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Perlecan

Perlecan, also known as heparan sulfate proteoglycan 2 (HSPG2), is a large multidomain proteoglycan consisting of a ~500 kDa protein core decorated with heparan sulfate (HS) and chondroitin sulfate (CS) glycosaminoglycan (GAG) chains, serving as a key structural and signaling component of basement membranes and other extracellular matrices in various tissues. Encoded by the HSPG2 gene, which spans over 120 kb with 97 exons, perlecan's modular structure comprises five distinct domains: Domain I at the N-terminus features three GAG attachment sites for HS/CS chains that facilitate growth factor binding; Domain II contains low-density lipoprotein receptor-like motifs involved in lipid and signaling molecule interactions; Domain III includes laminin-like globular regions and EGF-like repeats that support cell proliferation; Domain IV consists of immunoglobulin-like repeats aiding matrix assembly and cell adhesion; and Domain V, which can be proteolytically cleaved to form endorepellin, regulates angiogenesis and tissue repair through integrin and receptor interactions. These domains enable perlecan to bind diverse partners, including extracellular matrix proteins like type IV collagen, laminin, nidogen, and fibronectin, as well as growth factors such as fibroblast growth factor 2 (FGF2), vascular endothelial growth factor A (VEGFA), platelet-derived growth factor (PDGF), and bone morphogenetic proteins (BMPs), thereby modulating cell adhesion, migration, and signaling pathways. In physiology, perlecan plays essential roles in embryonic development, including cardiac morphogenesis, bone formation, and neuromuscular junction stabilization, while also contributing to adult tissue homeostasis such as cartilage mechanosensation, vascular integrity, and blood-brain barrier function. Its interactions with integrins (e.g., α2β1), dystroglycan, and acetylcholinesterase support these processes, and tissue-specific variants—such as HS-only forms in endothelial cells or keratan sulfate/HS/CS hybrids in keratinocytes—allow for specialized functions. Pathologically, mutations in HSPG2 cause rare disorders like Schwartz-Jampel syndrome and dyssegmental dysplasia, characterized by skeletal and neuromuscular defects, while dysregulated expression or processing of perlecan contributes to conditions including , , tumor , , and impaired . Fragments like endorepellin exhibit anti-angiogenic properties by disrupting VEGFR2 signaling, highlighting perlecan's dual pro- and anti-repair roles in regeneration and disease progression.

Molecular Structure

Core Protein Domains

Perlecan's core protein is encoded by the HSPG2 gene, located on human chromosome 1p36.1, and comprises 4,391 with a calculated of approximately 468 kDa. The polypeptide backbone exhibits a highly modular organized into five distinct domains (I–V), which reflect its evolutionary origins and structural versatility as a basement membrane component. This domain organization is conserved across vertebrates, underscoring perlecan's fundamental role in assembly. Domain I resides at the and features a unique (sperm protein, enterokinase, agrin) module, spanning about 120 , along with three serine-glycine attachment sites that serve as primary loci for substitution. Domain II follows, encompassing four cysteine-rich repeats homologous to the ligand-binding domains of the receptor, each containing six conserved residues that stabilize the structure through bonds. Domain III consists of three globular laminin-like modules interspersed with epidermal growth factor-like repeats, which support proper folding, secretion, and overall protein stability. Domain IV represents the largest segment, with over 2,000 forming 21 tandem immunoglobulin-like repeats akin to those in neural molecules, providing an extended scaffold for intermolecular interactions. The C-terminal V contains three laminin G-like (LG) modules separated by epidermal growth factor-like segments, including the LG1–LG3 modules that constitute the bioactive endorepellin fragment upon proteolytic processing. This domain organization highlights perlecan's chimeric nature, drawing modular elements from diverse protein families. The modular structure of perlecan is evolutionarily conserved, with the protein exhibiting approximately 87% to its counterpart across the core domains, facilitating comparative studies in mammalian models. Post-translational modifications, including N-linked , occur at specific residues uniquely within Domains III and V, influencing protein maturation and localization. These features ensure perlecan's stability and functionality in diverse tissues.

