Tissue engineering of the annulus fibrosus (AF) is currently being investigated as a treatment for intervertebral disc degeneration, a condition frequently associated with low back pain. The ...objective of this work was to use 3D printing to generate a novel scaffold for AF repair that mimics the structural and biomechanical properties of the native tissue. Multi-layer scaffolds were fabricated by depositing polycaprolactone struts in opposing angular orientations, replicating the angle-ply arrangement of the native AF tissue. Scaffolds were printed with varied strut diameter and spacing. The constructs were characterized morphologically and by static and dynamic mechanical analyses. Scaffold surfaces were etched with unidirectional grooves and the influence on bovine AF cell metabolic activity, alignment, morphology and protein expression was studied
in vitro
. Overall, the axial compressive and circumferential tensile properties of the scaffolds were found to be in a similar range to the native AF tissue. Confocal microscopy images indicated that cells were able to attach and spread on the smooth polycaprolactone scaffolds, but the surface texture induced cellular alignment and proliferation. Furthermore, immunofluorescence analysis demonstrated the aligned deposition of collagen type I, aggrecan and the AF-specific protein marker tenomodulin on the etched scaffolds. Overall, results demonstrated the potential for using the scaffolds as a template for AF regeneration.
The recent convergence of decellularized extracellular matrix (dECM) methodologies and 3D bioprinting (3DBP) has led to multiple advancements in tissue engineering scaffold design by enabling ...researchers to recreate a tissue‐specific 3D environment in a custom geometry. The application of 3DBP of dECM for articular cartilage and intervertebral disc (IVD) repair, however, is still burgeoning. While cartilage and IVD tissue each possess unique architectures, they are composed of similar macromolecules and therefore pose similar challenges for the successful application of their matrix bioinks. Herein, the state‐of‐the‐art in cartilage and IVD dECM bioink preparation, material properties, and applications are highlighted. The current major obstacles regarding optimal decellularization and printing methods are discussed, which need to be overcome to enable recapitulation of the hierarchical organization, zone‐specific matrix composition, and anisotropic biomechanical behavior of the native tissues. Finally, a vision is presented for how this field may continue to evolve in the future to empower the fabrication of scaffolds that serve as effective templates for guiding cellular assembly and organization toward the formation of functional cartilage and IVD tissues.
This progress report summarizes the state‐of‐the‐art in cartilage and intervertebral disc (IVD) decellularized extracellular matrices bioink preparation and 3D bioprinting applications, and discusses the future perspectives in this field to empower the fabrication of scaffolds that serve as effective templates for guiding cellular assembly and organization toward the formation of functional cartilage and IVD tissues.
•Students fit the stress relaxation behavior of biomaterials to viscoelastic models.•Students evaluated the impact of crosslinking on the stress-relaxation behavior.•Students studied the accuracy of ...each model by comparison to the experiment data.•Our evaluation indicates that the laboratory contributed to ABET learning outcomes.
Distance learning has become a prevalent method of delivering education to all types of student demographics. Here we present an online materials-related activity, which can be implemented into any course (traditional or online) related to chemical, mechanical, or biomedical engineering. Students use a Matlab graphical user interface (GUI) to predict the stress relaxation behavior of crosslinked biomaterials with three viscoelastic models, the Maxwell, Kelvin–Voigt, and standard linear. By analyzing provided experimental data, students evaluate the impact of crosslinking on the stress-relaxation behavior and learn the underlying molecular mechanisms that cause this behavior. Furthermore, students learn the accuracy of each model prediction by comparison to the experiment data. Overall, the activity highlights the importance of structure-property relationships in the technological advancement of biomedical materials. Our evaluation indicates that the laboratory was effectively conducted online, as it contributed to outcomes set forth for undergraduate chemical engineering students by Rowan University and ABET.
