ASTM F2131-02(2007)e1
(Test Method)Standard Test Method forIn Vitro Biological Activity of Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) Using the W-20 Mouse Stromal Cell Line
Standard Test Method for<bdit>In Vitro</bdit> Biological Activity of Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) Using the W-20 Mouse Stromal Cell Line
SIGNIFICANCE AND USE
Although the test method can be used for assessment of the bioactivity of crude preparations of rhBMP-2, it has only been validated for use with highly pure (>98 % by weight protein purity) preparations of rhBMP-2.
SCOPE
1.1 This test method describes the method used and the calculation of results for the determination of the in-vitro biological activity of rhBMP-2 using the mouse stromal cell line W-20 clone 17 (W-20-17). This clone was derived from bone marrow stromal cells of the W++ mouse strain.
1.2 This test method (assay) has been qualified and validated based upon the International Committee on Harmonization assay validation guidelines (with the exception of interlaboratory precision) for the assessment of the biological activity of rhBMP-2. The relevance of this in vitro test method to in vivo bone formation has also been studied. The measured response in the W-20 bioassay, alkaline phosphatase induction, has been correlated with the ectopic bone-forming capacity of rhBMP-2 in the in vivo Use Test (UT). rhBMP-2 that was partially or fully inactivated by targeted peracetic acid oxidation of the two methionines was used as a tool to compare the activities. Oxidation of rhBMP-2 with peracetic acid was shown to be specifically targeted to the methionines by peptide mapping and mass spectrometry. These methionines reside in a hydrophobic receptor binding pocket on rhBMP-2. Oxidized samples were compared alongside an incubation control and a native control. The 62, 87, 98, and 100 % oxidized samples had W-20 activity levels of 62, 20, 7, and 5 %, respectively. The incubation and native control samples maintained 100 % activity. Samples were evaluated in the UT and showed a similar effect of inactivation on bone-forming activity. The samples with 62 % and 20 % activity in the W-20 assay demonstrated reduced levels of bone formation, similar in level with the reduction in W-20 specific activity, relative to the incubation control. Little or no ectopic bone was formed in the 7 and 5 % active rhBMP-2 implants.
1.3 Thus, modifications to the rhBMP-2 molecule in the receptor binding site decrease the activity in both the W-20 and UT assays. These data suggest that a single receptor binding domain on rhBMP-2 is responsible for both in-vitro and in-vivo activity and that the W-20 bioassay is a relevant predictor of the bone-forming activity of rhBMP-2.
1.4 The values stated in SI units are to be regarded as standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: F2131 − 02(Reapproved 2007)
Standard Test Method for
In Vitro Biological Activity of Recombinant Human Bone
Morphogenetic Protein-2 (rhBMP-2) Using the W-20 Mouse
Stromal Cell Line
This standard is issued under the fixed designation F2131; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Formatting and grammar were corrected editorially throughout in April 2007.
1. Scope incubation and native control samples maintained 100% ac-
tivity. Samples were evaluated in the UTand showed a similar
1.1 This test method describes the method used and the
effect of inactivation on bone-forming activity. The samples
calculation of results for the determination of the in-vitro
with 62% and 20% activity in the W-20 assay demonstrated
biological activity of rhBMP-2 using the mouse stromal cell
reduced levels of bone formation, similar in level with the
line W-20 clone 17 (W-20-17). This clone was derived from
2 reduction in W-20 specific activity, relative to the incubation
bone marrow stromal cells of the W++ mouse strain.
control. Little or no ectopic bone was formed in the 7 and 5%
1.2 This test method (assay) has been qualified and vali-
active rhBMP-2 implants.
