Browsing by Author "Kasyanov, Vladimir"
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Item Biomechanical properties of human dilated ascending aorta(2019-05-01) Brečs, Ivars; Stradiņš, Peteris; Kalejs, Martiņš; Strazdiņš, Uldis; Ozolanta, Iveta; Kasyanov, Vladimir; Rīga Stradiņš University; Biomehānikas zinātniskā laboratorijaAneurysms of ascending aorta are dilatation of the first part of the human aorta. They commonly show no clinical symptoms. This condition increases the risk of aorta dissection, which is a life-threatening condition. In this study we attempted to elucidate the changes in the biomechanical properties that occur in the dilated human ascending aorta. Fourteen specimens of ascending aorta wall were mechanically tested under a uniaxial tensile test. Two specimens from each ascending aorta anterior region were cut in longitudinal and circumferential directions. The samples were stretched until rupture of the sample occurred. The obtained experimental data were processed to determine maximal stress, maximal strain and the tangential modulus of elasticity in the linear part of the stress-strain curve. The obtained results showed a remarkable anisotropy of the ascending aorta tissue. We found higher strength of the tissue in the circumferential direction than in the longitudinal direction. There were no statistically significant differences between the strains of the samples. Tangential modulus of elasticity of the aortic samples in the longitudinal direction was significantly lower than the elastic modulus of the samples in the circumferential direction. The tissue in the circumferential direction is stronger and stiffer than in the longitudinal direction.Item Calcium Phosphate Bioceramic Material Local Influence on the Bone Biomechanical Properties at Rabbits with Experimental Osteoporosis(2018) Ananjevs, Vladislavs; Ananjeva, Aleksandra; Vētra, Jānis; Skagers, Andrejs; Salma, Ilze; Ločs, Jānis; Kasyanov, Vladimir; Department of Oral and Maxillofacial Surgery and Oral Medicine; Institute of Anatomy and Anthropology; Biomehānikas zinātniskā laboratorijaBiomechanical characteristicsof the rabbit cartilagecomponentfrom the femurwereinvestigated.The controlosteoporosishad beenactivatedby ovariectomy alongside theinjections of methylprednisolone. During the experiment defects in the femur’sgreater trochanter zonewas created andafterwardsfilled withthefragmentsof a hydroxyapatite as well astricalcium phosphate(HAP/TCP 70/30) or HAP/TCP 70/30mixedwith five percentstrontium. Threemonths lateranimals were euthanazed, squared samples werecut out from the femur’sbody andlatertested on a bend. The results ofthe research revealedthat the femurs becomemorestringentafter filling offdefects in the greater trochanter zonewith HAP/TCP 70/30or HAP/TCP 70/30mixed with fivepercentstrontium. The ultimate painfor the cartilagecomponentin the controlgroupswas less, than in thetest group.The flexure modulus of flexibilityof a cartilagecomponentin the test groupwas statistically reliable less, than the value of the flexure modulus of flexibilityof the cartilagecomponentin the controlgroups. Therefore, local usage ofcalcium –phosphatic bioceramic componentoverthe greater trochanter partincreasesbiomechanical characteristicsof the cartilagecomponentin the femurof animals.Item Commercial articulated collaborative in situ 3D bioprinter for skin wound healing(2023-01-31) Levin, Aleksandr A; Karalkin, Pavel A.; Koudan, Elizaveta V.; Senatov, Fedor S.; Parfenov, Vladislav A.; Lvov, Vladislav; Petrov, Stanislav; Pereira, Frederiko D.A.S.; Kovalev, Alexey V.; Osidak, Egor; Domogatsky, Sergey P.; Manturova, Natalya E.; Kasyanov, Vladimir; Sergeeva, Natalia S.; Zorin, Vadim L.; Khesuani, Yusef D.; Mironov, Vladimir A.; Joint Laboratory of Traumatology and OrthopaedicsIn situ bioprinting is one of the most clinically relevant techniques in the emerging bioprinting technology because it could be performed directly on the human body in the operating room and it does not require bioreactors for post-printing tissue maturation. However, commercial in situ bioprinters are still not available on the market. In this study, we demonstrated the benefit of the originally developed first commercial articulated collaborative in situ bioprinter for the treatment of full-thickness wounds in rat