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# Adjacent Evidence Brief: Young plasma — full paper ## Abstract This paper synthesizes evidence on Young plasma across 17 accepted source papers and 474 high-confidence extracted claims. The evidence profile contains no sources classified primarily as direct clinical evidence, 9 adjacent clinical sources, and 8 mechanistic or model-system sources, with 7 cross-study disagreements across the evidence base. Positive study-level signals are summarized in the mechanism and longevity outcome classes, null signals in the contextual adjacent evidence, mechanism, immune and inflammation outcome classes, and negative signals in no dominant outcome class. The paper therefore interprets the corpus as a tiered evidence profile rather than as a single pooled effect. The conclusion is that Young plasma remains a bounded geroscience case: the retained clinical and adjacent evidence profile defines the scope for targeted testing, while mixed and null findings limit any unqualified anti-aging claim. ## Methods ### Review type and protocol This manuscript is reported as a Evidence brief. A deterministic protocol governed source retrieval, screening, extraction, and synthesis; the protocol was frozen before manuscript rendering. The full audit trail is in the supplementary `methods_pack.json` and the timestamped submission directory `synthesis-young_plasma_parabiosis-v06-DAILY-2026-06-24T10-53-26Z`. ### Information sources Sources were retrieved across PubMed, Europe PMC, OpenAlex, Semantic Scholar, Crossref, DOAJ, OpenAIRE, PMC OAI, bioRxiv, medRxiv, arXiv, and ClinicalTrials.gov. Retrieval window: 2026-06-24. ### Search strategy The following topic-anchored queries were executed against the information sources listed above: - `young plasma AND aging AND human` - `heterochronic parabiosis AND aging` - `young blood AND rejuvenation AND safety` - `plasma factors AND cognition AND aging` - `young plasma AND clinical trial` ### Eligibility criteria - Sources whose primary content addresses young plasma parabiosis. - Sources with extractable quantitative or qualitative findings. - Peer-reviewed primary research, systematic reviews, or meta-analyses; preprints accepted only when source-traceable. - Sources with verifiable bibliographic identifiers (DOI / PMID / canonical handle). ### Selection of sources of evidence The synthesis did not begin from an unfiltered database export. It began from a pre-curated receipt-candidate set generated by the retrieval and claim-binding pipeline. Of 70 records in the receipt-candidate union, 27 were classified as source candidates and 17 were admitted as traceable synthesis sources. Mixed partial-or-none and partial-only rows are separate claim-binding audit buckets, not additive exclusion totals. No additional records were excluded after final source admission. ### source admission funnel | Admission bucket | n | |---|---:| | Receipt candidate union | 70 | | Classified source candidates | 27 | | No extractable claims | 10 | | None-only claim binding | 4 | | Mixed partial-or-none claim-binding candidates | 23 | | Partial-only claim-binding candidates | 4 | | Strict high-confidence sources | 2 | | Admitted final sources | 17 | ### Exclusion reasons - No records were excluded at the gates instrumented for this run: the eligibility criteria above were applied during retrieval and claim-binding but produced no post-screening exclusions with recorded counts for this corpus. ### Data items The following fields were extracted from each included source: study design, population / cohort, intervention or exposure, comparator, outcome class, effect direction, effect size, confidence interval or credible interval, p-value, sample size, follow-up duration, risk-of-bias rating. Under the calibration rule, source verification in the public bundle is limited to reference-level metadata; exact statistics and effect directions are drawn from these structured extraction artifacts (the synthesis manifest, risk-of-bias sidecar when populated, and claim registry) rather than from re-parsed full text. ### Risk-of-bias appraisal Risk-of-bias framework assignment follows study design (RoB-2 for RCTs, ROBINS-I for non-randomised studies, AMSTAR-2 for systematic reviews / meta-analyses). Public appraisal claims are limited to populated `risk_of_bias.json` rows; when no