2.37), IKDC score (33.44–56.33), and modified WOMAC score (53.26–75.93) after surgery. The SF-36 showed significant improvements in the physical and mental domains (30.49–40.23 and 46.43–49.84 respectively; both P < 0.05).ConclusionsCombination of microfractures, autogenous crushed cartilage graft, synthetic scaffold, and transosseous sutures with fibrin glue provides secure fixation for treatment of articular cartilage lesions of the knee. At 12-month follow-up, function had improved by 20 points on the IKDC and WOMAC, and quality of life, by 10 points on the SF-36. Age > 45 years had a negative impact on outcomes.

Uni-Directionally Oriented Fibro-Porous PLLA/Fibrin Bio-Hybrid Scaffold: Mechano-Morphological and Cell Studies.

In this study, we report a biohybrid oriented fibrous scaffold based on nanofibers of poly(l-lactic acid) (PLLA)/fibrin produced by electrospinning and subsequent post-treatment. Induced hydrolytic degradation of the fibers in 0.25 M NaOH solution for various time periods followed by the immobilization of fibrin on the hydrolyzed fiber surfaces was shown to significantly affect the mechanical properties, with the tensile strength (40.6 MPa ± 1.3) and strain at failure (38% ± 4.5) attaining a value within the range of human ligaments and ligament-replacement grafts. Unidirectional electrospinning with a mandrel rotational velocity of 26.4 m/s produced highly aligned fibers with an average diameter of 760 ± 96 nm. After a 20-min hydrolysis treatment in NaOH solution, this was further reduced to an average of 457 ± 89 nm, which is within the range of collagen bundles found in ligament tissue. Based on the results presented herein, the authors hypothesize that a combination of fiber orientation/alignment and immobilization of fibrin can result in the mechanical and morphological modification of PLLA tissue scaffolds for ligament-replacement grafts. Further, it was found that treatment with NaOH enhanced the osteogenic differentiation of hMSCs and the additional inclusion of fibrin further enhanced osteogenic differentiation, as demonstrated by decreased proliferative rates and increased ALP activity.

Tissue engineering and cell technologies: how these can help in correction of urinary system pathologies. Literature review and own experience

SummaryIntroduction. Modern possibilities of cellular and tissue engineering technologies are presented in this pub-lication, that are developed to be applied to urologic patholo gies in experimental and clinical practice. Оwn experience is described in rabbit bladder reconstruction with tissue engineering construction. Тissue engineering is one of the leading trends in modern science and envis-ages the development of restoration or replacement tech-niques for damaged structures with the use of scaffolds and cells. However, in spite of a huge number of publica-tions, urologic structures reconstructions are in minority. Nowadays, to treat damaged human tissues and organs, bioresorbable synthetic polimers are becoming more and more popular, those are used as the basis for cell culture (Ho M.H. et al., 2006; Shao J. et al., 2012). Foreign scien-tists have been successfully attempting to create tissue wall analogues for a long time. Маterials and methods.15 male Chinchilla rabbits underwent partial bladder resection with scaffold grafting containing smooth mio-cytes with urothelium, fibroblasts and mesenchymal stem cells, as well as acellular matrix. Results. In the group of animals that received scaffoled with labelled mesenchy-mal stem cells, in 5 out of 6 cases, matrix lysis occurred with no signs of graft rejection. After 2.5 months post-op, the capacity of the bladders was comparable with that pre-op. In the implantation site, one could visually see the area of a newly formed bladder wall, with vasculariza-tion signs. Histologically, initial stages of reparation and angiogenesis have been identified. Confocal microscopy of cryoslices from the implantation site showed labelled cells taking part in the urothelium-like structure forma-tion. In all cases when acellular matrix or scaffolds with smooth miocytes with urothelium and fibro blasts were implanted, graft rejection took place, with various de-grees of inflammation and decrease of bladder capacity. Conclusion. The use of tissue engineering construction made of composite matrix and rabbit mesenchymal stem cells was effective for small bladder defects reconstruc-tion. Further development of techniques to create mul-ticomponent graft with allogenic cells may improve the results of treating such pathologies in patients when au-togenic material cannot be harvested. A study is under way in St Petersburg Research Institute of Phthisiopulm-onology as of now, to study tissue engineered bladder augmentation, up to its total replacement (Russian Scien-tific Foundation grant no. 22-25-20167, https://rscf.ru/project/22-25-20167/ and St Petersburg Scientific Foun-dation grant in accordance with agreement dd. 14th April 2022 no. 20/2022)

