Buying airway and respiratory tissue: nose, bronchus, bronchiole and alveolus

The short answer: airway tissue tolerates a longer shelf life than any other living tissue on this site. Two suppliers ship ready-to-use human respiratory epithelium at an air–liquid interface, and both state that the tissue survives in culture for months — one says three months or more, the other says several months and up to a year. Every other category on the engineered tissue map hands you a product with a four-day usable window.

The second thing to know: the specification that matters is anatomical region, not “airway”. Nose, trachea, bronchus, bronchiole and alveolus are different tissues with different cell populations, and a bronchiolar model is not a small bronchial model. Ordering the wrong region is the most common and most expensive error in this category, because the tissue will grow perfectly and answer a question you did not ask.

The third thing, and the one that will cost you a study if you ignore it: these tissues are released on QC that finishes after they have already shipped. One supplier publishes the exact timing — barrier-function failures notified by Wednesday 5 p.m., sterility failures within eight days of shipment. You may already be dosing when the failure notice arrives.

What is actually available

Region is the specification. Get it right first.

The airway is not one tissue and the suppliers are unusually explicit about this. Read the two descriptions side by side and the difference is a cell type, not a size.

Upper airway. MucilAir is reconstituted from nasal, tracheal or bronchial cells and is dominated by basal, goblet and ciliated cells. Goblet cells are prominent; mucus is produced and secreted on the apical side by the tissue itself.

Lower airway. SmallAir models the bronchiolar region after the fifth division of the airway. Epithelix states the major difference from the upper airway plainly: club cells are abundant and are quasi-absent in the upper airways, while goblet cells are present but in low proportion. The supplier backs this with a western blot showing CC10 detected in SmallAir and not detected in MucilAir, with Muc5AC highly expressed in MucilAir instead.

That single contrast is the most useful published fact in this category. Club cells are the secretory, xenobiotic-metabolising, progenitor-competent cell of the small airway. If your compound, pathogen or disease mechanism acts on club cells, an upper-airway model does not contain the cell you care about — and it will still produce clean, reproducible, entirely irrelevant data.

Practical rule. Write the anatomical level into the RFQ as a location, not an adjective. “Bronchiolar, distal to the fifth division” is a specification. “Small airway” is a hope, and “lung model” is not a specification at all.

Longevity inverts the usual logistics problem

Most living tissue purchases are governed by a shelf life measured in days. Airway tissue is the exception, and it changes how you should plan the work.

MatTek states that EpiAirway cultures can be continued for three months or more with good retention of normal morphology, on a stated condition: tissues must be fed every other day with 5.0 mL of maintenance medium (AIR-100-MM), with inserts placed atop washers (EPI-WSHR) or culture stands (MEL-STND) in 6-well plates so that the 5.0 mL volume can be used.

Epithelix states that MucilAir sits in a stable homeostatic state for several months — even up to a year — with slow but physiological cell renewal, maintaining functionality and cell population across its life cycle. SmallAir is described the same way, stable for several months once the production cycle terminates. Their maintenance instruction is deliberately undramatic: transfer to fresh medium, put it in the incubator, change medium twice a week, occasionally wash the mucus.

Three consequences follow, and they are worth planning around.

1. Chronic and repeated-exposure designs are available off the shelf. Repeated-dose inhalation toxicology, chronic inflammation, long-run infection and remodelling studies are possible on purchased tissue without a custom programme. Very little else in the living-tissue market supports this.
2. The arrival date stops being a deadline. A three-day shelf life forces your experiment onto the supplier’s calendar. A three-month culture window means you can accept delivery, stabilise the tissue and start when your compound, your instrument and your analyst are all ready.
3. The cost per data point falls with study length, and the labour does not. Feeding every other day for three months is roughly 45 medium changes per plate, plus medium, plus the incubator footprint, plus contamination risk accumulating the whole time. Longevity is a real capability but it is bought with technician hours. Price the hours before you commit to the design.

The caveat that matters. Both suppliers describe longevity under their own protocol with their own maintenance medium. Neither is telling you that the tissue tolerates three months of your compound. Longevity of the untreated model is the ceiling on your study duration, not a prediction about the treated model.

