Effects of low-intensity pulsed ultrasound on the infrapatellar fat pad in knee osteoarthritis: a randomized, double blind, placebo-controlled trial

[Purpose] We investigated the effects of low-intensity pulsed ultrasound (LIPUS) irradiation of the infrapatellar fat pad (IFP) combined with therapeutic exercise for management of knee osteoarthritis (knee OA). [Participants and Methods] The study included 26 patients with knee OA, who were randomized into the LIPUS group (patients underwent LIPUS + therapeutic exercise) and the therapeutic exercise group (patients underwent sham LIPUS + therapeutic exercise). We measured changes in the patellar tendon-tibial angle (PTTA) and in IFP thickness, IFP gliding, and IFP echo intensity after 10 treatment sessions to determine the effects of the aforementioned interventions. We additionally recorded changes in the visual analog scale, Timed Up and Go Test, the Western Ontario and McMaster Universities Osteoarthritis Index, and Kujala scores, as well as range of motion in each group at the same end-point. [Results] Compared with patients in the therapeutic exercise group, those in the LIPUS group showed significant post-treatment improvements in PTTA, VAS, and Kujala scores, as well as in range of motion. [Conclusion] The combined use of LIPUS irradiation of the IFP and therapeutic exercise is a safe and effective modality to reduce IFP swelling, relieve pain, and improve function in patients with knee OA.

Influence of new coronavirus pandemic on behavior and awareness of young nurses and nursing students in Japan

Background

Although mental health disorders of health care workers in the coronavirus disease 2019 (COVID-19) pandemic have been focused, little is known about the psychological impact on nurses and the influence on their behavior and awareness, such as professionalism and views on life and death, in Japan where there are fewer cases of infection and deaths than in other countries. Moreover, the influence of the pandemic on nursing students is still unclear.

Methods

An online questionnaire survey was conducted among nurses and nursing students. Feelings during the state of emergency (at the peak of the pandemic) in Japan, changes in behavior and awareness after the rise of COVID-19, and the associated factors influencing these changes were analyzed, comparing nurses with nursing students.

Results

Significantly increased scores of anxiety/fear (p < .005) and voluntary restraint (p < .005) and significantly decreased score of motivation (p < .005) were observed during the state of emergency in both nurses and students. Scores of experience of discrimination (p < .005) and consideration of premature retirement (p < .01) were significantly increased in nurses. Moreover, preventive behavior (p < .005), lifestyle (p < .005), anxiety about nursing (p < .005) and views on life and death (p < .005) significantly changed after the rise of COVID-19 in both nurses and students. Only nurses reported significant damage to their professionalism (p < .01). Anxiety/fear and/or voluntary restraint and/or decreased motivation during the state of emergency were major factors associated with these changes. Also, the type of hospital, experience of care of infected patients and sex affected some of the changes. Voluntary restraint (p = .008), increased preventive behavior (p = .021) and decreased motivation (p = .005) were more marked in nurses than in students, while change in views on life and death was greater in students than in nurses (p = .002).

Conclusion

The COVID-19 pandemic has had a psychological impact on nurses and nursing students, associated with changes in behavior and awareness even in Japan. Of note, the COVID-19 pandemic has affected nurses’ professionalism and views on life and death. This study demonstrates the importance of having a coping strategy for anxiety and damaged professionalism in nurses, and education on life and death in nursing students.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12912-021-00724-x.

Beneficial effect of laughter therapy on physiological and psychological function in elders

AIM

In the present study we investigated the effect of laughter therapy on physiological and psychological function in older people.

DESIGN

An open-label trial.

METHODS

Seventeen older people who regularly attended an elderly day care centre were recruited. Stand-up comedy as laughter therapy was performed once a week for 4 weeks. Parameters of physiological and psychological function were evaluated before and after laughter therapy.

RESULTS

Laughter therapy intervention resulted in a significant reduction in systolic blood pressure and heart rate, accompanied by a significant increase in plasma concentration of serotonin and a significant decrease in salivary concentration of chromogranin A. Questionnaire surveys of SF-8, GDS-15, and Vitality Index demonstrated alleviation of depression and improvement of sociability and activity in older people. Laughter therapy could be expected to become a practical treatment to improve quality of life of older people in an elderly day care centre.

