Good new paper on growth plate therapeutics

Evolution and future of growth plate therapeutics

“Longitudinal bone growth is regulated by multiple endocrine signals (e.g. growth hormone, insulinlike growth factor I, estrogen, androgen) and local factors (e.g. fibroblast growth factors and their receptors and the C-natriuretic peptide/NPR-2 pathway).”

“The resting zone chondrocytes, farthest from the primary ossification center, replicate at a slow rate and act as stem-like cells that replenish the pool of proliferative chondrocytes{if we can reintroduce these resting zone chondrocytes we may be able to reopen the growth plate}. Resting zone chondrocytes produce a ‘growth plate-orienting factor’ that instructs the proper spatial orientation of adjacent proliferative chondrocytes. As cells within the resting zone divide, the proliferative zone is formed in which chondrocytes replicate at a high rate, become arranged into columns, and contribute to bone elongation. Hypertrophic chondrocytes generated from terminal differentiation of proliferating zone chondrocytes enlarge in columns parallel to the axis of elongation. Cell swelling during chondrocyte hypertrophy enables chondrocytes within the growth plate to enlarge rapidly. This phase of endochondral ossification, during which chondrocytes increase their height about 6- to 10-fold, serves as the major factor regulating the growth rate amongst endochondral bones. Hypertrophic chondrocytes calcify surrounding extracellular matrix and produce factors that attract bone cell precursors, bone cells and blood vessel growth, and undergo apoptosis shortly before the blood vessels invade the chondrocyte lacuna. The overall effect of this process of chondrocyte proliferation, hypertrophy, and extracellular matrix secretion is elongation of bones and progressive creation of new bone tissue at the bottom of the growth plate. With age, the rate of longitudinal bone growth declines, caused primarily by a decrease in chondrocyte proliferation associated with other hormone-independent structural, functional, and molecular changes termed growth plate senescence. Evidence suggests that growth plate senescence occurs because the progenitor chondrocytes in the resting zone have a limited replicative capacity – gradually exhausted with increasing cell division{things like estrogen and FGFR3 may contribute to reducing the replicative capacity}.  When the proliferative capacity of stem-like cells in the resting zone is exhausted, and in the presence of sex hormones, growth plate cartilage becomes completely replaced by bone, an event termed epiphyseal fusion”

” According to the dual-effector hypothesis, GH promotes recruitment of resting chondrocytes into a proliferative state and stimulates local production of IGF-I, which then acts in a paracrine/autocrine fashion to increase chondrogenesis. The IGF-I signaling pathway plays an important role in promoting complete hypertrophic chondrocyte formation. These effects are predominantly due to growth plate-generated IGF-I, and IGF-I deficiency results in pre- and post-natal growth retardation marked in the growth plate by disorganized columnar chondrocytes, decreased cell proliferation and cell hypertrophy, increased apoptosis, and delayed vascular invasion. ”

“Estrogen influences longitudinal growth primarily and indirectly by augmenting GH secretion during puberty, but also through both growth-enhancing and -attenuating direct actions on the growth plate. A direct effect of estrogen is to advance growth plate senescence causing proliferative exhaustion, and thus epiphyseal fusion. An important mediator of this growth plate closure process is vascular endothelial growth factor (VEGF), the production of which is stimulated by estrogen in both males and females. Androgens stimulate linear growth partly due to aromatization to estrogens within growth plate cartilage, but also by direct interaction with androgen receptors on growth plate chondrocytes – explaining the GH- and IGF-I-independent growth stimulating effects of non-aromatizable compounds such as dihydrotestosterone and oxandrolone. Linear growth is slowed by deficiency of and accelerated by excess thyroid hormone. Hypothyroidism indirectly impedes linear growth by diminishing GH secretion and IGF-I, but also by decreasing chondrocyte proliferation and hypertrophy, slowing of vascular/bone cell invasion, and disruption of column organization. Glucocorticoid (GC) excess slows longitudinal bone growth by inhibiting chondrocyte proliferation, hypertrophy, and cartilage matrix synthesis. Diminished GH secretion and/or altered IGF-I bioavailability have been described in some GCtreated patients. Slowing of growth plate senescence due to GC appears to explain the phenomenon of catch-up growth following transient GC exposure and hypothyroidism.”

