[Show abstract][Hide abstract] ABSTRACT: Background
Tendons are dense connective tissues subjected periodically to mechanical stress upon which complex responsive mechanisms are activated. These mechanisms affect not only the development of these tissues but also their healing. Despite of the acknowledged importance of the mechanical stress for tendon function and repair, the mechanotransduction mechanisms in tendon cells are still unclear and the elucidation of these mechanisms is a key goal in tendon research. Tendon stem/progenitor cells (TSPC) possess common adult stem cell characteristics, and are suggested to actively participate in tendon development, tissue homeostasis as well as repair. This makes them an important cell population for tendon repair, and also an interesting research target for various open questions in tendon cell biology. Therefore, in our study we focused on TSPC, subjected them to five different mechanical protocols, and investigated the gene expression changes by using semi-quantitative, quantitative PCR and western blotting technologies.
Among the 25 different genes analyzed, we can convincingly report that the tendon-related genes - fibromodulin, lumican and versican, the collagen I-binding integrins - α1, α2 and α11, the matrix metalloproteinases - MMP9, 13 and 14 were strongly upregulated in TSPC after 3 days of mechanical stimulation with 8% amplitude. Molecular signaling analyses of five key integrin downstream kinases suggested that mechanical stimuli are mediated through ERK1/2 and p38, which were significantly activated in 8% biaxial-loaded TSPC.
Our results demonstrate the positive effect of 8% mechanical loading on the gene expression of matrix proteins, integrins and matrix metalloproteinases, and activation of integrin downstream kinases p38 and ERK1/2 in TSPC. Taken together, our study contributes to better understanding of mechanotransduction mechanisms in TPSC, which in long term, after further translational research between tendon cell biology and orthopedics, can be beneficial to the management of tendon repair.
[Show abstract][Hide abstract] ABSTRACT: The C3 toxins from Clostridium botulinum (C3bot) and Clostridium limosum (C3lim) as well as C3-derived fusion proteins are selectively taken up into the cytosol of monocytes/macrophages where the C3-catalyzed ADP-ribosylation of Rho results in inhibition of Rho-signalling and characteristic morphological changes. Since the fusion toxin C2IN-C3lim was efficiently taken up into and inhibited proliferation of murine macrophage-like RAW 264.7 cells, its effects on RAW 264.7-derived osteoclasts were investigated. C2IN-C3lim was taken up into differentiated osteoclasts and decreased their resorption activity. In undifferentiated RAW 264.7 cells, C2IN-C3lim-treatment significantly decreased their differentiation into osteoclasts as determined by counting the multi-nucleated, TRAP-positive cells. This inhibitory effect was concentration- and time-dependent and most efficient when C2IN-C3lim was applied in the early stage of osteoclast-formation. A single-dose application of C2IN-C3lim at day 0 and its subsequent removal at day 1 reduced the number of osteoclasts in a comparable manner while C2IN-C3lim-application at later time points did not reduce the number of osteoclasts to a comparable degree. Control experiments with an enzymatically inactive C3 protein revealed that the ADP-ribosylation of Rho was essential for the observed effects. In conclusion, the results indicate that Rho-activity is crucial during the early phase of osteoclast-differentiation. Other bone cell types such as pre-osteoblastic cells were not affected by C2IN-C3lim. Due to their cell-type selective and specific mode of action, C3 proteins and C3-fusions might be valuable tools for targeted pharmacological manipulation of osteoclast formation and activity, which could lead to development of novel therapeutic strategies against osteoclast-associated diseases.
PLoS ONE 12/2013; 8(12):e85695. DOI:10.1371/journal.pone.0085695 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Regenerative strategies aim to restore the original biofunctionality of the intervertebral disc. Different biomaterials are available, which might support disc regeneration. In the present study, the prospects of success of two hydrogels functionalized with anti-angiogenic peptides and seeded with bone marrow derived mononuclear cells (BMC), respectively, were investigated in an ovine nucleotomy model.
