Tag Archives: distraction osteogenesis

Using CRISPR technology to upregulate Chondromodulin could be a possibility in the future

The implication of this study I think is that CRISPR or other gene therapy technology could potentially be used to elevate Chondromodulin levels to either quicken limb lengthening surgery or maybe induce ectopic cartilage formation?

Chondromodulin is necessary for cartilage callus distraction in mice

“Chondromodulin (Cnmd) is a glycoprotein known to stimulate chondrocyte growth. We examined in this study the expression and functional role of Cnmd during distraction osteogenesis that is modulated by mechanical forces. The right tibiae of the mice were separated by osteotomy and subjected to slow progressive distraction using an external fixator. In situ hybridization and immunohistochemical analyses of the lengthened segment revealed that Cnmd mRNA and its protein in wild-type mice were localized in the cartilage callus, which was initially generated in the lag phase and was lengthened gradually during the distraction phase. In Cnmd null (Cnmd−/−) mice, less cartilage callus was observed, and the distraction gap was filled by fibrous tissues. Additionally, radiological and histological investigations demonstrated delayed bone consolidation and remodeling of the lengthened segment in Cnmd−/− mice. Eventually, Cnmd deficiency caused a one-week delay in the peak expression of VEGF, MMP2, and MMP9 genes and the subsequent angiogenesis and osteoclastogenesis. We conclude that Cnmd is necessary for cartilage callus distraction.“

So CNMD gene therapy could potentially be used to treat non-unions in limb lengthening surgery too.

“Cnmd−/− mice did not show abnormalities in cartilage development or endochondral bone formation during embryogenesis or normal growth, and further did not affect natural articular cartilage development. Thus, Cnmd functions as a chondrocyte modulator in specific conditions, causing osteogenesis such as cartilage or bone injury, but not in normal cartilage development and growth.”

“the relationship between mechanical stress and Cnmd in the process of cartilage callus formation during bone repair/regeneration.”<-Perhaps we could induce Cnmd via other mechanical stress mechanisms?

“We focused on distraction osteogenesis, which involves an osteotomy followed by a slow progressive distraction to lengthen congenitally or traumatically shortened extremities”

“Cnmd could directly stimulate chondrocyte proliferation and proteoglycan synthesis in vitro“

“Cnmd is required for cartilage callus formation due to tensile stress on the periosteum and is less involved in it due to hydrostatic pressure between the gaps”<-we can induce hydrostatic pressure and tensile stress via other mechanisms.

” the gap tissue is subject to approximately 15% deformation (compression and tension) during walking in a rabbit tibial lengthening model, indicating that compression as well as tensile forces act on the gap tissue during the distraction phase”

” the fibula spontaneously fractured during the distraction phase and lengthened in the same manner as the tibia.”

“increased expression of Tnmd mRNA in Cnmd−/− mice at the distraction phase. Tnmd is a type II transmembrane protein that shares a cysteine-rich domain with Cnmd at the C-terminus”<-we actually want Tnmd to increase as Tendons are one of the limiting factors in the amount of growth you can get in limb lengthening surgery.

“Tnmd mRNA expression was strongly upregulated by 5% axial cyclic strain in tendon stem/progenitor cells”

“elongation of cartilage callus during distraction osteogenesis was suppressed in Cnmd−/− mice and subsequent bone formation and remodeling slowed and partially failed. The study results indicate that Cnmd-mediated cartilage callus elongation is necessary for distraction osteogenesis and Cnmd could be a mechanical response chondrogenic factor. New insights into the function of Cnmd may establish this molecule as a candidate therapeutic agent for successful bone healing.”

Distraction Histogenesis: Arteries

In limb lengthening surgery, there is concern to how the soft tissue will adapt to the growing bone. Here is a paper that provides evidence that the arteries do adapt after limb lengthening surgery:

Effect of mechanical tension stress on arterial vessels after limb osteotomy in rabbits

<-osteomy is bone cutting an important stage in limb lengthening surgery

“Limb lengthening by tensile stress{limb lengthening surgery is primarily an osteomy plus tensile stress} has become an effective measure in the treatment of fracture and limb amputation, but the underlying mechanism of how mechanical tensile stress affects limb arteries and vessels has not been clarified.  
To investigate the effect of slow steady unidirectional mechanical tension stress on limb artery.
 Totally 75 adult New Zealand rabbits were randomly divided into model control group (the hind limb was amputated and not prolonged), experimental group (the hind limb was amputated and lengthened) and blank group (no limb treatment), with 25 rabbits in each group. The prolonged speed of the experimental group was 0.5 mm/time, twice a day, for 10 days. Saphenous artery specimens were collected at 8, 10, 12, 16, and 19 days (i.e., 3, 5, 7, 11, and 14 days from the start of distraction osteogenesis) after Ilizarov external fixation. The length of saphenous artery was observed and compared. At the same time, X-ray examination was conducted to detect the osteotomy of the affected limb. Arterial structure and inflammatory response were observed by hematoxylin-eosin staining.  
(1) In terms of vascular length: Since the 5th day of Ilizarov external fixation stent pulling, the length of saphenous artery in the experimental group was significantly increased compared with the model control group (P < 0.01). (2) In terms of X-ray examination, at 16 days after osteotomy (i.e., 1 day after the extension ends), the end of osteotomy in the experimental group was extended by about 10 mm, and no callus was formed in the gap. (3) Hematoxylin-eosin staining showed that at 8, 10, 12, 16, and 19 days after external fixation, the arterial tissue structure of the experimental group was intact, without intima vascular injury, smooth muscle cell necrosis or inflammatory cell infiltration. (4) These results indicate that slow and steady unidirectional mechanical stretch stress can prolong the limb arteries and keep the arterial vascular structure stable while lengthening the length of tibial osteotomy end, suggesting that the potential mechanism of stretch stress promoting limb lengthening lies in the stimulation of arterial vascular growth.“

Unfortunately, I could not get this full study.