Inhibiting Estrogen to Increase Height

It's important to evaluate inhibiting Estrogen to increase height after we found that estrogen inhibits TGF-Beta induced Smad3 signaling which induces chondrogenesis.

Use of aromatase inhibitors to increase final height. 

"During puberty in both sexes, the mechanism involved in epiphyseal fusion is mediated by the action of estrogen through a cascade of events including proliferation, differentiation, and apoptosis of chondrocytes. The enzyme P450 aromatase catalyzes the aromatization of C19 androgens (androstenedione and testosterone) to C18 estrogens (estrone and estradiol). Inhibition of estrogen action by aromatase inhibitors (AIs) appears to decelerate the process of growth plate fusion[Note delaying growth plate fusion may not increase final height if growth velocity does not also increase], and thus AIs may be used therapeutically to increase adult height. The clinical experience with AIs in the pediatric setting is limited to testolactone, fadrozole, letrozole, and anastrozole. Testolactone, a nonselective steroidal AI, has been used successfully as an adjunct to antiandrogen and gonadotropin-releasing hormone analogue (GnRHa), therapy for children with familial male-limited precocious puberty (FMPP) and congenital adrenal hyperplasia (CAH), and with some success in girls with McCune-Albright syndrome. The limitations of testolactone include its relatively low potency and the need for frequent dosing. Results of a randomized placebo-controlled trial in boys with delayed puberty treated with letrozole, a selective nonsteroidal AI, found that boys treated with letrozole + testosterone experienced delayed bone maturation and good growth response and achieved an increase in predicted adult height[keyword: PREDICTED adult height]. In this study, only minor differences in bone density were seen between the placebo and letrozole treatment groups[bone density takes into account bone size as well so that means that bone size did not increase], both of which were receiving concomitant testosterone therapy. No adverse effects on testis size or inhibin B concentration were noted." 

"bone in both men and women has the capacity to convert androgen to estrogen in the bone"

"mean predicted adult stature was 143.0 ± 7.8 cm before treatment and 147.3 ± 11.5 cm after 3 years" with AI treatment.

"an increase in predicted adult height was seen for all but one boy in the letrozole + testosterone group (range, 2.5–8.8 cm); predicted adult height decreased by 3.5 cm for the one remaining boy."

Impact of growth plate senescence on catch-up growth and epiphyseal fusion. 

"In mammals, longitudinal bone growth occurs rapidly in prenatal and early postnatal life, but then slows and eventually ceases. This deceleration, which reflects a decline in chondrocyte proliferation, was previously attributed to a hormonal or other systemic mechanism. However, new evidence suggests that it is due to a local mechanism within the growth plate[See not estrogen, GH, IGF-1, or testosterone]. growth plate chondrocytes have a finite proliferative capacity that is gradually exhausted, causing growth to slow and finally stop." 

"With age, there is a decrease in the overall height of the growth plate, associated with a decline in the number of proliferative and hypertrophic chondrocytes per column. In addition, the individual hypertrophic cells do not grow as large in an older animal, and the columns become more widely spaced with more intervening cartilage matrix. The number of apoptotic growth plate chondrocytes detected by the TUNEL assay increases with age and might thus contribute to the age-dependent decline in growth rate"

"in rabbits, estrogen accelerates growth plate senescence despite decelerating longitudinal bone growth"

"estrogen does not stimulate ossification of cartilage directly but instead accelerates the normal process of growth plate senescence, secondarily inducing earlier fusion"

So, this study states that estrogen can not help increase height because final height is due to a finite proliferative capacity of chondrocytes within the growth plates.  What does that mean for Lateral Synovial Joint Loading? 

Fundamental limits on longitudinal bone growth: growth plate senescence and epiphyseal fusion. 

"The decline in [long bone] growth rate is caused primarily by a decrease in the rate of chondrocyte proliferation and is accompanied by structural changes in growth plate cartilage. This programmed senescence does not appear to be caused by hormonal or other systemic mechanisms but is intrinsic to the growth plate itself. In particular, recent evidence indicates that senescence might occur because stem-like[mesenchymal red bone marrow stem] cells in the resting zone have a finite proliferative capacity, which is exhausted gradually. In some mammals, including humans, proliferative exhaustion is followed by epiphyseal fusion, an abrupt event in which the growth plate cartilage is replaced completely by bone." 