Therapeutic effect of intra-articular injection of ribbon-type decoy oligonucleotides for hypoxia inducible factor-1 on joint contracture in an immobilized knee animal model

BACKGROUND

Limited range of motion (ROM) as a result of joint contracture in treatment associated with joint immobilization or motor paralysis is a critical issue. However, its molecular mechanism has not been fully clarified and a therapeutic approach is not yet established.

METHODS

In the present study, we investigated its molecular mechanism, focusing on the role of a transcription factor, hypoxia inducible factor-1 (HIF-1), which regulates the expression of connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF), and evaluated the possibility of molecular therapy to inhibit HIF-1 activation by ribbon-type decoy oligonucleotides (ODNs) for HIF-1 using immobilized knee animal models.

RESULTS

In a mouse model, ROM of the immobilized knee significantly decreased in a time-dependent manner, accompanied by synovial hypertrophy. Immunohistochemical studies suggested that CTGF and VEGF are implicated in synovial hypertrophy with fibrosis. CTGF and VEGF were up-regulated at both the mRNA and protein levels at 1 and 2 weeks after immobilization, subsequent to up-regulation of HIF-1 mRNA and transcriptional activation of HIF-1. Of importance, intra-articular transfection of decoy ODNs for HIF-1 in a rat model successfully inhibited transcriptional activation of HIF-1, followed by suppression of expression of CTGF and VEGF, resulting in attenuation of restricted ROM, whereas transfection of scrambled decoy ODNs did not.

CONCLUSIONS

The present study demonstrates the important role of HIF-1 in the initial progression of immobilization-induced joint contracture, and indicates the possibility of molecular treatment to prevent the progression of joint contracture prior to intervention with physical therapy. Copyright © 2016 John Wiley & Sons, Ltd.

Electric Field Exposure Improves Subjective Symptoms Related to Sleeplessness in College Students: A Pilot Study of Electric Field Therapy for Sleep Disorder

Background:

Objective:

Methods:

Results:

Conclusion:

Leucine-rich alpha 2 glycoprotein promotes Th17 differentiation and collagen-induced arthritis in mice through enhancement of TGF-β-Smad2 signaling in naïve helper T cells

Background

Leucine-rich alpha 2 glycoprotein (LRG) has been identified as a serum protein elevated in patients with active rheumatoid arthritis (RA). Although the function of LRG is ill-defined, LRG binds with transforming growth factor (TGF)-β and enhances Smad2 phosphorylation. Considering that the imbalance between T helper 17 (Th17) cells and regulatory T cells (Treg) plays important roles in the pathogenesis of RA, LRG may affect arthritic pathology by enhancing the TGF-β-Smad2 pathway that is pivotal for both Treg and Th17 differentiation. The purpose of this study was to explore the contribution of LRG to the pathogenesis of arthritis, with a focus on the role of LRG in T cell differentiation.

Methods

The differentiation of CD4 T cells and the development of collagen-induced arthritis (CIA) were examined in wild-type mice and LRG knockout (KO) mice. To examine the influence of LRG on T cell differentiation, naïve CD4 T cells were isolated from LRG KO mice and cultured under Treg- or Th17-polarization condition in the absence or presence of recombinant LRG.

Results

In the CIA model, LRG deficiency led to ameliorated arthritis and reduced Th17 differentiation with no influence on Treg differentiation. By addition of recombinant LRG, the expression of IL-6 receptor (IL-6R) was enhanced through TGF-β-Smad2 signaling. In LRG KO mice, the IL-6R expression and IL-6-STAT3 signaling was attenuated in naïve CD4 T cells, compared to wild-type mice.

Conclusions

Our findings suggest that LRG upregulates IL-6R expression in naïve CD4 T cells by the enhancement of TGF-β-smad2 pathway and promote Th17 differentiation and arthritis development.

Wound healing potential of lavender oil by acceleration of granulation and wound contraction through induction of TGF-β in a rat model

Background

Although previous studies have suggested that lavender oil promote wound healing, no study has examined the molecular mechanisms of its effect. In this study, we investigated the effect of lavender oil on various steps of wound healing and its molecular mechanism, focusing on transforming growth factor-β (TGF-β).

