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Heterochronic Exchange and Young Plasma

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# Heterochronic Exchange and Young Plasma

Portal: Longevity Science
Stage: Preclinical, early human pilots
Evidence: Preclinical
Template: Intervention
Risk: Moderate
Reversibility: Reversible
Last reviewed: May 2026

== Summary ==
Sharing a young circulatory environment rejuvenates some tissues in animals, but the human versions — young plasma or plasma dilution — remain unproven and easy to oversell.

== Key takeaways ==
* Joining young and old circulations improves some repair signals in mice.
* The active question is whether dilution of old factors, not addition of young ones, drives the effect.
* Commercial young-plasma infusions run far ahead of any human evidence.

== Mechanism ==
In heterochronic parabiosis, an old animal shares a bloodstream with a young one, and several old tissues show improved regeneration. The effect is often attributed to a shift in circulating signals rather than to any single youth factor.

More recent work suggests that simply diluting age-elevated factors — for example by exchanging plasma for a neutral solution — reproduces part of the benefit, reframing the mechanism from adding youth to removing accumulated signals.

== Human translation ==
Human evidence is thin. Small studies of plasma exchange in aging and disease are early and mixed, and no regimen has shown durable healthspan benefit.

Meanwhile, clinics have marketed young-plasma infusions directly to consumers, drawing regulatory warnings. The honest status is a provocative animal result whose human form is unestablished.

== Open questions ==
* Is the benefit from removing old factors or adding young ones?
* Can any human regimen show a functional, not just biomarker, effect?

== Watchlist ==
* Plasma-dilution trials
* Identified rejuvenating factors
* Regulatory action on plasma clinics

== References ==
* Heterochronic parabiosis — Conboy et al., Nature, 2005. https://pubmed.ncbi.nlm.nih.gov/15716955/. Foundational study showing a young circulation improves old-tissue repair.
* Plasma dilution effect — Mehdipour et al., Aging, 2020. https://pubmed.ncbi.nlm.nih.gov/32474458/. Argues dilution of old factors, not youth factors, drives rejuvenation.

== Categories ==
[[Category:Longevity Science]]
[[Category:parabiosis]]
[[Category:plasma]]
[[Category:rejuvenation]]

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