Glycosaminoglycan Modifications

Perlecan, a modular , undergoes by the attachment of 3-5 () chains, primarily (HS) or (CS)/ (DS), which significantly contribute to its structural diversity and charge properties. These chains are covalently linked via O-glycosidic bonds to specific serine residues in the core protein, with the main attachment sites located in Domain I at Ser65, Ser71, and Ser76. An additional optional site exists in Domain V at Ser3250 or Ser3593, allowing for further customization depending on cellular context. Mutagenesis studies have confirmed that disruption of these serine residues in Domain I abolishes attachment, underscoring their essential role in chain initiation. The chains on perlecan, typically ranging from 70-100 in size, are linear composed of repeating units of (either D-glucuronic acid or L-iduronic acid) and N-acetyl-D-glucosamine, featuring high degrees of sulfation that confer a strong negative charge. In contrast, / chains are less extensively sulfated and consist of linked to N-acetyl-D-galactosamine , resulting in lower and distinct biophysical properties. These compositional differences enable perlecan to adapt its interactions within the , with chains often dominating in vascular contexts and / providing flexibility in other environments. Tissue-specific variations in substitution highlight perlecan's adaptability, with -dominant forms prevalent in endothelial membranes where they support vascular integrity. In most tissues, including connective and epithelial structures, perlecan exists as a bearing both and chains, balancing charge and elasticity. Certain cartilaginous tissues exhibit predominantly -substituted perlecan, enhancing compressive resilience in load-bearing regions. These variations arise from differential expression of biosynthetic enzymes and reflect localized functional demands. The biosynthesis of perlecan's chains begins with the action of xylosyltransferase enzymes, which initiate linkage region formation by transferring a residue to the serine-glycine motifs in Domains I and V. Polymerization follows via the exostosin complex, comprising EXT1 and , which alternately add and (for ) or (for /) units to form the backbone. Subsequent sulfation by specific transferases, such as those introducing 6-O-sulfation on or galactosamine residues, modulates chain charge density, reaching up to -2 negative charges per in highly sulfated variants and influencing perlecan's electrostatic interactions. Recent investigations since 2020 have revealed that / forms of perlecan are particularly enriched in neural tissues, where they bolster stability by enhancing cross-linking and resisting proteolytic degradation during development and repair processes.

Biological Functions

Extracellular Matrix Assembly

Perlecan integrates into basement membranes through and specific interactions with key (ECM) components, including , , and , thereby contributing to the formation of robust filtration barriers in tissues such as the , blood vessels, and . These interactions facilitate the cross-linking of laminin and collagen IV networks, with perlecan's chains and protein domains enabling high-affinity binding to nidogen-1 and the laminin-nidogen , which stabilizes the overall essential for selective permeability and structural integrity. In the of the , for instance, perlecan's incorporation supports the against protein leakage under physiological pressures. In cartilage ECM, perlecan provides mechanical strength and hydration, playing a critical role in supporting organization during skeletogenesis. Localized primarily in the pericellular matrix surrounding , perlecan's chains attract water molecules, enhancing tissue resilience and load-bearing capacity, while its core protein interacts with II and IX fibrils to maintain spatial arrangement of cells in growth plates. This organization is vital for proper , as evidenced by disrupted columnar alignment in developing skeletons lacking perlecan. The essential nature of perlecan in assembly is underscored by the embryonic lethality observed in HSPG2 knockout mice, resulting from disruptions in Reichert's membrane and cartilage anlagen. In these models, failure of Reichert's membrane—a specialized surrounding the —leads to impaired exchange and developmental arrest, while defective cartilage anlagen exhibit reduced fibrillar networks and shortened fibers, highlighting perlecan's role in early matrix stabilization. In adult tissues, perlecan stabilizes fibrillar matrices in structures like walls, preventing rupture under hemodynamic stress. By anchoring collagen IV and networks in vascular s, perlecan reinforces mechanical resistance to pulsatile blood flow; in conditional knockout models, its absence leads to and instability in high-stress regions such as the myocardium and cerebral vessels. The domain IV immunoglobulin repeats of perlecan contribute to this bridging function through binding to nidogens and laminins.

