PDGF Receptor β Is a Potent Regulator of Mesenchymal Stromal Cell Function

Mesenchymal stromal cells (MSCs) in bone marrow are important for bone homeostasis. Although platelet‐derived growth factor (PDGF) has been reported to be involved in osteogenic differentiation of MSCs, the role remains controversial and the network of PDGF signaling for MSCs has not been clarified. To clarify the underlying regulatory mechanism of MSC functions mediated by PDGF, we deleted the PDGF receptor (PDGFR)β gene by Cre‐loxP strategy and examined the role of PDGF in osteogenic differentiation of MSCs and fracture repair. In cultured MSCs, the mRNA expression of PDGF‐A, ‐B, ‐C, and ‐D as well as PDGFRα and β was detected. Depletion of PDGFRβ in MSCs decreased the mitogenic and migratory responses and enhanced osteogenic differentiation as evaluated by increased alkaline phosphatase (ALP) activity and mRNA levels of ALP, osteocalcin (OCN), bone morphogenetic protein (BMP) 2, Runx2, and osterix in quantitative RT‐PCR. PDGF‐BB, but not PDGF‐AA, inhibited osteogenic differentiation accompanied by decreased ALP activity and mRNA levels, except for BMP2. These effects of PDGF‐BB were eliminated by depletion of PDGFRβ in MSCs except that PDGF‐BB still suppressed osterix expression in PDGFRβ‐depleted MSCs. Depletion of PDGFRβ significantly increased the ratio of woven bone to callus after fracture. From the combined analyses of PDGF stimulation and specific PDGFRβ gene deletion, we showed that PDGFRβ signaling distinctively induces proliferative and migratory responses but strongly inhibits osteogenic differentiation of MSCs. The effects of PDGFRα on the osteogenic differentiation were very subtle. PDGFRβ could represent an important target for guided tissue regeneration or tissue engineering of bone.     

Somatostatin immunoreactive C cells in thyroid glands from various mammalia species

The relative distribution of somatostatin- and calcitonin-containing cells in thyroid glands from various mammalian species was investigated by immunoperoxidase staining, and the concentration of immunoreactive somatostatin by radioimmunoassay. In the thyroid glands of guinea pigs and rabbits, most of the calcitonin cells were also immunoreactive to the somatostatin antiserum, and high concentration of immunoreactive somatostatin was obtained. On the other hand, in the thyroids of other animal species—rats, dogs, pigs, cows, goats, cats, monkeys, mice, and hamsters—only a few C cells revealed the immunoreaction for somatostatin, and the concentration of somatostatin was low. In all animal species studied, the somatostatin was present in the same cells that contain calcitonin, though in guinea pigs and rats there were some C cells containing a large number of reaction products for somatostatin but very few for calcitonin. Thus, it was concluded that there was a considerable variation in somatostatin immunoreactivity of thyroid C cells from species to species.     

Effects of NKH477, a forskolin derivative, and dibutyryl-cyclic AMP on adrenal catecholamine release in response to splanchnic nerve stimulation, acetylcholine, DMPP and muscarine in anesthetized dogs

Summary— The effects of NKH477, a water-soluble forskolin derivative, and dibutyryl-cyclic adenosine monophosphate (dbcAMP) on the release of adrenal catecholamines (CAs) in response to splanchnic nerve stimulation (SNS), acetylcholine (ACh), the nicotinic receptor stimulant 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP) and muscarine were examined in anesthetized dogs. NKH477, dbcAMP and the cholinergic agonists were infused and injected, respectively, into the adrenal gland intra-arterially. SNS (3 Hz) or injections of ACh (3 μg), DMPP (2 μg) and muscarine (2 μg) produced increases in CA output determined from adrenal venous blood. Both NKH477 infusion (0.3, 1 and 3 μg/min) and dbcAMP infusion (0.1, 0.3 and 1 mg/min) caused dose-dependent enhancement of the SNS-, ACh- and DMPP-induced increases in CA output, whereas they failed to affect the muscarine-induced increases in CA output. Neither NKH477 nor dbcAMP affected basal CA output. Cyclic AMP (cAMP) overflow determined from adrenal venous blood increased during NKH477 infusion. These results indicate that NKH477 and dbcAMP have facilitatory effects on adrenal CA release mediated by nicotinic receptors, but not by muscarinic receptors in the dog, and suggest the selective action of cAMP on nicotinic mechanism.     