Lateral synovial joint loading helps transport new stem-like cells to the resting zone by distracting the growth plates and increasing interstitial fluid flow which sends red bone marrow stem cells into the growth plates thus potentially restoring proliferative capacity!  Here's a study that states that estrogen inhibition does not impact final height and only growth rate: 

Depletion of resting zone chondrocytes during growth plate senescence. 

"With age, the growth plate undergoes senescent changes that cause linear bone growth to slow and finally cease. Based on previous indirect evidence, we hypothesized that this senescent decline occurs because growth plate stem-like cells, located in the resting zone, have a finite proliferative capacity that is gradually depleted. Consistent with this hypothesis, we found that the proliferation rate in rabbit resting zone chondrocytes (assessed by continuous 5-bromo-2'-deoxy-uridine labeling) decreases with age, as does the number of resting zone chondrocytes per area of growth plate. Glucocorticoid excess slows growth plate senescence. To explain this effect, we hypothesized that glucocorticoid inhibits resting zone chondrocyte proliferation, thus conserving their proliferative capacity. Consistent with this hypothesis, we found that dexamethasone treatment decreased the proliferation rate of rabbit resting zone chondrocytes and slowed the numerical depletion of these cells. Estrogen is known to accelerate growth plate senescence. However, we found that estradiol cypionate treatment slowed resting zone chondrocyte proliferation. Our findings support the hypotheses that growth plate senescence is caused by qualitative and quantitative depletion of stem-like cells in the resting zone and that growth-inhibiting conditions, such as glucocorticoid excess, slow senescence by slowing resting zone chondrocyte proliferation and slowing the numerical depletion of these cells, thereby conserving the proliferative capacity of the growth plate[i.e. estrogen only slows down growth rate, it does not eliminate the proliferate capacity of the growth plate]. We speculate that estrogen might accelerate senescence by a proliferation-independent mechanism, or by increasing the loss of proliferative capacity per cell cycle." 

"the resting zone chondrocytes serve as a pool of stem-like cells that generate columnar clones of proliferative zone chondrocytes"

"Estrogen treatment did not significantly affect the number of resting zone chondrocytes"  "Serum estradiol concentration, measured 7 days after the second injection of estradiol cypionate, was 11 ± 2 pg/mL, compared to < 5 pg/mL in animals treated with the vehicle. Estrogen treatment did not significantly affect serum IGF-I concentration (88 ± 6 ng/mL vs 108 ± 6 ng/mL, estrogen vs control, P=NS)."<-This amount seems significant to me though.

"The decline in number of resting zone chondrocytes could also affect growth rate by a paracrine mechanism. For example, a decrease in the number of resting zone chondrocytes might decrease the overall production of parathyroid hormone-related protein (PTHrP), which could lead to earlier hypertrophy of proliferative zone chondrocytes."

"[estrogen] decreased proliferation rate and had no significant effect on cell numbers"  No obvious mechanisms as to how estrogen affects growth plate senescence were observed.

"We speculate that estrogen might increase the loss of proliferative capacity that occurs with each cell cycle, or that estrogen might cause loss of proliferative capacity by a cell-cycle-independent mechanism. For example, if senescence is caused by epigenetic changes such as loss of DNA methylation with each cell cycle, then estrogen might act by decreasing expression of maintenance methylases, causing greater loss of methylation with each cell replication. The effects of estrogen on the resting zone chondrocytes could be mediated by the estrogen receptor-α or -β, both of which are expressed by resting zone chondrocytes in humans, rabbits, and rats. The combination of a decreased rate of growth (in most mammals) and an increased rate of senescence seems to be an effect specific to estrogen"

"Estrogen appears to accelerate growth plate senescence without accelerating resting zone chondrocyte proliferation or accelerating the numerical depletion of these cells"<-Thus estrogen may decrease height.

They do state however that estrogen might accelerate growth plate fusion by a method not dependent on proliferation or that estrogen might reduce final height by another mechanism. 

17β-Estradiol regulates rat growth plate chondrocyte apoptosis through a mitochondrial pathway not involving nitric oxide or MAPKs.