The donor disease panel is the underused feature

Both suppliers produce tissue from diseased donors, and this is where airway models do something that most tissue categories cannot.

Epithelix states MucilAir can be produced from donors who are: healthy non-smoker, healthy smoker, COPD, asthmatic, cystic fibrosis (several mutations available), and allergic rhinitis. SmallAir is likewise available from patients with several pathologies.

MatTek states EpiAirway’s standard donor is a healthy non-smoker, with alternate donors available on request, and specifically names NHBE from asthmatic, COPD and smoker donors. The product page additionally describes a diverse donor inventory of healthy and diseased donors including goblet cell hyperplasia.

This is a disease model you can buy rather than build, and it is the strongest reason to source airway tissue externally rather than culture it. Two things to verify before you rely on it:

• Cystic fibrosis is a mutation-level specification, not a disease-level one. Epithelix states several mutations are available. F508del homozygous, F508del heterozygous and class III gating mutations behave differently under modulators, and “CF tissue” is not a specification. Name the genotype in the RFQ and get it confirmed in writing on the certificate of analysis.
• A disease donor is one person. Epithelix supplies a certificate of analysis with donor information per batch, which is exactly what you need — but a single diseased donor is an n of 1 in the dimension you are studying. If the endpoint is a disease effect, plan multiple donors or a pooled product, and note that Epithelix catalogues MucilAir Pool and SmallAir Pool precisely for this.

Barrier function is the release criterion, and it is published

MatTek publishes an unusually concrete acceptance test for EpiAirway, and you should hold every supplier in this category to the same standard.

End-use testing: transepithelial electrical resistance of each EpiAirway lot is measured using an EVOM2 epithelial voltohmmeter with an Endohm electrode chamber, and a minimum TEER of 300 Ω·cm² is required for QC release.

Epithelix likewise states that barrier function is quantified by TEER and is part of the SmallAir QC, alongside cilia beating frequency, which is measured with their own analysis software.

Two observations.

First, TEER is the correct release metric for this tissue because the assay most people run — permeation, flux, inhaled dose, infection across a barrier — is a barrier assay. A number you can reproduce on your own voltohmmeter on arrival is a genuine acceptance test rather than a certificate. Measure it on day one, on your instrument, before anything is dosed.

Second, 300 Ω·cm² is a floor, not a target. It is the value below which the lot is not shipped. It is not a statement that your tissues will read 300, and it is not comparable across models, electrodes or media without care — TEER is temperature- and medium-sensitive and chamber geometry matters. Record your own baseline and use it as the internal control.

Epithelix adds a functional release measurement most suppliers do not: cilia beating frequency, plus mucociliary clearance measured by tracking particles across the tissue surface. For any mucociliary endpoint — mucolytics, ciliotoxicity, clearance-dependent dosing — that is a more relevant acceptance criterion than resistance.

The post-shipment QC problem

This is the operational fact that separates people who have run these studies from people who are about to.

MatTek publishes its lot-failure policy in full: because QC and sterility testing are done post-shipment, notification is made as soon as possible, and under normal circumstances TEER failures will be notified by Wednesday 5 p.m., and sterility failures within eight days of shipment. If a lot fails, the customer is notified and the tissues are replaced without charge where appropriate.

Read that against the delivery schedule from the same document — shipped every Monday, delivered Tuesday morning in the US — and the sequence is stark:

• Tuesday morning: tissue arrives.
• Tuesday afternoon: recommended use day.
• Wednesday 5 p.m.: the earliest you learn the barrier failed.
• Up to eight days later: the earliest you learn the lot was not sterile.

You can be a week into a three-month chronic study before a sterility failure is reported. The replacement policy protects the cost of the tissue. Nothing protects the cost of the study.

What to actually do about it.

1. Measure TEER yourself on arrival rather than waiting for the notification. You have the supplier’s own release threshold to compare against.
2. Do not dose the same day you receive on a long study if you can avoid it. Longevity is the luxury this category gives you — spend some of it waiting for the QC window to close.
3. Stagger long studies across two lots where the design permits, so a single lot failure does not take the whole experiment.
4. Keep the shipping agarose gel and the lot letter. MatTek assigns a lot number weekly with a letter appended per kit, and states all kits within a lot are identical in cells, medium, handling and culture conditions. That letter is how a claim gets traced.
5. Ask for the sterility result actively at day eight rather than assuming silence means pass.

