I do not have access to the full study.
"[We] investigate the effects of combined treatment of exogenous mesenchymal stem cells (MSCs) and low intensity pulsed ultrasound (LIPUS) on fracture healing by comparing LIPUS-MSC, MSC and control (CTL) groups. Quantitative callus width/area demonstrated that the MSC-LIPUS group had the best healing, MSC group the second and CTL group the poorest with significant differences among each at different time points. MSC-LIPUS had the highest bone volume/tissue volume. [There was] a significantly faster remodeling in late phase in MSC-LIPUS and MSC groups. Combined treatment of MSCs and LIPUS was beneficial to fracture healing. Regenerative power and homing ability of MSCs were shown by promotion in fracture healing and locally found green fluorescent protein (GFP)-labeled MSCs at fracture calluses."
"a metal blade (weighted 500 g) dropping from a height of 35 cm, was used to create the fracture at the midshaft of the femur. The quality of fracture with fracture gap [was] smaller than 0.5 mm and displacement [was] less than 0.5 mm"
" Large amount of cartilaginous tissues bridged the osseous callus in the first week. At week 2, woven bone was observed in MSC-LIPUS and MSC groups with active endochondral ossification at the edge of cartilaginous tissues, while this phenomenon was shown in CTL group at week 3. The area of cartilaginous tissues tended to reduce in both MSC-LIPUS and MSC groups at week 3 and more woven bone replaced the cartilaginous tissues to bridge the fracture site in week 4, particularly in MSC-LIPUS group. There were, however, still large amounts of cartilaginous tissues in CTL group in week 4."
"LIPUS has been proven to increase blood flow around fracture site that might promote angiogenesis, MSCs migration and, hence, fracture healing."It's possible LIPUS could do this to normal bone too.
Combined Treatment of Alendronate and Low-Intensity Pulsed Ultrasound (LIPUS) Increases Bone Mineral Density at the Cancellous Bone Osteotomy Site in Aged Rats: A Preliminary Study.
"9-month-old Sprague-Dawley rats, with a unilateral proximal tibial osteotomy, were treated with alendronate (daily, 1 µg/kg) plus sham-LIPUS, saline plus LIPUS (20 min/day), alendronate plus LIPUS, or saline plus sham-LIPUS as a control for 4 weeks"
"The combined therapy significantly increased BMD at the osteotomy site at 4 weeks compared with the control, without affecting the contralateral, non-osteotomized tibia. Both alendronate and LIPUS alone also exerted a positive, albeit less, effect on BMD in the affected limb. Alendronate and LIPUS cooperate to enhance BMD during metaphyseal bone healing."
LIPUS and Alendronate were applied to both osteomy and non-osteomy bone.
"The ultrasound signals were transferred for 20 min per day with a spatial average-temporal average (SATA) intensity of 30 mW/cm2"
The region of interest was the epiphysis. It is possible that LIPUS can increase other parameters besides BMD in non-osteomy bone. BMD was the only parameter that was measured.
Low-intensity ultrasound increases FAK, ERK-1/2, and IRS-1 expression of intact rat bones in a noncumulative manner.
"daily 20-minute LIPUS [was] applied to intact tibias.
FAK, ERK-1/2, and IRS-1 expression and activation [was detected] from the stimulated intact tibias at 7, 14, and 21 days of daily 20-minute LIPUS.
LIPUS increased FAK expression (at 7 days), ERK-1/2 (at 14 days), and IRS-1 (at 7 days), but expression decreased 7 days later, indicating a noncumulative effect of LIPUS. As only FAK expression was detected at 21 days, these observations suggest LIPUS influences nuclear reactions that may be modulated by a major cellular mechanism preferentially inhibiting IRS-1 expression and not FAK expression. Increased ERK-1/2 expression at 14 days suggests the differing mechanisms for promoting ERK-1/2, FAK, and IRS-1 syntheses. IRS-1 expression behaved similarly to FAK expression; therefore, LIPUS may modulate growth factor pathways. LIPUS increased sustained FAK and ERK-1/2 activation, but not IRS-1, suggesting sustained ERK-1/2 activation is not the result of mechanically induced growth factor activation."