In vivo performance of electrospun tubular hyaluronic acid/collagen nanofibrous scaffolds for vascular reconstruction in the rabbit model

One of the main challenges of tissue-engineered vascular prostheses is restenosis due to intimal hyperplasia. The aim of this study is to develop a material for scaffolds able to support cell growth while tolerating physiological conditions and maintaining the patency of carotid artery model. Tubular hyaluronic acid (HA)-functionalized collagen nanofibrous composite scaffolds were prepared by sequential electrospinning method. The tubular composite scaffold has well-controlled biophysical and biochemical signals, providing a good matrix for the adhesion and proliferation of vascular endothelial cells (ECs), but resisting to platelets adhesion when exposed to blood. Carotid artery replacement experiment from 6-week rabbits showed that the HA/collagen nanofibrous composite scaffold grafts with endothelialization on the luminal surface could maintain vascular patency. At retrieval, the composite scaffold maintained good structural integrity and had comparable mechanical strength as the native artery. This study indicating that electrospun scaffolds combined with cells may become an alternative to prosthetic grafts for vascular reconstruction.Graphical

The Effect of Anterior Cruciate Ligament Reconstruction with an Electropsun Scaffold on Tibiofemoral Contact Mechanics.

Surgical reconstruction of the torn ACL is performed to restore native contact mechanics. Drawbacks to traditional ACL repair techniques motivate the development of a tissue engineered ACL scaffold. Our group has developed a hierarchical electrospun polycaprolactone (PCL) scaffold that consists of rolled nanofiber bundles attached at each end with solvent-case blocks of PCL. The goal of this study was to compare ovine cadaver tibiofemoral contact mechanics after ACL reconstruction with the electrospun scaffold to a clinically applicable ACL reconstruction with a soft tissue graft and the ACL transected condition (ACLX). In the ACLX group and after ACL reconstruction with either the electrospun scaffold or soft tissue graft, pressure sensors were inserted under the menisci. Loads up to 890 N were applied at various flexion angles. The scaffold performed the best at restoring contact mechanics in the medial hemijoint to that of the native ACL. The scaffold was good at maintaining a medial-lateral balance of pressures as in the native joint whereas the ACLX shifted pressure off the lateral and on to the medial hemijoint. While the ACL scaffold didn't restore mechanics to that of the native condition, it improved contact mechanics compared to the standard graft replacement and ACLX condition.

Osteochondral Injury of the Talus Treated With Cell-Free Hyaluronic Acid-Based Scaffold (Hyalofast®) - A Reliable Solution.

Background: Osteochondral injuries commonly occur in load-bearing joints, mainly caused by traumatic incidents that can lead to detachment of the cartilage fragment either partial or complete.Objective: This study aims to review the long-term outcome of osteochondral injury of the talus treated with a cell-free hyaluronic acid-based scaffold (Hyalofast®, Anika Therapeutics Inc., Bedford, Massachusetts, USA).Method: This study evaluated the data of seven patients who underwent medial malleolus osteotomy, microfracture, and cell-free hyaluronic acid-based scaffold (HYALOFAST®) insertion between 2015 to 2018. All patients had an osteochondral lesion (OCL) grade III and IV of the talus based on Dipaola classification due to trauma. They were followed up for at least two years and assessed by the short form 36 health survey questionnaire (SF36) for both physical functioning and mental health, American Orthopaedic Foot and Ankle Society (AOFAS) scoring system, and visual analog scale (VAS).Result: All patients were satisfied in terms of physical function, mental health, and pain after one month of surgery (p-value<0.05). There was also an improvement in AOFAS hindfoot and VAS scores from preoperative to postoperative. No complications were noted in the surgical site or bone union.Conclusion: Medial malleolus osteotomy, cell-free hyaluronic acid-based scaffold (HYALOFAST®) grafting, and microfracture are considered relatively easy techniques that are a good choice for patients with sizeable cartilage deficiency and provide a good functional outcome.

