Perlecan modulates VEGF signaling and is essential for vascularization in endochondral bone formation

Abstract

Perlecan (Hspg2) is a heparan sulfate proteoglycan expressed in basement membranes and cartilage. Perlecan deficiency (Hspg2−/−) in mice and humans causes lethal chondrodysplasia, which indicates that perlecan is essential for cartilage development. However, the function of perlecan in endochondral ossification is not clear. Here, we report the critical role of perlecan in VEGF signaling and angiogenesis in growth plate formation. The Hspg2−/− growth plate was significantly wider but shorter due to severely impaired endochondral bone formation. Hypertrophic chondrocytes were differentiated in Hspg2−/− growth plates; however, removal of the hypertrophic matrix and calcified cartilage was inhibited. Although the expression of MMP-13, CTGF, and VEGFA was significantly upregulated in Hspg2−/− growth plates, vascular invasion into the hypertrophic zone was impaired, which resulted in an almost complete lack of bone marrow and trabecular bone. We demonstrated that cartilage perlecan promoted activation of VEGF/VEGFR by binding to the VEGFR of endothelial cells. Expression of the perlecan transgene specific to the cartilage of Hspg2−/− mice rescued their perinatal lethality and growth plate abnormalities, and vascularization into the growth plate was restored, indicating that perlecan in the growth plate, not in endothelial cells, is critical in this process. These results suggest that perlecan in cartilage is required for activating VEGFR signaling of endothelial cells for vascular invasion and for osteoblast migration into the growth plate. Thus, perlecan in cartilage plays a critical role in endochondral bone formation by promoting angiogenesis essential for cartilage matrix remodeling and subsequent endochondral bone formation.

Pannexin 3 and connexin 43 modulate skeletal development through their distinct functions and expression patterns

“…proliferating cells; thrombospondin-2 (Tsp2, also known as THBS2), a marker of periosteum and osteoblasts (Tucker, 1993), and perlecan, which is used to identify cartilage (Arikawa-Hirasawa et al, 1999;Costell et al, 1999;Ishijima et al, 2012). We found that the Ki67 staining increased in the proliferative chondrocyte zone, periosteum, bone collar, and trabecular bone of Panx3 −/− growth plates, compared to their WT counterparts (Fig.…”

Extracellular Matrix Organization, Structure, and Function

“…Perlecan (Pln) is one of the more abundant heparan sulfate proteoglycans and is found in several tissues including in the endochondral barrier in bones [105]; however, it is primarily localized in vascular basement membranes. It has a major role in regulating the development of blood vessels, the heart, cartilage, and the nervous system.…”

Matrilysin/matrix metalloproteinase-7(MMP7) cleavage of perlecan/HSPG2 creates a molecular switch to alter prostate cancer cell behavior

“…Perlecan’s interaction with growth factors and receptors is crucial in both normal development and in disease progression. Perlecan in cartilage modulates vascular endothelial growth factor receptor-2 activity to allow vascular invasion for endochondral bone formation (Ishijima et al, 2012). Meanwhile, perlecan in synovial fluid positively regulates TGF-β signaling to induce osteophyte formation in mouse osteoarthritis models (Kaneko et al, 2013).…”