Tissue samples
Histological examination of phosphorylated a-syn in different peripheral tissue biopsies of PD cases has been subject of increasing interest [12, 14]. Detection of phosphorylated a-syn aggregates in the autonomic nerve fibers of salivary glands and skin shown promise as an early histological biomarker [35, 36]. However, the finding is not specific for PD as similar deposits can be observed in other alpha-synucleinopathies, too [35]. Similarly, gastrointestinal biopsy could represent an accessible strategy to assess a-syn neuropathology in PD patients [37].
Peripheral tissue miRNAs may be of significance as hsa-miR-1260a from PD patients nasal and buccal swabs was significantly increased as compared with healthy controls [38]. Interestingly, non-coding miRNAs, miR-134 and miR-141 downregulated CDNF levels in an experimental setting calling for clinical studies on the biomarker properties of these miRNAs [34].