Papers by Manuela T Raimondi
Micromachines, 2014
We applied two-photon polymerization to fabricate 3D synthetic niches arranged in complex pattern... more We applied two-photon polymerization to fabricate 3D synthetic niches arranged in complex patterns to study the effect of mechano-topological parameters on morphology, renewal and differentiation of rat mesenchymal stromal cells. Niches were formed in a photoresist with low auto-fluorescence, which enabled the clear visualization of the fluorescence emission of the markers used for biological diagnostics within the internal niche structure. The niches were structurally stable in culture up to three weeks. At three weeks of expansion in the niches, cell density increased by almost 10-fold and was 67% greater than in monolayer culture. Evidence of lineage commitment was observed in monolayer culture surrounding the structural niches, and within cell aggregates, but not inside the niches. Thus, structural niches were able not only to direct stem cell homing and colony formation, but also to guide aggregate formation, providing increased surface-to-volume ratios and space for stem cells to adhere and renew, respectively.
Journal of Biomechanics, 2006
devices, subjected to a graded series of strains and then processed for SEM and TEM. Results and ... more devices, subjected to a graded series of strains and then processed for SEM and TEM. Results and Discussion: The collagen meshwork within the superficial layer was reoriented in the direction of applied strain, whether the strain was applied parallel or perpendicular to the split lines. At 0% strain, a fibrillar meshwork within the articular surface was predominantly oriented parallel to the split lines. As strain increased, it became reoriented in the direction of applied strain. The perpendicular group required much greater strain for complete collagen reorientation than the parallel group. Furthermore the collagen meshwork within the middle and deep layers was reoriented in the direction of applied strains regardless of its original orientation, i.e. random in the middle layer and perpendicular to the surface in the deep layer. Greater strain was required for collagen reorientation in the deeper layers than the superficial one.
Biomedical Microdevices, 2008
This paper presents a software framework for the computational modeling of tissue engineering exp... more This paper presents a software framework for the computational modeling of tissue engineering experiments, aimed to supplement and extend the empirical techniques currently employed in tissue engineering. The code included a model of cell population dynamics coupled to a finite element model of oxygen diffusion and consumption at the macroscale level, including the scaffold and the culture medium, and at
Bioreactors allowing culture medium perfusion overcome diffusion limitations associated with stat... more Bioreactors allowing culture medium perfusion overcome diffusion limitations associated with static culturing, and provide flow-mediated mechanical stimuli. Currently, one of the main issues in bioreactors design is to build a set up which may provide the required nutrients, optimizing the mechanical stimulation on the cells. However, in most of the direct-perfusion systems currently available, the hydrodynamic environment imposed to cells
Biomaterials, 2000
This paper reports the study performed on four titanium nitride (TiN) coated prosthetic femoral h... more This paper reports the study performed on four titanium nitride (TiN) coated prosthetic femoral heads collected at revision surgery together with patient data. Surface topology has been examined using Scanning Electron Microscopy (SEM) and elemental analysis of both coating and substrate have been evaluated using energy-dispersive X-ray spectrometry. Quantitative assessment of the surface topography is achieved using contacting profilometry. The
Journal of Applied Biomaterials & Functional Materials, 2012
Mechanical properties of the extra-cellular matrix (ECM) such as stiffness mediate cell signaling... more Mechanical properties of the extra-cellular matrix (ECM) such as stiffness mediate cell signaling, proliferation, migration, and differentiation. Within this context, we developed a method to estimate in vitro the stress-strain field induced by contraction of cardiovascular progenitor cells on substrates of controlled stiffness. Two alginate-agarose hydrogels were polymerized and mechanically characterized under compression. The hydrogels showed different levels of stiffness, mimicking either normal or pathologic ECM of the cardiac tissue, with an average compressive equilibrium modulus of 3 and 25 kPa, respectively. To estimate substrate deformation induced by the adhering cells, fluorescent microspheres were included under the surface layer of the hydrogels as displacement trackers. The hydrogels were polymerized in multiwell plates and seeded with cells that were allowed to adhere for 24 hours. On the softer substrate, images of the substrate surface and the cells were acquired using time-lapse fluorescence microscopy. Image processing enabled tracking the microsphere movements and mapping local substrate deformation because of tensile stresses produced by the cells. The resulting tensile stresses could then be calculated from measured stiffness. The substrate strains ranged between a maximum contraction of -26.5% to a maximum stretching of 19.8%. The calculated stresses ranged between a maximum compression of -0.53 kPa to a maximum tension of 0.4 kPa (nN/µm²). These results may help to interpret experimental findings, showing important differences in cell morphology and expression of phenotypic markers, induced by culturing cells on substrates with different mechanical properties.
