Role of Bushen Huoxue Formula and transplanted endothelial progenitor cells play in promoting endplate microcirculation and attenuating intervertebral disc degeneration.

Objective: To explore whether Bushen Huoxue Formula (BSHXF) improves the angiogenesis ability of transplanted endothelial progenitor cells (EPCs) in endplate and its potential mechanism in delaying intervertebral disc degeneration (IDD).

Methods: BSHXF was analyzed via Ultra-High Performance Liquid Chromatography (UPLC). Rabbit axial compression lumbar IDD models were constructed and the effects of BSHXF, EPCs, and their combination in IDD were determined by MRI, histological evaluation, TUNEL, and immunofluorescence assays. Additionally, CCK-8 assay, flow cytometry, and tube formation assay were used to evaluate EPCs viability, proliferation, cell cycle and the angiogenesis ability of EPCs between groups.

Results: BSHXF and transplanted EPCs both attenuate the process of IDD in the rabbit model assessed by MRI, HE staining and Masson staining. TUNEL-positive NP cells were significantly reduced in the BSHXF group, EPCs group, and EPC + BSHXF group compared to the model group (P < 0.05), with the EPC + BSHXF group showing the most significant therapeutic effect. Immunofluorescence detection showed that VEGF, CD34 expression and quantity of microvessels in the endplate significantly increased in the EPC + BSHXF group compared to all the other groups (P < 0.05). Besides, the CCK-8 assay showed an upregulation of EPC viability and the tube formation assay demonstrated a significant increase in tube length and branching in EPCs cultured with BSHXF-containing serum (P < 0.05). Furthermore, BSHXF-containing serum increased VEGF expression in EPCs cultured in vitro (P < 0.05).

Conclusions: Both BSHXF and EPCs transplantation play an important role in increasing endplate angiogenesis and attenuating IDD. BSHXF can enhance the viability and tube-forming ability of EPCs and endplate microcirculation.