Enhanced Height Increase with FGF?

Previously, one of the factors stimulated by F-spondin was FGF.  Inhibiting F-spondin(and in turn plasmin) resulted in enhancing height increase by 30%.  Since FGF is one of the compounds inhibited by F-spondin, it's possible that FGF's in some way reduce maximal height gain.  By studying the various functions of FGF, we can see if it increases or decreases height growth and whether we can eliminate it from our analysis of how F-spondin inhibits height gain.

Two isoforms of FGFR1 are upregulated by LSJL as well as FGF2 and FGF14.  FGF13 is downregulated by LSJL.

Induction of new bone by basic FGF-loaded porous carbonate apatite implants in femur defects in rats. 

[Carbonate apatite is a form of Calcium Phosphate]

"Thirty-six disc-shaped porous CA implants were inserted into femur defects in 36 Wister rats. Porous CA containing 0, 5, or 50 ng of bFGF was placed in the defect. Bone augmentation was evaluated at 2 and 12 weeks.
At 2 weeks postoperatively, new bone was evident in the defect sites with porous CA containing either 5 or 50 ng of bFGF. The area of regenerated bone was significantly higher with porous CA containing 5 ng of bFGF than with porous CA containing 50 ng. At 12 weeks postoperatively, no differences in new bone formation were seen between porous CA containing 5 and 50 ng bFGF. Porous CA containing bFGF markedly increased the amount of bone newly formed as compared with porous CA without bFGF. Regardless of the implantation period, TRAP-positive cells were visible around the material, indicating that osteoclast-like cells were resorbing porous CA. Bioresorption of the material increased over time: 6.3-7.8% at 2 weeks to 9.1-11.5% at 12 weeks."

"Calcium phosphate ceramics exhibit a high binding affinity for proteins and also provide a cell substratum on which osteogenic cells undergo growth and differentiation "<-can the same be true for chondrocytes?

So too high levels of FGF(10 times higher) inhibits growth rate.  But lower levels 5 ng of FGF benefits growth rate.  It could be that high levels of FGF inhibit cellular differentiation and encourage stem cell proliferation which would have an eventual benefit on height growth.

Actions of fibroblast growth factor-8 in bone cells in vitro. 

"The fibroblast growth factors (FGFs) are a group of at least 25 structurally related peptides. Some FGFs are active in bone, including FGF-1, FGF-2, and FGF-18. FGF-8 is osteogenic in mesenchymal stem cells.FGF-8 was expressed in rat primary osteoblasts and in osteoblastic UMR-106 and MC3T3-E1 cells. Both FGF-8a and FGF-8b potently stimulated the proliferation of osteoblastic cells, whereas they inhibited the formation of mineralized bone nodules in long-term cultures of osteoblasts and reduced the levels of osteoblast differentiation markers, osteocalcin, and bone sialoprotein. FGF-8a induced the phosphorylation of p42/p44 mitogen-activated protein kinase (MAPK) in osteoblastic cells; however, its mitogenic actions were not blocked by either the MAPK kinase (MEK) inhibitor U-0126 or the PI 3-kinase (PI3K) inhibitor LY-294002. FGF-8a, unlike FGF-8b and other members of the family, inhibited osteoclastogenesis in mouse bone marrow cultures, and this was via a receptor activator of NF-kappaB ligand (RANKL)/osteoprotegerin (OPG)-independent manner. FGF-8a did not affect osteoclastogenesis in RAW 264.7 cells (a macrophage cell line devoid of stromal cells) exogenously stimulated by RANKL, nor did it affect mature osteoclast function as assessed in rat calvarial organ cultures and isolated mature osteoclasts. FGF-8 is active in bone cells, stimulating osteoblast proliferation in a MAPK-independent pathway and inhibiting osteoclastogenesis via a RANKL/OPG-independent mechanism." 

FGF-8 affects osteoblasts and osteoclasts. 

"FGF-8 stimulates the expression of core-binding factor a-1 (Cbfa1) in the murine fibroblast-derived cell line C3H10T1/2"

"there is some evidence that ectopic bone and cartilage form in nude mouse tumors of S115 cells known to produce FGF-8"

"FGF-18 has a high homology to FGF-8"

"FGF-2 and FGF-18 stimulate osteoclast function, inducing osteoclastogenesis via receptor activator of NF-κB ligand (RANKL) as well as actively stimulating pit formation"

"FGF-8b and FGF-8e were reported to induce osteoclastic differentiation likely dependent of the RANKL/osteoprotegerin (OPG) pathway"

"FGF-8a stimulated connexin 43 (Cx43) expression in cultured mesenchymal cells from chicken limb buds"

BMP canonical Smad signaling through Smad1 and Smad5 is required for endochondral bone formation. 

