Homogeneously crosslinked in situ hydrogel enclosing high-density human-cancer cells promotes vascularized in vivo tumor modeling for immune cell therapy

Cancer models in animal studies play a central role in cancer research, particularly in investigating vascularized tumor tissues for the validation of immune cell therapies. However, xenografts relying solely on cancer cells are ineffective for optimal tumor tissue formation. Additionally, tumor modeling using hydrogels with cancer cells to promote vascularization often leaves behind residual biomaterials that inhibit integration with surrounding tissues. To address these issues, we utilized a straightforward in vivo vascularized tumor modeling method with a completely degradable, crosslinker-free carboxymethyl chitosan (CMCTS)/oxidized hyaluronic acid (OHA) hydrogel that encapsulates high-density human cancer cells for in situ injection. The CMCTS/oHA hydrogel was fully degraded within 3 weeks, enabling three-dimensional (3D) cell condensation in vitro. 2 weeks after subcutaneous injection in mice, solid tumors formed, with native host vasculature infiltrating the transplanted human cancer cells, confirming spontaneous hydrogel degradation. Following this, human macrophages were administered via tail vein injection, enhancing the accumulation of mouse immune cells in the humanized tumor twofold and showing murine macrophages adjacent to the vasculature. This study thus provides proof-of-concept for a facile and fully vascularized humanized tumor model in mice for validating immune cell therapies. HIGHLIGHTSO_LIThe oHA was prepared using sodium periodate treatment, which facilitated the formation of in situ CMCTS/oHA hydrogels C_LIO_LICMCTS/oHA hydrogels completely degraded within a short period, allowing for 3D cell condensation C_LIO_LIHigh-density cell-laden CMCTS/oHA hydrogels were injected subcutaneously in mice, resulting in the generation of a vascularized solid tumor C_LIO_LIThe transplanted therapeutic cell was observed to adhere to the tumor tissue through the bloodstream C_LI