“Members of the FGF family of receptors (FGFRs) and their ligands are required for proper chondrocyte function, endochondral ossification and overall skeletal development. Proliferative chondrocytes express FGFR3 and prehypertrophic/hypertrophic chondrocytes express FGFR1. These pathways inhibit the proliferation of chondrocytes, thereby limiting the longitudinal growth of bones. Thus, activating mutations in FGFRs impede linear growth and cause skeletal phenotypes such as achondroplasia and hypochondroplasia. Accelerated linear growth and epiphyseal growth plate maturation in obese children, even in the setting of decreased GH production may be due to effects of increased insulin concentrations and activation of the insulin receptor in the growth plate. Leptin, increased in obese children, has direct effects on skeletal growth centers, enhancing chondrocyte proliferation and subsequent cell differentiation. Leptin also increases growth plate aromatase activity{this may explain why some obese children are taller than normal and others are shorter based on differential responses to estrogen} which along with estrogen produced through adipose tissue aromatization, accelerates skeletal maturation. Parathyroid hormone-related protein (PTHrP) supports chondrocytes and maintains the width of the growth plate. Mutations affecting PTHrP action (e.g. Gs-alpha) can result in a shortening of the proliferating zone, accelerated differentiation of hypertrophic chondrocytes, premature closure of the growth plate, and short stature. Vitamin D facilitates normal linear growth indirectly by increasing intestinal calcium and phosphate absorption, but vitamin D metabolites produced locally in the growth plate also decrease the proliferation of chondrocytes through the PTHrP pathway. Thus, the full effect of vitamin D on the growth plate physiology is incompletely understood.”

The paper some options for treatment for increasing growth plate based growth.  I recommend reading the whole paper.  I highlighted some stuff here because it does a great job explaining the mechanics of growth plate based height increase.

Can Berberine have an impact on height?

I saw berberine as part of a height stack and wanted to see if it could have any impact. Berberine is a part of many plants so it is available to the average population. So I searched if berberine had any impact on bone or cartilage.

Possible therapeutic effects of berberine on bone damage in high-fat diet-induced obese rats

“After treatment with berberine, TNF-α, IL-1β and the number of adipocytes in bone marrow were significantly decreased, and P1NP levels were higher in the HB group than in the HFD group.”<-so berberine could be used to prevent over inflammation. I don’t know if this would have any impact in healthy individuals.

“berberine chloride exerted protective effects on bone in an osteoporotic rat model induced by ovariectomy, and berberine significantly increased femur load and stiffness in glucocorticoid treated animals”

This is the study that indicates that berberine may have a positive result on longitudinal bone growth:

Effects of Huang Bai (Phellodendri Cortex) on bone growth and pubertal development in adolescent female rats

“Female Sprague–Dawley rats (28 days old; n = 72) were divided into six daily treatment groups: control (distilled water), Huang Bai (100 and 300 mg/kg), recombinant human GH (rhGH; 20 μg/kg), estradiol (1 μg/kg), and triptorelin (100 μg).”

“Expression of IGF-1 and BMP-2 in the hypertrophic zone was higher in all experimental groups.”

“Huang Bai promoted GH mRNA and protein in pituitary cells and inhibited GnRH mRNA expression in hypothalamus cells “

“Huang Bai contained one representative component: 24.36 mg/g berberine chloride.”<-Huang Bai contains berberine.

“Longitudinal bone growth rates of the Huang Bai 100 mg/kg, rhGH, and triptorelin groups were significantly higher than that of the control group”

It does not look like higher doses of berberine had a benefit. It is important to note that the mice in these studies do not get as diverse a diet as a normal human so it’s possible that it would have no effect on a human.

“Huang Bai stimulates longitudinal bone growth and chondrocyte proliferation by upregulating BMP-2 and IGF-1 expression in the growth plate. However, it has no effects on pubertal onset and estrogenic activity.”