Estimation of obscure ictal epileptic activity in scalp EEG

Summary We have produced a method to estimate ictal localized epileptic activity hidden among the background in scalp EEGs. When the visually completely different waveforms of the epileptic and background activities are nearly orthogonal, epileptic activity may be approximately extracted from the EEG data matrix by singular value decomposition with subsequent orthogonal rotation to match the distribution of one component with that of the epileptic source. A simulation study was carried out using a matrix mimicking the scalp EEG with an inconspicuous ictal epileptic activity from a dipole source. This hidden epileptic activity was approximately recovered by matching the dipole of interest with the epileptic dipole, even when the simulated waveforms of the epileptic and background activities were not exactly orthogonal. High linear correlation between these two types of waveforms hampered the recovery of the epileptic activity. In another simulation study employing two epileptic dipoles producing activities with the same waveform and a brief time lag, it was indicated that the temporal relationship between the epileptic activities could be also estimated using the cross-correlation function. In the preliminary clinical application of this method to the ictal EEGs of complex partial seizures, rhythmic activities with seemingly epileptic waveforms were estimated at the dipoles which were located in the vicinity of cortical lesions revealed by neuroimaging studies. These activities were indicated to appear before any change in the scalp EEG. We hope for the clinical application of this method for noninvasive estimation of inconspicuous ictal epileptic activity.The authors thank Prof. Peter K.H. Wong of the Department of Paediatrics, University of British Columbia, Canada, and Prof. Yutaka Tanaka and Mr. Kim Hyun Bin of the Department of Environmental and Mathematical Sciences, Faculty of Environmental Science and Technology, Okayama University, Japan, for their technical suggestions. This study was aided by a grant from the Japan Epilepsy Research Foundation.     

Long-term follow-up studies on Iodine-131 treatment of hyperthyroid graves’ disease based on the measurement of thyroid volume by ultrasonography

In the present series of studies, the long-term (four year) effect of 80 Gy of¹³¹I treatment was evaluated in patients with hyperthyroid Graves’ disease whose thyroid volumes have been accurately estimated with a high resolution ultrasound scanner. One year after¹³¹I treatment, 23.1 % (3 out of 13 patients) remained hyperthyroid, 69.2% (9 out of 13) became euthyroid, and 7.7% (1 out of 13) were in a hypothyroid state. Since three patients in a hyperthyroid state one year after treatment were subsequently treated with either antithyroid drugs or additional¹³¹I treatment, the remaining ten patients (9 euthyroid and 1 hypothyroid patients) have been followed up for three more years. Two patients developed a hypothyroid state three years after treatment and one patient four years after treatment. Overall, 60% (6 out of 10 patients) were in a euthyroid state and 40% (4 out of 10) in a hypothyroid state, four years after 80 Gy¹³¹I treatment. There was no significant difference between eu- and hypothyroid groups in the sex ratio, age, radiation dose, therapeutic dose, thyroid gland volume, 24-hr¹³¹I uptake, the effective half-life of¹³¹I in the thyroid or the duration of hyperthyroidism. In our preliminary studies, the incidence of late hypothyroidism in our¹³¹I treatment is similar to those previously reported. These suggest that uncertain factor(s), such as inhomogeneity of iodine distribution in the thyroid, unequal sensitivity of the thyroid cells to the radiation, and/or persistent destructive effects of the autoimmune process may influence the long-term effect of¹³¹I treatment of Graves’ disease.