Wednesday, September 12, 2012

What genes are upregulated during distraction osteogenesis?

Knowledge of what genes are expressed during distraction osteogenesis may provide insight of what genes to induce without causing fracture.  It also allows us to compare DO to LSJL.

Expression of TGF-beta1, osteonectin, and BMP-4 in mandibular distraction osteogenesis with compression stimulation: reverse transcriptase-polymerase chain reaction study and biomechanical test.

"A total of 42 rabbits were used in this reverse transcriptase-polymerase chain reaction study. In the control group, distraction was performed at 1 mm/day for 8 days. In the experimental group, overdistraction was performed for 10 days, followed by a 3-day latency period and 2 days of compression to achieve the same amount of DO. Three rabbits per subgroup were killed at 0, 5, 13, 20, 27, 34, and 41 days after the initial osteotomy. The levels of TGF-beta1 {TGF-Beta receptor I was downregulated by LSJL but TGF-BetaRII is the better one for height growth}, osteonectin, and BMP-4 in the bone regenerates were measured.
Reverse transcriptase-polymerase chain reaction revealed a greater level of TGF-beta1 in the experimental group immediately after applying the compression force that continued for 2 weeks. The level then decreased to that of the control group at 3 weeks. The greater level of osteonectin in the experimental group after compression than that in the control group continued for 3 weeks. In the experimental group, the level of BMP-4 increased immediately after compression. However, the level in the control group decreased."

"overexpression of TGF-β1 on mesenchymal cells, osteoblasts, neovessels, and collagen in the extracellular matrix near the osteotomy site"

"the level of TGF-β1 expression increased during the latency and distraction periods and decreased 4 weeks after DO"

"positive staining for platelet-derived growth factor, basic fibroblast growth factor, TGF-β, BMP-2, BMP-4, and BMP-7 in the cells and matrix components [occurred 21 days after DO]"

Comparison of gene expression of tissue inhibitor of matrix metalloproteinase-1 between continuous and intermittent distraction osteogenesis: A quantitative study on rabbits.

"[There were] higher mRNA levels of TIMP-1 under continuous distraction than that under intermittent distraction at day-6 and day-10 {upregulated over 6 fold by LSJL}. No significant differences were found at day-14 and day-21."

Expression of osteotropic growth factors and growth hormone receptor in a canine distraction osteogenesis model.

"The aim of the present study was to determine the expression of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), and bone morphogenetic protein 2 (BMP-2) in distraction-induced bone regeneration. Expression of these factors was assessed during the consolidation phase, comparing distraction osteogenesis with osteotomy-induced bone formation.In addition, plasma GH profiles and plasma concentrations of IGF-I, IGF-II, and insulin-like growth factor-binding protein 4 and -6 (IGFBP-4 and -6) were measured to assess their potential systemic role during bone formation. Expression of GHR, IGF-I, and BMP-2 had significantly increased in comparison with the expression of these factors in mature bone. Expression of GHR was significantly higher in distraction-induced bone regenerate than in osteotomy-induced bone {The difference was 78-fold}. No significant differences were found for the expression of IGF-I and BMP-2 between distraction and osteotomy {thus the osteomy may be most important in initiating height growth and not the distraction}. Plasma concentrations of GH, IGF-I, IGF-II, IGFBP-4, and IGFBP-6 did not demonstrate any significant differences between treatment groups and controls. Upregulation of GHR expression in distraction osteogenesis may enhance sensitivity to endogenous systemic GH and thus promote consolidation of the regenerated bone. Changes in the systemic osteotropic growth factors GH{downregulated by LSJL}, IGF-I, IGF-II, IGFBP-4, and IGFBP-6{upregulated by LSJL} do not seem to be of importance during distraction osteogenesis."

"IGFBP-6 preferentially binds and modulates IGF-II"

"The decrease in IGFBP-6 plasma concentrations possibly mediated through TGF-β1 could enhance local availability of IGF-II and thus stimulate bone formation"<-an IGFBP-6 inhibitor may be a way to grow taller?