"Bone morphogenetic protein (BMP) signaling{which typically use Smad receptors 1/5/8} is required for endochondral bone formation.  Deletion of individual Smads results in viable and fertile mice. Combined loss of Smads 1, 5 and 8, however, results in severe chondrodysplasia[dwarfism]. Smad1/5(CKO) (cartilage-specific knockout) mutant mice are nearly identical to Smad1/5(CKO);Smad8(-/-) mutants, indicating that Smads 1 and 5 have overlapping functions and are more important than Smad8 in cartilage. The Smad1/5(CKO) phenotype is more severe than that of Smad4(CKO) mice. The chondrodysplasia in Smad1/5(CKO) mice is accompanied by imbalances in cross-talk between the BMP, FGF and Ihh/PTHrP pathways. Ihh is a direct target of BMP pathways in chondrocytes and FGF exerts antagonistic effects on Ihh expression." 

"FGFs reduce Bmp4 and Ihh"

FGF has antagonistic effects on Ihh expression.   FGF-8 induces the phosphorylation of MAPK.  Here we see that FGF phosphorylates Smad.  FGF may inhibit height by inhibiting Ihh.  Of course alternatively, optimal levels may be needed to maintain the separate growth plate zones.   Remember that Smad 1/5/8 phosphorylation affects height growth.  Smad phosphorylation activates those genes.  Therefore, perhaps transgenic Smad 1/5/8 expression could encourage height growth.

"[Smad 1/5KO] mutants exhibited an expanded domain of type I collagen-producing cells.  These cells were randomly oriented, unlike the structure of the WT perichondrium, in which they are perpendicular to the growth plate. Type II collagen-producing cells, which are normally restricted to the growth plate, were embedded in the mutant periosteum"

"Apoptosis is normally confined to the hypertrophic zone. Apoptosis was expanded in mutant cartilage"

Smado 1/5KO mice had lower expression of Type II Collagen and Type X Collagen.

"Ucma is a marker for upper (resting) chondrocytes"

"Smad1/5CKO mutants exhibited increased expression of osteocalcin (Bglap1/2)"

"FGF18 treatment reduced C-terminal phosphorylation throughout the growth plate, whereas inhibition of endogenous FGF signaling using the FGF receptor antagonist SU5402 led to activation (C-terminal phosphorylation) of Smad1/5"

FGFR3 promotes synchondrosis closure and fusion of ossification centers through the MAPK pathway. 

"Activating mutations in FGFR3 cause achondroplasia. FGFR3 and MAPK signaling in chondrocytes promote synchondrosis closure and fusion of ossification centers[FGFR1 and FGFR2 are good for height growth whereas FGFR3 is bad for height growth; MAPK signaling chondrocytes is bad.  Note this is not MAPK signaling in osteo- cells]. We observed premature synchondrosis closure in the spine and cranial base in human cases of homozygous achondroplasia and thanatophoric dysplasia as well as in mouse models of achondroplasia. In both species, premature synchondrosis closure was associated with increased bone formation. Chondrocyte-specific activation of Fgfr3 in mice induced premature synchondrosis closure and enhanced osteoblast differentiation around synchondroses. FGF signaling in chondrocytes increases Bmp ligand mRNA expression and decreases Bmp antagonist mRNA expression in a MAPK-dependent manner, suggesting a role for Bmp signaling in the increased bone formation. The enhanced bone formation would accelerate the fusion of ossification centers and limit the endochondral bone growth." 

"Bmp ligands and Bmp antagonists [are] downstream targets of FGF signaling in chondrocytes. BMPs, such as Bmp-2 and Bmp-7, are strongly osteogenic, while their availability to the Bmp receptors is counterbalanced by BMP antagonists, such as Noggin, Gremlin and Chordin. Because BMP enhances chondrocyte hypertrophy, it is possible that increased BMP signaling together with increased FGF signaling in chondrocytes accelerated synchondrosis closure in Fgfr3G374R/+ mice{So too much BMP-2 for instance could be bad for height but it depends on the presence of FGFR3 receptors}. In addition, increased availability of BMPs may have accelerated osteoblast differentiation in the adjacent perichondrium." 

