Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Reexamination Certificate
1998-07-02
2003-03-25
Naff, David M. (Department: 1651)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
C424S093700, C424S422000, C424S548000, C424S569000, C424S572000, C435S325000, C435S363000, C435S366000, C435S377000, C435S395000
Reexamination Certificate
active
06537567
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed generally to the art of tissue engineering, or the production of organized mammalian tissues in vitro.
BACKGROUND OF THE INVENTION
Tissue engineering is emerging as a new field in the biomedical sciences. Langer and others have demonstrated the feasibility of seeding and culturing various cell types on biocompatible, biodegradable polymer films and three-dimensional scaffolds or substrates (Takeda et al. (1995); Vacanti et al. (1994); Mooney et al. (1994); Cao et al. (1994); Bell (1994); Gilbert et al. (1993); Freed et al. (1994a); Mooney et al. (1994); Cima et al. (1991); Cima and Langer (1993); Wintermantel et al. (1991); Mooney et al. (1992); Freed et al. (1994b); Freed et al. (1993)). Cell attachment, spreading and replication have been demonstrated to occur on these polymers, and the formation of solid tissue masses of up to one millimeter in thickness has been demonstrated for tissues such as cartilage (Freed et al. (1994a); Freed et al. (1994b); Freed et al. (1993)). Many cell types have been implanted successfully in vivo, including hepatocytes, chondrocytes, fibroblasts, enterocytes, smooth muscle cells and endothelial cells (Takeda et al. (1995); Mooney et al. (1994); Gilbert et al. (1993); Mooney et al. (1994)).
Tissue-engineered constructs may be used for a variety of purposes both in vivo and in vitro. For example, such constructs may serve as prosthetic devices for the repair or replacement of damaged organs or tissues, such as in coronary bypasses or liver grafts. In addition, tissue-engineered constructs can serve as in vivo delivery systems for proteins or other molecules secreted by the cells of the construct. Alternatively, tissue-engineered constructs can serve as in vitro models of tissue function or as models for testing the effects of various treatments or pharmaceuticals.
Of particular interest are vascular tissue-engineered constructs. There are 1.4 million surgical procedures performed annually in this country that require arterial prostheses (Langer and Vacanti (1993)). Small arteries with diameters less than five to six mm cannot be replaced with artificial materials due to high rates of thrombosis (Connolly et al. (1988); Greisler et al. (1988)). Thus, autologous vein or artery grafts are generally used to replace small arteries in the coronary or peripheral circulations. Vein grafts have thin walls that are sometimes damaged when transplanted into the arterial system, and suitable veins are not available in all patients due to amputation or previous vein harvest. Internal mammary arteries, which comprise the majority of arterial grafts, are useful only in the coronary circulation. Thus, there remains a need for developing methods for culturing autologous arterial grafts from a small biopsy of the patient's own tissue, or heterologous arterial grafts from histocompatible cells derived from a donor or cell line.
SUMMARY OF THE INVENTION
The present invention is directed to improved methods for the production of tissue-engineered constructs, including muscular tissue constructs such as vascular constructs. The methods include the use of improved substrates for cell growth, improved cell culture media for cell growth, and the use of distensible bodies to impart pulsatile stretching force to the lumens of constructs during growth. Also provided are improved products, including substrates and cell culture media, for tissue engineering and tissue culture generally. Improved muscular tissue constructs, including vascular constructs, are also provided, which may be used in medicine for the repair or replacement of damaged natural structures.
Thus, in one aspect, the invention provides a method for producing a muscular tissue-engineered construct in which a porous substrate, comprising a biocompatible material, and having an inner surface and an outer surface, is first provided. The inner surface of the porous substrate defines a lumen. Within the lumen, a distensible body is provided which is capable of distending within the lumen so as to contact the inner surface of the substrate. The porous substrate, either before or after inserting the distensible body, is contacted with a suspension comprising muscle cells which adhere to and infiltrate the porous substrate, thereby forming a primary cell-seeded construct. The primary cell-seeded construct is then maintained for a first growth period in an environment suitable for growth of the muscle cells to form a primary tissue-engineered construct. During the first growth period, cyclical increases in pressure within the distensible body are provided, thereby causing the distensible body to distend within the lumen of the construct and to apply pulsatile stretch to the construct. This pulsatile stretch mimics natural pulsatile stretching forces encountered in the body, and aids the growing construct in developing strength and/or an appropriate phenotype.
In another aspect, the invention provides a method for producing a muscular tissue-engineered construct in which a porous substrate comprising a biocompatible material, and having an inner surface and an outer surface, is first provided. The inner surface of the porous substrate defines a lumen. The porous substrate is contacted with a suspension comprising muscle cells which adhere to and infiltrate the porous substrate, thereby forming a primary cell-seeded construct. Rather than a distensible body within the lumen of the construct, a sleeve is provided, either before or after cell-seeding, around a portion of the exterior of the porous substrate. The sleeve is capable of resisting distension of the substrate in response to pressure within the lumen. The primary cell-seeded construct is then maintained for a first growth period in an environment suitable for growth of the smooth muscle cells to form a primary tissue-engineered construct. During the first growth period, intralumenal flow is provided within the lumen, thereby causing the substrate to distend within the sleeve, and to contact the sleeve. The sleeve, by resisting the distension, provides mechanical support to the growing construct. Optionally, during the first growth period, cyclical increases in pressure are also provided within the lumen, thereby causing the substrate to cyclically distend within the sleeve, and thereby applying pulsatile stretch to the construct. This intralumenal flow, and optional pulsatile stretch, mimic natural flow and pulsatile stretching forces encountered in the body, and aids the growing construct in developing strength and/or an appropriate phenotype.
In another aspect, the invention provides a method for producing a muscular tissue-engineered construct in which a porous substrate comprising a biocompatible material, and having an inner surface and an outer surface, is first provided. The inner surface of the porous substrate defines a lumen. Rather than a distensible body or sleeve, an inner surface of the lumen (or a medial layer of the substrate) is provided which is substantially less porous than the outer surface, and this inner surface (or medial layer) is also capable of resisting distension of the substrate in response to pressure within the lumen. The porous substrate is contacted with a suspension comprising smooth muscle cells which adhere to and infiltrate the porous substrate, thereby forming a primary cell-seeded construct. The primary cell-seeded construct is then maintained for a first growth period in an environment suitable for growth of the smooth muscle cells to form a primary tissue-engineered construct. During the first growth period, intralumenal flow within the lumen is provided, thereby causing the substrate to distend. The inner surface (or medial layer), by resisting the distension, provides mechanical support to the growing construct. Optionally, during the first growth period, cyclical increases in pressure are also provided within the lumen, thereby causing the substrate to cyclically distend, and thereby applying pulsatile stretch to the construct. This intralumenal flow, and
Gao Jinming
Langer Robert S.
Niklason Laura E.
Choate Hall & Stewart
Massachusetts Institute of Technology
Naff David M.
Ware Deborah K.
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