Methods

Circular full-thickness skin wounds were produced on rats. Control solution or lavender oil was topically applied to the wounds on alternating days for 14 days.

Results

The area of wounds topically treated with lavender oil was significantly decreased as compared to that of wounds of control rats at 4, 6, 8, and 10 days after wounding. Topical application of lavender oil induced expression of type I and III collagen at 4 days after wounding, accompanied by an increased number of fibroblasts, which synthesize collagen. Induced expression of type III collagen by topical application of lavender oil was reduced to control level at 7 days after wounding although increased expression of type I collagen still continued even at 7 days, suggesting rapid collagen replacement from type III to type I in wounds treated with lavender oil. Importantly, expression of TGF-β in wounds treated with lavender oil was significantly increased as compared to control. Moreover, an increased number of myofibroblasts was observed in wounds treated with lavender oil at 4 days after wounding, suggesting promotion of differentiation of fibroblasts through induction of TGF-β, which is needed for wound contraction.

Conclusion

This study demonstrated that topical application of lavender oil promoted collagen synthesis and differentiation of fibroblasts, accompanied by up-regulation of TGF-β. These data suggest that lavender oil has the potential to promote wound healing in the early phase by acceleration of formation of granulation tissue, tissue remodeling by collagen replacement and wound contraction through up-regulation of TGF-β. The beneficial effect of lavender oil on wound healing may raise the possibility of new approaches as complementary treatment besides conventional therapy.

Effect of angiotensin II receptor blocker, olmesartan, on turnover of bone metabolism in bedridden elderly hypertensive women with disuse syndrome

AIMS

Although recent studies suggest that several antihypertensive drugs could reduce the risk of bone fracture, it is still unclear how these drugs act on bone remodeling, especially in elderly women with severe osteoporosis with disuse syndrome. In the present study, we investigated the effects of a calcium channel blocker (CCB) and an angiotensin II receptor blocker (ARB) on bone metabolism in elderly bedridden women with hypertension and disuse syndrome.

METHODS

Elderly bedridden women (aged >75 years) receiving antihypertensive therapy treated with CCB were recruited in the present study. The participants were divided into two groups--CCB group and ARB group--and followed up to 12 months.

RESULTS

Markers of bone resorption were markedly increased, suggesting accelerated bone resorption in the participants of the present study. In the follow-up period, the patients treated with a CCB showed a significant decrease in bone mineral density in a time-dependent manner, accompanied by a significant increase in bone resorption markers, whereas treatment with olmesartan inhibited bone loss, associated with attenuation of increased bone resorption markers. Bone mineral density of femoral neck in the CCB group was significantly lower than that in the ARB group at 6 months.

CONCLUSION

The present study showed inhibitory effects of an ARB on bone resorption in hypertensive patients with accelerated bone resorption, such as elderly bedridden women, and indicated an important role of the renin-angiotensin system in bone metabolism. In elderly hypertensive patients, ARB might be expected to have additional beneficial potential to maintain bone health in bedridden patients.

Comparative analysis of the effects of anti-IL-6 receptor mAb and anti-TNF mAb treatment on CD4+ T-cell responses in murine colitis

BACKGROUND

The efficacy of anti-tumor necrosis factor monoclonal antibody (anti-TNF mAb) for Crohn's disease (CD) is well established, and anti-interleukin-6 receptor (anti-IL-6R) mAb has also been reported to be effective in CD. It is, however, unclear if the efficacy and mechanisms of both agents are different in CD therapy.

METHODS

Using an adoptive transfer colitis model, we compared the efficacy of anti-IL-6R mAb, anti-TNF mAb, and TNF receptor-Fc fusion protein (TNFR-Fc), and their modes of action on CD4+ T cells. We also investigated the role of Th1 and Th17 cells in colitis using the same model.

