HSPG2 and myeloid sarcoma: Increased HSPG immunoreactivity localizes with TG2 in RRMS lesions. Compared to low basal levels of Heparan Sulfate Proteoglycans (HSPG) in non-MS control brain tissue, its immunoreactivity was significantly increased (Figure 8J) in blood vessels and perivascular tissue after RRMS (Figure 8E,F) compared to the lesions in PMS (Figure 8H,I).