Growth Factor Regulation

Perlecan serves as a critical reservoir for several growth factors, including fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and bone morphogenetic proteins (BMPs), primarily through the heparan sulfate (HS) chains attached to its Domain I. These HS chains sequester the growth factors, shielding them from proteolytic degradation and thereby extending their half-life in the extracellular environment. Specific sulfation patterns within the HS chains further enhance binding affinity, enabling precise modulation of growth factor interactions. By controlling the localized release and presentation of these factors, perlecan facilitates the formation of concentration gradients essential for directing angiogenesis, where sustained VEGF and FGF-2 availability promotes endothelial cell proliferation and vessel sprouting. In Domain III, perlecan directly binds FGF-7 and FGF-18 with high affinity (approximately 60 nM for FGF-7 and 28 nM for FGF-18), facilitating their from producing cells and increasing their bioavailability in the . This supports key developmental processes, such as epithelial-mesenchymal interactions, by enhancing the mitogenic effects of FGF-7 on epithelial cells and FGF-18 on mesenchymal progenitors, thereby coordinating tissue morphogenesis and branching. Through these mechanisms, Domain III contributes to the spatiotemporal regulation of FGF signaling during . The C-terminal fragment of perlecan, known as endorepellin (derived from Domain V), exerts an anti-angiogenic effect by binding to VEGFR2 on endothelial cells, thereby antagonizing VEGF-induced receptor dimerization and activation. This interaction occurs at a distinct site from VEGF binding but effectively competes for VEGFR2 occupancy, leading to receptor internalization and suppression of downstream pro-vascular pathways such as PI3K/Akt. Consequently, endorepellin balances pro-angiogenic signals from VEGF and FGFs, promoting angiostasis and maintaining vascular in physiological contexts. During tissue repair, perlecan establishes gradients that guide migration to injury sites, as demonstrated in models of where Domain I-based hydrogels create heparin-binding growth factor depots to direct chondroprogenitor and recruitment. These gradients mimic native cues, enhancing directed motility and integration into regenerative processes without disrupting overall matrix integrity.

Cell Adhesion and Signaling

Perlecan facilitates primarily through its interactions with receptors, particularly via domains and of its core protein. These domains bind to integrins such as α2β1, αvβ3, and α5β1, enabling direct cell-matrix contacts that are crucial for endothelial and cell functions. In endothelial cells, this binding promotes adhesion, spreading, and activation of kinase (FAK) and extracellular signal-regulated kinase (ERK) pathways, which in turn drive and survival during processes like and vascular remodeling. Similarly, in cells, perlecan-integrin engagement via domains and supports migratory responses and inhibits excessive proliferation by modulating FAK/ERK signaling, contributing to vascular stability. Domain V of perlecan plays a specific role in modulating dystroglycan-mediated signaling within muscle membranes. By to α-dystroglycan, which links to the transmembrane β-dystroglycan, perlecan anchors the to the , ensuring mechanical stability and preventing membrane rupture during . This interaction is essential for maintaining integrity in fibers, where disruptions lead to impaired force transmission and . In neural contexts, perlecan supports integrity through its association with the dystroglycan complex. The linkage between perlecan and β-dystroglycan in astrocytic endfeet and endothelial cells reinforces the vascular , reducing permeability and preventing solute leakage in the under physiological conditions. Additionally, recent evidence highlights perlecan's role in promoting via α2β1 signaling in hippocampal niches, where it enhances neural progenitor proliferation and differentiation to support . Perlecan can also briefly enhance these signals through co-presentation of growth factors like FGF-2 at the cell surface.

