Biomedical subjects

Kee Woei Ng

Publications and source records attributed to Kee Woei Ng.

6 recordsLinked to original sources

PubMed2006

Reduced contraction of skin equivalent engineered using cell sheets cultured in 3D matrices.

In order to alleviate their extensive contraction, human fibroblast sheets were cultured in combination with three-dimensional matrices (knitted poly(lactic-co-glycolic acid) (PLGA) mesh and collagen-hyaluronic acid (CHA) sponge) to form contiguous dermal constructs for tissue engineering a bilayered skin equivalent. The resulting constructs were viable, and supported the development of bilayered skin equivalents which did not contract over the 4-week culture period. When implanted into full-thickness wounds in nude rats, cultured skin equivalents based on PLGA meshes registered a take rate of 100% and showed an extent of wound contraction that was statistically similar to autografts, while wounds grafted with PLGA meshes without cell sheets contracted more than autografts. On the other hand, skin equivalents based on CHA sponges were all sloughed off within 2 weeks of transplantation. In all cell sheet-incorporated specimens, cells from the constructs infiltrated and produced extracellular matrix within the neo-dermis, shown by positive human leukocyte antigen and collagen I expression. This technique offers an alternative approach for scaffold-based tissue engineering to produce mechanically stable grafts with matured neo-tissue.

Animals↗

PubMed2005

Assimilating cell sheets and hybrid scaffolds for dermal tissue engineering.

Cell sheets can be used to produce neo-tissue with mature extracellular matrix. However, extensive contraction of cell sheets remains a problem. We devised a technique to overcome this problem and applied it to tissue engineer a dermal construct. Human dermal fibroblasts were cultured with poly(lactic-co-glycolic acid)-collagen meshes and collagen-hyaluronic acid foams. Resulting cell sheets were folded over the scaffolds to form dermal constructs. Human keratinocytes were cultured on these dermal constructs to assess their ability to support bilayered skin regeneration. Dermal constructs produced with collagen-hyaluronic acid foams showed minimal contraction, while those with poly(lactic-co-glycolic acid)-collagen meshes curled up. Cell proliferation and metabolic activity profiles were characterized with PicoGreen and AlamarBlue assays, respectively. Fluorescent labeling showed high cell viability and F-actin expression within the constructs. Collagen deposition was detected by immunocytochemistry and electron microscopy. Transforming Growth Factor-alpha and beta1, Keratinocyte Growth Factor and Vascular Endothelial Growth Factor were produced at various stages of culture, measured by RT-PCR and ELISA. These results indicated that assimilating cell sheets with mechanically stable scaffolds could produce viable dermal-like constructs that do not contract. Repeated enzymatic treatment cycles for cell expansion is unnecessary, while the issue of poor cell seeding efficiency in scaffolds is eliminated.

Actins↗

PubMed2003

Elastic cartilage engineering using novel scaffold architectures in combination with a biomimetic cell carrier.

Tissue engineering of an elastic cartilage graft that meets the criterion for both structural and functional integration into host tissue, as well as allowing for a clinically tolerable immune response, is a challenging endeavour. Conventional scaffold technologies have limitations in their ability to design and fabricate complex-shaped matrix architectures of structural and mechanical equivalence to elastic cartilage found in the body. We attempted to investigate the potential of conventionally isolated and passaged chondrocytes (2D environment) when seeded and cultured in combination with a biomimetic hydrogel in a mechanically stable and biomimetic composite matrix to form elastic cartilage within ectopic implantation sites. In vitro cultured scaffold/hydrogel/chondrocytes constructs showed islets of cartilage and mineralized tissue formation within the cell-seeded specimens in both pig and rabbit models. Specimens with no cells seeded showed only vascularized fibrous tissue ingrowth. These studies demonstrated the potential of such scaffold/hydrogel/cell constructs to support chondrogenesis in vivo. However, it also showed that even mechanically stable scaffolds do not allow regeneration of a large mass of structural and functional cartilage within a matrix architecture seeded with 2D passaged chondrocytes in combination with a cell biomimetic carrier. Hence, future experiments will be designed to evaluate an initial 3D culture of chondrocytes, effect on cell phenotype and their subsequent culture within biomimetic 3D scaffold/cell constructs.

