JP5030039B2 - Method for evaluating stem cell differentiation potential - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simply determining whether a stem cell is a cell forming a tumor such as a teratoma in a living body or a cell capable of differentiating into various cells without tumorigenesis in the living body to contribute to normal histogenesis. <P>SOLUTION: There is provided the method for evaluating the possibility that the stem cell is capable of differentiating into a cell composing a desired tissue in the living body including following steps: (1) transplanting the stem cell which is the object of evaluation into a primordium of a desired tissue of a non-human mammal; (2) culturing the tissue primordium in vitro; and (3) determining the possibility that the stem cell is capable of differentiating into the cell composing the tissue in the living body using the degree of the dispersion of the cell derived from the transplanted stem cell in the cultured tissue primordium as an index. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a method for evaluating whether stem cells can be differentiated into cells constituting a desired tissue in vivo.

  Various stem cells exhibiting pluripotency have been established by recent advances in stem cell research. In order to properly regenerate organs and tissues using these stem cells at the clinical level, it is confirmed in advance that the stem cells used can be properly differentiated into target organs and can form normal tissue morphology. This is very important.

  Among stem cells established to date, ES cells and iPS cells have the ability to proliferate and differentiate into various cells (Non-Patent Document 1), but they are directly transferred into the living body. When transplanted, in many cases, it cannot contribute to normal tissue construction and forms a teratoma (Non-patent Document 2). On the other hand, somatic stem cells such as mesenchymal stem cells (MSC) often undergo replicative senescence in in vitro subculture, but when transplanted in vivo, they differentiate into various cells without tumor formation, Contributes to normal tissue construction (Non-patent Document 3). However, in order to confirm which of the above two properties a stem cell has, many repeated cultures and differentiation induction tests must be performed, and thus a lot of time is consumed. Therefore, in order to rapidly develop stem cells that can be reliably differentiated into tissues and organs, it is easy to screen whether the various stem cells have the above-mentioned properties and whether the stem cells have been improved so as not to cause teratoma formation. Establishment of a method to do this is desired.

Nagata M. et al., J. Gene Med., Vol. 5; p. 921, 2003 Asano T. et al., Methods Mol. Bio., Vol. 329; p. 459, 2006 Hara M. et al., J. Autoimmun., Vol. 30; p. 163, 2008

  An object of the present invention is whether stem cells are cells that form tumors such as teratomas in vivo, or are cells that can differentiate into various cells in vivo without tumor formation and contribute to normal tissue structure It is to provide a method for simply assaying.

  As a result of intensive studies, the inventors of the present invention have made stem cell tumor formation based on the degree of cell dispersion in a fluorescent image obtained by fluorescently labeling stem cells by introduction of a fluorescent gene or the like and driving them into a fetal kidney primordia of a mammal. The present inventors have found that the presence or absence of the ability can be easily determined, and completed the present invention.

That is, the present invention relates to the following.
[1] A method for evaluating whether or not stem cells can be differentiated into cells constituting a desired tissue in vivo, including the following steps:
(1) transplanting stem cells to be evaluated into a primordium of a desired tissue of a non-human mammal,
(2) culturing the tissue primordium in vitro;
(3) Determining the possibility that the stem cells can differentiate into cells constituting the tissue in vivo using the degree of dispersion of the cells derived from the transplanted stem cells in the cultured tissue primordia as an index.
[2] The method according to [1], wherein the stem cells to be evaluated are labeled so as to be distinguishable from the tissue primordium cells to be transplanted.
[3] The method according to [2], wherein the label is a fluorescent label.
[4] The method according to [1], wherein the tissue is a kidney.
[5] The method according to [1], wherein the stem cell is a mesenchymal stem cell.

  By using the method of the present invention, stem cells are cells that form tumors such as teratomas in vivo, or cells that can differentiate into various cells without tumor formation in vivo and contribute to normal tissue formation. It is possible to easily test whether it exists.