In a one-step procedure iliac crest aspirates were harvested and, subsequently, separated BMC were seeded on hydrogels and implanted into the ovine disc. For the cell-seeded approach a hyaluronic acid-based hydrogel was used. The anti-angiogenic potential of newly developed VEGF-blockers was investigated on ionically crosslinked metacrylated gellan gum hydrogels. Untreated discs served as nucleotomy controls. 24 adult merino sheep were used. After 6 weeks histological, after 12 weeks histological and biomechanical analyses were conducted.
Biomechanical tests revealed no differences between any of the implanted and nucleotomized discs. All implanted discs significantly degenerated compared to intact discs. In contrast, there was no marked difference between implanted and nucleotomized discs. In tendency, albeit not significant, degeneration score and disc height index deteriorated for all but not for the cell-seeded hydrogels from 6 to 12 weeks. Cell-seeded hydrogels slightly decelerated degeneration.
None of the hydrogel configurations was able to regenerate biofunctionality of the intervertebral disc. This might presumably be caused by hydrogel extrusion. Great importance should be given to the development of annulus sealants, which effectively exploit the potential of (cell-seeded) hydrogels for biological disc regeneration and restoration of intervertebral disc functioning.
European Spine Journal 10/2013; 23(1). DOI:10.1007/s00586-013-2998-8 · 2.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The estimated frequency of MSCs in BM is about 0.001-0.01% of total nucleated cells. Most commonly, one applied therapeutic cell dose is about 1 -5 million MSCs/kg body weight, necessitating a reliable, fast and safe expansion system. The limited availability of MSCs demands for an extensive ex vivo amplification step to accumulate sufficient cell numbers. Human platelet lysate (PL) has proven to be a safe and feasible alternative to animal-derived serum as supplement for MSC cultivation. We have investigated the functionally closed automated cell culture hollow fiber bioreactor Quantum® cell expansion system as an alternative novel tool to conventional tissue flasks for efficient clinical-scale MSC isolation and expansion from bone marrow using PL. Cells expanded in the Quantum system fulfilled MSC criteria as shown by flow cytometry and adipogenic, chondrogenic and osteogenic differentiation capacity.Cell surface expression of a variety of chemokine receptors, adhesion molecules, and additional MSC markers was monitored for several passages by flow-cytometry. The levels of critical media components like glucose and lactate were analysed. PDGF-AA, PDGF-AB/BB, bFGF, TGF-β1, sICAM-1, sVCAM-1, RANTES, GRO, VEGF, sCD40L, IL-6 were assessed using a LUMINEX platform. Originally optimized for the use of fetal calf serum (FCS) as supplement and fibronectin as coating reagent, we succeeded to obtain an average of more than 100x10⁶ of MSCs from as little as 18.8 to 28.6 mL of BM aspirate using PL. We obtained similar yields of MSCs/μL BM in the FCS-containing and the xenogen-free expansion system. The Quantum system reliably produces a cellular therapeutic dose in a functionally closed system that requires minimal manipulation. Both isolation and expansion is possible using FCS or PL as supplement. Coating of the hollow fibres of the bioreactor is mandatory when loading MSCs. Fibronectin, PL and human plasma may serve as coating reagents.
[Show abstract][Hide abstract] ABSTRACT: Mesenchymal stromal cells (MSC) have gained importance in tissue repair, tissue engineering and in immunosupressive therapy during the last years. Due to the limited availability of MSC in the bone marrow, ex vivo amplification prior to clinical application is requisite to obtain therapeutic applicable cell doses. Translation of preclinical into clinical-grade large-scale MSC expansion necessitates precise definition and standardization of all procedural parameters including cell seeding density, culture medium and cultivation devices. While xenogeneic additives such as fetal calf serum are still widely used for cell culture, its use in the clinical context is associated with many risks, such as prion and viral transmission or adverse immunological reactions against xenogeneic components.
We established animal-free expansion protocols using platelet lysate as medium supplement and thereby could confirm its safety and feasibility for large-scale MSC isolation and expansion. Five different GMP-compliant standardized protocols designed for the safe, reliable, efficient and economical isolation and expansion of MSC was performed and MSC obtained were analyzed for differentiation capacity by qPCR and histochemistry. Expression of standard MSC markers as defined by the International Society for Cellular Therapy as well as expression of additional MSC markers and of various chemokine and cytokine receptors was analysed by flow cytometry. Changes of metabolic markers and cytokines in the medium were addressed using the LUMINEX platform.
