Papers by Keyword: Collagen Scaffold

Abstract: This study aims to present the preliminary studies related to the evaluation of the in vivo biocompatibility using the rat model of bioresorbable composite materials type collagen-tricalciumphophate and colagen-tricalcium phosphate-magnesium for potentially medical application in trauma surgery. These biomaterials could be used as short-term structural support for bone tissue defects and can be reabsorbed into the body after healing are being sought. For in-vivo evaluation of bioresorbable materials on 2 groups of twenty Wistar and brown Norway rats for a period of 18 months. We simulated tissue defects in different anatomical areas of the animals and these two types of biomaterials were implanted. The animals were evaluated periodically with clinical exams, laboratory tests (blood tests, histopatological tests, radiological control) and anatomical dissection for macroscopic examination of the tissues. After different times (3, 6 and18 months) of implantation we sacrificed the animals. We observed the resorbtion rate of the biomaterials into the tissues in conjunction with tissue regeneration. We also note the inflammatory response and foreign body reactions into the adjacent tissue, using histopathological examinations. Due to the reaction of the materials in contact with the bone narrow a layer of magnesium calcium phosphate was formed which contributes to the local tissue healing. Our preliminary investigation results on these materials demonstrate that all the implanted materials were absorbed in vivo without any pathological changes in the rat body. Other future researches will be made in order to validate these biomaterials as orthopedic biomaterials useful in bone defects regeneration.

Abstract: Antibiotic delivery systems used in the past have consisted primarily of impregnated cement beads that required routine removal once the antibiotic had eluded completely. With the development of collagen scaffolds that could be used to fill bony defects the antibiotic cold be delivered from the scaffold used to sustain local bone growth. Over the course of two years antibiotic loaded collagen scaffolds were used in the local treatment of 21patients suffering of complicated fractures including bone defects, infections or pseudoarthrosis, all of them of traumatic nature. At the time of the initial surgical debridement or at subsequent second look procedures once local tissue viability was observed the antibiotic loaded collagen scaffold was inserted in the tissue defect and never removed. Excellent results were obtained and the infection was brought under control by use of both surgical and antibiotic modalities. Bone grafting was used in 6 cases where the defects were extensive. Where there was less extensive bone destruction the scaffold was a good adjuvant in new bone formation. Use of antibiotic loaded collagen scaffolds is a reliable and effective means of local antibiotic delivery system combining both the new bone formation capacity of the scaffold to hold osteoblasts with the ability to deliver high doses of antibiotic in the local tissue environment and thus avoiding the systemic toxicity.

Abstract: Collagen gels constitute an adequate scaffold for supporting the adhesion, proliferation and tissue regeneration of vascular cells inside a bioreactor. However, their mechanical properties should be enhanced not only for their manipulation but also to resist the mechanical constraints applied in the bioreactor. Actually, assessing the mechanical properties of a hydrogel requires many precautions since they are very sensitive to the environmental conditions (temperature, ionic strength, aqueous environment, etc). Whereas mechanical properties are usually measured directly in the air, the aim of this work was to evaluate the effects of a pseudo-physiological environment (PPE) on the mechanical properties of collagen gels. Furthermore, reinforcement was also tested using UV treatments (λ = 254 nm, 20 J/cm²), known to induce crosslinking. Irradiated samples were more resistant to enzymatic degradation and swelling tests showed that the crosslink density was increased by a factor of 30. This increase was thereafter correlated to the mechanical properties. Results showed that the UV-treated samples were stiffer and more brittle than the non-treated ones when tested in air. However, a 20% decrease and 40% increase were respectively measured on the linear modulus and strain at rupture when the gels were tested in the PPE. In the perspective of vascular tissue regeneration, these results show that the mechanical properties of a hydrogel should be performed in PPE in order to take into account the plasticization phenomenon that will occur in a bioreactor.

Abstract: Diseases occurring to blood vessel are preferentially solved by replacing the vessel by an autologous graft. When it is not available, a synthetic graft is used which has low patency rates for small diameter (<6 mm) vessels. Tissue engineering of blood vessel aims to improve the performance of vascular substitutes. Bioreactors are used in vascular tissue engineering to mimic the mechanical and biochemical environment of blood vessel. A 2D bioreactor was custom made in order to impose a dynamical strain to silicone membrane receiving the collagen cell-based construct. Collagen gels with vascular smooth muscle cells cultured inside were subdued to maturation under dynamical uniaxial stretch regimes at 1Hz for 48 hours. The percentage of deformation encountered by the silicone membrane was measured by ImageJ. Collagen fibrils and porcine smooth muscle cells (PSMC) orientations were assessed by scanning electron microscopy (SEM). Results show that the study of mechanical conditioning on cell activity is an important issue for enhancing the alignment of collagen fibrils.

Abstract: The purpose of this study is to confirm the possibility of regenerating actual fat tissue using human adipose tissue-derived stem cells (ASCs) and hyaluronic acid-collagen sponge in animal model. Human ASCs of young female adults were isolated and culture expanded in basal media. At the second passage, cultured ASCs suspension containing 106 cells was applied on prewetted scaffolds the hyaluronic acid-collagen sponge and the sponges was exposed to adipogenic media for the 1week. Then the tissue engineered constructs were implanted into the subcutaneous pocket on the back of immunodeficient athymic nude mice for 3 weeks. Hyaluronic acid-collagen sponges without human ASCs were used as the control. After 3 weeks, specimens were harvested and adipogenic potentials were assessed with histological examination, RT-PCR for PPAR-γ2 expression and G-3-PDH activity. Tissue engineered fat tissue from ASCs and hyaluronic acid-collagen sponges demonstrated PPAR-γ2 positive expression and positive Oil red O staining. The histologic study showed definitive adipose tissue and rich vascular tissue within the engineered fat. Two-fold higher activities of G-3-PDH were identified in experimental group after 3 weeks as compared to control. By contrast, the specimen from control group did not show active vessel ingrowth and contained only few cellular elements within the scaffold. The control specimens failed to demonstrate adipogenic gene markers and were negative in oil red O staining. In conclusion, human ASCs can be differentiated into adipocytes and actual fat tissue engineering was possible with combination of adequate scaffold materials, such as hyaluronic acid-collagen sponges. These data demonstrate that fat tissue engineered from human ASCs can retain predefined shape and dimension for soft tissue augmentation and reconstruction of defects.

Abstract: Human skin substitutes are needed for implantation and wound repair based on the new concept of tissue engineering in combination with biomaterials and cell biological technology. However, failure sometimes occurs when the wound healing is delayed in vivo due to acute inflammation resulting from the early degradation of the transplanted biomaterials. Accordingly, the current study modified conventional biomaterials to overcome early degradation and strong inflammation. In a conventional skin substitute, the animal origin collagenous materials have a slight antigenicity as xenogenic materials, however, the modified method was able to obtain a low antigenicity and anti-inflammation effect using atelo-collagen and an amniotic component. The tyrosine content in the developed atelo-collagen, representing the antigenicity, was reduced from 0.590% to 0.046% based on an HPLC analysis. In addition, to reduce the inflammation and foreign material reaction, an amniotic component was applied to the atelo-collagen materials. While, to enhance the wound healing, the modified skin substitute was developed as a composite matrix of an atelo-collagen scaffold with an amniotic membrane component. A quantitative analysis of hEGF in the amniotic membrane was also performed using different processing methods. Finally, a tissueengineered skin substitute was constructed by cultivating skin cells in the collagen scaffold attached to an amniotic membrane.