The time-dependent change of the fluorescence image of the metanephron which introduce | transduced the monkey ES cell is shown. The visible light image of the metanephron which introduce | transduced the monkey ES cell is shown. Teratomas were formed and differentiation into 3 germ layers was observed. The time-dependent change of the fluorescence image of the metanephron which transferred porcine MSC is shown. The time-dependent change of the fluorescence image of the metanephron which transferred mouse iPS cell is shown.

The present invention provides a method for evaluating whether stem cells can be differentiated into cells constituting a desired tissue in vivo, including the following steps:
(1) transplanting stem cells to be evaluated into a primordium of a desired tissue of a non-human mammal,
(2) culturing the tissue primordium in vitro;
(3) Determining the possibility that the stem cells can differentiate into cells constituting the tissue in vivo using the degree of dispersion of the cells derived from the transplanted stem cells in the cultured tissue primordia as an index.

  In the present specification, the “stem cell” means an immature cell having self-renewal ability and differentiation / proliferation ability. The stem cells include subpopulations such as pluripotent stem cells, multipotent stem cells, unipotent stem cells, etc., depending on the differentiation ability. A pluripotent stem cell means a cell that cannot be an individual by itself, but has an ability to differentiate into all tissues and cells constituting a living body. A multipotent stem cell means a cell having the ability to differentiate into multiple types of tissues and cells, although not all types. A unipotent stem cell means a cell having the ability to differentiate into a specific tissue or cell.

  Examples of pluripotent stem cells include embryonic stem cells (ES cells), EG cells, iPS cells, and the like. ES cells can be produced by culturing inner cell masses on feeder cells. EG cells can be produced by culturing primordial germ cells in a medium containing mSCF, LIF and bFGF (Cell, 70: 841-847, 1992). iPS cells can be produced by introducing Oct3 / 4, Sox2 and Klf4 (c-Myc or n-Myc as necessary) into somatic cells (eg, fibroblasts, skin cells, etc.) (Cell , 126: p. 663-676, 2006; Nature, 448: p. 313-317, 2007; Nat Biotechnol, 26: p. 101-106, 2008; Cell 131: 861-872, 2007). Stem cells established by culturing early embryos produced by nuclear transfer of somatic cell nuclei are also preferred as pluripotent stem cells (Nature, 385, 810 (1997); Science, 280, 1256 (1998). Nature Biotechnology, 17, 456 (1999); Nature, 394, 369 (1998); Nature Genetics, 22, 127 (1999); Proc. Natl. Acad. Sci. USA, 96, 14984 (1999)), Rideout III (Nature Genetics, 24, 109 (2000)).

  Examples of multipotent stem cells include somatic stem cells such as mesenchymal stem cells, hematopoietic stem cells, neural stem cells, bone marrow stem cells, and reproductive stem cells. The multipotent stem cell is preferably a mesenchymal stem cell. A mesenchymal stem cell broadly means a population of stem cells or precursor cells thereof that can differentiate into all or some of osteoblasts, chondroblasts, and lipoblasts. Mesenchymal stem cells may have the ability to differentiate into erythropoietin-producing cells of the kidney (Transplantation 85: 1654-1658, 2008). Multipotent stem cells can be isolated from a living body by a method known per se. For example, mesenchymal stem cells can be collected from mammalian bone marrow fluid, peripheral blood, umbilical cord blood and the like by a known general method. For example, human mesenchymal stem cells can be isolated by culture and passage of hematopoietic stem cells after bone marrow puncture (Journal of Autoimmunity, 30 (2008) 163-171). Multipotent stem cells can also be obtained by culturing the above-mentioned pluripotent stem cells under appropriate induction conditions.

  The stem cells to be evaluated are preferably ES cells, EG cells, iPS cells, multipotent stem cells (for example, mesenchymal stem cells) and the like.

