Composite scaffolds and methods using same for generating complex tissue grafts

Abstract

A composite scaffold for engineering a heterogeneous tissue is provided. The composite scaffold includes: (a) a first scaffold being capable of supporting, formation of a first tissue type thereupon; and (b) a second scaffold being capable of supporting formation of a second tissue type thereupon; wherein the first scaffold and the second scaffold are arranged with respect to each other such that when the first scaffold supports the first tissue type and the second scaffold supports the second tissue type, a distance between any cell of the second tissue type and the first tissue type does not exceed 200 $G(m)m.

What is claimed is:  
     
         1 . A composite scaffold for engineering a heterogeneous issue, the composite scaffold comprising: 
 (a) a first scaffold being capable of supporting formation of a first tissue type thereupon; and    (b) a second scaffold being capable of supporting formation of a second tissue type thereupon;    wherein said first scaffold and said second scaffold are arranged with respect to each other such that when said first scaffold supports said first tissue type and said second scaffold supports said second tissue type, a distance between any cell of said second tissue type and said first tissue type does not exceed 200 μm.    
     
     
         2 . An engineered tissue graft generated using the composite scaffold of  claim 1 .  
     
     
         3 . The composite scaffold of  claim 1 , wherein said first scaffold is a filamentous scaffold composed of filaments having a diameter selected from a range of 4-500 μm.  
     
     
         4 . The composite scaffold of  claim 1 , wherein said second scaffold is a porous continuous scaffold.  
     
     
         5 . The composite scaffold of  claim 1 , wherein said first scaffold and/or second scaffold are degradable upon exposure to predetermined environmental conditions.  
     
     
         6 . The composite scaffold of  claim 5 , wherein said predetermined environmental conditions are selected from the group consisting of presence of hydrolytic enzymes, presence of proteasomal enzymes, presence of pH lower than 5 and presence of reducing conditions,  
     
     
         7 . The composite scaffold of  claim 1 , wherein said first scaffold is selected so as to enable said first tissue type to form in substantially tubular structures thereupon.  
     
     
         8 . The composite scaffold of  claim 1 , wherein said first tissue type is vascular tissue.  
     
     
         9 . The composite scaffold of  claim 1 , wherein said second tissue type is structural tissue selected from the group consisting of bone tissue, cartilage tissue, adipose tissue, connective tissue and muscle tissue.  
     
     
         10 . The composite scaffold of  claim 1 , wherein said first scaffold and/or said second scaffold further include a bioactive agent associated therewith.  
     
     
         11 . The composite scaffold of  claim 10 , wherein said bioactive agent is selected from the group consisting of a cell proliferation factor, a cell differentiation factor, a cell attracting factor and a pharmacologically active factor.  
     
     
         12 . The composite scaffold of  claim 1 , wherein said first scaffold is selected so as to enable colonization and/or proliferation of at least one cell type composing said first tissue type.  
     
     
         13 . The composite scaffold of  claim 1 , wherein said second scaffold is selected so as to enable-colonization and/or proliferation of at least one cell type composing said second tissue type.  
     
     
         14 . A composition of matter comprising: 
 (a) a linker molecule attached to a first polymer backbone; and    (b) a stereoisomer of said linker molecule attached to a second polymer backbone;    wherein when exposed to polymerizing conditions said first and said second polymer backbones cross-link with at least one molecule of said first and/or said second polymer backbones via at least one of said linker molecule and said stereoisomer of said linker molecule to thereby form a scaffold structure.    
     
     
         15 . The composition of matter of  claim 14 , wherein said linker molecule is a co-polymer of lactic acid.  
     
     
         16 . The composition of matter of  claim 14 , wherein said polymer backbone is a hydrophilic polymer.  
     
     
         17 . The composition of matter of  claim 16 , wherein said hydrophilic polymer is selected from the group consisting of a natural polysaccharide, a protein, an ethylene glycol based polymer and a propylene glycol based polymer.  
     
     
         18 . The composition of matter of  claim 14 , wherein said first polymer backbone is identical to said second polymer backbone.  
     
     
         19 . The composition of matter of  claim 14 , wherein said scaffold structure is three dimensional.  
     
