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Heparin-binding growth-associated molecule (pleiotrophin) is a neurite outgrowth-promoting secretory protein that lines developing fiber tracts in juvenile CNS (central nervous system). Previously, we have shown that heparin-binding growth-associated molecule (HB-GAM) reverses the CSPG (chondroitin sulfate proteoglycan) inhibition on neurite outgrowth in the culture medium of primary CNS neurons and enhances axon growth through the injured spinal cord in mice demonstrated by two-photon imaging. In this study, we have started studies on the possible role of HB-GAM in enhancing functional recovery after incomplete spinal cord injury (SCI) using cervical lateral hemisection and hemicontusion mouse models. In vivo imaging of blood-oxygen-level-dependent (BOLD) signals associated with functional activity in the somatosensory cortex was used to assess the sensory functions during vibrotactile hind paw stimulation. The signal displays an exaggerated response in animals with lateral hemisection that recovers to the level seen in the sham-operated mice by injection of HB-GAM to the trauma site. The effect of HB-GAM treatment on sensory-motor functions was assessed by performance in demanding behavioral tests requiring integration of afferent and efferent signaling with central coordination. Administration of HB-GAM either by direct injection into the trauma site or by intrathecal injection improves the climbing abilities in animals with cervical hemisection and in addition enhances the grip strength in animals with lateral hemicontusion without affecting the spontaneous locomotor activity. Recovery of sensory signaling in the sensorimotor cortex by HB-GAM to the level of sham-operated mice may contribute to the improvement of skilled locomotion requiring integration of spatiotemporal signals in the somatosensory cortex.

Nerve endings in skin are involved in physiological processes such as sensing(1) as well as in pathological processes such as neuropathic pain(2). Their close-to-surface positioning facilitates microscopic imaging of skin nerve endings in living intact animal. Using multiphoton microscopy, it is possible to obtain fine images overcoming the problem of strong light scattering of the skin tissue. Reporter transgenic mice that express EYFP under the control of Thy-1 promoter in neurons (including periphery sensory neurons) are well suited for the longitudinal studies of individual nerve endings over extended periods of time up to several months or even life-long. Furthermore, using the same femtosecond laser as for the imaging, it is possible to produce highly selective lesions of nerve fibers for the studies of the nerve fiber restructuring. Here, we present a simple and reliable protocol for longitudinal multiphoton in vivo imaging and laser-based microsurgery on mouse skin nerve endings.

Among other glial cell types such as microglia, oligodendrocytes and radial glia, astrocytes are known to be involved in brain function; metabolically supporting neurons, regulating blood flow dynamics, participating in the development of pathological states, sensing and modulating synaptic activity. At the same time the complex astrocytic morphology, with a number of highly ramified peripheral processes located near the synaptic terminals, suggests them as a possible source for morpho-functional plasticity in the brain. This thesis summarizes the work on the in vitro development and further in vivo implementation, using a gene delivery system, of a tool for suppressing activity-dependent astrocytic motility. Calciuminduced astrocyte process outgrowth and its dependence on Profilin-1, novel in vivo gene delivery approaches, a demonstration of astrocytic motility in vivo and the independence of visual processing from astrocytic motility rates are the main findings of the project. The results described in this work increase our understanding of the interactions occurring between astrocytes and neurons as well as the consequences for brain function. Glia-soluihin kuuluvat astrosyytit ovat tiedettävästi osa aivojen toimintaa. Astrosyytit tukevat metabolisesti neuroneita, säätelevät verenkierron dynamiikkaa, ovat hyvin läsnä patoloogisten tilojen kehittymisessä, mukana aistimassa ja muuntamassa synaptista aktiivisuutta. Samanaikaisesti astrosyyttejen kompleksi morfologia, läheinen sijainti synaptisien terminalejen kanssa viittaavat mahdolliseen morfo-funtionaaliseen muovautumiseen aivoissa. Tämä väitöskirja keskittyy töihin jotka kehittävät in vitro ja in vivo tekniikoita jolla voidaan käyttää geeni jakelu menetelmää joka vaimentaa astrosyyttejen liikkuvuutta. Keskeiset havainnot tässä väitöskirjassa ovat astrosyyttejen kasliumin indusoima haarottuminen joka on riippuvainen Profiliini-1:stä ja havainnollistaminen astrosyyttejen liikkuvuudesta in vivo menetelmillä ja astrosyyttejen liikkuvuus aste joka on itsenäinen visuaalisesta prosessoinnista. Kuvaillut tulokset tässä väitöskirjassa kohentavat meidän ymmärrystä astrosyytetjen ja neuronejen välisestä kanssakäymisestä ja niiden seuraamus aivojen toiminnassa.