Regional cell density distribution and oxygen consumption rates in porcine TMJ discs: an explant study

Abstract

Objective To determine the regional cell density distribution and basal oxygen consumption rates (based on tissue volume and cell number) of temporomandibular joint (TMJ) discs and further examine the impact of oxygen tension on these rates. Design TMJ discs from pigs aged 6–8 months were divided into five regions: anterior, intermediate, posterior, lateral and medial. The cell density was determined using confocal laser scanning microscopy. The change in oxygen tension was recorded while TMJ disc explants were cultured in sealed metabolism chambers. The volume based oxygen consumption rate of explants was determined by theoretical curve fitting of the recoded oxygen tension data with the Michaelis-Menten equation. The rate on a per-cell basis was calculated based on the cell density measurements and volume based rate measured in another group of discs. Results The overall cell density (mean, 95% CI) was 51.3(21.3–81.3)×106cells/mL wet tissue. Along the anteroposterior axis, the anterior band had 25.5% higher cell density than the intermediate zone (p<0.02) and 29.1% higher than the posterior band (p<0.008). Along the mediolateral axes, the medial region had 26.2% higher cell density than the intermediate zone (p<0.04) and 25.4% higher than the lateral region (p<0.045). The overall volume and cell based maximum oxygen consumption rates were 1.44(0.44–2.44) μmol/mL wet tissue/hr and 28.7(12.2–45.2) nmol/106 cells/hr, respectively. The central regions (intermediate, lateral, and medial) had significantly higher volume based (p<0.02) and cell based (p<0.005) oxygen consumption rates than the anterior and posterior bands. At high oxygen tension, the oxygen consumption rate remained constant, but dropped as oxygen tension fell below 5%. Conclusions The TMJ disc had higher cell density and oxygen consumption rates than articular cartilage reported in the literature. These results suggest that a steeper oxygen gradient may exist in the TMJ disc and may be vulnerable to pathological events that impede nutrient supply.

The effects of oxygen level and glucose concentration on the metabolism of porcine TMJ disc cells

“…Both articular cartilage chondrocytes and IVD cells, which utilize glycolytic metabolism in both high and low levels of oxygen, have extremely low oxygen consumption rates. In contrast, Kuo et al reported a significantly higher oxygen consumption rate of porcine TMJ disc cells 22 , compared to articular cartilage chondrocytes 27 and IVD cells 35 , which in combination with our present findings, may be related to oxidative phosphorylation, and thus, a significant Pasteur effect for TMJ disc cells, but further investigation into the energy metabolism is necessary to confirm. Future studies to determine the effects of hypoxia and glucose concentrations in media on other key metabolites, such as glucose consumption and lactic acid production, in the TMJ disc cells may provide more information.…”

“…Moreover, our cell metabolic studies have shown that the TMJ disc has a higher cell density and higher oxygen consumption rates compared to articular cartilage and the IVD 22 . Therefore, it is likely that a steeper nutrient gradient may exist in TMJ discs and thus, it is more vulnerable to pathological events which impede nutrient supply, including sustained joint loading due to jaw clenching and bruxism.…”

“…In the avascular TMJ disc, the oxygen and glucose gradient may be steeper than that of articular cartilage, because of its higher cell density and rates of nutrient consumption 22 and lower solute diffusivities through the extracellular matrix 19-21 . This suggests that TMJ disc cells are more susceptible to pathological changes which impede nutrient supply, such as sustained joint loading due to jaw clenching or bruxism.…”

Biomechanical and biochemical outcomes of porcine temporomandibular joint disc deformation

“…The predominance of a folded disc configuration observed here mirrors results from an MRI study showing a folded type deformation was the predominant (43%) configuration of discs displaced without reduction (11). Due to the advanced age of the pigs, all dimensions of the discs measured in this study were larger than similar measurements reported in literature (14, 29). The majority of other comparative studies use discs obtained from animals aged 3–12 months (14, 19, 20, 30, 31) however skeletal maturity is not reached until at least 1 year of age (15).…”

Engineered Microporosity: Enhancing the Early Regenerative Potential of Decellularized Temporomandibular Joint Discs

“…[33][34][35] These works describe the application of a novel scaffold development addressing the hypothesis that incorporation of an artificial path of infiltration for cells, nutrients, wastes, oxygen, and other small molecules will improve a naturally derived acellular scaffold's potential for cellular integration and early remodeling capacity while retaining the native tissue's biochemical and biomechanical properties.…”