Sibylle Grad

Last Name

Grad

First Name

Sibylle

ORCID

0000-0001-9552-3653

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01630 - Lehre HEST

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Publications 1 - 10 of 14

Multiaxial rotational loading compromises the transition zone of the intervertebral disc: Ex vivo study using next-generation bioreactors
Šećerović, Amra; Ristaniemi, Aapo; Crivelli, Francesco; et al. (2025)
Bioengineering & Translational Medicine
Bioreactors have become indispensable tools in spine research, enabling long-term intervertebral disc culture under controlled biological and mechanical conditions. Conventional systems are often limited to uniaxial loading, restricting their ability to replicate the complex, multidirectional biomechanics of the spine. To overcome this limitation, we developed a next-generation bioreactor capable of simulating multiaxial motions while preserving the disc's biological environment. In this study, we investigated the effects of complex loading patterns on early disc degeneration by subjecting bovine whole-organ discs to combined extension, lateral bending, and torsion at 0.3 Hz for 2 h daily over 14 days. To assess the impact of loading magnitude and the specific contribution of torsion, discs were exposed to either low- or high-angle rotations, with or without torsional loading at higher angles. Histological analysis revealed a marked loss of glycosaminoglycans (GAG) and collagen type II within the inner annulus fibrosus and transitional nucleus pulposus (NP), encompassing the transition zone (TZ), as well as GAG depletion in the central NP. Matrix degradation was observed across all loading conditions, with the most severe breakdown occurring under high-angle extension, bending, and torsion. All loading regimes induced cell death in the TZ and central NP, although torsion-free loading better maintained cell viability. These findings highlight the TZ, alongside the commonly affected NP, as a critical early site of degeneration. The study further underscores the importance of incorporating multiaxial loading in disc degeneration models and provides new insights into the biomechanical mechanisms underlying disc pathology.
Decellularized extracellular matrix particle-based biomaterials for cartilage repair applications
Guo, Peng; Jiang, Nan; Mini, Carina; et al. (2023)
Journal of Materials Science and Technology
Cartilage Decellularized ExtraCellular Matrix (dECM) materials have shown promising cartilage regeneration capacity due to their chondrogenic bioactivity. However, the limited retention of ECM components and the reduced integrity of functional ECM molecules during traditional decellularization processes impair the biomimicry of these materials. The current study aims to fabricate biomimetic materials containing decellularized cartilage particles that have an intact molecular structure and native composition as biomaterial inks and hydrogels for cartilage repair. For this, we established a novel two-fraction decellularization strategy for the preparation of reconstituted dECM (rdECM) particles by mixing the two-fraction components, as well as a one-fraction decellularization strategy for the preparation of biomimetic dECM (bdECM) particles. Hyaluronic acid-tyramine (THA) hydrogels containing rdECM or bdECM particles were produced and characterized via rheological test, swelling and stability evaluation, and compression test. The results showed that our novel decellularization strategies preserved intact proteoglycans and collagen at a higher retention rate with adequate DNA removal compared to traditional methods of decellularization. The addition of rdECM or bdECM particles significantly increased the shear moduli of the THA bioinks while preserving their shear-thinning properties. bdECM particle-embedded THA hydrogels also achieved long-term stability with a swelling ratio of 70% and high retention of glycosaminoglycans and collagen after long-term incubation, while rdECM particle-embedded THA hydrogels showed unsatisfactory stability as self-standing biomaterials. Compared to pure THA hydrogels, the addition of bdECM particles significantly enhanced the compression moduli. In summary, our decellularization methods are successful in the retention of functional and intact cartilage components with high yield. Both rdECM and bdECM particles can be supplemented in THA bioinks for biomimetic cartilage 3D printing. Hydrogels with cartilage bdECM particles possess the functional structure and the natural composition of cartilage ECM, long-term stability, and enhanced mechanical properties, and are promising biomaterials for cartilage repair.
Small molecules of herbal origin for osteoarthritis treatment: in vitro and in vivo evidence
Zhang, Penghui; Li, Kaihu; Kamali, Amir; et al. (2022)
Arthritis Research & Therapy