Shipping: airway ships warm, and that surprises people

MatTek’s EpiAirway specification states shipment at room temperature on medium-supplemented agarose gels, with a shelf life of up to three days at room temperature including transit.

That is a genuine difference from the same supplier’s skin models, which ship refrigerated. It has two practical consequences. A courier delay does not have the same meaning as it would for a cold-chain shipment, and there is no cold pack whose failure you can inspect. The evidence you have is the condition of the gel and the tissue, so inspect and photograph on opening, before anything is moved.

The published delivery pattern is specific: shipment every Monday; delivery Tuesday morning by FedEx priority service in the US; Tuesday to Thursday outside the US depending on location. MatTek further recommends that for best reproducibility tissues be used consistently on the same day — for example Tuesday afternoon, or Wednesday morning after overnight storage at room temperature.

Epithelix states it ships routinely to Europe, America and Asia, and offers to evaluate delivery to a specific location. If you are outside the standard lanes, ask for that evaluation before you design the schedule, not after.

Formats, and the detail that determines your assay

The EpiAirway specification lists the available formats precisely, and format is a harder constraint than most buyers expect:

• 9 mm and 22 mm individual inserts — substrate chemically modified, 0.4 µm pore size
• 12 mm and 6.5 mm Transwell — same substrate and pore size
• 96-well HTS plates — same substrate and pore size
• A standard kit (AIR-100) is 24 tissues, containing tissues, a small amount of culture medium and plasticware

Histology is stated as 3–4 cell layers, pseudostratified, with mucociliary morphology and tissue structure. Note how different that is from reconstructed epidermis, which is a much thicker stratified structure — a pseudostratified airway epithelium is one cell layer deep in the histological sense, and it is the correct architecture rather than a thin one.

Epithelix’s SmallAir and MucilAir are likewise supplied ready to use on inserts, with the supplier handling all production and QC, and explicitly no specialist equipment or cell-culture skill required for maintenance.

The format question to answer before ordering: does your exposure system, Franz cell, permeation device or plate reader accept the insert diameter you are buying? Air–liquid interface exposure hardware is frequently built around one insert size. MatTek notes EpiAirway is available in several formats specifically for physiological exposure systems — which is a hint that the wrong format is a common and avoidable mistake.

Medium composition, and the variants that exist for a reason

MatTek publishes the EpiAirway medium composition, and several of these fields are experiment-critical:

• Base medium: Dulbecco’s Modified Eagle’s Medium
• Growth factors: epidermal growth factor and other proprietary factors
• Serum: none
• Antibiotics: gentamicin at 5 µg/mL — stated as 10 percent of the normal gentamicin level
• Anti-fungal: amphotericin B at 0.25 µg/mL
• pH indicator: phenol red
• Assay medium: AIR-100-ASY. Maintenance medium: AIR-100-MM

And the variants: phenol-red-free, antibiotic-free and anti-fungal-free medium and tissues are available, with the agents removed at least three days prior to shipment.

That three-day removal window is the reason this must be ordered rather than arranged on arrival. You cannot make a tissue antibiotic-free by washing it on the bench — residual antibiotic will confound any microbiology, and any microbiome, infection or bacterial-challenge work needs the antibiotic-free variant ordered upstream. The same logic applies to phenol red for fluorescence and absorbance readouts.

Epithelix supplies dedicated, chemically defined, serum-free media per model — MucilAir Medium, SmallAir Medium, AlveolAir Medium — and states this ensures stable composition batch to batch. Where a supplier sells the matched medium, use it; the longevity claims are made under that medium and not under yours.

Safety and screening, stated plainly

MatTek states EpiAirway cells are screened for HIV, hepatitis B, hepatitis C and mycoplasma, with HIV and hepatitis screening performed by PCR, and adds the sentence every buyer of human primary tissue should read at least once:

no known test method can offer complete assurance that the cells are pathogen free

and directs that these and all human-derived products be handled at BSL-2 or higher per the CDC–NIH guidance. Epithelix states its primary cells are isolated under ethical approval and donor consent, with a certificate of analysis carrying donor information and QC results per batch.