The role of angiogenesis in a murine tibial model of distraction osteogenesis.

"A simple and reproducible murine model of tibia distraction osteogenesis was developed using a monolateral fixator. Bone formation was assessed histologically over a 35-day time course. The steady state expression of a broad family of angiogenesis-associated genes was assessed by microarray hybridization analyses over the same time course, while the immediate gene response that was induced during each cycle of distraction was assessed at 30 min and 8 h after the first and last rounds of activation of the fixator. Distraction osteogenesis promoted new bone formation primarily through an intramembranous process with maximal osteogenesis during the active distraction period. Histological analysis also showed that dense cortical bone continued to be formed, during the consolidation phase, for 2 weeks after distraction ended. The analysis of steady state mRNA expression levels over the time course of DO showed that VEGF-A and neuropilin, an alternate receptor for VEGF-A, both angiopoietin (Ang) 1 and 2 factors, and the Ang receptor Tie2 were the critical angiogenic factors during DO. A key transcriptional regulator of many of the angiogenic factors, hypoxia-induced factor1alpha (Hif-1a), the FGF binding protein pleiotropin/OSF1{upregulated by LSJL as PTN}, and multiple MMP(s), were also induced during the active distraction period. Examination of the expression of angiogenic factors that were induced after each cycle of activation, demonstrated that Hif-1a, Nrp1, and VEGF-A were all cyclically induced after each increment of distraction. "

"two growth factors pleiotropin/OSF2 and pigment epithelium-derived factor (PEDF) showed the greatest absolute levels of expression during the bone regeneration"

"our results did show chondrocyte-like cells both at the border of trabecular bone adjacent to osteoblast-like cells. While these cells had the appearance of hypertrophic chondrocytes, contrary to fracture healing a distinct endochondral phase was not seen"

"Ang-2 in the presence of VEGF will promote new vessel formation by both inducing remodeling of capillary basal lamina and stimulating endothelial cell sprouting and migration"

Stimulation of Fos- and Jun-related genes during distraction osteogenesis.

" We looked for the expression of early-response genes of the AP-1 transcription factor complex in an in vivo bone regeneration system subjected to mechanical forces because these genes were found to be related to mechanotransduction and important for bone development. Sheep maxillary bone was distracted daily for 15 days. c-Jun and c-Fos were evaluated in biopsy specimens removed at 8 and 15 days and were compared with post-osteotomy but not distracted repair tissue. Elevated levels of c-Jun and c-Fos mRNA were found after 8 days of distraction. Likewise, mesenchyme-like and fibroblast-like cells composing the 8-day distracted regeneration tissue showed increases in the intensity of immunostaining compared to cells in the corresponding non-distracted fracture repair tissue. After 15 days of distraction, when bone trabeculae start to form distally and proximally in the distracted regeneration tissue, mostly preosteoblasts and osteoblasts retained c-Fos and c-Jun immunoreactivity, similar to bone-associated cells in control non-distracted fracture repair tissue."

Jun and Fos genes are upregulated by LSJL.

"The nuclear protooncogenes c-fos, c-jun, fra-2, and jun-D, the expression of which has been followed in the present study, are members of a family of transcription factors that contain a leucine-rich region and a basic region, which are necessary for dimer formation and DNA binding, respectively. Dimerization is a prerequisite for DNA binding to a consensus response element site (5′-TGAG/CTCA-3′) designated activator protein-1 (AP-1) "

It seems that the way distraction osteogenesis initiates height growth is via BMP-2,4, and 7 and TGF-Beta1 and angiogenesis related proteins.  Why can't we just initiate those proteins without the bone breaking?


  1. Limb lengthening honestly sounds a lot more viable than LSJL because it actually works while LSJL probably doesn't

  2. @ anonymous u mean limb lengthening surgery? yea of course it surgery does work but lot expensive and S/E are i decided to do only LSJL
    may be in this decade or soon there will be better way to improve height as gene regulation by vectors(viruses) and some other technology..
    the way i was wondering is to introduce some chondroblast and osteoblasts combination at growth plates that may help ...:)