Rapid differentiation of epithelial cell types in aged biological samples using autofluorescence and morphological signatures

Abstract

Establishing the tissue source of epithelial cells within a biological sample is an important capability for forensic laboratories. In this study we used Imaging Flow Cytometry (IFC) to analyze individual cells recovered from buccal, epidermal, and vaginal samples that had been dried between 24 hours and more than eight weeks. Measurements capturing the size, shape, and fluorescent properties of cells were collected in an automated manner and then used to build a multivariate statistical framework for differentiating cells based on tissue type. Results showed that epidermal cells could be distinguished from vaginal and buccal cells using a discriminant function analysis of IFC measurements with an average classification accuracy of ~94%. Ultimately, cellular measurements such as these, which can be obtained non-destructively, may provide probative information for many types of biological samples and complement results from standard genetic profiling techniques.

Fig 1. Image gallery for three epithelial cell tissue sources.

IFC Brightfield images for buccal cells (columns 1–3), epidermal cells (columns 4–6), and vaginal cells (columns 7–9). Each image frame is 50 μm x 50 μm. Object identifiers are included with each image.

Fig 2. Discriminant Function Analysis of epithelial cells from three tissue sources using IFC variables.

The first discriminant function (x-axis) accounted for ~74% of the between group variation and the second discriminant function (y-axis) accounted for ~26%.

Fig 3. Discriminant function analysis of cell populations derived from different contributors for buccal and epidermal tissue sources.

Buccal cells (left) were dried for 48 hours at room temperature and epidermal cell samples (right) were dried for 24 hours at room temperature prior to analysis. Red, green, blue circles represent three different individuals in each graph.