RESULTS

The histological scores for the anti-IL-6R mAb and anti-TNF mAb groups but not for TNFR-Fc group were much lower than that for the control group, and the score was the lowest for the anti-IL-6R mAb group. The frequency of proliferating CD4+ T cells was reduced in anti-IL-6R mAb and anti-TNF mAb groups, but not in the TNFR-Fc group, whereas the frequency of apoptotic CD4+ T cells was similar in all groups. Anti-IL-6R mAb suppressed the induction of Th17 cells and increased the frequency of lamina propria regulatory T cells, whereas anti-TNF mAb exerted no influence on CD4+ T-cell differentiation. A deficiency in interferon-γ and/or IL-17 in CD4+ T cells reduced the severity of colitis.

CONCLUSIONS

Our findings suggest that suppression of the proliferation of pathogenic CD4+ T cells is the major mode of action of biological agents for colitis therapy. Anti-IL-6R mAb might have benefits in CD patients with Th17 dominance and impaired Treg frequency.

Global iron connections between desert dust, ocean biogeochemistry, and climate

The environmental conditions of Earth, including the climate, are determined by physical, chemical, biological, and human interactions that transform and transport materials and energy. This is the "Earth system": a highly complex entity characterized by multiple nonlinear responses and thresholds, with linkages between disparate components. One important part of this system is the iron cycle, in which iron-containing soil dust is transported from land through the atmosphere to the oceans, affecting ocean biogeochemistry and hence having feedback effects on climate and dust production. Here we review the key components of this cycle, identifying critical uncertainties and priorities for future research.

Identification of promoter regions involved in cell- and developmental stage-specific osteopontin expression in bone, kidney, placenta, and mammary gland: an analysis of transgenic mice

Cell-specific expression of GFP under the control of different lengths of the osteopontin promoter in transgenic mice identified the positive and negative regulatory regions for respective cell types. The results provide new insights for physiological and pathological expression of the osteopontin gene.

INTRODUCTION

Osteopontin (OPN) is a major non-collagenous bone matrix protein that is involved in normal and pathological calcification and is expressed in a tissue-specific manner. To investigate how such tissue-specific OPN gene expression is regulated in vivo, transgenic mice expressing the green fluorescent protein (GFP) reporter gene controlled by different lengths of the OPN promoter were generated.

MATERIALS AND METHODS

Cell- and developmental stage-specific osteopontin expression in transgenic mice was examined by Northern blotting, immunoblotting, fluorescence examination, and in situ hybridization and compared with those of OPN.

RESULTS AND CONCLUSIONS

The line bearing the -5505 to +14 region of the OPN promoter was shown by Northern blotting and immunoblotting to express GFP in the same cells that express endogenous OPN (osteoblasts, hypertrophic chondrocytes, renal and mammary gland epithelial cells, and granulated metrial gland [GMG] placental cells) at the same stage in development. Thus, the 5.5-kb -5505 to +14 promoter region is sufficient for proper tissue-specific OPN expression. The lines carrying shorter segments of the OPN promoter showed different expression patterns. These patterns revealed a putative cis-acting element in the -5269 to -5263 region that restricts OPN expression to hypertrophic chondrocytes and a mammary gland-specific expressing element and a GMG cell-specific enhancing element in the -5505 to -3156 region. Furthermore, the -3155 to -1576 region seems to contain positive renal epithelial cell- and GMG cell-specific expression motif(s) as well as a negative regulatory element that prevents OPN expression in fibroblasts. Moreover, the -1576 to -910 region seems to contain a positive osteoblast-specific-expressing element. Thus, the 5.5-kb OPN promoter contains multiple cis-acting elements encoding positive and negative cell-specific regulatory systems.

Difference of osteopontin gene regulation between bone and kidney

Osteopontin is a sialoprotein that is expressed in various cells. It plays a variety of important roles in cell adhesion, migration, signaling, calcification, and immunity. Its diverse functions indicate that the regulation of osteopontin may also vary extensively among tissues. Although osteopontin promoter has been studied in vitro, in vivo analyses may be more appropriate for elucidating osteopontin's functions. In an attempt to investigate osteopontin gene expression, we generated transgenic mice in which the bacterial beta-galactosidase reporter gene was conjugated downstream of osteopontin promoter. The osteopontin promoter was a mouse -910 bp upstream fragment, which we had previously found functional in 3T3 cells. Among 34 transgenic founders, 13 mice were transgenic, as determined with the polymerase chain reaction. Osteopontin and beta-galactosidase signals were evaluated with in situ hybridization. Among the 13 transgenic mice, 3 were beta-galactosidase-positive. In these transgenic mice, osteopontin signals were observed in bones and kidneys, whereas beta-galactosidase message was detected only in bones. This suggests that the -910 bp osteopontin promoter is active in bones but not in kidneys. These data imply that the promoter region required for osteopontin expression in kidneys may differ from that in bones.

