Ex vivo and in vivo methods and related compositions for regenerating hematopoietic stem cell populations

#The present invention relates to methods for regenerating adult hematopoietic stem cells (HSCs) and related compositions by reducing/inhibiting latexin expression and/or latexin activity.

#The material on the accompanying CD-R is hereby incorporated by reference into this application. The accompanying compact disc contains one file, 1028750-000249 HSCS.ST25.txt, which was created on Oct. 2, 2006. The file named 1028750-000249 HSCS.ST25.txt is 5 KB. The file can be accessed using Microsoft Word on a computer that uses Windows OS.

#Hematopoiesis is a complex process for producing multiple and distinct lineages of blood-borne cells throughout the life span of an organism. Hematopoietic stem cells (“HSCs”) represent a subset of undifferentiated cells that resides predominantly in the bone marrow of adult mammals. HSCs, as a population, are capable of self-renewal by maintaining a sufficient number of HSCs within an organism's bone marrow as a reservoir of uncommitted cells that can be further differentiated into various types of new blood cells. Such newly generated blood cells emerge from the bone marrow and enter the circulatory system in order to continuously replace mature/aging circulating blood cell types. The ability of HSCs, as a population, to differentiate and to give rise to cells of multi-lineages is critical for the preservation of an organism.

#FIG. 1 illustrates various biochemical pathways mediated by latexin that may be involved in the regulation of HSC proliferation in mammals, as described in Example 1.

#FIG. 2 illustrates a genomic map of congenic intervals identified in reciprocal Chr.3 congenic mouse strains, as described in Example 1.

#FIG. 3 illustrates a genome-wide linkage analysis based on GeneNetwork that associates the trait regulating HSC population size with three quantitative trait loci (QTL) on Chromosomes (Chr) 3, 5, and 18, respectively, as described in Example 4.

#Various embodiments provide methods and related compositions useful for reconstituting hematopoietic stem cells (HSCs) within a patient in need of HSC renewal. For example, the present methods are useful for the treatment of patients affected with disorders, diseases, and/or cancers that deleteriously compromise the number of endogenous HSCs and differentiated forms of such HSCs within patients. Examples of disorders, diseases, and/or cancers contemplated for treatment by the present methods and compositions include diseases of the blood, diseases of the bone marrow, cancers of the blood, and cancers of the bone marrow, including various types of anemia, leukemia, immunological disorders, thalassemia major, sickle-cell disease, myelodysplastic syndrome, lymphoma, aplastic anemia, and multiple myeloma. Patients that may benefit from treatments that utilize the present methods and related compositions include candidates for bone marrow transplantation (“BMT”) and hematopoietic stem cell transplantation (“HSCT”). Transplantation therapies can be effective for the treatment of various types of leukemia and any disorder/disease/cancer for which patients are subjected to radiotherapy and/or chemotherapy. The renewed or regenerated population of HSCs that can be induced by the present methods and compositions are useful for various applications, including regenerative medicine, tissue engineering, tissue repair, cancer therapy, and gene therapy. As described in the following embodiments, a given HSC population obtained from a donor or within a recipient host (i.e., a patient) can be induced to proliferate and/or to suppress apoptosis by providing antagonistic compounds/compositions that can inhibit latexin expression and/or latexin activity.

#As used throughout the specification and the appended claims, the terms listed below have the following meanings, wherein “a” means one or more:

#The terms “hematopoietic stem cells” (“HSCs”) refer to a heterogeneous mixture of undifferentiated progenitor stem cells, mainly composed of long-term HSCs (“LT-HSCs”) and short-term HSCs (“ST-HSCs”). LT-HSCs are undifferentiated stem cells that have the capacity for self-renewal throughout the life span of an organism. ST-HSCs are undifferentiated stem cells that have the capacity for self-renewal for a limited time prior to full differentiation into a specific lineage. For example, HSCs can differentiate into hematopoietic progenitor cells (“HPCs”) that can further differentiate into clonogenic cells, or cells of a single lineage, that represent a subset of a hematopoietic lineage. HSCs include non-embryonic stem cells isolated from post-natal animals. HSCs include “pluripotent adult stem cells” isolated from the bone marrows of mammals that are capable of differentiating into tissues of all three germ or dermal layers, such as the mesoderm, endoderm, and ectoderm. A “pluripotent stem cell” refers to a stem cell that exhibits the capacity to grow into any type of cell that constitutes an organism. A pluripotent cell can be self-renewing and can remain dormant/quiescent within a tissue. HSCs include “multipotent stem cells” that exhibit the capacity to grow into any subset of cells that constitute an organism. HSCs include undifferentiated stem cells that exhibit a distinct profile of cell surface markers, including the following combination of markers: Thy-1lo Sca-1+ Lineage− c-kit+; or CD150+CD48− Sca-1+ Lineage− c-kit+; or Thy-1lo CD150+ CD48− Sca-1+ Lineage− c-kit+ (Kiel et al., Cell, Vol. 121, p 1109-1121 (2005)). HSCs that express the combination of human counterparts for these markers are preferably contemplated. The following references are herein incorporated by reference in their entirety: Cheshier et al., P.N.A.S., Vol. 96, p 3120-3125 (1999); Eckfeldt et al., Nature, Vol. 6, p 726-737 (2005); Wright et. al., Science, Vol. 94, p 1933-1936 (2001); and Preston et al., J. Clin. Pathol. Vol. 56, p 86-96 (2003).