Drug – bio-affecting and body treating compositions – Whole live micro-organism – cell – or virus containing – Animal or plant cell
Reexamination Certificate
1997-05-16
2003-12-23
Falk, Anne-Marie (Department: 1632)
Drug, bio-affecting and body treating compositions
Whole live micro-organism, cell, or virus containing
Animal or plant cell
C424S093100, C435S377000, C435S383000, C435S384000, C435S385000, C435S386000
Reexamination Certificate
active
06667034
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and compositions for the growth of mammalian cells in culture, particularly the growth of hematopoietic cell cultures. The present invention also relates to a functioning in vitro human tissue system, which may serve as a model for hematopoiesis. The present invention further relates to a method for assaying the effect of a substance and/or physical condition on a human hematopoietic cell mass or the hematopoietic process. The present invention also relates to a method for controlling the lineage development in an in vitro human tissue system and cultures of cells in which the population of a particular cell type has been enhanced relative to the total cell population in the culture or depleted. In addition, the present invention relates to a method of bone marrow tranplantation, in which the tissue implanted into the donee has been cultured by the present method.
2. Discussion of the Background
All of the circulating blood cells in the normal adult, including erythrocytes, leukocytes, platelets and lymphocytes, originate as precursor cells within the bone marrow. These cells, in turn, derive from very immature cells, called progenitors, which are assayed by their development into contiguous colonies of mature blood cells in 1-3 week cultures in semisolid media such as methylcellulose or agar.
Progenitor cells themselves derive from a class of progenitor cells called stem cells. Stem cells have the capacity, upon division, for both self-renewal and differentiation into progenitors. Thus, dividing stem cells generate both additional primitive stem cells and somewhat more differentiated progenitor cells. In addition to the generation of blood cells, stem cells also may give rise to osteoblasts and osteoclasts, and perhaps cells of other tissues as well. This document describes methods and compositions which permit, for the first time, the successful in vitro culture of human hematopoietic stem cells, which results in their proliferation and differentiation into progenitor cells and more mature blood cells of a specific lineage.
Although there are recent reports of the isolation and purification of progenitor cells (see, e.g., U.S. Pat. No. 5,061,620 as representative), such methods do not permit the long-term culture of viable and dividing stem cells.
In the late 1970s the liquid culture system was developed for growing hematopoietic bone marrow in vitro. The cultures are of great potential value both for the analysis of normal and leukemic hematopoiesis and for the experimental manipulation of bone marrow, for, e.g., retroviral-mediated gene transfer. These cultures have allowed a detailed analysis of murine hematopoiesis and have resulted in a detailed understanding of the murine system. In addition, it has made possible retroviral gene transfer into cultured mouse bone marrow cells. This allowed tagging murine hematopoietic cells proving the existence of the multi-potent stem cell and of the study of the various genes in the process of leukemogenesis.
But while it has been possible to transfer retroviral genes into cultured mouse bone marrow cells, this has not yet been possible in cultured human bone marrow cells because, to date, human long-term bone marrow cultures have been limited both in their longevity and more importantly in their ability to maintain stem cell survival and their ability to produce progenitor cells over time.
Human liquid bone marrow cultures were initially found to have a limited hematopoietic potential, producing decreasing numbers of progenitor cells and mature blood cells, with cell production ceasing by 6 to 8 weeks. Subsequent modifications of the original system resulted only in modest improvements. A solution to this problem is of incalculable value in that it would permit, e.g., expanding human stem cells and progenitor cells for bone marrow transplantation and for protection from chemotherapy, selecting and manipulating such cells, i.e., for gene transfer, and producing mature human blood cells for transfusion therapy.
Studies of hematopoiesis and in vitro liquid marrow cultures have identified fibroblasts and endothelial cells within adhering layers as central cellular stromal elements. These cells both provide sites of attachment for developing hematopoietic cells and can be induced to secrete hematopoietic growth factors which stimulate progenitor cell proliferation and differentiation. These hematopoietic growth factors include granulocyte colony stimulating factor (G-CSF), granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 6 (IL-6).
Cultures of human bone marrow cells on such adherent layers in vitro however have been largely disappointing. Unlike related cultures from other species, such as mouse and tree shrew, human liquid marrow cultures fail to produce significant numbers of either nonadherent hematopoietic precursor cells or clonogenic progenitor cells for over 6 to 8 weeks. And although cultures lasting 3-5 months have been reported, no culture which stably produces progenitor cells from stem cells continuously for more than 4-6 weeks has been reported.
Moreover, nonadherent and progenitor cell production typically declined throughout even the short life of these cultures, so that it is not clear that stem cell survival or proliferation is supported at all by these cultures. Further, when studied in isolation, unstimulated bone marrow stromal cells secrete little if any detectable hematopoietic growth factors (HGFs).
The lack of stable progenitor cell and mature blood cell production in these cultures has led to the belief that they are unable to support continual stem cell renewal and expansion. It has therefore been presumed that the cultures either lack a critical stem cell stimulant(s) and/or contain a novel stem cell inhibitor(s). However, while explanations for failure to detect HGFs and uninduced stromal cell cultures have been suggested, the null hypothesis, which combines the failure to detect HGFs and the relative failure of human liquid marrow cultures, would be that the culture systems used in vitro do not provide the full range of hematopoietic supportive function of adherent bone marrow stromal cells in vivo.
Stem cell and progenitor cell expansion for bone marrow transplantation is a potential application of human long-term bone marrow cultures. Human autologous and allogeneic bone marrow transplantation are currently used as therapies for diseases such as leukemia, lymphoma and other life-threatening disorders. For these procedures however, a large amount of donor bone marrow must be removed to insure that there is enough cells for engraftment.
A culture providing stem cell and progenitor cell expansion would reduce the need for large bone marrow donation and would make possible obtaining a small marrow donation and then expanding the number of stem cells and progenitor cells in vitro before infusion into the recipient. Also, it is known that a small number of stem cells and progenitor cells circulate in the blood stream. If these stem cells and progenitor cells could be collected by phoresis and expanded, then it would be possible to obtain the required number of stem cells and progenitor cells for transplantation from peripheral blood and eliminate the need for bone marrow donation.
Bone marrow transplantation requires that approximately 1×10
8
to 2×10
8
bone marrow mononuclear cells per kilogram of patient weight be infused for engraftment. This requires the bone marrow donation of the same number of cells which is on the order of 70 ml of marrow for a 70 kg donor. While 70 ml is a small fraction of the donors marrow, it requires an intensive donation and significant loss of blood in the donation process. If stem cells and progenitor cells could be expanded ten-fold, the donation procedure would be greatly reduced and possibly involve only collection of stem cells and progenitor cells from peripheral blood and expansion of these stem cells and progenitor cells.
Progenitor cell expa
Armstrong R. Douglas
Clarke Michael F.
Emerson Stephen G.
Palsson Bernhard O.
Falk Anne-Marie
The Regents of the University of Michigan
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