dated based upon the International Committee on Harmoniza-
1.3 Thus, modifications to the rhBMP-2 molecule in the
tion assay validation guidelines (with the exception of inter-
receptorbindingsitedecreasetheactivityinboththeW-20and
laboratory precision) for the assessment of the biological
UT assays. These data suggest that a single receptor binding
activity of rhBMP-2.The relevance of this in vitro test method
domainonrhBMP-2isresponsibleforboth in-vitroand in-vivo
to in vivo bone formation has also been studied.The measured
activity and that the W-20 bioassay is a relevant predictor of
responseintheW-20bioassay,alkalinephosphataseinduction,
the bone-forming activity of rhBMP-2.
has been correlated with the ectopic bone-forming capacity of
rhBMP-2 in the in vivo Use Test (UT). rhBMP-2 that was 1.4 The values stated in SI units are to be regarded as
partially or fully inactivated by targeted peracetic acid oxida- standard.
tion of the two methionines was used as a tool to compare the
1.5 This standard does not purport to address all of the
activities. Oxidation of rhBMP-2 with peracetic acid was
safety concerns, if any, associated with its use. It is the
showntobespecificallytargetedtothemethioninesbypeptide
responsibility of the user of this standard to establish appro-
mappingandmassspectrometry.Thesemethioninesresideina
priate safety and health practices and determine the applica-
hydrophobic receptor binding pocket on rhBMP-2. Oxidized
bility of regulatory limitations prior to use.
samples were compared alongside an incubation control and a
nativecontrol.The62,87,98,and100%oxidizedsampleshad
2. Terminology
W-20 activity levels of 62, 20, 7, and 5%, respectively. The
2.1 rhBMP—recombinant human bone morphogenetic pro-
tein.
ThistestmethodisunderthejurisdictionofASTMCommitteeF04onMedical
2.2 GDF—growth and differentiation factor.
andSurgicalMaterialsandDevicesandisthedirectresponsibilityofSubcommittee
F04.42 on Biomaterials and Biomolecules for TEMPs.
3. Summary of Test Method
Current edition approved Feb. 1, 2007. Published February 2007. Originally
approved in 2002. Last previous edition approved in 2002 as F2131–02. DOI:
3.1 Inthistestmethod,themousestromalcelllineW-20-17
10.1520/F2131-02R07E01.
is used as a target cell line for rhBMP-2. The W-20-17 cells
Thies, R. S., Bauduy, M., Ashton, B. A., Kurtzberg, L., Wozney, J.M., and
exhibit increased alkaline phosphatase activity in response to
Rosen, V., “Recombinant Human Bone Morphogenetic Protein-2 Induces Osteo-
blastic Differentiation in W-20-17 Stromal Cells,” Endocrinology, 130, 1992, pp.
rhBMP-2. Optical density at 405 nm of the p-nitrophenol
1318-1324.
generated from the alkaline phosphatase substrate is used as a
Guideline for Industry, ICH-Q2AText on Validation ofAnalytical Procedures,
measure of alkaline phosphatase enzyme level. The test
November 1996, International Committee on Harmonization, March 1995, http://
www.fda.gov/cder/guidance/index/htm. method is performed in a 96-well plate format. A similar test
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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F2131 − 02 (2007)
methodbaseduponthesamecelllinehasbeendevelopedusing 7. Reagents and Materials
chemiluminescent detection of alkaline phosphatase. 5
7.1 W-20-17 Mouse Stromal Cells.
4. Significance and Use 7.2 Dulbecco’s modified Eagle’s medium with 4500 mg/L
glucose and 4.0 mM L-glutamine, without sodium bicarbonate
4.1 Although the test method can be used for assessment of
(DME/High, JRH Biosciences, 56439 or equivalent).
the bioactivity of crude preparations of rhBMP-2, it has only
been validated for use with highly pure (>98% by weight
7.3 Sodium bicarbonate (Sigma—Aldrich S4019 or equiva-
protein purity) preparations of rhBMP-2.
lent).
7.4 5 M hydrochloric acid.
