Grow Taller with Osteoblasts?

In the entry on increasing torso height, we learned that osteoblast activity deposits bone beneath the periosteum which results in appositional growth(growth in width).  This usually takes place beneath the periosteum but there exists a possibility for bone to be deposited on the subchondral plate if osteoblast adhesion was encouraged there.  So, how do you stimulate osteoblast proliferation and encourage the deposit of bone beneath the subchondral plate?  It would seem that just increasing osteoblast activity would not be enough as you want the osteoblasts to deposit bone at a specific point(beneath the subchondral plate).  However, one would assume that the more osteoblast activity is stimulated the more likely that the osteoblasts would be to deposit bone beneath the periosteum.  Still, osteoblast activity activates RANKL activity which stimulates osteoclasts which can cause bone disease.  In conclusion, finding the things that regulate osteoblasts is more important than just increasing osteoblast proliferation.

Here's something that's used to encourage osteoblast and adhesion and if we applied to to the subchondral plate we could get bone deposition there and at which point grow taller.

Activation of cyclic amp/protein kinase: A signaling pathway enhances osteoblast cell adhesion on biomaterials for regenerative engineering.

"osteoblastic cells adhering to biodegradable biomaterials require the expression of integrins on the cell surface[we can manipulate integrins to affect osteoblast adhesion to grow taller]. We report here that cyclic adenosine monophosphate (cAMP), a small signaling molecule, regulates osteoblast cell adhesion to biomaterial surfaces[altering cAMP could be a mechanism to achieve height increase as well]. We used an in vitro cell adhesion assay to demonstrate that at 0.1 mM, 8-Br-cAMP, a cell-permeable cAMP analog, significantly enhances osteoblast-like cells' (MC3T3-E1) adherence to biomaterials[so this is the analog that should be applied beneath the subchondral plate]. Moreover, we demonstrate that a commonly used cAMP-elevating agent, forskolin, promotes cell adhesion similar to that of the cell permeable cAMP analog[forskolin is another option]. By using different target-specific cAMP analogs: 8-CPT-2Me-cAMP which specifically activates exchange protein activated by cAMP (Epac), and 6-Bnz-cAMP which specifically activates protein kinase A (PKA), we observed that the PKA signaling pathway plays a dominant role in this process. Thus, this report suggests a new method to enhance osteoblast cell adhesion on biodegradable biomaterials for bone regenerative engineering applications."

Forskolin is available for sale: Life Extension Forskolin 10mg Capsules, 60-Count.  We don't know if it will induce an increase in cellular adhesion in specific locations.

Regulation of osteoblast and osteoclast functions by FGF-6. 

"Fibroblast growth factor-6 (FGF-6) is known to be the key ligand for fibroblast growth factor receptor 4 (FGFR4) during muscle regeneration but its role in bone has yet to be verified. Fibroblast growth factor receptor signaling is known to be important in the initiation and regulation of osteogenesis, so in this study the actions of FGF-6 on human osteoblasts and osteoclasts were investigated. Human primary osteoblasts (hOB) were used to study the effect of FGF-6 on proliferation (by ATP quantification), signal transduction (by ERK and AKT phosphorylation), differentiation (by alkaline phosphatase activity) and mineralization (by calcein staining). To study FGF-6 activity on osteoclast differentiation, human bone marrow cells were used and tartrate-resistant acid phosphatase (TRAP) multinucleated cells together with actin filaments arrangements were quantified. Human primary mature osteoclasts were used to evaluate the effect of FGF-6 on osteoclast reabsorbing activity by reabsorbed pit measurements. FGF-6 > 10(-9) M as FGF-2 10(-7) M induced hOB proliferation mediated by pERK together with a reduction in alkaline phosphatase activity and reduced mineralization of the treated cells[FGF-6 increased osteoblast proliferation but decreased osteoblast differentiation by virtue of reduced alkaline phosphatase activity]. Moreover FGF-6 increased the formation of TRAP positive multinucleated cells in a dose-dependent manner (maximal effect at 10(-8)M). FGF-6 treated cells showed also a greater percentage of cells that formed typical osteoclast sealing zones. Mature osteoclasts cultured on dentine slice increased the area of reabsorption with a maximal effect of FGF-6 at 10(-12) M. FGF-6 may be considered a regulator of bone metabolism as shown by its activity on both osteoblasts and osteoclasts." 

Fibroblast growth factor-6 seems to increase the acitivity of both osteoblasts and osteoclasts.  Now that's no problem as we want an increase in activity in different areas.  We want an increase in osteoblast activity beneath the periosteum and we can tolerate an increase in osteoclast activity by the endosteum. 

