A Normative Study of the Synovial Fluid Proteome from Healthy Porcine Knee Joints

Synovial
fluid in an articulating joint contains proteins derived from the
blood plasma
and proteins that are produced by cells within the joint tissues,
such as synovium, cartilage, ligament, and meniscus. The proteome
composition of healthy synovial fluid and the cellular origins of
many synovial fluid components are not fully understood. Here, we
present a normative proteomics study using porcine synovial fluid.
Using our optimized method, we identified 267 proteins with high confidence
in healthy synovial fluid. We also evaluated mRNA expression data
from tissues that can contribute to the synovial fluid proteome, including
synovium, cartilage, blood, and liver, to better estimate the relative
contributions from these sources to specific synovial fluid components.
We identified 113 proteins in healthy synovial fluid that appear to
be primarily derived from plasma transudates, 37 proteins primarily
derived from synovium, and 11 proteins primarily derived from cartilage.
Finally, we compared the identified synovial fluid proteome to the
proteome of human plasma, and we found that the two body fluids share
many similarities, underlining the detected plasma derived nature
of many synovial fluid components. Knowing the synovial fluid proteome
of a healthy joint will help to identify mechanisms that cause joint
disease and pathways involved in disease progression.