300 Acta Neuropathol (2011) 122:293–311 Fig. 3 Expression of the astrocytic glucose and lactate transporter involved in cerebral metabolism and neuronal functioning is reduced in astrocytes cultured from mid-stage TG arcAb mouse brain with concomitant decreased lactate release. a GLUT1 and MCT1 (astro- cytic lactate transporter) were down-regulated in whole cell lysate preparations of astrocyte cultures originating from mid-stage TG Early-stage astrogliosis precedes wide-spread Ab plaque burden and is paralleled by increased vascular basement laminin staining and increased soluble laminin secretion by TG arcAb astrocytes ex vivo Astrogliosis was found in all three disease stages in TG arcAb mice, increasing with age, especially surrounding diffuse Ab plaques in the neuropil and vessels bearing CAA or vascular Ab deposits. The presence of astrogliosis in the early-stage mice was found around arteries descending from leptomeningeal vessels and was remark- able since only little extracellular Ab plaque burden was present in this age group (Fig. 4a). The extensive astrogl- iosis around these blood vessels was paralleled by an increased immunoreactivity against laminin (Fig. 4a), a major component of the VBM. Moreover, astrocytes themselves were clearly immunopositive for laminin too; especially astrocytic dendrites presented a strong laminin staining (Fig. 4b, arrow). Laminin was concentrated around and within the astrocytes and following the astro- cytic staining structure rather than that for Ab (Fig. 4b). Interestingly, a more diffuse laminin staining was observed around astrocytes as well (Fig. 4b, asterisk). It is known that astrocytes can secrete laminin [8] and we, therefore, measured soluble laminin in media of TG and NTG ex vivo-cultured astrocytes derived from early and mid-stage arcAb mice. The TG astrocytes in both the age groups were found to secrete more laminin than their NTG counterparts (Fig. 4c, early-stage and d, mid-stage). Ab induces astrocyte endfeet retraction leading to neurovascular uncoupling, starting at early-stage pathology To further investigate the astrocytic abnormalities found in the TG arcAb mice, we studied the structural appearance of astrocyte endfeet at early and late pathological stages of the 123 arcAb mice. Staining for b actin served as loading control for all samples. b Astrocytic lactate release in media of the same astrocyte cultures originating from mid-stage TG and NTG arcAb mice. A decreased lactate concentration was found in culture media of TG astrocytes as compared to astrocytes from NTG littermate brains disease (Fig. 5). As was observed in other transgenic AD mouse models [61] we found signs of neurovascular uncou- pling suggested by swelling and retraction of astrocyte endfeet of astrocytes surrounding (vascular) Ab deposits in both early and late-stage animals (Fig. 5a, b). Although the cerebro- vasculature in late-stage arcAb mice is severely affected by CAA, we found that on non-CAA-laden vessels in these aged mice contacts between astrocyte endfeet and the vasculature was maintained (Fig. 5b, arrows). An Ab-induced endfeet detachment and swelling was further suggested by the observation of astrocyte endfeet swelling and endfeet loss of astrocytes surrounding diffuse Ab plaques (Fig. 5b, asterisk) similar to CAA-induced endfeet abnormalities (Fig. 5a, arrows). Furthermore, astrocytes surrounding the small number of Ab deposits which were present in the early-stage mice, all showed endfeet abnormalities. Loss of astrocytic b dystroglycan expression in late-stage TG arcAb mice is consistent with decreased interactions between astrocyte endfeet and vasculature and is paralleled by cerebral extravasation of blood-derived IgG Astrocyte endfeet attach to cerebral vessels via interactions between endfeet b dystroglycan and vascular laminin [2, 53]. To understand if the observed astrocyte endfeet retractions as shown in Fig. 5 could be associated with impaired b dystro- glycan-laminin interactions, the expression of astrocytic b dystroglycan was explored. We found that the astrocytic expression of b dystroglycan was signiﬁcantly decreased in TG arcAb mice (Fig. 6a, c, e, g). Loss of b dystroglycan was paralleled by the cerebral presence of endogenous mouse IgG around diffuse Ab plaques (Fig. 6a, c, and e, arrows) and was most pronounced in the cortical regions and hippocampus (Fig. 6a, e and s). The presence of mouse IgG was detected by the same secondary anti-mouse antibody (ﬂuorescein iso- thiocyanate/FITC-tagged donkey anti-mouse IgG, Jackson