and porcine models. We used an articulated and collaborative robotic arm from company KUKA and developed original printhead and correspondence software enabling in situ bioprinting on curve and moving surfaces. The results of in vitro and in vivo experiments show that in situ bioprinting of bioink induces a strong hydrogel adhesion and enables printing on curved surfaces of wet tissues with a high level of fidelity. The in situ bioprinter was convenient to use in the operating room. Additional in vitro experiments (in vitro collagen contraction assay and in vitro 3D angiogenesis assay) and histological analyses demonstrated that in situ bioprinting improves the quality of wound healing in rat and porcine skin wounds.Item Comparison of biomechanical and structural properties between human aortic and pulmonary valve(2004-09) Stradins, Peteris; Lacis, Romans; Ozolanta, Iveta; Purina, Biruta; Ose, Velta; Feldmane, Laila; Kasyanov, Vladimir; Department of Surgery; Biomehānikas zinātniskā laboratorijaObjective: Pulmonary valve autografts have been reported as clinically effective for replacement of diseased aortic valve (Ross procedure). Published data about pulmonary valve mechanical and structural suitability as a long-term substitute for aortic valve are limited. The aim of this study was to compare aortic and pulmonary valve properties. Methods: Experimental studies of biomechanical properties and structure of aortic and pulmonary valves were carried out on pathologically unchanged human heart valves, collected from 11 cadaveric hearts. Biomechanical properties of 84 specimens (all valve elements: cusps, fibrous ring, commissures, sinotubular junction, sinuses) were investigated using uniaxial tensile tests. Ultrastructure was studied using transmission and scanning electron microscopy. Results: Ultimate stress in circumferential direction for pulmonary valve cusps is higher than for aortic valve (2.78±1.05 and 1.74±0.29 MPa, respectively). Ultimate stress in radial direction for pulmonary and aortic cusps is practically the same (0.29±0.06 and 0.32±0.04 MPa, respectively). In ultrastructural study, different layout and density in each construction element are determined. The aortic and pulmonary valves have common ultrastructural properties. Conclusions: Mechanical differences between aortic and pulmonary valve are minimal. Ultrastructural studies show that the aortic and pulmonary valves have similar structural elements and architecture. This investigation suggests that the pulmonary valve can be considered mechanically and structurally suitable for use as an aortic valve replacement.Item From Biomechanical Properties to Morphological Variations : Exploring the Interplay between Aortic Valve Cuspidity and Ascending Aortic Aneurysm(2024-07-19) Brečs, Ivars; Skuja, Sandra; Kasyanov, Vladimir; Groma, Valērija; Kalējs, Mārtiņš; Svirskis, Šimons; Ozolanta, Iveta; Stradiņš, Pēteris; Joint Laboratory of Electron Microscopy; Joint Laboratory of Traumatology and Orthopaedics; Faculty of Medicine; Institute of Microbiology and VirologyBackground: This research explores the biomechanical and structural characteristics of ascending thoracic aortic aneurysms (ATAAs), focusing on the differences between bicuspid aortic valve aneurysms (BAV-As) and tricuspid aortic valve aneurysms (TAV-As) with non-dilated aortas to identify specific traits of ATAAs. Methods: Clinical characteristics, laboratory indices, and imaging data from 26 adult patients operated on for aneurysms (BAV-A: n = 12; TAV-A: n = 14) and 13 controls were analyzed. Biomechanical parameters (maximal aortic diameter, strain, and stress) and structural analyses (collagen fiber organization, density, fragmentation, adipocyte deposits, and immune cell infiltration) were assessed. Results: Significant differences in biomechanical parameters were observed. Median maximal strain was 40.0% (control), 63.4% (BAV-A), and 45.3% (TAV-A); median maximal stress was 0.59 MPa (control), 0.78 MPa (BAV-A), and 0.48 MPa (TAV-A). BAV-A showed higher tangential modulus and smaller diameter, with substantial collagen fragmentation ( p < 0.001 vs. TAV and controls). TAV-A exhibited increased collagen density ( p = 0.025), thickening between media and adventitia layers, and disorganized fibers ( p = 0.036). BAV-A patients had elevated adipocyte