Me: I found this article when I was searching for more information on bone lengthening. It seems that the engineering students in this generation are trying their hands and finding better ways to do limb lengthening. What makes this so interesting is that the device they have as a prototype is a combination of the efforts of students in biomedical engineering and mechanical engineering. The device does the distraction of the bones by attaching to the  wires that goes through the bone in the external fixator method and slowly moves the wires apart from each other while still keeping the overall structure stable. The unique thing they have is the feedback mechanism which makes sure the device does not overdo a distraction.

From website GizMag HERE

Students create automated bone-lengthening device

By Randolph Jonsson        April 25, 2012

Whether it’s from injury, infection or malfunctioning genes, millions of children suffer from bone deformities at any given time. To help remedy the situation, doctors often resort to the painful practice of breaking the target bone and then repeatedly moving the ends apart as they attempt to grow together – a procedure known as distraction osteogenesis (DO), that has its share of risks and problems. Now, a team of undergrad students from Rice University (RU) in Texas has come up with a device they hope will make the lengthy process of bone-stretching both easier and safer for the young patients who have to endure it.

“The process of limb lengthening – essentially creating a localized mini-growth spurt – works well for bones, but is very hard on the soft tissues such as nerves and blood vessels,” Gogola said. “This team has done an outstanding job of designing a creative solution. Their device not only protects the soft tissues, it will ultimately speed up the entire process.”

With current DO rigs, long pins are embedded on both sides of the break in the bone to be lengthened. These are then attached to a bulky threaded frame outside of the appendage with a drive screw that must be regularly adjusted manually several times a day with a hex wrench. This pushes the pins further apart as the bone heals, but before it sets, allowing the gentle elongation of the bone over a period of several months. It’s a burdensome task for patient and caregiver alike.

“The problem with the current device is that there’s a lot of room for error,” RU team member Kahn said. “You can imagine that one might forget to turn it once, or turn it the wrong way, or turn it too much. And a lot of problems can arise in the soft tissue and the nerves surrounding the bone,” she added. “That’s the limiting factor of this process. But LinDi implements a motor to make the distraction process nearly continuous.”

In fact, the battery-powered LinDi self-adjusts about 1,000 times a day, which allows it to better approximate bone growth. The team’s innovative inclusion of a force-feedback sensor – a first for DO devices – monitors stress loads on surrounding tissues and shuts the system down if levels get too high, thus averting unnecessary trauma from the process.

Short-term animal testing with the help of Shriners hospital staff allowed the students to fine tune the device and confirmed that it works as planned – a nice feather in the bonnet of the soon-to-be grads and a welcome relief for the countless children and their parents who stand to benefit from this new technology in the years to come.

Me: One a related note one of the commenters made a point that there was alreday a company in the 90s which had already developed a very similar device that could automate the distraction / stretching of the bone process. However there was no feedback mechanism that told the Automator to stop when the bone is distracted too far. From the comments on the article above…

“”A friend of mine did this nearly 15 years ago while working for a company called Autogenisys they automated the Ilizarov apparatus. While they they didn’t have a feed back system you didn’t have to manually adjust it either.””

Douglas Renfro
25th April, 2012 @ 09:40 pm PDT

Autogenesis Website link HERE

From the website….

The Automator

Applications:

• Ring Frame Lengthening
• Bone Transport
• Unilateral Frame Lengthening
• Joint Contracture
• Angular Deformity Correction.

Biological Advantages:

Research indicates that frequent distractions in small increments can promote superior muscle tissue and reduce the forces required to accomplish distraction (thereby reducing pain experienced by the patient). The Automator performs precise micro-distractions every few minutes minutes rather than every six hours as is typical with manual systems. Hence, the lengthening process is more similar to the body’s natural (continuous) growth process. Additionally patients and their families report less anxiety.

BACKGROUND:

The Automator was designed to provide an improved automated alternative to manual distraction methods. The device:

1. Costs the same or less than most manual distracters sold by large medical equipment manufacturers,
2. Allows patients to enjoy the psychological and physical benefits of high rhythm (small increment) corrections,
3. Allows for precision, flexibility, and reliability unavailable with manual systems, and
4. Does not introduce installation or operational complexity to the procedure.

Automated lengthening should be the standard of care for limb lengthening and deformity correction procedures.