The five different systems for isolation and expansion of MSC described in this study are all suitable to produce at least 100 millions of MSC, which is commonly regarded as a single clinical dose. Final products are equal according to the minimal criteria for MSC defined by the ISCT. We showed that chemokine and integrin receptors analyzed had the same expression pattern, suggesting that MSC from either of the systems show equal characteristics of homing and adhesion.
PLoS ONE 08/2012; 7(8):e43255. DOI:10.1371/journal.pone.0043255 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to prove the effect of cyclic uniaxial intermittent strain on the mRNA expression of ligament-specific marker genes in human mesenchymal stem cells (MSC) and anterior cruciate ligament-derived fibroblasts (ACL-fibroblasts) seeded onto a novel textured poly(L-lactide) scaffold (PLA scaffold). Cell-seeded scaffolds were mechanically stimulated by cyclic uniaxial stretching. The expression of ligament matrix gene markers: collagen types I and III, fibronectin, tenascin C and decorin, as well as the proteolytic enzymes matrix metalloproteinase MMP-1 and MMP-2 and their tissue specific inhibitors TIMP-1 and TIMP-2 was investigated by analysing the mRNA expression using reverse transcriptase polymerase chain reaction and related to the static control. In ACL-fibroblasts seeded on PLA, mechanical load induced up-regulation of collagen types I and III, fibronectin and tenascin C. No effect of mechanical stimulation on the expression of ligament marker genes was found in undifferentiated MSC seeded on PLA. The results indicated that the new textured PLA scaffold could transfer the mechanical load to the ACL-fibroblasts and improved their ligament phenotype. This scaffold might be suitable as a cell-carrying component of ACL prostheses.
Journal of Materials Science Materials in Medicine 06/2012; 23(10):2575-82. DOI:10.1007/s10856-012-4710-7 · 2.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper explores the use of selective laser sintering (SLS) for the generation of bone tissue engineering scaffolds from polycaprolactone (PCL) and PCL/tricalcium phosphate (TCP). Different scaffold designs are generated, and assessed from the point of view of manufacturability, porosity and mechanical performance. Large scaffold specimens are produced, with a preferred design, and are assessed through an in vivo study of the critical size bone defect in sheep tibia with subsequent microscopic, histological and mechanical evaluation. Further explorations are performed to generate scaffolds with increasing TCP content. Scaffold fabrication from PCL and PCL/TCP mixtures with up to 50 mass% TCP is shown to be possible. With increasing macroporosity the stiffness of the scaffolds is seen to drop; however, the stiffness can be increased by minor geometrical changes, such as the addition of a cage around the scaffold. In the animal study the selected scaffold for implantation did not perform as well as the TCP control in terms of new bone formation and the resulting mechanical performance of the defect area. A possible cause for this is presented.
[Show abstract][Hide abstract] ABSTRACT: The skeletal and the immune system are not two independent systems, rather, there are multifaceted and complex interactions between the different cell types of both systems and there are several shared cytokines. As a part of the innate immunity, the complement system was found to be an important link between bone and immunity. Complement proteins appear to be involved in bone development and homeostasis, and specifically influence osteoblast and osteoclast activity. This review describes the complex mutual regulation of the two systems, and indicates some of the negative side effects as a result of inappropriate or excessive complement activation.
[Show abstract][Hide abstract] ABSTRACT: There is evidence that complement components regulate cytokine production in osteoblastic cells, induce cell migration in mesenchymal stem cells, and play a regulatory role in normal enchondral bone formation. We proved the hypothesis that complement might be involved in bone healing after fracture.
We investigated the expression of the key anaphylatoxin receptor C5aR during fracture healing in rats by immunostaining after 1, 3, 7, 14, and 28 days. C5aR expression was additionally analyzed in human mesenchymal stem cells (hMSC) during osteogenic differentiation, in human primary osteoblasts, and osteoclasts by reverse transcriptase polymerase chain reaction and immunostaining. Receptor functionality was proven by the migratory response of cells to C5a in a Boyden chamber.