Cell and Tissue Banking, 2014
We analyzed specific features of chondrocytes as cellular yield, cell doubling rates and the depe... more We analyzed specific features of chondrocytes as cellular yield, cell doubling rates and the dependence between these parameters and patient-related data in a set of 211 osteoarthritic (OA) patients undergoing total joint replacement. For each patient the data available were joint type, age and gender. Knee samples chosen randomly among all biopsies were graded according to ICRS score. Patients' age ranged between 30 and 90 years with a mean age of 66 ± 9.7 years. Patients were divided into age classes and statistically significant differences in proliferation rate at passage 1 were found between chondrocytes derived from young and old donors, with the last ones characterized by a lower proliferation rate. A similar trend was observed for proliferation rate at passage 2. For all the samples, cellular yields ranged between 0.1 and 5.5 million cells/g of tissue. No significant correlation was observed between the level of cartilage degeneration (ICRS score) and cellular yield and proliferation rates. However, in samples with a high degree of cartilage degeneration (ICRS score 4) the cellular yield was lower compared to the other three groups (ICRS scores 1-3). In this study we performed a systematic characterization of basic parameters of chondrocytes originating from a wide group of OA patients. Considering the use of autologous chondrocytes in chondral treatments, the characterization of cell basic features may represent an important step to determine the quality of the cell source which is a major determinant in the outcome of cell-based therapies.
JABB, 2011
Regenerative medicine is a critical frontier in biomedical and clinical research. The major progr... more Regenerative medicine is a critical frontier in biomedical and clinical research. The major progresses in the last few years were driven by a strong clinical need which could benefit from regenerative medicine outcomes for the treatment of a large number of conditions including birth defects, degenerative and neoplastic diseases, and traumatic injuries. Regenerative medicine applies the principles of engineering and life sciences to enhance the comprehension of the fundamental biological mechanisms underlying the structure-function relationships in physiologic and pathologic tissues and to accomplish alternative strategies for developing in vitro biological substitutes which are able to restore, maintain, or improve tissue, and organ function. This paper reviews selected approaches currently being investigated at Politecnico di Milano in the field of regenerative medicine. Specific tissue-oriented topics are divided in three sections according to each developmental stage: in vitro study, pre-clinical study, and clinical application. In vitro studies investigate the basic phenomena related to gene delivery, stem cell behavior, tissue regeneration, and to explore dynamic culture potentiality in different applications: cardiac and skeletal muscle, cartilage, hematopoietic system, peripheral nerve, and gene delivery. Specific fields of regenerative medicine, i.e., bone, blood vessels, and ligaments engineering have already reached the preclinical stage providing promising insights for further research towards clinical applications. The translation of the results obtained during in vitro and preclinical steps into clinical organ replacement is a very challenging issue, which can offer a valid alternative to fight morbidity, organ shortage, and ethical-social problems associated with allotransplantation as shown in the clinical case reported in this review.
Techniques in Orthopaedics, 2007
ABSTRACT Conventional plate techniques have been widely used in the treatment of humeral fracture... more ABSTRACT Conventional plate techniques have been widely used in the treatment of humeral fractures. The controversial clinical outcome is believed to be related to the reduced blood supply and to the presence of osteoporotic bone substance. In fact, the compressive force under the plate prevents periosteal perfusion resulting in periosteum and bone necrosis deep to the plate and adjacent to the fracture site, localized bone resorption at the screw threads, and loosening of the implant. Furthermore, in the presence of osteoporotic bone, it may become impossible to develop sufficient screw torque to generate sufficient screw force to prevent micromotion. In light of the encouraging results achieved in the management of metaphyseal fractures of the tibia and femur, locking plates have recently been introduced for the treatment of humeral fractures. These systems allow the screws to rigidly lock into the plate hole. Locking plate systems decrease gap strain by minimizing motion whereas tolerating an increased gap length. Strain at the fracture site is optimized so that secondary bone healing with callus formation is favored over fibrosus nonunion or primary bone healing. As internal fixators, locking plates no longer rely on frictional force between the plate and bone thus allowing the local blood supply. Promising initial clinical results have been reported. Regarding proximal humerus, biomechanical tests have shown better fatigue resistance and stiffness of locked plates as compared with conventional ones. Interestingly, in the case of distal humerus, comparative tests have shown that the biomechanical behavior depends more on plate configuration than plate type. Anyway, further clinical and biomechanical investigations are needed to understand the indications for locked plating as opposed to conventional plating in the treatment of humeral fracture.
