Sensory nerve degeneration in a mouse model mimicking early manifestations of familial amyloid?polyneuropathy due to transthyretin Ala97Ser

摘要

Aims Sensory nerve degeneration and consequent abnormal sensations are the earliest and most prevalent manifestations of familial amyloid polyneuropathy (FAP) due to amyloidogenic transthyretin (TTR). FAP is a relentlessly progressive degenerative disease of the peripheral nervous system. However, there is a lack of mouse models to replicate the early neuropathic manifestations of FAP. Methods We established human TTR knock‐in mice by replacing one allele of the mouse Ttr locus with human wild‐type TTR (hTTR wt ) or human TTR with the A97S mutation (hTTR A97S ). Given the late onset of neuropathic manifestations in A97S‐FAP, we investigated nerve pathology, physiology, and behavioural tests in these mice at two age points: the adult group (8 – 56?weeks) and the ageing group (?104?weeks). Results In the adult group, nerve profiles, neurophysiology and behaviour were similar between hTTR wt and hTTR A97S mice. By contrast, ageing hTTR A97S mice showed small fibre neuropathy with decreased intraepidermal nerve fibre density and behavioural signs of mechanical allodynia. Furthermore, significant reductions in sural nerve myelinated nerve fibre density and sensory nerve action potential amplitudes in these mice indicated degeneration of large sensory fibres. The unaffected motor nerve physiology replicated the early symptoms of FAP patients, that is, sensory nerves were more vulnerable to mutant TTR than motor nerves. Conclusions These results demonstrate that the hTTR A97S mouse model develops sensory nerve pathology and corresponding physiology mimicking A97S‐FAP and provides a platform to develop new therapies for the early stage of A97S‐FAP.