"Estrogens cause growth plate closure in both males and females, by decreasing proliferation and inducing apoptosis of postproliferative growth plate chondrocytes. In vitro studies using 17β-estradiol (E(2)) conjugated to bovine serum albumin (E(2)-BSA) show that rat costochondral growth plate resting zone chondrocytes also respond to E(2). Moreover, they are regulated by E(2)-BSA via a protein kinase C and ERK MAPK signaling pathway that is functional only in female cells.  Rat resting zone chondrocytes cells were treated with E(2) or E(2)-BSA. E(2) caused apoptosis in male and female resting zone and growth zone chondrocytes in a dose-dependent manner, based on elevated DNA fragmentation, terminal deoxynucleotidyl transferase dUTP nick end labeling staining and caspase-3 activation[Now you don't really want apoptosis in the resting zone but still studies have shown positive benefits from lower estrogen levels and these rats could have already been above equilibrium estrogen]. E(2) also up-regulated p53 and Bax protein (Bcl-2-associated X protein) levels and induced release of cytochrome C from the mitochondria, indicating a mitochondrial apoptotic pathway. The apoptotic effect of E(2) did not involve elevated nitric oxide production or MAPKs. It was reduced by ICI 182780, which is an estrogen receptor (ER) antagonist and blocked by antibodies to Erα36, a membrane-associated ER. E(2)-BSA reduced cell viability and increased caspase-3 activity; ICI 182780 had no effect, but anti-ERα36 antibodies blocked the effect. The results indicate that estrogen is able to directly affect the cell population kinetics of growth plate chondrocytes by regulating apoptosis, as well as proliferation and differentiation in both resting zone and growth zone cells."

"High doses of estrogens also induce activation of caspase-3 in the growth plate, indicating involvement of apoptosis"

"The effects of estrogen on proliferation and differentiation of rat costochondral resting zone (RC) chondrocytes involve a membrane receptor-related pathway, which acts through activation of protein kinase C (PKC) and MAPK"

"Pi[extracellular inorganic phosphate] is able to induce resting zone chondrocyte apoptosis in an NO-dependent pathway"

"Resting zone chondrocytes differ from growth zone chondrocytes with respect to their morphology, the composition of their extracellular matrix, the phospholipid composition and levels of alkaline phosphatase activity in their matrix vesicles, and the production and activity of neutral vs. acid matrix metalloproteinases"

"resting zone chondrocytes respond to the vitamin D metabolite 24R,25(OH)2D3, whereas the growth zone chondrocytes respond to 1α,25(OH)2D3. Both vitamin D metabolites are produced actively in the growth plate in a regulated way by TGFβ1 in a zone-specific manner"<-There have been evidence of Vitamin D effects on growth plates but also studies have shown that Vitamin D polymorphisms have a "negligible effect" on human height.  Vitamin D regulates IL-1, PGE2, and PKC in GP chondrocytes.

"The 1α,25(OH)2D3-dependent activation of PKC involves activation of phospholipase A2 (PLA2) and arachidonic acid production, whereas 24R,25(OH)2D3-dependent activation of PKC involves PLD activation "

"E2 caused a dose-dependent decrease in cell viability based on MTT activity and in cell number in both male and female resting zone chondrocytes [in addition to the dose dependent effects on apoptosis]"<-Note only three dosages were used so this does not disprove that there is an equilibrium level of estrogen that increases height.

E2 does not affect apoptosis by a nitric oxide or inorganic phosphate mechanism.  The apoptosis mechanism is related to caspase-3 and caspase-1.

Now here's a study that mentions Stanozol to increase cellular proliferation.  Stanozol is a controlled substance.

Stanozolol regulates proliferation of growth plate chondrocytes via activation of ERalpha in GnRHa-treated adolescent rats.

"Stanozolol (ST) is a synthetic derivative of androgen. In this study, we investigated the effects and the mechanisms of ST on the proliferation of growth plate chondrocytes isolated from adolescent rats treated with gonadotropin-releasing hormone analogue (GnRHa). Treatment with ST resulted in time- and concentration-dependent effects on proliferation[the effectiveness of Stanozol was dependent on the concentration and the time that stanozol was in the system note that it's unclear whether this is a linear relationship]. ST increased the phosphorylation level of the estrogen receptor alpha (ERalpha)[so if there was a legal substance that increased the phosphorylation of ERalpha that would be beneficial as well], but not the androgen receptor (AR). Pharmacological inhibition of ERalpha and mitogen-activated protein kinase (MAPK) attenuated the effects of ST on the proliferation of growth plate chondrocytes[If ERalpha was inhibited by other means than the effects of Stanozol were diminished(attenuated).  Also, Stanozol seems to operate along the MAPK pathway]. A molecular dynamics simulation showed hydrophobic interactions between ST and ERalpha[cartilage is hydrophillic(water loving) so stanozol is likely effective at bypassing water and getting straight to ERalpha]. These results suggested that ERalpha, but not AR, partially mediates the ST-driven proliferation of growth plate chondrocytes."