Because low back pain is frequently a result of intervertebral disc degeneration (IVDD), strategies to regenerate or repair the IVD are currently being investigated. Often, ex vivo disc cultures of ...non-human IVD organs or tissue explants are used that usually do not exhibit natural IVDD. Therefore, degenerative changes mimicking those reported in human IVDD need to be induced. To support researchers in selecting ex vivo disc cultures, a systematic search was performed for them and their potential use for studying human IVDD reviewed. Five degeneration induction categories (proinflammatory cytokines, injury/damage, degenerative loading, enzyme, and other) were identified in 129 studies across 7 species. Methods to induce degeneration are diverse and can induce mild to severe degenerative changes that progress over time, as described for human IVDD. The induced degenerative changes are model-specific and there is no "one-fits-all" IVDD induction method. Nevertheless, specific aspects of human IVDD can be well mimicked. Currently, spontaneously degenerated disc cultures from large animals capture human IVDD in most aspects. Combinatorial approaches of several induction methods using discs derived from large animals are promising to recapitulate pathological changes on several levels, such as cellular behaviour, extracellular matrix composition, and biomechanical function, and therefore better mimic human IVDD. Future disc culture setups might increase in complexity, and mimic human IVDD even better. As ex vivo disc cultures have the potential to reduce and even replace animal trials, especially during preclinical development, advancement of such models is highly relevant for more efficient and cost-effective clinical translation from bench-to-bedside.
Background
Intervertebral disc (IVD) disorders (e.g., herniation) directly contribute to back pain, which is a leading cause of global disability. Next‐generation treatments for IVD herniation need ...advanced preclinical testing to evaluate their ability to repair large defects, prevent reherniation, and limit progressive degeneration. This study tested whether experimental, injectable, and nonbioactive biomaterials could slow IVD degeneration in an ovine discectomy model.
Methods
Ten skeletally mature sheep (4–5.5 years) experienced partial discectomy injury with cruciate‐style annulus fibrosus (AF) defects and 0.1 g nucleus pulposus (NP) removal in the L1–L2, L2–L3, and L3–L4 lumbar IVDs. L4–L5 IVDs were Intact controls. IVD injury levels received: (1) no treatment (Injury), (2) poly (ethylene glycol) diacrylate (PEGDA), (3) genipin‐crosslinked fibrin (FibGen), (4) carboxymethylcellulose–methylcellulose (C‐MC), or (5) C‐MC and FibGen (FibGen + C‐MC). Animals healed for 12 weeks, then IVDs were assessed using computed tomography (CT), magnetic resonance (MR) imaging, and histopathology.
Results
All repaired IVDs retained ~90% of their preoperative disc height and showed minor degenerative changes by Pfirrmann grading. All repairs had similar disc height loss and Pfirrmann grade as Injury IVDs. Adhesive AF sealants (i.e., PEGDA and FibGen) did not herniate, although repair caused local endplate (EP) changes and inflammation. NP repair biomaterials (i.e., C‐MC) and combination repair (i.e., FibGen + C‐MC) exhibited lower levels of degeneration, less EP damage, and less severe inflammation; however, C‐MC showed signs of herniation via biomaterial expulsion.
Conclusions
All repair IVDs were noninferior to Injury IVDs by IVD height loss and Pfirrmann grade. C‐MC and FibGen + C‐MC IVDs had the best outcomes, and may be appropriate for enhancement with bioactive factors (e.g., cells, growth factors, and miRNAs). Such bioactive factors appear to be necessary to prevent injury‐induced IVD degeneration. Application of AF sealants alone (i.e., PEGDA and FibGen) resulted in EP damage and inflammation, particularly for PEGDA IVDs, suggesting further material refinements are needed.
This study evaluates the in vivo performance of four injectable, nonbioactive IVD repair biomaterial strategies could slow intervertebral disc (IVD) degeneration in an ovine discectomy model. All repaired IVDs retained ~90% of their preoperative disc height and showed minor degenerative changes by Pfirrmann grading. C‐MC and FibGen + C‐MC IVDs had the best outcomes, these treatments may be appropriate for enhancement with bioactive factors.
