Look taller with equilibrium Vitamin A?

Perinatal exposure to vitamin A differentially regulates chondrocyte growth and the expression of aggrecan and matrix metalloprotein genes in the femur of neonatal rats.

"Vitamin A (VA) and its active form, retinoic acid (RA)[RA upregulates F-spondin], are regulators of skeletal development. [Does] maternal VA intake during pregnancy and lactation, as well as direct oral supplementation of neonates with VA + RA (VARA) in early life, alters neonatal bone formation and chondrocyte gene expression? Offspring of dams fed 3 levels of VA (marginal, adequate, and supplemented) for 10 wk were studied at birth (P0) and postnatal day 7 (P7). One-half of the newborns received an oral supplement of VARA on P1, P4, and P7. Tissues were collected on P0 and 6 h after the last dose on P7. Pup plasma and liver retinol concentrations were increased by both maternal VA intake and VARA. Although maternal VA did not affect bone mineralization, newborn femur length was increased with maternal VA{although Vitamin A increases chondrocyte maturation so it may just be an increase in growth rate rather than an increase in adult height}. VARA supplementation of neonates increased the length of the hypertrophic zone only in VA-marginal pups, close to that in neonates from VA-adequate dams, suggesting VARA caused a catching up of growth that was limited by low maternal VA intake. Maternal diet did not alter type X nor type II collagen mRNA. VARA-treated pups from VA-supplemented dams had reduced mRNA for aggrecan, a major component of cartilage matrix, and increased mRNA for matrix metalloproteinase (MMP)13, which catalyzes the degradation of aggrecan and collagens. Moderately high maternal VA intake combined with neonatal VARA supplementation can reduce the ratio of aggrecan:MMP, which may unfavorably alter early bone development."

"VARA increases retinol uptake and retinyl ester formation in neonatal lung to a level higher than that produced by VA or RA alone"

This points to Vitamin A increasing growth rate only and in fact too much Vitamin A may reduce aggrecan resulting in reduced long term height.

Retinoic acid and the transcription factor MafB act together and differentially to regulate aggrecan and matrix metalloproteinase gene expression in neonatal chondrocytes.

"Vitamin A (VA) and its active form, retinoic acid (RA), are regulators of skeletal development and chondrogenesis. MafB {MafB is downregulated by LSJL by 0.334 fold}, a transcription factor, has been identified as an important mediator in monocyte and osteoclast differentiation. MafB gene expression was regulated by both the VA status of the mother (VA-marginal, adequate, and supplemented diets) and by direct oral supplementation of the neonates with VARA (VA mixed with 10% RA). Expression was highest in neonates of VA-supplemented versus VA-marginal dams, and in VARA-treated versus placebo-treated neonates across all diet groups.  Primary chondrocytes derived from neonatal rat ribs were cultured in the presence of RA for up to 48 h. MafB mRNA exhibited a time- and dose-dependent increase in response to RA, while the induction of MafB mRNA was attenuated by BMS-493, a pan-RAR inverse agonist, implicating RAR signaling in the regulation of MafB. The genetic knockdown of MafB in chondrocytes using siRNA (MafB(SI) chondrocytes) abrogated the RA-induced increase in MafB expression. MafB(SI) chondrocytes expressed higher levels of aggrecan mRNA. Additionally, the increased matrix metalloproteinase (MMP)3 {MMP3 was increased 3.677 fold by LSJL} and MMP13 gene expression due to RA was attenuated in MafB(SI) chondrocytes, while total extracellular matrix staining was increased. MafB [is] a regulator of chondrocyte gene expression and matrix formation via control of aggrecan, MMP3 and MMP13 expression.  RA [regulates] MafB."

If RA exerts height decreasing effects by MafB, LSJL could counteract this as it downregulates MafB by a factor of 3.

"RA is produced from VA via a number of oxidative enzymes".  CRABP2 and CRABP1, two Retinoic Acid binders are upregulated by LSJL.  Gprc5a which is induced by RA is upregulated by LSJL.

"RA can induce chondrocyte terminal differentiation and alter extracellular matrix homeostasis though regulating the expression of genes involved in extracellular matrix, such as type X collagen, MMP3, MMP13, and aggrecan"

"RA regulates gene expression through it nuclear receptors (RARs), consisting of three subtypes, RARalpha, RARBeta, and RARGamma.  RARgamma is the most strongly expressed of the RARs in the growth plate"

"MafB contains a basic leucine zipper structure at the carboxy-terminal portion, which mediates DNA binding and subunit dimerization, involved in the regulation of gene expression."

