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

Objective: To determine whether the functional properties of tissue-engineered constructs cultured in a chemically-defined medium supplemented briefly with TGF-beta 3 can be enhanced with the application of dynamic deformational loading. Methods: Primary immature bovine cells (2-3 months old) were encapsulated in agarose hydrogel (2%, 30 x 10(6) cells/ml) and cultured in chemically-defined medium supplemented for the first 2 weeks with transforming growth factor beta 3 (TGF-beta 3) (10 mu g/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-03 supplementation. Mechanical and biochemical properties were evaluated up to day 56. Results: Dynamic deformational loading applied concurrently with TGF-beta 3 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.). Conclusions: An 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. (C) 2007 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.