Bone morphogenetic proteins (BMPs) are multi-functional growth factors that belong to the transforming growth factor β (TGF- β) superfamily.

1. Archana. B
Bone Morphogenic Protein

2. Technical terminologies
 Osteogenesis: refers to formation of bone.
 Osteoinduction: is the process by which osteogenesis is induced.
 Osteoconduction: This term means that bone grows on a surface.
Wilson Hench [1987] has suggested that osteoconduction is the
process by which bone is directed so as to conform to a material’s
surface.
 Osseointegration: This was first described by Brånemark and co-
workers [1977]. The term was first defined by Albrektsson et al.
[1981] as direct contact (at the light microscope level) between living
bone and implant

3.  Bone morphogenetic proteins (BMPs) are multi-functional growth factors
that belong to the transforming growth factor β (TGF- β) superfamily.
 The roles of BMPs in embryonic development and cellular functions in
postnatal and adult animals have been extensively studied in recent years.
 BMPs are now considered to constitute a group of pivotal morphogenetic
signals, orchestrating tissue architecture throughout the body (Bleuming
SA et al 2007)
 According to kessler et al 1996 BMPs are bone derived factors capable of
inducing ectopic bone formation

4. The ability of devitalized bone, when implanted in an animal, to induce a
cellular response resulting in new bone tissue formation has been known
for decades.
This unique activity was observed and researched extensively by an
orthopedic surgeon, Dr. Marshall Urist.
He subsequently demonstrated that this activity could be extracted from the
organic component of bone, and that a protein or proteins were responsible
for this activity.
He thus named this activity “bone morphogenetic protein.”

5. Implantation of this protein component of bone matrix resulted in
a complex series of cellular events including mesenchymal cell
infiltration, cartilage formation, vascularization, bone formation,
and ultimately remodeling of the new bone tissue along with
population by hematopoietic bone marrow elements.

6.  BMPs are of tremendous interest as therapeutic agents for healing
bone fractures, including non-union and in open tibial fracture. Also
used in spinal fusion and reported to prevent osteoporosis.
 In dentistry, it is used for augmentation of maxillary sinus floor and
alveolar ridge. BMPs may provide a promising alternative to
traditional grafting procedures.
 Its scope further extends in treating periodontal bone defects and in
implant placement along with alloplastic materials, root coverage
procedures and in periodontal regeneration.

7. Properties

8. 1. They act as mitogens on undifferentiated mesenchymal cells and
osteoblast precursors. Structurally they are related to TGF-β super
family.
2. BMP 2-12 singly initiate de novo endochondral bone formation.
3. BMPs induce bone formation where as other growth factors such as
TGF-β and PDGF donot.
4. BMPs have an anabolic effect on periodontal tissue through
stimulation of osteoblastic differentiation in human periodontal
ligament cells.

9. 5. Bone graft materials contain varying amount of BMPs such
as BMP 2-4 and a deficiency of BMP like protein retards
bone cell differentiation and may account for failure of
fracture to heal.
6. Recombinant BMPs have shown to promote bone formation.
7. They induce the expression of osteoblast Phenotype
8. Act as chemoattractants for mesenchymal cells and
monocytes as well as binding to extra cellular matrix type 4
collagen.

10. Extraction of BMPs

11. Advances in biochemical techniques and the advent of biotechnology
eventually allowed the purification and subsequent molecular cloning of
the factors responsible for the osteoinductive activity in bone.
The purification process included removal of the mineral component of
bone with acid, extraction of the active component from the remaining
organic matrix of bone using chaotropic agents, and multiple column
chromatography steps.

12. Using amino acid sequence information from this purified
extract, the genes or cDNAs encoding each of the proteins
were cloned molecularly. Analysis of these clones indicated
that the bone-inductive extract consisted of a family of related
proteins, i.e, the “bone morphogenetic proteins”.