"MafB mRNA was detected in both proliferative and hypertrophic chondrocytes"

"Exposure to VA in utero via differences in maternal dietary VA intake significantly altered the VA storage in the newborns, but only increased plasma retinol when the mother’s diet was VA supplemented. For all pups that were supplemented directly with VARA, both liver and plasma retinol were increased significantly, but to the same extent for each maternal diet."

"Neither type II nor type X collagen expression was altered by MafB knockdown"

"in untreated chondrocytes, the reduced MafB expression in the MafBSI knockdown cells resulted in increased aggrecan expression, while RA reduced aggrecan expression by more than 75% regardless of silencing of MafB"<-so inhibiting MafB may not inhibit all the height decreasing effects of RA.

"exposure to too much preformed VA (retinol), or direct exposure of the neonate to RA, can potentially “push” developing chondrocytes towards an unhealthy phenotype with an excess of MMP expression and too little aggrecan expression"

"MafB can form a heterodimeric complex with c-Fos. C-Fos plays an important role in chondrogenesis. Overexpression of c-Fos in ATDC5 cells was shown to inhibit chondroprogenitor cell differentiation in vitro, while ectopic expression of Fos in developing chicken limb buds resulted in truncation of the cartilage in the long bones due to chondrodysplasia caused by a delay in precartilagenous condensation and severely retarded terminal differentiation of these cells into hypertrophic chondrocytes"<-However c-Fos may promote chondrogenesis.

How RA byproducts like CRABP affect height?

Endogenous retinoids in mammalian growth plate cartilage: analysis and roles in matrix homeostasis and turnover.

"The growth plate contains resting and proliferating chondrocytes in its upper zones (UGP) and maturing and hypertrophic chondrocytes in its lower zones (LGP). Retinoid signaling [is] nearly absent in UGP, but to be much stronger in LGP coincident with hypertrophy, extracellular matrix turnover and endochondral bone formation. The upper two-thirds and lower one-third of rabbit rib growth plates were microsurgically isolated.  The UGP samples contained only about a 0.6 nm concentration of all-trans-retinoic acid (atRA) that is the most active natural retinoid in tissues, whereas LGP samples contained nearly 3-fold higher atRA levels (about 1.8 nM). Perichondrium was quite rich in atRA (about 4.9 nM). Retinol [levels], the major but inactive atRA precursor, were similar in all tissues (1.1-1.6 μM). Distinct atRA levels in UGP and LGP reflect different retinoid anabolic capacity.  RALDH2 and CRABP1{up in LSJL} transcript levels were much higher in LGP than UGP samples. Chondrogenic cells transfected with a retinoic acid response element (RARE)-luc reporter plasmid were treated with different concentrations of exogenous atRA (0-100 nM). About 3 nm atRA was needed to elicit appreciable RARE-luc reporter activity and to decrease proteoglycan synthesis and activity of an aggrecan enhancer reporter plasmid.  (i) the endogenous levels of atRA are significantly higher in hypertrophic than upper zones of growth plate; (ii) such difference reflects distinct retinoid anabolic capacity; (iii) atRA levels in hypertrophic portion are within effective ranges to elicit retinoid signaling and action, but those in upper zones are not."

"overexpression of a constitutive active form of RARα or excess intake of atRA cause skeletal deformities"

"mouse embryos lacking RARγ or both RARα and RARγ were found to exhibit growth retardation, malformations, and homeotic transformations in their skeletons"

"unliganded RARγ stimulates aggrecan synthesis in cultured chondrocytes"<-The more RAR-gamma, the more likely it is to be unliganded.

"RARγ may act as an unliganded receptor in UGP where it would favor proteoglycan expression and matrix accumulation"

"expression levels of Cyp26a1 (one of the enzymes regulating atRA degradation) and CRABP-I and CRABP-II (the main cellular atRA-binding proteins) were most prominent in perichondrium, LGP, and AC but were low in UGP and resting cartilage. CRABP-II expression was appreciable in UGP and resting cartilage as well, but CRABP-I was not"  CRABP2 expression was expressed 1.5 fold higher than CRABP1 expression in LSJL indicating that LSJL resulted in more upper growth plate cartilage and more resting zone cartilage.

