Engineering of strong, pliable tissues

Abstract

It has been discovered that improved yields of engineered tissue following implantation, and engineered tissue having enhanced mechanical strength and flexibility or pliability, can be obtained by implantation, preferably subcutaneously, of a fibrous polymeric matrix for a period of time sufficient to obtain ingrowth of fibrous tissue and/or blood vessels, which is the removed for subsequent implantation at the site where the implant is desired. The matrix is optionally seeded prior to the first implantation, after ingrowth of the fibrous tissue, or at the time of reimplantation. The time required for fibrous ingrowth typically ranges from days to weeks. The method is particularly useful in making valves and tubular structures, especially heart valves and blood vessels.

1. A method for making a cell-matrix construct for use as a heart valve or blood vessel comprising
 implanting into an animal at a first site a fibrous matrix formed of a synthetic biodegradable polymer having seeded therein a mixture of cells selected from the group selected from endothelial cells, myofibroblasts, skeletal muscle cells, vascular smooth muscle cells, myocytes, fibromyoblasts, and ectodermal cells, wherein the matrix is formed of a biocompatible, biodegradable polymer, and   implanting into an animal or human the matrix at a site where the resulting cell-construct is needed.   
     
     
       2. The method of  claim 1  further comprising seeding the matrix with dissociated parenchymal or connective tissue cells. 
     
     
       3. The method of  claim 1  wherein the matrix is first cultured at a first site in a patient prior to being implanted at a second site. 
     
     
       4. The method of  claim 1  wherein the matrix is a heart valve and is implanted in the heart. 
     
     
       5. The method of  claim 1  wherein the cell-matrix construct is seeded with vascular smooth muscle cells and endothelial cells is implanted to form a valve. 
     
     
       6. The method of  claim 5  wherein the valve is a heart valve. 
     
     
       7. The method of  claim 1  wherein the cell-matrix construct is seeded with endothelial cells and implanted to form a blood vessel. 
     
     
       8. A cell-matrix construct for use as a heart valve or heart valve leaflet construct consisting of
 (a) a fibrous polymeric matrix consisting of a synthetic, biocompatible, chemically biodegradable polymer in the shape of a heart valve or heart valve leaflet,   (b) cells selected from the group consisting of endothelial cells, myofibroblasts, skeletal muscle cells, vascular smooth muscle cells, myocytes, fibromyoblasts, and ectodermal cells,   wherein the synthetic, biocompatible chemically biodegradable polymer provides the biomechanical properties of a heart valve or leaflet until the seeded cells can lay down their own extracellular matrix, and   the matrix is formed so that the cells can attach to and proliferate in a three dimensional space, to the edges of the matrix.   
     
     
       9. The cell-matrix construct of claim 8 comprising myofibroblasts grown to confluence and then endothelial cells seeded thereon. 
     
     
       10. The cell-matrix construct of claim 8 wherein the cell-matrix construct can withstand repeated stress and strain. 
     
     
       11. The cell-matrix construct of claim 8 wherein the cell-matrix construct is formed of a polymer selected from the group consisting of poly(lactide) (PLA), poly(glycolic acid) (PGA), poly(lactide-co-glycolide) (PLGA), poly(caprolactone), polyanhydrides, polyamino acids, and polyortho esters. 
     
     
       12. The cell-matrix construct of claim 8 wherein the cell-matrix construct contains interconnected pores in the range of between approximately 100 and 300 microns. 
     
     
       13. The cell-matrix construct of claim 8 wherein the cell-matrix construct includes growth factors. 
     
     
       14. The cell-matrix construct of claim 13 wherein the growth factors are selected from the group consisting of heparin binding growth factor (hbgf), transforming growth factor alpha or beta (TGFβ), alpha fibroblastic growth factor (FGF), epidermal growth factor (TGF), vascular endothelium growth factor (VEGF), insulin, glucagon, estrogen, nerve growth factor (NGF) and muscle morphogenic factor (MMP). 
     
     
       15. The cell-matrix construct of claim 8 wherein the cell-matrix further comprises bioactive factors incorporated to between one and 30% by weight. 
     
     
       16. The cell-matrix construct of claim 8 wherein the cell-matrix is first cultured in a bioreactor to form a fibrous tissue-polymeric construct before implantation. 
     
     
       17. The cell-matrix construct of claim 16 wherein the bioreactor is an animal. 
     
     
       18. A cell-matrix construct for implantation comprising a fibrous matrix formed of a synthetic biodegradable polymer having seeded therein a mixture of cells selected from the group consisting of endothelial cells, myofibroblasts, skeletal muscle cells, vascular smooth muscle cells, myocytes, fibromyoblasts, and ectodermal cells, wherein the matrix incorporates one or more struts or support members, cultured in vivo to form tissue, for implantation into a second second site in an animal or human.