Product Description:

• Continuous Distraction: The Automator  causes 1/240 mm adjustments 24 hrs per day according to the rate selected. Accuracy is maintained within 1/48 mm.
• Compact: The self contained design involves no external cables, batteries, or programming module. Each Automator weighs approximately 6oz.
• Programmable: Rate settings include 0.5, 0.75, 1.0, 1.25, 1.5, 2.0, and 4.0 mm/day. The device may be set for distraction, compression, or cyclical motion (used for loading a fracture site). Rate and directional settings may be changed by the physician at any time.
• Convenient: Brackets facilitate installation. The Automator is water resistant, and it requires minimal maintenance.
• Efficient: Automator batteries last more than four months when lengthening at 1mm per day. The device can distract against more than 250 lbs.
• Versatile: The device may be installed on ring or unilateral frames regardless of the distance between rings or frame components.

Source

Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.

Abstract

Cell condensation is a pivotal stage in skeletal development. Although prechondrogenic condensations normally exist for some 12 h, duration can vary. Variation is seen both between condensations for different cartilages (Meckel’s vs. elastic ear cartilage) and within a single condensation from which more than one skeletal element will form, as in the three components of the single first arch chondrogenic condensation. Understanding how duration of the condensation phase is established–how the condensation phase is entered and exited during cell differentiation–remains a major area for future study. During chondrogenesis, cell-specific products such as collagen types II and IX and cartilage proteoglycan appear concomitant with condensation. Therefore, during chondrogenesis, condensation precedes commitment of cells as prechondroblasts. During osteogenesis, however, differentiation of preosteoblasts precedes condensation. Therefore, during osteogenesis, condensation amplifies the number of committed osteogenic cells. Further comparative analysis of skeletogenesis should provide us with a more rigorous understanding of cell commitment, when differentiation is initiated, how commitment and differentiation are measured and the relationship of condensation to onset of differentiation. Current knowledge of molecules characteristic of condensations focused attention on extracellular matrix and cell surface components on the one hand, and on growth factors homeobox genes and transcription factors on the other. We have drawn together the molecular data for pre-chondrogenic condensations in diagrammatic form in Figure 2. Three major phases of chondrogenesis are identified: (a) epithelial-mesenchymal interactions that precede condensation, (b) condensation itself, and (c) cell differentiation. Although we label the third phase differentiation, it is important to recognize that phases a and b also constitute aspects of chondroblast cell differentiation (see Dunlop and Hall, 1995 for a discussion of this point. The pre-condensation phase is characterized by expression of Hox genes, growth factors (TGF-beta and BMP-2) and the cell surface proteoglycan receptor, syndecan-1. Expression of Msx-1 and Msx-2, growth factors and syndecan continues into the condensation phase. Other molecules, such as versican, syndecan-3 and tenascin, present in low concentrations before condensation, are up-regulated during condensation. Yet other molecules–Hox genes, transcription factors, growth factors (activin, BMP-4 and -5, GDF-5), cell adhesion molecules and proteoglycans–are only expressed during the condensation phase, while the transcription factor Pax-1, fibronectin, hyaluronan and hyaladherin are expressed both during and after condensation. During condensation mRNAs for collagen types II and IX and for the core protein of cartilage proteoglycan are up-regulated. Late in condensation and increasingly thereafter, the protein products of these genes accumulate as chondroblasts differentiate (see Fig. 2 for details). Not all the molecules present before, during of after condensation can be placed into causal sequences. Some however can. In Figure 3 we summarize the causal sequences discussed in this paper as they relate to initiation of condensation and to transit from condensation to overt differentiation during chondrogenesis. Condensations form following activation of at least three pathways: (1) Initiation of epithelial-mesenchymal interactions by tenascin, BMP-2, TGF beta-1 and Msx-1 and -2. (2) Up-regulation of N-CAM by activin. (3) Up-regulation of fibronectin by TGF-beta, further enhancing N-CAM accumulation (Fig. 3). It is by these three pathways that condensations are initiated and grow. Transition from condensation to overt cell differentiation is under both positive and negative control (Fig. 3). Syndecan blocks fibronectin and so blocks N-CAM accumulation, preventing accumulation of additional cell

PMID: 8901191     [PubMed – indexed for MEDLINE] 

Bioessays. 2000 Feb;22(2):138-47.

All for one and one for all: condensations and the initiation of skeletal development.