"the hypertrophic zone expresses higher levels of CRABPs that could also facilitate diffusion and accumulation of the hydrophobic retinoids"

Retinoic acid receptor alpha function in vertebrate limb skeletogenesis: a modulator of chondrogenesis., states that RAR alpha downregulation is essential for chondroinduction.

Modulation of limb bud chondrogenesis by retinoic acid and retinoic acid receptors., states that RAR-Beta2 may be chondroinhibitive.  Exogenous RA enhances RAR-Beta2 production.  The study also found chondrinhibitive effects from RARbeta1&3, RARalpha2, and RARgamma1.  Only inhibition of RAR-Beta2 reversed the height decreasing effects of RA.  However, another study found that RAR-Beta2 inhibition did not inhibit the height decreasing effects.

Pharmacological regulation of adult stem cells: chondrogenesis can be induced using a synthetic inhibitor of the retinoic acid receptor.

"Retinoic acid receptor beta (RAR beta) [is] a potential pharmacological target. A low molecular weight synthetic inhibitor of the RAR alpha and RAR beta receptors was able to induce chondrogenic differentiation of mesenchymal stem cells derived from osteoarthritis patients, in the absence of serum and growth factors. the pathway is independent of SOX9 upregulation and does not lead to hypertrophy. When mesenchymal cells were seeded on to polyglycolic acid scaffolds and cultured with LE135, there was a dose-dependent formation of cartilage, demonstrated  by analysis of the collagen component of the extracellular matrix."

"in LE135 cultures, there was no significant inhibition of aggrecan or type II collagen mRNA expression, even though SOX9 mRNA was successfully knocked down"<-thus a RARbeta & RARalpha inhibitor has an additive effect on Sox9 based chondrogenesis.

"with LE135, there was minimal type X collagen mRNA expression"

"RARβ is downregulated upon TGF-β3-driven chondrogenic differentiation of human BMSCs."

Although The role of retinoic acid receptor inhibitor LE135 on the osteochondral differentiation of human bone marrow mesenchymal stem cells., suggests that LE135 and TGF-Beta are not synergestic.  "LE135 actually inhibited the chondrogenic response caused by exogenous TGF-β, or endogenous TGF-β induced by mechanical load".  "Addition of LE135 to TGF-β1 cultured pellets down-regulated the gene expression of COL2, AGG, COL10, and TGFB1 compared to pellet group"

Potent inhibition of heterotopic ossification by nuclear retinoic acid receptor-γ agonists.

"Heterotopic ossification was essentially prevented in mice receiving a nuclear retinoic acid receptor-γ (RAR-γ) agonist[activator] {So RARgamma may have chondroinhibitory effects}. Side effects were minimal, and there was no significant rebound effect. We treated mouse mesenchymal stem cells with an RAR-γ agonist and transplanted them into nude mice. Whereas control cells formed ectopic bone masses, cells that had been pretreated with the RAR-γ agonist did not, suggesting that they had lost their skeletogenic potential. The cells became unresponsive to rBMP-2 treatment in vitro and showed decreases in phosphorylation of Smad1, Smad5 and Smad8 and in overall levels of Smad proteins {Smad1 was downregulated by LSJL and Smad9 which is related to Smad8 was upregulated by LSJL}. An RAR-γ agonist blocked heterotopic ossification in transgenic mice expressing activin receptor-like kinase-2 (ALK2) Q207D, a constitutively active form of the receptor that is related to ALK2 R206H found in individuals with fibrodysplasia ossificans progressiva."

TGIF may be a way to inhibit RA's chondroinhibitive effects.

Negative functional interaction of retinoic acid and TGF-beta signaling mediated by TG-interacting factor during chondrogenesis.

