Protective effect of post-ischaemic viral delivery of heat shock proteins in vivo

Abstract

Heat shock proteins (HSPs) function as molecular chaperones involved in protein folding, transport and degradation and, in addition, they can promote cell survival both in vitro and in vivo after a range of stresses. Although some in vivo studies have suggested that HSP27 and HSP70 can be neuroprotective, current evidence is limited, particularly when HSPs have been delivered after an insult. The effect of overexpressing HSPs after transient occlusion of the middle cerebral artery in rats was investigated by delivering an attenuated herpes simplex viral vector (HSV-1) engineered to express HSP27 or HSP70 30 mins after tissue reperfusion. Magnetic resonance imaging scans were used to determine lesion size and cerebral blood flow at six different time points up to 1 month after stroke. Animals underwent two sensorimotor tests at the same time points to assess the relationship between lesion size and function. Results indicate that post-ischaemic viral delivery of HSP27, but not of HSP70, caused a statistically significant reduction in lesion size and induced a significant behavioural improvement compared with controls. This is the first evidence of effective post-ischaemic gene therapy with a viral vector expressing HSP27 in an experimental model of stroke.

Figure 1

Representative centre slices (slice 5) of multislice T₂-weighted spin echo data sets. The scans show the lesion area (bright) in HSP27-, HSP70-, and LacZ-injected rats at 24 h, 1 week, and 3 weeks after MCA occlusion. Values represent absolute lesion volume (mm³±s.e.m.) determined on multislice T₂-weighted scans per treatment group at all time points.

Figure 2

Regional analysis of absolute lesion volume estimates in frontal (1 and 2), mid (3, 4, 5, and 6), and posterior (7, 8, and 9) slices calculated form multislice T₂-weighted spin echo images at six different time points in HSP-treated and control animals.

Figure 3

Percentage difference in lesion size at 24 h after stroke calculated from single-slice DWI and T₂-weighted images. The mismatch between the lesion area calculated from ADC maps and the lesion defined on T₂-weighted images is larger in HSP27-treated animals than in HSP70-treated or control animals.

Figure 4

Difference in the time to removal of the sticky tape from the affected paw (left) in HSP-treated and control animals up to 1 month after stroke.

Figure 5

Representative end-point cryosections of HSP27-injected animals and LacZ-injected controls stained for HSP27 (red) and synaptophysin (green) (63×10). (A) LacZ-injected and MCA-occluded control showing no colocalization of HSP27 and synaptophysin. (B) HSP27-injected and MCA-occluded animal stained for the same proteins showing no colocalization. (C) Detail of the scar edge in an HSP27-injected animal (scale bar: 10 μm).