PDGF-AA: The "Mesenchymal Cell Regulatory Core" that drives tissue repair in PRP

I. Introduction: The Role of PDGF-AA in the PRP Growth Factor Network

Platelet-Rich Plasma (PRP) is isolated from autologous blood via centrifugation, with its core biological activity derived from growth factors released by platelet α-granules. Based on leukocyte and fibrin content, PRP formulations are categorized into three types: leukocyte-rich PRP (L-PRP), leukocyte-poor PRP (P-PRP, also called pure PRP), and leukocyte-platelet-rich fibrin. Within PRP’s growth factor network, the Platelet-Derived Growth Factor (PDGF) family is critical for mediating tissue repair, consisting of five dimeric subtypes including PDGF-AA and PDGF-BB. Among these, PDGF-AA (a homodimer composed of two A subunits) stands out as a core functional molecule in PRP for promoting wound healing and tissue regeneration, owing to its precise regulatory effects on mesenchymal cells (e.g., fibroblasts, mesenchymal stem cells). Its receptor-binding properties and biological functions directly determine PRP’s repair efficiency.

II. Molecular Characteristics and Expression Distribution of PDGF-AA

(I) Molecular Structure and Receptor Specificity

(II) Tissue and Cellular Expression Patterns

Embryonic stage: Secreted by epithelial cells (alveolar and gastrointestinal epithelium) and vascular smooth muscle precursor cells, participating in the development of the lungs and cardiovascular system;

Adult stage: Highly expressed in alveolar epithelium (lungs), placental trophoblasts, and prostatic glandular epithelium to maintain organ homeostasis; low-level secretion by dermal fibroblasts and bone marrow stromal cells supports tissue repair;

In PRP: Primarily stored in platelet α-granules, released upon activation by endogenous thrombin post-injection, serving as a core signaling source in the local repair microenvironment.

III. Core Biological Functions of PDGF-AA

(I) Regulating Mesenchymal Cell Proliferation and Chemotaxis

(II) Maintaining Organ Development and Homeostasis

Pulmonary function: Induces mesenchymal cell differentiation into alveolar smooth muscle cells during embryogenesis to maintain alveolar expansion; repairs alveolar damage in adulthood, slowing the pathological progression of chronic obstructive pulmonary disease (COPD);

Gastrointestinal homeostasis: Promotes collagen synthesis by intestinal mesenchymal fibroblasts to support epithelial cells and regulate the intestinal stem cell microenvironment;

Spermatogenesis: Stimulates the proliferation of testicular Leydig cells and testosterone synthesis, providing a hormonal environment for sperm maturation.

(III) Mediating Injury Repair and Regeneration

Inflammatory phase: Activates macrophages to phagocytose necrotic tissue and secrete inflammatory factors, amplifying repair signals;

Proliferative phase: Recruits fibroblasts to synthesize extracellular matrix (ECM), supports angiogenesis, and forms granulation tissue;

Remodeling phase: Induces fibroblast differentiation into myofibroblasts, regulates ECM remodeling, and reduces scarring. Preclinical studies show that PRP with high PDGF-AA concentration shortens mouse skin wound healing time by 30% and increases the tensile strength of healed skin by 25%.

IV. Abnormal PDGF-AA Expression and Associated Diseases

Tumors: In cholangiocarcinoma and head and neck squamous cell carcinoma (HNSCC), cancer cells overexpress PDGF-AA, promoting tumor stroma formation and vascular maturation, enhancing invasiveness, and reducing chemotherapy sensitivity;

Fibrosis: Post-lung injury, alveolar epithelial cells overproduce PDGF-AA, activating fibroblasts and leading to alveolar fibrosis; during renal ischemia, renal tubular epithelial cells secrete PDGF-AA, accelerating renal interstitial fibrosis;

Developmental defects: Mice with PDGF-A gene knockout (unable to synthesize PDGF-AA) exhibit defects in alveolar smooth muscle and testicular Leydig cells, mostly dying in the embryonic stage or within 60 days after birth.

V. Application and Outlook of PDGF-AA in PRP

Chronic wounds: Compensates for insufficient endogenous growth factors in patients with diabetic foot ulcers or pressure sores, accelerating healing;

Orthopedic repair: Promotes the proliferation of osteoprogenitor cells and migration of tendon cells, aiding bone transplantation and tendon repair;

Soft tissue regeneration: Drives skin collagen synthesis and oral mucosal renewal, improving repair quality.

VI. Conclusion