Bone Morphogenetic Proteins - Function, Types, Clinical Use, and Drawbacks

Introduction

Bone morphogenetic proteins are a growth factor from a transforming growth factor beta (TGFbeta) family. It has an essential role in human cellular functions and embryonic development. The group of growth factors is also known as metabolites and cytokines. Bone morphogenetic proteins can induce bone and cartilage formation in the embryo. Bone morphogenetic proteins do cell regulation, differentiation, morphogenesis, apoptosis, and proliferation of various types of cells all over the body. Some studies and research have shown a bioactive factor in the demineralized Matrix of bone, which is responsible for stimulating bone formation. The bioactive factor accountable for inducing bone formation is bone morphogenetic proteins(BMPs). It has a unique activity in the demineralized bone matrix that stimulates the heterotopic bone formation in the non-skeletal tissues like subcutaneous tissues and skeletal muscles.

What Are the Functions of Bone Morphogenetic Proteins?

• The bone morphogenetic proteins interact with the specialized receptors on the cell's surface called bone morphogenetic protein receptors (BMP receptors). Signal transduction through bone morphogenetic receptors results in mobilizing SMAD members of proteins.

• Thus the signaling pathway that involves bone morphogenetic protein, bone morphogenetic protein receptors, and SMADs plays an essential role in the central nervous system, cartilage, heart, and postnatal bone development.

• These bone morphogenetic proteins, bone morphogenetic protein receptors, and SMADs also play an essential role in patterning embryos and early skeletal formation.

• The bone morphogenetic protein four and its inhibitors chordin and noggin help regulate the embryo's back and front patterning, which means the polarity of the embryo.

• Disruption in the signaling of bone morphogenetic protein may affect the body parts of the developing embryo.

• Mutation in the bone morphogenetic proteins and their inhibitors can cause skeletal disorders.

• The primary function of bone morphogenetic protein is to induce the osteoblast to produce native cartilage or bone.

What Are the Types of Bone Morphogenetic Proteins?

Researchers have studied that there are more bone morphogenetic proteins in the human species. So these bone morphogenetic proteins were described under many names, including cartilage-derived morphogenetic proteins, osteogenic proteins, osteogenic, GDFs, and Vg-related. On the structural homology, the bone morphogenetic proteins may be classified into many subgroups, which include:

• BMP 1 - The bone morphogenetic protein 1 does not belong to the transforming growth factor beta(TGFbeta) family. BMP 1 is a metalloprotease that has a role in procollagen 1, 2, and 3. The primary function of bone morphogenetic protein 1 is the development of cartilage.

• BMP 2 - The critical role of bone morphogenetic protein 2 is that it acts as a disulfide-linked homodimer which induces cartilage and bone formation. It also plays an essential role in osteoblast differentiation.

• BMP 3 - Though its essential function is not yet studied, it is believed to also play an important role in inducing bone formation.

• BMP 4 - The bone morphogenetic protein 4 regulates the formation of limbs, bone, and teeth from mesoderm. This type of bone morphogenetic protein also plays a vital role in fracture repair, ovarian follicular development, dorsal central axis formation, and epidermis formation.

• BMP 5 - The bone morphogenetic protein 5 induces the formation of cartilages.

• BMP 6 - The critical role of bone morphogenetic protein 6 is maintaining the integrity of joints in adults. It also controls iron homeostasis by regulating the hepcidin.

• BMP 7 - The bone morphogenetic protein 7 plays a crucial role in osteoblast differentiation and is essential in kidney development and repair.

• BMP 8 - It plays an essential role in cartilage and bone development.

• BMP 10 - This bone morphogenetic protein plays a role in the trabeculation of the heart in the embryo.

• BMP 11 - This bone morphogenetic protein controls the anterior-posterior patterning of the limbs in the embryo.

• BMP 15 - This bone morphogenetic protein plays a vital role in follicular and oocyte development.

What Is the Clinical Use of Bone Morphogenetic Proteins?

• The bone morphogenetic proteins have several applications in oral and maxillofacial surgery.

• Bone morphogenetic proteins help to reconstruct the entirely or partially dissected mandible.

• Bone morphogenetic proteins are used in facial clefts, alveolar ridge augmentation, cleft palate, oral implants, and TMJ cartilage repair.

• In some surgeries, bone morphogenetic proteins help induce osteoblasts and involve forming bone deposits on the native sites.

• It helps in bone regeneration, differentiation, and induction which can form cartilage or bone in the native sites.

• Thus bone morphogenetic proteins help in the reconstruction of bone during surgeries.

What Are the Drawbacks of Bone Morphogenetic Protein?

• The bone morphogenetic proteins should not be used in spinal fusion, that is, anterior cervical fusion, as it can cause soft tissue swelling, resulting in life-threatening complications due to pressure on the respiratory tract and swallowing difficulty.

• Bone morphogenetic proteins are an expensive procedure than other bone graft procedures.

• A lack of understanding of how bone morphogenetic proteins work is a significant disadvantage. It also has the drawback that its side effects have yet to be discovered. These bone morphogenetic proteins are usually prescribed in pharmacological doses.

Conclusion

Bone morphogenetic proteins play a vital role in embryonic development and the surgical procedures of the bone with high success rates. Doctors perform various bone reconstruction procedures like non-vascularized bone grafts and vascularized free flaps. Both of these procedures had some complications, like non-vascularized bone grafts undergoing resorption, which requires replacement, whereas vascularized free flaps can undergo flap necrosis. To overcome the drawbacks of both the above bone reconstruction procedures and to bring back the function and form of the bone in its native site, doctors use bone morphogenetic proteins for reconstruction, as bone morphogenetic proteins help in mutation, osteoinduction, differentiation, and regeneration of new bone deposits in the damaged site. Thus bone morphogenetic proteins play a vital role in bone reconstruction surgeries.