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PubMed2006

[Perfusion-weighted magnetic resonance imaging for monitoring vascularization in tissue-engineered bone in rhesuses].

OBJECTIVE: To assess the value of perfusion-weighted magnetic resonance (MR) imaging (PWMRI) in monitoring vascularization in tissue-engineered bone graft. METHODS: Tibial diaphyseal defect of 20 mm was induced in 25 lower limbs of 13 rhesuses and fixed with an AO reconstruction plate with 7 holes. The monkeys were randomized into 5 groups according to the materials used for defect filling: group A, with beta-tricalcium phosphate (beta-TCP), bone marrow stromal cells (BMSCs) and blood vessel bundles; group B, with beta-TCP and blood vessel bundles; group C, with beta-TCP and BMSCs; group D, with beta-TCP, and group E without filling. PWMRI, X-ray, and radionuclide imaging were carried out at weeks 4, 8, 12 postoperatively. The maximum slope rates of the single intensity-time curve (SS(max)) and the baseline values (SI(baseline)) on the same time points were calculated. Transmittances on the X-ray films and isotope counts in the region of interest (ROI) were assessed and calculated. RESULTS: Compared with other groups, group A showed the highest SS(max) at weeks 4, 8, and 12 postoperatively, and its SS(max) at week 8 was significantly higher than that at week 4 (P=0.003). The SS(max) was positively related to isotope counts in ROI at week 8 after operation (r(s)=0.899, P=0.038), and inversely related to transmittance on X-ray films at week 12 (r(s)=-0.892, P=0.042). CONCLUSION: The SS(max) of the single intensity-time curve can accurately reflect the vascularization of the tissue-engineered bone graft, and PWMRI allows sensitive, quantitative, noninvasive and radiation-free vascularization monitoring.

Animals↗

PubMed2000

The science of tissue engineering.

This article reviews the development of tissue engineering during the last decade. The science began to fully develop in association with efforts to combine viable cells with biocompatible material. The history and scope of this new field are presented. Basic principles of cell biology, materials, and technologies are discussed. Future challenges in the field are presented.

Coated Materials, Biocompatible↗

PubMed2005

Demineralized bone matrix gelatin as scaffold for osteochondral tissue engineering.

To develop a single-unit osteochondral tissue with demineralized bone matrix gelatin (BMG), rabbit chondrocytes were cultured on demineralized bone matrix gelatin for 6 weeks. The engineered osteochondral tissue was characterized with histology, immunolocalization, TEM, SEM, biochemical assay, and gene expression analysis. About 1.3mm viable neo-cartilage was produced on demineralized BMG. RT-PCR, immunohistochemistry, TEM, biochemical assay, and histology revealed hyaline-like cartilage with zonal layers, intense type II collagen expression, and abundant proteoglycan content formed upon BMG compared with normal cartilage. But hydroxyproline content and type I collagen gene and protein expressions were significantly lower. We consider engineering cartilage tissue with chondrocytes cultured on allogenic demineralized BMG is a good approach for osteochondral tissue engineering.

Animals↗

PubMed2007

Biomaterials and scaffold design: key to tissue-engineering cartilage.

Cartilage remains one of the most challenging tissues to reconstruct or replace, owing to its complex geometry in facial structures and mechanical strength at articular surfaces in joints. This non-vascular tissue has poor replicative capacity and damage results in its functionally inferior repair tissue, fibrocartilage. This has led to a drive for advancements in tissue engineering. The variety of polymers and fabrication techniques available continues to expand. Pore size, porosity, biocompatibility, shape specificity, integration with native tissue, degradation tailored to rate of neocartilage formation and cost efficiency are important factors which need consideration in the development of a scaffold. The present review considers the current polymers and fabrication methodologies used in scaffold engineering for cartilage and postulates whether we are closer to developing the ideal scaffold for clinical application.

Animals↗

PubMed2006

hCTLA4-gene modified human bone marrow-derived mesenchymal stem cells as allogeneic seed cells in bone tissue engineering.