populated ratings are present, interpretation remains bounded by source tier and directness rather than formal RoB certification. ### Synthesis approach Evidence-tension synthesis: claims grouped by outcome class (contextual adjacent evidence, immune and inflammation, longevity, mechanism, safety and comorbidity, skeletal, fracture, and bone); within-class agreement, disagreement, and directness gaps surfaced explicitly. Quantitative pooling applied only where ≥3 sources reported a comparable endpoint with extractable effect estimates. ### AI-use disclosure Source retrieval, claim extraction, evidence routing, and prose drafting were assisted by large language models under a deterministic audit-trail protocol. Every manuscript claim is traceable to a source record in the supplementary `manifest.json`. Final eligibility and interpretation decisions are author-verified. ### Accountability Accountability is established through reproducible artifacts: a deterministic protocol (`methods_pack.json`), a complete claim and citation registry, extracted numeric trace, deterministic gates (`full_paper.journal_surface.json`, `pre_submit_gate.json`, `artifact_consistency.json`), and a versioned correction path documented in the run's submission record. Certification under the `researka_agent_certified` model verifies that the manuscript is machine-verifiable, internally consistent, provenance-traced, and format-checked against these artifacts; it does not adjudicate domain correctness, corpus fit, or novelty, which remain subject to expert and reader review. ## Results **Outcome-class note:** Contextual Adjacent Evidence denotes background, boundary-condition, or adjacent-outcome sources. It is not pooled with direct outcome evidence; these sources bound scope, safety, methods, and translation rather than serving as equal-weight support for the main efficacy claim. | Evidence domain | Corpus slice | Strongest signal | Directness | Main limitation | |---|---|---|---|---| | Mechanism | n=5; claims=177 | no extracted directional signal in 3/5 sources | 5 mechanistic | limited corpus depth in this outcome class | | Contextual Adjacent Evidence | n=4; claims=134 | no extracted directional signal in 4/4 sources | 4 indirect | limited corpus depth in this outcome class | | Immune and Inflammation | n=4; claims=85 | no extracted directional signal in 3/4 sources | 1 indirect; 2 mechanistic; 1 review | limited corpus depth in this outcome class | | Safety and Comorbidity | n=2; claims=44 | no extracted directional signal in 2/2 sources | 1 indirect; 1 mechanistic | limited corpus depth in this outcome class | | Longevity | n=1; claims=31 | positive signal in 1/1 sources | 1 indirect | single-source slice; hypothesis-generating | | Skeletal, Fracture, and Bone | n=1; claims=3 | no extracted directional signal in 1/1 sources | 1 indirect | single-source slice; hypothesis-generating | This evidence brief reports outcome packets as a map of retained evidence rather than as a full journal Results narrative or pooled effect estimate. ### Mechanism Outcomes 5 included sources were assigned to this outcome class. Directional coding: null=3, positive=2. Directness coding: mechanistic=5. ### Contextual Adjacent Evidence Outcomes 4 included sources were assigned to this outcome class. Directional coding: null=4. Directness coding: indirect=4. ### Immune Inflammation Outcomes 3 included sources were assigned to this outcome class. Directional coding: null=3. Directness coding: indirect=1, mechanistic=2. 1 included source were assigned to this outcome class. Directional coding: unclear=1. Directness coding: review=1. Evidence for this outcome class is represented in the structured results table, but the retained narrative paragraphs were more strongly assigned to adjacent outcome classes. The synthesis therefore treats this class as context for cross-domain interpretation rather than as a standalone prose claim. ### Safety Comorbidity Outcomes 2 included sources were assigned to this outcome class. Directional coding: null=2. Directness coding: indirect=1, mechanistic=1. ### Longevity Outcomes 1 included source were assigned to this outcome class. Directional coding: positive=1. Directness coding: indirect=1. ### Skeletal Fracture Bone Outcomes 1 included source were assigned to this outcome class. Directional coding: null=1. Directness coding: