Autologous bone marrow mesenchymal stem cell mitochondrial transplantation in recurrent assisted reproductive technology failure: a randomized controlled trial

Abstract

Background: Mitochondrial dysfunction contributes to poor embryo quality and recurrent assisted reproductive technology (ART) failure. Mitochondrial transplantation (MIT), which involves supplementing oocytes with exogenous mitochondria, has been proposed as a novel strategy to improve ART outcomes. However, both its clinical efficacy and safety remain unclear. Methods: In this single-center trial, 151 patients with a history of ≥2 failed ART cycles provided 1178 metaphase II (MII) oocytes. Sibling oocytes were randomized 1:1 to receive autologous bone marrow mesenchymal stem cells (BMSCs) mitochondria co-injection during intracytoplasmic sperm injection (ICSI) or standard ICSI. The primary outcome was the rate of day-3 good-quality embryos. Results: MIT significantly accelerated early embryonic cleavage at the 3-cell stage and 5-cell stage, but this morphokinetic alteration did not translate into improvements in good-quality embryo rate, clinical pregnancy rate, or live birth rate. Long-term follow-up of 23 live births revealed no adverse effects, with all offspring exhibiting normal growth and development. Exploratory analysis revealed that oocytes yielding ≥70% transferable embryos after MIT harbored an elevated higher burden of medium frequency (0.05–0.5) mtDNA point mutations. Conclusions: While autologous BMSCs-MIT transiently alters early cleavage kinetics, it does not demonstrate a clinical advantage in unselected patients with recurrent ART failure. Nevertheless, its observed safety profile and the identification of mtDNA mutation burden as a potential predictive biomarker provide a foundation for shifting future MIT research from a universal approach toward precision application in molecularly stratified populations.

1. Introduction

Embryo competence is critically dependent on mitochondrial function within the oocyte [1, 2]. Mitochondrial DNA (mtDNA) copy number, structural integrity, and respiratory efficiency govern ATP production, consequently exerting profound regulation on early embryonic development [3]. The growing trend toward delayed childbearing has exacerbated mitochondrial dysfunction related infertility, contributing to the persistent challenge of poor quality embryos and recurrent failure of assisted reproductive technology (ART) among affected patients [4]. Therapeutic options for this population remain limited.

Mitochondrial transplantation (MIT) has emerged as a putative rescue strategy, whereby healthy organelles are microinjected into metaphase II oocytes to restore bioenergetic homeostasis [5, 6]. Yet clinical studies using autologous granulosa-cell or oogonial-stem-cell mitochondria have consistently yielded suboptimal outcomes, primarily due to the synchronous aging of donor mitochondria with host oocytes, compounded by unresolved questions regarding stem cell lineage specification and functional potency [7–9]. Attempts with allogeneic mesenchymal-stem-cell mitochondria improve oocyte function in animals but raise immunologic and regulatory concerns in humans [10–12]. Autologous bone marrow mesenchymal stem cells (BMSCs) offer a theoretically optimal mitochondrial source. These cells exhibit negligible immunogenicity and are readily harvested under local anesthesia [13]. Whether BMSC-derived mitochondria can effectively ameliorate oocyte energetic deficits, and which patient subpopulations would derive the greatest clinical benefit from this intervention, have not been established.