     
         20 . A composition of matter comprising a polymer backbone attached to: 
 (a) a linker molecule; and    (b) a stereoisomer of said linker molecule;    wherein when exposed to polymerizing conditions said polymer backbone cross links with at least an additional polymer backbone via at least one of said linker molecule and said stereoisomer of said linker molecule, to thereby form a scaffold structure.    
     
     
         21 . The composition of matter of  claim 20 , wherein said linker molecule is a co-polymer of lactic acid.  
     
     
         22 . The composition of matter, of  claim 20 , wherein said polymer backbone is a hydrophilic polymer.  
     
     
         23 . The composition of matter of  claim 22 , wherein said hydrophilic polymer is selected from the group consisting of a natural polysaccharide, a protein, an ethyrene glycol based polymer and a propylene glycol based polymer.  
     
     
         24 . The composition of matter of  claim 22 , wherein said scaffold structure is three dimensional.  
     
     
         25 . A scaffold comprising a plurality of molecules of a polymeric backbone cross-linked therebetween via L and D stereoisomers of a linker molecule.  
     
     
         26 . The scaffold of  claim 25 , wherein said plurality of molecules of said polymeric backbone are hydrophilic polymers.  
     
     
         27 . The scaffold of  claim 26 , wherein said hydrophilic polymers are selected from the group consisting of natural polysaccharides, proteins, ethylene glycol based polymers and a propylene glycol based polymers.  
     
     
         28 . The scaffold of  claim 25 , wherein said linker molecule is a co-polymer of lactic acid.  
     
     
         29 . The scaffold of  claim 25 , further comprising a bioactive agent.  
     
     
         30 . The scaffold of  claim 29 , wherein said bioactive agent is selected from the group consisting of a cell proliferation factor, a cell differentiation factor, a cell attracting factor and a pharmacologically active factor.  
     
     
         31 . A scaffold capable of releasing a bioactive agent, the scaffold comprising a polymeric backbone and the bioactive agent, wherein said polymeric backbone is selected such that exposure thereof to predetermined environmental conditions leads to release of the bioactive agent from the scaffold.  
     
     
         32 . The scaffold of  claim 31 , wherein the bioactive agent is selected from the group consisting of a cell proliferating factor, a cell differentiating factor, a cell attracting factor and a pharmacologically active factor.  
     
     
         33 . The scaffold of  claim 31 , wherein said polymeric backbone is selected from the group consisting of cellulose, hydroxyl alkyl acid polyester, polyphosphazene, polycarbonate, lactide acid and glycolide acid.  
     
     
         34 . The scaffold of  claim 31 , wherein the bioactive agent is incorporated within said polymeric backbone, and whereas the bioactive agent is released following degradation and/or disintegration of said polymeric backbone in said environmental conditions.  
     
     
         35 . The scaffold of claim.  31 , wherein the bioactive agent is a negatively charged bioactive agent, and whereas said negatively charged bioactive agent is incorporated within pre-cationized regions of said polymeric backbone.  
     
     
         36 . The scaffold of  claim 31 , wherein said polymeric backbone is designed and constructed so as to enable timed release of the bioactive agent from the scaffold.  
     
     
         37 . The scaffold of  claim 31 , wherein said predetermined environmental conditions are selected from the group consisting of presence of hydrolytic enzymes, presence of proteasomal enzymes, presence of pH lower than 5 and presence of reducing conditions,  
     
     
         38 . A scaffold comprising a filamentous polymer including: 
 (a) a hydrophilic molecule being capable of promoting degradation of said filamentous polymer when exposed to predetermined environmental conditions;    (b) a plasticizing agent being capable of rendering said filamentous polymer flexible; and    (c) a co-polymeric stereocomplex being capable of cross linking said filamentous polymer with at least one additional filamentous polymer to thereby form the scaffold.    
     
     
         39 . The scaffold of  claim 38 , wherein said filamentous polymer has a diameter selected from a range of 4-500 μm.  
     