"[Male] WH rats, aged 12 weeks [were used]"
ERK 1/2 was phosphorylated at Tyr-204. p-ERK 1/2 was the same in both control and LIPUS group at 21 days indicating a conditioning response.
"IGF-1 expression may be increased by LIPUS"
12 week old WH mice are still growing.
"Seven days after the augmentation of FAK (at 14 days) and ERK-1/2 (at 21 days) expression, their expression decreased, showing a noncumulative effect of LIPUS on intact bone and suggesting there is a regulatory mechanism in bone cells, similar to negative feedback, that is activated after the augmentation of FAK and ERK-1/2 expression. In healthy bone, this mechanism may have antineoplastic finalities, because FAK is persistently increased in neoplasia"
Mechanical means to improve bone strength: ultrasound and vibration.
"At intensities of 5 to 300 W/cm2, [ultrasound] is used as a surgical tool to fragment calculi{mineral deposits}"
"LIPUS uses a significantly low intensity and does not yield major temperature changes (typically <1°C). However, even these minor temperature changes are hypothesized to stimulate enzymatic processes involving some sensitive enzymes, such as matrix metalloproteinase 1 and collagenase"
Low-intensity pulsed ultrasound (LIPUS) and cell-to-cell communication in bone marrow stromal cells.
"Single or daily-multiple LIPUS treatment at 1.5MHz, 30mW/cm(2), for 20min was applied to BMSC. BMSC form functional gap junctions and single LIPUS treatment significantly increased the intracellular dye transfer between BMSC. Activated phosphorylation of ERK1/2 and p38 by LIPUS stimulation was diminished when cells were treated with a gap junction inhibitor 18β-glycyrrhetinic acid (18β). We further demonstrated that 18β diminished the significant increase in alkaline phosphatase activity following LIPUS stimulation."
"Gap junctions mediate the intercellular exchange of regulatory ions and small molecules that allow metabolic cooperation between adjacent cells and control cell differentiation and growth. In bone, gap junctions have been suggested to be central to the transmission of biophysical stimuli"
LIPUS increased ALP by 30% and this was diminished by 18B.
The development and validation of a LIPUS system with preliminary observations of ultrasonic effects on human adult stem cells.
" a custom LIPUS system was designed and validated by exploring the effects of using different pulse repetition frequency (PRF) parameters on human adipose derived adult stem cells (hASCs) and bone marrow derived mesenchymal stem cells (hMSCs), two common stem cell sources for creating bone constructs in vitro. Changing the PRF was found to affect cellular response to LIPUS stimulation for both cell types. Proliferation of LIPUS-stimulated cells was found to decrease for hASCs by d 7 for all three groups compared with unstimulated control cells (P = 0.008, 0.011, 0.014 for 1 Hz, 100 Hz and 1 kHz PRF, respectively) and for hMSCs by d 14 (donor 1: P = 0.0005, 0.0002, 0.0003; donor 2: P = 0.0003, 0.0002, 0.0001; for PRFs of 1 Hz, 100 Hz, and 1 kHz, respectively). Additionally, LIPUS was shown to strongly accelerate osteogenic differentiation of hASCs based on amount of calcium accretion normalized by total DNA (P = 0.003, 0.001, 0.003, and 0.032 between control/100 Hz, control/1 kHz, 1 Hz/1 kHz, and 100 Hz/1 kHz pulse repetition frequencies, respectively)."
LIPUS increased calcium accretion per total DNA for hMSCs as well.
Application of low-intensity ultrasound to growing bone in rats.
