Ryo Hanyu

Sympathetic control of bone mass regulated by osteopontin

The sympathetic nervous system suppresses bone mass by mechanisms that remain incompletely elucidated. Using cell-based and murine genetics approaches, we show that this activity of the sympathetic nervous system requires osteopontin (OPN), a cytokine and one of the major members of the noncollagenous extracellular matrix proteins of bone. In this work, we found that the stimulation of the sympathetic tone by isoproterenol increased the level of OPN expression in the plasma and bone and that mice lacking OPN (OPN-KO) suppressed the isoproterenol-induced bone loss by preventing reduced osteoblastic and enhanced osteoclastic activities. In addition, we found that OPN is necessary for changes in the expression of genes related to bone resorption and bone formation that are induced by activation of the sympathetic tone. At the cellular level, we showed that intracellular OPN modulated the capacity of the β2-adrenergic receptor to generate cAMP with a corresponding modulation of cAMP-response element binding (CREB) phosphorylation and associated transcriptional events inside the cell. Our results indicate that OPN plays a critical role in sympathetic tone regulation of bone mass and that this OPN regulation is taking place through modulation of the β2-adrenergic receptor/cAMP signaling system.

Anabolic action of parathyroid hormone regulated by the β2-adrenergic receptor

Parathyroid hormone (PTH), the major calcium-regulating hormone, and norepinephrine (NE), the principal neurotransmitter of sympathetic nerves, regulate bone remodeling by activating distinct cell-surface G protein-coupled receptors in osteoblasts: the parathyroid hormone type 1 receptor (PTHR) and the β2-adrenergic receptor (β2AR), respectively. These receptors activate a common cAMP/PKA signal transduction pathway mediated through the stimulatory heterotrimeric G protein. Activation of β2AR via the sympathetic nervous system decreases bone formation and increases bone resorption. Conversely, daily injection of PTH (1–34), a regimen known as intermittent (i)PTH treatment, increases bone mass through the stimulation of trabecular and cortical bone formation and decreases fracture incidences in severe cases of osteoporosis. Here, we show that iPTH has no osteoanabolic activity in mice lacking the β2AR. β2AR deficiency suppressed both iPTH-induced increase in bone formation and resorption. We showed that the lack of β2AR blocks expression of iPTH-target genes involved in bone formation and resorption that are regulated by the cAMP/PKA pathway. These data implicate an unexpected functional interaction between PTHR and β2AR, two G protein-coupled receptors from distinct families, which control bone formation and PTH anabolism.

Nanogel‐based scaffold delivery of prostaglandin E2 receptor–specific agonist in combination with a low dose of growth factor heals critical‐size bone defects in mice

OBJECTIVE Regeneration of bone requires the combination of appropriate drugs and an appropriate delivery system to control cell behavior. However, the delivery of multiple drugs to heal bone is complicated by the availability of carriers. The aim of this study was to explore a new system for delivery of a selective EP4 receptor agonist (EP4A) in combination with low-dose bone morphogenetic protein 2 (BMP-2). METHODS Combined delivery of EP4A and BMP-2 was carried out with a nanogel-based scaffold in the shape of a disc, to repair critical-size circle-shaped bone defects in calvariae that otherwise did not heal spontaneously. RESULTS Combination treatment with EP4A and low-dose BMP-2 in nanogel efficiently activated bone cells to regenerate calvarial bone by forming both outer and inner cortical plates as well as bone marrow tissue to regenerate a structure similar to that of intact calvaria. EP4A enhanced low-dose BMP-2-induced cell differentiation and activation of transcription events in osteoblasts. CONCLUSION These data indicate that combined delivery of EP4A and low-dose BMP-2 via nanogel-based hydrogel provides a new system for bone repair.

Osteoblastic differentiation enhances expression of TRPV4 that is required for calcium oscillation induced by mechanical force

Mechanical stress is known to alter bone mass and the loss of force stimuli leads to reduction of bone mass. However, molecules involved in this phenomenon are incompletely understood. As mechanical force would affect signaling events in cells, we focused on a calcium channel, TRPV4 regarding its role in the effects of force stimuli on calcium in osteoblasts. TRPV4 expression levels were enhanced upon differentiation of osteoblasts in culture. We found that BMP-2 treatment enhanced TRPV4 gene expression in a dose dependent manner. BMP-2 effects on TRPV4 expression were suppressed by inhibitors for transcription and new protein synthesis. In these osteoblasts, a TRPV4-selective agonist, 4α-PDD, enhanced calcium signaling and the effects of 4α-PDD were enhanced in differentiated osteoblasts compared to the control cells. Fluid flow, as a mechanical stimulation, induced intracellular calcium oscillation in wild type osteoblasts. In contrast, TRPV4 deficiency suppressed calcium oscillation significantly even when the cells were subjected to fluid flow. These data suggest that TRPV4 is involved in the flow-induced calcium signaling in osteoblasts.

