Spleen Organoid Units Generate Functional Human and Mouse Tissue-Engineered Spleen in a Murine Model

Introduction: Splenectomy is common after trauma or hematologic disease, and alters immune protection against pathogens, which may lead to fulminant infection with high mortality. Yet the spleen has demonstrable regenerative capacity and cells might be recovered and reimplanted at the time of injury or excision to avoid these risks. Methods: Tissue-engineered spleen (TESp) was generated from Actin^GFP mice (mTESp) or human donor spleen (hTESp) through implantation of spleen organoid units (spleen OU), in NOD/SCID mice with concurrent splenectomy, on a biodegradable scaffold. Explants were evaluated and blood smears were obtained to investigate the presence of target cells or Howell-Jolly bodies, which are erythrocyte sequelae of asplenia. Results: TESp was generated from mouse (mTESp) and human (hTESp) donor cells with essential splenic components: red and white pulp with trabeculae. mTESp and hTESp demonstrated green fluorescent protein- or lamin-positive costaining with proliferating cell nuclear antigen, CD4, and CD11c, identifying proliferative donor cells and key immune components of the spleen of donor origin. Animals with hTESp and mTESP combined with splenectomy had significantly fewer Howell-Jolly bodies on blood smears than controls. Conclusion: TESp from mouse and human donor cells can be generated by 4 weeks and contains donor immune cells identified by CD4 and CD11c. TESp reduces postsplenectomy erythrocyte inclusions, indicating possible function. Impact Statement Overwhelming postsplenectomy infection is rare but highly mortal. Tissue-engineered spleen (TESp) was generated from murine (mTESp) and human (hTESp) donors and appeared histologically similar to native spleen. Both mTESp and hTESp demonstrated proliferative cells of donor spleen origin. Importantly, functional cells were demonstrated on imaging with a corresponding reduction in the number of erythrocyte inclusions in blood smears that are typically identified in patients with asplenia and indicate a lack of clearance by functional spleen tissue. Taken together, these findings indicate that this approach might be clinically relevant as a future human therapy.