C5aR was expressed in a distinct spatial and temporal pattern in the fracture callus by differentiated osteoblast, chondroblast-like cells in cartilaginous regions, and osteoclasts. In vitro C5aR was expressed by osteoblasts, osteoclasts, and hMSC undergoing osteogenic differentiation. C5aR was barely expressed by undifferentiated hMSC but was significantly induced after osteogenic differentiation. C5aR activation by C5a induced strong chemotactic activity in osteoblasts, and in hMSC, which had undergone osteogenic differentiation, being abolished by a specific C5aR antagonist. In hMSC, C5a induced less migration reflecting their low level of C5aR expression.
Our in vitro and in vivo results demonstrated the presence of C5aR in bone forming osteoblasts and bone resorbing osteoclasts. It is suggested that C5aR might play a regulatory role in fracture healing in intramembranous and in enchondral ossification, one possible function being the regulation of cell recruitment.
The Journal of trauma 03/2011; 71(4):952-60. DOI:10.1097/TA.0b013e3181f8aa2d · 2.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recently, it was demonstrated that phosphonate-functionalised nanoparticles were successfully taken up by mesenchymal stem cells without influencing their viability and differentiation capacity, suggesting that they may provide a promising basis for the development of nanoparticles for drug delivery or cell labelling. The present study aimed to investigate the effects of these nanoparticles on osteoclast formation and activity as well as on the inflammatory response of osteoclasts and osteoblasts. The intracellular uptake of the particles by human osteoclasts and osteoblasts was demonstrated by confocal laser scanning microscopy, transmission electron microscopy and fluorescence microscopy. The expression of tartrate-resistant acid phosphatase, carboanhydrase II, cathepsin K, calcitonin receptor and osteoclast-specific vacuolar proton pump subunit TCIRG1 as well as actin ring formation were not significantly altered in osteoclasts by particle treatment, as demonstrated by cytochemical staining and immunostaining. Active calcium phosphate resorption by osteoclasts was also not significantly influenced by the particles. The expression and secretion of pro-inflammatory cytokines (IL-6, IL-1β) by osteoclasts and osteoblasts and the expression of osteoclast-regulating genes (M-CSF, OPG, RANKL) in osteoblasts were similarly not significantly affected. In conclusion, phosphonate-functionalised nanoparticles did not affect osteoclast formation and activity either directly or indirectly, suggesting that they could provide a promising tool for the development of particle-based treatments for anti-resorptive therapies.
[Show abstract][Hide abstract] ABSTRACT: Schlüsselwörter Mechanotransduktion, mechanische Belas-tung, WNT/β-Catenin-und Östrogenrezeptor-Signalweg, Knochenzellen Zusammenfassung Die Erhaltung der Knochenmasse wird durch die Interaktion von verschiedenen Faktoren, einschließlich systemischen Hormonen, loka-len Wachstumsfaktoren und mechanischer Be-lastung reguliert. Verantwortlich für die adap-tive Antwort von Knochenzellen auf mechani-sche Belastung sind zelluläre Prozesse der Auf-nahme, der Umwandlung des physikalischen Stimulus in strukturelle und biochemische Re-aktionen, die als Mechanotransduktion be-zeichnet werden. Osteoblasten und vor allem Osteozyten sind die mechanosensorischen Zellen des Knochens. Sie benötigen den me-chanischen Stimulus für ihre Vitalität und Funktion. Die in der Mechanotransduktion ak-tivierten Signalwege wirken anabol auf die Knochenmasse. Hierzu gehören der WNT (win-gless integration)/β-Catenin und der Östro-genrezeptor (ER)-Signalweg, die beide eine entscheidende Rolle in der Regulation von Knochenbildung und Knochenresorption spie-len. Eine Aufklärung der Interaktion der Sig-nalwege in der Mechanotransduktion durch geeignete In-vitro-und In-vivo-Experimente ist sinnvoll, um in Zukunft effektiv mecha-nische Signale in der Prävention und Interven-tion von/bei osteodegenerativen Krankheiten, wie z. B. Osteoporose, nutzen zu können.