deposits and immune cell infiltration. Conclusions: This study highlights distinct pathological profiles associated with different valve anatomies. BAV-A is characterized by smaller diameters, higher biomechanical stress, and significant collagen deterioration, underscoring the necessity for tailored clinical strategies for effective management of thoracic aortic aneurysm.Item The fusion of tissue spheroids attached to pre-stretched electrospun polyurethane scaffolds(2014-01-17) Beachley, Vince; Kasyanov, Vladimir; Nagy-Mehesz, Agnes; Norris, Russell; Ozolanta, Iveta; Kalejs, Martins; Stradins, Peteris; Baptista, Leandra; da Silva, Karina; Grainjero, Jose; Wen, Xuejun; Mironov, Vladimir; Biomehānikas zinātniskā laboratorijaEffective cell invasion into thick electrospun biomimetic scaffolds is an unsolved problem. One possible strategy to biofabricate tissue constructs of desirable thickness and material properties without the need for cell invasion is to use thin (<2 µm) porous electrospun meshes and self-assembling (capable of tissue fusion) tissue spheroids as building blocks. Pre-stretched electrospun meshes remained taut in cell culture and were able to support tissue spheroids with minimal deformation. We hypothesize that elastic electrospun scaffolds could be used as temporal support templates for rapid self-assembly of cell spheroids into higher order tissue structures, such as engineered vascular tissue. The aim of this study was to investigate how the attachment of tissue spheroids to pre-stretched polyurethane scaffolds may interfere with the tissue fusion process. Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs. Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number. In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes. Our data demonstrate that tissue spheroids attached to thin stretched elastic electrospun scaffolds have an interrupted tissue fusion process. The resulting tissue-engineered construct phenotype is a direct outcome of the delicate balance of the competing physical forces operating during the tissue fusion process at the interface of the pre-stretched elastic scaffold and the attached tissue spheroids. We have shown that with appropriate treatments, this process can be modulated, and thus, a thin pre-stretched elastic polyurethane electrospun scaffold could serve as a supporting template for rapid biofabrication of thick tissue-engineered constructs without the need for cell invasion.Item General influence of biphasic calcium phosphate on osteoporotic bone density(2019-05-01) Ananjevs, Vladislavs; Ananjeva, Aleksandra; Vetra, Janis; Skagers, Andrejs; Salma, Ilze; Neimane, Laura; Kasyanov, Vladimir; Department of Oral and Maxillofacial Surgery and Oral Medicine; Institute of Anatomy and Anthropology; Biomehānikas zinātniskā laboratorijaBone density of the femur body of rabbit was determined in vivo. Experimental osteoporosis was induced by ovariectomy and subsequent injections of methylprednisolone. In the greater trochanter region of right femur, defects were created and filled with granules of hydroxyapatite and tricalcium phosphate (HAP/TCP 70/30) or HAP/TCP 70/30 together with 5% strontium. After three months, the animals were euthanized. The bone mass density of the right and left body of femur was measured by cone beam computed tomography (CT) scan. The results of the study showed that the right femur of the rabbit, where biomaterials had been implanted, and the left femur, where no biomaterial implantation occurred, became denser after filling the defect with HAP/TCP 70/30 ceramic granules or 5% Sr modified HAP/TCP ceramic granules. There was no difference between operated and non-operated legs and HAP/TCP and HAP/TCP with 5% strontium groups.Item Nanotechnological strategies for biofabrication of human organs(2012) Rezende, Rodrigo A.; Azevedo, Fábio De Souza; Pereira, Frederico David; Kasyanov, Vladimir; Wen, Xuejun; De Silva, Jorge Vicente Lopes; Mironov, Vladimir; Institute of Anatomy and AnthropologyNanotechnology is a rapidly emerging technology dealing with so-called nanomaterials which at least in one dimension have size smaller than 100nm. One of the most potentially promising applications of nanotechnology is in the area of tissue engineering, including biofabrication of 3D human tissues and organs. This paper