Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Reexamination Certificate
1999-12-29
2002-08-06
Naff, David M. (Department: 1651)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
C424S093700, C425S177000, C425S180000, C425S395000
Reexamination Certificate
active
06428802
ABSTRACT:
BACKGROUND OF THE INVENTION
The technical field of this invention is the creation of artificial organs in vitro with subsequent implantation of the artificial organ in vivo, and in particular to the creation of multilayered cellular organs with a natural interface between the tissue layers.
A considerable amount of effort from the medical community is directed to substitution of defective organs with replacements of the entire organ or a part of the organ. In many instances these organs are completely synthetic, such as artificial hearts, or completely natural, such as organs from mammalian donors. However, there are limitations with both approaches. With natural organ transplants there is the potential risk for transmission of diseases like AIDS and hepatitis, or rejection of the transplanted organ. In addition, the availability of a donor organ is often a rate limiting factor. With synthetic organs there are complications associated with the formation of mechanical failure and calculus formation.
Several approaches have been explored for reconstruction of defective organs and tissues. Initially, the feasibility of cell survival was demonstrated by injecting suspensions of dissociated cells into other tissues such as fat, liver or, with the stroma of the host tissue providing the matrix for cell attachment and reorganization. However, a sustained increase in cell mass was not observed, thus underscoring the limitations of trying to achieve growth and structuring of new tissue in pre-existing tissue (See Cima, et al., (1991)
J. Biomech. Engr
., 113:143-151).
Alternatively, organs have been prepared on various matrices. The cellular morphology and metabolic activity of cultured cells are affected by the composition of the matrix on which they are grown. Presumably cultured cells function best (i.e. proliferate and perform their natural in vivo functions) when cultured on matrices that closely mimic their natural environment. Currently, in vitro studies of cellular function are limited by the availability of cell growth matrices that present the appropriate physiological environment for proliferation and development of the cultured cells.
A further limitation in organ reconstruction has been mimicking the cellular organization of a multilayered organ. Many organs are made up of multiple layers of different tissues. Depending on the functional role of the organ, different tissues confer different properties to the organ. For example, the bladder has three main layers of tissue: the mucosa, submucosa and detrusor. The mucosa, comprising urothelial cells, is the innermost layer and is composed of transitional cell epithelium. The submucosa lies immediately beneath the mucosa and its basement membrane. It is a layer of interstitial protein that supports blood vessels, which supply the mucosa with nutrients and the lymph nodes which aid in the removal of waste products. The submucosa serves an important function, and is produced as the interface between the mucosa and the detrusor. The detrusor is a layer of smooth muscle cells which expands to store urine and contracts to expel urine. Natural interfaces produced in vivo between different cell populations result in the formation of several biological features that have important structural and functional properties, for example the production of the submucosa which supplies nutrients to the mucosa.
Reconstruction of multilayered organs has typically involved coating both sides of a matrix with different cell populations. In these instances, the matrix functions as an artificial barrier between the different cell populations (See Atala et al. U.S. Ser. No. 60/063,790, filed Oct. 31, 1997, entitled “Bladder Reconstruction”). Although some interactions occur between the two different cell populations through the pores of the matrix, these interactions, are at best, minimal, and lack the cell-cell interactions characteristic of whole tissue in vivo. This prevents normal functional and morphological interactions which result in the formation of biological material, such as epithelial cells, like, bladder submucosa, oral mucosa and nasal epithelium. The presence of the submucosa provides growth factors and other proteins which promote normal division and differentiation.
Therefore, there exists a need to create artificial organs that have natural interfaces between different cell populations, to produce artificial organs that more closely resemble the interface of native in vivo organs.
SUMMARY OF THE INVENTION
It is the object of the invention to provide artificial organs with a chimeric interface between two different cell populations that more closely resembles the interface of a native in vivo organ.
It is the object of the invention to provide methods of producing artificial organs with a chimeric interface between two different cell populations that more closely resembles the interface of a native in vivo organ.
It is the object of the invention to provide artificial organs in which cells retain their normal morphology and cell function.
The invention is based, in part, on the discovery that growth of a different population of cells on biocompatible substrate with a chimeric interface between the different cell populations produces new interstitial biomaterial that resembles the equivalent biomaterial in a native in vivo organ. This can be accomplished by sustaining active proliferation of heterogenous polylayers comprising different populations of cells in culture, such that each polylayer resembles the equivalent parenchyma tissue of an in vivo organ. This may be due, in part, by the method of producing the polylayers. Polylayers are produced by culturing a first homogenous cell population one layer at a time on the biocompatible substrate until the cells of each layer are actively proliferating. The polylayers are incubated until the cells develop and proliferate to resemble the structure and morphology of the equivalent parenchyma tissue of an in vivo organ.
Polylayers developed by the method of the invention therefore produce proteins, growth factors and regulatory factors necessary to support the long term proliferation of the homogenous cell population. After the first polylayer has been established, this provides the surface for producing the second polylayer. The second polylayer comprises a second homogenous cell population that is different from the first homogenous cell population. The second polylayer is developed by culturing the second homogenous cell population one layer at a time until the cells of each layer are actively proliferating to produce a polylayer of cells.
A chimeric interface is produced where the cells of the two polylayers are in contact. This creates a cellular microenvironment that is analogous to that of an in vivo multicellular organ. By creating such a microenvironment, the cells at the interface proliferate, differentiate and segregate as they would in vivo, unhindered by any structural constraints. This also allows the cells at the interface to resume a more natural morphology, structure, and spatial distribution, which more closely approximates conditions in vivo. The growth of cells at the chimeric interface may be further enhanced by adding proteins, glycoproteins, glycosaminoglycans, a cellular matrix, and other materials between the different polylayers.
Accordingly, in one aspect, the invention features an artificial organ construct comprising:
a first cultured polylayer of cells derived from a first cell population; and
a second cultured polylayer of cells derived from a second cell population that is different from the first cell population, wherein the second polylayer is coupled to the first polylayer by a chimeric interface such that the construct provides the functional equivalent of a natural biological structure upon implantation.
In one embodiment, the artificial organ further comprises a third cultured polylayer of cells derived from a third cell population that is different from the first cell population and the second cell population, wherein the third polylayer is coupled to
Children's Medical Center Corp.
Engellenner Thomas
Nutter & McClennen & Fish LLP
Sagoo Jasbir
LandOfFree
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