[Show abstract][Hide abstract] ABSTRACT: The combined use of nanoparticles and mesenchymal stem cells (MSC) in regenerative medicine requires the incorporation of the particles and, at the same time, undisturbed cell viability and maintenance of the multi-lineage potential of MSC. The aim of this study was to investigate the uptake of novel phosphonate-functionalised polystyrene nanoparticles prepared by miniemulsion polymerisation. After exposition of human MSC to the particles, their uptake and localisation were analysed by flow cytometry, confocal laser scanning microscopy (CLSM), and transmission electron microscopy (TEM). The osteogenic, adipogenic and chondrogenic differentiation potential was examined by analysing representative marker genes by RT-PCR. Flow cytometry revealed that after 5 and 16 days more than 98% of the MSC and of the cells, which underwent osteogenic and adipogenic differentiation were positive for particle association. CLSM and TEM demonstrated the successful intracellular incorporation of the particles without using any transfection agents and their presence over the cultivation period. The cell viability was found to be unaffected. Particle treated MSC maintained their potential for osteogenic, adipogenic and chondrogenic differentiation. It was concluded that the surface functionalisation with phosphonate groups provides a promising basis for the development of nanoparticles with high intracellular uptake rates for drug delivery or cell labelling.
[Show abstract][Hide abstract] ABSTRACT: Osteoclast activity has traditionally been regarded as restricted to bone resorption but there is some evidence that also non-resorbing osteoclasts might influence osteoblast activity. The aim of the present study was to further investigate the hypothesis of an anabolic function of non-resorbing osteoclasts by investigating their capability to recruit mesenchymal stem cells (MSC) and to provoke their differentiation toward the osteogenic lineage. Bone-marrow-derived human MSC were exposed to conditioned media (CM) derived from non-resorbing osteoclast cultures, which were generated from human peripheral blood monocytes. Osteogenic marker genes (transcription factor Runx2, bone sialoprotein, alkaline phosphatase (AP), and osteopontin) were significantly increased. Osteogenic differentiation (OD) was also proved by von Kossa and AP staining occurred in the same range as in MSC cultures stimulated with osteogenic supplements. Chemotactic responses of MSC were measured with a modified Boyden chamber assay. CM from osteoclast cultures induced a strong migratory response in MSC, which was greatly reduced in the presence of an anti-human platelet-derived growth factor (PDGF) receptor beta antibody. Correspondingly, significantly increased PDGF-BB concentrations were measured in the CM using a PDGF-BB immunoassay. CM derived from mononuclear cell cultures did not provoke MSC differentiation and had a significantly lower migratory effect on MSC suggesting that the effects were specifically mediated by osteoclasts. In conclusion, it can be suggested that human non-resorbing osteoclasts induce migration and OD of MSC. While effects on MSC migration might be mainly due to PDGF-BB, the factors inducing OD remain to be elucidated.
[Show abstract][Hide abstract] ABSTRACT: Bone adaptation to mechanical load is accompanied by changes in gene expression of bone-forming cells. Less is known about mechanical effects on factors controlling bone resorption by osteoclasts. Therefore, we studied the influence of mechanical loading on several key genes modulating osteoclastogenesis. Human osteoblasts were subjected to various cell stretching protocols. Quantitative RT-PCR was used to evaluate gene expression. Cell stretching resulted in a significant up-regulation of receptor activator of nuclear factor-kappaB ligand (RANKL) immediate after intermittent loading (3x3h, 3x6h, magnitude 1%). Continuous loading, however, had no effect on RANKL expression. The expression of osteoprotegerin (OPG), macrophage-colony stimulating factor (M-CSF), and osteoclast inhibitory lectin (OCIL) was not significantly altered. The data suggested that mechanical loading could influence osteoclasts recruitment by modulating RANKL expression in human osteoblasts and that the effects might be strictly dependent on the quality of loading.
Biochemical and Biophysical Research Communications 05/2008; 368(3):582-7. DOI:10.1016/j.bbrc.2008.01.106 · 2.28 Impact Factor