Update on Vosoritide:  New studies have come in about it that show very promising results and I am like 99% confident that it would work on children that do not have dwarfism because they also are impacted by CNP and have FGFR3 receptors.   Vosoritide is very promising and I think will eventually be used for children of normal growth velocity.

Vosoritide is basically a daily CNP injection.  It’s targeted for dwarfism but as everyone has FGFR3 receptors it can work normal children but testing would be needed.

<-From the video it seems that it’s progressing very slowly.  Which is unfortunate as it has potential to happen normal children and possibly even adults.  Unfortunately it doesn’t seem like they’r keen on testing Growth Hormone and CNP at the same time because Growth Hormone may only increase growth velocity but not final height but perhaps together.  They address other potential uses kindof at around the 25 minute mark.

Here’s more on CNP.<-“we developed transgenic mice with an elevated plasma concentration of CNP under the control of human serum amyloid P component promoter and exhibited that these mice showed prominent skeletal overgrowth phenotype”

CNP delays mineralization.->”The femur, skull, and spine (L2-4) measurements were longer than that of the wild-type littermates”  It could potentially affect adults via spinal height even if limbs do not increase.

“CNP activates bone turnover and remodeling in vivo”

More on CNP.<-also there’s a snippet from free patents online for CNP being used to increase height in people free of FGFR3 abnormalities meaning normal children.

Who knows if CNP could potentially increase height in adults until it is tested….

Apparently Biomarin did test this on adults but did the adults get taller?  Although the study was only for a short period of time approx two weeks which is not a lot of time to evaluate if the adults grew taller.

Note Meclozine has been associated with height growth too.

Note based on this image, barring other effects the benefit of CNP is limited based on how much growth inhibiting effects FGFR3 induces.  Though according to Dose dependent effect of C-type natriuretic peptide signaling in glycosaminoglycan synthesis during TGF-β1 induced chondrogenic differentiation of mesenchymal stem cells., CNP may induce differentiation of MSCs to chondrogenic lineage so it’s effects may not solely be limited based on how much FGFR3 there is to inhibit.

“A multinational study of 35 children (5–14 years of age) receiving daily subcutaneous vosoritide at a dose of 15 µg/kg demonstrated a sustained increase in the annualized growth velocity of approximately 1.5–2.0 cm/year over 42 months of treatment.” Let’s say that’s 1.5 inches over 3 years.  That’s pretty significant.  How long that can be sustained will be revealed with further testing.

Here’s another study on Vosorotide:

Once-daily, subcutaneous vosoritide therapy in children with achondroplasia: a randomised, double-blind, phase 3, placebo-controlled, multicentre trial

Now growth velocity does not always coincide with final height.

“Due to the inherent variability of growth and the lesser magnitude of the pubertal growth spurt in children with achondroplaisa, these long-term effects will only be known once these children reach final adult height”

You can see in the circled image a student using a hammer and chisel on an object.  I’m currently trying the hammer method with a ball pein hammer.  Unlike suggested in the post I am currently tapping the epiphysis of the bone and not just the diaphysis and I am not using a chisel because I think it is too cumbersome.  Now it’s possible that the hammer here is being used to cause a fracture rather than as a bone stimulatory agent, I’m just suggesting that using a lateral impact force is not unheard of.  Also, the method alluded to in the poster would have the issue that the hammer would puncture the skin(hence why I’m trying a ball pein hammer).

Also of note in the poster(and circled) Is that salubrinal and joint loading is used on articular cartilage and it seems to be noticeably thicker than even the control group.  Also if you look at the rat foot on the same line.  the salubrinal(and joint loaded) treated group looks longer than the osteoarthritis group but that could be an optical illusion.

Here are David Burr’s thoughts on the study.  I have spoken to David Burr before as he’s add that microdamage in bone does not heal by endochondral ossification.  He’s said:  “Diffuse damage(and linear microcracks that are are not fully fractures) don’t heal by endochondral ossification.”  “Large cracks always heal by remodeling, but full fractures, trabecular or otherwise, can heal by endochondral ossification.”  I pointed out this study to him given that he’s made the above statements.  Here’s what he had to say: “The endochondral ossification and chondrocytes that are present here are in woven bone.  That is not unusual.  There is none of that in the pre-existing bone.  Several things here are remarkable (though not that cartilage can appear in woven bone).  One question is why is there woven bone when the strains are only 640 microstrain (not high, as suggested by the authors).  This suggests there was some independent effect of muscle stimulation on bone, beyond the level of strain.  This could be due to the manner of stimulation, or to the fact that these were quite young rats – not adult – started at 8 weeks, or that the muscle stimulation occurred consistently over a long period of time. At some point in the very distant past, we showed that high strains (which were not present here) in dogs can cause woven bone formation without fracture.  It is simply a response either to a need to adapt quickly, or to damage that is not evidenced in a fracture.  So, I don’t find anything particularly novel about this, and some fundamental flaws in the model and analysis.”<-I think Burr is arguing that endochondral ossification is only occurring in immature bone that is not under repair.