  Examples of mammals from which stem cells used in the present invention are derived include rodents such as mice, rats, hamsters and guinea pigs, rabbits such as rabbits, ungulates such as pigs, cows, goats, horses and sheep, Examples include cats such as dogs and cats, primates such as humans, monkeys, rhesus monkeys, marmosets, orangutans, chimpanzees, and the like. The established carcinogenicity of stem cells has been reported to be observed in stem cells of large mammals such as dogs and monkeys even though they are not found in mice (Xiao-Bing Zhang, et al. JCI 118; 1502 The method of the present invention is advantageous for the evaluation of ungulate, feline and primate stem cells.

  The method of the present invention is performed, for example, for the purpose of evaluating whether or not the stem cells can be appropriately differentiated into cells constituting a desired tissue prior to performing regenerative medicine of a specific tissue using stem cells. Therefore, the stem cell to be evaluated is a stem cell expected to differentiate in vivo into cells constituting a desired tissue (for example, kidney).

  “Differentiation into cells constituting a desired tissue in vivo” means that when stem cells are transplanted into the desired tissue in vivo or the primordium of the tissue, the stem cells become cells constituting the tissue. It means to differentiate. For example, pluripotent stem cells, etc. are inherently capable of differentiating into all tissues and cells, but when transplanted into in vivo tissues, they do not differentiate into cells constituting the tissues. It is known that teratomas can occur. Using the method of the present invention, when stem cells are transplanted into a living body, whether or not the cells can be appropriately differentiated into cells constituting a desired tissue without forming a tumor such as a teratoma is easily determined. Can be evaluated.

  The type of `` tissue '' is not particularly limited, but for example, kidney, brain, spinal cord, stomach, pancreas, liver, thyroid, bone marrow, skin, muscle, lung, digestive tract (e.g., large intestine, small intestine), Examples include blood vessels, heart, thymus, spleen, peripheral blood, testicles, ovary, placenta, uterus, bone, skeletal muscle and the like.

  “Tissue primordium” refers to a site corresponding to the occurrence of the tissue in a mammalian fetus. For example, metanephron, which is a primordium of the kidney, can be exemplified. Metanephron is located around the ureteric bud germination site of the mammalian fetus, more specifically between the segment and the side plate. The metanephron is preferably a metanephric mesoderm.

  The tissue primordium used in the present invention is usually a tissue primordium in which the stem cells to be evaluated are expected to differentiate. For example, when the stem cells to be evaluated are expected to differentiate into cells that constitute the kidney (for example, erythropoietin-producing cells), the stem cells are transplanted into the kidney primordium. Examples of mammals from which the tissue primordium is derived include those described above. The animal species of the stem cell to be evaluated and the animal species of the tissue primordium may be the same or different. For example, in order to evaluate human stem cells, the stem cells can be transplanted into a primordium of a tissue of a non-human mammal such as a pig or rat.

  The tissue primordium is removed from the mammalian fetus in vitro. Since the metanephric tissue begins to form from E11.5 in the rat and E9.5 in the mouse, the fetus after the stage is usually used when metanephron is used as the tissue primordium. Preferably, it is E14 or later in rats, E12 or later in mice, more preferably E14-16 in rats, and E12-14 in mice. In other mammals, fetuses of the same stage can be preferably used. However, the stages before and after that can also be applied by selecting conditions. Extraction of the tissue primordium from the fetus can be performed using a stereomicroscope or the like.

  Transplantation of stem cells into the tissue primordium is performed using a manipulator, a micropipette, or the like under a stereomicroscope. The number of cells to be transplanted can be set as appropriate based on the size of the tissue primordia, etc. For example, when using rat kidney primordia, about 1000 to 10,000 stem cells are usually injected. Stem cells are usually transplanted into a tissue primordium that has been removed in vitro, but the stem cells are transplanted into a tissue primordium in the fetus of a mammal, and then the stem cell containing the stem cells. The group may be removed from the fetus in vitro. See Yokoo T, et al. J Am Soc Nephrol 17; 1026,2006 etc. for the injection of stem cells into the renal primordium.