Per-1 is a specific clock gene regulated by parathyroid hormone (PTH) signaling in osteoblasts and is functional for the transcriptional events induced by PTH

Per‐1 is one of the clock genes and is known to regulate various biological events including bone mass determination. Parathyroid hormone is anabolic to bone while the mechanism of its action is not fully understood. Here, we examined the role of PTH on Per‐1 gene expression under osteoblast specific PTH signaling. Constitutively active PTH receptor (caPPR) expressed specifically in osteoblasts in transgenic mice activates Per‐1 gene expression in bone. This is specific as expression of other clock gene Bmal‐1 is not affected by caPPR over‐expression. Per‐1 is also expressed in osteoblastic cell line. Interestingly, Per‐1 expression is required for PTH signaling‐induced CRE dependent transcription. This is forming a positive feed back loop in the anabolic action of PTH signaling and Per‐1 in bone. These data indicate that PTH singling in osteoblasts activates Per‐1 gene expression in vivo in association with its anabolic action in bone at least in part through the regulation of transcriptional events. J. Cell. Biochem. 112: 433–438, 2011.

Case report: The operation for the lumbar disk herniation just after cesarean delivery in the third trimester of pregnancy

Highlights • We suggest treatment strategy for a pregnant woman with lumber disk herniation.• The discectomy was performed just after cesarean delivery in the third trimester.• There were not any complications with mother and baby after operation.• It is necessary to cooperate with a pediatrician, an obstetrician, and an anesthesiologist.• It is important to discuss in advance to be able to respond quickly for changeable situation.

Osteopontin deficiency enhances parathyroid hormone/ parathyroid hormone related peptide receptor (PPR) signaling-induced alteration in tooth formation and odontoblastic morphology

Parathyroid hormone/parathyroid hormone-related protein receptor (PPR) signaling is known to be involved in tooth development. In bone, extracellular matrix protein osteopontin (OPN) is a negative regulator of PPR signaling in bone formation. However, the role of OPN in modulation of PPR action in tooth development is not understood. Therefore, we examined the tooth in double mutant mice. Constitutively active PPR was expressed specifically in the odontoblasts and osteoblasts (caPPR-tg) in the presence or absence of OPN. Radiographic analysis indicated that the length of the third molar (M3) and the incisor was decreased in the caPPR-tg mice compared to wild type, and such reduction in molar and incisor length was further enhanced in the absence of OPN (caPPR-tg OPN-KO). With respect to histology of incisors, caPPR-tg induced high cellularity and irregularity in odontoblastic shape and this was enhanced by the absence of OPN. These morphological observations suggest that OPN modulates PPR signaling that are involved in tooth formation.

Schnurri-2 deficiency counteracts against bone loss induced by ovariectomy.

Schnurri (Shn)‐2 is a transcriptional modulator of bone formation and bone resorption and its deficiency causes low turnover state with higher cancellous bone mass due to the defects in osteoclasts that exceeds the defects in osteoblasts in mice. We addressed whether such low turnover of bone remodeling in Shn2 deficiency may be modulated in the absence of estrogen that induces high turnover state in vivo. Ovariectomy reduced bone mass in wild type compared to sham operated control mice and such reduction in bone mass was also observed in Shn2 deficient mice. However, due to the high levels of basal bone mass in Shn2 deficient mice, the bone mass levels after ovariectomy were still comparable to sham operated wild‐type mice. Analysis indicated that estrogen depletion increased bone resorption at similar levels in wild type and Shn2 deficient mice though the basal levels of osteoclast number was slightly lower in Shn2‐deficient mice. In contrast, basal levels of bone marrow cell mineralization in cultures were low in Shn2‐deficeint mice while estrogen depletion increased the mineralization levels to those that were comparable to sham wild type. This indicates that Shn2‐deficient mice maintain bone mass at the levels comparable to wild‐type sham mice even after ovariectomy‐induced bone loss and this correlates with the high levels of mineralization activity in bone marrow cells after ovariectomy. J. Cell. Physiol. 226: 573–578, 2011.

Minimally invasive endoscopic decompression of the intermatatarsal nerve for Morton's neuroma

BACKGROUND We presented case reports of endoscopic decompression for a Morton intermetatarsal neuroma. METHODS Three patients underwent surgery using an instrument designed to release the transverse carpal ligament for carpal tunnel syndrome. Each patient was 61, 56 and 24 years old. The mean follow up period was 1.5 years. RESULTS All patients experienced reduced pain postoperatively. The postoperative scar was very small (only 1 cm). There is no loss of sensation, no hematoma and no infection. CONCLUSION This procedure is simple, and the postoperative morbidity for the patient is minimal. There is rapid recovery with minimal risk of complications that are associated with open techniques. Therefore endoscopic decompression for Morton neuroma offers many advantages and should be studied in a larger number of patients.