Biomedical subjects

Huang-Chi Chen

Publications and source records attributed to Huang-Chi Chen.

6 recordsLinked to original sources

PubMed2006

Bioreactors for tissue engineering.

Bioreactors are essential in tissue engineering, not only because they provide an in vitro environment mimicking in vivo conditions for the growth of tissue substitutes, but also because they enable systematic studies of the responses of living tissues to various mechanical and biochemical cues. The basic principles of bioreactor design are reviewed, the bioreactors commonly used for the tissue engineering of cartilage, bone and cardiovascular systems are assessed in terms of their performance and usefulness. Several novel bioreactor types are also reviewed.

Animals↗

PubMed2006

Determination of the baculovirus transducing titer in mammalian cells.

Baculovirus has emerged as a promising vector for in vivo or ex vivo gene therapy. To date, the infectious titer and multiplicity of infection (MOI) based on the ability of baculovirus to infect insect cells are commonly adopted to indicate the virus dosage. However, the infectious titer and MOI do not reliably represent the baculovirus transducing ability, making the comparison of baculovirus-mediated gene transfer difficult. To determine the baculovirus transducing ability more rapidly and reliably, we developed a protocol to evaluate the transducing titers of baculovirus stocks. The virus was diluted twofold serially and used to transduce HeLa cells. The resultant transduction efficiencies were measured by flow cytometry for the calculation of transducing titers. Compared to the infectious titer, the determination of transducing titer is more reproducible as the standard deviations among measurements are smaller. Also, the transducing titers can be obtained in 24 h, which is significantly faster as opposed to 4-7 days to obtain the infectious titer. More importantly, we demonstrated that baculoviruses with higher transducing titers could transduce cells at higher efficiency and yield stronger and longer transgene expression, confirming that the transducing titer was representative of the baculovirus transducing ability. This finding is particularly significant for ex vivo gene delivery whereby unconcentrated viruses are used for transduction and long-term transgene expression is desired. In this regard, our titration protocol provides a simple, fast, and reliable measure to evaluate the quality of virus stocks during virus production and purification, and is helpful to predict the performance of vector supernatants and ensure reproducible gene delivery experiments.

Baculoviridae↗

PubMed2006

Combination of baculovirus-mediated gene transfer and rotating-shaft bioreactor for cartilage tissue engineering.

We have previously demonstrated efficient baculovirus transduction of rat chondrocytes in 6-well plates. To further explore the potential of baculovirus in cartilage tissue engineering, the baculovirus-transduced chondrocytes were seeded into porous scaffolds and cultivated in a rotating-shaft bioreactor (RSB) which was developed for two-phase cultivation of tissue engineered cartilage. The baculovirus transduction resulted in efficiencies up to 90%, and affected neither cell adhesion to the scaffolds nor cell survival in the RSB. After 4-week RSB cultivation, the transduced cells remained highly differentiated and grew into constructs that resembled the untransduced constructs with regard to gross appearance, construct size, cell morphology, cell spatial distribution, glycosaminoglycan and collagen production and deposition. Importantly, baculovirus transduction did not alter the expression of chondrocytic genes. These data confirmed that baculovirus transduction neither harms chondrocytes nor retards the formation of cartilage-like tissues in the RSB, thus implicating the potentials of combining baculovirus-mediated gene transfer with RSB cultivation in in vitro cartilage tissue engineering.

Aggrecans↗

PubMed2005

Rational development of GAG-augmented chitosan membranes by fractional factorial design methodology.