"atRA (all-trans Retinoic Acid, atRA) inhibites chondrogenesis by downregulation of TGF-beta/Smad signaling. atRA suppressed chondrogenesis and Smad2/3 phosphorylation regardless of the presence of TGF-beta3. TGF-beta3 treatment or co-transfection of expressing Smad2/3 vectors suppressed atRA-induced RARE-tk-Luc activity. atRA or RAR-overexpression repressed TGF-beta3-induced transactivation of the TGF-beta-responsive reporter, p3TP-Lux. Smad transcriptional co-repressor TGIF [also known as IL10] (TG-interacting factor, TGIF) [binds] to RARbeta promoter in control MMCs, but this association was decreased by the addition of RA and increased by TGF-beta3, respectively. TGIF exerted a pivotal role in regulating crosstalk of RA and TGF-beta signaling, since siRNA knockdown of TGIF partially abolished the ability of atRA to suppress TGF-beta3-induced chondrogenesis, whereas forced expression of TGIF blocked the ability of TGF-beta3 to relieve atRA-mediated the suppression of chondrogenesis.  The effects of atRA on TGF-beta-dependent gene activation and of TGF-beta on RA-dependent gene activation are mediated by TGIF with siRNA to downregulate TGIF."

"RARs are associated with RXRs to form RAR-RXR heterodimers which bind target RARE.  Members of the RAR family recognize two natural stereoisomers of RA, all-trans RA (atRA) and 9-cis RA, whereas the RXR family exclusively recognizes 9-cis RA."

tellurium compound AS101 (ammonium trichloro(dioxoethylene-o,o′)tellurate) may be a TGIF inhibitor according to Inhibition of Interleukin-10 by the Immunomodulator AS101 Reduces Mesangial Cell Proliferation in Experimental Mesangioproliferative Glomerulonephritis ASSOCIATION WITH DEPHOSPHORYLATION OF STAT3.

Genetic deletion of Cyp26b1 negatively impacts limb skeletogenesis by inhibiting chondrogenesis.

"Cyp26b1, a retinoic acid (RA)-metabolising enzyme, is expressed in the developing limb bud, and Cyp26b1(-/-) mice present with severe limb defects. These malformations might be attributable to an RA-induced patterning defect; however RA [may be] dispensable for limb patterning. In this study, we examined the role of endogenous retinoid signalling in skeletogenesis using Cyp26b1(-/-) mice and transgenic mice in which Cyp26b1 is conditionally deleted under control of the Prrx1 promoter beginning at ~E9.5 (Prrx1Cre(+)/Cyp26b1(fl/fl)). We found that the limb phenotype in Prrx1Cre(+)/Cyp26b1(fl/fl) mice was less severe than that observed in Cyp26b1(-/-) animals and that a change in retinoid signalling contributed to the difference in phenotypes. We examined the role of endogenous RA signalling in chondrogenesis and found that Cyp26b1(-/-) cells and limb mesenchymal cells treated with a CYP inhibitor, are maintained in a pre-chondrogenic state, exhibit reduced chondroblast differentiation and have modestly accelerated chondrocyte hypertrophy. Cyp26b1(-/-) mesenchyme exhibited an increase in expression of genes in a closely related tendogenic lineage.  Retinoid signals in the limb interfere with differentiation and maintain progenitor status."

"analysis of Rara,Rarg and Rarb,Rarg double knockouts has shown that RAR-mediated repression is essential for growth plate function and cartilage matrix homeostasis"

"the retinaldehyde dehydrogenases (RALDHs: ALDH1A1, ALDH1A2 and ALDH1A3{down in LSJL}) and CYP26 enzymes (CYP26a1, CYP26b1, CYP26c1), which synthesise and degrade RA"

"in the absence of Cyp26b1, Cyp26a1 and Crabp2 expression increased, and Aldh1a2 expression decreased, probably to compensate for increased levels of RA"

"although there is little change in Sox9 expression between wild-type and Cyp26b1−/− cultures, the expression of condensation markers Vcan{up} and Tnc{down} is maintained or increased in null cultures "

"the mesenchyme from Cyp26b1−/− limbs{So Vitamin A transgenic} forms discrete prechondrogenic condensations in which chondroblast differentiation (and thus progression from the condensation stage) appears to be impaired."