Early preclinical evaluation of a novel, computer aided designed, 3D printed, bioresorbable posterior cricoid scaffold

ObjectivesThe posterior cricoid split with rib graft is a procedure that elegantly corrects pediatric posterior glottic stenosis and subglottic stenosis. Currently, the procedure requires harvesting of rib cartilage which leaves room for optimization. With use of three dimensional printing technology, our objective was to design a device that would negate the need for costal cartilage harvesting in this procedure. MethodsAn optimized, novel polycaprolactone scaffold was designed using computer aided design software and three dimensional printing. A pilot proof of concept study was conducted with implantation of the device in three porcine animal subjects. Device was evaluated by post-procedural clinical course, endoscopic exams, post-mortem exam, and histological evaluation. ResultsA series of variably sized scaffolds were created. The scaffolds showed structural integrity and successfully expanded the cricoid cartilage in the porcine model study. Post-operative endoscopy and clinical exams demonstrated no signs of implant instability or failure. Gross and histologic exams showed successful mucosalization over the scaffold and cartilage ingrowth by six weeks. ConclusionThis porcine animal pilot study demonstrated early success of a computer-aided designed, 3D printed, bioresorbable PCL posterior graft scaffold. The scaffolds eliminate the need for costal cartilage harvesting and had excellent surgical usability. The scaffolds functioned as designed, offering proof of concept and grounds for further evaluation to expand on this small pilot study with larger animal studies and continued design refinement.

Nitric oxide-releasing poly(ε-caprolactone)/S-nitrosylated keratin biocomposite scaffolds for potential small-diameter vascular grafts

Rapid endothelialization and regulation of smooth muscle cell proliferation are crucial for small-diameter vascular grafts to address poor compliance, thromboembolism, and intimal hyperplasia, and achieve revascularization. As a gaseous signaling molecule, nitric oxide (NO) regulates cardiovascular homeostasis, inhibits blood clotting and intimal hyperplasia, and promotes the growth of endothelial cells. Due to the instability and burst release of small molecular NO donors, a novel biomacromolecular donor has generated increasing interest. In the study, a low toxic NO donor of S-nitrosated keratin (KSNO) was first synthesized and then coelectrospun with poly(ε-caprolactone) to afford NO-releasing small-diameter vascular graft. PCL/KSNO graft was capable to generate NO under the catalysis of ascorbic acid (Asc), so the graft selectively elevated adhesion and growth of human umbilical vein endothelial cells (HUVECs), while inhibited the proliferation of human aortic smooth muscle cells (HASMCs) in the presence of Asc. In addition, the graft displayed significant antibacterial properties and good blood compatibility. Animal experiments showed that the biocomposite graft could inhibit thrombus formation and preserve normal blood flow via single rabbit carotid artery replacement for 1 month. More importantly, a complete endothelium was observed on the lumen surface. Taken together, PCL/KSNO small-diameter vascular graft has potential applications in vascular tissue engineering with rapid endothelialization and vascular remolding.

Three-Dimensional Printability of an ECM-Based Gelatin Methacryloyl (GelMA) Biomaterial for Potential Neuroregeneration.