Berberine for bone regeneration: Therapeutic potential and molecular mechanisms

“Berberine promotes osteogenesis”

“the migration of BMSCs to target organs is also of great significance for repairing the damaged bone tissues. Berberine can promote this process by activating PI3K/AKT pathway”

“berberine can activate the expression of key osteogenic transcription factor Runt-related transcription factor 2 (Runx2) through the p38MAPKs pathway, thereby promoting bone regeneration”

“berberine was confirmed to be able to reduce the apoptosis of BMSCs and promote bone regeneration by up-regulating the expression of anti-apoptotic factor Bcl-2, down-regulating the expression of pro-apoptotic factor bax and cleaving caspase-3 in the apoptosis pathway”

“oral berberine has poor bioavailability due to the first pass effect in the intestine. Currently, there are
some solutions, such as D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), that can increase the absorption of berberine in the intestine to improve the bioavailability”

In one study mentioned by the review “Mice treated with berberine showed better cartilage surfaces
with cracks and less cartilage degradation”

So it’s possible that berberine could be used to effect height but there’s lots of things that increase BMP-2 and IGF-1. It’d have to be studied more.

IL23 inhibition may have niche applications for height growth(Tremfya)

Some questions that have to be answered for Tremfya that have to be answered to see if it influences longitudinal bone growth:

1: Does it inhibit IL-23 in an area that would affect height such as the growth plate, articular cartilage, or intervertebral discs? I don’t think reducing the action of inflammatory cytokines on bone would have any impact on height as we generally want more bone turnover to get more height.

2: Does IL-23 impact height? Is it biphasic where there needs to be an equilibrium amount. In which case Tremfya can help when IL-23 is too high.

According to the study Pro-Inflammatory Cytokines Produced by Growth Plate Chondrocytes May Act Locally to Modulate Longitudinal Bone Growth, inflammatory cytokine inhibition of IL-1Beta and TNF-Alfa increased growth. Inflammatory cytokines can cause chondrocyte apoptosis which too much of is bad but chondrocyte apoptosis is a needed a stage in endochondral ossification. It’s likely that inflammatory cytokines are needed in small quantities so knockout is bad but too much overall decreases height.

IL-23 Inhibits Osteoclastogenesis Indirectly through Lymphocytes and Is Required for the Maintenance of Bone Mass in Mice

“L-23 stimulates the differentiation and function of the Th17 subset of CD4+ T cells and plays a critical role in chronic inflammation. The IL-23 receptor-encoding gene is also an inflammatory disease susceptibility gene. IL-23 shares a common subunit with IL-12, a T cell-dependent osteoclast formation inhibitor, and we found that IL-23 also dose-dependently inhibited osteoclastogenesis in a CD4+ T lymphocyte-dependent manner. When sufficiently enriched, γδ T cells also mediated IL-23 inhibition. Like IL-12, IL-23 acted synergistically with IL-18 to block osteoclastogenesis but, unlike IL-12, IL-23 action depended on T cell GM-CSF production. IL-23 did not mediate IL-12 action although IL-12 induced its expression. Male mice lacking IL-23 (IL-23p19−/−) had ∼30% lower bone mineral density and tibial trabecular bone mass (bone volume (BV)/total volume (TV)) than wild-type littermates at 12 wk and 40% lower BV/TV at 26 wk of age; male heterozygotes also had lower bone mass. Female IL-23p19−/− mice also had reduced BV/TV. IL-23p19−/− mice had no detectable osteoclast defect in trabecular bone but IL-23p19−/− had thinner growth plate hypertrophic and primary spongiosa zones (and, in females, less cartilage remnants) compared with wild type. This suggests increased osteoclast action at and below the growth plate, leading to reduced amounts of mature trabecular bone. Thus, IL-23 inhibits osteoclast formation indirectly via T cells in vitro. Under nonpathological conditions (unlike inflammatory conditions), IL-23 favors higher bone mass in long bones by limiting resorption of immature bone forming below the growth plate.”

IL-23 knockout increases osteoclast action. It’s unclear how this would affect height at skeletal maturity.

“IL-23 is a heterodimeric cytokine structurally related to IL-12.”

“IL-23p19/ male mice develop shorter limb bones than WT:”<-so IL-23 knockout is bad as it reduces height when you’re skeletally immature. The difference in length was 8.6% which is fairly significant.