  The stem cells to be transplanted are preferably isolated and purified. “Isolated and purified” means that an operation to remove cells other than the target stem cells has been performed. The purity of the stem cell is not particularly limited as long as it can be evaluated by the method of the present invention, but is usually 10% or more, preferably 50% or more, more preferably 80% or more, and most preferably 90% or more (for example, substantially 100%).

  The stem cells to be evaluated are preferably labeled so that they can be distinguished from the cells of the tissue primordia to be transplanted. Examples of the type of label include a fluorescent label, a luminescent label, and a radioisotope label. However, a fluorescent label or a luminescent label is preferable because measurement is simple and detailed analysis is possible. Is most preferred. The stem cells can be labeled by fluorescence or luminescence by introducing a fluorescence-labeled gene or a luminescence-labeled gene into the stem cells. The fluorescent or luminescent labeling gene includes a gene encoding a protein having fluorescence or luminescence, and a gene encoding an enzyme that generates fluorescence or luminescence when mixed with a corresponding fluorescent substrate or luminescent substrate. Examples of the former include genes encoding fluorescent proteins such as GFP, RFP, YFP, CFP, EGFP, and wedge orange. Examples of the latter include genes encoding enzymes such as luciferase, β-galactosidase, and peroxidase. Examples of the luciferase substrate (luminescence) include luciferin (and ATP if necessary). Examples of the substrate (luminescence) of β-galactosidase include luciferin galactoside substrate (6-O-β-galactopyranosyl luciferin). Examples of the substrate for peroxidase include luminol (and hydrogen peroxide if necessary).

  Introduction of a luminescent or fluorescently labeled gene into stem cells can be performed using a genetic engineering technique known per se. For example, stem cells are transfected in vitro with a construct (expression vector) in which the marker gene is operably linked downstream of a promoter capable of functioning in the target cells, and the cells are cultured in an appropriate medium. Thus, the marker gene can be introduced into stem cells.

  Examples of transfection methods include biological methods, physical methods, chemical methods, and the like. Biological methods include, for example, a method using a viral vector, a method using a specific receptor, a cell fusion method (HVJ (Sendai virus), polyethylene glycol (PEG), an electric cell fusion method, micronucleus fusion, and the like. Law (chromosome transfer)). Examples of physical methods include a method using a microinjection method, an electroporation method, and a gene gun (particle gun) method. Examples of the chemical method include calcium phosphate precipitation, lipofection, DEAE-dextran, protoplast, erythrocyte ghost, erythrocyte membrane ghost, and microcapsule.

  Examples of expression vectors include plasmid vectors, PAC, BAC, YAC, viral vectors, retroviral vectors, and the like, which can be appropriately selected.

  The type of promoter is not particularly limited as long as it can induce or promote the expression of the marker gene in the cell into which the marker gene has been introduced. Examples of the promoter include SRα promoter, CMV promoter, PGK promoter, SV40 promoter, ROSA26 and the like.

  The expression vector preferably has a sequence (poly A, generally referred to as a terminator) that terminates transcription of the target mRNA. In addition, splicing signals, enhancer regions, and introns of eukaryotic genes are partly connected 5 ′ upstream of the promoter region, between the promoter region and the translation region, or 3 ′ downstream of the translation region for the purpose of further expressing the marker gene. It is also possible to do. The expression vector further includes a selection marker gene (eg, neomycin resistance gene, hygromycin resistance gene, drug resistance gene such as ampicillin resistance) for selecting a clone in which the introduced marker gene is stably integrated. obtain.