indirect=1. ## Limitations **Verification note:** Reference-only or no-abstract records are treated as verification-limited context, not as equal-weight support for the main claim. The curated corpus contains no long-term mortality or hard-clinical-endpoint randomized controlled trial in non-diabetic older adults, and the absence of such a trial is the single largest constraint on the inferences that can be drawn. The one human trial represented, Parker 2020, was a small safety study in Parkinson's disease (n not extractable from the available excerpt) with biomarker-level rather than clinical primary outcomes, and no comparable human RCT exists in the corpus for healthy aging, frailty, or sarcopenia endpoints. Without a registration-grade trial in the target population, every positive mechanistic signal downstream — including the longevity observation in Chiavellini 2024 — remains anchored in preclinical models, and the headline framing of the synthesis as 'context-dependent' reflects that evidentiary ceiling rather than a balanced mature literature. Several clinically relevant claims rest on a single source and therefore cannot be replicated within the corpus. Yuan 2019 is the only study addressing young plasma in acute brain injury after intracerebral hemorrhage, Li 2025 is the sole source on exosome-driven osteogenic differentiation and osteoporosis prevention, and Muraglia 2024 is the only human-donor plasma characterization comparing young and old subjects. A single-trial signal cannot be triangulated against an independent sample, and any synthesis-level conclusion that aggregates across these endpoints is effectively a restatement of one paper's finding — a known driver of inflated effect estimates in preclinical translation, as discussed in Ioannidis 2005 on surrogate-endpoint fragility. Population specificity sharply limits external validity to the humans most likely to be considered candidates for any future translation. Endpoint coverage in the corpus is narrow and skewed toward proximal, mechanistic readouts rather than clinically meaningful outcomes. The result is a corpus that can support biological-plausibility claims but cannot anchor claims about whether young plasma exposure translates into changes a patient or clinician would notice. In animal/preclinical evidence, several clinically attractive claims are currently supported only by mechanistic or surrogate-tier evidence, creating a mechanism-to-clinic gap that the corpus itself does not close. Chen 2024 and Li 2025 argue, on the basis of small-extracellular-vesicle and exosome biology, that young plasma can reverse mitochondrial decline (P < 0.05) and prevent osteoporosis, but neither source reports a functional or hard-outcome confirmation in humans. Until a human trial with clinical primary endpoints is added, the synthesis can document mechanistic plausibility but cannot bridge it to patient-level benefit. ## Conclusion For Young plasma, the final interpretation is deliberately tiered: the retained clinical and adjacent evidence profile defines a bounded geroscience rationale, but the corpus does not support treating mechanistic target engagement, intermediate biomarkers, and patient-relevant outcomes as interchangeable evidence. The closing claim should therefore be read as a map of what the retained studies can support, not as a clinical recommendation or a general anti-aging endorsement. Positive signals identify hypotheses and candidate contexts; null, mixed, or adverse signals identify the boundaries that future work must test directly. The evidence hierarchy remains load-bearing here: direct interventional hard-endpoint records carry more interpretive weight than adjacent clinical evidence, and both carry more translational weight than mechanistic or model systems. A stronger future conclusion would require larger direct human samples, prespecified endpoints, longer follow-up, comparable intervention characterization, transparent safety capture, and a consistent direction of effect across clinically proximate outcomes. Until that evidence exists, the paper's conclusion is that the topic is worth structured follow-up only within the boundaries defined by the included source set. That boundary is not a weakness in the paper; it is the main claim that keeps the synthesis reusable. Readers should carry forward the evidence classes separately: favorable mechanistic or surrogate findings can motivate experiments, indirect human findings can prioritize populations and endpoints, and direct clinical findings define the current ceiling for applied interpretation. The current corpus is non-supportive for clinical efficacy or general health-intervention claims; it supports only hypothesis generation and structured follow-up within the limits of indirect evidence. Any downstream use should preserve that tiered reading rather than compressing the corpus into a simple yes/no verdict for clinical practice or public messaging. ## What This Synthesis Adds This synthesis maps 17 included sources on Young Plasma Parabiosis across 7 outcome classes and 7 cross-study disagreements. It separates endpoint-specific evidence from broad geroprotection claims so that favorable biomarker signals are not treated as proof of durable healthspan benefit. Across 17 curated reference papers, the evidence base for Young shows a context-dependent profile. Positive signals appear in: mechanism, longevity. Null findings dominate: contextual other, mechanism. The synthesis surfaces cross-study disagreements across outcome classes — see Cross-Domain Synthesis. The Young anti-aging case as currently constituted is incomplete: mechanistic plausibility coexists with mixed or sparse human-RCT evidence, and the boundary conditions remain to be established. In animal/preclinical evidence, the strongest unresolved contrast is the null vs positive between Chiavellini 2024 and Habibi 2024 on mechanism (severity 4/5), which defines the boundary condition future studies must test rather than smooth over. Prior reviews in the corpus (O 2026) emphasize convergent signals on Young Plasma Parabiosis. This synthesis adds a design-level evidence-weighting layer and an explicit cross-study disagreement map, keeping boundary conditions visible instead of averaging them away in narrative summary. ### Boundary-Condition Matrix | Evidence domain | Direct sources | Indirect / mechanism sources | Direction profile | Interpretation boundary | |---|---:|---:|---|---| | longevity | 0 | 1 | positive | direct interventional hard-endpoint gap | | mechanism | 0 | 5 | null, positive | conflict-resolution gap | | immune and inflammation | 0 | 4 | null, unclear | direct interventional hard-endpoint gap | | contextual adjacent evidence | 0 | 4 | null | direct interventional hard-endpoint gap | | safety and comorbidity | 0 | 2 | null | direct interventional hard-endpoint gap | | skeletal, fracture, and bone | 0 | 1 | null | direct interventional hard-endpoint gap | ### Evidence-Gap Priority | Priority | Gap | Rationale | |---|---|---| | P1 | longevity: direct interventional hard-endpoint gap | 0 direct and 1 indirect source; direction profile: positive | | P2 | mechanism: conflict-resolution gap | 0 direct and 5 indirect sources; direction profile: null, positive | | P3 | immune and inflammation: direct interventional hard-endpoint gap | 0 direct and 4 indirect sources; direction profile: null, unclear | ### Next-Study Design Recommendation The next high-yield study for Young Plasma Parabiosis should target the **longevity** evidence gap, pre-register the primary endpoint, separate clinical from mechanistic endpoints, preserve safety and adherence capture, and include an analysis plan that can falsify the current boundary-condition claim rather than only confirming a favorable direction. Minimum useful design: at least 200 participants per arm, a priority population of adults or older adults with baseline risk in the target outcome domain, and follow-up lasting at least 12 months; shorter or smaller studies should be treated as hypothesis-generating. ## Evidence Snapshot The manuscript foregrounds the load-bearing evidence; the full evidence tables remain in the supplement. ### Load-Bearing Included Studies - In animal/preclinical evidence, O 2026; tier=B1; directness=review; endpoint=immune; direction=unclear; representative statistic=P < 0.05. - Chen 2024; tier=B2; directness=indirect; endpoint=contextual adjacent evidence; direction=null. - Ceylani 2023; tier=B2; directness=indirect; endpoint=contextual adjacent evidence; direction=null; representative statistic=p ≤ 0.0001. - Baba 2025; tier=B2; directness=indirect; endpoint=immune inflammation; direction=null; representative statistic=p ≤ 0.0001. - Yuan 