Adult↗

PubMed2003

Preliminary study of a polycaprolactone membrane utilized as epidermal substrate.

Solvent-cast sheets of polycaprolactone were biaxially stretched to produce 10-15 microm thick films. PCL films were found to have a tensile strength of 55 MPa which is about two and a half times stronger than native skin. One of our previous studies using non-coated PCL membranes showed that only 36% of the membrane surface was covered with keratinocytes after 9 days of culture. The present study examined the effects of coating the surface of PCL membranes with fibrin on the proliferation of keratinocytes. Qualitative analysis revealed that the cells attached and proliferated better on coated PCL films. Keratinocytes exhibited healthy cobblestone morphology and proliferated as continuous monolayers over a period of 16 days. The results indicated that fibrin coated PCL films would support the attachment and proliferation of human keratinocytes and have the potential to be applied as a matrix material for tissue engineering an epidermal equivalent.

Journal Article↗

PubMed2002

Induction of ectopic bone formation by using human periosteal cells in combination with a novel scaffold technology.

Due to their osteogenic germination potential, periosteum-derived osteoprogenitor cells are a potential source for tissue engineering a bone graft that could be used to regenerate skeletal defects. In this study we evaluated if ectopic bone formation could be induced by a construct made of human periosteal cells and a novel scaffold architecture whose mechanical properties are in the range of cancellous bone. Biopsies from human calvarial periosteum were harvested and cells were isolated from the inner cambial layer. Fifty thousand periosteal cells were seeded into the scaffolds measuring 6 x 6 x 2 mm. The cell-scaffold constructs were cultured for a period of 3 weeks prior to implantation into balb C nude mice. Mice were sacrificed and implants were analyzed 6 and 17 weeks postoperatively. Immunohistochemical analysis confirmed the osteoblastic phenotype of the seeded cells. Formation of focal adhesions and stress fibers could be observed in both scaffold architectures. Three-dimensional cell proliferation was observed after 2 weeks of culturing with centripetal growth pattern inside the pore network. The deposition of calcified extracellular matrix was observed after 3 weeks of culturing. In vivo, endochondral bone formation with osteoid production was detectable via von Kossa and Osteocalcin staining after 6 and 17 weeks. Histology and SEM revealed that the entire scaffold/bone grafts were penetrated by a vascular network. This study showed the potential of bone tissue engineering by using human periosteal cells in combination with a novel scaffold technology.

Animals↗

PubMedDate not supplied

Evaluation of a tissue-engineered membrane-cell construct for guided bone regeneration.

PURPOSE: Currently, a number of bioresorbable and biodegradable membranes used for guided bone regeneration lead to incomplete tissue regeneration. Poor mechanical properties, short degradation time, and the lack of integrated biologic components result in the inability to create and maintain an appropriate environment and to actively support tissue remodeling. In the present study, the osteogenic potential of human calvarial periosteal cells in combination with ultrathin polycaprolactone (pc2) membranes of a slow biodegradation rate was investigated. MATERIALS AND METHODS: In vitro and in vivo analyses of the tissue-engineered constructs were conducted using imaging techniques, immunohistochemistry, and histology. Two types of membranes were investigated. Group 1 consisted of a plain membrane, and in group 2 membranes were treated with sodium hydroxide. RESULTS: In vitro results showed that osteoblast-like cells attached and proliferated on the membranes with the formation of extracellular matrix. Sodium hydroxide-treated membranes showed enhanced cell attachment and proliferation kinetics, resulting in a dense cellular layer after 2 weeks in culture. In vivo mineralized tissue formation in association with vascularization was observed. Extracellular matrix calcification with nodule formation was detected via histology as well as scanning electron microscopy. DISCUSSION: PCL membranes support the attachment, growth, and osteogenic differentiation of human primary osteoblast-like cells. Sodium hydroxide-treated membranes demonstrated increased cell attachment resulting from increased hydrophilicity. CONCLUSION: These findings have potential application in the development of a new generation of osteoconductive membranes.

Absorbable Implants↗