• Manuela Wuelling, Andrea Vortkamp

During endochondral ossification bones are formed as cartilage templates in which chondrocytes proliferate, differentiate into hypertrophic chondrocytes and are gradually replaced by bone. Postnatally, remnants of embryonic chondrocytes remain in a restricted domain between the ossified regions of the bones forming the growth plate. The coordinated proliferation and differentiation of chondrocytes ensures the continuous elongation of the epiphyseal growth plates. The sequential changes between proliferation and differentiation are tightly regulated by secreted growth factors, which activate chondrocyte-specific transcription factors. Transcription factors that play critical roles in regulating cell-type-specific gene expression include Sox9, Gli2/3, and Runx2. The interaction of these transcription factors with general transcriptional regulators like histone-modifying enzymes provides an additional level of regulation to fine-tune the expression of target genes in different chondrocyte populations. This review will outline recent advances in the analysis of the complex transcriptional network that regulates the distinct steps of chondrocyte differentiation.

Source

Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Japan.

Abstract

Leptin has been suggested to mediate a variety of actions, including bone development, via its ubiquitously expressed receptor (Ob-Rb). In this study, we investigated the role of leptin in endochondral ossification at the growth plate. The growth plates of wild-type and ob/ob mice were analyzed. Effects of leptin on chondrocyte gene expression, cell cycle, apoptosis and matrix mineralization were assessed using primary chondrocyte culture and the ATDC5 cell differentiation culture system. Immunohistochemistry and in situ hybridization showed that leptin was localized in prehypertrophic chondrocytes in normal mice and that Ob-Rb was localized in hypertrophic chondrocytes in normal and ob/ob mice. Growth plates of ob/ob mice were more fragile than those of wild-type mice in a mechanical test and were broken easily at the chondro-osseous junction. The growth plates of ob/ob mice showed disturbed columnar structure, decreased type X collagen expression, less organized collagen fibril arrangement, increased apoptosis and premature mineralization. Leptin administration in ob/ob mice led to an increase in femoral and humeral lengths and decrease in the proportional length of the calcified hypertrophic zone to the whole hypertrophic zone. In primary chondrocyte culture, the matrix mineralization in ob/ob chondrocytes was stronger than that of wild-type mice; this mineralization in both types of mice was abolished by the addition of exogenous leptin (10 ng/ml). During ATDC5 cell differentiation culture, exogenous leptin at a concentration of 1-10 ng/ml (equivalent to the normal serum concentration of leptin) altered type X collagen mRNA expression and suppressed apoptosis, cell growth and matrix calcification. In conclusion, we demonstrated that leptin modulates several events associated with terminal differentiation of chondrocytes. Our finding that the growth plates of ob/ob mice were fragile implies a disturbance in the differentiation/maturation process of growth plates due to depletion of leptin signaling in ob/ob mice. These findings suggest that peripheral leptin signaling plays an essential role in endochondral ossification at the growth plate.

Source

First Department of Oral and Maxillofacial Surgery, School of Dentistry, The University of Tokushima, Tokushima, Japan.

Abstract

Leptin, a 16-kD circulating hormone secreted mainly by white adipose tissue, is a product of the obese (ob) gene. Leptin acts on human marrow stromal cells to enhance differentiation into osteoblasts and inhibit differentiation into adipocytes. Leptin also inhibits bone formation through a hypothalamic relay. To obtain a better understanding of the potential role of leptin in bone formation, the localization of leptin in endochondral ossification was examined immunohistochemically. High expression of leptin was identified in hypertrophic chondrocytes in the vicinity of capillary blood vessels invading hypertrophic cartilage and in a number of osteoblasts of the primary spongiosa beneath the growth plate. The hypertrophic chondrocytes far from the blood vessels were negative for leptin. Moreover, we detected the production and secretion of leptin by a mouse osteoblast cell line (MC3T3-E1) and a mouse chondrocyte cell line (MCC-5) by RT-PCR, immunocytochemistry, and Western blotting. Leptin enhanced the proliferation, migration, tube formation, and matrix metalloproteinase-2 (MMP-2) activity of human endothelial cells (HUVECs) in vitro. These findings suggest the possibility that leptin exerts its influence on endochondral ossification by regulating angiogenesis.

PMID:   11799135         [PubMed – indexed for MEDLINE]

Leptin differentially regulates endochondral ossification in tibial and vertebral epiphyseal plates.