13. The use of demineralized freeze-dried bone allograft (DFDBA) had been the
focus of much attention throughout the past 30 years as one such material
which may be capable of promoting regeneration of the attachment
apparatus.
Becker et al. [1994] examined the inductivity of DFDBA by placing it in
human extraction sites and then comparing it histologically to control sites
grafted with autogenous bone.
They reported that within those sites grafted with DFDBA, the DFDBA
particles exhibited osteoblastic activity.

14. Release kinetics of
BMPS...

15.  A study by Talwar et al have shown that rapid release of BMPs resulted in
bone formation and slow release promotes cementum formation [King, J.
et al 2011]
 By affecting the degradation rate of carrier, its release kinetics could be
altered. Resorbable carrier matrices have an unpredictable degradation
rate.
 Regeneration may be limited since earlier resorption leads to premature
obliteration of space. In case of non-resorbable carriers such as
ethacrylate/tetrahydrofurfuryl methacrylate (PEM/THFM), amount and
duration of release can be altered by adjusting the preparation method.

16.  They have been observed to have an initial rapid relief followed
by a slow release and resiliency in maintaining the space
necessary for proliferation and differentiation of osteogenic cells.
 However they necessitate a second surgery for removal.
 Release kinetics could be altered through
1.Chemical method- for example gelatin carrier is altered by cross-
linking with glutraldehyde.
2. Magnetic field,
3. Ultrasound
4. Emission of photons.

17. Types & Functions...
BMP 1
BMP 7
BMP 6
BMP 4
BMP 2

18. BMP Functions
BMP1
BMP1 does not belong to the TGF-β family of proteins. It
is a metalloprotease that acts on procollagen I, II, and III.
It is involved in cartilage development.
BMP2
Acts as a disulfide-linked homodimer and induces bone
and cartilage formation. It is a candidate as a retinoid
mediator. Plays a key role in osteoblast differentiation.
BMP3 Induces bone formation. Also called osteogenin
BMP4
Regulates the formation of teeth, limbs and bone from
mesoderm. It also plays a role in fracture repair, epidermis
formation, dorsal-ventral axis formation, and ovarian
follical development.
BMP5 Performs functions in cartilage development.
BMP6
Plays a role in joint integrity in adults. Controls iron
homeostasis via regulation of hepcidin

19. BMP Functions
BMP7
Plays a key role in osteoblast differentiation. It also
induces the production of SMAD1. Also key in renal
development and repair.
BMP8a Involved in bone and cartilage development.
BMP8b Expressed in the hippocampus.
BMP10
May play a role in the trabeculation of the embryonic
heart
BMP11 Controls anterior-posterior patterning
BMP15
May play a role in oocyte and follicular
development.

20. BMPs also play a role in a number of non-osteogenic
developmental processes:
•Neural induction represents the earliest step in the determination of
ectodermal cell fates.
•In vertebrates, BMPs act as signals of epidermal induction (Mun˜oz-
Sanjua´n and Brivanlou, 2002).
• BMP-2 directs the development of neural crest cells into neuronal
phenotypes (Christiansen et al., 2000), while BMP-4 and 7 specifically
induce a sympathetic adrenergic phenotype.

21. •BMPs give direction to somite development by inhibiting the process
of myogenesis.
•Physiological roles of BMPs and BMP receptor signaling in normal
bone formation have been investigated.
•Injection of BMP-2 locally over the surface of calvariae of mice
induces periosteal bone formation on the surface of calvariae without
a prior cartilage phase (Chen et al., 1997).

22. BMPs in bone induction

23. •Bone formation can take place by an intramembraneous (direct) or
endochondral (indirect) process.
•In both mechanisms, the induction of bone and cartilage occurs through
an epithelial - mesenchymal interaction that initiates specific cell
differentiation.
•Depending on the concentration gradient BMPs can attract various types
of cells and can act as chemotactic, mitogenic/or differentiating agent.
•BMPs can induce differentiation of mesenchymal progenitor cells into
various cell types including chondroblasts and osteoblasts.