So increasing phosphorylation of ERalpha may be one way to increase height growth if the increase in cellular proliferation also increases chondrocyte proliferative capacity.

"in some patients, growth is suppressed to subnormal velocity during the GnRHa therapy."

"mini-dose of estrogen replacement can normalize the slowdown of the growth rate during GnRHa therapy in girls with CPP"

"[ST] may impair adult height"

"In pediatric patients with Turner syndrome who treated with oxandrolone, height velocity increased without significant bone age progression"

"ST promoted chondrocytes proliferation independent of the AR."  Possibly via ER or MAPK pathways

"ER α phosphorylation can mediate the promotion or inhibition of long bone growth and epiphysis fusion"

High circulating Estradiol levels may inhibit chondrogenesis:

Estradiol inhibits chondrogenic differentiation of mesenchymal stem cells via nonclassic signaling.

"The existence of intracellular and membrane-associated E2 receptors was shown at various stages of chondrogenesis. Smaller aggregates and significantly lower type II collagen and sGAG content were detected after treatment with E2 and E2-BSA in a dose-dependent manner. Furthermore, E2 enhanced type X collagen and MMP-13 expression. Compared with estradiol alone, the coincubation of ICI 182.780 with estradiol enhanced suppression of chondrogenesis. Treatment with specific GPR-30 agonists alone (G-1 and ICI 182.780) resulted in a considerable inhibition of chondrogenesis. In addition, we found an enhancement of hypertrophy by G-1. Furthermore, the specific GPR-30 antagonist G15 reversed the GPR-30-mediated inhibition of chondrogenesis and up-regulation of hypertrophic gene expression.
The experiments revealed a suppression of chondrogenesis by estradiol via membrane receptors (GPR-30)."

So reducing estradiol levels or GPR-30 receptor levels may be a way to increase height.

"MMP-13 expression was significantly up-regulated after treatment with E2 or G-1 as compared with control"<-Maybe the increase in MMP-13 expression is related in somehow to the inhibition of chondrogenesis(MMP-13 gets beat up on a lot).

"During chondrogenesis, no proliferative or apoptotic effects of estradiol were detected"

"estradiol showed a dose-dependent inhibition of 3-D chondrogenesis with macroscopically smaller aggregates as well as reduced GAG and type II collagen deposition as compared with controls. Estradiol treatment did not disturb aggregate condensation and did not completely suppress chondrogenic differentiation."<-Thus high Estradiol levels should not be the cause of lack of LSJL results but they could be the cause of the reduction of the results.

"extracellular matrix can “store” E2"<-If there's no growth plate in the epiphysis then estrogen can't really be stored there.

Here's a study that shows that estrogen may accelerate closure but that doesn't mean that inhibiting estrogen can allow you to go beyond senescence.

The role of estrogen receptor-α and its activation function-1 for growth plate closure in female mice.

"High estradiol levels in late puberty induce growth plate closure and thereby cessation of growth in humans[cessation of growth can occur before closure however]. In mice, the growth plates do not fuse after sexual maturation, but old mice display reduced longitudinal bone growth and high-dose estradiol treatment induces growth plate closure. Estrogen receptor (ER)-α stimulates gene transcription via two activation functions (AFs), AF-1 and AF-2. To evaluate the role of ERα and its AF-1 for age-dependent reduction in longitudinal bone growth and growth plate closure, female mice with inactivation of ERα (ERα(-/-)) or ERαAF-1 (ERαAF-1(0)) were evaluated. Old (16- to 19-mo-old) female ERα(-/-) mice showed continued substantial longitudinal bone growth, resulting in longer bones (tibia: +8.3%, P < 0.01) associated with increased growth plate height (+18%, P < 0.05) compared with wild-type (WT) mice. In contrast, the longitudinal bone growth ceased in old ERαAF-1(0) mice (tibia: -4.9%, P < 0.01). Importantly, the proximal tibial growth plates were closed in all old ERαAF-1(0) mice while they were open in all WT mice. Growth plate closure was associated with a significantly altered balance between chondrocyte proliferation and apoptosis in the growth plate. In conclusion, old female ERα(-/-) mice display a prolonged and enhanced longitudinal bone growth associated with increased growth plate height, resembling the growth phenotype of patients with inactivating mutations in ERα or aromatase.  ERαAF-1 deletion results in a hyperactive ERα, altering the chondrocyte proliferation/apoptosis balance, leading to growth plate closure. This suggests that growth plate closure is induced by functions of ERα that do not require AF-1 and that ERαAF-1 opposes growth plate closure."