"the expression of extracellular matrix molecules such as Col2a1, Acan, Hapln1, Comp and Matn1 were significantly decreased [when VitA degradation was inhibited]"

"this treatment led to a significant decrease in the expression of Ihh, Pthrp and Ptch1"

"Decreased expression of Pthrp has been shown to accelerate chondrocyte hypertrophy and consistent with this, ketoconazole treatment induced precocious expression of Col10a1, Mmp13, Spp1 and Vegfa expression in day 1 and/or 3 cultures"

"Analysis of tendon markers in Cyp26b1−/− PLM culture by qPCR revealed a modest increase (less than twofold) in Scx{up}, Tnmd{up over six fold} and Col1a1{up} expression, and other markers of tendon development in null cultures"

"a lack of Cyp26b1 negatively impacts chondrogenesis and tendogenesis before the onset of Ihh and Mkx expression"

"RA is probably maintaining mesenchymal progenitors in part through the upregulation of genes such as Twist1 and Fgf18 (a putative direct RAR target gene), both of which repress chondroblast differentiation "

Effects of retinoic acid on the differentiation of chondrogenic progenitor cells, ATDC5.

"Chondroprogenitor cells, ATDC5 have been shown to be a useful in vitro model for examining the multiple step differentiation of chondrocytes. [How does] RA [regulate] chondrogenesis [in an] ATDC5 cell culture? RA suppresses the cell growth, cartilage nodule formation, accumulation of proteoglycan, alkaline phosphatase (ALPase) activity and mineralization and that RA dose dependently upregulates the levels of type X collagen and matrix metalloproteinase-13 (MMP-13) mRNA which are marker proteins of hypertrophic chondrocytes, in ATDC5 cells. The addition of protein synthesis inhibitor, cycloheximide (CHX), partially inhibits the induction of type X collagen and MMP-13 mRNA by RA.  RA upregulates the mRNA level of Runx2/Cbfa1 (type II), a positive regulator for mineralization, and downregulates the mRNA of Indian hedgehog (Ihh), parathyroid hormone related protein (PTHrP), negative regulators for terminal differentiation. RA downregulates ALPase, bone gla protein (BGP) mRNAs and mineralization.  RA stimulates cartilage differentiation, however, cell condensation and cartilage nodule formation may be candidates of primary importance in the terminal differentiation of chondrocytes."

BMP action in skeletogenesis involves attenuation of retinoid signaling.

"We have identified the gene for the retinoic acid (RA) synthesis enzyme Aldh1a2{LSJL downregulates Aldh1a3} as a principal target of BMP signaling; prochondrogenic BMPs or GDFs lead to attenuation of Aldh1a2 expression and, consequently, to reduced activation of the retinoid signaling pathway. Antagonism of retinoid signaling phenocopies BMP4 action, whereas RA inhibits the chondrogenic stimulatory activity of BMP4. BMP4 also down-regulates Aldh1a2 expression in organ culture and, consistent with this, Aldh1a2 is actively excluded from the developing cartilage anlagens."

"RA influences the expression and/or activity of Sox9"

"mesenchymal cells isolated from a transgenic animal overexpressing a weak, constitutively active Rara transgene exhibit skeletal defects, and this, in part, results from delayed or inhibited chondroblast differentiation "

"BMPs decrease RA availability, and that this is required for their prochondrogenic function"

"the addition of BMP4 generates a dose-dependent increase in endogenous SOX9 activity"

"Aldh1a2 and Cyp26a1, which are genes encoding enzymes involved in the synthesis and degradation of all-trans RA (atRA), respectively, exhibit the largest decreases at 24 h (14.8- and 7.3-fold, respectively). Interestingly, other RA synthesis enzymes, Aldh1a1 and Aldh1a3, are unaffected by BMP4 addition"

"The expression of retinol and RA-binding proteins, Rbp1 and Crabp2{LSJL upregulates this 3.5 fold}, and the RA-responsive receptor Rarb are also observed to be substantially decreased at 24 and 72 h after BMP addition"

"heterologous expression of Ncor2{downregulated by LSJL} or Ncor2 and Rara together increases SOX9 activity by ∼2- and 10-fold, respectively."

"overexpression of either of the BMP receptor (Bmpr) type I receptors, a or b, stimulates SOX9 activity, and this is associated with a reduction in RARE-luc activity"<-LSJL upregulates BMPR1b.

Retinoic acid is a potent regulator of growth plate chondrogenesis.