Expression and Regulation

Developmental and Tissue-Specific Patterns

Perlecan exhibits dynamic expression patterns during murine embryogenesis, beginning with detection in two-cell embryos and increasing on the external surface of the morula and blastocyst stages. High levels of expression emerge in embryonic basement membranes around embryonic day (E) 10.5, particularly in tissues involved in vasculogenesis, such as the endothelial basement membranes of the heart, pericardium, and major blood vessels, coinciding with the initial assembly of these structures. By E11 to E13, expression peaks in cartilage condensations, especially in precartilaginous mesenchymal regions undergoing endochondral ossification, where it supports skeletogenesis by facilitating matrix assembly and chondrocyte differentiation prior to collagen type II accumulation. This temporal pattern underscores perlecan's role in early vascular integrity and skeletal patterning, with sustained presence in maturing basement membranes of organs like the kidney and lung by E13 to E17.5. In adult tissues, perlecan maintains prominent expression in specialized basement membranes, including those of vascular endothelium, renal glomeruli, and neuromuscular junctions, where it contributes to structural stability and filtration functions. It is particularly elevated in the hypertrophic zone of cartilage growth plates, aiding in biomechanical support and homeostasis, as well as in the microvasculature of the brain, where it modulates blood-brain barrier integrity. Tissue-specific variations are notable: expression remains low or undetectable in hepatocytes of both fetal and adult liver, reflecting minimal contribution to hepatic , whereas it is robustly upregulated in , correlating with high matrix production demands. In gonadal tissues, perlecan localizes to the ovarian stroma and testicular tunica albuginea. Animal models highlight perlecan's essential developmental roles. Complete of the Hspg2 in mice results in embryonic lethality around E10.5, primarily due to severe vascular defects, including pericardial and cephalic hemorrhages from fragile membranes and impaired cardiovascular remodeling. These models confirm perlecan's non-redundant contributions to organ-specific maturation without overlapping regulatory mechanisms.

Molecular Regulation Mechanisms

The promoter region of the human HSPG2 gene, which encodes perlecan, lacks canonical TATA or CAAT boxes but contains multiple GC-rich motifs and binding sites for transcription factors including Sp1, enabling basal and inducible expression in various cell types. These regulatory elements ensure perlecan's role in stabilization in response to environmental cues. Perlecan expression is upregulated by transforming growth factor-β (TGF-β) in fibroblasts through activation of the promoter via the transcription factor NF-1, independent of Smad signaling, leading to increased mRNA and protein levels that contribute to matrix deposition. In contrast, tumor necrosis factor-α (TNF-α), a key , upregulates perlecan expression in human dermal fibroblasts and vascular cells via activation during , highlighting cell-type-specific regulation. Post-transcriptional control of perlecan involves microRNAs. Epigenetic modifications, such as at CpG islands in the HSPG2 promoter, correlate negatively with in various cancers including , where hypermethylation silences transcription and contributes to altered dynamics in tumor microenvironments.

Degradation and Turnover

Enzymatic Processes

Perlecan, a large in the , is subject to through specific enzymatic processes that target its core protein and chains. Proteolytic cleavage occurs primarily within the immunoglobulin repeat region of domain IV, mediated by matrix metalloproteinase-7 (MMP-7), also known as matrilysin. MMP-7 processes perlecan to generate bioactive fragments that influence cellular behavior, such as promoting migration and invasion in cells. Additionally, /Tolloid-like metalloproteases cleave the C-terminal domain V of perlecan to produce endorepellin, a potent angiostatic fragment consisting of laminin-like globular modules LG1-LG3. This cleavage occurs at specific sites within domain V, releasing endorepellin to modulate vascular processes. The (HS) chains attached to domain I of perlecan are degraded by heparanase (HPSE), an endoglycosidase that cleaves internal α-1,4-glycosidic bonds within HS, resulting in shorter chain fragments. This enzymatic action not only reduces the overall length of HS but also facilitates the release of sequestered growth factors, such as fibroblast growth factors, from the matrix reservoir. Complementary to heparanase, extracellular sulfatases SULF1 and SULF2 act as 6-O-endosulfatases, selectively removing 6-O-sulfate groups from HS chains on perlecan. This desulfation alters the negative charge distribution and sulfation patterns of HS, thereby modifying binding affinities for ligands and promoting the dynamic release of bound growth factors while influencing signaling pathways.

