Pluripotent stem cells

In US 2005/0079608, the inventors propose a method to isolate adult stem cells.  A cell population containing committed progenitor cells is transformed with a construct comprising a telomerase promoter operably linked to a selectable marker.  Because stem cells express telomerase, the introduced telomerase promoter is expected to be active.  By growing the transformed cells under selecting conditions, an enriched population of adult stem cells can be obtained.

Mesenchymal stem cells from bone marrow are the subject of a series of patent documents.  Mesenchymal stem cells have been reported to differentiate into bone cells, chondrocytes, adipocytes, myocytes, tendon cells, and cardiomyocytes.  Clearly, if mesenchymal stem cells can be propagated in culture without losing pluripotency, the stem cells would be a valuable resource for regenerative medicine.


In Stem Cell Information [World Wide Web site]. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services, 2007 [cited Monday, January 29, 2007] Available at <http://stemcells.nih.gov/info/media/defaultpage>

US 6,645,763 B2 claims a specific, immortalized bone marrow mesenchymal stem cell line.  The line was made by transforming human adult bone marrow mesenchymal cells, which were commercially obtained, with a retroviral vector that contained hTERT-encoding sequences inserted between a pair of site-specific recombination sequences (e.g., LoxP).  The cell line was demonstrated to differentiate into osteoblasts and into adipocytes.

Patent applications, US 2005/0084959 and EP 1 669 441 A1, filed by a Japanese group, are directed to immortalized mesenchymal stem cells and a use for them, respectively.  In US ‘959, immortalized mesenchymal stem cells are obtained by immortalization using a telomerase gene, a “gene derived from telomerase” or a gene that regulates the expression of telomerase.  In EP ‘441, the applicants claim a method for differentiating a mesenchymal stem cell into a hepatocyte.  One of the sources for the stem cell is a mesenchymal stem cell that has been transformed with a construct expressing hTERT.

One of the very difficult cell types to propagate in culture is neural cells.  Moreover, damaged brain or spinal cells are largely incapable of significant self-repair.  The plight of Christopher Reeve dramatically underscored this problem.  One impediment to scientific and medical advances is the scarcity of adult neuronal precursor cells.  Other clinically-important progenitor cells in the brain, such as progenitors for oligodendrocytes, spinal cord motor neurons, midbrain dopaminergic and cholinergic neurons, are also resistant to propagation in vitro.  In early 2004, Roy and Goldman published a break-through set of experiments in this area (Roy et al. 2004).  Lineage-restricted progenitors of the central nervous system (CNS) in fetal spinal cord were transformed with a retroviral vector that over-expressed hTERT.  The immortalized cells gave rise to phenotypically restricted subpopulations of either glia or neurons.   Importantly, the cells differentiated into neurons when implanted in xenografts.  The method used to generate the immortalized neural progenitor cells is claimed in US 7,150,989.

Cartilage degradation is a feature of osteoarthritis and rheumatoid arthritis.  Degradation results in joint pain and impairs mobility.  Sufferers of these diseases may even need a wheelchair to get around.  Some limited progress has been made in propagating and differentiating chondrocyte precursors.  Unfortunately, the sources of these cells are limited.  The patent application US 2003/0109038 addresses this problem by disclosing a method to obtain human chondrocytes by differentiating them from embryonic stem cells.  The embryonic stem cells are induced to undergo general differentiation and then coaxed along the chondrocyte differentiation pathway by culturing them in the presence of factors.  Further, the cells can be immortalized by transformation with an expression vector containing telomerase-encoding sequence.

Obesity is a disease of “epidemic” proportions and one of the most significant health problems in industrialized countries.  Consequently, more scientific investigation has been directed to all aspects of adipocytes biology, including adipogenesis.  While there is plenty of fat tissue in obese people, adipocytes make up about a third of the cells, the other two-thirds comprise blood vessels, nerve tissue, fibroblasts and preadipocytes in various stages of differentiation.  Preadipocytes are not easily distinguished from fibroblasts.  Even when preadipocytes are isolated and cultured, they senesce and also lose adipogenic potential.  US 2005/0008621 is directed to methods for generating primary preadipocyte strains that have increased replicative potential and also maintain adipogenic capacity.  One of the methods that is claimed and demonstrated in the application is to transform primary adipocytes with sequences encoding hTERT and select for those that express hTERT.