"a single oral dose of RA reduced the height of the rat proximal tibial growth plate. Fetal rat metatarsal bones were cultured in the presence of RA. In this system, RA inhibited longitudinal bone growth by three mechanisms: 1) decreased chondrocyte proliferation, particularly in the proliferative zone of the growth plate; 2) decreased matrix synthesis; and 3) decreased cell hypertrophy. The growth-inhibiting effects of RA were completely reversed by a retinoic acid receptor (RAR) antagonist. In the absence of exogenous RA, this antagonist accelerated bone growth, as did an RA-specific neutralizing antibody, suggesting that endogenous RA negatively regulates growth plate chondrogenesis. "

"Cotreatment with 100-fold molar excess of AGN 193109[RAR inhibitor] not only reversed the RA-mediated inhibition of longitudinal bone growth (n = 8 per group, P < 0.01) but actually produced a growth rate greater than that of controls."

"in metatarsal bones cultured without exogenous RA, AGN 193109 caused a concentration-dependent acceleration in growth rate"

Retinoic acid inhibits chondrogenesis of mesenchymal cells by sustaining expression of N-cadherin and its associated proteins.

"RA inhibits chondrogenic differentiation of mesenchymal cells and also causes loss of differentiated chondrocyte phenotype. RA treatment in chondrifying mesenchymal cells did not affect precartilage condensation{Maybe Vitamin A could help in chondroinduction by LSJL but once growth plates are formed only maintenance RA should be used}, but blocked progression from precartilage condensation to cartilage nodule formation. This inhibitory effect of RA was independent of protein kinase C and extracellular signal-regulated protein kinase, which are positive and negative regulators of cartilage nodule formation, respectively. The progression from precartilage condensation to cartilage nodule requires downregulation of N-cadherin expression. However, RA treatment caused sustained expression of N-cadherin and its associated proteins including alpha- and beta-catenin suggesting that modulation of expression of these molecules is associated with RA-induced inhibition of chondrogenesis. disruption of the actin cytoskeleton by cytochalasin D (CD) blocks RA-induced sustained expression of cell adhesion molecules and overcomes RA-induced inhibition of chondrogenesis. RA inhibits chondrogenesis by stabilizing cell-to-cell interactions at the post-precartilage condensation stage."

"Dissociated limb bud mesenchymal cells undergo differentiation to chondrocytes in vitro when cells are cultured at high density. Both in vivo and in vitro chondrogenesis is initiated by precartilage condensation via cell-to-cell adhesion. N-cadherin, a key Ca2+-dependent cell adhesion molecule, mediates cell-to-cell adhesion in association with α- and β-catenin"<-LSJL upregulates several adhesion molecules.

"PKCα positively affects chondrogenesis of mesenchymal cells by regulating expression of cell adhesion molecules such as N-cadherin, fibronectin, and its receptor α5β1 integrin, leading to progression from precartilage condensation to cartilage nodules. PKC-dependent regulation of chondrogenesis is exerted via MAP kinase subtype ERK-1. The pattern of ERK-1 activation is inversely related to expression and activity of PKCα. It was found that increased expression and activation of PKC was required for downregulation of ERK-1 activity, which correlated with induction of chondrogenic differentiation of mesenchymal cells. In addition, inhibition or downregulation of PKC (conditions that inhibit chondrogenesis) resulted in activation of ERK-1, while inhibition of ERK-1 with PD98059 blocked the inhibitory effects of PKC downregulation on chondrogenesis"

"phosphorylation of ERK-1 was reduced during chondrogenesis. RA treatment had no effect on ERK activation"

"inhibition of ERK with PD98059 did not affect RA-induced inhibition of type II collagen expression and accumulation of sulfated proteoglycans"

"In addition to PKC and ERK signaling, chondrogenesis requires PKA and p38 MAP kinase activity. We have previously shown that ERK and p38 MAP kinase regulate chondrogenesis by conversely modulating expression of N-cadherin at the post-precartilage condensation stage in a manner independent of PKCα. PKA activation is an upstream event required for PKCα activity at the post-precartilage condensation stage."

"inhibition of RAR that is necessary and sufficient for chondrogenesis results in activation of PKA and p38 MAP kinase, and chondrogenesis induced by inhibition of RAR is blocked by inhibition of PKA and p38 MAP kinase. In contrast, inhibition of chondrogenesis induced by RAR activation is rescued by activation of PKA and p38 MAP kinase"

" CD treatment enhanced chondrogenesis" "[CD treatment] changes actin organization and functions as a signal in the modulation of chondrocyte phenotype"

SOX9 enhances aggrecan gene promoter/enhancer activity and is up-regulated by retinoic acid in a cartilage-derived cell line, TC6.

