Sammendrag
The native cartilage extracellular matrix (ECM) is enriched in sulfated glycosaminoglycans with
important roles in the signaling and phenotype of resident chondrocytes. Recapitulating the key
ECM components within engineered tissues through biomimicking strategies has potential to
improve the regenerative capacity of encapsulated cells and lead to better clinical outcome. Here,
we developed a double-modified, biomimetic and tissue adhesive hydrogel for cartilage
engineering. We demonstrated sequential modification of alginate with first sulfate moieties to
mimic the high glycosaminoglycan content of native cartilage and then tyramine moieties to allow
in situ enzymatic crosslinking with tyrosinase under physiological conditions.
Tyrosinase-crosslinked alginate sulfate tyramine (ASTA) hydrogels showed strong adhesion to
native cartilage tissue with higher bond strength compared to alginate tyramine (AlgTA). Both
ASTA and AlgTA hydrogels supported the viability of encapsulated bovine chondrocytes and
induced a strong increase in the expression of chondrogenic genes such as collagen 2, aggrecan and
Sox9. Aggrecan and Sox9 gene expression of chondrocytes in ASTA hydrogels were significantly
higher than those in AlgTA. Chondrocytes in both ASTA and AlgTA hydrogels showed potent
deposition of cartilage matrix components collagen 2 and aggrecan after 3 weeks of culture whereas
a decreased collagen 1 deposition was observed in the sulfated hydrogels. ASTA and AlgTA
hydrogels with encapsulated human chondrocytes showed in vivo stability as well as cartilage
matrix deposition upon subcutaneous implantation into mice for 4 weeks. Our data is the first
demonstration of a double-modified alginate with sulfation and tyramination that allows in situ
enzymatic crosslinking, strong adhesion to native cartilage and chondrogenic re-differentiation.
important roles in the signaling and phenotype of resident chondrocytes. Recapitulating the key
ECM components within engineered tissues through biomimicking strategies has potential to
improve the regenerative capacity of encapsulated cells and lead to better clinical outcome. Here,
we developed a double-modified, biomimetic and tissue adhesive hydrogel for cartilage
engineering. We demonstrated sequential modification of alginate with first sulfate moieties to
mimic the high glycosaminoglycan content of native cartilage and then tyramine moieties to allow
in situ enzymatic crosslinking with tyrosinase under physiological conditions.
Tyrosinase-crosslinked alginate sulfate tyramine (ASTA) hydrogels showed strong adhesion to
native cartilage tissue with higher bond strength compared to alginate tyramine (AlgTA). Both
ASTA and AlgTA hydrogels supported the viability of encapsulated bovine chondrocytes and
induced a strong increase in the expression of chondrogenic genes such as collagen 2, aggrecan and
Sox9. Aggrecan and Sox9 gene expression of chondrocytes in ASTA hydrogels were significantly
higher than those in AlgTA. Chondrocytes in both ASTA and AlgTA hydrogels showed potent
deposition of cartilage matrix components collagen 2 and aggrecan after 3 weeks of culture whereas
a decreased collagen 1 deposition was observed in the sulfated hydrogels. ASTA and AlgTA
hydrogels with encapsulated human chondrocytes showed in vivo stability as well as cartilage
matrix deposition upon subcutaneous implantation into mice for 4 weeks. Our data is the first
demonstration of a double-modified alginate with sulfation and tyramination that allows in situ
enzymatic crosslinking, strong adhesion to native cartilage and chondrogenic re-differentiation.