Revista de ciencia e ingeniería de tejidos

Tissue engineering is rapidly progressing to provide complex, three-dimensional (3D) representations of human tissues that can be used for tissue replacement and/or to study tissue systems. Tissue engineering includes the addition of cells within 3D scaffolds, along with bioactive components, sometimes within a bioreactor. A major challenge in developing many tissue-engineered models is the ability to evenly distribute cells throughout a porous scaffold, in order to achieve good cell viability and growth. In this study, we created a 3D collagen-chitosan scaffold with specific properties to aid in seeding cells within the entire volume and investigated a dynamic method to seed cells within such scaffold. Based on the requirements for cell seeding, the scaffolds were less than 500 µm thick, had pore sizes greater than 50 µm and had a porosity of 50% or greater. Fibroblasts were used as model cells for this seeding method. To seed fibroblasts within the scaffold, we varied two design parameters: concentration of the collagen seeding solution and the centrifugal force used for cell seeding. We ranked the seeding efficiency, cell proliferation and distribution in order to choose the ideal cell seeding method. Results showed that seeding with a higher concentration (2 mg/ml) of collagen seeding solution and a lower centrifugation speed (259 ×g) was the optimal seeding method, resulting in 84% increase in cell proliferation and a more uniform cell distribution throughout the scaffold. Results from this study can be applied for seeding a variety of cell populations within porous scaffolds for tissue engineering applications.

Circumferential tears of the Annulus Fibrosus (AF) are frequently observed pathological features of degenerate lumbar discs and have been associated with vascular propagation and the generation of low back pain. In order to evaluate the potential of novel biological agents to repair annular defects and arrest disc degeneration we required an animal model that would permit injection of cells or their cryoprotectant into adjacent lumbar discs of the same animal. Three lumbar discs (L2/3, L3/4 and L4/5) of 6 sheep were subjected to a peripheral lateral annular surgical incision. The adjacent uninjured lumbar L1/2 and L5/6 discs served as uninjured controls. After three months the spines were radiographed and disc height indices (DHI) calculated and Pfirrmann disc degeneration scores determined from MRI spinal images. Isolated lumbar discs were analysed morphologically, histologically and biochemically using published procedures. Disc height index measurements of injured discs revealed an average decrease of 23.67% relative to baseline values (p<0.0001). The corresponding MRI Pfirrmann degeneration scores were significantly higher than non-injured control discs (p<0.05), as were their morphology scores (p<0.005). The sulphated - glycosaminoglycan content, of the Nucleus Pulposus (NP) and injured side of the AF of lumbar discs, were significantly lower than control discs (p<0.05 and p<0.0005) respectively. Conversely, the DNA levels of the injured side of the AF were higher than the uninjured side (p<0.05). The histological scores showed higher degenerative changes in injured than in control discs (p<0.005). For all parameters monitored in this study no statistical differences were observed between the three injured lumbar discs confirming their uniform response to injury. This study therefore confirmed the suitability of this large animal model for evaluating the potential of biologicals to reconstitute degenerate ovine lumbar discs relative to their carriers/cryoprotectant.

Polyvinyl Alcohol (PVA) and Hydroxy Ethyl Cellulose (HEC) were used to prepare hydrogel for tissue regeneration. Female rabbits were used to evaluate the obtained hydrogels for the regeneration of adipose tissue. Mechanical and biocompatible properties were evaluated. AFM (Atomic Force Microcopy) and SEM (Scanning Electron Microscopy) showed the roughness around 5.447 nm and pore size from 1 to 7.9 μm. In vivo tests were conducted during two years in female rabbits. Histological images showed stable fat formation over long-term without adverse reaction or necrosis. The obtained results indicated that PHEC30 hydrogel may provide a viable approach for the regeneration of adipose tissue in female rabbits as first step as an alternative solution for women who suffered a radical mastectomy.

This study proposes a production method capable of producing vascular grafts from fully synthetic, resorbable polymers that both meet basic minimum mechanical requirements for potential vascular grafts, and have a compliance similar to that of the intended vasculature being replaced. All of the electrospun vascular grafts in this work meet the minimum mechanical requirements for compliance, burst pressure, and suture retention strength, and could be potential candidates for off-the-shelf tissue engineered vascular grafts. Each polymer investigated in this paper has FDA approval for medical use and has been shown to be successful in various tissue engineering applications. Only recently has an electrospun small-diameter graft been fabricated with compliance and burst pressure greater than that of the human saphenous vein. We show a significant advancement in burst pressure, compliance, and suture retention strength in the novel electrospun grafts presented in this work which demonstrates the potential use of these tissue engineered vascular grafts for coronary artery bypass graft and other smalldiameter graft indications.

The human skin is a complex organ consisting of multiple skin cells that work together to complement each other and provide essential functions such as skin barrier function, skin homeostasis and protection against the harmful ultraviolet radiation. Understanding the roles and paracrine signaling of different skin cells plus the influence of external stimuli on them are crucial towards the design of tissue-engineered skin constructs as these factors regulate the cellular behavior such as cell proliferation, migration and differentiation. Hence, an in-depth understanding of the knowledge on the epithelial-mesenchymal interactions would be valuable towards the design of a tissue-engineered skin construct.

Introduction: Perioral tissue loss commonly requires surgical reconstruction. Autologous tissue transfer result in poor functional and aesthetic outcomes and allogenous transplantation of tissue requires lifelong immunosuppression. There is a clinical need for a cell scaffold, which could be seeded with the patients own cells to create an immunogenically inert perioral tissue replacement. Decellularized human lip may provide the answer.
Methodology: To the authors knowledge this was the first time human lip has been decellularized. Four existing protocols shown to be successful at removing cells from either muscle or dermis were used to decellularize human lip in an attempt to identify an optimal protocol.
Results: Three of the four protocols proved to be successful at achieving decellularization of the lip, as histological investigation of these samples showed complete loss of cellular structures for the entire construct. A non-detergent based protocol using osmotic shock and enzymatic processes best preserved the extracellular matrix. It was able to maintain the micro-architecture of collagen and elastin, and retain important signaling molecules such as glycosaminoglycans.
Conclusion: This decellularized scaffold developed here may be the first step towards an exciting new treatment for perioral tissue loss.

Functional cartilage tissue engineering aims at augmenting the regeneration process of chondrocyte seeded three dimensional scaffolds by application of external biomechanical stimuli. The effect of static compressive stimuli in modulating the phenotype of chondrocytes cultured in porous scaffolds using a bioreactor is being investigated in the present study. Chondrocytes were seeded in porous Poly (vinyl) alcohol-Poly capro lactone scaffold and was subjected to static unconfined compressive strain of 10% for 1h everyday for a period of 7days using a bioreactor. After culture period, chondrogenic phenotype of seeded cells was assessed by live dead assay, biochemical histological and real time PCR analysis. Bioreactor seems to be a promising tool in delivering the desired biomechanical stimuli to the cell seeded constructs. However, application of biomechanical stimuli in the form of static compression doesn’t seem beneficial as it modulates chondrogenic phenotype by reverting to a fibroblastic morphology with the secretion of collagen type 1 extra cellular matrix molecules