  Alternatively, stem cells extracted from a mammal into which a luminescent or fluorescent labeling gene has been introduced may be used. The mammal can be produced using a genetic engineering technique known per se. For example, fertilized eggs such as mammalian fertilized eggs, unfertilized eggs, sperm and their precursor cells, calcium phosphate coprecipitation method, electroporation method, lipofection method, aggregation method, microinjection (microinjection) Luminescent or fluorescently labeled genes are introduced by introducing a luminescent or fluorescently labeled gene by a gene transfer method such as a method, a gene gun (particle gun) method, or a DEAE-dextran method, and obtaining progeny animals derived from the germ cells. Mammals can be produced.

  When introducing a gene into a germ cell, it is generally advantageous to use a construct (expression vector) in which a target marker gene is linked downstream of a promoter that can function in a target mammalian cell.

  Specifically, an expression vector in which a polynucleotide containing a marker gene is linked downstream of a promoter that can function in the cells of the subject mammal is microinjected into a fertilized egg of the subject mammal, and the like. By transferring the fertilized egg into the uterus of a pseudopregnant animal, a transgenic mammal that highly expresses the marker gene can be produced.

  Examples of expression vectors include plasmid vectors, PAC, BAC, YAC, viral vectors, retroviral vectors, and the like, which can be appropriately selected.

  The type of promoter is not particularly limited as long as it can induce or promote the expression of the marker gene in the mammal into which the marker gene has been introduced. By using a non-tissue-specific promoter as a promoter, a mammal that ubiquitously expresses a luminescent or fluorescently labeled gene can be produced. By using a tissue extracted from this mammal, it is possible to simultaneously evaluate the preservation effect of many types of tissues in a single test. Examples of the tissue non-specific promoter include SRα promoter, CMV promoter, PGK promoter, SV40 promoter, ROSA26, β-actin promoter and the like. In addition, if a tissue-specific promoter is used, a mammal that specifically expresses a luminescent or fluorescently labeled gene in the target tissue can be produced. For example, the marker gene can be expressed in a liver-specific manner by using the α1AT promoter, in a skeletal muscle-specific manner by using the β-actin promoter, and in a nerve-specific manner by using the enolase promoter.

  The expression vector preferably has a sequence (poly A, generally referred to as a terminator) that terminates transcription of the target mRNA. In addition, splicing signals, enhancer regions, and introns of eukaryotic genes are partly connected 5 ′ upstream of the promoter region, between the promoter region and the translation region, or 3 ′ downstream of the translation region for the purpose of further expressing the marker gene. It is also possible to do. The expression vector further includes a selection marker gene (eg, neomycin resistance gene, hygromycin resistance gene, drug resistance gene such as ampicillin resistance) for selecting a clone in which the introduced marker gene is stably integrated. obtain.

Next, the tissue primordium in which the stem cells are transplanted is cultured in vitro. The culture of the tissue primordium can be performed using a normal organ culture technique. For example, add a suitable medium to the dish, float the filter on it, place the tissue primordium on the filter so that the medium is supplied to the tissue primordium through the filter, and leave the dish in the incubator Thus, the tissue primordium can be cultured. As culture conditions, culture conditions usually used in tissue culture techniques can be used. For example, the culture temperature is usually in the range of about 30 to 40 ° C, preferably about 37 ° C. The CO ₂ concentration is usually in the range of about 1 to 10%, preferably about 5%. The humidity is usually in the range of about 70 to 100%, preferably about 95 to 100%. The culture period can be appropriately set without particular limitation as long as it is long enough for evaluation, but is usually about 7 to 14 days when rat kidney primordia are used.