European Spine Journal, 2002
The authors report their experience with the treatment of lumbar instability by a kind of spine s... more The authors report their experience with the treatment of lumbar instability by a kind of spine stabilization. The elastic stabilization, which follows a new philosophy, is obtained by an interspinous device, and should be used alone in degenerative disc disease, recurrent disc herniation and in very low grade instability, or in association with rigid fusion for the prevention of pathology
Medical Engineering & Physics, 2008
This study presents a finite element model of the C4-C7 segment in healthy conditions and after i... more This study presents a finite element model of the C4-C7 segment in healthy conditions and after implantation of a disc prosthesis at a single level, in order to investigate of the influence of disc arthroplasty on the biomechanics of the cervical spine. A nonlinear finite element model of the C4-C7 segment in intact conditions was developed and run in flexion and extension. A detailed model of the Bryan disc prosthesis, including contacts between the different components of the device, was built and positioned at C5-C6. The calculated segmental motion resulted preserved after disc arthroplasty, with respect to the model of the intact spine, in both flexion and extension. A general preservation of the forces transmitted through the facet joints was obtained; a minor force increase at the implanted level was detected. The analysis of the instantaneous centers of rotation (ICR) in flexion-extension showed the preservation of a physiological kinematics. The mechanical behaviour showed an asymmetry between flexion and extension, probably due to the removal of the anterior longitudinal ligament and the anterior part of the annulus fibrosus, and the preservation of the posterior structures. In general, the disc prosthesis showed to be able to reproduce a nearly physiological motion. However, other important mechanical aspects, such as the possible micromotion at the bone-implant interface and the possible degenerative conditions of the spine, need to be evaluated before drawing a conclusion about total disc arthroplasty from an engineering point of view.
Medical Engineering & Physics, 1998
This paper presents a parametric mathematical model of the head-cup wear coupling in total hip ar... more This paper presents a parametric mathematical model of the head-cup wear coupling in total hip arthroplasty (THA). The model evaluates the dependence of acetabular volumetric wear upon the characteristic parameters of patient and hip prosthesis. Archard's law is assumed to calculate the wear coupling behaviour. The wear factor is taken from pin-on-disc wear tests as a function of materials and finishing of the articular joint. The forces acting on the hip joint are taken from experimental data found in the literature whilst the load distribution is calculated under the hypotheses of perfectly rigid ideal wear coupling. The sliding distance is obtained by combining the three elementary displacements -- due to rotations around the three axes -- at the generic bearing surface location. The simulations show that the polymeric wear volume per step cycle decreases ranging from fast walking speeds to low running speeds, it increases linearly with patient body weight and with femoral head diameter, it decreases slightly for positive variations of the socket inclination angle and it increases exponentially with femoral head roughness. The volumetric wear rate per year calculated for a standard reference patient is 5.8 mm3. The relevant iso-wear maps show a marginal pattern with the maximum located near the cup superior borderline. At the instant of peak load, the iso-stress maps show a paracentral pattern with the maximum superior to the cup polar point, and the iso-sliding distance maps show a marginal pattern with two maxima located near the cup's superior and inferior borderlines.
Magnetic Resonance in Medicine, 2008
Our hypothesis was that the enhanced MRI of cartilage (dGEMRIC) imaging protocol could be used in... more Our hypothesis was that the enhanced MRI of cartilage (dGEMRIC) imaging protocol could be used in patients to quantify the sulfated glycosaminoglycan (sGAG) in intervertebral discs (IVD). To test this hypothesis, 23 patients with degenerative disc pathology scheduled for surgery were studied by a specific dGEMRIC protocol: each patient underwent two MRI scans, before and 3.5 hr after Gd(DTPA)2-injection of a nonconventional dose of 40 mL. Then, T(1PRE-ENH) and T(1POST-ENH) parametric images of the disc were obtained, from which a new index DeltaT(1) of the molecular status of the IVD was computed (T(1PRE-ENH) - T(1POST-ENH)). A total of 31 tissue samples (one or two from each patient) obtained at herniectomy were collected and biochemically analyzed for sGAG content and used as the gold standard for comparison. DeltaT(1) values in correspondence to degenerated sectors were higher (158 +/- 36 ms) compared to normal sectors (80 +/- 13 ms). Linear regression analysis between MRI-derived and biochemistry-derived measurements resulted in a significant correlation (r = 0.73, P < 0.0001). The DeltaT(1) parametric images, calculated using the modified dGEMRIC technique, provided noninvasive quantitative information about sGAG content within discal tissue in vivo, which resulted in agreement with biochemical analysis. The application of this new MRI method could provide diagnostic information for standard treatment of lumbar discopathy and for innovative therapies of regenerative medicine.
