Engineered biological nerve graft, fabrication and application thereof
An engineered three-dimensional structure includes living cells cohered with each other. The living cells suitably include Schwann cells and at least one other type of cell. The cells accompanying the Schwann cells can suitably be bone marrow stem cells or another type of cell having one or more anti-inflammatory properties. The structure is suitably a graft that facilitates restorative axon growth when the graft is implanted between the proximal and distal stubs of a severed nerve in a living organism. The graft can optionally include a plurality of acellular conduits extending between opposite axial ends of the graft. Bio-printing techniques can be used to assemble a three-dimensional construct that becomes through maturation an axon-guiding graft, by stacking a plurality of multicellular bodies, each of which includes a plurality of living cells cohered to one another to sufficiently to avoid collapsing when the multicellular bodies are stacked to form the structure.
1. A multicellular construct consisting essentially of: a multicellular region comprising:
a plurality of living cells cohered to one another to form an elongate graft for restoring neural connection between the ends of a severed nerve;
a plurality of acellular channels extending axially through the multicellular region;
and wherein the multicellular construct does not comprise any scaffold material at the time of implantation into a living organism having a nervous system.
2. The multicellular construct of claim 1 wherein the acellular channels are hollow or filled with one or more acellular materials.
3. The multicellular construct of claim 1 wherein the acellular channels are hollow, partially filled with one or more acellular materials, fully filled with one or more acellular materials, or any combination thereof.
4. The multicellular construct of claim 1 wherein the living cells comprise Schwann cells.
5. The multicellular construct of claim 4 wherein between about 0.1 and about 20 percent of the total number of living cells in the multicellular region are Schwann cells.
6. The multicellular construct of claim 5 wherein between 1 percent to about 10 percent of the total number of living cells in the multicellular region are Schwann cells.
7. The multicellular construct of claim 6 wherein between about 5 percent to about 10 percent of the total number of living cells in the multicellular region are Schwann cells.
8. The multicellular construct of claim 4 wherein the graft has a central portion and a peripheral portion surrounding the central portion, the percentage of cells in the central portion that are Schwann cells being higher than the percentage of cells in the peripheral portion that are Schwann cells.
9. The multicellular construct of claim 1 wherein the number of acellular channels is in the range of two to five.
10. The multicellular construct of claim 1 wherein the graft is tubular.
11. The multicellular construct of claim 1 wherein the graft is an engineered tissue.
12. The multicellular construct of claim 1 wherein the graft is non-innervated.
13. The multicellular construct of claim 1 wherein the graft comprises tissue culture medium.
14. An elongate three-dimensional structure comprising:
a plurality of engineered multicellular bodies, each multicellular body comprising a plurality of living cells cohered to one another; and
a plurality of discrete filler bodies, each filler body comprising a biocompatible material that resists migration and ingrowth of cells from the multicellular bodies into the filler bodies,
wherein the multicellular bodies are arranged in a pattern in which each multicellular body contacts at least one other multicellular body and the filler bodies are positioned and arranged to form a plurality of acellular channels extending between opposite ends of the structure.
15. The multicellular construct of claim 1 wherein the acellular channels are hollow.
16. The elongate three-dimensional structure of claim 14 wherein the acellular channels have a side-by-side orientation to one another and are separated from one another by the multicellular bodies.
17. The elongate three-dimensional structure of claim 14 wherein there are at least three acellular channels extending between the opposite ends of the structure.
18. The elongate three-dimensional structure of claim 14 wherein the plurality of living cells comprises Schwann cells.
19. The elongate three-dimensional structure of claim 14 wherein at least some of the multicellular bodies or some of the filler bodies are substantially rod shaped.
20. The elongate three-dimensional structure of claim 14 wherein at least some of the multicellular bodies or some of the filler bodies are substantially spherical.
21. The multicellular construct of claim 1 for restoring nerve function by promoting regenerative axon growth through the graft when the graft is implanted in a living organism having a nervous system and positioned in a gap between the ends of a severed nerve, wherein the plurality of acellular channels extends between opposite ends of the multicellular region.
22. The multicellular construct of claim 21 wherein the acellular channels are hollow, partially filled with one or more acellular materials, fully filled with one or more acellular materials, or any combination thereof.
23. The multicellular construct of claim 21 wherein the living cells comprise Schwann cells.
24. The multicellular construct of claim 1 , wherein the plurality of acellular channels extends axially through the interior of the multicellular region.
25. A multicellular construct as recited in claim 21 , wherein the multicellular construct is an engineered tissue.
26. A multicellular construct as recited in claim 21 wherein the acellular channels have a side-by-side orientation to one another and are separated from one another by living cells in the multicellular construct.