Can TGF-beta1 and rhBMP-2 act in synergy to transform bone marrow stem cells to discogenic-type cells?
BACKGROUND
The recombinant human bone morphogenic protein-2 (rhBMP-2) is known to increase the proteoglycan production and chondrogenic gene expression in the disc cells. The transforming growth factor-beta 1 (TGF-beta(1)) can transform the bone marrow stem cells (BMDCs) into the disc-like cells.


METHODS
We carried out an experiment to determine if TGF-beta(1) and rhBMP-2 can act in synergy on BMDCs by increasing the production of sulfated-glycosaminoglycan (sGAG) and affecting the mRNA expression of aggrecan, type I collagen, and type II collagen. The BMDCs were isolated from the iliac crest and femur of a New Zealand white rabbit (1 year). The BMDCs were culured in monolayer and treated for 6 days with TGF-beta(1) 10 ng/ml (group 1), rhBMP-2 200 ng/ml (group 2), and both TGF-beta(1) 10 ng/ml and rhBMP-2 200 ng/ml (group 3: the combined group) in Dulbecco's modified Eagle medium/F-12 with 1% fetal bovine serum. After 6 days, the sGAG content in the media was quantified using 1,9-dimethylmethylene blue staining and the mRNA expression of aggrecan, type I collagen, type II collagen, Sox-9, BMP-2, and BMP-7 were measured with the real-time PCR. The same BMDCs were also cultured in the chamber slide at 3 x 10(4) cells/chamber. After 6 days treatment, the treated cells were immunofluorescence stained with aggrecan, type I collagen, type II collagen, anti-BMP-2, anti-BMP-7 antibodies. After that, we compared the number of positive immunofluorescence stained cells with fluorescence microscope. The sGAG production and mRNA expression for each group were normalized against the same parameters for a non-treatment group.


CONCLUSIONS
The sGAG production was increased 1.15*, 1.34*, and 1.45* times in the TGF-beta(1) 10 ng/ml group, the rhBMP-2 200 ng/ml group, and the combined group respectively. The mRNA expression of aggrecan was increased 1.28, 3.42*, and 5.34* times, the mRNA expression of type I collagen was increased 0.86, 1.09, 1.17 times, the mRNA expression of type II collagen was increased 3.58*, 3.77*, and 10.78* times, the mRNA expression of Sox-9 was increased 1.29, 2.45, 2.75* times, the mRNA expression of BMP-2 was increased 1.14, 2.07, 4.43* times, and the mRNA expression of BMP-7 was increased 1.16, 1.49, 1.97* times, respectively for each group (* indicates p < 0.05). On the immunofluorescence staining of antibodies, the average positively immunofluorescence stained cells number for aggrecan were 4.2, 15.8*, 10*, and 22* according to the non-treatment group, TGF-beta(1) 10 ng/ml group, rhBMP-2 200 ng/ml group, and the combined group respectively. The average positively immunofluorescence stained cells number for type I collagen were 7, 14.2*, 9.2*, 17.4* and the average positively immunofluorescence stained cells number for type II collagen were 8.5, 28.25*, 20.25*, 42.25* and the average positively immunofluorescence stained cells number for anti-BMP-2 were 5, 16.75*, 8.75*, 27.25* and the average positively immunofluorescence stained cells number for anti-BMP-7 were 3.25, 7.5*, 8.75*, 15.25* (* indicates p < 0.05).


CONCLUSIONS
Both TGF-beta(1) and rhBMP-2 alone, can increase proteoglycan production in the BMDCs. However, if they were used in combination, there is a synergistic effect. Similarly, the mRNA expressions of both aggrecan, type II collagen, Sox-9, BMP-2, and BMP-7 except for type I collagen were increased significantly when TGF-beta(1) and rhBMP-2 were combined. The positive immunofluorescence stained cell numbers for aggrecan, type I, II collagen, BMP-2 and BMP-7 were also increased after each TGF-beta(1) and rhBMP-2 treatment, and also more increased significantly in the aggrecan, type I, II collagen, BMP-2, and 7 when they were used jointly.
Kuh
Sung Uk
SU
Department of Neurosurgery, The Spine and Spinal cord Institute, Yonsei University Medical College, Seoul, Korea.
Zhu
Yerun
Y
Li
Jun
J
Tsai
Kai-Jow
KJ
Fei
Qinming
Q
Hutton
William C
WC
Yoon
S Tim
ST
D053674:Aggrecans / Q000235:genetics; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D016026:Bone Marrow Transplantation / Q000379:methods; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology* / Q000627:therapeutic use; D055419:Bone Morphogenetic Protein 7 / Q000235:genetics; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D020219:Chondrogenesis / Q000187:drug effects* / Q000502:physiology; D024042:Collagen Type I / Q000235:genetics; D024043:Collagen Type II / Q000235:genetics; D004357:Drug Synergism; D006025:Glycosaminoglycans / Q000096:biosynthesis; D007403:Intervertebral Disc / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007405:Intervertebral Disc Displacement / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000494:pharmacology / Q000627:therapeutic use; D012038:Regeneration / Q000187:drug effects / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology* / Q000627:therapeutic use
D053674:Aggrecans; C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D055419:Bone Morphogenetic Protein 7; D024042:Collagen Type I; D024043:Collagen Type II; D006025:Glycosaminoglycans; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D053773:Transforming Growth Factor beta1