As observed in mitral stenosis, mitral insufficiency (regurgitation), aortic stenosis, aortic insufficiency, tricuspid insufficiency and like valvular heart diseases, when a heart valve does not properly function and stenosis or regurgitation occurs, the heart valve must be replaced. There are three kinds of heart valves which are currently used in heart transplant operations: (1) mechanical valves, (2) heterograft valves and (3) homograft valves. 
Mechanical valves have excellent durability; however, they require recipients to take an anticoagulant throughout their lifetime. Heterograft valves, which use valves from animals, do not require recipients to take an anticoagulant throughout their lifetime; however, the valves tend to malfunction after 6 to 10 years. Alternatively, frozen homograft valves harvested from cadavers exhibit more favorable long term results than heterograft valves. Therefore, the frozen homograft valves are widely used in Europe and America where use of  cadaver tissue is advanced; however, the drawback of short supply exists. 
A method for regenerating various kinds of tissues in a living body by employing tissue engineering techniques has recently been developed, wherein cells of autogenous tissue are seeded and cultured on a scaffold made of a bioabsorbable polymer so as to regenerate the autogenous tissues. Quite a few research reports have been published on the tissue regeneration method applied to skin regeneration (M. L. Cooper, L. F. Hansbrough, R. L. Spielvogel et al. “In vivo optimization of a living dermal substitute employing cultured human fibroblasts on a biodegradable polyglycolic acid or polyglactin mesh.” Biomaterials 12 (1991): 243–248) and cartilage regeneration (C. A. Vacanti, R. Langer et al. “Synthetic polymers seeded with chondrocytes provide a template for new cartilage formation.” Plast. Reconstr. Surg. 88 (1991): 753–759). 
Regeneration of heart valves has also been tested using tissue engineering techniques and a study regarding regeneration of heart valve leaflets has reported good results (T. Shin'oka et. al. “Tissue-engineered heart valve leaflets. Autologous valve leaflet replacement study in a lamb model.” Circulation 94 (suppl. II) (1996): II-164-II-168. T. Shin'oka et al. “Tissue-engineered heart valve leaflets. Does cell origin affect  outcome?” Circulation 96 (suppl. II) (1996): II-102-II-107). 
However, practically usable bioabsorbable substrates which enable the entire heart valve to be made of bioabsorbable material have not yet been developed. 
An object of the present invention is to provide a practically usable bioabsorbable substrate which enables the entire heart valve to be made of bioabsorbable material. 