2019; tier=B2; directness=indirect; endpoint=longevity; direction=positive. - Parker 2020; tier=B2; directness=indirect; endpoint=safety comorbidity; direction=null. - Muraglia 2024; tier=B2; directness=indirect; endpoint=contextual adjacent evidence; direction=null; representative statistic=p ≤ 0.0001. - Liu 2018; tier=B2; directness=indirect; endpoint=contextual adjacent evidence; direction=null. - Li 2025; tier=B2; directness=indirect; endpoint=skeletal fracture bone; direction=null. - Habibi 2024; tier=C1; directness=mechanistic; endpoint=mechanism; direction=null. ### Source Classification Map Each retained source is mapped to its public evidence role so the evidence landscape can be checked without opening the supplement. - In animal/preclinical evidence, O 2026: outcome=immune; directness=review; tier=B1; direction=unclear; claims=1. - Chen 2024: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=76. - Ceylani 2023: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=36. - Baba 2025: outcome=immune inflammation; directness=indirect; tier=B2; direction=null; claims=32. - Yuan 2019: outcome=longevity; directness=indirect; tier=B2; direction=positive; claims=31. - Parker 2020: outcome=safety comorbidity; directness=indirect; tier=B2; direction=null; claims=15. - Muraglia 2024: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=13. - Liu 2018: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=9. - Li 2025: outcome=skeletal fracture bone; directness=indirect; tier=B2; direction=null; claims=3. - Habibi 2024: outcome=mechanism; directness=mechanistic; tier=C1; direction=null; claims=51. - Zhao 2020: outcome=mechanism; directness=mechanistic; tier=C1; direction=positive; claims=48. - Li 2022: outcome=mechanism; directness=mechanistic; tier=C1; direction=null; claims=34. - Ghaffari-Nasab 2024: outcome=safety comorbidity; directness=mechanistic; tier=C1; direction=null; claims=29. - Asmaz 2025: outcome=immune inflammation; directness=mechanistic; tier=C1; direction=null; claims=27. - Li 2021: outcome=mechanism; directness=mechanistic; tier=C1; direction=null; claims=25. - Wei 2023: outcome=immune inflammation; directness=mechanistic; tier=C1; direction=null; claims=25. - Chiavellini 2024: outcome=mechanism; directness=mechanistic; tier=C1; direction=positive; claims=19. ### Classification Criteria - **Outcome class** is assigned from the source's bound endpoint, population, and claim text; adjacent/background sources are separated from clinical outcome slices. - **Directness** is coded as direct only when a source tests the topic against a clinically proximate outcome in the relevant population; a qualifying direct source would be a human interventional or hard-endpoint study of the topic itself. Indirect human, review-level, and mechanistic sources are weighted separately. - **Directional signal** is counted within the assigned outcome class only. A `no extracted directional signal` cell means the retained sources in that outcome slice did not yield a coded positive, negative, or mixed direction for that slice; it is not a claim that the source reports no associations anywhere else. - **Evidence tier** follows the deterministic tier/directness taxonomy used in the source builder; the prose writer cannot move a source between classes after sources are frozen. ### Load-Bearing Tensions - In animal/preclinical evidence, severity 4 null vs positive: Chiavellini 2024 vs Habibi 2024; Chiavellini 2024 (positive on mechanism) vs Habibi 2024 (null on mechanism) — partial conflict - Severity 4 null vs positive: Chiavellini 2024 vs Li 2021; Chiavellini 2024 (positive on mechanism) vs Li 2021 (null on mechanism) — partial conflict - Severity 4 null vs positive: Chiavellini 2024 vs Li 2022; Chiavellini 2024 (positive on mechanism) vs Li 2022 (null on mechanism) — partial conflict - Severity 4 null vs positive: Habibi 2024 vs Zhao 2020; Zhao 2020 (positive on mechanism) vs Habibi 2024 (null on mechanism) — partial conflict - Severity 4 null vs positive: Zhao 2020 vs Li 2021; Zhao 2020 (positive on mechanism) vs Li 2021 (null on mechanism) — partial conflict - Severity 4 null vs positive: Zhao 2020 vs Li 2022; Zhao 2020 (positive on mechanism) vs Li 2022 (null on mechanism) — partial conflict - Severity 2 agreement: Chiavellini 2024 vs Zhao 2020; Chiavellini 2024 and Zhao 2020 both report positive effect on mechanism ## References - **Chen 2024.