So FGF could be bad for height increase by activating MAPk in the chondrocytes which results in accelerated chondrocyte ossification. 

Proteoglycan desulfation determines the efficiency of chondrocyte autophagy and the extent of FGF signaling during endochondral ossification. 

"Cartilage extracellular matrix (ECM) contains large amounts of proteoglycans made of a protein core decorated by highly sulfated sugar chains, the glycosaminoglycans (GAGs)[LSJL upregulates ECM genes]. GAGs desulfation, a necessary step for their degradation, is exerted by sulfatases that are activated by another enzyme, Sulfatase-Modifying Factor 1 (SUMF1), whose inactivation in humans leads to severe skeletal abnormalities. Despite being expressed in both osteoblasts and chondrocytes Sumf1 does not affect osteoblast differentiation.  In chondrocytes it favors ECM production and autophagy and promotes proliferation and differentiation by limiting FGF signaling[How much Sumf1 promotes proliferation and differentiation may differ on expression levels of FGFR3 versus FGFR1/2]. Proteoglycan desulfation is a critical regulator of chondrogenesis." 

"The extracellular matrix (ECM) secreted by hypertrophic chondrocytes allows vascular invasion, degradation of the calcified ECM, and initiation of osteogenesis." 

"Sumf1, and proteoglycan desulfation, influence FGF signaling in chondrocytes during skeletal development.Sulfatases catalyze desulfation of the GAGs moiety of proteoglycans in the intracellular and extracellular space. These enzymes are substrates of Sumf1 whose only known function is to activate sulfatases. Proteoglycan desulfation regulates several aspects of chondrocyte biology. The block in proteoglycan desulfation caused by Sumf1−/− deletion severely decreases chondrocytes viability by hampering their capacity to generate enough energy through autophagy to survive in their avascular environment. This defect in autophagy is caused, in part, by the engulfment of lysosomes by undigested GAGs that leads to an impairment of the autophagosome–lysosome fusion"  

Proteoglycan desulfation inhibits the ability of GAGs to damage the growth plate tissue.  FGF results in a decrease of chondrocyte proliferation(based on FGFR3 expression). 

Fibroblast growth factor expression in the postnatal growth plate. 

"Fibroblast growth factor (FGF) signaling is essential for endochondral bone formation. In the postnatal growth plate, we quantitated expression of FGFs and FGF receptors (FGFRs) and examined both their spatial and temporal regulation. Tat proximal tibial growth plates and surrounding tissues were microdissected, and specific mRNAs were quantitated. Perichondrium expressed FGFs 1, 2, 6, 7, 9, and 18 and, at lower levels, FGFs 21 and 22. Growth plate expressed FGFs 2, 7, 18, and 22{Note that the growth plate does not generally express more specific FGFs than the perichondrium}. perichondrial FGFs regulate growth plate chondrogenesis{another link between the periosteum and height growth, therefore stimulating the periosteum like for instance mechanical load may affect height growth}. FGFs synthesized by growth plate chondrocytes may be physiologically important because of their proximity to target receptors. In growth plate, we found expression of FGFRs 1, 2, and 3, primarily, but not exclusively, the c isoforms. FGFRs 1 and 3, thought to negatively regulate chondrogenesis, were expressed at greater levels and at later stages of chondrocyte differentiation, with FGFR1 upregulated in the hypertrophic zone and FGFR3 upregulated in both proliferative and hypertrophic zones. FGFRs 2 and 4, putative positive regulators, were expressed at earlier stages of differentiation, with FGFR2 upregulated in the resting zone and FGFR4 in the resting and proliferative zones. FGFRL1, a presumed decoy receptor, was expressed in the resting zone. With increasing age and decreasing growth velocity, FGFR2 and 4 expression was downregulated in proliferative zone. Perichondrial FGF1, FGF7, FGF18, and FGF22 were upregulated. Temporal changes in FGF and FGFR expression may contribute to growth plate senescence and thus help determine the size of the adult skeleton." 

So, the regulation of FGF is complex and the optimal amount of them needed is similarly so.  The best way to grow taller would be to encourage desulfation of GAGs or to supplement with the non-sulfated forms of these compounds(like chondroitin(no sulfate)). 