24. BONE INDUCING PROPERTY OF BMPS
Subcutaneous implantation of demineralized bone matrix leads to
endochondral bone formation similar to embryonic bone development.
The sequential developmental cascade includes
1. Activation and migration of undifferentiated mesenchymal cells by
chemotaxis;
2. anchorage-dependent cell attachment to the matrix via fibronectin;
3. mitosis and proliferation of mesenchymal cells;
4. differentiation of cartilage;

25. 5. mineralization of the cartilage;
6. vascular invasion and chondrolysis;
7. differentiation of osteoblasts and deposition of bone matrix;
8. Mineralization of bone
9. Differentiation of hemopoietic marrow in the newly developed
ossicle.

26. Receptors...

27. Most of the biological action of BMPs are mediated through the
BMP receptors which initiate signaling from the cell surface
when bind to two distinct type I and II serine/threonine kinase
receptors, required for signal transduction.[Massgue J, et al
1996].
BMP receptors are composed of three parts: a short extracellular
domain, a single membrane-spanning domain, and an
intracellular domain with active serine/threonine region.[Lin
HY,1995]

28. The type II receptor is the primary binding site of the ligand and
upon its activation, phosporylation of type I receptor occurs.
It is the type I receptor (or activin receptor-like kinases) that
determines the nature of biologic response.

31. Pathway...

32. BMPs can signal through both canonical and non-canonical
pathways. In the canonical signaling pathway, they initiate the
signal transduction cascade by binding to cell surface receptors and
forming a heterotetrameric complex comprised of two dimers of
type I and type II serine/threonine kinase receptors

34. The mechanism of the heterotetrameric signaling complex formation can
vary.
For example, BMP6 and BMP7 interact with type II receptors and recruit
type I receptors, whereas BMP2 and BMP4 preferentially bind type I
receptors and recruit type II receptors. [De Caestecker et al 2004].

35. Upon formation of a heterotetrameric complex, the constitutively
active type II receptor transphosphorylates the type I receptor at a
glycine-serine rich motif known as the GS domain. This activates
the type I receptor and allows phosphorylation of the
immediately downstream substrate proteins known as the
receptor-regulated Smads (R-Smads) at a C-terminal SSXS motif.

36. The R-Smads involved in BMP signaling are Smad1, Smad5, and Smad8
(Smad1/5/8).
Rsmads then associate with the co-mediator Smad (co-Smad) Smad4,
and this complex translocates to the nucleus where it functions as a
transcription factor with coactivators and corepressors to regulate gene
expression.
Inhibitory Smads (I-Smads), Smad6 and Smad7 (Smad6/7), are involved
in feedback inhibition of the signaling pathway.

37. Various non-canonical pathways, including the MAPK
cascade, can also lead to regulation of gene expression.
BMP signaling is modulated extracellularly (e.g., Noggin),
intracellularly (e.g., FKBP12, microRNAs, phosphatases, and
I-Smads), and by co-receptors in the plasma membrane (e.g.,
Endoglin).

38. BMP4, for example, was found to activate TAK-1, a serineethreonine
kinase of the MAPKKK family.
In addition to the MAPK pathway, BMP signaling has been found to affect
PI3K/Akt, P/kc, Rho-GTPases, and others.
The specific pathway that is activated upon ligand-receptor interaction is
thus likely dependent upon the extracellular environment, other cellular
activity.