Physiological and Pathological Roles

Perlecan's controlled degradation plays a vital role in physiological processes by facilitating (ECM) remodeling. During , enzymatic cleavage of perlecan releases bound growth factors like fibroblast growth factor-2 (FGF-2), which promote , proliferation, and tissue regeneration. Similarly, in , perlecan turnover maintains vascular homeostasis by modulating the of angiogenic factors, ensuring balanced endothelial cell responses without excessive vessel formation. Key enzymes such as matrix metalloproteinases (MMPs) and heparanase contribute to this regulated breakdown, preventing ECM rigidity while supporting dynamic tissue adaptation. In pathological contexts, dysregulated perlecan degradation disrupts tissue integrity and drives disease progression. Excessive cleavage by heparanase liberates sequestered FGF-2 from perlecan's chains, enhancing tumor cell invasion and promoting through heightened angiogenic signaling. Conversely, insufficient turnover results in the accumulation of perlecan fragments, which inhibit apoptosis via pathways like PI3K and amplify signaling (e.g., FGF-2 and VEGF), thereby fostering excessive deposition and . A notable degradation product, endorepellin derived from perlecan's C-terminal Domain V, exerts anti-angiogenic effects by antagonizing VEGFR2 and α2β1 on endothelial cells, thereby inhibiting tumor vascularization and serving as an endogenous suppressor of pathological . Recent research from 2022 highlights the therapeutic potential of perlecan degradation products in neurological repair; specifically, recombinant perlecan Domain V and its LG3 subdomain enhance neuroprotection and in models by modulating VEGF release and signaling through VEGFR2 and pathways, improving functional .

Protein Interactions

Major Binding Partners

Perlecan, a modular , engages with key (ECM) components primarily through its N-terminal domains to stabilize architecture. Domain IV of perlecan binds directly to nidogen-1 and nidogen-2, forming ternary complexes that link the and IV networks in basement membranes. This interaction is mediated by specific sites within domain IV, with comparable affinities for both nidogen isoforms. Additionally, domain IV associates with laminin-1 and laminin-10, often indirectly via nidogen, enhancing network polymerization during ECM assembly. Perlecan's core protein integrates into IV networks, while its (HS) chains contribute to binding IV networks in basement membranes. The HS chains attached to perlecan's domain I serve as binding sites for multiple factors, modulating their localization and activity in tissues. These include fibroblast growth factors (FGF-1, FGF-2, FGF-7, and FGF-18), which bind with high affinity to promote cellular processes like and . (VEGF165) and BB (PDGF-BB) also interact via these HS chains, facilitating vascular development and remodeling. Bone morphogenetic proteins ( and BMP-7) similarly associate with perlecan's HS, influencing osteogenesis and tissue differentiation. Perlecan interacts with various cell surface molecules to mediate adhesion and communication. Its C-terminal LG domains (in domain V) bind α-dystroglycan, a key receptor in muscle and epithelial cells that links the to the . V also engages such as α2β1 and αvβ3, supporting cell- adhesion in vascular and epithelial contexts. Perlecan associates with syndecans, fellow proteoglycans on cell surfaces, potentially through shared -mediated interactions that amplify signaling co-receptors. Furthermore, domain II, rich in LDL receptor-like modules, binds lipids including low-density lipoproteins via O-linked oligosaccharides, influencing in vascular tissues. Recent studies have identified perlecan as a binding partner for the , primarily through its HS chains and LG3 module in domain V, which may facilitate viral attachment and entry into host cells.

Functional Outcomes

Perlecan's interaction with nidogen facilitates the bridging of and networks within membranes, thereby stabilizing these structures and supporting efficient . This bridging role is essential for maintaining the integrity of the (GBM), where nidogen links perlecan-bound to IV, preventing structural defects that could impair the selective permeability required for function. In the GBM, perlecan's chains further contribute to this stabilization by providing electrostatic repulsion that enhances selectivity, ensuring the passage of water and small solutes while retaining proteins. Through its heparan sulfate moieties and core protein domains, perlecan mediates synergistic interactions between fibroblast growth factor-2 (FGF-2) and (VEGF), promoting endothelial cell tube formation . Perlecan binds both growth factors, presenting them to their respective receptors on endothelial cells and amplifying signaling cascades that drive , , and into vascular tubes. This synergy is evident in assays where perlecan enhances VEGF-induced tube-like structures by up to 16% when combined with soluble domain I fragments, underscoring its role in coordinated angiogenic processes. Perlecan engages , particularly via its endorepellin domain V, to induce clustering and formation of that support myotube in . This interaction activates focal adhesion kinase (FAK) and associated proteins within adhesion complexes, transmitting mechanical signals that promote myoblast alignment, , and maturation into contractile myotubes. In muscle cells, perlecan's presence in these complexes facilitates the cytoskeletal reorganization necessary for , as evidenced by impaired myotube formation in perlecan-deficient models. The combinatorial binding of Wnt signaling molecules to perlecan's domain II sequesters and modulates these signals, contributing to precise axonal guidance during neural development. Domain II acts as a for Wnt ligands, regulating their diffusion and presentation to receptors on growing axons, which directs and formation at neuromuscular junctions. This sequestration prevents ectopic signaling while establishing gradients essential for neuronal patterning, as demonstrated in perlecan mutants exhibiting disrupted axonal trajectories and synaptic retraction.