Immune rejection of heterogeneic seed cells, even of low antigenicity human bone marrow derived mesenchymal stem cells (hBMMSCs), remains an obstacle for bone tissue engineering. It is still a question how to transfer the gene of human cytotoxic T lymphocyte-associated antigen 4-Ig (CTLA4-Ig), a well-known ligand for CD80/CD86, to hBMMSCs to prolong survival time while not interfering with their osteogenesis in vivo. Our data, for the first time, clearly demonstrate that CTLA4-Ig gene modified hBMMSCs could normally differentiate to osteoblasts in vitro, significantly inhibit immune response in the model of mixed lymphocyte culture, and survive until bone tissue formed in vivo. Thus, CTLA4Ig gene-modified hBMMSCs might be promising seed cells for bone tissue engineering.

Animals↗

PubMed2005

Anchoring dental implant in tissue-engineered bone using composite scaffold: a preliminary study in nude mouse model.

PURPOSE: The purpose of this study was to fabricate a tissue-engineered bone graft anchoring dental implant with bone marrow stromal cell (bMSC) seeded coral-implant composite scaffold. MATERIALS AND METHODS: Titanium dental implants (3 mm in diameter) were inserted into the cylinder coral scaffolds (5 mm in diameter and 1 mm in wall thickness). bMSCs were isolated from iliac bone marrow of adult New Zealand White rabbits, induced by dexamethasone and seeded into the composite scaffold at the density of 2 x 10 8 /mL in 200 muL medium. Nine cell coral-implant complexes were incubated in vitro for 5 days. One complex was processed for scanning electronic microscopy. The other 8 complexes, together with 4 coral scaffold without cell acting as control, were implanted subcutaneously into nude mice back. At 1 and 2 months after implantation, 4 specimens from the experiment group and 2 specimens from the control group were harvested respectively. New bone restoration and new bone integration with dental implant were evaluated by gross inspection, manual handling test, radiographic examination, and histologic observation. RESULTS: Specimens harvested at 2 months after implantation were red and similar to native bone. Manual handling test showed that dental implants were fixed in the newly formed bone. Radiographic examination showed that most of the coral scaffold had been absorbed. Bone density x-ray shadow could be observed around the dental implant. Histologic examination showed that large amount of new bone formed around the dental implants and integrated well with the implants in some area. In the control group no bone formation was observed both macroscopically and microscopically. CONCLUSION: The results of the study suggested that the tissue-engineered bone of bMSCs seeded natural coral-implant composite scaffold is promising for dental implant anchoring, which has positive implication for clinical jaw reconstruction.

Animals↗

PubMed2005

Use of autologous tissue engineered skin to treat porcine full-thickness skin defects.

OBJECTIVE: To explore a feasible method to repair full-thickness skin defects utilizing tissue engineered techniques. METHODS: The Changfeng hybrid swines were used and the skin specimens were cut from the posterior limb girdle region, from which the keratinocytes and fibroblasts were isolated and harvested by trypsin, EDTA, and type II collagenase. The cells were seeded in Petri dishes for primary culture. When the cells were in logarithmic growth phase, they were treated with trypsin to separate them from the floor of the tissue culture dishes. A biodegradable material, Pluronic F-127, was prefabricated and mixed with these cells, and then the cell-Pluronic compounds were seeded evenly into a polyglycolic acid (PGA). Then the constructs were replanted to the autologous animals to repair the full-thickness skin defects. Histology and immunohistochemistry of the neotissue were observed in 1, 2, 4, and 8 postoperative weeks. RESULTS: The cell-Pluronic F-127-PGA compounds repaired autologous full-thickness skin defects 1 week after implantation. Histologically, the tissue engineered skin was similar to the normal skin with stratified epidermis overlying a moderately thick collageneous dermis. Three of the structural proteins in the epidermal basement membrane zone, type IV collagen, laminin, and type VII collagen were detected using immunohistochemical methods. CONCLUSIONS: By studying the histology and immunohistochemistry of the neotissue, the bioengineered skin graft holds great promise for improving healing of the skin defects.

Animals↗

PubMedDate not supplied

Age-related structural changes in cardiac valves: implications for tissue-engineered repairs.