So if knockout of IL-23 is bad is too much IL-23 good or also bad(and IL-23 is biphasic)?

According to the study Linear growth and bone metabolism in pediatric patients with inflammatory bowel disease, chronic inflammation results in reduced longitudinal bone growth. But there are many inflammatory cytokines involved inflammatory bowel disease, not just IL-23.

According to Bone phenotypes in rheumatology – there is more to bone than just bone, IL-23 can cause bone destruction which may actually be good if you want to grow taller as bone is not capable of interstitial growth. Distraction osteogenesis after all begins with an osteotomy. Also of note in this study is that it’s mentioned that psoriatic osteoarthritis involves ossification of the enthesis. Tremfya is a treatment for psoriatic osteoarthritis. The study also mentions that psoriatic osteoarthritis can result in increased bone formation.

I could not find a direct link between IL-23 and longitudinal bone growth reduction just with inflammation in general. I’m going to conclude that Tremfya if it could be used as a way to increase longitudinal bone growth it is only in very niche cases where inflammation is very high.

It looks like corsets may actually cause plastic bone deformation

This is a huge find because it means that we may actually be able to pull on bones to make them longer.  Now it’s easier to deform bones by bending than it is by pulling on them but bending generates both tensile and compressive forces so you’d have to find a way to bend the bone in two parts at once to balance the compressive forces to achieve length.  Lateral compressive forces are axial tensile forces so this is why something like tapping can be beneficial to achieve length.  Don’t think that sleeping in a “rack” position can achieve this kind of pull the problem is that the pull forces are observed muscle by the muscles and ligaments which only pull the bone at the enthesis(which not surprising is longer and thicker than other parts of the bone), you’d have to find a way to generate pull directly on the bone itself.  Also, consider that sleeping in the rack position could potentially cut off circulation when you’re not awake to do anything about it.

If corsets generated bone shape increase via plastic deformation rather than traditional bone modeling with osteoclast absorption and osteoblast deposition that is a huge find because bone modeling is not likely to result in an increase in length unless osteoblast deposition occurs at the longitudinal ends of bones.

Here’s the citation:

Corsets and Skeletal Deformities: Anthropological Study

“The skeletons of 19th century corseted women were studied to see how their ribcages were flexibly bent into a more tapered shape from the corset. From the photos, you can see literal ‘bends’ in the ribs where the pressure from the corset formed the ribs into the shape of a circle. Also, the spinous processes seemed to be affected too: spinous processes are the small “spikes” humans have on their vertebrae; they look like spikes down a lizard’s back, but in humans these are small and one can occasionally see or feel them as the ‘bumps’ along one’s back. In the skeletons that showed rib shaping from a corset, these same skeletons also had “spikes” in the upper back that bent downward and overlapped like snaggleteeth.”

Corsets are basically lateral compressive loading on the ribs so should generate a minor longitudinal tensile force as well.  it’s not surprising that corsets also generate torsional and rotational forces which explain why the spinous process of the vertebrae were deformed.  But ribs are bent so it would be easier to generate stronger mechanical forces than it would be in straighter long bones.

“Gibson first chose skeletons showing classic deformation of the ribcage from the pressure of the corset (which in O’Followell’s study, pressure from the corset is shown to be measured up to 80psi). The ribs were more circular compared to an anatomically “normal” human ribcage (the “control” ribcage).”  1 psi is about 0.007 MPa.  Or about 0.56 MPa total.

Rickets can also cause deformation of the rib bones “rickets flattens the curves of the ribcage, and most of the ‘bend’ occurs at the costal joints, especially at the sternum (“pigeon chest” is common) – and in extreme cases of rickets, the pressure from one’s own arms laying at the side of the body can cause the ribcage to cave in at each side.”

 A pigeon chest looks longer than a regular chest so if we look at the principles that make a pigeon chest that may translate into longer bones.  Rickets results in less height but more bended bones.

  Since rickets bones would more malleable it would be interesting to try a bone loading deformation routine on someone with rickets.

