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 in the shape of a heart valve or blood vessel or heart valve leaflet comprising implanting into an animal at a first site a cell-matrix construct comprising
 (a) a fibrous matrix formed in the shape of a heart valve or heart value leaflet, wherein the matrix consists of a synthetic, biocompatible, chemically biodegradable polymer, and  
 (b) having seeded therein a mixture of cells selected from the group selected from consisting of endothelial cells, myofibroblasts, skeletal muscle cells, vascular smooth muscle cells, myocytes, fibromyoblasts, and ectodermal cells, seeded thereon, 
 wherein the synthetic chemically biodegradable polymer provides the biochemical properties of a heart valve or leaflet until the seeded cells can lay down their own extracellular matrix, and  
 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 neededthe matrix is formed so that the cells attach to and proliferate on it to the edges of the matrix. 
 
     
     
       2. The method of  claim 1  further comprising seeding wherein the matrix is seeded 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 transplanted to a second site. 
     
     
       4. The method of  claim 1  wherein the matrix is in the form of a heart valve and is implanted in the heart leaflet. 
     
     
       5. The method of  claim 1  wherein the cell-matrix construct is seeded with vascular smooth muscle cells and endothelial cells is and implanted to form a heart 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. The method of claim 1 wherein the cell-matrix construct is formed of a potymer 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. 
     
     
       9. The method of claim 1 wherein the cell-matrix construct contains interconnected pores in the range of between approximately 100 and 300 microns. 
     
     
       10. The method of claim 1 wherein the cell-matrix construct includes growth factors. 
     
     
       11. The method of claim 10 wherein the growth factors are selected from the group consistin of heparin binding growth factor (hbgf), transforming growth factor alpha or beta (TGFβ), alpha fibroblastic growt.h...factor (FGF),.epidermal growth factor (TGF), vascular endothelium growth factor (VEGF), insulin, glucagon, estrogen, nerve growth factor (NGF) and muscle morphogenic factor (MMP). 
     
     
       12. The method of claim 1 wherein the cell-matrix further comprises bioactive factors incorporated to between one and 30% by weight. 
     
     
       13. The method of claim 1 wherein the cell-matrix is first cultured in a bioreactor to form a fibrous tissue-polymeric construct before implantation. 
     
     
       14. The method of claim 13 wherein the bioreactor is an animal.