     
         40 . The scaffold of  claim 38 , wherein said filamentous polymer is designed and configured for supporting formation of a tube shaped tissue structure thereupon  
     
     
         41 . The scaffold of  claim 38 , wherein said filamentous polymer is selected from the group consisting of hydroxyl alklyl acid polyester, polyphosphazene, poly carbonate and poly phosphate ester.  
     
     
         42 . The scaffold of  claim 38 , wherein said filamentous polymer is degradable upon exposure to predetermined environmental conditions.  
     
     
         43 . The scaffold of  claim 42 , wherein said predetermined environmental conditions are selected from the group consisting of presence of hydrolytic enzymes, presence of proteasomal enzymes, pH lower than 5 and reducing conditions.  
     
     
         44 . The scaffold of  claim 40 , wherein said tube shaped tissue is vascular tissue.  
     
     
         45 . The scaffold of  claim 38 , wherein said hydrophilic molecule is poly ethylene glycol and poly ethylene propylene glycol.  
     
     
         46 . The scaffold of  claim 38 , wherein said plasticizing agent is selected from the group consisting of a tributyl citrate, a tributyl citrate acetate, a phospholipids and an oleate ester.  
     
     
         47 . The scaffold of  claim 38 , wherein said co-polymeric stereocomplex includes lactide acid stereoisomers.  
     
     
         48 . The scaffold of  claim 38 , further comprising a bioactive agent associated therewith.  
     
     
         49 . The scaffold of  claim 48 , wherein said bioactive agent is selected from the group consisting of a cell proliferation factor, a cell differentiation factor, a cell attracting factor and a pharmacologically active factor.  
     
     
         50 . A method of inducing the formation of a heterogeneous tissue, the method comprising: 
 (a) providing a first scaffold being capable of supporting formation of a first tissue type thereupon;    (b) providing a second scaffold being capable of supporting formation of a second tissue type thereupon;    (c) embedding said first scaffold in said second scaffold thereby forming a composite scaffold; and    (d) implanting said composite scaffold in an individual;    
     
     
         51 . The method of  claim 50 , wherein said step of embedding is effected such that when said first scaffold supports said first tissue type and said second scaffold supports said second tissue type, a distance between any cell of said second tissue type and said first tissue type does not exceed 200 μm.  
     
     
         52 . The method of  claim 50 , wherein said first scaffold is a filamentous scaffold having a diameter not exceeding 0.5 mm.  
     
     
         53 . The method of  claim 50 , wherein said second scaffold is a porous continuous scaffold.  
     
     
         54 . The method of  claim 52 , wherein said filamentous scaffold is selected so as to enable said first tissue type to form substantially tubular structures thereupon.  
     
     
         55 . The method of  claim 50 , wherein said first tissue type is vascular tissue.  
     
     
         56 . The method of  claim 50 , wherein said second tissue type is structural tissue selected from the group consisting of bone tissue, cartilage tissue, adipose tissue, connective tissue and muscle tissue.  
     
     
         57 . The method of  claim 50 , wherein said first scaffold and/or said second scaffold further include a bioactive agent associated therewith.  
     
     
         58 . The method of  claim 50 , wherein said bioactive agent is selected from the group consisting of a cell proliferation factor, a cell differentiation factor, a cell attracting factor and a pharmacologically active factor.  
     
     
         59 . The method of  claim 50 , further comprising the step of growing said first tissue type on said first scaffold and/or growing said second tissue type on said second scaffold prior to step (c).  
     
     
         60 . The method of  claim 50 , further comprising growing said second tissue type on said second scaffold prior to step (c) or step (d).  
     
     
         61 . The method of  claim 50 , wherein said first scaffold is selected so as to enable colonization and/or proliferation of at least one cell type composing said first tissue type.  
     
     
         62 . The method of  claim 50 , wherein said second scaffold is selected so as to enable colonization and/or proliferation of at least one cell type composing said second tissue type.  
     
     
         63 . The method of  claim 59 , wherein said first scaffold and/or second scaffold are degradable upon exposure to predetermined environmental conditions.  
     
     
         64 . The method of  claim 50 , wherein said predetermined environmental conditions are selected from the group consisting of presence of hydrolytic enzymes, presence of proteasomal enzymes, pH lower than 5 and reducing conditions.