"TC6 is a clonal chondrocytic cell line derived from articular cartilage. SOX9 overexpression in TC6 cells enhanced by approximately 3-fold the transcriptional activity of the AgCAT-8 construct containing 8-kilobase (kb) promoter/first exon/first intron fragments of the aggrecan gene. SOX9 enhancement of aggrecan promoter activity was lost when we deleted a 4.5-kb fragment from the 3'-end of the 8-kb fragment corresponding to the region including the first intron. In TC6 cells, SOX9 enhanced the transcriptional activity of a reporter construct containing the Sry/Sox consensus sequence >10-fold. SOX9 enhancement of aggrecan gene promoter activity and SOX9 transactivation through the Sry/Sox consensus sequence were not observed in osteoblastic osteosarcoma cells (ROS17/2.8), indicating the dependence on the cellular background. TC6 cells constitutively express Sox9 mRNA at relatively low levels. retinoic acid (RA) specifically enhanced Sox9 mRNA expression in TC6 cells. The basal levels of Sox9 expression and its enhancement by RA were observed similarly at both permissive (33 degrees C) and nonpermissive (39 degrees C) temperatures. RA treatment enhanced the transcriptional activity of a reporter construct containing the Sry/Sox consensus sequence in TC6 cells. RA treatment also enhanced the transcriptional activity of another reporter construct containing the enhancer region of the type II procollagen gene in TC6 cells. SOX9 enhances aggrecan promoter activity and its expression is up-regulated by RA in TC6 cells."

"Mice with a phenotype known as cartilage matrix deficiency (Cmd) have been found to possess an autosomal recessive mutation in the aggrecan gene. These mice exhibit cleft palate and short limbs, tail, and snout, whereas their levels of type II collagen and link protein are normal."

"The cells were cultured in the absence or presence of 1 μM RA for 1, 2, and 3 days. RA reduced TC6 cell numbers by 22% on day 2 and by 40% on day 3. RA-mediated reduction of TC6 cell proliferation was observed in a dose-dependent manner after 3 days of treatment"

Retinoic acid upregulates preadipocyte genes to block adipogenesis and suppress diet-induced obesity.

"[RA induces] activation of the nuclear receptors RA receptors (RARs) and peroxisome proliferator-activated receptor β/δ and their associated binding proteins cellular RA binding protein type II (CRABP-II){up in LSJL} and fatty acid binding protein type 5 in adipocytes and skeletal muscle, leading to enhanced lipid oxidation and energy dissipation.  RA inhibits differentiation of cultured preadipocytes. RA inhibits adipocyte differentiation by activating the CRABP-II/RARγ path in preadipose cells, thereby upregulating the expression of the adipogenesis inhibitors Pref-1, Sox9, and Kruppel-like factor 2 (KLF2). KLF2 induces the expression of CRABP-II and RARγ, further potentiating inhibition of adipocyte differentiation by RA."

"interference with adipogenesis by RA involves Smad3"

"SOX9 blocks adipogenesis by repressing the expression of the adipogenic factors CCAAT/enhancer binding protein (C/EBP) β and C/EBPδ"

"RA treatment blunted diet-induced elevation in levels of plasma cholesterol"

Premature epiphyseal closure in an adolescent treated by retinoids for acne: an unusual cause of anterior knee pain.

"Retinoids are effective and widely prescribed in the treatment of severe acne. However their use can be associated with premature epiphyseal closure. We present the case of a sixteen-year-old soccer player referred for progressive anterior pain in both knees, evoking a patellar problem. Careful pharmacological questioning revealed use of isotretinoin[Accutane is a form of isotretinoin] for several months. MRI findings showed an irregularity of the growth plate and an important metaphyso-epiphyseal oedema, more noticeable in the left knee. Retinoid-induced premature epiphyseal closure was diagnosed. The treatment was stopped, with a resolution of pain within two months. After recovery a persisting small sequelar thumbprint-like growth plate lesion was observed on the control MRI. Retinoids induce an invasion of the growth plate by osteoclasts and a decrease in proteoglycans synthesis. It seems that the knee is the most affected joint."

"the administration of 0.75 mg/kg of 13-cis retinoic acid for 6 months in the treatment of acne was diagnosed to date as premature epiphysiodesis"

"Usually, withdrawal of the acne treatment will quickly alleviate the pain and allow normal growth."