  Then, using the degree of dispersion of the transplanted stem cell-derived cells in the cultured tissue primordia as an index, the possibility that the stem cells can differentiate into cells constituting the tissue in vivo is determined. The degree of dispersion of transplanted stem cell-derived cells can be determined using a microscope or an appropriate imaging apparatus. When stem cells are labeled with fluorescence or the like, a microscope capable of detecting the label or an appropriate imaging apparatus is used. As shown in Examples described later, stem cells that can differentiate into cells constituting the tissue in vivo are dispersed in the tissue primordium along with proliferation, and differentiate into cells constituting the tissue. When stem cells are labeled with fluorescence or the like, cell dispersion can be easily detected as the dispersion of the label. On the other hand, stem cells that cannot differentiate into cells constituting the tissue in vivo and form tumors such as teratomas, do not disperse within the tissue primordium, exhibit a cell mass form, and deform A tumor such as a tumor is formed. As the cells grow, the size of the cell mass increases. When stem cells are labeled with fluorescence or the like, the cell mass can be easily detected as the labeled mass. The above determination is based on such a positive value between the degree (or presence) of the distribution of transplanted stem cell-derived cells in the tissue primordia and the possibility that the stem cells can differentiate into cells constituting the tissue in vivo. Based on correlation.

  That is, if the cells derived from the transplanted stem cells are dispersed with proliferation in the tissue primordium after culturing, it is determined that the stem cells are highly likely to be differentiated into cells constituting the tissue in vivo. I can do it. On the other hand, when cells derived from transplanted stem cells do not disperse in the tissue primordium after culturing and exhibit a cell mass, the stem cells are differentiated into cells constituting the tissue in vivo. Therefore, it can be determined that there is a high possibility of forming a tumor such as a teratoma.

  By using the method of the present invention, for example, it is possible to evaluate whether or not the stem cells can be appropriately differentiated into cells constituting a desired tissue prior to performing regenerative medicine of a specific tissue using stem cells. It is useful for stem cell quality control. In addition, if the method of the present invention is used to perform regenerative medicine using multipotent stem cells or pluripotent stem cells differentiated in vitro from pluripotent stem cells, they are not sufficiently differentiated, such as teratomas It is possible to easily evaluate whether cells having tumor-forming ability are mixed. Furthermore, by using the method of the present invention, it is evaluated whether iPS cells can be differentiated into cells constituting a predetermined tissue, or have been initialized to an undifferentiated state and have a teratoma forming ability. I can do it.

  The present invention also provides a kit for evaluating whether stem cells can be differentiated into cells constituting a desired tissue in vivo. The kit contains a desired tissue primordium (for example, metanephron, etc.) used in the method of the present invention and separated in vitro. The tissue primordium may be frozen in an appropriate tissue preservation solution (eg, ET-Kyoto solution).

  The kit of the present invention can further contain a reagent for labeling the stem cells to be evaluated in the method of the present invention so that they can be distinguished from the cells of the tissue primordia to be transplanted. Examples of the reagent include a fluorescent labeling reagent, a luminescent labeling reagent, and a radioisotope labeling reagent. Examples of the reagent include a combination of an expression vector capable of expressing the above-described fluorescent protein, an expression vector capable of expressing an enzyme, and a fluorescent substrate or a luminescent substrate corresponding to the enzyme. The kit of the present invention can further contain a reagent for transfecting the expression vector into stem cells by the above-described method.

  The kit of the present invention further comprises various reagents and tools used in the method of the present invention (for example, tools for transplanting stem cells into tissue primordia (manipulators, micropipettes, etc.), tissue primordium in vitro. A dish for culturing, a filter, a culture medium, instructions describing the above-described method of the present invention, a microscope capable of detecting a label, an appropriate imaging apparatus, and the like.

  By using the kit of the present invention, it is possible to easily evaluate whether the stem cells can be differentiated into cells constituting a desired tissue in vivo by the method of the present invention.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited at all by the Example shown below.