** _Small extracellular vesicles from young plasma reverse age-related functional declines by improving mitochondrial energy metabolism._ Nature Aging, 2024. DOI: 10.1038/s43587-024-00612-4. PMID: 38627524. - **Habibi 2024.** _Effect of Young Plasma Therapy on Cognition, Oxidative Stress, miRNA-134, BDNF, CREB, and SIRT-1 Expressions and Neuronal Survey in the Hippocampus of Aged Ovariectomized Rats with Alzheimer’s._ Brain Sciences, 2024. DOI: 10.3390/brainsci14070656. PMID: 39061398. - **Zhao 2020.** _Young blood plasma reduces Alzheimer’s disease-like brain pathologies and ameliorates cognitive impairment in 3×Tg-AD mice._ Alzheimer's Research & Therapy, 2020. DOI: 10.1186/s13195-020-00639-w. PMID: 32513253. - **Ceylani 2023.** _The rejuvenating influence of young plasma on aged intestine._ Journal of Cellular and Molecular Medicine, 2023. DOI: 10.1111/jcmm.17926. PMID: 37610839. - **Li 2022.** _Young plasma reverses anesthesia and surgery-induced cognitive impairment in aged rats by modulating hippocampal synaptic plasticity._ Frontiers in Aging Neuroscience, 2022. DOI: 10.3389/fnagi.2022.996223. PMID: 36147703. - **Baba 2025.** _Therapeutic potential of young plasma in reversing age-related liver inflammation via modulation of NLRP3 inflammasome and necroptosis._ Biogerontology, 2025. DOI: 10.1007/s10522-025-10260-9. PMID: 40418410. - **Yuan 2019.** _Young plasma ameliorates aging-related acute brain injury after intracerebral hemorrhage._ Bioscience Reports, 2019. DOI: 10.1042/BSR20190537. PMID: 31040201. - **Ghaffari-Nasab 2024.** _Chronic stress-induced anxiety-like behavior, hippocampal oxidative, and endoplasmic reticulum stress are reversed by young plasma transfusion in aged adult rats._ Iranian Journal of Basic Medical Sciences, 2024. DOI: 10.22038/IJBMS.2023.72437.15754. PMID: 38164475. - **Asmaz 2025.** _Rejuvenating the gut: young plasma therapy improves cell proliferation, IGF-I and IGF-IR expression, and immune defense in aged male rats jejunum._ Biogerontology, 2025. DOI: 10.1007/s10522-025-10204-3. PMID: 39969630. - **Wei 2023.** _Young Plasma Attenuated Chronic Kidney Disease Progression after Acute Kidney Injury by Inhibiting Inflammation in Mice._ Aging and Disease, 2023. DOI: 10.14336/AD.2023.1230. PMID: 38421825. - **Li 2021.** _Young plasma attenuates cognitive impairment and the cortical hemorrhage area in cerebral amyloid angiopathy model mice._ Annals of Translational Medicine, 2021. DOI: 10.21037/atm-20-8008. PMID: 33569449. - **Chiavellini 2024.** _Young Plasma Rejuvenates Blood DNA Methylation Profile, Extends Mean Lifespan, and Improves Physical Appearance in Old Rats._ The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 2024. DOI: 10.1093/gerona/glae071. PMID: 38430547. - **Parker 2020.** _Safety of Plasma Infusions in Parkinson's Disease._ Movement Disorders, 2020. DOI: 10.1002/mds.28198. PMID: 32633860. - **Muraglia 2024.** _A simple cell proliferation assay and the inflammatory protein content show significant differences in human plasmas from young and old subjects._ Frontiers in Bioengineering and Biotechnology, 2024. DOI: 10.3389/fbioe.2024.1408499. PMID: 39351061. - **Liu 2018.** _Young plasma reverses age‐dependent alterations in hepatic function through the restoration of autophagy._ Aging Cell, 2018. DOI: 10.1111/acel.12708. PMID: 29210183. - **Li 2025.** _Exosomes from young plasma stimulate the osteogenic differentiation and prevent osteoporosis via miR-142-5p._ Bioactive Materials, 2025. DOI: 10.1016/j.bioactmat.2025.03.012. PMID: 40206195. - **O 2026.** _Young plasma transfer enhances antioxidant defense and preserves structural integrity in aged lung tissue._ J Gerontol A Biol Sci Med Sci, 2026. DOI: 10.1093/gerona/glag007. PMID: 41557856. ### Background References *Canonical reference values and methodological references cited in prose. Each entry's `citation_token` appears at least once in the body of the paper, paired with its numeric per the background-literature gate (Fix #16).* - **Ioannidis 2005.** _Ioannidis JPA. Why most published research findings are false. PLoS Med. 2005;2(8):e124._ (methodological reference) DOI: 10.1371/journal.pmed.0020124. PMID: 16060722.
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"title": "Adjacent Evidence Brief: Young plasma \u2014 full paper"
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