Mesenchymal Stem Cells have the ability to differentiate into osteoblasts.  In the long bones, we want MSCs to differentiate into chondrocytes in the hyaline cartilage growth plate line.  The other bone types contain red bone marrow too in the spongy bone but unlike with long bones we want the MSCs to differentiate into osteoblasts by the periosteum. 

In Long Bones to grow taller: Increase MSC proliferation and encourage MSCs to differentiate into chondrocytes


In Some Bones to grow taller: Increase MSC proliferation, encourage MSCs to differentiate into osteoblasts, send osteoblasts to deposit bone beneath the subchondral plate or beneath the periosteum where applicable.

ACTH is a novel regulator of bone mass. 

"Adrenocorticotropin (ACTH) is one of several peptide hormones derived from a larger molecule, proopiomelanocortin (POMC). ACTH is a classic endocrine hormone, processed and secreted from the pituitary to stimulate cortisol production from the fasciculata cells in the adrenal gland. However, ACTH is also produced by other cells, including macrophages, at many sites in the body. ACTH binds to a specific member of the melanocortin receptor family, the MC2R. MC2R is expressed in osteoblastic cells in vivo, as shown by in situ hybridization. MC2R expression is strongest at sites of active bone deposition, and thus ACTH response probably varies with osteoblastic activity or stage of osteoblast differentiation. In vitro ACTH stimulates proliferation of osteoblasts in a dose-dependent manner. ACTH at 10 nM increases collagen I mRNA in the osteoblastic cell line SaOs2, although at lower concentrations ACTH may oppose osteoblast differentiation. ACTH is thus, at high concentrations, anabolic for the osteoblast, and it is highly likely that the hormone has concentration-dependent effects on bone metabolism in vivo." 

So, we don't want ACTH to reach the adrenal gland but we do want it to reach the bone so it can bind to a melanocortin receptor.  We know there's a blood brain barrier so all we have to do to prevent this is to encourage ACTH production in other sites like the aforementioned macrophages.   

Impact is a commonly sited method for bone building.  Impact causing microfractures may stimulate bone growth but impact may also cause a mechanotransducary sort of stimulus that causes bone growth.  

The Interaction of Biological Factors with Mechanical Signals in Bone Adaptation: Recent Developments

"Mechanotransduction in bone is fundamental to proper skeletal development. Deficiencies in signaling mechanisms that transduce physical forces to effector cells can have severe consequences for skeletal integrity[thus mechanotransduction may possibly affect height].  In recent years, progress has been made on many fronts regarding our understanding of bone cell mechanotransduction, including subcellular localization of mechanosensitive components in bone cells, the discovery of mechanosensitive Gprotein-coupled receptors, identification of new ion channels and larger pores (eg, hemichannels) involved in physical signal transduction, and cell adhesion proteins, among others."

"Osteocytes are likely the mechanosensory cell type in bone. Osteocytes reside in a mineralized matrix, and have long cytoplasmic processes that allow communication with one another and with cells on the bone surfaces."<-so osteocytes may be able to communicate with mesenchymal stem cells and encourage them to differentiate into chondrocytes.

"As bone is loaded in bending, extracellular fluid movement occurs between the osteocyte cell body/processes and the lacunocanalicular walls. The fluid movement in those spaces creates drag forces that pull on tethering structures of the glycocalyx, which suspend the osteocyte from the bony walls. Those drag
forces create radial strains on the cell processes, and induce mechanosensory proteins to signal."<-Are mesenchymal stem cells too far from the lacunae to be affected by osteocyte cell processes?  Still the mechanosensory proteins may affect MSC differentiation into chondrocytes.

"A potential candidate for a mechanosensor in bone is G-protein signaling, which can become activated (GTP-bound) by ligand-independent mechanical perturbation of the G-protein-coupled receptor (GPCR), or by GPCR-independent mechanical perturbation of the membrane.  The α5β1 integrin was recently shown to directly promote opening of Cx43 hemichannels in the membrane, which allow mechanical signaling molecules to act on key receptors"<-Interaction of the Beta1 integrin with collagen type II was shown to activate ERK.  That interaction is very similar to the alpha-5Beta1 integrin interaction with the hemichannels of the membrane.  Thus perhaps Beta1 integrin interaction with collagen type II is a mechanosensory mechanism.

The study states that osteoblast cell lines may be as sensitive to shear strain as osteocyte cell lines.