5. Interferences
7.5 Heat inactivated (Hi) fetal bovine serum (FBS).
5.1 There have been no systematic studies of interfering
NOTE 1—Each new lot of fetal bovine serum must be evaluated in the
substances for this test method. There is anecdotal evidence
assay before use.
that trypsin and some rhBMP-2 formulation buffers can inter-
fere with the assay. Additionally, the source of fetal bovine 7.6 200 mM L-Glutamine (Invitrogen Life Technologies,
25030081 or equivalent).
serum is an important variable. Each lot should be tested in all
parts of the assay where it is required to determine the
7.7 Gentamicin Gibco sterile filtered: 10 mg/mL or equiva-
appropriatenessofthelot.Thisisparticularlyimportantiffetal
lent.
bovine serum vendor is changed.
7.8 Penicillin Streptomycin (PS), contains 10 000 units of
6. Apparatus penicillin(base)/mLand10000µgofstreptomycin(base)/mL,
utilizing penicillin G (sodium salt) and streptomycin sulfate in
6.1 Polypropylene conical tubes, 15 mL and 50 mL.
0.85 % saline (Invitrogen Life Technologies, #15140122 or
6.2 Cryovials (Corning or equivalent), sterile 2 mL.
equivalent).
6.3 Eppendorf vials, sterilized.
7.9 Phosphate Buffered Saline, Calcium and Magnesium
6.4 Variable pipets,(range20to1000µL)and Multichannel
Free, 1x (PBS-CMF), (Invitrogen Life Technologies (cat.
pipets (range 50 to 300 µL).
#20012050 or equivalent).
6.5 Biosafety cabinet.
7.10 Dimethyl sulfoxide (DMSO), cell culture grade
(Sigma-Aldrich or equivalent).
6.6 96 Well flat bottom sterile tissue culture microtiter
plates, (Falcon 3072 or equivalent).
7.11 Trypsin-EDTA(0.05%trypsin,0.53mMEDTA·4Na)
(1X), liquid (Invitrogen Life Technologies 25300054 or
6.7 IEC Centra-7R Centrifuge, or equivalent.
equivalent).
6.8 CO humidified tissue culture incubator.
7.12 Glycine (Sigma —Aldrich or equivalent).
6.9 Spectrophotometric microplate reader, (VMAX/
Spectramax, Molecular Devices, or equivalent).
7.13 Sodium Hydroxide (NaOH) 0.2 N and 10 N.
6.10 Hemacytometer, or automatic cell counter.
7.14 Triton X-100 (J.T. Baker Cat. No. X198-05 or equiva-
lent).
6.11 Inverted microscope.
7.15 Magnesium Chloride, Crystalline (MgCl ·6H O).
6.12 Tissue culture flasks, Falcon T175 or equivalent.
2 2
6.13 Sterilized paper towels, or equivalent. 7.16 p-Nitrophenol phosphate (PNPP, Sigma—Aldrich
104(R) phosphatase substrate, product # 1040 or equivalent).
6.14 Sterile filter units, (0.2 µm).
7.17 NaCl.
6.15 Sterile pipets, (1 mL, 5 mL, 10 mL, 25 mL, 50 mL).
7.18 Purified water.
6.16 9 in. Pasteur pipets, sterilized.
6.17 Sterilized pipet tips, (1-300 µL and 200-1000 µL).
6.18 Sterile reagent reservoirs.
This cell line has been deposited in mid-2001 at the American Type Culture
Collection, 10801 University Blvd., Manassas, VA 20110-2209, U.S., http://
6.19 −80°C freezer.
www.atcc.org.
6.20 96 Well U-Bottom polypropylene sterile tissue culture
Thismediumhasbeenfoundsatisfactoryforthispurposeandisavailablefrom
JRHBiosciences,P.O.Box14848,Lenexa,KS66215,U.S.,http://www.jrhbio.com.
microtiter plates, (Costar 3790 or equivalent).
6.21 Water bath.
Thismaterialhasbeenfoundsatisfactoryforthispurposeandisavailablefrom
Sigma-Aldrich Corp., 3050 Spruce St., St. Louis, MO 63103, U.S., http://
6.22 Orbital shaker.
www.sigmaaldrich.com.
