Chondrocyte response to high regimens of cyclic hydrostatic pressure in 3-dimensional engineered constructs

Purpose: Despite widespread use of 3-dimensional (3D) micro-porous scaffolds to promote their potential application in cartilage tissue engineering, only a few studies have examined the response to hydrostatic pressure of engineered constructs. A high cyclic pressurization, currently believed to be the predominant mechanical signal perceived by cells in articular cartilage, was used here to stimulate bovine articular chondrocytes cultured in a synthetic 3D porous scaffold (DegraPol). Methods: Construct cultivation lasted 3 days with applied pressurization cycles of amplitude 10 MPa, frequency 0.33 Hz, and stimulation sessions of 4 hours/day. Results: At 3 days of culture, with respect to pre-culture conditions, the viability of the pressurized constructs did not vary, whereas it underwent a 16% drop in the unpressurized controls. Synthesis of α-actin was 34% lower in all cultured constructs. Synthesis of collagen II/collagen I did not vary in pressurized constructs, was 76% lower in unpressurized controls, and was around 230% higher in pressurized constructs with respect to unpressurized controls. Chondrocytes showed a phenotypic spherical morphology at time zero and at 3 days of pressurized culture. Conclusions: Although the passage from 2D expansion to 3D geometry was effective to guide cell differentiation, only mechanical conditioning enabled the maintenance and further cell differentiation toward a mature chondrocytic phenotype.