Extracorporeal shock waves (ESW) have recently been used in resolving tendinitis. However, mechanisms by which ESW promote tendon repair is not fully understood. In this study, we reported that an optimal ESW treatment promoted healing of Achilles tendintis by inducing TGF-PI and IGF-I. Rats with the collagenease-induced Achilles tendinitis were given a single ESW treatment (0.16 mJ/mm' energy flux density) with 0, 200, 500 and 1000 impulses. Achilles tendons were subjected to biomechanical (load to failure and stiffness), biochemical properties (DNA, glycosaminoglycan and hydroxyproline content) and histological assessment. ESW with 200 impulses restored biomechanical and biochemical characteristics of healing tendons 12 weeks after treatment. However, ESW treatments with 500 and 1000 impulses elicited inhibitory effects on tendinitis repair. Histological observation demonstrated that ESW treatment resolved edema, swelling, and inflammatory cell infiltration in injured tendons. Lesion site underwent intensive tenocyte proliferation, neovascularization and progressive tendon tissue regeneration. Tenocytes at the hypertrophied cellular tissue and newly developed tendon tissue expressed strong proliferating cell nuclear antigen (PCNA) after ESW treatment, suggesting that physical ESW could increase the mitogenic responses of tendons. Moreover, the proliferation of tenocytes adjunct to hypertrophied cell aggregate and newly formed tendon tissue coincided with intensive TGF-PI and IGF-I expression. Increasing TGF-Dl expression was noted in the early stage of tendon repair, and elevated IGF-I expression was persisted throughout the healing period. Together, low-energy shock wave effectively promoted tendon healing. TGF-PI and IGF-I played important roles in mediating ESW-stimulated cell proliferation and tissue regeneration of tendon.

No abstract

Prolonged glucocorticoid treatment is known to cause osteoporosis or aseptic necrosis. Secreted frizzled-related proteins 1 (SFRP1) and low-density lipoprotein-related protein 5 (LRP5), a Wnt protein antagonist and a coreceptor, have been found to regulate skeletogenesis. Whereas recent studies have reported that excess glucocorticoid promotes bone loss, the biological role of SFRP1 and LRP5 in regulating glucocorticoid attenuation of bone formation is not fully understood. We showed that a supraphysiological level of glucocorticoid enhanced SFRP1 but not LRP5 expression of primary mesenchymal cell cultures in vitro and osteoblasts at metaphyseal trabecular endosteum and chondrocytes at calcified cartilage in vivo. Glucocorticoid augmentation of SFRP1 expression was transcriptionally mediated. The inhibitory action of glucocorticoid on osteogenic differentiation appeared to be regulated by SFRP1 mediation of beta-catenin destabilization because knocking down SFRP1 by RNA interference abrogated the supraphysiological level of glucocorticoid attenuation of osteogenesis. Recombinant human SFRP1 reduced the promoting effect of physiological level of glucocorticoid on cytosolic beta-catenin accumulation, runt-related transcription factor-2 activation, and osteogenic activities. Glucocorticoid and recombinant human SFRP1 significantly increased osteochondral cell apoptosis associated with reduced mineral density, biomechanical properties, trabecular bone volume, and midshaft cortical bone areas in rat femurs. These findings suggest that SFRP1 modulates glucocorticoid-induced bone loss. Regulation of Wnt/SFRP signal transduction can be used in the future as an alternative strategy for the prevention of glucocorticoid-induced osteoporosis.

No abstract

Bone cells respond to mechanical stimulation via mechanoreceptors and convert biophysical stimulation into biochemical signals that alter gene expression and cellular adaptation. Pulsed acoustic energy treatment raises membrane potential and induces osteogenic activity. How membrane-bound osteoblast mechanoreceptors convert physical ultrasound (US) stimuli into osteogenic responses is not fully understood. We demonstrated that low-intensity pulsed US treatment (200-W Ws pulse, 1 kHz, 30 mW/cm 2 ) elevated Cbfa1/Runx2 mRNA expression and progressively promoted osteocalcin mRNA expression in human osteoblasts. Pretreatment with pertussis toxin (PTX), but not with cholera toxin, suppressed US-augmented osteogenic transcription. This indicated that Gi proteins, but not Gs proteins, were involved in US promotion of osteogenic transcription. Further studies demonstrated US treatment could rapidly increase PTX-sensitive GK Ki protein levels and subsequently enhanced phosphorylation of extracellular signal-regulated kinase (ERK). PTX pretreatment signi¢cantly reduced US promotion of ERK activation. Moreover, inhibition of ERK activity by PD98059 suppressed US augmentation of Cbfa1/Runx2 and osteocalcin mRNA expression. Membranous GK Ki proteins and cytosolic ERK pathways acted as potent mechanosensitive signals in the response of osteoblasts to pulsed US stimulation.