Thismaterialhasbeenfoundsatisfactoryforthispurposeandisavailablefrom
Invitrogen Life Technologies, 1600 Faraday Ave., P.O. Box 6482, Carlsbad, CA
Blum, R. S., Li, R. H., Mikos,A.G., and Barry, M.A., “An Optimized Method 92008, U.S., http://www.invitrogen.com.
for the Chemiluminescent Detection of Alkaline Phosphatase Levels During Thismaterialhasbeenfoundsatisfactoryforthispurposeandisavailablefrom
Osteodifferentiation by Bone Morphogenetic Protein 2,” Jour. Cellular Biochem., J.T.Baker,(MallinckrodtBaker,Inc.),222RedSchoolLn.,Phillipsburg,NJ08865,
80, 2001, pp. 532-537. U.S., http://www.jtbaker.com.
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F2131 − 02 (2007)
7.19 rhBMP-2, 1st WHO Reference Reagent 1997 (5000 8.1.6.1 Mix 12.5 mL Triton X-100 with 87.5 mL of 0.9%
Units per ampoule, cat. # 93/574, National Institute for NaCl.
Biological Standards and Control).
8.1.6.2 Filterthrougha0.2µmfilterandstoreinasterilized
container at room temperature.
7.20 rhBMP-2 internal control, >1 mg/mL (stored at
8.1.7 Freezing Medium:
−80°C).
8.1.7.1 Prepare freezing medium immediately before the
freezing procedure by adding DMSO to growth medium (see
8. Procedure
9.1.3) to 20% v/v.
8.1 Solution Preparation:
Component Proportion (% v/v) Example: 100 mL
8.1.1 DME Low Bicarb:
Growth Medium 80 80 mL
8.1.1.1 Dissolve 66.87 g DME/High and 11.13 g sodium
DMSO 20 20 mL
bicarbonate in 4.5 L of purified water.
8.1.8 Glycine Buffer:
8.1.1.2 AdjustthepHto7.3 60.10with5MHClandbring
8.1.8.1 Dissolve0.75%(w/v)glycineinrequiredvolumeof
solution to 5 L with purified water.
purifiedwater.AdjustthepHofthesolutionto10.3 60.1with
8.1.1.3 Filter through a 0.2 µm filter into sterile bottles.
10 N NaOH.
8.1.1.4 Store at 2 to 8°C. The solution expires in 8 weeks.
8.1.8.2 Add 0.8% (v/v) of 12.5% Triton X-100.
8.1.2 Hi FBS:
8.1.8.3 Add 0.13% (w/v) MgCl ·6H O and mix well.
2 2
8.1.2.1 Thaw the desired amount of FBS at ambient
Component Example: 1000 mL
temperature, or 2 to 8°C.
Glycine 7.5 g
8.1.2.2 Adjust the water bath to a temperature of 56 6 2°C.
MgCl ·6H O 1.3 g
2 2
8.1.2.3 Place the bottle of FBS into the water bath so that
12.5 % Triton X-100 8.0 mL
Water To 1000 mL
the entire contents of the bottle are immersed in water.
8.1.2.4 Heat the bottle for 45 min, swirling periodically.
8.1.8.4 Filter through a 0.2 µm filter and store in a sterile
8.1.2.5 Remove the bottle from the water bath and allow to
container at room temperature. The solution has a one month
cool to room temperature.Aliquot 50 mLof the FBS in sterile
expiration.
50-mL conical tubes.
8.1.9 Assay Mix:
8.1.2.6 Label each container with name, lot number, expi-
8.1.9.1 Take a sufficient volume of the glycine buffer to
rationdate,andtheheatinactivationdate.Storeat−20 610°C
coverdevelopingneeds(thatis,5mLglycinebufferperplate).
or 2 to 8°C.
8.1.9.2 Add 0.34% (w/v) p-nitrophenol phosphate within
8.1.3 Growth Medium:
one (1) h of use and mix well.