The current study introduces two novel, smart polymer three-dimensional (3D)-printable interpenetrating polymer network (IPN) hydrogel biomaterials with favorable chemical, mechanical, and morphological properties for potential applications in traumatic brain injury (TBI) such as potentially assisting in the restoration of neurological function through closure of the wound deficit and neural tissue regeneration. Additionally, removal of injury matter to allow for the appropriate scaffold grafting may assist in providing a TBI treatment. Furthermore, due to the 3D printability of the IPN biomaterials, complex structures can be designed and fabricated to mimic the native shape and structure of the injury sight, which can potentially assist with neural tissue regeneration after TBI. In this study, a peptide-only approach was employed, wherein collagen and elastin in a blend with gelatin methacryloyl were prepared and crosslinked using either Irgacure or Irgacure and Genipin to form either a semi or full IPN hydrogel 3D-printable neuromimicking platform system, respectively. The scaffolds displayed favorable thermal stability and were amorphous in nature with high full width at half-maximum values. Furthermore, no alteration to the peptide secondary structure was noted using Fourier transform infrared spectroscopy. The IPN biomaterials have a stiffness of around 600 Pa and are suitable for softer tissue engineering applications—that is, the brain. Scanning electron micrographs indicated that the IPN biomaterials had a morphological structure with a significant resemblance to the native rat cortex. Both biomaterial scaffolds were shown to support the growth of PC12 cells over a 72 h period. Furthermore, the increased nuclear eccentricity and nuclear area were shown to support the postulation that the IPN biomaterials maintain the cells in a healthy state encouraging cellular mitosis and proliferation. The Genipin component of the full IPN was further shown to exhibit antimicrobial properties and this suggests that Genipin can prevent the growth of pathogens associated with postsurgical brain infections. In addition to these findings, the study presents an anomaly, wherein the full IPN is found to be more brittle than the semi IPN, a finding that is in contradiction with the literature. This research, therefore, contributes to the collection of potential biomaterials for TBI applications coupled with 3D printing and can assist in the progression of neural treatments toward patient-specific scaffolds through the development of custom scaffolds.

Upregulation of Apol8 by Epothilone D facilitates the neuronal relay of transplanted NSCs in spinal cord injury

BackgroundMicrotubule-stabilizing agents have been demonstrated to modulate axonal sprouting during neuronal disease. One such agent, Epothilone D, has been used to treat spinal cord injury (SCI) by promoting axonal sprouting at the lesion site after SCI. However, the role of Epothilone D in the differentiation of neural stem cells (NSCs) in SCI repair is unknown. In the present study, we mainly explored the effects and mechanisms of Epothilone D on the neuronal differentiation of NSCs and revealed a potential new SCI treatment.MethodsIn vitro differentiation assays, western blotting, and quantitative real-time polymerase chain reaction were used to detect the effects of Epothilone D on NSC differentiation. Retrograde tracing using a pseudotyped rabies virus was then used to detect neuronal circuit construction. RNA sequencing (RNA-Seq) was valuable for exploring the target gene involved in the neuronal differentiation stimulated by Epothilone D. In addition, lentivirus-induced overexpression and RNA interference technology were applied to demonstrate the function of the target gene. Last, an Apol8-NSC-linear ordered collagen scaffold (LOCS) graft was prepared to treat a mouse model of SCI, and functional and electrophysiological evaluations were performed.ResultsWe first revealed that Epothilone D promoted the neuronal differentiation of cultured NSCs and facilitated neuronal relay formation in the injured site after SCI. Furthermore, the RNA-Seq results demonstrated that Apol8 was upregulated during Epothilone D-induced neuronal relay formation. Lentivirus-mediated Apol8 overexpression in NSCs (Apol8-NSCs) promoted NSC differentiation toward neurons, and an Apol8 interference assay showed that Apol8 had a role in promoting neuronal differentiation under the induction of Epothilone D. Last, Apol8-NSC transplantation with LOCS promoted the neuronal differentiation of transplanted NSCs in the lesion site as well as synapse formation, thus improving the motor function of mice with complete spinal cord transection.ConclusionsEpothilone D can promote the neuronal differentiation of NSCs by upregulating Apol8, which may provide a promising therapeutic target for SCI repair.

Three-Dimensional Engineered Peripheral Nerve: Toward a New Era of Patient-Specific Nerve Repair Solutions.

