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PEXT™

Science & characterization

The layer most suppliers will not show you.

Source-cell identity, functional potency data, the lot-release specification and the literature the selection method rests on.
Scientific directionProf. Dr. H. Eray Copcu, MD·Plastic, Reconstructive and Aesthetic Surgery · Regenerative Medicine

This page was reviewed by the Scientific Director on 16 August 2026.

Source-cell identity

The source population meets the ISCT minimal MSC criteria

The International Society for Cellular Therapy defines minimal MSC criteria: plastic adherence, expression of CD105, CD73 and CD90, absence of haematopoietic markers, and trilineage differentiation capacity. Surface marker expression is characterized by flow cytometry.
Surface marker panel by flow cytometry. Grey traces are the isotype controls.Fig. 01
Positive · expression required
CD73100.0%CD9097.7%CD105100.0%
Negative · expression must be absent
CD11b0.14%CD190.13%CD340.067%CD450.42%HLA-DR1.55%

Identity is the first thing a batch record should establish, and the easiest thing to omit. A preparation whose producer cells were never confirmed as MSCs cannot be described as MSC-derived.

Method

How the glutathione reading is actually taken

Every parameter on this site is derived from one measurement: the FreSHtracer Ratio. FreSHtracer is a reversible fluorescent dye that binds glutathione in living cells and shifts its emission when it does.
The dye chemistry, the ratiometric readout and real-time monitoring in living cells.Fig. 02
Ratiometric, not absolute
Bound and unbound dye emit at different wavelengths. The ratio between them tracks glutathione concentration, so the reading does not depend on how much dye entered a given cell.
Living cells, in real time
The dye is reversible, so the same cells can be followed through an oxidant challenge and back. That is what makes GRC measurable at all.
Per cell, not per sample
Because the readout is per cell, a population can be described by its distribution rather than a single averaged number. GH, GRC and ORC all depend on that.

FreSHtracer™ is described in the peer-reviewed literature listed below.

Functional potency

Biological activity has to be measured, not inferred

Proteomic and particle characterization describe what is present. Potency assays ask whether it does anything. Both are required, and neither substitutes for the other.
  • Whitening
  • Wound-healing assay
  • Collagen synthesis
  • Immunosuppression assay
Collagen synthesis and secretion in human dermal fibroblasts, PEXT versus untreated control.Fig. 03
Inhibitory effect on activated T-cell proliferation, compared across conditioned media sources.Fig. 04

Assay data shown are development-stage comparative evaluations. They describe biological activity under the stated conditions and are not clinical efficacy claims.

Level 05Release · Batch Passport

The lot-release specification, in full

MISEV2023 and the MFDS extracellular-vesicle guidance both assess quality through the same five layers, so the record is organized the same way.

Starting material

The source-cell population, before production

GM · glutathione mean level
FreSHtracer ratio, mean or median
GH · glutathione heterogeneity
Robust coefficient of variation
GRC · glutathione regeneration capacity
AUC oxidant ÷ AUC non-treated
ORC · oxidative stress resistant capacity
GSH-high cells ÷ total cells
MSC identity panel
CD73, CD90, CD105 positive; CD11b, CD19, CD34, CD45, HLA-DR negative

Process

How the preparation was made

Culture composition
Phenol red-free, animal component-free
Passage number at harvest
Per specification
Isolation route
Clarification → filtration → concentration → purification

Characterization

What is actually in the vial

Particle concentration
Nanoparticle tracking analysis
Size distribution
Nanoparticle tracking analysis
Morphology
Electron microscopy
Positive EV marker panel
e.g. CD9, CD63, CD81, TSG101, ALIX
Negative marker panel
Non-vesicular and cellular contaminant markers
Purity
Particle-to-protein ratio
Non-vesicular contaminant analysis
Per specification
Residual DNA
Per specification
Residual protein
Per specification

Safety

Release testing

Sterility
Per specification
Endotoxin
Per specification
Mycoplasma
Per specification

Function

Whether it does anything

Functional potency assay
Product-specific, validated method

Stability

Whether it survives the process

Residual moisture
Post-lyophilization
Reconstitution time
Defined solvent and volume
Particle recovery before vs after lyophilization
Paired comparison
Biological function before vs after lyophilization
Paired comparison

Measured values, acceptance criteria and lot-release results are issued with each batch and available to professionals on request.

Request a batch record

Nomenclature

Why this site says “extracellular vesicles” more often than “exosomes”

Precision about naming is the first quality signal a platform can give you.

Extracellular vesicles are lipid-bilayer particles naturally released by cells. They carry combinations of proteins, lipids, metabolites and nucleic acids that can participate in communication between cells.

Exosomes are a specific subtype of EV, formed through the endosomal pathway inside the producing cell. Because the precise intracellular origin of every isolated vesicle cannot always be demonstrated in a finished preparation, the MISEV2023 guidelines recommend the broader terms extracellular vesicles or small extracellular vesicles unless exosomal biogenesis has been specifically established.