"he longitudinal growth and bone density of the femur and tibia in young rats was measured after application of an ultrasound transducer emitting 1.5-MHz pulsed ultrasound (30 mW/cm2, SATA) for 20 min/day. After 28 days, no length difference was detected (< or = 2%) compared to the sham-treated leg or to unexposed controls. Also, no significant difference in bone mineral density (BMD) of the femur or tibia was found (< or = 6%). In a repeated experiment in which a periosteal trauma stimulus was created in the femoral diaphysis, the ultrasound also had no effect on growth or BMD."
"Four-week-old Sprague–Dawley male rats (approximately 90 g) [were used]"
Ultrasound was applied to a huge region which could be part of the problem and why there wasn't significant growth.
Ultrasound though seemed to increase femur length but decrease tibia length.
" in fracture experiments, disruption of the cortex may provide better access to activated endosteal and periosteal cells than in the intact limb."
Effects of low-intensity pulsed ultrasound on the differentiation of C2C12 cells.
"Pluripotent mesenchymal cell line C2C12 were cultured in differentiation medium with or without the addition of LIPUS stimulation. The ultrasound signal consisted of 1.5 MHz at an intensity of 70 mW/cm2{more than twice the 30mW/cm2 of LIPUS} for 20 min for all cultures. To verify the cell lineage after LIPUS stimulation, mRNA expression of cellular phenotype-specific markers characterizing osteoblasts (Runx2, Msx2, Dlx5, AJ18), chondroblasts (Sox9), myoblasts (MyoD), and adipocytes (C/EBP, PPARgamma) was studied s. The protein expression of Runx2 and activated phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38 MAPK) were performed using Western blotting. The mRNA expression of Runx2, Msx2, Dlx5, AJ18, and Sox9 was increased markedly by the LIPUS stimulation, whereas the expression of MyoD, C/EBP, and PPARgamma was drastically decreased. In the Western blot analysis, LIPUS stimulation increased Runx2 protein expression and phosphorylation of ERK1/2 and p38 MAPK. LIPUS stimulation converts the differentiation pathway of C2C12 cells into the osteoblast and/or chondroblast lineage via activated phosphorylation of ERK1/2 and p38 MAPK{LSJL likely phosphorylates these two proteins as well}."
"C2C12 cells are a subclone of C2 myoblasts"
"Dlx5 expression correlates with osteoblast differentiation"
"The maximum expression of Dlx5 occurs in the final stages of osteoblast differentiation in vitro when the extracellular matrix mineralizes, suggesting that Dlx5 may be involved in the differentiation of the osteogenic cells. In contrast, Msx2 is predominantly expressed by proliferating osteoblasts and preosteoblasts, but decreases according to terminal osteoblast differentiation"
"Chick wing bud mesenchymal cell micromass culture allows the study of a variety of developmental mechanisms, ranging from cell adhesion to pattern formation. However, many cells remain in contact with an artificial substratum, which can influence cytoskeletal organisation and differentiation. An ultrasound standing wave trap facilitates the rapid formation of 2-D monolayer cell aggregates with a defined zero time-point, independent from contact with a surface. Aggregates formed rapidly (within 2 min) and intercellular membrane spreading occurred at points of contact. This was associated with an increase in peripheral F-actin within 10 min of cell-cell contact and aggregates had obtained physical integrity by 30 min. The chondrogenic transcription factor Sox9 could be detected in cells in the ultrasound trap within 3 h (ultrasound exposure alone was not responsible for this effect). This approach facilitates the study of the initial cell-cell interactions that occur during condensation formation and demonstrates that a combination of cell shape and cytoskeletal organisation is required for the initiation and maintenance of a differentiated phenotype, which is lost when these phenomena are influenced by contact with an artificial substrate."
"[N-CAM and N-Cadherin while encouraging mesenchymal condensation, their] expression following condensation also inhibits chondrogenesis" Cadherin 7 may also be key for mesenchymal condensation.
"loss of Sox9 occurs due to reorganisation of the F-actin cytoskeleton"
The pressure generated was 110 kPa.
"During condensation, cells come together and are compacted and take on a rounded morphology, show peripheral actin organisation, form adhesive complexes and gap junctions, then begin to express Sox9"