The role of platelets and platelet-derived microvesicles in diabetic nephropathy.

Diabetic nephropathy (DN) is one of the complications of diabetes, which occurs
in 20-40% of diabetic patients. Glomerular injury is the main hallmark of DN,
resulting in glomerulosclerosis and albuminuria, which is stratified in
normoalbuminuria (albumin-to-creatinin ratio (ACR) <30mg/g ), microalbuminuria
(ACR 30-300mg/g) and macroalbuminuria (ACR >300mg/g).
Patients with diabetes are at increased risk for cardiovascular disease. This
risk is even more increased when renal insufficiency accompanies diabetes.
Increased platelet activity is one element that leads to this increased risk.
In diabetes, platelet activation is increased because of an altered balance
between pro- and anti-coagulant mechanisms, mainly caused by endothelial
injury. Also, platelets can be activated directly by high glucose levels.
Besides the importance of platelets in coagulation, mounting evidence shows
that platelets are also involved in inflammation and repair. Platelets are
involved in these processes by secreting a plethora of bioactive molecules
either directly or via platelet-derived microvesicles (PMV). PMVs are buddings
from the membrane or exosomes derived from intracellular granules. PMVs allows
communications between platelets and remote target cells. Recently, PMVs have
emerged as important mediators of intercellular transfer of bioactive
molecules, which appears to be crucial in normal physiology and under
pathological circumstances. Moreover, PMV contain a multitude of
platelet-derived effector molecules among which mRNAs and miRNAs. Platelet
inherit (pre-)mRNA from the megakaryocyte, as well as abundant and a diverse
array of miRNAs, which regulate de novo protein synthesis in both platelets
and their recipient cells. Recent studies showed interactions between PMV and
endothelial cells and macrophages, in both cases the protein expression was
miRNA-mediated. Endothelial cells and macrophages are crucial cell types
involved in DN development, therefore we suppose that PMV miRNAs are promising
mediators in DN development.
In summary, platelet activity and PMV levels are increased in diabetes.
However, the role of platelets and PMV in the progression of DN is currently
unclear. We hypothesize that platelets act on injured glomerular endothelial
cells and podocytes via microvesicles carrying mRNA and miRNA, resulting in
pro-inflammatory and pro-fibrotic phenotype of these cells.

To correlate platelet activity, PMV production and platelet and PMV RNA content
to renal outcomes in diabetic nephropathy and to investigate the interaction
between PMV and glomerular endothelial cells and podocytes.

The design of this study is an observational, case-control study.

Patients visit the outpatient clinic for diabetes regularly, to monitor their
glucose control and health status. Blood and urine are routinely collected to
measure the standard clinical parameters. Patients participating in this study
only need to donate 2 extra vials (total of 18 mL) of blood to perform
additional measurements for the study. The collection if this small amount of
blood has minimal additional risk. The healthy volunteers do not have regular
blood and urine collection, so the burden to participate in this study will be
slightly higher in this group, however, the risk of these procedures is still
minimal.