“Longitudinal bone growth is governed by a complex network of endocrine signals including leptin. In mouse, leptin deficiency leads to distinct phenotypes in bones of the limb and spine, suggesting the appendicular and axial skeletons are subject to differential regulation by leptin. We established primary cultures for the chondrocytes from tibial and vertebral epiphyseal plates. Cellular proliferation and apoptosis were analyzed for the chondrocytes that had been treated with various concentrations of leptin. Crucial factors for chondrocyte proliferation and differentiation, such as BMP7 and Wnt3, were measured in the cells treated with leptin alone or in combination with pharmacological inhibitors of STAT and ERK signaling pathways. Primary culture of tibial epiphyseal plate chondrocytes has greater proliferating capability compared with that of vertebral epiphyseal plate chondrocytes. Leptin could promote the proliferation of tibial epiphyseal plate chondrocytes, while its effect on vertebral epiphyseal plate chondrocytes was inhibitory. Consistently, apoptosis is inhibited in tibial but promoted in vertebral epiphyseal plate chondrocytes by leptin. Importantly, leptin differentially modulates chondrogenic signaling pathways in tibial and vertebral epiphyseal chondrocytes through STAT and ERK pathways. Leptin differentially regulates chondrogenic proliferation and differentiation in appendicular and axial regions of the skeletons. The signaling pathways in these two regions are also distinct and subject to differential regulation by leptin through the STAT pathway in tibial epiphyseal plate chondrocytes but through the ERK pathway in vertebral epiphyseal plate chondrocytes. Therefore, the regulation of leptin is multi-faceted in the distinct anatomical regions of the skeleton. Knowledge gained from this system will provide insights into the pathophysiological causes for the diseases related to bone development and metabolism.”

Abstract

Introduction

Several lines of evidence indicate that signaling triggered by CNP plays an important role in chondrocyte development [1], [2]. Upon CNP binding, its cognate receptor natriuretic peptide receptor 2 (NPR2) functions as a guanylyl cyclase to increase cyclic guanosine monophosphate (cGMP) levels in chondrocytes, female reproductive organs, and endothelial cells [3], [4]. Transgenic mice that overproduce CNP exhibit excessive growth, while defects of the CNP or Npr2 gene, leading to impairment of skeletal development [5]–[7]. The increase in cGMP level activates cGMP-dependent protein kinase II and seems to promote the accumulation of extracellular matrix in the growth plate of CNP-transgenic mice [8]. In human, overproduction of C-type natriuretic peptide (CNP) due to a chromosomal translocation was reported to cause skeletal dysplasia associated with tall stature [9]–[10]. In addition, acromesomelic dysplasia, type Maroteaux, characterized by dwarfism and short limbs, is caused by loss-of-function mutations in the Npr2 gene [11]. On the other hand, NPR3, which is thought to act as a clearance receptor, knock-out mice resemble CNP transgenic mice [12].

In this paper, we describe the first family with tall stature and macrodactyly of both great toes caused by a gain-of-function type mutation in the Npr2 gene. The mutant receptor, p.Val883Met, constitutively generates cGMP in vitro. Animal studies using the transgenic mice expressing the mutant NPR2 in chondrocytes demonstrated that skeletal overgrowth was associated with the overproduction of cGMP in cartilage. Our findings provide evidence that cGMP production downstream CNP/NPR2 system regulates the proliferation and differentiation of chondrocytes and determines skeletal growth.

Source

Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. ola.nilsson@nih.gov

Abstract

The overall body size of vertebrates is primarily determined by longitudinal bone growth at the growth plate. With age, the growth plate undergoes programmed senescence, causing longitudinal bone growth to slow and eventually cease. Indirect evidence suggests that growth plate senescence occurs because stem-like cells in the growth plate resting zone have a finite proliferative capacity that is gradually exhausted. Similar limits on replication have been observed when many types of animal cells are placed in cell culture, an effect known as the Hayflick phenomenon. However, we found that the number of population doublings of rabbit resting zone chondrocytes in culture did not depend on the age of the animal from which the cells were harvested, suggesting that the mechanisms limiting replicative capacity of growth plate chondrocytes in vivo are distinct from those in vitro. We also observed that the level of DNA methylation in resting zone chondrocytes decreased with age in vivo. This loss of methylation appeared to occur specifically with the slow proliferation of resting zone chondrocytes in vivo and was not observed with the rapid proliferation of proliferative zone chondrocytes in vivo (i.e. the level of DNA methylation did not change from the resting zone to the hypertrophic zone), with proliferation of chondrocytes in vitro, or with growth of the liver in vivo. Thus, the overall level of DNA methylation decreases during growth plate senescence. This finding is consistent with the hypothesis that the mechanism limiting replication of growth plate chondrocytes in vivo involves loss of DNA methylation and, thus, loss of DNA methylation might be a fundamental biological mechanism that limits longitudinal bone growth in mammals, thereby determining the overall adult size of the organism.

PMID: 16002553         [PubMed – indexed for MEDLINE]