Chapter 4
A regenerative-medicine product is rarely a single substance. It is usually a combination of living cells, one or more signalling proteins, and a carrier that keeps both at the right place for the right length of time. The goal of the therapy falls into one of three families: replacing lost tissue, promoting the body's own regeneration, or modulating an immune response. A record that describes only the cells says nothing about how long the growth factor persists. A record that describes only the scaffold hides the donor behind it.
WIA-BIO-020 Phase 1 therefore defines five linked envelopes. They are the stem-cell record, the growth-factor descriptor, the scaffold-and-delivery descriptor, the clinical-application descriptor and the quality-test envelope. Together they follow a product from donor tissue to release test to the trial that evaluates it. This chapter walks through each envelope and the biology and regulation behind its fields.
Two design choices run through all five. First, identifiers are pseudonymous and consent-bound. The cell-record identifier is tied to the donor's consent through an attestation chain rather than to a name. Second, every envelope is expected to carry enough process detail (passage number, formulation, release profile) that a receiving site can judge fitness for use without phoning the sender.
The technical core of Phase 1 is a vocabulary of cell types, signalling molecules and delivery systems. Each term carries the numbers that decide whether a preparation is usable. The two sections below cover the cells first, then the signals and carriers that act on them.
Stem-cell records are grouped by source class. The class determines which quality markers matter and which ethical and regulatory questions arise.
| Source class | Origin | Defining features |
|---|---|---|
| ESC (embryonic) | Inner cell mass of the blastocyst, day 5–6 | Pluripotent; expresses OCT4, SOX2, NANOG; telomerase positive; use in cell therapy depends on ethical approval |
| iPSC (induced pluripotent) | Somatic donor cells (fibroblasts, blood cells) reprogrammed with OCT4, SOX2, KLF4 and c-MYC | Patient-specific and autologous; avoids the embryo-source concern; widely used for disease modelling |
| MSC (mesenchymal) | Bone marrow, adipose tissue, umbilical cord, dental pulp | Plastic-adherent; tri-lineage potential; immunomodulatory |
| HSC (hematopoietic) | Bone marrow, peripheral blood, cord blood | CD34⁺, CD133⁺, CD90⁺ and lineage-negative; give rise to myeloid and lymphoid lineages |
| NSC (neural) | Named as a source class in the envelope | Recorded under the same canonical fields |
The canonical fields of the record follow from this biology:
The MSC panel reflects the ISCT 2006 defining criteria: plastic adherence, more than 95% positivity for CD73, CD90 and CD105, less than 2% positivity for the haematopoietic and HLA-DR markers, and the ability to differentiate into bone, fat and cartilage. These criteria matter for the record because "MSC" is an operational label. A culture that fails the marker panel is not an MSC product, whatever the flask was labelled.
For iPSCs the record has to capture how pluripotency was established and verified. Reprogramming efficiency is defined as the fraction of starting cells that become iPSCs. Typical efficiency is 0.01% to 3%, depending on the method. Verification includes karyotype analysis, pluripotency-marker expression above 90%, a teratoma formation assay, demonstrated potential to form all three germ layers, and confirmation of epigenetic reprogramming. Where iPSCs are derived in-house, the scaffold-and-delivery descriptor cross-references the reprogramming-vector envelope. The vector is then traceable alongside the cells it created.
Reprogramming efficiency:
η = (N_iPSC / N_initial) × 100% (typical 0.01% – 3%)
ESC culture conditions (specification example):
Medium: mTeSR1 or E8
Substrate: Matrigel or vitronectin
Temperature: 37°C, 5% CO₂
Passage: every 3–5 days (70–80% confluence)
Markers: OCT4⁺, NANOG⁺, SSEA-4⁺Beyond identity, the MSC entry records functional behaviour that explains many clinical uses. MSCs secrete IL-10, TGF-β and PGE2, suppress T-cell proliferation, and shift macrophage polarisation from M1 toward M2. They show low immunogenicity, with low HLA class I and no HLA class II. These properties are why MSCs are studied for immunomodulation rather than only for tissue replacement. They are also why the potency test attached to an MSC lot must be chosen to match the intended effect.