So you actually want ERalphaAF-1 to grow taller.

"A patient with a point mutation in exon 2 of the estrogen receptor (ER)α (estrogen-resistant man) experienced a continued growth long into adulthood, but at the age of 33.5 yr his growth plates were nearly fused."<-the man grew to about 80 inches tall.

Roles of transactivating functions 1 and 2 of estrogen receptor-alpha in bone.

"estrogen receptor-α (ERα) stimulates target gene transcription through two activation functions (AFs), AF-1 in the N-terminal and AF-2 in the ligand binding domain. To evaluate the role of ERα AF-1 and ERα AF-2 for the effects of estrogen in bone in vivo, we analyzed mouse models lacking the entire ERα protein (ERα(-/-)), ERα AF-1 (ERαAF-1(0)), or ERα AF-2 (ERαAF-2(0)). ERα AF-2 is required for the estrogenic effects on all parameters evaluated, whereas the role of ERα AF-1 is tissue-specific Selective ER modulators stimulating ERα with minimal activation of ERα AF-1 could retain beneficial actions."

"a normal negative feedback regulation of serum sex steroids requires an intact AF-1 and an intact AF-2 in ERα"

Tamoxifen is a selective ERalpha inhibitor but tamoxifen may decrease height.  One study found tamoxifen increasing longitudinal growth in female rats whereas the other study found tamoxifen decreasing longitudinal growth in male rats.  This could be due to differing responses to hormones or that females were more likely to be above equilibrium due to higher endogenous estrogen production.

Gender- and region-specific variations of estrogen receptor α and β expression in the growth plate of spine and limb during development and adulthood.

"The effects of ER inactivation on bone growth are sex and age dependent, and may differ between the axial and appendicular regions. In this study, the spatial and temporal expression of ERα and β in the tibial and spinal growth plates of the female and male rats during postnatal development was examined to explore the possible mechanisms. The level of mRNA was examined and compared with quantitative real-time PCR. The spatial location was determined by immunohistochemical analysis. The 1-, 4-, 7-, 12- and 16-week age stages correspond to early life, puberty and early adulthood after puberty, respectively. Gender- and region-specific differences in ERα and β expression were shown in the growth plates. Mainly nuclear staining of ERα and β immunoreactivity was demonstrated in the spinal and tibial growth plate chondrocytes for both genders. [There's a] significant effect of gender on temporal ERα and β expression and of region on temporal ERα/ERβ expression ratio. However, spatial differences of region-related ERα and β expression were not observed. Gender-related spatial changes were detected only at 16 weeks of both spine and limb growth plates. ERα and β immunoreactivity was detected in the resting, proliferative and prehypertrophic chondrocytes in the early life stage and during puberty. After puberty, ERα expression was mainly located in the late proliferative and hypertrophic chondrocytes in female, whereas the expression still extended from the resting to hypertrophic chondrocytes in males."

"a significant decrease in the length of femoral bone was observed in ERα-knockout (ERKO) females; in contrast, a slight decrease was shown in ERKO males"

"In the female rat, gonadectomy [removal of the ovaries] resulted in a bigger femur"

"In growing female rats, estrogen deficiency leads to an increase in the length of appendicular bones, while growth was normal at spine"

"Compared with WT controls, the axial skeletal growth increase was bigger than that of the appendicular in BERKO female mice"

"a significant decrease in length of lumbar vertebrae was demonstrated in ERKO male and female mice"

This study finds that ERalpha knockout may increase height:

The role of estrogen receptor α in growth plate cartilage for longitudinal bone growth.