I suggested that the independent effect of muscle stimulation could be fluid flow.  Here’s what he had to say: “Strain is still too low – but it depends on the strain rate (ie, strain x frequency).  But, if the frequency is too high, then fluid can’t relax and so the effect is blunted”

I talked to Dan Huey in the past about the possibility of endochondral ossification within the bone.

“”While MSCs derived from bone marrow have shown the ability to differentiate down the chondrocytic lineage both in vitro and in vivo the efficiency and completeness of this process hinders the formation of stable hyaline tissue. Ectopic differentiation of MSCs into chondrocytes does not occur in the marrow cavity due to a lack of the appropriate signals (both mechanical and biochemical). These MSCs are tuned by their environment to contribute to the natural bone remodeling process. However, even when these cells are introduced into a cartilage defect via microfracture, complete chondrocyte differentiation does not occur, as evidenced by the formation of fibrous tissue. For these cell to undergo complete chondrogenesis the proper combination of mechanical and biochemical cues must be provided. As the clot formed in microfracture is quite soft the cells within the clot will not receive the appropriate level of mechanical forces for chondrogenesis. With regards to the biochemical signals, a cartilage stimulating growth factor analagous to BMP’s effect for osteogenic differenetiation has not been identified. With respect to the term microfracture, in cartilage and bone it means two different things. For cartilage microfracture is a surgical procedure that involves creating holes in the bone underlying a cartilage defect to allow stem cells to enact a healing response. With regards to bone, microfractures are the very small breaks in bone that occur during strenuous activity.  does not occur in cartilage as it does in bone. In bone, microfracture occurs during strenuous activity and heals.”<-it’s possible that muscular contraction along with other mechanical stimuli could help induce the signals needed for chondrogenic differentiation.

The below study shows the presence of endochondral ossification in non-growth plate regions within bone itself.  The problem is that at least according to this stimulus it is not in a longitudinal direction.  But this is a huge breakthrough study as it shows that chondrogenic regions can occur outside of the growth albeit in developing rats.

Morphological and histological adaptation of muscle and bone to loading induced by repetitive activation of muscle

“Muscular contraction plays a pivotal role in the mechanical environment of bone, but controlled muscular contractions are rarely used to study the response of bone to mechanical stimuli. Here, we use implantable stimulators to elicit programmed contractions of the rat tibialis anterior (TA) muscle. Miniature stimulators were implanted in Wistar rats (n = 9) to induce contraction of the left TA every 30 s for 28 days. The right limb was used as a contralateral control. Hindlimbs were imaged using microCT. Image data were used for bone measurements, and to construct a finite-element (FE) model simulation of TA forces propagating through the bone. This simulation was used to target subsequent bone histology and measurement of micromechanical properties to areas of high strain. FE mapping of simulated strains revealed peak values in the anterodistal region of the tibia (640 µε ± 30.4 µε). This region showed significant increases in cross-sectional area (28.61%, p < 0.05) and bone volume (30.29%, p < 0.05) in the stimulated limb. Histology revealed a large region of new bone, containing clusters of chondrocytes, indicative of endochondral ossification. The new bone region had a lower elastic modulus (8.8 ± 2.2 GPa) when compared with established bone (20 ± 1.4 GPa). Our study provides compelling new evidence of the interplay between muscle and bone.”

“eight-week-old Wistar rats (weights 228–282 g) underwent surgical implantation of miniature neuromuscular stimulators”

“Stimulators delivered 0.2 ms pulses at 100 Hz for 200 ms every 30 s, resulting in a total of 9.6 min of stimulation per day. Each 200 ms burst of nerve stimulation at 100 Hz caused a very brief but fused (tetanic, near maximum force) contraction.”<-it would be very hard to induce a maximum force contraction.  But muscle stimulation increase fluid forces in bone.  So it is not only possible for muscle contraction to stimulate new endochondral ossification within bone but any method that stimulates fluid forces.

“The volume of the stimulated muscles, TA and EDL, showed a significant decrease of volume of, on average, 19% and 16% (p < 0.05), respectively, when compared with the contralateral control limb”<-It’s interesting that the muscle actually decreased in size.