Osteoarthritis (OA) is one of the most common musculoskeletal degenerative diseases and contributes to heavy socioeconomic burden. Current pharmacological and conventional non-pharmacological therapies aim at relieving the symptoms like pain and disability rather than modifying the underlying disease. Surgical treatment and ultimately joint replacement arthroplasty are indicated in advanced stages of OA. Since the underlying mechanisms of OA onset and progression have not been fully elucidated yet, the development of novel therapeutics to prevent, halt, or reverse the disease is laborious. Recently, small molecules of herbal origin have been reported to show potent anti-inflammatory, anti-catabolic, and anabolic effects, implying their potential for treatment of OA. Herein, the molecular mechanisms of these small molecules, their effect on physiological or pathological signaling pathways, the advancement of the extraction methods, and their potential clinical translation based on in vitro and in vivo evidence are comprehensively reviewed.
Early markers of mechanical modulation in whole bovine intervertebral discs loaded in a multiaxial bioreactor
Kubincova, Barbora; Muerner, Marcia; Ma, Junxuan; et al. (2026)
European Spine Journal
Purpose Intervertebral disc degeneration (IVDD) is a major contributor to low back pain (LBP), with mechanical overloading recognized as a driver of disc pathology. This study investigated early responses of bovine caudal intervertebral discs (IVDs) to repetitive multiaxial loading and assessed effects on nociceptive sensitization. Methods Whole IVDs were cultured ex vivo for 3 or 7 days either free-swelling or under multiaxial loading (0.2 MPa compression, 0–6° flexion, 0–4° torsion, 0.2 Hz, 4 h/day). Disc height, biomechanics, gene expression, biochemical markers, collagen integrity, and cell viability were evaluated. Conditioned medium (CM) from IVDs was applied to primary dorsal root ganglion (DRG) neurons to assess calcium responses and neurite outgrowth. Results Multiaxial loading induced rapid, region-specific molecular changes, particularly in the outer annulus fibrosus, with upregulation of inflammatory (IL6) and catabolic (MMP13) genes and mild increases in glycosaminoglycan and nitric oxide release. DRG neurons exposed to CM from loaded IVDs exhibited enhanced capsaicin-evoked calcium responses and increased neurite branching, especially in CGRP-positive nociceptors, indicating early discogenic sensitization. Collagen denaturation showed a trend toward higher levels in loaded IVDs, while cell viability, tissue structure, and biomechanical properties remained preserved. Conclusion Multiaxial loading at the selected magnitude induced early molecular signs of degeneration and neuronal sensitization without detectable alterations in cell viability, tissue structure, or biomechanics, contributing to our understanding of mechanically induced impact on the IVD. Ex vivo multiaxial loading in bioreactors provides a physiologically relevant platform to study the initiation and progression of IVDD and associated discogenic pain mechanisms.
Homing of vertebral-delivered mesenchymal stromal cells for degenerative intervertebral discs repair - an in vivo proof-of-concept study
Schol, Jordy; Sakai, Daisuke; Warita, Takayuki; et al. (2023)
JOR Spine
Introduction Cell transplantation shows promising results for intervertebral disc (IVD) repair, however, contemporary strategies present concerns regarding needle puncture damage, cell retention, and straining the limited nutrient availability. Mesenchymal stromal cell (MSC) homing is a natural mechanism of long-distance cellular migration to sites of damage and regeneration. Previous ex vivo studies have confirmed the potential of MSC to migrate over the endplate and enhance IVD-matrix production. In this study, we aimed to exploit this mechanism to engender IVD repair in a rat disc degeneration model. Methods Female Sprague Dawley rats were subjected to coccygeal disc degeneration through nucleus pulposus (NP) aspiration. In part 1; MSC or saline was transplanted into the vertebrae neighboring healthy or degenerative IVD subjected to irradiation or left untouched, and the ability to maintain the IVD integrity for 2 and 4 weeks was assessed by disc height index (DHI) and histology. For part 2, ubiquitously GFP expressing MSC were transplanted either intradiscally or vertebrally, and regenerative outcomes were compared at days 1, 5, and 14 post-transplantation. Moreover, the homing potential from vertebrae to IVD of the GFP(+) MSC was assessed through cryosection mediated immunohistochemistry. Results Part 1 of the study revealed significantly improved maintenance of DHI for IVD vertebrally receiving MSC. Moreover, histological observations revealed a trend of IVD integrity maintenance. Part 2 of the study highlighted the enhanced DHI and matrix integrity for discs receiving MSC vertebrally compared with intradiscal injection. Moreover, GFP rates highlighted MSC migration and integration in the IVD at similar rates as the intradiscally treated cohort. Conclusion Vertebrally transplanted MSC had a beneficial effect on the degenerative cascade in their neighboring IVD, and thus potentially present an alternative administration strategy. Further investigation will be needed to determine the long-term effects, elucidate the role of cellular homing versus paracrine signaling, and validate our observations on a large animal model.
