Urinary bladder matrix (UBM) is one of the most studied extracellular matrixes (ECM) in the tissue engineering field. Although almost all of the UBM hydrogels were prepared by using peracetic acid (PAA), recent studies indicated that PAA was not a trustworthy way to decellularize UBM. A stronger detergent, such as sodium dodecyl sulfate (SDS), may help tackle this issue; however, its effects on the hydrogels’ characteristics remain unknown. Therefore, the objective of this study was to develop a more reliable protocol to decellularize UBM, using SDS, and to compare the characteristics of hydrogels obtained from this method to the widely employed technique, using PAA. The results indicated that SDS was superior to PAA in decellularization efficacy. Different decellularization methods led to dissimilar gelation kinetics; however, the methods did not affect other hydrogel characteristics in terms of biochemical composition, surface morphology and rheological properties. The SDS-treated hydrogels possessed excellent cytocompatibility in vitro. These results showed that the SDS decellularization method could offer a more stable and safer way to obtain acellular UBM, due to reducing immunogenicity. The hydrogels prepared from this technique had comparable characteristics as those from PAA and could be a potential candidate as a scaffold for tissue remodeling.

Porcine urinary bladder is one of the most used organs to fabricate extracellular matrix (ECM) hydrogel. Although there are two different ECM types inside a bladder, i.e., urinary bladder matrix (UBM) and a subtype ECM (sECM), most studies have only employed UBM for hydrogel fabrication, and overlooked the potential use of sECM. In another aspect, the delamination of UBM from bladders is a time-consuming process; consequently, the use of the whole bladder (WB) will likely increase production yield. Therefore, the objective of this study was to fabricate hydrogels from sECM and WB and compare them to UBM. The results indicated that different layers of the bladder shared almost the same biochemical composition. In terms of gelation kinetics, rheology and morphology, although hydrogels from UBM and sECM exhibited some discrepancies, those from UBM and WB interestingly possessed almost the same characteristics. In in vitro studies, all the hydrogels possessed nearly the same biochemical effects towards L929 viability and C2C12 differentiation. These results could preliminarily indicate that the use of sECM should no longer be ignored, and WB could be a promising substitution for UBM hydrogels, eliminating the need for time-consuming delamination processes, as well as increasing the possibility of mass production.

Mesenchymal stem cells (MSCs) possess immunomodulatory properties and capacity for endogenous regeneration. Therefore, MSC therapy is a promising treatment strategy for COVID-19. However, the cells cannot stay in the lung long enough to exert their function. The extracellular matrix from porcine bladders (B-ECM) has been shown not only to regulate cellular activities but also to possess immunoregulatory characteristics. Therefore, it can be hypothesized that B-ECM hydrogel could be an excellent scaffold for MSCs to grow and could anchor MSCs long enough in the lung so that they can exhibit their immunomodulatory functions. In this study, ECM degradation products and a co-culture system of MSCs and macrophages were developed to study the immunomodulatory properties of ECM and MSCs under septic conditions. The results showed that B-ECM degradation products could decrease pro-inflammatory and increase anti-inflammatory cytokines from macrophages. In an in vivo mimicking co-culture system, MSCs cultured on B-ECM hydrogel exhibited immunomodulatory properties at both gene and protein levels. Both B-ECM degradation products and MSC conditioned medium supported the wound healing of alveolar epithelial cells. The results from the study could offer a basis for investigation of immunomodulation by ECM and MSCs before conducting in vivo experiments, which could later be applied in regenerative medicine.