Fibrillins, which are extensively O-glucosylated by POGLUT2 and 3, are crucial for development and cardiopulmonary function. Using primary dermal fibroblasts derived from our POGLUT 2 and 3 double knockout mouse model combined with proteomics analyses, we show that loss of O-glucose modifications on fibrillin causes compositional changes in the extracellular environment compared to controls. Notably, a 30-50% reduction in the abundance of FBN1 and 2 was found in media samples whereas an 85% reduction was found in the extracellular matrix. Other proteins in the extracellular matrix also exhibited changes in abundance in the double knockout samples compared to wild type, but it is still unclear if these changes are simply secondary to the significant reduction in fibrillins.