Many other patent applications, not discussed in detail here, disclose methods for obtaining pluripotent stem cells and, once obtained, increasing their lifespan by transformation with hTERT-encoding sequences.

Patent Data Title and relevant claims Family Data
EP 1 669 441

Assignee:

Renomedix Institute

Earliest priority:

27 Aug 2003

Filed:

27 Feb 2004

Method of differentiating mesenchymal stem cell into liver cell and artificial human liver cell

Claim 1:  A method for differentiating a mesenchymal stem cell, a mesenchymal progenitor cell, or a mesenchymal cell into a hepatocyte using liver tissue that has experienced chronic livery injury.

CA 2536934 AA

KR 2006065712 A
WO 05/024004 A1

US 6,645,763

Assignee:

Inventors –

Kobayashi, N

Leboulch, P

Tanaka, N

Fujiwara, T

Filed:

12 Oct 2001

Granted:

11 Nov 2003

Expiry date:

27 Nov 2021

Immortalized bone marrow mesenchymal stem cell

Claim 1: An immortalized bone marrow mesenchymal stem cell line deposited as FERM BP-8197.

JP 2003174870A2

US 7,150,989

Assignee:

Cornell Research Foundation Inc.

Earliest priority:

10 Aug 2001

Filed:

09 Aug 2002

Granted:

19 Dec 2006

Expiry date:

05 Nov 2022

Telomerase immortalized neural progenitor cells

Claim 1: A method of immortalizing neural progenitor cells comprising: providing a population of neural progenitor cells and immortalizing the population of neural progenitor cells by introduction of a nucleic acid sequence encoding telomerase reverse transcriptase operably linked to a promoter, either before or after the neural progenitor cells are enriched or purified wherein said telomerase reverse transcriptase is produced in sufficient quantity to immortalize said neural progenitor cells.

AU 2002327433 A1
WO 03/014320 A3

US 2003/109038

Assignee:

Geron Corporation

Earliest priority:

07 Dec 2001

Filed:

06 Dec 2002

Chondrocyte precursors derived from human embryonic stem cells

Claim 1:  A cell population obtained by differentiating primate pluripotent stem (pPS) cells, in which at least 5% of the cells synthesize either Type II collagen or aggrecan from an endogenous gene.

AU 2002366602 AA
CA 2468335 AA
CN 1599793 A
EP 1463800 A4
GB 2399348 A1
JP 2005511083 T2
KR 2005044733 A
US 2006148077 A1
WO 03/050250 B1

US 2005/008621

Assignee:

Boston Medical Centre Corporation

Earliest priority:

06 Oct 2001

Filed:

07 Oct 2002

Preadipocyte cell strains and uses therefore

Claim 1:  A primary preadipocyte strain, wherein said strain expresses telomerase reverse transcriptase (TERT) such that said strain maintains replicative potential and adipogenic capacity.

AU 2002332028 A1

WO 03/031640 A3

US 2005/079608

Assignee:

Rappaport Family Institute

Earliest priority:

05 Feb 2002

Filed:

04 Aug 2004

Lineage committed stem cells selected for telomerase promoter activity

Claim 1:  An enriched population of adult stem cells derived from stem cells comprising a plurality of committed progenitor cells stably transfected with a polynucleotide construct comprising a telomerase promoter element operably linked to a sequence encoding a selectable marker, wherein the progenitor cells express telomerase promoter activity.

AU 2003208580 A1
EP1472340 A4
WO 03/066839 A1

US 2005/084959

Assignee:

Renomedix Institute

Earliest priority:

31 Oct 2001

Filed:

31 Oct 2002

Immortalized mesenchymal cells and utilization thereof

Claim 1:  An immortalized mesenchymal system-related cell, which is a mesenchymal system-related cell that is selected from mesenchymal stem cells, mesenchymal precursor cells, mesenchymal cells and cells derived from mesenchymal cells, and is immortalized by high expression or activation of an immortalizing gene.

EP 1447443 A4
WO 03/038076 A1