Associations with Diseases

Genetic Disorders

Mutations in the HSPG2 gene, which encodes perlecan, cause two primary autosomal recessive genetic disorders: Schwartz-Jampel syndrome type 1 (SJS1) and dyssegmental dysplasia, Silverman-Handmaker type (DDSH). These disorders result from loss-of-function variants that impair perlecan secretion or lead to its complete absence, disrupting integrity and function in skeletal and neuromuscular tissues. Schwartz-Jampel syndrome type 1 (SJS1) is characterized by partial loss-of-function mutations in HSPG2, often affecting the core protein domains and reducing perlecan secretion into the . For example, the C1532Y in domain III compromises protein processing and leads to diminished perlecan levels in basement membranes. Clinically, SJS1 presents with continuous causing muscle stiffness, chondrodysplasia resulting in skeletal abnormalities such as and joint contractures, and facial dysmorphism including and a mask-like appearance. Onset typically occurs in infancy, with progressive symptoms that do not significantly impact lifespan. Dyssegmental dysplasia, Silverman-Handmaker type (DDSH), arises from null mutations in HSPG2, such as frameshift-causing duplications or truncating variants, resulting in the complete absence of functional perlecan. These biallelic changes prevent protein secretion, leading to severe disruptions in and . DDSH is a lethal neonatal condition featuring profound skeletal dysplasias, including micromelia, anisospondyly, bowed long bones, , and , often resulting in death shortly after birth due to . Rare HSPG2 variants, including compound heterozygous combinations, can produce phenotypes of variable severity between SJS1 and DDSH, with no evidence of sex linkage due to the autosomal recessive inheritance pattern. Diagnosis of these disorders relies on clinical evaluation followed by targeted sequencing or whole-exome sequencing of the HSPG2 gene to identify causative mutations. Both conditions have an estimated prevalence of less than 1 in 1,000,000 individuals.

Cancer

Perlecan exhibits dual roles in cancer progression, acting as a tumor suppressor or promoter depending on the malignancy type, expression level, and proteolytic processing. Its full-length form often promotes tumor growth by sequestering and presenting growth factors like FGF-2 via heparan sulfate (HS) chains, facilitating angiogenesis and invasion, while C-terminal fragments such as endorepellin exert anti-angiogenic effects by antagonizing VEGFR2 and α2β1 integrin signaling in endothelial cells. In and cancers, perlecan functions primarily as a tumor suppressor through endorepellin-mediated mechanisms that inhibit and tumor vascularization. Conditional expression of endorepellin in the tumor vasculature of models attenuates growth, reduces , and decreases hyaluronan deposition, highlighting its role in limiting metastatic potential. In , while full-length perlecan supports progression via the Sonic Hedgehog pathway, its domain V fragment counters this by disrupting endothelial responses to VEGF, thereby suppressing tumor expansion. Conversely, perlecan acts as a tumor promoter in s and hepatomas through HS-FGF2 interactions that enhance and . In s, elevated perlecan expression correlates with reduced relapse-free , as its HS chains potentiate FGF-2 signaling to drive cell proliferation and migratory behavior. Similarly, in hepatomas, perlecan overexpression facilitates FGF-2 delivery and activation, synergizing with VEGF to boost tumor and metastatic spread in models. Perlecan domain V fragments, particularly endorepellin, inhibit VEGF signaling in colon cancer models, suppressing endothelial tube formation and to curtail tumor progression. In sponge assays with colon cells, endorepellin markedly reduced angiogenic responses, demonstrating its potential to limit vascular support for tumor growth. Heparanase-mediated degradation of perlecan further exacerbates malignancy, as enzymatic cleavage releases bound growth factors and correlates with poor across multiple cancers, including increased and reduced patient survival.