Two procurement consequences. Your institution’s biosafety approval must be in place before the tissue lands, not after, and the ethical-consent documentation is the thing your own ethics or governance office will ask for. Both are ordinary, both are slow, and both are routinely started too late.

Production quality: one supplier is certified against a scheme

Epithelix states that MucilAir has been produced since 2006 and SmallAir since 2017, and that tissue production has been GIVIMP certified since 2023. GIVIMP is the good in vitro method practice guidance, and certification is an external assessment of the production process rather than a self-declaration.

Epithelix also states its models use only low-passage (P1) human primary cells. Passage number is a real specification: airway epithelial cells dedifferentiate with passage, losing ciliated and secretory populations, and a model built from P1 cells is a different product from one built at P4.

For SmallAir, Epithelix additionally claims that using low-passage cells retains native ion channels including CFTR and ENaC, supporting electrophysiology, and native surface receptors including TMPRSS2, ACE2 and FcRn, supporting viral infection work. If you are doing Ussing chamber electrophysiology or receptor-mediated uptake, ask for the passage number of any competing model before assuming equivalence.

What a purchase does not include

• The exposure system. Air–liquid interface exposure hardware, aerosol or vapour generators, and cigarette or e-cigarette smoke exposure rigs are separate capital.
• Medium beyond what is in the kit. The EpiAirway kit contains a small amount of culture medium; a three-month study at 5.0 mL every other day is a large, separate medium line.
• The plasticware for long culture. Washers or culture stands in 6-well plates are required to use the 5.0 mL feeding volume.
• Assay reagents and readouts. TEER instrumentation, cilia beating frequency analysis, mucociliary clearance tracking, histology, ELISAs.
• Analysis services, where the supplier offers them as a separate line — cilia beating frequency analysis and mucociliary clearance analysis are catalogued by Epithelix as services.

Specification checklist for an airway tissue quote

• Anatomical region, stated as a location: nasal, tracheal, bronchial, bronchiolar (distal to the fifth division), or alveolar.
• Donor health status, and for disease donors the specific pathology — and for cystic fibrosis, the specific mutation.
• Single donor or pooled, and if single, whether donor identity is held constant across your whole study.
• Co-culture: fibroblasts, macrophages, or epithelium alone. Both suppliers catalogue these separately.
• Insert format and diameter, checked against your exposure system and plate reader.
• Medium variant: phenol-red-free, antibiotic-free or anti-fungal-free — ordered upstream, since agents are removed at least three days before shipment.
• TEER release criterion, in Ω·cm², and the instrument and chamber used to measure it.
• Cilia beating frequency and mucociliary clearance, if your endpoint depends on them.
• Passage number of the cells used to reconstitute the tissue.
• Certificate of analysis contents, and whether donor information is included.
• Lot number and kit letter, recorded against your experiment.
• Post-shipment QC timing: when a barrier failure is notified, and when a sterility failure is.
• Shipping lane and transit time to your actual address, especially outside the US and Europe.
• Intended culture duration, stated to the supplier, so the maintenance protocol and medium volume are quoted against your real design.

Where to go next

• Engineered tissue map — why epithelial tissue ships as a finished good when contractile tissue does not.
• Production calendars and shelf life — the scheduling mechanics that govern every living-tissue purchase, and the post-shipment QC problem in general form.
• Intestinal and gut tissue models — the other barrier-tissue category, where the geometry decision is sharper.
• 3D tissue model suppliers compared — airway alongside skin, liver, gut and organ-chip products.
• Shipping live cells and tissue — formats, failure modes and what to inspect on arrival.

How we can help

The failure mode in this category is buying the right supplier and the wrong region — a clean bronchial model for a bronchiolar question — and discovering it after the data are in. The second failure mode is the antibiotic-free variant that had to be ordered three days upstream and was not.

We map the biological question onto the anatomical level first, confirm the donor pathology and, for cystic fibrosis, the specific mutation is actually available in the production window you need, check the insert format against the exposure hardware you already own, and get the post-shipment QC timing stated in writing so your dosing schedule is not sitting inside the notification gap.

Tell us the anatomical level, the donor phenotype, the endpoint and how long the study runs.