“Histological sectioning targeted to this distal region revealed that the cross-sectional geometry of the contralateral control and the stimulated tibias were markedly different (figure 8a). The stimulated bone shows a large region of primary osteon formation (figure 9). Safranin O staining revealed the presence of clusters of chondrocytes within the region of primary osteon formation!!!!!! (figure 10).”

Here’s the grant Cartilage progenitor cells for growth plate regeneration

“Growth plate (GP) injuries result in growth arrest, formation of a “bony bar”{a technique that gets rid of the bony bar could potentially be used to make a new growth plate in adults} and angular limb deformities in children. Novel therapeutic approaches directed towards prevention of bone formation and growth arrest have to integrate cellular grafts, biomaterials and growth factors with the ultimate goal of recapitulating the complex zonal organization of the growth plate. One endogenous source of cartilage progenitor cells is thought to be the resting zone of the growth plate. Until now, the lack of specific marker(s) for the resting zone restricted the examination of this population. Currently, the evaluation of potential strategies for growth and cartilage disorders can mainly be achieved in vivo, therefore we proposed to use genetic modified mice to characterize the GP population and to characterize its development. Mice are the most appropriate model to use for several reasons: 1) GP is a tissue hardly approachable in vitro 2) we aim to characterize the GP population, and GP dynamics during the process of growing for which there is no optimal in vitro assays 3) we chose PHEX hemizygous mice for the study of GP dynamics because it is a well stablished model of X-linked hypophosphatemia (XLH){also called vitamin D resistant rickets}, which has being used for decades to study growth plate ossification. An other thing to keep in mind is that the standard treatments for XLH patients do not completely rescue the rickets and bone deformities. Serious side effects such as nephrocalcinosis and hyperparathyroidism have also been observed. Antagonizing FGF23 activity with antibodyes (Burosumab treatment){here’s some papers that indicate that FGF23 inhibition may potentially be part of a growth plate reactivation treatment.  FGF23 impacts bone mineralization so that may be why FGF23 inhibition could potentially help with growth plate restoration } is a recent and very promising therapy. However, this treatment requires at least a monthly infusion, is very costly and alleviates symptoms in many patients but not all. Hence, it is of the utmost necessity to identify more affordable strategies for therapy. Dr. Santos’ Laboratory demonstrated that inhibiting the MAPK pathway (FGF23 downstream pathway) in PHEX mice partially rescues growth impairment by normalizing the GP structure, specifically in the hypertropy zone. Nevertheless, it is not completely understood how FGF23 inhibition affects GP dynamics or how this is translated into a growth rescue and whether this treatment would be suitable for paediatric patients. Consequently, we will utilize the PHEX mice and FGF23 to 1) gain a better understanding of GP development and 2) look for alternative therapies to antagonize FGF23 activity.”

“FoxA2+ cells exhibit high clonogenicity and longevity. Moreover, FoxA2+ cell number expand in response to trauma and the data suggest that these cells participate in the production of hyaline cartilage, allowing for successful cartilage regeneration”

“Unlike other cartilage regions such as articular cartilage, GP has the ability to regenerate.”

Since Wild Type was the longest we don’t know it this treatment would have any impact in healthy developing individuals.

Endochondral ossification is not the only mechanism by which one can grow taller but also by appositional growth on the longitudinal ends whether by articular cartilage endochondral ossification or by direct bone deposition.  This study indicates that dinosaurs may have grown via non-endochondral ossification dependent mechanisms.  {Edit:  I emailed BM Rothschield and he said that all longitudinal bone growth identified occurred via longitudinal means but I think there’s a lot of interesting stuff here like that vascularization is key for growth plates.

An apparently phylogeny-independent method for identification of skeletal (longitudinal) growth cessation (skeletal maturity) in birds