Why this matters here

This distinction is not a weakness. A supplier who uses the word “exosome” for everything is telling you they have not done the characterization that would let them be more careful.

CD9CD63CD81SMALL EV · 30–150 nm

Extracellular vesicle (EV)

The general term: any lipid-bilayer particle released by a cell. Correct by default.

Small EV (sEV)

An EV within a defined small size range. A size statement, not an origin statement.

Exosome

An EV specifically formed through the endosomal pathway. Only usable when biogenesis has been demonstrated.

Literature

The published basis for glutathione-based source-cell selection

FreSHtracer and the parameters derived from it are described in the peer-reviewed literature. This list covers the method, its standard operating procedure, and applications across stem-cell biology.
  1. 01

    FreSHtracer technology

    Real-time monitoring of glutathione in living cells reveals that high glutathione levels are required to maintain stem cell function

    E.M. Jeong et al. · Stem Cell Reports (2018) 10, 600–614

  2. 02

    FreSHtracer SOP

    Monitoring glutathione dynamics and heterogeneity in living stem cells

    E.M. Jeong et al. · Int J Stem Cells (2019) 12(2), 367–379

  3. 03

    GRC measurement

    Measuring glutathione regeneration capacity in stem cells

    J. Kim et al. · Int J Stem Cells (2023) June 30

  4. 04

    Senescent cells

    Antioxidants reduce the heterogeneity of the intracellular glutathione level in senescent cell population of human dermal fibroblasts

    K.B. Lee et al. · J Dermatol Sci (2020) 98(3), 195–198

  5. 05

    Graft-versus-host disease

    Glutathione dynamics determine the therapeutic efficacy of mesenchymal stem cells for graft-versus-host disease via the CREB1–NRF2 pathway

    Lim et al. · Science Advances (2020) 6

  6. 06

    Haematopoietic stem cells

    3,2′-Dihydroxyflavone improves the proliferation and survival of human pluripotent stem cells and their differentiation into haematopoietic progenitor cells

    K. Kim et al. · J Clin Med (2020) 9, 669

  7. 07

    Induced pluripotent stem cells

    Improved isolation and culture of urine-derived stem cells (USCs) and enhanced production of immune cells from USC-derived induced pluripotent stem cells

    K. Kim et al. · J Clin Med (2020) 9, 827

  8. 08

    Astrocytes

    Cografting astrocytes improves cell therapeutic outcomes in a Parkinson's disease model

    J. Song et al. · JCI (2018) 128(1), 463–482

  9. 09

    Chronic inflammatory disease

    Mesenchymal stem cells exert their anti-asthmatic effects through macrophage modulation in a murine chronic asthma model

    R. Kim et al. · Sci Rep (2022) 13 Jun; 12(1):9811

  10. 10

    Asthma

    Intratracheal administration of mesenchymal stem cells modulates lung macrophage polarization and exerts anti-asthmatic effects

    Y. Mo et al. · Sci Rep (2022) 11 Jul; 12(1):11728

  11. 11

    Pulmonary inflammatory disease

    Activating transcription factor-2 supports the antioxidant capacity and ability of human mesenchymal stem cells to prevent asthmatic airway inflammation

    H. Ju et al. · Experimental & Molecular Medicine (2023) 10 Feb

  12. 12

    Degenerative arthritis

    High-glutathione mesenchymal stem cells isolated using the FreSHtracer probe enhance cartilage regeneration in a rabbit chondral defect model

    G. Cho et al.

  13. 13

    Anti-cancer drug response

    Glutathione dynamics is a potential predictive and therapeutic trait for neoadjuvant chemotherapy response in bladder cancer

    Kim et al. · Cell Rep Med (2023) 27 Sep: 101224

  14. 14

    Mechanism of action

    Transglutaminase 2 prevents premature senescence and promotes osteoblastic differentiation of mesenchymal stem cells through NRF2 activation

    Lee et al. · Stem Cells International (2023)

These publications describe the measurement technology and the biology of glutathione in stem cells. They are not clinical studies of PEXT, and they do not establish PEXT as a validated medical treatment.

The wider field

Where extracellular-vesicle research is going

Registered clinical studies are examining MSC-derived EVs and exosome-associated preparations across a growing range of research areas.
  • Topical MSC-exosome ointment in psoriasis
  • MSC-derived EVs in dystrophic epidermolysis bullosa
  • Adipose-derived EV preparations in wound healing
  • Small EVs in knee osteoarthritis
  • Nebulized MSC-derived EVs in respiratory conditions

Read this carefully

The existence of a registered clinical study does not establish that an intervention is safe, effective, approved or suitable for general clinical use. This section describes the development of the wider EV field. It must not be interpreted as evidence that PEXT has been clinically validated for these conditions.

Beyond naturally produced vesicles, researchers are developing engineered EV systems carrying defined RNA molecules, proteins and gene-editing components, with investigational programmes exploring delivery to difficult-to-reach tissues.

Those possibilities are the future direction of the field. On this site they are research context, not claims for the currently marketed product.