(190h) Biomolecular Rate Indicators of Human Mesenchymal Stem Cell Chondrogenesis

Human Mesenchymal Stem Cells (hMSCs) are a promising cell source for cartilage tissue engineering. However, the end tissue quality in hMSCs-chondrogenesis is highly variable and dependent on culture conditions such as media composition and mass transport and donors. Currently, assessment of hMSC chondrogenesis requires tissue sacrifice preventing longitudinal investigation of the engineered tissue. As a result, tissue-specific release criteria cannot be established. hMSCs primarily use glucose and its derivatives for biosynthesis of cartilage biomolecules such as glycosaminoglycan (GAG) and hydroxyproline (HYP). Glycolysis is a key metabolic pathway in chondrocytes leading to lactate production. Therefore, we hypothesized that both glucose consumption and lactate production can serve as indicators of end tissue quality during chondrogenesis.

In this project, we investigated the glucose uptake and lactate production of hMSCs during chondrogenesis under an aggregate culture system using various initial glucose concentrations (1, 2, 3 and 4.5 g/l) with different medium change frequencies (0.5 day^-1 and 1 day^-1). Glucose uptake and lactate production profiles were obtained from medium samples collected every day. Quantitative GAG and HYP measurements were performed using aggregates harvested at different time points (day 7, 14 and 21). The results showed that higher initial glucose concentration and higher medium change frequency led to better tissue quality (GAG and HYP content) and larger constructs. In addition, our data showed a direct linear relationship between cumulative glucose consumption or lactate production, and GAG or HYP content in chondrogenic aggregates. These results suggest that glucose consumption and lactate production can be predictors for end point tissue biochemical quality of hMSCs chondrogenesis. Such predictors can make it possible to monitor the chondrogenic process in real time and non-invasively, allowing dynamic intervention during the culture period for improved chondrogenic result.