“Identification of skeletal maturity is of interest as a measure of species longevity and for identifying its maximal achievable size/mass. Measurement of age on the basis of growth arrest/accentuation lines and external fundamental system evidences cessation or at least extreme slowing of circumferential bone growth{circumferential is appositional/periosteal growth which is mainly bone width but could potentially increase bone length albeit very slowly}. Such intramembranous (periosteal)-derived growth is distinct from the endochondral ossification responsible for longitudinal growth and therefore achievable organismal size/mass. As subchondral transcortical channels are required for nourishment, their loss should identify cessation of longitudinal growth{if we can restore subchondral transcortical channels then maybe we can restore longitudinal bone growth}. Predicated on phylogenetic bracketing/relationship and shared anatomical structures with and without growth plates, birds represent an appropriate model for the study of dinosaur ontogeny. Persistence of transcortical subchondral channels in the long bones of birds are examined at ×100–200 magnification and correlated with bone length. Transcortical channels are present in subchondral articular surfaces, but disappear when terminal longitudinal growth is achieved. Articular vascular channels perforating articular surfaces from within the bone are detected. Loss of penetrating channels is interpreted as evidence of skeletal growth cessation, identifying the longitudinal bone length at which skeletal growth cessation has been achieved. The current study provides evidence that maximal bone length does correlate with endochondral cessation growth. Failure of circumferential growth reduction/cessation to correlate with bone length may be related to lack of synchronicity of periosteal-based circumferential growth with the endochondral process responsible for bone lengthening{so the author states that circumferential growth can contribute bone length potential but it does not happen in practice}. Loss/closure of articular vascular channels may be the most reliable measure of a bird’s achievement of maximal growth (indicating cessation of appendicular element lengthening).”

“As trans-cortical channels through subchondral (that just below the articular cartilage) bone are the major source of nutrients for continued longitudinal growth, it is hypothesized that atrophy or loss of those articular vascular channels would preclude continued growth of bone – at least longitudinally.”<-this may be why mechanical loading could contribute to longitudinal bone growth by making this delivery more efficient by driving nutrients and potentially stimulating the channels to be open for longer

“Even calcified cartilage (which persists in the long bones of some groups) retains trans-surface (articular) channels (Rothschild and Tanke, 2007) and represents the opportunity for continuing growth“<-BM Rothschild the author of this study has also studied dinosaur bones

” epiphyseal bone expands “into the cartilage anlage until the interface forms a calcific layer that arrests vascular invasion.” That shuts off the marrow, and the vascular supply thereby available, from the epiphyseal cartilage”<-if we can degrade that layer then we can restore longitudinal bone growth

““proximal end of humerus grows faster than distal, “because the internal pattern of spongiosum depends on the direction of bone pressure.””<-thus again that bone pressure can affect bone growth.

“Trans-articular surface canals (articular vascular channels perforating articular surfaces from within the bone marrow) are detected, independent of avian order or family, confirming loss of the blood supply necessary for longitudinal growth.”<-so we if can keep the blood supply than we can keep growing for longer.  Note distraction osteogenesis basically restores the blood supply via fracture

” “canal-like contacts between the articular cartilages and the medullary cavities of epiphyses” supports the interpretation that continued growth is dependent upon persistence of such channels. While the loss of articular vascular channels does not identify an individual’s actual age, it does allow identification of the longitudinal bone length at which skeletal growth cessation has been achieved.”

“a linear relationship between LAG/EFS{growth arrest lines} and bone length is not established in dinosaurs. However, there is a confounding issue: Circumferential growth is the result of intramembraneous (periosteal) bone formation, while bone lengthening is the product of a very different process, endochondral bone formation”<-meaning dinosaurs were likely able to grow via mechanisms other than longitudinal bone growth.

” Longitudinal histologic section of bones provides evidence that growth had ceased, at least by documenting loss of trans-cortical channels. It is unclear that such a histological approach would provide significant additional information (on longitudinal growth cessation) to that observed by microscopic examination of joint surfaces. At this time, loss/closure of articular vascular channels may be the most reliable measure of a bird’s achievement of maximal growth (indicating cessation of appendicular element lengthening)”

Here’s more on dinosaurs also by BM Rothschild

Identification of growth cessation in dinosaurs based on microscopy of long bone articular surfaces: preliminary results

“As applied to bone, ‘determinate growth’ identifies an upper limit to size and the point when normal endochondral ossification ceases. This contrasts with ‘indeterminate growth’, which proceeds through the entire life of the animal. In this study, a non-destructive method, epi-illumination surface microscopy of the articular surfaces of long bones, is applied for the first time in 40 taxa of non-avian dinosaurs to determine cessation of endochondral growth. Thereby, the presence or absence of articular vascular channels between the endochondral bone and the cartilage is assessed. As articular vascular channels are the major source of nutrients for continued longitudinal growth, atrophy or loss of those channels would preclude continued growth of bone. We correlated our findings with published histological data and bone length measurements. We found articular vascular channels in all assessed dinosaur groups, but some individuals showed a loss of detectable articular vascular channels – what we interpret as evidence of longitudinal skeletal growth cessation. This observation contrasts with the hypothesis of continuous indeterminate growth in dinosaurs, at least for the taxa identified here, in which channels have been documented as closed or closing over{so dinosaurs must have grown via mechanisms other than endochondral ossification}. The new method introduced here provides a phylogenetic tool for definitively distinguishing new ‘dwarf’ species from juveniles of known species. Furthermore, this study confirms the rarity of skeletally mature dinosaurs discovered to date and indicates that we have only begun to witness the full extent of dinosaur growth.”