Elderly patients would receive substantial benefits from tissue-engineered heart valves (TEHVs), but most TEHV research has not focused on applications for this growing patient population. There will be numerous technical challenges involved in developing TEHVs for the elderly, such as designing tissues to accommodate higher blood pressure and larger aortic roots that may be friable or calcified. Concomitant medications may also affect the biology of the TEHV. Due to the predominantly senescent behavior of cells from older persons, a nonautologous cell source may be required to develop the TEHV. Decellularized heart valve allografts from elderly donors may not be durable enough to use as a scaffold, but several polymer and natural biodegradable scaffolds may provide promising alternatives. The selection of cell sources, scaffolds, and mechanical/biologic conditioning will need to be precisely targeted to meet the diverse physiological, medical, and surgical requirements of elderly patients.

Aging↗

PubMed2003

A collagen-phosphophoryn sponge as a scaffold for bone tissue engineering.

Non-collagenous phosphoproteins that interact with a type-I collagen are thought to nucleate bone mineral into collagen networks of mineralized tissues. Previously, phosphophoryn cross-linked to type-I collagen was reported to be an effective nucleator of appatite. However, free phosphophoryn molecules inhibit the formation of apatite in vitro. On the basis of the above study, we expected a collagen-phosphophoryn sponge to be a good scaffold for bone-tissue engineering and examined the formation of bone in orthotopically transplanted composites of the sponge and bone marrow osteoblasts in vivo in Fischer rats. Osteoblastic primary cells were obtained from the bone shaft of femorae of Fisher rats, according to the method of Maniatopoulous et al. A suspension of marrow cells was distributed through a flask with standard culture medium and incubated at 37 degrees C. When cultures were nearly confluent after 10 days, they were concentrated by centrifugation to 10(6) cells/ml and subcultured onto the synthesized collagen-phosphophoryn sponge and a collagen sponge (control). After 14 days, the composites of collagen-phosphophoryn and osteoblastic cells as well as control composites were transplanted into bone-defect sites of Fisher rats (holes 2 mm in diameter) and then the wounds were sutured. The composites were harvested at 1-8 weeks after implantation, and stained with hematoxylin and eosin. It was found that more bone was formed in the composites of collagen-phosphophoryn sponge and osteoblasts than control composites from 1 week to 8 weeks, suggesting that the collagen-phosphophoryn sponge is a good candidate as a scaffold for bone-tissue engineering.

Animals↗

PubMed2005

Direct patterning of mammalian cells onto porous tissue engineering substrates using agarose stamps.

This paper describes simple, inexpensive, and potentially generic methodology for generating patterns of mammalian cells on porous scaffolds for tissue engineering using replica printing. Circular patterns (diameter: 200, 700, and 1000 microm) of human osteoblasts were transferred directly from topographically patterned agarose stamps onto porous hydroxyapatite scaffolds or onto fibronectin-coated glass slides. The use of hydrogel stamps provided a "wet", biocompatible surface and maintained the viability of cells adsorbed on stamps during the patterning process. Stamps inked once with suspensions of cells allowed the repeated patterning of substrates. Direct stamping of human osteoblasts (and, potentially other mammalian cells) can be used to control the size, spacing, and geometry of patterns of cells printed on porous tissue engineering substrates. This approach may find use in controlling the spatial invasion of scaffolds, promoting the hierarchical organization of cells, and in controlling cell-cell interactions as a step in preservation of phenotypes of cells.

Actins↗

PubMedDate not supplied

Biomacromolecules electrostatic self-assembly on 3-dimensional tissue engineering scaffold.

A poly(ethylenimine) (PEI) was employed to obtain a stable positively charged surface on a poly(D,L-lactide) (PDL-LA) tissue engineering scaffold. An extracellular matrix (ECM)-like biomacromolecule, gelatin, was selected as polyelectrolyte and deposit alternately with PEI on the activated PDL-LA scaffold via ESA technique. The zeta-potential result showed alternating charge of polyelectrolytes (PEI/gelatin) layering on PDL-LA microspheres. Quartz crystal microbalance (QCM) measurement further verified the gradual deposition of PEI/gelatin on the PDL-LA thin film. The combination of PEI aminolysis and the layer-by-layer technique was then explored to construct gelatin coating onto the 3-D porous PDL-LA scaffold. Scanning electronic microscopy showed that there is no notable difference between modified and unmodified PLA scaffolds, with regard to the porosity, pore diameter, and scaffold integration. The dual-tunnel confocal laser scanning microscopy indicated uniform gelatin distribution on the inner surface of the 3-D porous scaffold. The gradual build-up of protein layer on scaffold was investigated by radioiodination technique. Chondrocyte was chosen to test the cell behavior on modified and unmodified PDL-LA scaffolds. The results of the cell viability, total intracellular protein content, and cell morphology on the PEI/gelatin multilayers modified PDL-LA scaffold showed to promote chondrocyte growth. Comparing conventional coating methods, polyelectrolyte multilayers are easy and stable to prepare. It may be a promising choice for the surface modification of complex biomedical devices. These very flexible systems allow broad medical applications for drug delivery and tissue engineering.

