Harnessing Metabolic Priming to Engineer Human Nucleus Pulposus Macromass Overcoming Scalability-Phenotype Tradeoff

Intervertebral disc degeneration (IDD) represents a major global health challenge, primarily due to the inability of current therapies to reverse the progressive loss of nucleus pulposus (NP) tissue and function. Transplanting bioactive substitutes offers potential for overcoming this limitation. However, current strategies fail to generate large-sized, functional human NP substitutes, impeded by a fundamental trade-off: the incapacity to simultaneously achieve scalable expansion and maintain the essential cellular phenotype. Here, we found that human platelet lysate (hPL) acts not merely as a growth supplement but as a powerful metabolic primer, driving robust proliferation of human NP cells (hNPCs) while remarkably preserving a mature NP phenotype. This was demonstrated through sustained expression of aggrecan (ACAN) and collagen type II (COL2). Crucially, this metabolic shift allowed us to create a high-quality, homogeneous NP macromass exceeding 2 mm in size, which exhibited superior mechanical integrity and successfully avoided the common problem of necrotic core formation. In vivo validation demonstrated significantly larger grafts with markedly enhanced ACAN and COL2 deposition, confirming the functional superiority of the constructs. Mechanistically, transcriptomic analysis revealed that hPL specifically enhanced fatty acid oxidation (FAO), with this energy metabolism shift serving as the primary driver enabling both rapid growth and phenotypic stability. Ultimately, the hPL-primed NP macromass demonstrated exceptional efficacy in repairing degenerated discs in situ. Our work introduces a novel and potent paradigm for IDD treatment by harnessing the principle of metabolic priming to generate scalable and functional NP substitutes, effectively bridging a critical gap in disc regeneration therapy.