"we developed a mouse model with cartilage-specific inactivation of ERα. Although mice with total ERα inactivation displayed affected longitudinal bone growth associated with alterations in the GH/IGF-1 axis, the skeletal growth was normal during sexual maturation in mice with cartilage-specific ERα inactivation. High-dose estradiol treatment of adult mice reduced the growth plate height as a consequence of attenuated proliferation of growth plate chondrocytes in control mice but not in cartilage-specific ERα(-/-) mice. Adult cartilage-specific ERα(-/-) mice continued to grow after 4 months of age, whereas growth was limited in control mice, resulting in increased femur length in 1-year-old cartilage-specific ERα(-/-) mice compared with control mice. We conclude that during early sexual maturation, ERα in growth plate cartilage is not important for skeletal growth. In contrast, it is essential for high-dose estradiol to reduce the growth plate height in adult mice and for reduction of longitudinal bone growth in elderly mice."

"female GPR30−/− mice displayed reduced longitudinal bone growth and reduced growth plate height"

"reduced femur and crown-rump lengths in the 17-week-old male total ERα−/− mice were associated with a significant reduction of serum IGF-1 levels (–20% ± 6% versus control littermates, p < .01), whereas serum IGF-1 levels were unchanged in Col2α1-ERα−/− mice (14% ± 7% versus control littermates, nonsignificant)."

Maybe you can increase IGF-1 levels exogenously to make up for loss of systemic ERalpha to get a total increase in height(since it will be hard to generate an ERalpha cartilage specific knockout).

The genetic basis of human height : the role of estrogen

" It has been hypothesised that estrogen functions to regulate growth plate fusion by stimulating chondrocyte apoptosis, angiogenesis and bone cell invasion in the growth plate. Another theory has suggested that estrogen exposure exhausts the proliferative capacity of growth plate chondrocytes, which accelerates the process of chondrocyte senescence, leading to growth plate fusion. The height-related genes FGFR3, CBFA1, ER and CBFA1 were screened for novel polymorphisms using denaturing HPLC and RFLP analysis. In total, 24 polymorphisms were identified. Two SNPs in ER (rs3757323 C>T and rs1801132 G>C) were strongly associated with adult male height and displayed an 8 cm and 9 cm height difference between homozygous genotypes, respectively{about 4 inches}. The TC haplotype of these SNPs was associated with a 6 cm decrease in height and remarkably, no homozygous carriers of the TC haplotype were identified in tall subjects. No significant associations with height were found for polymorphisms in the FGFR3, CBFA1 or VDR genes. Another hypothesis of this study was that estrogen exerted its effects in the growth plate by influencing chondrocyte proliferation and mediating the expression of chondrocyte marker genes. While estrogen did not dramatically alter the proliferation of the SW1353 cell line, gene expression experiments identified several estrogen regulated genes. Sixteen chondrocyte marker genes were examined in response to estrogen concentrations ranging from 10-12 M to 10-8 M over varying time points. Of the genes analysed, IHH, FGFR3, collagen II and collagen X were not readily detectable and PTHrP, GHR, ER , BMP6, SOX9 and TGF 1 mRNAs showed no significant response to estrogen treatments. However, the expression of MMP13, CBFA1, BCL-2 and BAX genes were significantly decreased. Interestingly, the majority of estrogen regulated genes in SW1353 cells are expressed in the hypertrophic zone of the growth plate{so estrogen likely affects peak chondrocyte hypertrophy and optimizing growth per hypertrophic chondrocyte}. Estrogen is also known to regulate systemic GH secretion and local GH action. At the molecular level, estrogen functions to inhibit GH action by negatively regulating GH signalling. GH treated SW1353 cells displayed increases in MMP9 mRNA expression (4.4-fold) and MMP13 mRNA expression (64-fold) in SW1353 cells{Thus MMP13 may be a pro-height protein}. Increases were also detected in their respective proteins. Treatment with AG490, an established JAK2 inhibitor, blocked the GH mediated stimulation of both MMP9 and MMP13 mRNA expression. The application of estrogen and GH to SW1353 cells attenuated GH-stimulated MMP13 levels, but did not affect MMP9 levels. Investigation of GH signalling revealed that SW1353 cells have high levels of activated JAK2 and exposure to GH, estrogen, AG490 and other signalling inhibitors did not affect JAK2 phosphorylation. Interestingly, AG490 treatment dramatically decreased ERK2 signalling, although GH did stimulate ERK2 phosphorylation above control levels. AG490 also decreased CBFA1 expression, a transcription factor known to activate MMP9 and MMP13. Finally, GH and estrogen treatment increased expression of SOCS3 mRNA{up in LSJL}, suggesting that SOCS3 may regulate JAK/STAT signalling in SW1353 cells. The modulation of GH-mediated MMP expression by estrogen in SW1353 cells represents a potentially novel mechanism by which estrogen may regulate longitudinal bone growth. "

In GH transgenic mice, SOCS2 overexpression further increases height.  BCL2 is protective against apoptosis in hypertrophic chondrocytes while Caspase 3 is pro-apoptotic.  CBFA1 induces Ihh expression.