Metabolic and Vascular Diseases

In , a major complication of diabetes mellitus, induces the upregulation of perlecan expression in glomerular , promoting excessive accumulation of components in the mesangium and contributing to the thickening of the (GBM). This structural change impairs the filtration barrier, leading to and progressive renal dysfunction. The (HS) chains attached to perlecan are particularly affected, with high glucose levels altering their sulfation patterns and reducing the anionic charge density in the GBM, which further compromises selectivity for macromolecules like . Perlecan's role extends to , where its side chains in the vascular subendothelial matrix interact with (LDL) to inhibit its oxidation, thereby exerting a protective effect against plaque initiation and progression. Experimental evidence from E-deficient (ApoE^{-/-}) mice demonstrates that perlecan deficiency accelerates atherosclerotic lesion formation, underscoring the proteoglycan's contribution to maintaining arterial wall by limiting lipid retention and . These interactions highlight perlecan as a modulator of in the vessel wall, with implications for therapeutic strategies targeting modifications. In cardiovascular diseases, the C-terminal domain V of perlecan is essential for stabilizing vascular integrity through promotion of endothelial , , and assembly via interactions with and growth factors like (VEGF). Reduced perlecan expression or fragmentation has been associated with weakened vessel walls and heightened risk of development, as observed in models of where diminished perlecan correlates with ECM degradation and inflammatory infiltration. Perlecan has been linked to diabetic , where its dysregulation may contribute to .

Neurologic and Musculoskeletal Disorders

Perlecan domain V provides in models of ischemic by activating α5β1 and VEGFR2-FAK signaling pathways, which promote , , and blood- barrier repair, leading to improved neurological outcomes when administered post-. In models, systemic delivery of recombinant domain V 24 hours after reduced infarct volume and enhanced functional recovery through increased VEGF secretion from endothelial cells. Perlecan is also implicated in , where domain V mitigates amyloid-β-induced endothelial cell toxicity and restores angiogenic function, potentially reducing neurovascular dysfunction associated with plaque formation. Recent studies indicate that perlecan domain V inhibits the α2β1 -mediated neurotoxic cascade triggered by amyloid-β, offering a protective mechanism in disease models. Elevated perlecan levels in brain s correlate with increased VEGF expression and vascular leakage, contributing to abnormal and lesion progression. In arteriovenous malformation tissues, perlecan domain V was found to be overexpressed alongside VEGF, suggesting a role in exacerbating pathological vessel permeability. In musculoskeletal disorders, perlecan is upregulated in the synovium during , where it drives chondrogenic differentiation of synovial cells and promotes formation. Synovial perlecan knockout in mouse models of knee significantly reduced size and severity, highlighting its essential role in this pathological process. In , elevated endorepellin—a fragment of perlecan domain V—impairs muscle repair by inhibiting through antagonism of VEGFR2 and α2β1 , leading to capillary endothelial cell and . This anti-angiogenic effect contributes to reduced satellite cell function and overall muscle regeneration capacity in aging . Therapeutic strategies targeting perlecan have shown promise in neurologic and musculoskeletal contexts. Recombinant perlecan domain V has demonstrated neuroprotective and functional restorative effects in preclinical models, with ongoing research exploring its translation to clinical use for post-stroke recovery. For cartilage regeneration, perlecan domain I-conjugated hydrogels enhance bone morphogenetic protein-2 delivery, promoting chondrogenic differentiation and repair in early models. These injectable microgels improved cartilage repair outcomes in murine studies by potentiating signaling and remodeling. Research gaps persist, including limited studies on exogenous perlecan administration in Schwartz-Jampel syndrome and its unexplored potential in models beyond preliminary progenitor maturation enhancements. Perlecan expression during neural supports its foundational role in the , but adult pathologic applications remain underexplored.

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