Background Limited data exist on the presence and function of immune-competent cells in chronic tendinopathic tendons, and their potential role in inflammation and tissue healing.
Objectives To quantify subtypes of immune-competent cells in biopsies from non-ruptured chronic tendinopathic Achilles tendons and healthy control tendons.
Methods Fifty patients with non-ruptured chronic Achilles tendinopathy and 15 healthy subjects were included. At time of inclusion, the Achilles tendons were examined clinically and evaluated with ultrasound with regard to tendon thickness and Doppler flow grade immediately before an ultrasound-guided tendon biopsy was obtained. Tissue samples were evaluated immunohistochemically by quantifying the presence of macrophages (CD68-KP1+), iron+ hemosiderophages (Perls Blue), T-lymphocytes (CD3+), B-lymphocytes (CD20+), natural killer cells (CD56+), mast cells (NaSDCl+), Schwann cells (S100+) and endothelial cells (CD34+) using a stereological technique. Cell counts were expressed as number of positive cell profiles per biopsy area (c/a), except for CD68-KP1 and CD34, which were quantified using a point counting grid to estimate number of grid hits of stained cells which were then calibrated to the total biopsy area (expressed as cell fractional area (%)). Descriptive data are reported as median and range if nothing else specified. Comparisons between groups were made with Mann-Whitney U tests or Fisher's Exact Tests. The level of significance was set at P <0.05.
Results Macrophages, T-lymphocytes, mast cells, and natural killer cells were observed in the majority (range: 52–96%) of biopsies from non-ruptured chronic tendinopathic Achilles tendons.
Conclusions This study provides evidence for the presence of immune-competent cells in the majority of biopsies from non-ruptured chronic tendinopathic Achilles tendons. Macrophages and endothelial cells were significantly more numerous in chronic tendinopathic tendons than in healthy tendons.
Disclosure of Interest : None declared