Hospital-acquired pneumonia (HAP) is associated with high mortality and costs, and frequently caused by multidrug-resistant (MDR) bacteria. Although prior antimicrobial therapy is a major risk factor ...for HAP, the underlying mechanism remains incompletely understood. Here, we demonstrate that antibiotic therapy in hospitalized patients is associated with decreased diversity of the gut microbiome and depletion of short-chain fatty acid (SCFA) producers. Infection experiments with mice transplanted with patient fecal material reveal that these antibiotic-induced microbiota perturbations impair pulmonary defense against MDR Klebsiella pneumoniae. This is dependent on inflammatory monocytes (IMs), whose fatty acid receptor (FFAR)2/3-controlled and phagolysosome-dependent antibacterial activity is compromized in mice transplanted with antibiotic-associated patient microbiota. Collectively, we characterize how clinically relevant antibiotics affect antimicrobial defense in the context of human microbiota, and reveal a critical impairment of IM´s antimicrobial activity. Our study provides additional arguments for the rational use of antibiotics and offers mechanistic insights for the development of novel prophylactic strategies to protect high-risk patients from HAP.
Wharton's jelly derived-mesenchymal stem cells (WJ-MSCs) have a same developmental origin with primordial germ cells. WJ-MSCs perhaps differentiate into oocyte and germ like-cells (OLCs/GLCs) in the ...presence of appropriate inducers. Human follicular fluid (FF) and cumulus cells conditioned medium (CCM) are naturally rich sources for oocyte development. The aim of this study was to evaluate WJ-MSCs potential for differentiating into OLCs and GLCs exposed to FF and CCM. WJ-MSCs were cultured in two different induction media (10% FF, 10% CCM) for 21 days. Morphological changes and expression of developmental genes were evaluated on days 0, 7, 14 and 21 of culture. Also, on 21st day of culture, the expression of oocyte and germ cell proteins investigated using immunofluorescence staining. Appearance of round shaped cells from 7th day onwards indicated that WJ-MSCs can differentiate into OLCs when exposed to FF and CCM. The size of produced OLCs and expression of oocyte specific genes and proteins were increased more positively in FF group rather than CCM group. Although, WJ-MSCs could differentiate into OLCs by FF and CCM, however, the induction potential of FF for producing OLCs was better than CCM.
Cell biology; Cell differentiation; Stem cells research; Embryology; Regenerative medicine; Wharton's jelly mesenchymal stem cells, Follicular fluid, Cumulus cells conditioned medium, Oocyte and germ like-cells
Compressive fracture can produce profound changes to the mechanical profile of a spine segment. Minimally invasive repair has the potential to restore both function and structural integrity to an ...injured spine. Use of both hydrogels to address changes to the disc, combined with polymethyl methacrylate (PMMA) to address changes to the vertebral body, has the potential to facilitate repair.
The purpose of this investigation was to determine if the combined use of hydrogel injection and PMMA could restore the mechanical profile of an axially injured spinal motion segment.
This is a basic science study evaluating a combination of hydrogel injection and vertebroplasty on restoring mechanics to compressively injured porcine spine motion segments.
Fourteen porcine spine motion segments were subject to axial compression until fracture using a dynamic servohydraulic testing apparatus. Rotational and compressive stiffness was measured for each specimen under the following conditions: initial undamaged, fractured, fatigue loading under compression, hydrogel injection, PMMA injection, and fatigue loading under compression. Group 1 received hydrogel injection followed by PMMA injection, whereas Group 2 received PMMA injection followed by hydrogel injection. This study was funded under a Natural Sciences and Engineering Research Council of Canada discovery grant.
PMMA injection was found to alter the compressive stiffness properties of axially injured spine motion segments, restoring values from Groups 1 and 2 to 89.3%±29.3% and 81%±27.9% of initial values respectively. Hydrogel injection was found to alter the rotational stiffness properties, restoring specimens in Groups 1 and 2 to 151.5%±81% and 177.2%±54.9% of initial values respectively. Prolonged restoration of function was not possible, however, after further fatigue loading.
Using this repair technique, replication of the mechanism of injury appears to cause a rapid deterioration in function of the motion segments. Containment of the hydrogel appears to be an issue with large breaches in the end plate, as it is posited to migrate into the cancellous bone of the vertebral body. Future work should attempt to evaluate methods in fully sealing the disc space.
PDF