Knee Surgery, Sports Traumatology, Arthroscopy, 2005
Journal of Magnetic Resonance Imaging, 2009
To evaluate the effects of reducing the number of segments in which the intervertebral disc (IVD)... more To evaluate the effects of reducing the number of segments in which the intervertebral disc (IVD) can be subdivided on the accuracy in estimating its sGAG content by computation of the parameter DeltaT1 from delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) protocol. Twenty-three herniectomy patients underwent dGEMRIC acquisitions for IVD. Thirty-one tissue samples were obtained at herniectomy from the same patients and biochemically analysed for their sGAG content. Eleven different division schemes (DS) were applied by processing dGEMRIC images, and DeltaT1 values of the segments related to the surgical sampling locations were computed and correlated to the corresponding biochemical data. For each DS, the linear regression and Pearson's coefficient were computed. Reducing the number of segments from 48 (4 annular rings and 12 angular sectors) to 12 (2 rings and 6 sectors), correlation with sGAG biochemical data did not decline (r > 0.7). A 12-segment DS provided the best compromise between preserving accuracy and reducing the number of segments.
Journal of Biomedical Materials Research, 2001
The increase of the femoral head roughness in artificial hip joints is strongly influenced by the... more The increase of the femoral head roughness in artificial hip joints is strongly influenced by the presence of abrasive particulate entrapped between the articulating surfaces. The aim of the present study is to evaluate the dependence of such damage on the geometry of the particles entrapped in the joint, with reference to the UHMWPE/chrome-cobalt coupling. Five chrome-cobalt femoral heads and their coupled UHMWPE acetabular cups, retrieved at revision surgery after a short period of in situ functioning, have been investigated for the occurrence of third-body damage. This was found on all the prosthetic heads, where the peak-to-valley height of the scratches, as derived from profilometry evaluations, ranged from 0.3-1.3 microm. The observed damage has been divided into four classes, related to the particle motion while being embedded into the polymer. Two kinds of particle morphology have been studied, spherical and prismatic, with size ranging from 5-50 microm. In order to provide an estimation of the damage induced by such particles, a finite element model of the third-body interaction was set up. The peak-to-valley height of the impression due to the particle indentation on the chrome-cobalt surface is assumed as an index of the induced damage. The calculated values range from 0.1-0.5 microm for spherical particles of size ranging from 10-40 microm. In the case of prismatic particles, the peak-to-valley height can reach 1.3 microm and depends both on the size and width of the particle's free corner, indenting the chrome-cobalt. As an example, a sharp-edged particle of size 30 microm can induce on the chrome-cobalt an impression with peak-to-valley height of 0.75 microm, when embedded into the polyethylene with a free edge of 5 microm facing the metallic surface. Negligible damage is induced, if a free edge of 7.5 microm is indenting the counterface. Our findings offer new support to the hypothesis that microscopic third-body particles are capable of causing increased roughening of the femoral head and provide a quantitative evaluation of the phenomenon.
