Nutrient deprivation of tendon-derived cells and its effect on collagen matrix integrity - mimicking graft remodelling after ACL reconstruction in vitro running title: cell starvation vs collagen integrity.

PURPOSE: After anterior cruciate ligament reconstruction surgeries, tendon grafts lose their mechanical integrity in vivo. Both auto- and allografts contain dead cells, and remaining viable cells are restricted temporarily from abundant nutrient access. To evaluate a possible connection, nutrient deprivation was hypothesized to reduce cell viability, compromising tissue mechanics as cells adopt a catabolic state.

MATERIALS AND

METHODS

Taking inspiration from the graft environment, collagenous tendon-mimics with tendon-derived cells were reconstituted in vitro. Subsequently, tendon-mimics were cultured at varying glucose and serum concentrations, ranging from complete medium (5 mM glucose, 2.5% serum), to mild deprivation (0.5 mM glucose, no serum), extreme deprivation (0 mM glucose, no serum), and a frozen control group (0 mM glucose, no serum).

RESULTS

In the complete medium group, cell viability remained stable, improving tendon-mimic mechanics. Tendon cells were resilient to mild nutrient deprivation, maintaining viability. However, at extreme nutrient deprivation or tissue freezing, cell viability dropped significantly. Surprisingly, mechanical properties remained unaltered in all the groups, except the complete medium group. MMP8 secretion and activation confirmed a catabolic potential only in the complete medium group, while no further MMPs were secreted or activated in the nutrient-deprived groups. This suggests that viable cells that are exposed to a nutrient deprived environment likely lack the energy to exert contractile forces or produce/activate MMPs.

CONCLUSIONS

This study revealed that tendon-derived cells do not compromise collagenous tendon-mimic integrity under nutrient-deprived conditions in an in vitro model, highlighting the resilience of tenocytes in maintaining tissue structure.