In Vitro Evaluation of a Nanoparticle-Based mRNA Delivery System for Cells in the Joint
Sturm, Lisa; Schwemberger, Bettina; Menzel, Ursula; et al. (2021)
Biomedicines
Biodegradable and bioresponsive polymer-based nanoparticles (NPs) can be used for oligonucleotide delivery, making them a promising candidate for mRNA-based therapeutics. In this study, we evaluated and optimized the efficiency of a cationic, hyperbranched poly(amidoamine)s-based nanoparticle system to deliver tdTomato mRNA to primary human bone marrow stromal cells (hBMSC), human synovial derived stem cells (hSDSC), bovine chondrocytes (bCH), and rat tendon derived stem/progenitor cells (rTDSPC). Transfection efficiencies varied among the cell types tested (bCH 28.4% ± 22.87, rTDSPC 18.13% ± 12.07, hBMSC 18.23% ± 14.80, hSDSC 26.63% ± 8.81) and while an increase of NPs with a constant amount of mRNA generally improved the transfection efficiency, an increase of the mRNA loading ratio (2:50, 4:50, or 6:50 w/w mRNA:NPs) had no impact. However, metabolic activity of bCHs and rTDSPCs was significantly reduced when using higher amounts of NPs, indicating a dose-dependent cytotoxic response. Finally, we demonstrate the feasibility of transfecting extracellular matrix-rich 3D cell culture constructs using the nanoparticle system, making it a promising transfection strategy for musculoskeletal tissues that exhibit a complex, dense extracellular matrix.
Physiological and degenerative loading of bovine intervertebral disc in a bioreactor: A finite element study of complex motions
Ristaniemi, Aapo; Šećerović, Amra; Dischl, Vincent; et al. (2023)
Journal of the Mechanical Behavior of Biomedical Materials
Intervertebral disc (IVD) degeneration and regenerative therapies are commonly studied in organ-culture experiments with uniaxial compressive loading. Recently, in our laboratory, we established a bioreactor system capable of applying loads in six degrees-of-freedom (DOF) to bovine IVDs, which replicates more closely the complex multi-axial loading of the IVD in vivo. However, the magnitudes of loading that are physiological (able to maintain cell viability) or mechanically degenerative are unknown for load cases combining several DOFs. This study aimed to establish physiological and degenerative levels of maximum principal strains and stresses in the bovine IVD tissue and to investigate how they are achieved under complex load cases related to common daily activities. The physiological and degenerative levels of maximum principal strains and stresses were determined via finite element (FE) analysis of bovine IVD subjected to experimentally established physiological and degenerative compressive loading protocols. Then, complex load cases, such as a combination of compression + flexion + torsion, were applied on the FE-model with increasing magnitudes of loading to discover when physiological and degenerative tissue strains and stresses were reached. When applying 0.1 MPa of compression and ±2–3° of flexion and ±1–2° of torsion the investigated mechanical parameters remained at physiological levels, but with ±6–8° of flexion in combination with ±2–4° of torsion, the stresses in the outer annulus fibrosus (OAF) exceeded degenerative levels. In the case of compression + flexion + torsion, the mechanical degeneration likely initiates at the OAF when loading magnitudes are high enough. The physiological and degenerative magnitudes can be used as guidelines for bioreactor experiments with bovine IVDs.
Chemonucleolysis combined with dynamic loading for inducing degeneration in bovine caudal intervertebral discs
Vernengo, Andrea; Bumann, Helen; Kluser, Nadine; et al. (2023)
Frontiers in Bioengineering and Biotechnology
Chemonucleolysis has become an established method of producing whole organ culture models of intervertebral disc (IVD) degeneration. However, the field needs more side-by-side comparisons of the degenerative effects of the major enzymes used in chemonucleolysis towards gaining a greater understanding of how these organ culture models mimic the wide spectrum of characteristics observed in human degeneration. In the current work we induced chemonucleolysis in bovine coccygeal IVDs with 100 µL of papain (65 U/mL), chondroitinase ABC (chABC, 5 U/mL), or collagenase II (col’ase, 0.5 U/mL). Each enzyme was applied in a concentration projected to produce moderate levels of degeneration. After 7 days of culture with daily dynamic physiological loading (0.02–0.2 MPa, 0.2 Hz, 