To develop a novel biomaterial for chondrocyte culture, 8 glycosaminoglycan (GAG)/chitosan membranes (groups N1-N8) were prepared, with the aid of a 2-level 2(4-1) fractional factorial design, by co-immobilizing chondroitin-4-sulfate (CSA), chondroitin-6-sulfate (CSC), dermatan sulfate (DS), and heparin to chitosan membranes. The fractional factorial design allowed us to partly interpret the effects of individual GAGs and two-way interactions between GAGs. Within the level range of -1 and +1, low CSA level (2.6 mg) is favorable for collagen synthesis but not for cell proliferation. High CSC level (1.3 mg) is favorable for GAG production but not for cell proliferation. Conversely, high heparin (0.33 mg) and DS (0.13 mg) levels are desired for cell proliferation but not for the production of collagen and GAG. Moreover, the two-way interactions between GAGs influence the cell behavior. Among the 8 GAG/chitosan membranes, N1 and N4 (containing low CSA and heparin levels) lead to the maintenance of proper chondrocyte phenotype, as judged by the chondrocyte-like morphology, modest cell expansion, higher GAG and collagen production and proper cartilage marker gene expression. In conclusion, this approach provides a means of rationally predicting and evaluating the proper formulation of GAG/chitosan membranes and may facilitate the rational design of other tissue engineering scaffolds.

Animals↗

PubMed2004

Highly efficient baculovirus-mediated gene transfer into rat chondrocytes.

To explore the potential of baculovirus serving as a gene delivery vector in tissue engineering of articular cartilage, the efficiencies of baculovirus-mediated gene delivery into primary rat chondrocytes were evaluated and the transduction protocol commonly employed by others (using concentrated virus at multiplicity of infection [MOI] 200 for 1 h) was found to be ineffective (<1%). Therefore, a modified protocol was adopted, which markedly enhanced the efficiency (68%). Optimization of the transduction parameters, such as incubation time (8 h), temperature (25 degrees C), and surrounding solutions (PBS), further increased the efficiency to 88% and prolonged the duration of expression to 21 days, suggesting that the cells previously considered nonpermissive to baculovirus transduction may be reexamined for their permissiveness using alternative transduction protocols. The elevated efficiency correlated well with increased virus uptake upon extended incubation time, as demonstrated by quantitative real-time polymerase chain reaction (Q-PCR). The Q-PCR also revealed the degradation of viral DNA over culture time. Although the virus transduction somewhat hindered the cell proliferation, growth rate could be restored in the long-term culture. More importantly, transduced cells could secrete articular cartilage-specific type II collagen and glycosaminoglycan as well as mock-transduced cells, confirming that normal differentiation state of rat chondrocytes is retained upon baculovirus transduction. Taken together, these data indicate that baculovirus is a safe and highly efficient gene delivery vehicle into rat chondrocytes.

Animals↗

PubMedDate not supplied

A novel rotating-shaft bioreactor for two-phase cultivation of tissue-engineered cartilage.

A novel rotating-shaft bioreactor (RSB) was developed for two-phase cultivation of tissue-engineered cartilage. The reactor consisted of a rotating shaft on which the chondrocyte/scaffold constructs (7.5 mm diameter x 3.5 mm thickness) were fixed and a reactor vessel half-filled with medium. The horizontal rotation of the shaft resulted in alternating exposure of the constructs to gas and liquid phases, thus leading to efficient oxygen and nutrient transfer, as well as periodically changing, mild shear stress exerting on the construct surfaces (0-0.32 dyn/cm2 at 10 rpm), as revealed by computer simulation. Strategic operation of the RSB (maintaining rotating speed at 10 rpm for 3 weeks and lowering the speed to 2 rpm in week 4) in combination with higher seeding density (6 x 10(6) chondrocytes/scaffold) and medium perfusion resulted in uniform cell distribution and increased glycosaminoglycan (3.1 mg/scaffold) and collagen (7.0 mg/scaffold) deposition. The 4-week constructs resembled native cartilages in terms of not only gross appearance and cell morphology but also distributions of glycosaminoglycan, total collagen, and type II collagen, confirming the maintenance of chondrocyte phenotype and formation of cartilage-like constructs in the RSB cultures. In summary, the novel RSB may be implicated for in vitro study of chondrogenesis and de novo cartilage development under periodic mechanical loading. With proper optimization of the culture conditions, a RSB may be employed for the production of cartilage-like constructs.

Animals↗