Animals↗

PubMed2002

Bioreactors mediate the effectiveness of tissue engineering scaffolds.

We hypothesized that the mechanically active environment present in rotating bioreactors mediates the effectiveness of three-dimensional (3D) scaffolds for cartilage tissue engineering. Cartilaginous constructs were engineered by using bovine calf chondrocytes in conjunction with two scaffold materials (SM) (benzylated hyaluronan and polyglycolic acid); three scaffold structures (SS) (sponge, non-woven mesh, and composite woven/non-woven mesh); and two culture systems (CS) (a bioreactor system and petri dishes). Construct size, composition [cells, glycosaminoglycans (GAG), total collagen, and type-specific collagen mRNA expression and protein levels], and mechanical function (compressive modulus) were assessed, and individual and interactive effects of model system parameters (SM, SS, CS, SM*CS and SS*CS) were demonstrated. The CS affected cell seeding (higher yields of more spatially uniform cells were obtained in bioreactor-grown than dish-grown 3-day constructs) and subsequently affected chondrogenesis (higher cell numbers, wet weights, wet weight GAG fractions, and collagen type II levels were obtained in bioreactor-grown than dish-grown 1-month constructs). In bioreactors, mesh-based scaffolds yielded 1-month constructs with lower type I collagen levels and four-fold higher compressive moduli than corresponding sponge-based scaffolds. The data imply that interactions between bioreactors and 3D tissue engineering scaffolds can be utilized to improve the structure, function, and molecular properties of in vitro-generated cartilage.

Animals↗

PubMed2004

[The study of producing allogenic-tissue engineering cartilage].

OBJECTIVE: To explore the feasibility of producing neocartilage tissue by using allogenic chondrocytes as seeding cells, artificial absorbable scaffold-polylactic acid (PLA) as matrices. METHOD: The cartilage tissue was obtained from the four limbs of neoborn New Zealand rabbits (born 3-5 days), digested by II collagenase, proliferated in vitro, then seeded the chondrocytes on PLA scaffolds. The chondrocyte-PLA complex were cultured 7-10 days in vitro, then implanted in dorsal subcutaneous of adult New Zealand rabbits. Specimens harvested 3 weeks, 5 weeks and 7 weeks after implantation respectively and subjected to histologic analysis. RESULT: Chondrocyte-PLA complex implanted in adult new Zealand rabbits for 7 weeks, produced neo-cartilage as proved by histologic analysis, along with time extending, chondrocyte matrice secretion increased, invading inflammatory cell decreased. CONCLUSION: Using allogenic chondrocytes as seeding cells and PLA scaffold, it is successful to generate allogenic tissue-engineering cartilage in animals that have inherent immunity.

Animals↗

PubMed2004

Functional tissue engineering of autologous tunica albuginea: a possible graft for Peyronie's disease surgery.

OBJECTIVES: The aim of the present study was to generate a tissue engineered type of mechanically stable graft suitable for surgical replacement of the tunica albuginea penis. METHODS: Porcine fibroblasts isolated from open fascia biopsies were seeded on decellularized collagen matrices and then cultivated in a bioreactor under continuous multiaxial stress for up to 21 days (n=12). Static cultures without mechanical stress served as controls. Cell proliferation, cell alignment, and de novo synthesis of extracellular matrix proteins (proteoglycans, procollagen I, elastin) in these grafts was evaluated by hematoxylin-eosin, pentachrome, and immuno-staining. Additionally, the enzymatic isolation of porcine fibroblasts from X4mm skin punch biopsies (n=8) was evaluated. RESULTS: Mechanically strained cultures of fibroblasts showed a homogeneous multilayer matrix infiltration and a regular cell alignment in the direction of strain axis after 7 days, as well as a de novo production of extracellular matrix proteins compared to the static control. A large amount of viable fibroblasts was easily obtained from small skin punch biopsies. CONCLUSION: This study shows that continuous multiaxial stimuli improve proliferation and extracellular matrix synthesis of mature fibroblasts reseeded on a biological matrix making this a feasible autologous tissue engineered graft for penile surgery. For the clinical setting fibroblasts harvested from small skin biopsies can be a comfortable cell source.