Reconstruction of peripheral nerve injuries (PNIs) with substance loss remains challenging because of limited treatment solutions and unsatisfactory patient outcomes. Currently, nerve autografting is the first-line management choice for bridging critical-sized nerve defects. The procedure, however, is often complicated by donor site morbidity and paucity of nerve tissue, raising a quest for better alternatives. The application of other treatment surrogates, such as nerve guides, remains questionable, and it is inefficient in irreducible nerve gaps. More importantly, these strategies lack customization for personalized patient therapy, which is a significant drawback of these nerve repair options. This negatively impacts the fascicle-to-fascicle regeneration process, critical to restoring the physiological axonal pathway of the disrupted nerve. Recently, the use of additive manufacturing (AM) technologies has offered major advancements to the bioengineering solutions for PNI therapy. These techniques aim at reinstating the native nerve fascicle pathway using biomimetic approaches, thereby augmenting end-organ innervation. AM-based approaches, such as three-dimensional (3D) bioprinting, are capable of biofabricating 3D-engineered nerve graft scaffolds in a patient-specific manner with high precision. Moreover, realistic in vitro models of peripheral nerve tissues that represent the physiologically and functionally relevant environment of human organs could also be developed. However, the technology is still nascent and faces major translational hurdles. In this review, we spotlighted the clinical burden of PNIs and most up-to-date treatment to address nerve gaps. Next, a summarized illustration of the nerve ultrastructure that guides research solutions is discussed. This is followed by a contrast of the existing bioengineering strategies used to repair peripheral nerve discontinuities. In addition, we elaborated on the most recent advances in 3D printing and biofabrication applications in peripheral nerve modeling and engineering. Finally, the major challenges that limit the evolution of the field along with their possible solutions are also critically analyzed. Impact statement Complex nerve injuries, including critical-sized gaps (>3 cm loss of substance), gaps involving nerve bifurcations, and those associated with ischemic environments, are difficult to manage. A biomimetic, personalized peripheral nerve tissue surrogate to address these injuries is lacking. The peripheral nerve repair market currently represents a multi-billion-dollar industry that is projected to expand. Given the clinical and economical dilemmas posed by this medical condition, it is crucial to devise novel and effective nerve substitutes. In this review article, we discuss progress in three-dimensional printing technologies, including biofabrication and nerve computer-aided design modeling, toward achieving a patient-specific and biomimetic nerve repair solution.

Investigation of the mechanical properties and biocompatibility of planar and electrospun alkene-styrene copolymers against P(VDF-TrFE) and porcine skin: Potential use as second skin substrates

Elastomers have been used in a variety of biomedical fields, including tissue engineering, soft robotics, prostheses, and cosmetics. Elastomers used for skin grafting scaffolds tend to be biodegradable, but other applications require perdurable elastomers. Advances in perdurable elastomers would allow for the development of a range of substrates useful in the creation of joint prostheses, chronic neural electrodes, implantables, and wearables. Still, for these, tailored mechanical properties and biocompatibility are required. In this work, several perdurable alkene-styrene elastomers and novel polymer blends are investigated for their stress-strain curves; with quantification of Young's moduli, fatigue behavior and standard biocompatibility. In particular, this study attempts to study polymers with mechanical properties similar to the complex characteristics of skin, through comparison with porcine skin samples. Poly (vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), a flexible polymer previously used as a wearable sensor and second skin component, was here used for comparison studies. Interestingly, this study points out that elastomer mechanical properties can be modulated to better replicate the elastic modulus of skin, in particular for KratonTM D1152, a Styrene-Butadiene-Styrene block copolymer. Namely, this is the case when such an elastomer is prepared as an electrospun matrix or as a flat dense film under low temperatures. Moreover, a specific method was optimized to obtain electrospun fibers of this alkene-styrene copolymer.

Influence of surface condition on the degradation behaviour and biocompatibility of additively manufactured WE43

The further development of future Magnesium based biodegradable implants must consider not only the freedom of design, but also comprise implant volume reduction, as both aspects are crucial for the development of higher functionalised implants, such as plate systems or scaffold grafts in bone replacement therapy. As conventional manufacturing methods such as turning and milling are often accompanied by limitations concerning implant design and functionality, the process of laser powder bed fusion (LPBF) specifically for Magnesium alloys was recently introduced. In addition, the control of the degradation rate remains a key aspect regarding biodegradable implants. Recent studies focusing on the degradation behaviour of additively manufactured Magnesium scaffolds disclosed additional intricacies when compared to conventionally manufactured Magnesium parts, as a notably larger surface area was exposed to the immersion medium and scaffold struts degraded non-uniformly. Moreover, chemical etching as post processing technique is applied to remove sintered powder particles from the surface, altering surface chemistry. In this study, cylindrical Magnesium specimens were manufactured by LPBF and surfaces were consecutively modified by phosphoric etching and machining. Degradation behaviour and biocompatibility were then investigated, revealing that etched samples exhibited the overall lowest degradation rates, but experienced large pit formation, while the reduction of surface roughness resulted in a delay of degradation.