Hypertrophy is induced during the in vitro chondrogenic differentiation of human mesenchymal stem cells by bone morphogenetic protein-2 and bone morphogenetic protein-4 gene transfer.
BACKGROUND
The present study compares bone morphogenetic protein (BMP)-4 and BMP-2 gene transfer as agents of chondrogenesis and hypertrophy in human primary mesenchymal stem cells (MSCs) maintained as pellet cultures.


METHODS
Adenoviral vectors carrying cDNA encoding human BMP-4 (Ad.BMP-4) were constructed by cre-lox combination and compared to previously generated adenoviral vectors for BMP-2 (Ad.BMP-2), green fluorescent protein (Ad.GFP), or firefly luciferase (Ad.Luc). Cultures of human bone-marrow derived MSCs were infected with 5 x 10(2) viral particles/cell of Ad.BMP-2, or Ad.BMP-4, seeded into aggregates and cultured for three weeks in a defined, serum-free medium. Untransduced cells or cultures transduced with marker genes served as controls. Expression of BMP-2 and BMP-4 was determined by ELISA, and aggregates were analyzed histologically, immunohistochemically, biochemically and by RT-PCR for chondrogenesis and hypertrophy.


RESULTS
Levels of BMP-2 and BMP-4 in the media were initially 30 to 60 ng/mL and declined thereafter. BMP-4 and BMP-2 genes were equipotent inducers of chondrogenesis in primary MSCs as judged by lacuna formation, strong staining for proteoglycans and collagen type II, increased levels of GAG synthesis, and expression of mRNAs associated with the chondrocyte phenotype. However, BMP-4 modified aggregates showed a lower tendency to progress towards hypertrophy, as judged by expression of alkaline phosphatase, annexin 5, immunohistochemical staining for type X collagen protein, and lacunar size.


CONCLUSIONS
BMP-2 and BMP-4 were equally effective in provoking chondrogenesis by primary human MSCs in pellet culture. However, chondrogenesis triggered by BMP-2 and BMP-4 gene transfer showed considerable evidence of hypertrophic differentiation, with, the cells resembling growth plate chondrocytes both morphologically and functionally. This suggests caution when using these candidate genes in cartilage repair.
Orthopaedic Center for Musculoskeletal Research, Orthopaedic Clinic, König-Ludwig-Haus, Julius-Maximilians-University, Brettreichstrasse 11, 97074 Würzburg, Germany. a-steinert.klh@mail.uni-wuerzburg.de
Andre F
AF
Steinert
Benedikt
B
Proffen
Manuela
M
Kunz
Christian
C
Hendrich
Steven C
SC
Ghivizzani
Ulrich
U
Nöth
Axel
A
Rethwilm
Jochen
J
Eulert
Christopher H
CH
Evans
D017209:Apoptosis / Q000502:physiology; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics* / Q000378:metabolism; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics*; D019902:Chondrocytes / Q000166:cytology* / Q000378:metabolism; D020219:Chondrogenesis / Q000235:genetics*; D018014:Gene Transfer Techniques; D006801:Humans; D006984:Hypertrophy; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D059630:Mesenchymal Stem Cells; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014161:Transduction, Genetic; D019076:Transgenes
C525718:BMP2 protein, human; C525809:BMP4 protein, human; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4