"In mice, targeted ablation of FGFR2 impairs postnatal long bone growth"

"Activating mutations in FGFR1 cause osteoglophonic dysplasia, [a] short-limbed skeletal dysplasia in humans"

"mice conditionally deleted for FGFR1 in osteo-chondro-progenitor cells display an increased hypertrophic zone size, probably due to a decrease in the rate of cartilage resorption and ossification"

"although ablation of FGFR4 alone produces no apparent growth plate phenotype, double FGFR3/FGFR4-null mice show impaired long bone growth"<-So FGFR4 may be a better form of FGFR3 for height growth.

"dwarfism in mice overexpressing FGF2"

"Mice overexpressing FGF9 develop a skeletal dysplasia involving proximal long bones while FGF9-null mice display disproportionately short proximal skeletal elements"

"Ectopic expression of FGF9 in cranial bones induces [new] endochondral ossification"

"FGF18-null mice display long bone phenotypes similar to but even more severe than FGFR3 knockouts"

FGF may also play a role in cellular senescence.

FGF's detected in the perichondrium but not the growth plate:
FGFR2b
FGF1
FGF5
FGF6
FGF9
FGF10
FGF16
FGF21

FGF's detected in the metaphseal bones but not the growth plate:
FGFR2b
FGF1
FGF9
FGF21
FGF23

"No ligands were detected in growth plate that were not also present in perichondrium, and all overlapping ligands showed similar or greater expression in perichondrium"

"FGF2 expression in proliferative zone chondrocytes remained constant with age while both FGF18 and FGF22 mRNA levels declined"<-so reduction of FGF18&22 could be related to senescence.

"FGFR1c, FGFR2b, FGF1, FGF7, FGF18, FGF22, and FGFR3c mRNA levels all increased in expression with age [in the perichondrium]"

"Local production of FGFs in the growth plate may become increasingly important in the postnatal animal where the distance between the perichondrium and the interior of the growth plate increases."<-so perhaps exogenous FGFs can help increase height when animals no longer have a source of FGFs from the perichondrium.  Perhaps exogenous administration of proteins expressed in the perichondrium but not in the growth plate could help with height.


Inhibition of cellular senescence by developmentally regulated FGF-receptors in mesenchymal stem cells.

"MSCs should express FGF-receptors reflecting their developmental origin and potential. FGFR1 and 2 are expressed by rare mesenchymal progenitors in putative MSC niches in vivo including perichondrium, periosteum and trabecular marrow[So the expression of FGFR1 and FGFR2 is reprentative of a cells ability to differentiate, forcing expression of FGFR1 and FGFR2 may be a way to grow taller]. FGFR1+ cells often appeared as pericytes. These cells display a characteristic MSC phenotype in vitro when expanded with FGF-2, which appears to maintain MSC stemness by inhibiting cellular senescence through a PI3K/AKT-MDM2 pathway and promoting proliferation[FGF-2 may inhibit cellular senescence]. FGFRs may thus be involved in MSCs self-renewal. FGFR1/2 are developmentally-regulated markers of MSCs in vivo and in vitro and are important to maintain MSCs stemness."

"undifferentiated mesenchymal cells are present in murine embryonic perichondrium during endochondral bone formation. These cells were shown to adopt a pericyte identity while migrating from the perichondrium to colonize both the bone collar (cortical bone) and the primary spongiosa (trabecular bone)."

"FGFR1/2 signaling through PI3K/AKT-MDM2 promotes the proliferation of MSCs mainly by inhibiting cellular senescence while maintaining MSC properties."

"FGFR1 could be detected in the marrow cavity of postnatal bones"

"Perichondrial FGFR1/2+ cells were found to be surrounded by FGF-18–expressing cells"

"murine MSCs expanded from whole-bone crushes with FGF-2 express high levels of mRNAs encoding PDGFRα, PDGFRβ, TGFβR1, TGFβR2, and EGFR (HER1/ ErbB1)"

"After chondrocytic differentiation, Sox9+/collagen2+ chondrocytes robustly up-regulated FGFR3 and only a few undifferentiated cells maintained FGFR1 expression at the periphery of the micromass culture"

Check out figure 7 for a great diagram of the role of various FGFs.

Cellular engineering of cells that express FGFR1 and FGFR2 may be a way to grow taller.  In addition, there may be a way to upregulate FGFR1 and FGFR2.

