Difference between heartwood and sapwood
Forest Products Laboratory (U.S.)
1919
Search results
46 records were found.
Uma lesão do sistema nervoso acarreta normalmente consequências devastadoras. No
caso particular de lesões da medula espinal (LME), os pacientes têm que lidar com
múltiplas insuficiências biológicas. Por este motivo, é urgente desenvolver terapias que
possam resolver eficazmente este problema. Diferentes estratégias têm sido propostas
para tratar esta condição, tais como, terapias baseadas em transplantação celular e/ou
terapias moleculares. No entanto, os resultados não têm sido satisfatórios, reforçando a
ideia que são necessárias abordagens alternativas. A engenharia de tecidos tem sido
proposta como um novo método para enfrentar estes problemas. Esta estratégia implica
o uso de uma estrutura 3D que é capaz de suportar o crescimento e a diferenciação
celular de forma a criar um ambiente adequado para o desenvolvimento de um tecido
f...
Adipose-derived adult stem cells (ASCs), bone marrow mesenchymal stem cells (bmMSCs), and human umbilical cord perivascular cells (HUCPVCs) tissue have been widely tested for regenerative applications, such as bone regeneration. Moreover, olfactory ensheathing cells (OECs) show promise in promoting spinal cord injury (SCI) regeneration. Our group recently proposed the use of a hybrid scaffold targeting both vertebral bone repair and SCI regeneration. According to this concept, both MSCs and OECs should be in close contact to be influenced by the factors that are involved in secretion. For this reason, here we studied the effects of the OEC secretome on the metabolic activity and proliferation of ASCs, bmMSCs, and HUCPVCs. The stem cells' secretome effects on metabolic activity and proliferation of the OECs were also considered. In co-c...
Mesenchymal Stem Cells (MSCs), have been defined and characterized by: 1) their ability to adhere to plastic culture flasks; 2) the positive expression of CD105, CD73, CD90 membrane antigens, and the lack of expression of others (e.g CD45 and CD34) and 3) the ability of differentiation under adequate conditions along the osteogenic, chondrogenic and adipogenic lineages. In recent years, cells with these characteristics have been isolated from the Wharton’s jelly of the Umbilical Cord (UC). Similarly to bone marrow MSCs, they have shown multilineage differentiation potential and to be able to provide trophic support to neighboring cells. According to the literature, there are two main populations of cells with a mesenchymal character within the human UC: Wharton's jelly Mesenchymal Stem Cells (WJ-MSCs) and Human Umbilical Cord Perivascu...
Although several major progresses have been introduced in the field of bone regenerative medicine during the years, current therapies, such as bone grafts, still have many limitations. Moreover, and in spite of the fact that material science technology has resulted in clear improvements in the field of bone substitution medicine, no adequate bone substitute has been developed and hence large bone defects/injuries still represent a major challenge for orthopaedic and reconstructive surgeons. It is in this context that TE has been emerging as a valid approach to the current therapies for bone regeneration/substitution. In contrast to classic biomaterial approach, TE is based on the understanding of tissue formation and regeneration, and aims to induce new functional tissues, rather than just to implant new spare parts. The present review...
Starch-based biomaterials and scaffolds have been proposed for several biomedical applications. In the present work new scaffolds based on a 50/50 (wt%) blend of corn starch/ethylene-vinyl alcohol (SEVA-C) were studied. These scaffolds were processed by a melt-based technology, which has been used before with other starch-based materials but never with SEVA-C. Scanning electron microscopy (SEM) observation showed that the developed porous structures were 60% porous with pore size between 200 and 900 μm and a reasonable degree of interconnectivity. Moreover, scaffolds presented a compressive modulus of 117.50 ± 3.7 MPa and a compressive strength of 20.8 ± 2.4 MPa. Cytotoxicity evaluation was performed according to ISO/EN 10993 part 5 guidelines, and revealed that the developed scaffolds were nontoxic and did not inhibit cell growth. Dir...
One possible interesting way of designing a scaffold for bone tissue engineering is to base
it on trying to mimic the biophysical structure of natural extracellular matrix (ECM). This
work was developed in order to produce scaffolds for supporting bone cells. Nano and
micro fiber combined scaffolds were originally produced from starch based biomaterials by
means of a fiber bonding and a electrospinning, two step methodology. The cell culture
studies with SaOs-2 human osteoblast-like cell line and rat bone marrow stromal cells
demonstrated that presence of nanofibers influenced cell shape and cytoskeletal
organization of the cells on the nano/micro combined scaffolds. Moreover, cell viability and
Alkaline Phosphatase (ALP) activity for both cell types was found to be higher in nano/micro
combined scaffolds than in control scaffolds base...
The regenerative capacity of injured adult central nervous system (CNS) tissue is very limited. Specifically, traumatic spinal cord injury (SCI) leads to permanent loss of motor and sensory functions below the site of injury, as well as other detrimental complications. A potential regenerative strategy is stem cell transplantation; however, cell survival is typically less than 1%. To improve cell survival, stem cells can be delivered in a biomaterial matrix that provides an environment conducive to survival after transplantation. One major challenge in this approach is to define the biomaterial and cell strategies in vitro. To this end, we investigated both peptide-modification of gellan gum and olfactory ensheathing glia (OEG) on neural stem/progenitor cell (NSPC) fate. To enhance cell adhesion, the gellan gum (GG) was modified using ...
The molecular weight and crystallinity of systems based on poly(L-lactic acid) PLLA is
an important issue as it can influence, besides the general physical properties of the polymer, the
patterns of cell adhesion, proliferation and cell morphology. The objective of the present study was
to evaluate how crystallinity and molecular weight of PLLA influence the referred parameters. Four
conditions were tested: low molecular weight amorphous and semi-crystalline PLLA disks, and
high molecular weight amorphous and semi-crystalline PLLA disks, obtained from hot press. The
thermal properties of the studied materials were accessed by differential scanning calorimetry. For
the cell culture studies a human osteosarcoma cell line (SaOS-2) was chosen. Disks were immersed
in a cell suspension containing 5x104 cells/ml and kept in culture for period...
A three-dimensional composite material was produced from microporous coralline origin hydroxyapatite (HA) microgranules, chitosan fibers and chitosan membrane. Cylindrical HA microgranules were oriented along channel direction within multichannel mould space and aligned particles were supported with fibers and a chitosan membrane. The positive replica of mould channels was clasp fixed to produce thicker scaffolds. Light microphotographs of the developed complex structure showed good adhesion between the HA particles, the fibers and the supporting membrane. The composite material showed 88% (w/w) swelling in one hour and preserved the complex structure of the original material upon long-term incubation in physiological medium. MEM extract test of HA chitosan complex showed no cell growth inhibition and cell viability assay (MTS) indicat...
Since the pioneering work dealing with the synthesis and physicochemical aspects of dendrimers,
a predictable and tunable set of compositions for therapeutic, scaffolding and
imaging systems has been reported. These are well documented, butmanyhot issues should
be examined and reviewed. Herein, a review is given on dendritic nanopolymers and their
applications that show promise in the field of regenerative medicine. This review begins with a brief overview on research merging nanotechnology and regenerative medicine.
Fundamentals of the synthesis and macromolecular structure of dendritic polymers are
provided. Dendrimers fulfill the requirements as carriers for gene, nucleic acids, bioactive
molecules and peptide/protein delivery aimed at modulate the cells functions, in vitro
and in vivo. However, to make use of this potential, toxico...
