Sodium alginate sponges with or without sodium hyaluronate: In vitro engineering of cartilage

Studies are underway to design biosystems containing embedded chondrocytes to fill osteochondral defects and to produce a tissue close to native carti lage. In the present report, a new alginate three-dimensional support for c hondrocyte culture is described. A sodium alginate solution, with or withou t hyaluronic acid (HA), was freeze-dried to obtain large-porosity sponges. This formulation was compared with a hydrogel of the same composition. In t he sponge formulation, macroscopic and microscopic studies demonstrated the formation of a macroporous network (average pore size, 174 mum) associated with a microporous one (average pore size, 250 nm). Histological and bioch emical studies showed that, when loaded with HA, the sponge provides an ada pted environment for proteoglycan and colla,,en synthesis by chondrocytes. Cytoskeleton organization was studied by three-dimensional fluorescence mic roscopy (CellScan EPR (TM)). Chondrocytes exhibit a marked spherical shape with a nonoriented and sparse actin microfilament network. Type II collagen was detected in both types of sponges (with or without HA) using immunoche mistry. In conclusion, the sponge formulation affords new perspectives with respect to the in vitro production of "artificial" cartilage. Furthermore, the presence of hyaluronate within the alginate sponge mimics a functional environment, suitable for the production by embedded chondrocytes of an ex tracellular matrix. (C) 2001 John Wiley & Sons, Inc.