Histomorphological and biochemical properties of plantar soft tissue in diabetes

Abstract

Background: Diabetes results in pathophysiological changes, leading to tissue that is unable to withstand and adapt to the same loads, resulting in breakdown. Certain locations are more susceptible to breakdown, yet differences between locations are largely not well understood. The authors performed a histological and biochemical analysis of isolated plantar adipose tissue at six relevant locations.

Methods: Tissue from six plantar locations (hallux, first, third and fifth metatarsal heads, lateral midfoot and calcaneus) was taken from fresh cadaveric feet of older diabetic and older non-diabetic intact donors. Histomorphological and biochemical analysis of isolated plantar tissue from both diabetic and non-diabetic feet at six relevant locations was performed.

Results: The main differences found between diabetic and non-diabetic tissue were in the thickness of the septal walls and the elastin content. Diabetic tissue had significantly thicker septal walls and an increased elastin concentration. When comparing the calcaneus to other locations, although there were no differences found in the thickness of the septal walls of diabetic tissue, elastin content was lower in the calcaneous tissue compared to the non-calcaneus sites.

Conclusions: Modifications in the structural and biochemical properties could translate to changes in the mechanical properties. This information could lead to an understanding of how the structural and biochemical changes result in an increase in susceptibility of tissue to breakdown with load at the different locations of the foot.

Keywords: Biochemical; Diabetic foot ulcer; Histomorphological; Plantar soft tissue.

Figure 1

Mean arithmetic thickness (left) and total elastin concentration (right) in diabetic and non-diabetic tissue at different foot locations: calcaneus (ca), lateral midfoot (la), hallus (ha), first, third and fifth metatarsal heads (m1, m3 and m5).

Figure 2

Representative images of the elastic septa in a) non-diabetic and b) diabetic plantar tissue stained with modified Hart’s. Elastin fibres stain black. Elastic fibres in diabetic tissue are frayed and fragmented, often resulting in thicker septal walls. Scale bar represents 50 µm.

Figure 3

Representative images of the elastic septa in a) non-diabetic and b) diabetic plantar tissue stained with Pico Sirus red. Under polarized light, collagen appears red-orange. Thicker collagen bundles (white arrow head) were observed in the diabetic tissue compared with the normal tissue. There were also regions of frayed and disordered collagen fibres (white arrow) observed in the diabetic septal walls compared with the normal tissue. Scale bar represents 200 µm.