Related Experiment Videos
Role of BMP-2 and OP-1 (BMP-7) in programmed cell death and skeletogenesis during chick limb development
D Macias1, Y Gañan, T K Sampath
1Departamento de Ciencias Morfológicas, Universidad de Extremadura, Badajoz, Spain.
Abstract:
Bone Morphogenetic Protein 2 (BMP-2) and Osteogenic Protein 1 (OP-1, also termed BMP-7) are members of the transforming growth factor beta superfamily. In the present study, we have analyzed the effects of administering them locally at different stages and locations of the chick limb bud using heparin beads as carriers. Our results show that these BMPs are potent apoptotic signals for the undifferentiated limb mesoderm but not for the ectoderm or the differentiating chondrogenic cells. In addition, they promote intense radial growth of the differentiating cartilages and disturb the formation of joints accompanied by alterations in the pattern of Indian hedgehog and ck-erg expression. Interestingly, the effects of these two BMPs on joint formation were found to be different. While the predominant effect of BMP-2 is alteration in joint shape, OP-1 is a potent inhibitory factor for joint formation. In situ hybridizations to check whether this finding was indicative of specific roles for these BMPs in the formation of joints revealed a distinct and complementary pattern of expression of these genes during the formation of the skeleton of the digits. While Op-1 exhibited an intense expression in the perichondrium of the developing cartilages with characteristic interruptions in the zones of joint formation, Bmp-2 expression was a positive marker for the articular interspaces. These data suggest that, in addition to the proposed role for BMP-2 and OP-1 in the establishment of the anteroposterior axis of the limb, they may also play direct roles in limb morphogenesis: (i) in regulating the amount and spatial distribution of the undifferentiated prechondrogenic mesenchyme and (ii) in controlling the location of the joints and the diaphyses of the cartilaginous primordia of the long bones once the chondrogenic aggregates are established.
Insights
Bone Morphogenetic Proteins (BMPs) like BMP-2 and OP-1 regulate chick limb development by influencing cell death, cartilage growth, and joint formation, revealing distinct roles in limb morphogenesis.
Area of Science:
- Developmental Biology
- Molecular Biology
- Regenerative Medicine
Background:
- Bone Morphogenetic Proteins (BMPs) are crucial signaling molecules in the transforming growth factor beta superfamily.
- BMP-2 and Osteogenic Protein 1 (OP-1, also BMP-7) are implicated in skeletal development.
- Their precise roles in limb bud morphogenesis require further elucidation.
Purpose of the Study:
- To investigate the localized effects of BMP-2 and OP-1 on chick limb bud development at different stages and locations.
- To determine the specific roles of BMP-2 and OP-1 in chondrogenesis, joint formation, and limb patterning.
- To understand the differential impact of BMP-2 and OP-1 on limb morphogenesis.
Main Methods:
- Local administration of BMP-2 and OP-1 using heparin beads in chick limb buds.
- Analysis of cell apoptosis, cartilage growth, and joint formation.
- In situ hybridization to examine gene expression patterns (Indian hedgehog, ck-erg, Bmp-2, Op-1).
Main Results:
- BMPs induced apoptosis in undifferentiated mesoderm but not in ectoderm or differentiating chondrocytes.
- BMPs promoted radial growth of cartilage and disrupted joint formation, with differential effects between BMP-2 and OP-1.
- Distinct expression patterns of Bmp-2 and Op-1 were observed in developing digit skeletons, highlighting complementary roles in joint and bone development.
Conclusions:
- BMP-2 and OP-1 play direct roles in limb morphogenesis beyond axial patterning.
- These BMPs regulate mesenchyme distribution and chondrogenic aggregate formation.
- They control joint positioning and the development of long bone diaphyses during skeletal formation.