Enhanced expression of Runx2/PEBP2alphaA/CBFA1/AML3 during fracture healing

The cause of the dramatic increase in expression of the osteopontin gene during fracture healing was studied in a mouse experimental model. Semiquantitative reverse transcription-polymerase chain reaction, Northern blotting, and in situ hybridization analysis showed that the enhanced expression took place prior to callus formation. The change in the expression pattern of collagenous and noncollagenous bone matrix proteins in addition to Ets-1 and Runx2, major transcription factors of osteopontin, were examined and compared to that of osteopontin. Although Ets-1 expression showed no significant change during fracture healing, enhanced expression of Runx2 corresponding to that of osteopontin was observed. Furthermore, in situ hybridization demonstrated that osteopontin-expressing cells also express the Runx2 gene. The results indicated the possibility that Runx2 is a major regulator of osteopontin during fracture healing.

Role of osteopontin in bone remodeling caused by mechanical stress

Changes in the number and proportion of osteopontin mRNA (Opn) expressing osteocytes and osteoclasts caused by the mechanical stress applied during experimental tooth movement were examined in the present study. Opn expression was detected in the osteocytes on the pressure side at the early stage, and gradually spread to those on the tension side and also to the osteoblasts and bone-lining cells in the alveolar bone. Only 3.3% of the osteocytes located on the pressure side expressed Opn in the interradicular septum of control rats; in contrast, the value was increased to 87.5% at 48 h after the initiation of tooth movement. These results indicate that these cells responded to mechanical stress loaded on the bone with expression of the osteopontin gene. Following the increased expression of Opn in these cells, a 17-fold greater number of osteoclasts compared with the control and numerous resorption pits were observed on the pressure side of the alveolar bone. Injection of arginine-glycine-aspartic acid-serine peptide but not that of arginine-glycine-glutamic acid-serine peptide strongly inhibited the increase in the number of osteoclasts. Furthermore, an in vitro migration assay demonstrated the chemotactic activity of osteopontin (OPN) on the precursor of osteoclasts. Our study strongly suggests that OPN is an important factor triggering bone remodeling caused by mechanical stress.

Transcriptional regulation of osteopontin gene in vivo by PEBP2alphaA/CBFA1 and ETS1 in the skeletal tissues

Osteopontin (Opn) and polyoma enhancer-binding protein (PEBP) 2alphaA/core binding factor (CBFA) 1 have been suggested to play important roles in ossification. The overlapping localization of opn and PEBP2alphaA/CBFA1 mRNA, and the marked decrease of opn mRNA expression in PEBP2alphaA knockout mice, indicated that the transcription of opn gene was controlled by PEBP2alphaA. In the present study, we determined the direct regulation of PEBP2alphaA on the opn promoter activity. Opn promoter activity was markedly enhanced by PEBP2alphaA and ETS1 in a synergistic manner. The synergistic effect was diminished when either the PEBP2alphaA or ETS1 binding site was mutated, or the spatial arrangement of these sites was mutated by a 4-nt insertion. The distance between these sites was important for transactivation but not protein-DNA binding. The direct interaction between PEBP2alphaA and ETS1 was depended on protein-DNA binding. These results suggested that the specific spatial arrangement of both sites and direct interaction between PEBP2alphaA and ETS1, were essential for promoter function. Furthermore, endogenous opn mRNA was decreased with the introduction of dominant negative PEBP2alphaA to MC3T3/E1 cells expressing endogenous PEBP2alphaA, ETS1 and opn. These findings suggest that PEBP2alphaA and ETS1 cooperate in vivo to regulate expression of the opn gene in the skeletal tissue. Cell type-specific regulation of Opn gene expression will also be discussed.

