Angiogenesis in parathyroid disease and association with VEGF
Angiogenesis has been demonstrated in normal parathyroid tissue in vitro and must occur in vivo to
allow for successful transplantation. Here we present data that angiogenesis also occurs in parathyroid
disease states and that VEGF (a known endothelial cell mitogen) expression is not evident in these
tissues.
Formalin fixed, paraffin embedded sections of human parathyroid tissue were stained with an
antibody to CD31 to visualise endothelial cells and separate sections stained with antibody to VEGF
using standard immunohistochemistry techniques. Microvessel counts were performed by two
(blinded) investigators. Western blot analysis of protein lysate of parathyroid tissue was also
performed using antibody to VEGF.
123 patients were studied (44 normal, 27 hyperplasia and 52 adenoma). Microvessel counts showed a
statistically significant (p < 0.05 compared with normal) and step-wise increase in microvessel count
between the different types of tissue. 120 parathyroid sections stained with antibody to VEGF with
positive control of normal kidney showed non-specific staining in all tissue types, a finding which was
repeated with Western blot analysis of protein derived from 1 normal, 2 adenomas and 2 hyperplasia
samples.
Here we have demonstrated evidence of angiogenesis that occurs in human parathyroid tissue when
diseased. Our data have not shown a significant expression ofVEGF in these samples. This finding
implies that either VEGF does not mediate angiogenesis in these tissues or that it does so transiently.
Alternatively VEGF may act in concentrations too small to be detected with these techniques. Gaining
a better understanding ofthe progression of angiogenesis in parathyroid disease may lead to the
development of novel therapeutic strategies.
Changes in Vascularity Associated with Chronic Allograft Nephropathy
This study aims to compare vascularity of kidneys with CAN versus normal. In addition, validation of
renal biopsy samples in the assessment of angiogenesis has been performed.
Tissue from transplant nephrectomies performed because of CAN (n=29), antecedent biopsies from
these grafts (n=18) and normal kidneys (n=61) were studied. Protocol renal transplant biopsies were
also studied. Tissue sections were immunostained with the endothelial cell antibody to CD31.
Changes in overall vascular patterns were noted and microvessel counts performed. Sections were
dual-stained with antibody to CD31 and the proliferation marker, MIB-1, to determine the presence of
proliferating endothelial cells. Microvessel counts were performed on paired samples of core biopsies
and cross-section of normal kidney and were compared in early protocol biopsy specimens from grafts
which develop CAN (n=10) with those where stable graft function continued (n=20). Macrophage
infiltration was studied using immunostaining to CD68.
CD31 staining from CAN nephrectomies exhibited diminished cortical and medullary staining and
was accompanied by a significant increase in proliferation index when compared with normal. There
was significant correlation in microvessel counts in core biopsies and the corresponding kidney crosssection. Early biopsies from grafts which developed CAN show significantly higher microvessel
counts compared with the corresponding nephrectomy. The number ofproliferating ECs was
significantly increased in this biopsy group compared with normal kidney but was not significantly
different compared with the CAN nephrectomy group. Early protocol biopsies from grafts which
developed CAN showed significantly higher microvessel counts compared with those with stable graft
function. A significant increase in macrophage infiltration was seen in CAN nephrectomies compared
with normal kidney.
This study demonstrates reduced density of CD31-positive microvessels in CAN compared with
normal. In addition, the investigation of changes in the microvasculature in CAN by study of core
biopsies has been validated and confirms preservation of normal vasculature in early CAN. Together
with evidence ofproliferating endothelial cells these findings support a hypothesis that, early in the
development ofCAN, angiogenesis is stimulated, but despite this attempt at tissue repair, progressive
microvascular loss occurs. The presence of significant numbers of macrophages may be of
aetiological importance or reflect changes relating to cessation of immunosuppression.