“In the French [corset] skeletons, instead of seeing “flattened curves”, Gibson noted that the ribcage was more rounded, such that when the dimensions were measured, the coronal (front-to-back) and sagittal (side-to-side) diameters were identical (or close to it). Also, the area of the rib with the greatest bending was closer to the back of the body, not at the sides where the arms would be. Gibson said that formation was seen as high as the 4th rib (imagine right up in the armpit)  and the corset molded each successive rib consistently and uniformly. The floating ribs (11th and 12th) were sometimes affected even more.”

“I found Figure 6 of the article to be of particular interest, where a single pair of ribs shows plastic deformation of the rib (actual bending near the back), a broken area that had healed later in life, and a post-mortem breakage (obviously not healed), showing how different all of them appear.”  Now the usage of the term plastic deformation in the study studied may need indicate that plastic deformation actually occurred it may have been traditional bone modeling rather than mechanical loading resulting in permanent change in shape.

” throughout the thoracic spine, normal spinous processes are already angled slightly downward, although may not necessarily overlap. It would not be impossible for these processes to deform with regular pressure and a predisposition to softer bones,”<-it would be interesting if different shaped and designed corsets would have different affects on the shape of the spinous process.

Something like scoliosis bracing has always thought to only be beneficial during development as as a means to alter spinal development mainly through altering growth via compression and tension on the growth plate.  Something like artificial cranial deformation was thought only to work in the youth.  If something like the corset can change the spine as an adult than maybe bracing can too.

The key step is catabolism.  HGH increases bone turnover which involves both catabolism and anabolism of bone.  So we need to not only stimulate bone growth but bone degradation as well to allow the bone growth to be of a less mature cell type.

mTor: Is Rapamycin good or bad for height growth?

Rapamycin is looked at a lot in longevity research. So if rapamycin helps help height growth then it could be a supplement worth looking into. Previously looking into mtor and rapamycin showed that rapamycin made bone growth slower. However, it is conceivable that rapamycin may make bone growth slower but increase height at skeletal maturity. Although based on the information presented in the study it seems that rapamycin can not increase long bone growth

Look who’s TORking: mTOR-mediated integration of cell status and external signals during limb development and endochondral bone growth

“the role of mTOR signaling in three aspects of tetrapod limb development: 1) limb outgrowth; 2) chondrocyte differentiation after mesenchymal condensation and 3) endochondral ossification-driven longitudinal bone growth. We conclude that, given its ability to interact with the most common signaling pathways, its presence in multiple cell types, and its ability to influence cell proliferation, size and differentiation, the mTOR pathway is a critical integrator of external stimuli and internal status, coordinating developmental transitions as complex as those taking place during limb development.”

“mTOR stands for mechanistic (formerly mammalian) target of rapamycin, a macrolide produced by Streptomyces Hygroscopicus bacteria. Rapamycin was named after the island of Rapa Nui, where it was discovered in the early 1990 s during a genetic screen in the budding yeast, where TOR1 and TOR2 were identified as the toxic agents of rapamycin”

“mTORC1 signaling in the limb mesenchyme is required for the normal size of both the limb bud and its individual cells, but relatively dispensable for skeletal patterning”

“MPs have been shown to induce mTORC1 activation via the ALK3 receptor and Smad4-mediated inhibition of PTEN. mTORC1, in turn, is required for the translational control of SOX9, a key transcription factor in the progression towards cartilage. mTORC1 has been shown to upregulate HIF-1α protein levels in the cartilage, which is critical for the control of glucose metabolism, proliferation and differentiation in chondrocytes”

“mTORC1 inhibition impaired fetal chondrocyte differentiation and response to insulin, but not proliferation. Similarly, genetic deletion of either Mtor or Raptor in the mouse cartilage impaired skeletal growth through reduced matrix production, decreased chondrocyte size and delayed chondrocyte hypertrophy”

“The size of the proliferative zone is controlled by a well characterized negative feedback loop between IHH and PTHrP. In this loop, IHH produced by pre-hypertrophic chondrocytes induces PTHrP expression in resting chondrocytes, whereas PTHrP secreted from the resting zone promotes chondrocyte proliferation and delays differentiation, including Ihh expression. mTOR is likely involved in this feedback loop in two different ways: via mechanotransduction-dependent Ihh expression, and via regulation of PTHrP signaling. Regarding the former, mechanical loading is an important regulator of chondrocyte maturation, and experiments in chicken embryos showed that elimination of muscle contraction results in mTOR inhibition in the cartilaginous growth plate”