A growth factor is meaningful only at a defined concentration, in a defined formulation, delivered over a defined time. The descriptor identifies the factor (BMP-2, BMP-7, TGF-beta, VEGF, PDGF, FGF-2, IGF-1, NGF, GDNF, EGF, HGF or SDF-1) and the source. The source may be recombinant (E. coli, yeast or mammalian), native and isolated from platelet-rich plasma, or a cell-free conditioned medium. It also records purity by HPLC, biological activity by the standard activity assay, the formulation (lyophilised, or liquid carrier with its buffer composition, with or without carrier protein), and storage. Storage is typically −20 °C to −80 °C with a documented stability profile. The functional roles and working doses described in the specification are:
| Factor | Function | Target cells | Optimal dose |
|---|---|---|---|
| VEGF | Angiogenesis | Endothelial cells | 10–50 ng/ml |
| FGF-2 | Cell proliferation | Multiple | 5–20 ng/ml |
| TGF-β | ECM production | Fibroblasts | 1–10 ng/ml |
| BMP-2 | Bone formation | Osteoblasts | 50–200 ng/ml |
| PDGF | Wound healing | Fibroblasts | 10–100 ng/ml |
| EGF | Epithelial growth | Keratinocytes | 5–50 ng/ml |
| NGF | Nerve growth | Neurons | 50–200 ng/ml |
The delivery vehicle changes the effective dose as much as the nominal concentration does. A bolus injection is simple and acts immediately, but its decline is exponential and the half-life for most growth factors is only 2 to 24 hours. Scaffold-based delivery replaces that burst with a release curve. Release patterns are classed as immediate (50–80% within 24 hours), sustained (10–20% per week) or controlled (a programmed pattern). Microsphere encapsulation, with spheres of 1 to 200 μm, releases by diffusion through the polymer, by polymer degradation, or by osmotic pressure. The target encapsulation efficiency is above 70%. Gene delivery moves the dosing problem inside the cell. Adenovirus gives high but transient expression, lentivirus gives stable integration, and AAV gives safe long-term expression. The non-viral options are plasmid DNA, mRNA and lipid nanoparticles.
Bolus: C(t) = C₀ × e^(-kt) half-life 2–24 h typical
Scaffold release: M_released(t) = M_total × (1 - e^(-kt))
Encapsulation: E_eff = (M_encapsulated / M_initial) × 100% target > 70%
Combination: Effect_combined > Effect_A + Effect_B (synergy)Combination therapy is the reason the descriptors are separate but linked. VEGF with FGF-2 enhances angiogenesis (a 2–3× increase is reported). BMP-2 with TGF-β3 improves bone formation. NGF with BDNF gives superior neural regeneration. A combination only exceeds the sum of its parts if each factor reaches the tissue in the expected window, which is a property of the carrier.
The scaffold-and-delivery descriptor completes the picture. It names the scaffold of record under the canonical material classification. That classification is catalogued in WIA-BIO-006 tissue-engineering Phase 1 §A.1, and Phase 1 does not duplicate it. It names the delivery vehicle, which is one of an injectable hydrogel, an in-situ-forming gel, a pre-formed scaffold, a microsphere-encapsulated system or a cell-laden bioink. It also records cell density, typically 1e6–1e8 cells/mL for therapeutic injection, with tissue-specific densities defined elsewhere in Phase 1. The release profile is whatever the operator's own pharmacokinetic study established.
This standard contains no market-size figures, and none are asserted here. What can be said from the specification is where interoperable records change the economics and logistics of cell therapy.
The clinical-application descriptor connects a product to the condition it treats and to the evidence being gathered. The indication is identified under WHO ICD-11 and SNOMED-CT, and the descriptor names the target tissue. Its intended-clinical-effect field has three values, matching the three strategies in the Overview: replace lost tissue, promote endogenous regeneration, or immunomodulate.
