A Polyethylene Glycol-Crosslinked Serum Albumin/Hyaluronan Hydrogel for the Cultivation of Chondrogenic Cell Types

Hydrogels are gaining increasing interest as a structural basis for regenerative cell implants. Here we present in vitro data on growth and differentiation of human mesenchymal stromal precursor cells (MSCs), adult human knee chondrocytes, and adult human intervertebral disk cells in a gel based on PEG-crosslinked serum albumin, supplemented with 4% hyaluronan (HSA-HA). Each gel culture was compared to its parallel proliferating monolayer (PML) culture and non-proliferating high density monolayer culture (HDML). MSCs were chondrogenically induced in both standard micromass (MM) cultures and HSA-HA. Cell viability in HSA-HA was above 90%. Chondrogenic differentiation was defined by changes in the expression of the mRNA for collagen types I, II, and X, for aggrecan, for alkaline phosphatase (ALP), and for hyaluronan synthases-2 and -3 (has-2, has-3). For disk cells and chondrocytes, the changes for collagen type II and aggrecan were in the range of up to 100-fold, depending on the human individual. After induction, MSCs differentiated equally well in MM and HSA-HA, showing increases spanning several orders of magnitude compared to uninduced monolayer (ML) cells. For has-2 and has-3, the changes were less obvious, but interestingly, the ratio of has-2/has-3 expression in HSA-HA cultures decreased approximately 40-fold for disk cells, remained unchanged for chondrocytes, but increased sevenfold for MSCs, when compared to the corresponding ML cultures. Taken together, HSA-HA revealed its potential as an anchoring hydrogel for chondrogenic cell types.