40. Factors Affecting BMP Activity
SYNERGISTIC EFFECT ANTAGONISTIC EFFECT
LOCAL
FACTORS
Basic fibroblast growth factor
(low dose)
Basic fibroblast growth factor (high
dose) [Hanada K, et al 1997]
Transforming growth factor [Hanada
K, et al 1997]
Prostaglandins (PG E1)[Ono I, et
al 1996]
SYSTEMIC
FACTORS
Glucocorticoids[Mayer H, et al
1996]
Vitamin D[Amedee J, et al
1994]
Beta-estradiol[Takuwa Y, et al
1991]

41. Recombinant
technologies

42. The structures of several human BMPs have been identified, it is
possible to use DNA probes to obtain human complimentary DNA
sequence.
The human cDNA is cloned and spliced into a viral expression vector,
E. coli transfected to become carriers have been used to produce BMPs
in large quantities for preclinical and clinical evaluation. Therefore
rh-BMP (recombinant human – rh) produced provides optimum
capability for clinical applications.
In 2002, The US Food and Drug Administration (FDA) approved
BMP-2 and BMP-7 for use in bone regeneration

43. BMP – delivery systems
Several matrices and delivery systems have been used
and evaluated for their efficacy and biocompatibility as
carrier for BMPs. Three major strategies for growth
factor delivery: gene therapy, cell therapy, and protein
therapy.

44. Gene therapy and stem cell-based therapy represent the major advance,
however, presently are still in their infancy regarding safety and efficacy
in human.[Kimelman N, et al 2007].
Protein therapy, on the other hand, has demonstrated the most practical
promise, mainly incorporating osteoinductive morphogens (BMPs) even
so with some limitations.
It was suggested that the clinical efficacy of rhBMPs will depend upon
the carrier system, for effective delivery of adequate protein
concentrations to the desired site.[Mont MA, et al 2004]

45. •An absorbable collagen sponge (ACS) was the first BMP carrier
technology to be approved by the US Food and Drug Administration
(FDA).
•The absorbable collagen sponge is a bovine type I collagen matrix that
is soak loaded with a BMP solution before surgical implantation.
•The rhBMP/ ACS construct has shown the clinical efficacy for a
number of indications; however, it is vulnerable to tissue compression.
•The collagen matrix retains 65% of the BMPs during initial
impregnation and releases it in two phases an initial phase within hours
of implantation and a second phase that depends on nature and
geometrical characteristics.

47. Periodontal
regeneration and
BMPs

48. BMPs play an important role in the process of bone modeling and
remodeling through chemotatic, mitogenic or differentiating mechanism
[Sykaras N, et al 2003].
Histological analysis showed that BMPs, in conjunction with the
collagenous matrix, induced cementum, periodontal ligament, and
alveolar bone regeneration.
Another study reported that partially purified osteogenin, isolated from
human bone matrix, when reconstituted with allogenic freeze dried
deminerlized bone matrix, enhanced new connective tissue attachment,
and alveolar bone regeneration in a root submerged environment in a
series of human biopsies.[Bowers G, et al 1991].

49. A study where rhBMP-2 was used in a prepared periodontal defect in
beagle dogs showed significant regeneration of the periodontal
tissues.[Sigurdsson TJ, et al 1996].
The effect of rhBMP-2 was evaluated in the surgically created critical size,
supra alveolar periodontal defects in mandibular premolar teeth in beagle
dogs which were implanted with rhBMP-2/ ACS at different
concentrations.

50. The ankylotic union was observed in the coronal aspect of supra
alveolar defects.
Given the unique action of BMPs on mineralized tissue formation,
obliteration of periodontal ligament space and ankylosis are a potential
complication for the use of BMPs in the periodontium.

51. The BMP/TGF-b signaling pathway mediates osteoblastic
differentiation and in vivo bone formation
BMP-2 and -7 were reported to the play a role in the differentiation of
periodontal ligament stem cells (PDLSC) and dental follicle stem
cells.
Reparative dentin formation was promoted by BMP-2 and 7. Other
members of the BMP family, such as BMP-7/OP-1 have observed
periodontal regeneration in animal model.

52. BMPS In tissue
engineering .....

53. Tissue engineering aims to reconstruct lost tissues or organs
and is considered as the ultimate regenerative technique.
With the help of tissue engineering, therapies such as the
production of skin to treat burns, bone grafts, arteries to treat
atherosclerotic vascular disease and cartilage for plastic and
reconstructive surgeries have been achieved.
Tissue engineering is being applied in dentistry for the
regeneration of temporo-mandibular joint, periodontal
ligament, dentin, enamel, pulp and integrated tooth tissues.