Expression of bone matrix proteins mRNA during distraction osteogenesis

Distraction osteogenesis is a recently advanced principle of bone lengthening in which a bone separated by osteotomy is subjected to slow progressive distraction using an external fixation device. Appropriate mechanical tension-stress is believed not to break the callus but rather to stimulate osteogenesis. To study the molecular features of this process, the expression and localization of the mRNAs encoding osteopontin (OPN), osteocalcin (OC), matrix Gla protein (MGP), osteonectin (ON), and collagen type I and I during distraction osteogenesis were examined by in situ hybridization and Northern blot analysis. The process can be divided into three distinct phases: the lag phase for 7 days between osteotomy and the beginning of distraction, the distraction phase for 21 days, and the consolidation phase for several weeks. The histologic and molecular events taking place during the lag phase were similar to those observed in fracture healing. The osteotomy site was surrounded by external callus consisting of hyaline cartilage. As distraction started at the rate of 0.25 mm/12 h, the cartilaginous callus was elongated, deformed, and eventually separated into proximal and distal segments. The chondrocytes were stretched along the tension vector and became fibroblast-like in shape. Although morphologically these cells were distinguishable from osteogenic cells, they expressed OPN, OC, and alkaline phosphatase mRNAs. As distraction advanced, the cartilaginous callus was progressively replaced by bony callus by endochondral ossification and thereafter new bone was formed directly by intramembranous ossification. OPN mRNA was detected in preosteoblasts and osteoblasts at the boundary between fibrous tissue and new bone. ON, MGP, and OC mRNAs appeared early in the differentiation stage. The variety of cell types expressing mRNA encoding bone matrix proteins in distraction osteogenesis was much greater than that detected in the embryonic bone formation and fracture healing process. Moreover, the levels of OPN, ON, MGP, and OC mRNA expression markedly increased during the distraction phase. These results suggested that mechanical tension-stress modulates cell shape and phenotype, and stimulates the expression of the mRNA for bone matrix proteins.

Differential in situ expression of alpha2(XI) collagen mRNA isoforms in the developing mouse

Type XI collagen is an essential structural component of the extracellular matrix of cartilage and plays a role in collagen fibril formation and skeletal morphogenesis. The expression of all three type XI collagen genes is not restricted to cartilage. In addition, alternative exon usage seems to increase the structural diversity and functional potential of type XI collagen during development. In order to investigate type XI collagen expression during development, we have examined alpha2(XI) and alpha1(XI) collagen genes by in situ hybridization in mice. Transcripts of the alpha2(XI) collagen gene were first detected in the notochord of mouse embryos after 11.5 days of gestation. Subsequently, alpha2(XI) mRNA was mainly found in the cartilaginous tissues of the developing limbs and axial skeleton together with transcripts of the alpha1(XI) gene. The alpha2(XI) transcripts seemed to be alternatively spliced isoforms lacking exons 6-8, which code for an acidic domain. Expression of alpha2(XI) outside the cartilage was relatively restricted, whereas expression of the alpha1(XI) gene was widespread. However, expression of alpha2(XI) transcripts containing exons 6-8 was found in non-chondrogenic tissues, including the calvarium and periosteum where intramembranous ossification occurs. These results indicate that alpha2(XI) mRNA isoforms are differentially expressed in various tissues during development. In addition, alpha2(XI) mRNA isoforms containing alternative exons are present in osteogenic cells, and their expression may be closely related to the formation of bone or cartilage.

