IN SITU EXPANSION OF ENGINEERED DEVICES FOR REGENERATION

1 .- 40 . (canceled)

41 . A method of in situ expansion of engineered tissue in a host, the method comprising implanting an engineered tissue seed into the host, wherein the engineered tissue seed was produced by:

(a) providing a co-culture comprising a first population of cells comprising human hepatocytes and a second population of cells comprising human fibroblasts, thereby forming one or more hepatocyte aggregates, wherein the one or more hepatocyte aggregates is in a first biocompatible scaffold;

(b) providing one or more human endothelial cell cords, wherein the one or more human endothelial cell cords is in a second biocompatible scaffold; and

(c) combining the one or more hepatocyte aggregates in the first biocompatible scaffold with the one or more human endothelial cell cords in the second biocompatible hydrogel scaffold, wherein the first and second biocompatible scaffolds are the same or different, thereby forming an engineered tissue seed suitable for implantation in a host,

wherein following implantation the human hepatocytes in the engineered tissue seed expand in the host.

42 . The method of claim 41 , wherein the engineered tissue seed expands 11-fold following implantation.

43 . (canceled)

44 . The method of claim 41 , wherein the engineered tissue seed expands 50-fold following implantation.

45 .- 60 . (canceled)

61 . The method of claim 41 , wherein the first and second biocompatible scaffolds are the same.

62 . The method of claim 41 , wherein the first and second biocompatible scaffolds are different.

63 . The method of claim 41 , wherein the first biocompatible scaffold comprises collagen.

64 . The method of claim 41 , wherein the second biocompatible scaffold comprises fibrin.

65 . The method of claim 41 , wherein the first biocompatible scaffold comprises collagen and the second biocompatible scaffold comprises fibrin.