"TrpV4, a receptor known to be sensitive to mechanical perturbation (most notably, cell swelling) and osmolarity in other tissues, was recently shown to modulate the response to mechanical disuse in mice."<-Chondrocytes were shown to have their response to osmolarity be mediated by TrpV4 as well.  However, TrpV4 may be more important to regulatory volume decrease than increase.

"Tail-suspended TrpV4 knockout mice failed to lose bone and did not exhibit reduced bone formation rates as was observed in tail suspended WT mice."<-So TrpV4 likely plays a role in osteocyte adaptation as well.  Perhaps TrpV4 is a negative gene for height growth and it would be better for it to be downregulated.

"fluid shear stress leads to ligand independent response (conformational change) of the PTHR1, similar to that found when the cells were treated with PTH 3-34"<-PTH enhances chondrogenesis.  Since fluid shear stress acts similarly to PTH 3-34 fluid shear stress likely induces chondrogenesis.

"osteoblast/osteocyte deletion of β1 not only protected mice from the normal (as was observed in the WT) tail suspension induced deterioration of bone mechanical properties, but mechanical properties were actually improved by tail suspension in the mutants."<-so maybe manipulation of Beta1 in addition to TrpV4 is important to height growth.  We'd have to see what the result of chondrocyte deletion of Beta1 is.

According to Beta1 integrin deficiency results in multiple abnormalities of the knee joint, Beta1 deletion of chondrocytes is not anabolic.  Beta1 deletion resulted in dwarfism.

Let-7 which has been linked to height growth via HMGA2 is related to osteoblast signaling.

Biological functions of miR-29b contribute to positive regulation of osteoblast differentiation.

"Bone tissue arises from mesenchymal cells induced into the osteoblast lineage by essential transcription factors and signaling cascades. MicroRNAs regulate biological processes by binding to mRNA 3′-untranslated region (UTR) sequences to attenuate protein synthesis. Here we performed microRNA profiling and identified miRs that are up-regulated through stages of osteoblast differentiation. Among these are the miR-29, miR-let-7, and miR-26 families that target many collagens and extracellular matrix proteins. We find that miR-29b supports osteoblast differentiation through several mechanisms. miR-29b decreased and anti-miR-29b increased activity of COL1A1{up in LSJL}, COL5A3, and COL4A2{up in LSJL} 3′-UTR sequences in reporter assays, as well as endogenous gene expression. These results support a mechanism for regulating collagen protein accumulation during the mineralization stage when miR-29b reaches peak levels. We propose that this mechanism prevents fibrosis and facilitates mineral deposition. Our studies further demonstrate that miR-29b promotes osteogenesis by directly down-regulating known inhibitors of osteoblast differentiation, HDAC4, TGFβ3, ACVR2A, CTNNBIP1, and DUSP2 proteins through binding to target 3′-UTR sequences in their mRNAs. Thus, miR-29b is a key regulator of development of the osteoblast phenotype by targeting anti-osteogenic factors and modulating bone extracellular matrix proteins."

So Let-7 is related to osteoblasts and since Let-7 is related to height growth osteoblasts are likely related to height growth.

"miR-29b targets several negative regulators of osteogenic differentiation, including TGFβ3, HDAC4, ACTVR2A, CTNNBIP1, and DUSP2"<-Since TGFBeta3 IS prochondrogenic perhaps inhibiting miR-29b can positively regulate chondrogenesis.

According to the supplementary materials of the paper the let-7 family is associated with extracellular matrix genes but not Col2a1 which is directly associated with chondrogenesis but is associated with Col1a1 which is associated with osteoblastgenesis which indicates that since let-7 is important to height that Col1a1 is important to height.


ECM-dependent mRNA expression profiles and phosphorylation patterns of p130Cas, FAK, ERK and p38 MAPK of osteoblast-like cells.

"Osteoblast cells synthesize collagen-rich ECM (extracellular matrix) in response to various environmental cues. Using MC3T3 E1 osteoblast-like cells and mouse whole-genome microarrays, we investigated molecular signalling affected by collagen-based ECMs. A genome-wide expression analysis revealed that cells grown in the 3D collagen matrix partially suppressed the genes associated with cell adhesion and cell cycling. Western analysis demonstrated that the expression of the active (phosphorylated) form of p130Cas, FAK (focal adhesion kinase) and ERK1/2 (extracellular-signal-regulated protein kinase 1/2) was reduced in cells grown in the 3D matrix. Conversely, phosphorylation of p38 MAPK (p38 mitogen-activated protein kinase) was elevated in the 3D matrix, and its up-regulation was linked to an increase in mRNA levels of dentin matrix protein 1 and bone sialoprotein."

This change in phosphorylation can affect chondrocyte differentiation.