The beneficial effect of delayed compressive loading on tissue-engineered cartilage constructs cultured with TGF-β3

SummaryObjectiveTo determine whether the functional properties of tissue-engineered constructs cultured in a chemically-defined medium supplemented briefly with TGF-β3 can be enhanced with the application of dynamic deformational loading.MethodsPrimary immature bovine cells (2–3 months old) were encapsulated in agarose hydrogel (2%, 30 × 106 cells/ml) and cultured in chemically-defined medium supplemented for the first 2 weeks with transforming growth factor beta 3 (TGF-β3) (10 μg/ml). Physiologic deformational loading (1 Hz, 3 h/day, 10% unconfined deformation initially and tapering to 2% peak-to-peak deformation by day 42) was applied either concurrent with or after the period of TGF-β3 supplementation. Mechanical and biochemical properties were evaluated up to day 56.ResultsDynamic deformational loading applied concurrently with TGF-β3 supplementation yielded significantly lower (−90%) overall mechanical properties when compared to free-swelling controls. In contrast, the same loading protocol applied after the discontinuation of the growth factor resulted in significantly increased (+10%) overall mechanical properties relative to free-swelling controls. Equilibrium modulus values reach 1306 ± 79 kPa and glycosaminoglycan levels reach 8.7 ± 1.6% w.w. during this 8-week period and are similar to host cartilage properties (994 ± 280 kPa, 6.3 ± 0.9% w.w.).ConclusionsAn optimal strategy for the functional tissue engineering of articular cartilage, particularly to accelerate construct development, may incorporate sequential application of different growth factors and applied deformational loading.