FGFR1 even though it may negatively regulates chondrogenesis it only does so in the hypertrophic zone where it's time to stop chondrogenesis anyways and begin osteogenic differentiation.  Even if you stimulate FGF-1 and FGF-2(and perhaps FGF-4) by stimulating the periosteum and growth then this may not result in taller height growth as the number of receptors is a limiting factor.  Finding ways to upregulate FGFR1(you likely need either FGFR1 or FGFR3 and FGFR1 is preferential to growing taller than FGFR3) and FGFR2 may be a way to grow taller.

Fibroblast growth factor (FGF) 18 signals through FGF receptor 3 to promote chondrogenesis.

"the congenital absence of either FGF18 or FGFR3 resulted in similar expansion of the growth plates of fetal mice and the addition of FGF18 to human articular chondrocytes in culture enhanced proliferation and matrix production. FGF18 signals through FGFR3 to promote cartilage production by chondrocytes. We used the limb buds of FGFR3(+/+) and FGFR3(-/-) embryonic mice as a source of mesenchymal cells to determine how FGF18 signaling affects chondrogenesis. Impaired cartilage nodule formation [occurred] in the FGFR3(-/-) cultures. Potential contributing factors to the phenotype were identified as impaired mitogenic response to FGF18, decreased production of type II collagen and proteoglycan in response to FGF18 stimulation, impaired interactions with the extracellular matrix resulting from altered integrin receptor expression, and altered expression of FGFR1 and FGFR2. FGF18 [is] a selective ligand for FGFR3 in limb bud mesenchymal cells, which suppressed proliferation and promoted their differentiation and production of cartilage matrix."

"FGF2 and FGF18 [are] potential ligands for FGFR1 in hypertrophic chondrocytes, for FGFR3 in resting and proliferating chondrocytes, and for FGFR2 in the perichondrium and periosteum of developing long bones. FGF18 [may signal] selectively through FGFR3 to promote the differentiation of pre-chondrogenic mesenchymal cells to cartilage-producing chondrocytes."

"FGF18 signals through FGFR3 to increase expression of type II collagen and its α1β1 receptor in chondrogenic cells."

Here's a patent involving FGF variants for some height increase applications:

FGF VARIANTS AND METHODS FOR USE THEREOF

"All FGFRs tested so far bind FGF-1 (acidic FGF, aFGF) with moderate to high affinity, demonstrating an apparent redundancy in the FGF system. In contrast to FGFR1 and FGFR2, the third receptor subtype, FGFR3 [binds] to FGF-8, FGF-17 and FGF-18 with high affinity and to FGF-9 with improved selectivity. Specificity may also be achieved by specific proteoglycans expressed in different tissues."

"FGF-9 variants comprising mutations in the loop between the β8 and β9 strands of the polypeptide, previously identified as a conserved receptor binding site, and analogous loops in the other members of the FGF family, unexpectedly provide enhanced receptor subtype specificity."

"The FGF-2 variants are shown to stimulate proliferation of chondrocytes and induce differentiation of neuronal cells and may be used to specifically induce proliferation or differentiation of progenitor cells and embryonic or adult stem cells."

"the FGF variant [to promote growth plate bone growth] is selected from R64M-FGF9 or FGF9-2, and the bioactive agent is a natriuretic peptide. In another currently most preferred embodiment the FGF variant is selected from R64M-FGF9-W144G or FGF9-2-W144G and the bioactive agent is selected from C-type natriuretic peptide (CNP) or an analog thereof."

Fibroblast growth factor receptors in in vitro and in vivo chondrogenesis: relating tissue engineering using adult mesenchymal stem cells to embryonic development.

"mRNA levels of FGFR2 are upregulated in the mesenchymal condensation, whereas FGFR3 is expressed during differentiation and FGFR1 during hypertrophy."

"On embryonic day 12 (E12), N-cadherin was observed in the mesenchymal condensation in the center of the limb bud. Collagen II stained only very weakly in the mesenchymal condensation on E12. No collagen X was seen at this stage. On E12, expression of FGFR1 was lower in the mesenchymal condensation than in the surrounding loose mesenchyme. In contrast, FGFR2 and FGFR3 expression was seen only in the mesenchymal condensation, although the staining for FGFR3 was not very strong"

"no FGFRs are expressed in hyaline articular chondrocytes"

"FGF2 and FGF9 had differential effects when added at days 21–35. While FGF2 inhibited further matrix deposition, FGF9 increased matrix resorption."