“On the other hand, mTORC1 activation has been shown to reduce expression of the PTHrP receptor in articular cartilage, which could potentially happen in the growth plate cartilage as well{perhaps it is thus mechanisms by which rapamycin could potentially increase height at skeletal maturity?}. S6K1, a downstream effector of mTORC1, phosphorylates and allows nuclear translocation of HH-signaling transducer GLI2, leading to transcription of Pthlh, encoding PTHrP. The mTOR/PTHrP interaction also works in reverse. Studies of skeletal dysplasia syndromes characterized by constitutive activation of PTH/PTHrP showed reduced activities of salt inducible kinase 3 (SIK3), which caused accumulation of DEPTOR, in turn inhibiting mTORC1 and 2 activity, biasing skeletal progenitor differentiation towards fat instead of bone. This new PTH/PTHrP-SIK3-mTOR axis has been recently explored further, showing that, in the presence of nutrients, DEPTOR directly interacts with PTH1R to regulate PTH/PTHrP signaling, whereas in the absence of nutrients it forms a complex with TAZ (an effector of the Hippo pathway), to prevent its translocation to the nucleus and therefore inhibit its transcriptional activity”

“Wnt10b overexpression causes enlargement of calvarial tissue and phosphorylation of S6, both of which effects were abrogated by rapamycin”<-obviously we want enlargement so rapamycin in that case is bad.

Interesting paper on how periosteal stem cells impact growth plate development

I’m not sure how this can be applied in practice but since periosteum is on the surface of the bone and it is easier to stimulate the surface of the bone than the interior of the bone this could have some practical implications.  For example, a foam roller could be used to stimulate the periosteum.

Periosteal stem cells control growth plate stem cells during postnatal skeletal growth

“The ontogeny and fate of stem cells have been extensively investigated by lineage-tracing approaches. At distinct anatomical sites, bone tissue harbors multiple types of skeletal stem cells, which may independently supply osteogenic cells in a site-specific manner. Periosteal stem cells (PSCs) and growth plate resting zone stem cells (RZSCs) critically contribute to intramembranous and endochondral bone formation, respectively. However, it remains unclear whether there is functional crosstalk between these two types of skeletal stem cells. Here we show PSCs are not only required for intramembranous bone formation, but also for the growth plate maintenance and prolonged longitudinal bone growth. Mice deficient in PSCs display progressive defects in intramembranous and endochondral bone formation, the latter of which is caused by a deficiency in PSC-derived Indian hedgehog (Ihh). PSC-specific deletion of Ihh impairs the maintenance of the RZSCs, leading to a severe defect in endochondral bone formation in postnatal life. Thus, crosstalk between periosteal and growth plate stem cells is essential for post-developmental skeletal growth.”

“After four weeks of the PSC deletion, the mice exhibited an impaired periosteal bone formation with a compensatory increase in endosteal bone formation”<-this is interesting as it means that the bone compensates in growth in a mechanism in which it is not impaired.

“Ihh was among the genes highly specific to PSCs and is known to be involved in the regulation of endochondral bone formation”<-so then an interesting study would be to compensated for PSC deletion via increasing IHH levels and see how much that rescues the impaired bone formation of the PSC deletion phenotype.  According to the study osteoclasts were not impacted so we know that inability to remodel is not one of the factors.

“During development, growth plate-derived Ihh acts on cells in the periosteum/perichondrium, leading to the activation of PTHrP expression in the periarticular chondrocytes through a poorly understood mechanism. PTHrP then maintains chondrocytes in a proliferative, less differentiated state and inhibits the production of Ihh from the growth plate. This Ihh/PTHrP loop coordinates the synchronized chondrocyte differentiation in the growth plate during early life stages”<-manipulation of IHH-PTHrP production may be able to manipulate height but it is unlikely to totally be able to do it due to other factors like for example of other nutrients required for the growth plate to grow and eventually the cells will no longer be able to divide due to things like methylation and telomeres etc.