Impaired expression of noncollagenous bone matrix protein mRNAs during fracture healing in ascorbic acid-deficient rats

In scorbutic patients, fractures are slow to heal because of impaired collagen synthesis. To investigate the influence of impaired collagen synthesis on the differentiation and proliferation of osteogenic and chondrogenic cells, we examined the expression of genes encoding bone matrix proteins, including osteonectin (ON), osteopontin (OPN), osteocalcin (OC), and matrix Gla protein (MGP), as differentiation markers for osteogenic and chondrogenic cells during fracture healing in Osteogenic Disorder Shionogi (ODS) rats, which have a hereditary defect in the ability to synthesize ascorbic acid (Asc). In ODS rats without Asc supplementation, intramembranous ossification was completely inhibited. Although a few fibroblast-like cells expressing ON mRNA were observed, no OPN mRNA-expressing cells were detected. During endochondral ossification, a small amount of metachromatic staining cartilage appeared at the fracture site, but there was no provisional calcification zone in the cartilage. Chondrocytes expressed ON and MGP mRNAs, but not OPN mRNA. When Asc was given to these rats, callus formation was soon detected around the fracture site, while OPN mRNA was expressed by differentiated osteoblasts and hypertrophic chondrocytes. Our data indicate that impaired collagen synthesis due to Asc deficiency inhibited the increase of ON and MGP mRNA-expressing cells as well as the appearance of OPN mRNA-expressing cells. Since OPN is considered to play an important role in normal and pathological mineralization, lack of OPN mRNA expression accompanying impaired collagen synthesis may have a role in defective mineralization and delayed fracture healing in scurvy.

Three modes of ossification during distraction osteogenesis in the rat

We developed a rat model of limb lengthening to study the basic mechanism of distraction osteogenesis, using a small monolateral external fixator. In 11-week-old male rats we performed a subperiosteal osteotomy in the midshaft of the femur with distraction at 0.25 mm every 12 hours from seven days after operation. Radiological and histological examinations showed a growth zone of constant thickness in the middle of the lengthened segment, with formation of new bone at its proximal and distal ends. Osteogenic cells were arranged longitudinally along the tension vector showing the origin and the fate of individual cells in a single section. Typical endochondral bone formation was prominent in the early stage of distraction, but intramembraneous bone formation became the predominant mechanism of ossification at later stages. We also showed a third mechanism of ossification, 'transchondroid bone formation'. Chondroid bone, a tissue intermediate between bone and cartilage, was formed directly by chondrocyte-like cells, with transition from fibrous tissue to bone occurring gradually and consecutively without capillary invasion. In situ hybridisation using digoxigenin-11-UTP-labelled complementary RNAs showed that the chondroid bone cells temporarily expressed type-II collagen mRNA. They did not show the classical morphological characteristics of chondrocytes, but were assumed to be young chondrocytes undergoing further differentiation into bone-forming cells. We found at least three different modes of ossification during bone lengthening by distraction osteogenesis. We believe that this is the first report of such a rat model, and have shown the validity of in situ hybridisation techniques for the study of the cellular and molecular mechanisms involved in distraction osteogenesis.

THREE MODES OF OSSIFICATION DURING DISTRACTION OSTEOGENESIS IN THE RAT

We developed a rat model of limb lengthening to study the basic mechanism of distraction osteogenesis, using a small monolateral external fixator. In 11-week-old male rats we performed a subperiosteal osteotomy in the midshaft of the femur with distraction at 0.25 mm every 12 hours from seven days after operation.

Radiological and histological examinations showed a growth zone of constant thickness in the middle of the lengthened segment, with formation of new bone at its proximal and distal ends.

Osteogenic cells were arranged longitudinally along the tension vector showing the origin and the fate of individual cells in a single section. Typical endochondral bone formation was prominent in the early stage of distraction, but intramembraneous bone formation became the predominant mechanism of ossification at later stages. We also showed a third mechanism of ossification, ‘transchondroid bone formation’. Chondroid bone, a tissue intermediate between bone and cartilage, was formed directly by chondrocyte-like cells, with transition from fibrous tissue to bone occurring gradually and consecutively without capillary invasion.

In situ hybridisation using digoxigenin-11-UTP-labelled complementary RNAs showed that the chondroid bone cells temporarily expressed type-II collagen mRNA. They did not show the classical morphological characteristics of chondrocytes, but were assumed to be young chondrocytes undergoing further differentiation into bone-forming cells.

We found at least three different modes of ossification during bone lengthening by distraction osteogenesis. We believe that this is the first report of such a rat model, and have shown the validity of in situ hybridisation techniques for the study of the cellular and molecular mechanisms involved in distraction osteogenesis.