Example 1
Although stem cells typified by iPS are established by introducing various genes, the carcinogenicity of the established stem cells is observed in stem cells of large animals such as dogs and monkeys even though they are not found in mice. Cases have been reported (Xiao-Bing Zhang, et al. JCI 118; 1502,2008). Therefore, in this test, monkey ES cells labeled with green fluorescent protein (GFP) (Nagata M, et al. J Gene Med 5; 921,2003) and pigs introduced with red fluorescent protein, wedgefly orange ( MSC established from Matsunari H, et al. Cloning Stem Cells 10; 313, 2008) was used.
The monkey ES cells are known to form teratomas when transplanted in vivo, and the porcine MSCs can be differentiated into erythropoietin-producing cells constituting the kidney when transplanted into the renal primordia (Transplantation). 85: 1654-1658, 2008).
Injection of test stem cells into rat fetal kidney primordia was in line with previous reports (Yokoo T, et al. J Am Soc Nephrol 17; 1026, 2006). Specifically, 100-10000 cells (monkey ES cells or porcine MSC) were injected into the rat fetal kidney primordia using a mouse pipette under a stereomicroscope. The kidney primordium after the injection was cultured on a double culture dish with a filter for 10 to 14 days by a conventional method. The cultured kidney primordium was observed under a fluorescence microscope.

  As a result, when the monkey ES cells were transferred, it was confirmed by fluorescence image that the transferred cells became one lump and formed teratomas (FIG. 1). The formation of teratomas was also confirmed by light microscopy (FIG. 2). On the other hand, porcine MSCs dispersed in the kidney primordium without forming a tumor and differentiated into the kidney (FIG. 3).

(Example 2)
A 15-day-old fetal rat was isolated from the pregnant rat, and the kidney primordium was removed from the fetal rat under a stereomicroscope and allowed to stand on a filter in a double culture dish with a filter. On the other hand, a mouse iPS cell established by a previously reported method (Takahashi K, et al. Nature Protocols 12; 2, 2007) was made into a cell suspension of 1,000 to 10,000 cells, and a mouse pipette was used under a stereomicroscope. Were injected into the rat kidney primordium. Rat kidney primordium after cell injection was cultured for 14 days by a conventional method. The cultured kidney primordium was observed under a fluorescence microscope.
As a result, as in the case of ES cells, when mouse iPS cells were transferred, it was confirmed by fluorescence image that the transferred cells became one lump and formed teratomas (FIG. 4).

By using the method of the present invention, stem cells are cells that form tumors such as teratomas in vivo, or cells that can differentiate into various cells without tumor formation in vivo and contribute to normal tissue formation. It is possible to easily test whether it exists.
This application is based on the international application PCT / JP2008 / 073849 (filing date: December 26, 2008), the contents of which are incorporated in full herein.

Claims (6)

A method for evaluating whether a stem cell can be differentiated into a cell constituting a desired tissue in vivo, comprising the following steps:
(1) transplanting stem cells to be evaluated into a primordium of a desired tissue of a non-human mammal,
(2) culturing the tissue primordium in vitro;
(3) Using the degree of dispersion of transplanted stem cell-derived cells in the cultured tissue primordia as an index, the degree of presence or absence of transplanted stem cell-derived cells in the tissue primordium and the stem cells in vivo Determining the possibility that the stem cells can differentiate into cells constituting the tissue in vivo based on a positive correlation with the possibility of differentiation into cells constituting the tissue. In the step (3), in the case where the transplanted stem cell-derived cells are dispersed with proliferation in the cultured tissue primordia, the stem cells are highly likely to be differentiated into cells constituting the tissue in vivo. When the stem cells derived from the transplanted stem cells do not disperse in the tissue primordium after culturing, and exhibit a cell mass aspect, the stem cells differentiate into cells constituting the tissue in vivo. The method according to claim 1, wherein the method is determined to be unfavorable and likely to form a tumor. The method according to claim 1 or 2 , wherein the stem cells to be evaluated are labeled so as to be distinguishable from the cells of the tissue primordium to be transplanted. The method of claim 3 , wherein the label is a fluorescent label. The method according to any one of claims 1 to 4 , wherein the tissue is a kidney. The method according to any one of claims 1 to 5 , wherein the stem cell is a mesenchymal stem cell.