focused on demonstrating how nanomaterials with nanolevel size can contribute to development of 3D human tissues and organs which have macrolevel organization. Specific nanomaterials such as nanofibers and nanoparticles are discussed in the context of their application for biofabricating 3D human tissues and organs. Several examples of novel tissue and organ biofabrication technologies based on using novel nanomaterials are presented and their recent limitations are analyzed. A robotic device for fabrication of compliant composite electrospun vascular graft is described. The concept of self-assembling magnetic tissue spheroids as an intermediate structure between nano- and macrolevel organization and building blocks for biofabrication of complex 3D human tissues and organs is introduced. The design of in vivo robotic bioprinter based on this concept and magnetic levitation of tissue spheroids labeled with magnetic nanoparticles is presented. The challenges and future prospects of applying nanomaterials and nanotechnological strategies in organ biofabrication are outlined.Item Organ printing as an information technology(2015) Rezende, Rodrigo A.; Kasyanov, Vladimir; Mironov, Vladimir; Da Silva, Jorge Vicente Lopes; Rīga Stradiņš UniversityOrgan printing is defined as a layer by layer additive robotic computer-aided biofabrication of functional 3D organ constructs with using self-assembling tissue spheroids according to digital model. Information technology and computer-aided design softwares are instrumental in the transformation of virtual 3D bioimaging information about human tissue and organs into living biological reality during 3D bioprinting. Information technology enables design blueprints for bioprinting of human organs as well as predictive computer simulation both printing and post-printing processes. 3D bioprinting is now considered as an emerging information technology and the effective application of existing information technology tools and development of new technological platforms such as human tissue and organ informatics, design automation, virtual human organs, virtual organ biofabrication line, mathematical modeling and predictive computer simulations of bioprinted tissue fusion and maturation is an important technological imperative for advancing organ bioprinting.Item Periostin regulates collagen fibrillogenesis and the biomechanical properties of connective tissues(2007-06-01) Morris, Russell A.; Damon, Brook; Mironov, Vladimir; Kasyanov, Vladimir; Ramamurthi, Anand; Moreno-Rodriguez, Ricardo; Trusk, Thomas; Potts, Jay D.; Goodwin, Richard L.; Davis, Jeff; Hoffman, Stanley; Wen, Xuejun; Sugi, Yukiko; Kern, Christine B.; Mjaatvedt, Corey H.; Turner, Debi K.; Oka, Toru; Conway, Simon J.; Molkentin, Jeffery D.; Forgacs, Gabor; Markwald, Roger R.; Rīga Stradiņš UniversityPeriostin is predominantly expressed in collagen-rich fibrous connective tissues that are subjected to constant mechanical stresses including: heart valves, tendons, perichondrium, cornea, and the periodontal ligament (PDL). Based on these data we hypothesize that periostin can regulate collagen I fibrillogenesis and thereby affect the biomechanical properties of connective tissues. Immunoprecipitation and immunogold transmission electron microscopy experiments demonstrate that periostin is capable of directly interacting with collagen I. To analyze the potential role of periostin in collagen I fibrillogenesis, gene targeted mice were generated. Transmission electron microscopy and morphometric analyses demonstrated reduced collagen fibril diameters in skin dermis of periostin knockout mice, an indication of aberrant collagen I fibrillogenesis. In addition, differential scanning calorimetry (DSC) demonstrated a lower collagen denaturing temperature in periostin knockout mice, reflecting a reduced level of collagen cross-linking. Functional biomechanical properties of periostin null skin specimens and atrioventricular (AV) valve explant experiments provided direct evidence of the role that periostin plays in regulating the viscoelastic properties of connective tissues. Collectively, these data demonstrate for the first time that periostin can regulate collagen I fibrillogenesis and thereby serves as an important mediator of the biomechanical properties of fibrous connective tissues.