Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Tissue
Reexamination Certificate
1999-06-09
2004-04-13
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Tissue
Reexamination Certificate
active
06719805
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to devices and methods for the treatment tissue. In particular, the treatment involves implantation of angiogenic implants in combination with therapeutic materials such as tissue cells or cell material into injured, diseased or otherwise dysfunctional tissue such as cardiac muscle tissue.
BACKGROUND OF THE INVENTION
Muscle tissue can become dysfunctional for a variety of reasons. Disease, injury or the effects of surgical intervention all can adversely affect the function of muscle tissue. In many instances tissue becomes dysfunctional due to inadequate blood supply attributable to a variety of causes. Tissue suffering from inadequate blood supply is defined as ischemic tissue. Tissue that is deprived from blood for extended periods of time can become necrotic and permanently non-functioning. Muscle tissue disease can occur anywhere in the body, but commonly occurs in the legs and the heart. Heart disease presents a critical situation to those afflicted and potential treatments to intervene in the disease process of the heart have been the subject of increased study in recent years.
A common approach to treatment of muscle disease has been to treat the subject tissue with pharmacological agents. However, general administration of such agents presents several problems. Typically, agents useful in treating muscle disease are expensive, making general administration through the body relatively costly. Additionally, pharmacological agents can be toxic to other regions of the body, especially when administered in large doses, required to obtain a therapeutically effective concentration at the intended treatment site.
Local delivery of therapeutic agents addresses some of the concerns associated with a therapeutic approach to muscle disease treatment. Delivery of discreet amounts the therapeutic substance directly to the intended treatment site via injection or via a drug delivery catheter navigated to the location offers several benefits. A reduced amount of therapeutic substance can be used because the agent is released only at the intended location and thus is not diluted by its passage throughout the body as occurs with general administration. Also, other areas of the body will not be affected by administration of the substance if it remains only at the intended tissue location. U.S. Pat. No. 5,354,279 (Hofling) discloses a catheter for localized delivery of an agent by injection. However, substances delivered locally do not always remain only at the intended location. Frequently, the substance is not absorbed into the tissue as expected and may be carried away by the bloodstream. Also, even if the substance is injected into the subject tissue as intended, it may be squeezed out of the tissue rapidly rather than being retained for a therapeutically beneficial period of time. This occurrence is especially problematic when treating highly active muscle tissue such as myocardial tissue of the heart because its exaggerated cyclical contraction and relaxation tend to force out locally delivered materials from the intended tissue location.
In recent years treatment of muscular dysfunction with biological therapeutic materials has been a subject of increased study. Stem cells, as well as cell components, such as DNA and proteins, are considered to hold potential as a promising treatment for diseased tissue regions. It has been reported that stem cells may be capable transforming into a highly specialized cells of a given organ in which they are placed. J. Hescheler et al.,
Embryotic Stem Cells: A Model To Study Structural And Functional Properties In Cardiomyogenesis
, Cardiovascular Research 36 (1997) 149-162. Addition of such cells to the tissue of an organ serves to initiate growth of the tissue of that organ. For example such cells may be delivered to regions of diseased tissue of the heart with the expectation that the cells will become cardiomyocytes initiating new cardiac muscle growth to replace the diseased muscle that is present. Precursor cells may also be effective in treating diseased tissue of the heart. R. K. Li et al.,
Cell Transplantation to Repair Broken Hearts
, Can J. Cardiol 1998;14(5): 735:744. Treatment of diseased cardiac tissue by transplanting skeletal myoblast into the subject tissue has also been the subject of recent study. Charles E. Murphy et al.,
Skeletal Myoblast Transplantation for Repair of Myocardial Necrosis
, J. Clin. Invest. 1996 98:2512-2523. However, effective delivery of these biological herapeutic materials is subject to the same concerns discussed above in connection with delivery of pharmacological therapeutic materials. Specifically, biological therapeutic materials can be ejected from the intended muscle location by movement of the muscle, prior to any ameliorative effect the cells may bring to the area.
Biological therapeutic materials present an additional challenge in order to be delivered effectively in that their metabolic activity must be sustained while they are implanted so that they remain viable and capable of carrying out their intended function. The biological materials require a blood supply that carries nutrients to sustain their viability. However, an adequate supply of blood is typically unavailable at the site of diseased tissue where such biological materials would be applied. This is especially true in regions that are ischemic.
It would be desirable to provide a muscle tissue treatment that effectively delivers therapeutically beneficial materials to an intended tissue location while addressing the above-mentioned challenges to effective delivery of a therapeutic material. It is an object of the present invention to provide devices and methods for treating muscle dysfunction that address those concerns.
SUMMARY OF THE INVENTION
The present invention provides devices and methods for diseased tissue such as muscle tissue that has become dysfunctional due to disease. The devices and methods are intended to be useful in any tissue of the human body. However, the invention is believed to be particularly useful in the treatment of heart muscle that has become damaged or dysfunctional because of disease, ischemia or other injury. The treatment comprises implantation into subject tissue of an angiogenic implant device in combination with therapeutic material associated with the device. Though the angiogenic device may have pharmacological agents associated with it, biological materials such as tissue, cells or cell material are believed to be particularly well suited for combination with the device because the device will serve as a scaffold holding them in place in the host tissue and will initiate angiogenic activity that will serve to supply the biological materials with needed blood.
Therapeutic materials are considered to comprise cells or, groups of cells forming tissue. Examples of therapeutic cells are stem cells, myoblasts, cardiomyocytes, or precursor cells or genetically engineered cells potentially useful in the treatment of tissue disease, ischemia and necrosis that may occur anywhere in the human body. In particular, ailments that afflict myocardial muscle tissue are addressed by the present invention. Therapeutic materials may also include growth factors or cell components such as genes or DNA. It is also recognized that inhibitors such as tumor necrosis factors may be delivered by the devices and methods of the present invention for controlling undesirable tissue growth such as that of tumors. Such treatment is also to be considered within the scope of the invention.
The angiogenic implants utilize the body's own healing process to induce angiogenesis and recruitment of existing vessels to the implant site. Vessel growth and recruitment is believed to be initiated by injury or aggravation of the tissue in which the device has been implanted. Fibrin created during the tissue's injury response may additionally help to promote angiogenesis because its fibrous network provides a host structure for endothelial cells, which will form the new blood vessels to
C. R. Bard Inc.
Jackson Suzette J.
Kirkpatrick & Lockhart LLP
Willse David H.
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