Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or...
Reexamination Certificate
2002-03-15
2004-11-02
Redding, David A. (Department: 1744)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
C435S005000, C435S007230, C435S007240, C435S288500
Reexamination Certificate
active
06811968
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method of monitoring cell motility and chemotaxis.
BACKGROUND
Test devices, such as those used in chemotaxis, haptotaxis and chemoinvasion are well known. Such devices are disclosed for example in U.S. Pat. Nos. 6,329,164, 6,238,874, and 5,302,515.
Three processes involved in cell migration are chemotaxis, haptotaxis, and chemoinvasion. Chemotaxis is defined as the movement of cells induced by a concentration gradient of a soluble chemotactic stimulus. Haptotaxis is defined as the movement of cells in response to a concentration gradient of a substrate-bound stimulus. Chemoinvasion is defined as the movement of cells into and/or through a barrier or gel matrix. The study of chemotaxis/haptotaxis and chemoinvasion and the effects of external stimuli on such behavior are prevalent throughout contemporary biological research. Generally, this research involves exposing a cell to external stimuli and studying the cell's reaction. By placing a living cell into various environments and exposing it to different external stimuli, both the internal workings of the cell and the effects of the external stimuli on the cell can be measured, recorded, and better understood.
A cell's migration in response to a chemical stimulus is a particularly important consideration for understanding various disease processes and accordingly developing and evaluating therapeutic candidates for these diseases. By documenting the cell migration of a cell or a group of cells in response to a chemical stimulus, such as a therapeutic agent, the effectiveness of the chemical stimulus can be better understood. Typically, studies of disease processes in various medical fields, such as oncology, immunology, angiogenesis, wound healing, and neurobiology involve analyzing the chemotactic and invasive properties of living cells. For example, in the field of oncology, cell migration is an important consideration in understanding the process of metastasis. During metastasis, cancer cells of a typical solid tumor must loosen their adhesion to neighboring cells, escape from the tissue of origin, invade other tissues by degrading the tissues' extracellular matrix until reaching a blood or lymphatic vessel, cross the basal lamina and endothelial lining of the vessel to enter circulation, exit from circulation elsewhere in the body, and survive and proliferate in the new environment in which they ultimately reside. Therefore, studying the cancer cells' migration may aid in understanding the process of metastasis and developing therapeutic agents that potentially inhibit this process. In the inflammatory disease field, cell migration is also an important consideration in understanding the inflammatory response. During the inflammation response, leukocytes migrate to the damaged tissue area and assist in fighting the infection or healing the wound. The leukocytes migrate through the capillary adhering to the endothelial cells lining the capillary. The leukocytes then squeeze between the endothelial cells and use digestive enzymes to crawl across the basal lamina. Therefore, studying the leukocytes migrating across the endothelial cells and invading the basal lamina may aid in understanding the inflammation process and developing therapeutic agents that inhibit this process in inflammatory diseases such as adult respiratory distress sydrome (ARDS), rheumotoid arthritis, and inflammatory skin diseases. Cell migration is also an important consideration in the field of angiogenesis. When a capillary sprouts from an existing small vessel, an endothelial cell initially extends from the wall of the existing small vessel generating a new capillary branch and pseudopodia guide the growth of the capillary sprout into the surrounding connective tissue. New growth of these capillaries enables cancerous growths to enlarge and spread and contributes, for example, to the blindness that can accompany diabetes. Conversely, lack of capillary production can contribute to tissue death in cardiac muscle after, for example, a heart attack. Therefore studying the migration of endothelial cells as new capillaries form from existing capillaries may aid in understanding angiogenesis and optimizing drugs that block vessel growth or improve vessel function. In addition, studying cell migration can also provide insight into the processes of tissue regeneration, organ transplantation, autoimmune diseases, and many other degenerative diseases and conditions.
Cell migration assays are often used in conducting these types of research. Commercially available devices for creating such assays are sometimes based on or employ a transwell system (a vessel partitioned by a thin porous membrane to form an upper compartment and a lower compartment). To study cell chemotaxis, cells are placed in the upper compartment and a migratory stimulus is placed in the lower compartment. After a sufficient incubation period, the cells are fixed, stained, and counted to study the effects of the stimulus on cell chemotaxis across the membrane.
To study chemoinvasion, a uniform layer of a MATRIGEL™ matrix is placed over the membrane to occlude the pores of the membrane. Cells are seeded onto the MATRIGEL™ matrix in the upper compartment and a chemoattractant is placed in the lower compartment. Invasive cells attach to and invade the matrix passing through the porous membrane. Non-invasive cells do not migrate through the occluded pores. After a sufficient incubation period, the cells may be fixed, stained, and counted to study the effects of the stimulus on cell invasion across the membrane.
The use of transwells has several shortcomings. Assays employing transwells require a labor-intensive protocol that is not readily adaptable to high-throughput screening and processing. Because of the configuration of a transwell system, it is difficult to integrate with existing robotic liquid handling systems and automatic image acquisition systems. Therefore, much of the screening and processing, such as counting cells, is done manually which is a time-consuming, tedious, and expensive process. Cell counting is also subjective and often involves statistical approximations. Specifically, due to the time and expense associated with examining an entire filter, only randomly selected representative areas may be counted. Moreover, even when these areas are counted, a technician must exercise his or her judgment when accounting for a cell that has only partially migrated through the filter.
Transwell-based assays have intrinsic limitations imposed by the thin membranes utilized in transwell systems. The membrane is only 50-30 microns (elm) thick, and a chemical concentration gradient that forms across the membrane is transient and lasts for a short period. If a cell chemotaxis assay requires the chemotactic gradient to be generated over a long distance (>100-200 &mgr;m) and to be stable over at least two hours, currently available transwell assays cannot be satisfactorily performed.
Notwithstanding the above, perhaps the most significant disadvantage of transwells is the lack of real-time observation of chemotaxis and chemoinvasion. In particular, the changes in cell morphology during chemotaxis cannot be observed in real-time with the use of transwells. In transwells, when the cells are fixed to a slide, as required for observation, they are killed. Consequently, once a cell is observed it can no longer be reintroduced into the assay or studied at subsequent periods of exposure to a test agent. Therefore, in order to study the progress of a cell and the changes in a cell's morphology in response to a test agent, it is necessary to run concurrent samples that may be slated for observation at various time periods before and after the introduction of the test agent. In light of the multiple samples required for each test, in addition to the positive and negative controls required to obtain reliable data, a single chemotaxis assay can require dozens of filters, each of which needs to be individually exami
Aumond Bernardo D.
Benoit Brian
Brown Matthew
Kim Enoch
Kirk Gregory L.
Redding David A.
Surface Logix Inc.
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