2 h), the cellular, biochemical and histological properties of the IVDs were evaluated in comparison to a PBS-injected control. Papain and collagenase, but not chABC, produced macroscopic voids in the tissues. Compared to day 0 intact IVDs, papain induced the greatest magnitude glycosaminoglycan (GAG) loss compared to chABC and col’ase. Papain also induced the greatest height loss (3%), compared to 0.7%, 1.2% and 0.4% for chABC, col’ase, and PBS, respectively. Cell viability in the region adjacent to papain and PBS-injection remained at nearly 100% over the 7-day culture period, whereas it was reduced to 60%–70% by chABC and col’ase. Generally, enzyme treatment tended to downregulate gene expression for major ECM markers, type I collagen (COL1), type II collagen (COL2), and aggrecan (ACAN) in the tissue adjacent to injection. However, chABC treatment induced an increase in COL2 gene expression, which was significant compared to the papain treated group. In general, papain and col’ase treatment tended to recapitulate aspects of advanced IVD degeneration, whereas chABC treatment captured aspects of early-stage degeneration. Chemonucleolysis of whole bovine IVDs is a useful tool providing researchers with a robust spectrum of degenerative changes and can be utilized for examination of therapeutic interventions.
Toward the Next Generation of Spine Bioreactors: Validation of an Ex Vivo Intervertebral Disc Organ Model and Customized Specimen Holder for Multiaxial Loading
Secerovic, Amra; Ristaniemi, Aapo; Cui, Shangbin; et al. (2022)
ACS Biomaterials Science & Engineering
A new generation of bioreactors with integrated six degrees of freedom (6 DOF) aims to mimic more accurately the natural intervertebral disc (IVD) load. We developed and validated in a biological and mechanical study a specimen holder and corresponding ex vivo IVD organ model according to the bioreactor requirements for multiaxial loading and a long-term IVD culture. IVD height changes and cell viability were compared between the 6 DOF model and the standard 1 DOF model throughout the 3 weeks of cyclic compressive loading in the uniaxial bioreactor. Furthermore, the 6 DOF model and holder were loaded for 9 days in the multiaxial bioreactor under development using the same conditions, and the IVDs were evaluated for cell viability. The interface of the IVD model and specimen holder, enhanced with fixation screws onto the bone, was tested in compression, torsion, lateral bending, and tension. Additionally, critical motions such as tension and bending were assessed for a combination of side screws and top screws or side screws and adhesive. The 6 DOF model loaded in the uniaxial bioreactor maintained similar cell viability in the IVD regions as the 1 DOF model. The viability was high after 2 weeks throughout the whole IVD and reduced by more than 30% in the inner annulus fibrous after 3 weeks. Similarly, the IVDs remained highly viabile when cultured in the multiaxial bioreactor. In both models, IVD height changes after loading were in the range of typical physiological conditions. When differently directed motions were applied, the holder-IVD interface remained stable under hyper-physiological loading levels using a side screw approach in compression and torsion and the combination of side and top screws in tension and bending. We thus conclude that the developed holding system is mechanically reliable and biologically compatible for application in a new generation of multiaxial bioreactors.
Engineering Sensory Ganglion Multicellular System to Model Tissue Nerve Ingrowth
Ma, Junxuan; Eglauf, Janick; Grad, Sibylle; et al. (2024)
Advanced Science
Discogenic pain is associated with deep nerve ingrowth in annulus fibrosus tissue (AF) of intervertebral disc (IVD). To model AF nerve ingrowth, primary bovine dorsal root ganglion (DRG) micro-scale tissue units are spatially organised around an AF explant by mild hydrodynamic forces within a collagen matrix. This results in a densely packed multicellular system mimicking the native DRG tissue morphology and a controlled AF-neuron distance. Such a multicellular organisation is essential to evolve populational-level cellular functions and in vivo-like morphologies. Pro-inflammatory cytokine-primed AF demonstrates its neurotrophic and neurotropic effects on nociceptor axons. Both effects are dependent on the AF-neuron distance underpinning the role of recapitulating inter-tissue/organ anatomical proximity when investigating their crosstalk. This is the first in vitro model studying AF nerve ingrowth by engineering mature and large animal tissues in a morphologically and physiologically relevant environment. The new approach can be used to biofabricate multi-tissue/organ models for untangling pathophysiological conditions and develop novel therapies.

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Sibylle Grad

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