“Growth measured by LAGs and by EFS is intramembranous in derivation. It is a very different process from the endochondral ossification (in which bone replaces cartilage), which characterizes longitudinal bone growth”

“trans-cortical channels through subchondral (i.e., just below the articular cartilage) bone are the major source of nutrients for continued longitudinal growth, it is hypothesized that atrophy or loss of those articular vascular channels would preclude continued growth of bone—at least longitudinally. Even calcified cartilage (which persists in the long bones of some dinosaur groups) retains trans-surface (articular) channels and represents the opportunity for continuing growth{!}.”

“epiphyseal bone expands ‘into the cartilage anlage until the interface forms a calcific layer that arrests vascular invasion’. This shuts off the marrow, and the vascular supply thereby available, from the epiphyseal cartilage”

” in [some] taxa (e.g., Plateosaurus) the bone length is not correlated with ontogeny as measured by slowing/cessation of intramembraneously based circumferential growth”

“failure to identify growth cessation in Tyrannosaurus rex.”

Here’s a study that shows that growth plate loading can stunt growth but it also shows that it can enhance growth in one vertebrae which emphasizes the importance of developing the proper loading method.

In vivo dynamic loading reduces bone growth without histomorphometric changes of the growth plate

“This in vivo study aimed at investigating the effects of dynamic compression on the growth plate. Rats (28 days old) were divided into three dynamically loaded groups, compared with two groups (control, sham). A device was implanted on the 6th and 8th caudal vertebrae for 15 days{but note not on the 9th vertebrae which grows as we’ll see later}. Controls (n = 4) did not undergo surgery. Shams (n = 4) were operated but not loaded. Dynamic groups had sinusoidal compression with a mean value of 0.2 MPa: 1.0 Hz and ±0.06 MPa (group a, n = 4); 0.1 Hz and ±0.2 MPa (group b, n = 4); 1.0 Hz and ±0.14 MPa (group c, n = 3). Growth rates (µm/day) of dynamic groups (a) and (b) were lower than shams (p < 0.01). Growth plate heights, hypertrophic cell heights and proliferative cell counts per column did not change in dynamic (a) and (b) groups compared with shams (p > 0.01). Rats from dynamic group (c) had repeated inflammations damaging tissues{this group had the highest frequency of loading}; consequently, their analysis was unachievable. Increasing magnitude or frequency leads to growth reduction without histomorphometric changes. However, the combined augmentation of magnitude and frequency alter drastically growth plate integrity. Appropriate loading parameters could be leveraged for developing novel growth modulation implants to treat skeletal deformities{the authors themselves even allude to with this sentence that this does not disprove growth modulation but that it only suggests that it’s important to develop the appropriate growth modulation method}.”

“With the approval of the Institutional Animal Care Committee, 19 male Sprague–Dawley rats were received at the age of 21 days old. After 1-week of acclimatization, the protocol was conducted from 28 to 43 days old, corresponding to the rat pubertal growth spurt”

“The stress variation was chosen at a mean value of 0.2 MPa as it represents a wide physiological stress interval that is still retarding but not arresting bone growth (stress value over 0.6 MPa). The frequencies were either lower (0.1 Hz) or close to an average walking frequency (1.0 Hz) for humans. ”

“The loading device was adjusted daily at the same time of day for 10 min under isoflurane to compensate for longitudinal growth.”

“three caudal vertebrae (one loaded Cd7; two unloaded (Cd5, Cd9) used as intra-animal controls)”

Note how the CD9 vertebrae grew significantly faster than controls.  Also interestingly the sham group for both CD7 and CD9 vertebrae grew faster than controls.  “Shams (n = 4) were operated but no compression was applied.” <-so the operation itself could be stimulatory on the growth

“The ultimate dynamic (c) condition, combining an increase in both maximum magnitude and frequency, was tested only on three animals since severe inflammation occurred.”

CD9 has a significant increase in all growth plate parameters according to these figures.

Clearly the loading regime on CD7 had spillover reduction in growth in CD5 and stimulatory effect on growth in CD9.  It’s hard to say why that is without looking at say a stress strain analysis.  The device could be doing indirect tensile strain on CD9 and compressive strain on CD5.   But this study shows the importance of finding the right loading method in order to manipulate longitudinal bone growth.