The objective of the present study was to evaluate the capacity of a tissue-engineered bone complex of recombinant human bone morphogenetic protein 2 (rhBMP-2)-mediated dental pulp stem cells (DPSCs) and nano-hydroxyapatite/collagen/poly(L-lactide) (nHAC/PLA) to reconstruct critical-size alveolar bone defects in New Zealand rabbit. Autologous DPSCs were isolated from rabbit dental pulp tissue and expanded ex vivo to enrich DPSCs numbers, and then their attachment and differentiation capability were evaluated when cultured on the culture plate or nHAC/PLA. The alveolar bone defects were treated with nHAC/PLA, nHAC/PLA+rhBMP-2, nHAC/PLA+DPSCs, nHAC/PLA+DPSCs+rhBMP-2, and autogenous bone (AB) obtained from iliac bone or were left untreated as a control. X-ray and a polychrome sequential fluorescent labeling were performed postoperatively and the animals were sacrificed 12 weeks after operation for histological observation and histomorphometric analysis. Our results showed that DPSCs expressed STRO-1 and vementin, and favored osteogenesis and adipogenesis in conditioned media. DPSCs attached and spread well, and retained their osteogenic phenotypes on nHAC/PLA. The rhBMP-2 could significantly increase protein content, alkaline phosphatase activity/protein, osteocalcin content, and mineral formation of DPSCs cultured on nHAC/PLA. The X-ray graph, the fluorescent, histological observation, and histomorphometric analysis showed that the nHAC/PLA+DPSCs+rhBMP-2 tissue-engineered bone complex had an earlier mineralization and more bone formation inside the scaffold than nHAC/PLA, nHAC/PLA+rhBMP-2, and nHAC/PLA+DPSCs, or even autologous bone. Implanted DPSCs' contribution to new bone was detected through transfected eGFP genes. Our findings indicated that stem cells existed in adult rabbit dental pulp tissue. The rhBMP-2 promoted osteogenic capability of DPSCs as a potential cell source for periodontal bone regeneration. The nHAC/PLA could serve as a good scaffold for autologous DPSC seeding, proliferation, and differentiation. The tissue-engineered bone complex with nHAC/PLA, rhBMP-2, and autologous DPSCs might be a better alternative to autologous bone for the clinical reconstruction of periodontal bone defects.

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The flow of ionic currents within the neurons of cerebral cortex produces a magnetic field that can be detected outside the human scalp. The dominant contribution is attributed to pyramidal cells, which are preferentially oriented perpendicular to the cortical surface. In general, it is not possible to deduce a unique representation of the spatial configuration of these cortical sources from a measurement of their field pattern alone. However, accurate a priori knowledge of the geometry of the underlying cerebral cortex makes it possible to infer the spatial configuration of these transcortical current sources, moment by moment, without imposing a simplified model such as a small set of current dipoles. To achieve such a realistic magnetic source image, we have introduced what we call the "Minimum-Norm Least-Squares Inverse" (MNLS inverse) for the magnetic problem. The MNLS inverse provides the least residual error in accounting for the measured field pattern, with a source current distribution having minimum power. An extension of this procedure provides an inverse solution for average field power, as opposed to field per se. This makes it possible to define spatial configurations of spontaneous cortical activity not phase-locked to a sensory stimulus. Rhythmic activity such as the occipital alpha rhythm is one example. Thus, it is possible to determine spatial patterns of enhanced or suppressed cortical rhythms that accompany cognitive processes and some pathological conditions. This paper provides the necessary background for understanding these recent developments, as well as examples of how they might be used.