Animals↗

PubMed2000

Fundamentals of biomechanics in tissue engineering of bone.

The objective of this review is to provide basic information pertaining to biomechanical aspects of bone as they relate to tissue engineering. The review is written for the general tissue engineering reader, who may not have a biomechanical engineering background. To this end, biomechanical characteristics and properties of normal and repair cortical and cancellous bone are presented. Also, this chapter intends to describe basic structure-function relationships of these two types of bone. Special emphasis is placed on salient classical and modern testing methods, with both material and structural properties described.

Animals↗

PubMed2006

Tissue-engineered peripheral nerve grafting by differentiated bone marrow stromal cells.

Bone marrow stromal cells are multipotential stem cells that contribute to the differentiation of tissues such as bone, cartilage, fat and muscle. In the experiment, we found that bone marrow stromal cells can be induced to differentiate into cells expressing characteristic markers of Schwann cells, such as S-100 and glial fibrillary acidic protein, promoting peripheral nerve regeneration. Tissue-engineered bioartificial nerve grafting of rats by differentiated bone marrow stromal cells was applied for bridging a 10 mm-long sciatic nerve defect. Twenty-eight inbred strains of female F344 rats weighing 160 approximately 200 g were randomly divided into four nerve grafting groups, with seven rats in each group. Differentiated bone marrow stromal cell-laden group: poly(lactic-co-glycolic) acid tubes with an intrinsic framework were seeded with syngeneic bone marrow stromal cells which were induced for 5 days; Schwann cell-laden group: poly(lactic-co-glycolic) acid tubes with an intrinsic framework were seeded with syngeneic Schwann cells; acellular group: poly(lactic-co-glycolic) acid tubes were only filled with an intrinsic framework; autografts group. Three months later, a series of examinations was performed, including electrophysiological methods, walking track analysis, immunohistological staining of nerves, immunostaining of S-100 and neurofilament, and axon counts. The outcome indicated that bone marrow stromal cells are able to differentiate into Schwann-like cells and Schwann-like cells could promote nerve regeneration. Bone marrow stromal cells may be potentially optional seed cells for peripheral nerve tissue engineering because of abilities of promoting axonal regeneration.

Animals↗

PubMed2006

Human serum for tissue engineering of human nasal septal cartilage.

OBJECTIVE: To compare the chondrogenic and proliferative effects of pooled human serum (HS) and fetal bovine serum (FBS) on tissue-engineered human nasal septal chondrocytes. STUDY DESIGN AND SETTING: Human chondrocytes were expanded for one passage in monolayer in medium supplemented with 10% FBS, 2% HS, 10% HS, or 20% HS. Cells were then suspended in alginate beads for 3D culture for 2 weeks with 10% FBS, 2% HS, 10% HS, or 20% HS. RESULTS: Monolayer cell yields were greater with HS than FBS. In alginate, cellular proliferation, glycosaminoglycan production per cell, and type II collagen were significantly higher with 10% HS compared to 10% FBS controls. CONCLUSION: HS results in increased proliferation and production of cartilaginous extracellular matrix by tissue-engineered human nasal septal chondrocytes, compared to FBS controls. SIGNIFICANCE: Culture with human serum may facilitate creation of neocartilage constructs that more closely resemble native tissue.

Alginates↗

PubMed2006

Electrospinning of polymeric nanofibers for tissue engineering applications: a review.

Interest in electrospinning has recently escalated due to the ability to produce materials with nanoscale properties. Electrospun fibers have been investigated as promising tissue engineering scaffolds since they mimic the nanoscale properties of native extracellular matrix. In this review, we examine electrospinning by providing a brief description of the theory behind the process, examining the effect of changing the process parameters on fiber morphology, and discussing the potential applications and impacts of electrospinning on the field of tissue engineering.

Animals↗