Biomedical subjects

Hannah K Heywood

Publications and source records attributed to Hannah K Heywood.

3 recordsLinked to original sources

PubMed2006

Rate of oxygen consumption by isolated articular chondrocytes is sensitive to medium glucose concentration.

Cartilage tissue engineering typically involves the culture of isolated chondrocytes within a scaffold material. The oxygen tension within the engineered tissue is known to be an essential parameter for implant success. This will be sensitive to the oxygen consumption behavior of the embedded chondrocytes, which remains to be characterized. We report that the oxygen consumption of bovine articular chondrocytes is sensitive to glucose deprivation below 2.7 mM, increasing from a basal level of 9.6x10(-16) to <18.4x10(-16) mol/cell.h in 1.3 mM glucose. Further studies examined the influence of selecting high (18.4 mM) or low (5.1 mM) glucose medium on the oxygen tension in 2 mm thick cellular agarose constructs. A relative upregulation of oxygen consumption was observed in constructs cultured in low glucose medium. This resulted in the near-anoxic oxygen concentration of 5 microM oxygen in constructs seeded with 40x10(6) cells/ml, compared to 57 microM in the corresponding high glucose culture. The upregulation of oxygen consumption generally corresponded to the inhibition of glycolysis, which is consistent with the Crabtree phenomenon. Medium osmolarity (316-600 mOsm) had minimal effects on chondrocyte oxygen consumption rate. In conclusion, glucose availability is a critical parameter that regulates the oxygen tension within tissue engineered constructs.

Animals↗

PubMed2005

Nutrient utilization by bovine articular chondrocytes: a combined experimental and theoretical approach.

A combined experimental-numerical approach was adopted to characterize glucose and oxygen uptake and lactate production by bovine articular chondrocytes in a model system. For a wide range of cell concentrations, cells in agarose were supplemented with either low or high glucose medium. During an initial culture phase of 48 h, oxygen was monitored noninvasively using a biosensor system. Glucose and lactate were determined by medium sampling. In order to quantify glucose and oxygen uptake, a finite element approach was adopted to describe diffusion and uptake in the experimental model. Numerical predictions of lactate, based on simple relations for cell metabolism, were found to agree well for low glucose, but not for high glucose medium. Oxygen did not play a role in either case. Given the close association between chondrocyte energy metabolism and matrix synthesis, a quantifiable prediction of utilization can present a valuable contribution in the optimization of tissue engineering conditions.

Animals↗

PubMedDate not supplied

Cellular utilization determines viability and matrix distribution profiles in chondrocyte-seeded alginate constructs.

The long-term success of any cellular construct used for cartilage tissue engineering is dependent on the maintenance of cell viability throughout the construct thickness. Furthermore, the cells must continue to be metabolically active in order to synthesize a mechanically functional extracellular matrix (ECM). In the present study, a live-dead staining technique and systematic profiling procedure enabled the spatial and temporal distribution of chondrocyte viability to be characterized within 4-mm-thick alginate scaffolds. ECM distribution after 14 days of culture is described both biochemically and histologically and the mechanical functionality of the constructs was assessed by an unconfined compression test. Parameters investigated included alginate permeability, cell-seeding density, and volume of culture medium. Nonhomogeneity of cell and matrix distribution was evident, with greater densities of both parameters in the periphery of the constructs. The culture time preceding central viability loss was inversely related to cell density but relatively independent of scaffold density. However, homogeneity could be attained with increasing medium volume, as evidenced with cell and matrix distribution for cultures in 6.4 mL of medium per 10(6) cells. Moreover, the mechanical properties of the construct were enhanced by culture in increasing volumes of medium. This work indicates that cellular utilization determines the nonhomogeneous nature of cartilage formation in three-dimensional constructs and presents a guide to nonlimiting medium volumes for static culture conditions.

Adaptation, Physiological↗