There is still need for development of biomimetic hydrogels capable to recapitulate the native environment of bone tissue, as those used currently lack of tissue-specific composition and yield suboptimal tissue formation. Decellularized extracellular matrix (dECM) is composed of tissue-specific biopolymers and growth factors. Moreover, it undergoes gelation at physiological temperatures. Therefore, it is a very promising material for development of injectable hydrogels.
The goal of this study was to develop injectable hydrogels containing solubilized dECM isolated from porcine bone (bdECM).
Porcine tibia was demineralized using hydrochloric acid (at room temperature (RT) and 4 °C) and decellularized by means of either Triton X-100 (at RT and 4 °C) or trypsin (at 37 °C). The concentration of DNA, GAGs and collagen was studied after hydrolysis of the freeze-dried bdECM powder. Additionally, content of BMP2 and VEGF was determined by ELISA after extraction with guanidine hydrochloride. The obtained bdECM powder was dissolved by pepsin digestion at concentration of 10, 20 and 30 mg/ml and rheological, gelling and mechanical properties of the solutions and the corresponding hydrogels were studied using rheometer. The biological evaluation was performed with human mesenchymal stem cells (hMSC) and pepsin-digested type I collagen hydrogels used as a reference biomaterial.
The biochemical analysis revealed that the composition of bdECM varied depending on the demineralization and decellularization temperatures, with demineralization carried out at RT and decellularization at 4 °C yielding the lowest DNA content. Rheological tests showed concentration-dependent increase in dynamic viscosity and shear thinning behavior of all pre-gel solutions. The sol-gel transition took approximately 10 mins after incubation at 37 °C. Moreover, we observed inversion of the viscoelastic properties from viscous to elastic with increasing concentration of dECM. The ability of hydrogels to support hMSC proliferation and osteogenic differentiation was confirmed by means of MTS, DNA and ALP activity assays.