Journal of Biomechanics, 2006
Bioreactors allowing culture medium perfusion overcome diffusion limitations associated with stat... more Bioreactors allowing culture medium perfusion overcome diffusion limitations associated with static culturing and provide flow-mediated mechanical stimuli. The hydrodynamic stress imposed to cells will depend not only on the culture medium flow rate, but also on the scaffold three-dimensional (3D) micro-architecture. We developed a CFD model of the flow of culture medium through a 3D scaffold of homogeneous geometry, with the aim of predicting the shear stress acting on cells as a function of parameters that can be controlled during the scaffold fabrication process, such as the scaffold porosity and the pore size, and during the cell culture, such as the medium flow rate and the diameter of the perfused scaffold section. We built three groups of models corresponding to three pore sizes: 50, 100 and 150 microm. Each group was made of four models corresponding to 59%, 65%, 77%, and 89% porosity. A commercial finite-element code was used to set up and solve the problem and to analyze the results. The mode value of shear stress varied between 2 and 5 mPa, and was obtained for a circular scaffold of 15.5 mm diameter, perfused by a flow rate of 0.5 ml/min. The simulations showed that the pore size is a variable strongly influencing the predicted shear stress level, whereas the porosity is a variable strongly affecting the statistical distribution of the shear stresses, but not their magnitude. Our results provide a basis for the completion of more exhaustive quantitative studies to further assess the relationship between perfusion, at known micro-fluid dynamic conditions, and tissue growth in vitro.
European Spine Journal, 2009
The dynamic stabilization of lumbar spine is a non-fusion stabilization system that unloads the d... more The dynamic stabilization of lumbar spine is a non-fusion stabilization system that unloads the disc without the complete loss of motion at the treated motion segment. Clinical outcomes are promising but still not definitive, and the long-term effect on instrumented and adjacent levels is still a matter of discussion. Several experiments have been devised in order to gain a better understanding of the effect of the device on the intervertebral disc. One of the hypotheses was that while instrumented levels are partially relieved from loading, adjacent levels suffer from the increased stress. But this has not been proved yet. The aim of this study was to investigate the long-term effect of dynamic stabilization in vivo, through the quantification of glycosaminoglycans (GAG) concentration within instrumented and adjacent levels by means of the delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) protocol. Ten patients with low back pain, unresponsive to conservative treatment and scheduled for Dynesys implantation at one to three lumbar spine levels, underwent the dGEMRIC protocol to quantify GAG concentration before and 6 months after surgery. Each patient was also evaluated with visual analog scale (VAS), Oswestry, Prolo, Modic and Pfirrmann scales, both at pre-surgery and at follow-up. Six months after implantation, VAS, Prolo and Oswestry scales had improved in all patients. Pfirrmann scale could not detect any change, while dGEMRIC data already showed a general improvement in the instrumented levels: GAG was increased in 61% of the instrumented levels, while 68% of the non-instrumented levels showed a decrease in GAG, mainly in the posterior disc portion. In particular, seriously GAG-depleted discs seemed to have the greatest benefit from the Dynesys implantation, whereas less degenerated discs underwent a GAG depletion. dGEMRIC was able to visualize changes in both instrumented and non-instrumented levels. Our results suggest that the dynamic stabilization of lumbar spine is able to stop and partially reverse the disc degeneration, especially in seriously degenerated discs, while incrementing the stress on the adjacent levels, where it induces a matrix suffering and an early degeneration.
European Spine Journal, 2008
The implantation of lumbar disc prostheses based on different design concepts is widely accepted.... more The implantation of lumbar disc prostheses based on different design concepts is widely accepted. This paper reviews currently available literature studies on the biomechanics of TDA in the lumbar spine, and is targeted at the evaluation of possible relationships between the aims of TDA and the geometrical, mechanical and material properties of the various available disc prostheses. Both theoretical and experimental studies were analyzed, by a PUBMED search
Biomechanics and Modeling in Mechanobiology, 2002
Natural cartilage remodels both in vivo and in vitro in response to mechanical forces and hence m... more Natural cartilage remodels both in vivo and in vitro in response to mechanical forces and hence mechanical stimulation is believed to have a potential as a tool to modulate extra-cellular matrix synthesis in tissue-engineered cartilage. Fluid-induced shear is known to enhance chondrogenesis on animal cells. A well-defined hydrodynamic environment is required to study the biochemical response to shear of three-dimensional engineered cell systems. We have developed a perfused-column bioreactor in which the culture medium flows through chondrocyte-seeded porous scaffolds, together with a computational fluid-dynamic model of the flow through the constructs' microstructure. A preliminary experiment of human chondrocyte growth under static versus dynamic conditions is described. The median shear stress imposed on the cells in the bioreactor culture, as predicted by the CFD model, is 3 x 10(-3) Pa (0.03 dyn/cm(2)) at a flow rate of 0.5 ml/min corresponding to an inlet fluid velocity of 44.2 mum/s. Providing a fluid-dynamic environment to the cells yielded significant differences in cell morphology and in construct structure.
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Papers by Manuela T Raimondi