Established and investigational uses in the specification show the range:
The remaining fields place the application in its trial context. The stage is one of preclinical, phase 1 safety, phase 2 dose-finding-and-efficacy, phase 3 confirmatory, or post-market surveillance. The comparator arm is placebo, standard of care, or no intervention, always with the matching ethics-board approval. Endpoints are divided into primary safety, primary efficacy, secondary endpoints and exploratory biomarkers. The registration envelope carries the trial's identifier in ClinicalTrials.gov, EU CTIS, KR CRIS or WHO ICTRP. A reader can then trace a product record to a registered study and see exactly which question that study asked.
Cell-therapy products are released on tests, not on process alone. The quality-test envelope follows the cross-walk in Phase 4 §A.1 and adds the tests specific to living products. It records the result of each test, so a lot can be released on a documented profile.
| Attribute | What is tested | Methods named in the specification |
|---|---|---|
| Identity | The cells are who they are claimed to be | STR profiling for human cells; immunophenotyping against the marker-panel envelope |
| Purity | Absence of process residues | Residual host protein, DNA, serum and antibiotics |
| Potency | The cells do what the indication needs | Bone: ALP and OCN secretion. Cartilage: GAG production. Cardiac: beating rate and electrophysiology. Neurological: dopaminergic-marker expression for Parkinson's iPSC-derived neurons |
| Tumourigenicity | The product does not form tumours | Soft-agar growth; immunodeficient-mouse xenograft |
| Genetic stability | The genome has not drifted in culture | Whole-genome sequencing or array-CGH, at the operator's release-test cadence |
| Microbiological safety | No contaminating organisms or endotoxin | Sterility per USP <71>; mycoplasma per USP <63>; endotoxin per USP <85> |
Potency is the attribute most often misunderstood. A single viability number does not show that a bone product will form bone. The envelope asks for an indication-specific functional assay so that the release test measures the effect the clinical descriptor claims. Tumourigenicity and genetic stability exist because pluripotent and long-cultured cells can carry hidden risk. The teratoma assay on the iPSC record and the soft-agar and xenograft tests here answer two parts of the same question. Is the product safe to put into a person?
Implementations most often go wrong in the units and the links between envelopes, not in the data structures. Several practical points follow from the specification.
Like every WIA standard, Phase 1 ships with a reference container, a command-line envelope generator and a conformance suite. These let a team exercise the contract with mock data before connecting real systems. Within the 1.x line, implementers may add optional fields but may not remove existing ones.
Several directions are visible in the specification itself. Gene delivery already lists mRNA and lipid nanoparticles next to viral vectors, which points toward therapies in which the product is a transient instruction rather than a living graft. Cell-free conditioned medium already appears as a growth-factor source, which suggests a path in which the signals from MSCs are used without the cells. The iPSC-derived dopaminergic neuron example for Parkinson's disease shows the pattern likely to spread. A reprogrammed line is differentiated toward one tissue and released on a potency assay specific to that tissue. Because the 1.x line allows optional fields and new envelopes, such products can be described without breaking existing records.
Phase 1 treats a regenerative product as a linked set of five records. The stem-cell record fixes the identity, history and safety status of the cells. The growth-factor descriptor and the scaffold-and-delivery descriptor define the signals and the carrier that shape the dose over time. The clinical-application descriptor binds the product to an indication, a trial stage and a registered study. The quality-test envelope shows that identity, purity, potency, tumourigenicity, genetic stability and sterility were established before release. The numbers in these records (the ISCT marker thresholds, the 0.5 EU/mL endotoxin limit, the 1e6–1e8 cells/mL density range, the 70% encapsulation target) are the evidence a receiving site uses to accept or refuse a lot.
What Phase 1 does not do is move any of these records between systems. The next chapter picks up there. It takes the envelopes defined here and exposes them through HTTPS interfaces, so that a clinic, a manufacturer and a registry can create, retrieve and exchange cell-record, descriptor and quality-test data through one defined contract.