8.1.3.1 Combine the following components in the corre-
NOTE 2—The assay mix must be made on day of use.
sponding proportions (v/v):
Component Example: 50 mL for 10 plates
Component Proportion (% v/v) Example: 500 mL (mL)
Glycine buffer 50 mL
DME Low Bicarb 85.5 427.5
PNPP substrate 170 mg
Hi FBS 10.0 50.0
L-Glutamine (200 mM) 4.0 20.0
8.2 Cell Line Storage and Cell Banking Procedure:
Gentamicin 0.5 2.5
8.2.1 Store the cells in 1 mLaliquots in 2 mLcryovials at 5
8.1.3.2 Filter through a 0.2 µm filter and store at 2 to 8°C in 5
×10 cells/mL in freezing medium (see 8.1.7).
a sterile container.
8.2.2 Prepare cells to make a working cell bank (100+
8.1.4 Assay Medium:
vials).
8.1.4.1 Combine the following components in the corre-
8.2.3 Thaw the vial of W-20-17 cells obtained from ATCC
sponding proportions (v/v):
or other source following the procedure described in 8.3.
Component Proportion (% v/v) Example: 1000 mL (mL)
8.2.4 Inordertoobtaintheexpectedcellnumber,subculture
DME Low Bicarb 87.0 870.0
the cells by expanding them through one or two additional
Hi FBS 10.0 100.0
L-Glutamine (200 mM) 2.0 20.0
passages (repeat steps in 8.3).
Penicillin/streptomycin 1.0 10.0
NOTE 3—The viability should be in the range ≥80%.
8.1.4.2 Filter through a 0.2 µm filter and store at 2 to 8°C in
a sterile container. 8.2.5 Determine the number of vials to be made based on
8.1.5 NaCl, 0.9 % w/v:
totalcellnumberobtainedfollowingprocedure8.2.2.Labelthe
8.1.5.1 Dissolve 9 g NaCl in approximately 800 mL of appropriate number of cryovials as follows:
purified water and bring to a final volume of 1 Lwith purified
Cell Line Name WCB
Passage Number
water.
Freezing Date
8.1.5.2 Filter through a 0.2 µm filter and store in a sterile
Preparation Reference Number
container at room temperature.
Initials
8.1.6 12.5 % Triton X-100:
8.2.6 Decap the cryovials in the biosafety cabinet.
8.2.7 Dilute the cell suspension to one half the appropriate
volume with 2 to 8°C cold freezing medium without DMSO.
Thismaterialhasbeenfoundsatisfactoryforthispurposeandisavailablefrom
Volume should be one half of the appropriate volume for the
the National Institute for Biological Standards and Control (NIBSC), Blanche Ln.,
South Mimms, Potters Bar, Herts, EN6 3QG, U.K., http://www.nibsc.ac.uk. desired cell suspension for freezing. The second half of the
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F2131 − 02 (2007)
cold freezing medium should be made with culture medium 8.3.6 Place the flasks in a 37 6 2°C, 5 6 0.5% CO
(see 8.1.7, 20% DMSO).The final DMSO concentration must humidified incubator for 4 days.
be 10%.
NOTE 6—A final volume of 30 mL per T175 flask is required.
8.2.8 Slowly add the half-volume of culture medium with
NOTE 7—Do not prepare partial flasks, that is, less than2×10
cells/flask.
20% DMSO to the other half of the volume of the cell
suspension.
8.4 Plating of Cells:
8.2.9 Using a sterile pipet, transfer 1 mLof cell suspension 8.4.1 After 4 days, aspirate the medium from the flasks.
toeachofthelabeledcryovialsonice.Repeatuntilallvialsare
8.4.2 Add 10 mLPBS-CMF to each flask; swirl and lay the
filled. Gently mix the cell suspension during the filling process flasks flat to cover the monolayer. Remove the PBS-CMF.
to prevent settling of the cells.
8.4.3 Add 10 mL trypsin t
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