FGFR3 knockout increases Ihh levels.  Retinoic Acid increases MMP2 and can induce chondrocyte hypertrophy.  BCL2 may increase Sox9 activity.  BCL2 knockout decreases height.  PTHrP increases BCL2 in chondrocytes.

An ERa mutation increases height in males and females.  An ERb mutation increases height in females.  BSM I(associated with VDR) knockout decreases height.  VDR mutations associated with increased height.  Vitamin D deficiency decreases CBFA1.  PPARG3 mutation that decreases activity resulted in increased height.  DRD2(associated with dopamine) knockout decreases height.  Mutation in PTHR1 increases height.

Stage specific effect of leptin on the expressions of estrogen receptor and extracellular matrix in a model of chondrocyte differentiation.

"The aim of our study was to investigate the effect of leptin on the expression of estrogen receptors and extracellular matrix in ATDC5 cells, an in vitro model of endochondral ossification. First, we quantified the physiological expressions of estrogen receptors α, β (ERα, ERβ), leptin receptor (Ob-Rb), type II and type X collagens in definite stages of endochondral ossification in ATDC5 cells using real-time PCR. Dynamic and stage specific expression characteristics of these target genes were observed. Simultaneous expressions of Ob-Rb with ERα or ERβ in ATDC5 cells were also found with dual-label confocal immunofluorescency. Then using Western blotting analysis and/or real-time PCR, we detected that, leptin treatment up-regulated the expressions of ERα, ERβ and type II collagen, but down-regulated type X collagen expression and the ERα/ERβ ratio in the chondrogenic differentiation stage. Meanwhile, leptin down-regulated the expressions of ERα, type II and type X collagens, and the ERα/ERβ ratio, but up-regulated the expression of ERβ in the hypertrophic differentiation stage. Significant positive correlation existed between ERα and type II collagen expression, and between the ratio of ERα/ERβ and type X collagen production. In summary, the crosstalk between leptin and estrogen receptor might be differentiation stage specific in ATDC5 cells."

"In a mandibular condyle organ culture model, leptin treatment increased overall condylar height"

The role of estrogen receptor α in the regulation of bone and growth plate cartilage.

"rapid responses to E2 are mediated by second messenger systems, e.g., cAMP and protein kinase A (PKA), while other responses are mediated by membrane-based ion fluxes, involving, e.g., Ca2+ and Ca2+-dependent K+ channels, which are capable of responding to estrogens"

"A mouse model, believed to lack the entire ERα (K-ERα−/−) had an opposite growth plate phenotype compared to the estrogen-resistant man, in that these mice completely fused their growth plates"

"Young adult (4 months old) female ERα−/− mice had normal longitudinal bone growth. Interestingly, old (16–19 months) female ERα−/− mice showed continued longitudinal bone growth, resulting in longer bones, associated with increased growth plate height compared with WT mice "

"male ERα−/− mice had a reduced longitudinal bone growth during sexual maturation, resulting in shorter bone length, while the male Col2α1-ERα−/− mice had a normal growth"

Membrane Effects of Sex Hormones on Growth Plates Chondrocytes 

"E2 caused rapid increases in Ca++ ion transport and activation of protein kinase C (PKC) and phospholipase A2 in female chondrocytes but not in male cells."

"Testosterone had no effect on PKC in male chondrocytes at any of the times tested, whereas DHT caused a rapid increase in PKC activity at 9 minutes that was still present at 90 minutes"

"DHT induced the PKC activity in dose dependent manner, which was significant at 10-9 to 10-7 M DHT"

 

"DHT induced PKC activity via two mechanisms: influx of extracellular Ca2+ via voltage gated calcium ion channels, and Ca2+ mobilization from the endoplasmic reticulum. Thapsigargin abolished the effect of DHT on PKC activity on a dose dependent manner"

 

"Once PKC is activated, it can initiate a protein phosphorylation cascade that ultimately affects cell differentiation."

"DHT signaling via the AR plays a role in chondrocyte maturation by increasing [35S]-sulfate incorporation, suggesting an increase in the synthesis of a sulfated proteoglycan extracellular matrix."