Role of cell-free mitochondria in breast milk to support neonatal metabolism

Breastmilk evolved over millions of years and has a fine-tuned composition that optimizes neonatal growth, development, and survival in diverse mammalian species. Breastmilk alternatives, such as infant formulas, are empowering, safe, and effective nutrient source for offspring. However, exclusive formula feeding is associated with an increased risk of developing many different metabolic, immunologic, and neurologic diseases in the offspring later in life, possibly due to missing components such as extracellular vesicles (EVs) that are normally found in breastmilk. Therefore, identifying novel components in breastmilk will increase our understanding of how breastmilk contributes to neonatal and infant health and may lead to strategies to improve the composition of formula. In my new preliminary studies, I found that murine breastmilk contains large quantalities of cell-free mitochondria that are predominantly derived from CX3CR1-postive macrophages in the lactating mammary gland. These cell-free mitochondria can be transported into some of the neonatal cells in the intestines during nursing. Moreover, prolonged breastfeeding or administering milk to Ndufs4–/– mice, a mouse model develops a mitochondrial disease called Leigh Syndrome (LS) after weaning, markedly reduced their disease severity and improved their survival. These findings provoke my central hypothesis that maternal cell-free mitochondria are released into breastmilk to deliver the full complement of mitochondria- associated nutrients and to support mitochondria metabolism in the offspring. I will test this hypothesis in two aims. In Aim 1, I will determine how cell-free mitochondria contribute to the nutrient composition of breastmilk. In Aim 2, I will establish how cell-free mitochondria in breastmilk contribute to normal development and limit the progression of LS in the offspring. This proposal is highly innovative because it will (1) identify cell- free mitochondria as a previously unknown breastmilk component that shapes the milk’s nutrient composition, (2) define the function of breastfeeding-associated mitochondria transfer in supporting neonatal metabolism, and (3) establish extended breastfeeding or mitochondria-supplemented formula as novel therapies for inherited mitochondrial diseases. These studies will increase our understanding of lactation physiology, the mechanisms of how breastmilk contribute to the growth and development of offspring, and provide novel insights on improving the composition of infant formula. I will complete the mentored phase (K99) of this project by leveraging the intellectual and scientific resources of Dr. Jonathan R. Brestoff’s Lab (one of the world’s leading labs studying mitochondria transfer and cell-free mitochondria), with co-mentorship by Dr. David Pagliarini (a prominent mitochondrial biologist) and an exceptional set of scientific and career advisors and collaborators. This project will allow me to transition to independence (R00 phase) to launch my career at a leading academic medical center in the United States. Project Number: 1K99HD118086-01A1 | Fiscal Year: 2026 | NIH Institute/Center: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) | Principal Investigator: Wentong Jia | Institution: WASHINGTON UNIVERSITY, SAINT LOUIS, MO | Award Amount: $119,544 | Activity Code: K99 | Study Section: Special Emphasis Panel[ZRG1 EMS-Q (90)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11302503