54. Tissue engineering has three key features namely
• Cells - that synthesize the matrix essential for the new tissue.
• Scaffolds - that provide the environment for the cells to synthesize
matrix.
• Signaling molecules such as growth factors – that facilitate and promote
this action.
The growth factors that have frequently been applied to tissue engineering
include bone morphogenetic proteins (BMPs), basic fibroblast growth
factor (bFGF or FGF-2), vascular epithelial growth factor and
transforming growth factor-b (TGF-b).

55. BMPS IN SOCKET AUGMENTATION:
BMPS when used in augmentation of socket and maxillary sinus
wall [Boyne PJ et al ,1997] were found to promote soft-tissue
healing, minimize surgery time, reduce potential postsurgical
infection, accelerate cell migration and promotes early bone
formation.

56. BMPS In Implantology

57. Application of BMPs for the osseointegration of Endosseous implant
has been evaluated by some authors [King GN et al in 2002].
Osseo-integration is critical for endosseous implant in which there is
complete union of implant with bone. Sometimes there would be
insufficiency in quality or amount of bone, which is addressed by
using grafts or growth factors.

58. In human trial studies conducted by Howell in 1997 and Cochran et al in
2000 using Recombinant human BMP-2 in collagen sponge carrier, bone
formation at the extracted site was observed, which helped in endosseous
implant placement.
Boyne et al in 1997, observed bone formation in sinus lift procedure using
the same combination and this aided in implant placement .
A feasibility study evaluating rhBMP-2/absorbable collagen sponge for
maxillary sinus floor augmentation

59. BMPS Used along
with distraction
osteogenesis

60. Rachmiel et al I 2006, evaluated the effect of rhBMP in distraction
osteogenesis in sheep model. 1.5 mm distraction devices were placed
following alveolar segmental osteotomy in sheep.
5 days later rhBMP was injected. Radiographic analysis showed lifting
of the transported segment and union of the distracted segment, newly
formed bone and the native bone.
Thus BMPs when used in the process of distraction osteogenesis
seemed to minimise the consolidation period, allowing early
placement of implants.

61. BMP implanted at the distraction site, may induce the noncommitted
mesenchymal cells to form cells of osteoblastic or chondroblastic
lineage. Thus to reduce the consolidation phase and improve quality of
bone, BMPs can be used in DO procedure.

62. Limitations...
•Lack of bone induction with BMPs combined with hydroxyapatite alone –
probably as a result of the lack of resorption of hydroxyapatite and the tight
binding affinity between BMPs and hydroxyapatite; moreover,
immunogenecity and risk of disease transmission with the use of
demineralized bone matrix and acidic breakdown products of synthetic
polymers which might prove detrimental to wound healing.

63. •A further complicating factor is that different anatomical sites might
require different kinetics of release for optimal performance.
•A major problem with delivery of growth factor proteins is the
limited bioactivity (half-life) of proteins due to degradation and
difficulty in achieving a controlled release.

64. Conclusion

65. Despite a lack of complete understanding of BMP cellular
pathways, addition of BMPs remains the growth factor of choice
to induce mesenchymal stem cell differentiation to osteoblasts to
induce bone formation.
However, to date, sufficient human studies with BMPs in
periodontal defects are lacking.

66. Periodontal tissue regeneration entails the induction of periodontal
ligament, cementum, and alveolar bone.
Although, several studies have shown significant regeneration of the
periodontal tissues with the use of BMP, it is important to understand the
biologic processes of periodontal wound healing and the effects of these
biologic processes on BMP activity.

67. Further studies are needed for the development of delivery
systems that have mechanical and surgical properties appropriate
for controlled release of bone morphogenetic proteins and
identifying optimal condition for the use of BMPs for periodontal
regeneration.

68. Thank
you...!