Reconstruction of Full Thickness Skin Equivalents using BRANDplates® Insert System

By: Lena Schober and Andrea Traube
Fraunhofer Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA, Nobelstraße 12, 70569 Stuttgart, Germany

Introduction

In the past decade new cell and tissue culture technologies have been generated to follow the European legislative that restricts animal experiments to a minimum. Particularly, the improvement of culture conditions for reconstructed human full thickness skin and epidermis equivalents based on cell culture inserts, lead to a successful commercialization of these tissue models , e.g. EpiDerm™ and EpiDerm™ (FT MatTek, Ashland, MA), EpiSkin™ and EpiSkin™ FTM (SkinEthic, Lyon, France) or Phenion FT (Henkel, Düsseldorf, Germany). Today, with the help of artificial human tissues pharmaceutical and cosmetic industry carry out tolerance, toxicology and irritation studies day by day. In spite of every progress made in terms of media compositions and supplements, setup and handling of organotypic cultures still needs a lot of time and expertise.

setup and handling of organotypic cultures still needs a lot of time and expertise

Up to now, increased hands-on time and human-induced variations in culture processes can cut the success in high throughput reconstruction of human tissue. To deplete sources of unintended process fluctuations and to ensure high quality and reproducibility of in vitro tissues, the Fraunhofer Society and BRAND GMBH + CO KG collaborated in the development of the BRANDplates® Insert System. This 24-well platform is especially customized to meet all requirements for a totally automated handling of insert-based tissue cultures. The carrier plates are designed in a 24-well or in a modified 6-well shape according to requirements of ANSI/SLAS standards 1 and 4 (Figure a) and b)). The corresponding BRANDplates® Insert Strips consist of 4 inserts in a row (Figure c) and are hold in a fixed position at any time of automated handling.

6-well plate:

  • Use just one or two inserts per well to extend medium change interval.
  • For up to 4 inserts, medium in the well can be changed in one step (Figure b, pag. 3).

Inlet Opening System (IOS)

  • No leaking during cell seeding or initial coating.
  • Simultaneous change of medium in the well and insert.
  • Setup of air-liquid-interface in one step.
  • Compatible with 24- und 6-well BRANDplates®.

Insert:

  • Divided BRANDplates® Insert Strips for subsequent analysis.

Volumes needed for different culture phases

  24-well 6-well
Insert (e.g., coating, cell seeding) 50 - 400 μL 50 - 400 μL
Well: submerged culture 1.6 - 2 mL 8 - 10 mL
Well: air-liquid interface (wetted membrane) 0.8 mL
3.5 mL

BRANDplates® Inserts are available with the Inlet Opening System

BRANDplates® Inserts are available with the Inlet Opening System (patent pending, Figure c, pag. 3) which is dedicated to support the automated in vitro reconstruction of human skin. This peerless feature interconnects the medium of wells and inserts, giving the opportunity to establish the air-liquid interface without entering the inserts with pipette tips. In addition to this increase in safety for cultures, the IOS reduces the number of pipetting steps needed to change medium within the two compartments. This user manual describes in short the reconstruction of full thickness skin equivalents and provides tips for the handling of BRANDplates® Insert System.

I. Preparation of dermal components for full thickness skin equivalents

Protocol according to Promocell

1. Passaging of primary fibroblasts

Passaging of primary fibroblasts

2. Preparation of Collagen type I fibroblast mixture

Preparation of Collagen type I fibroblast mixture

3. Establishing fibroblast – collagen submerse culture

> 400 μL collagen - fibroblasts mix is needed per demal equivalent.

Advice: calculate an extra volume of 30 % to compensate for pipetting errors!

> 4.0 x 104 fibroblasts/400 μL

> 5.2 x 104 fibroblasts/520 μL

520 μL total

à 347 μL collagen

à 173 μL gel neutralization medium

Gel neutralizing medium contains:

1. 25 μL/mL Chondroitin-4-sulfate (gel cross linker)

2. 25 μL/mL Chondroitin-6-sulfate (gel cross linker)

3. 2 x DMEM

4. 90 mM HEPES

5. 3 % FCS

> Recommended collagen type I concentration:

   6 mg/mL.

> Preparation of collagen mixture on ice impedes risk of premature gelation.

> Use chilled pipets while mixing collagen.

> Avoid air bubbles!

> Collagen type I is usually dissolved in acetic acid (0.1 M, pH 3) and needs to be neutralized by titration of NaOH before adding cells.

> Alternatively use medium containing HEPES and/or sodium dicarbonate.

> Use inserts with membranes of 8 μm pore size!

Use of BRANDplates® Inserts with Inlet Opening System (IOS)

> Prevents culture damaging during medium application/changes.

> Reduced number of pipetting step is needed for medium application/changes.

> Provides lateral nutrient supply for collagen embedded fibroblasts.

Volume for submers culture in BRANDplates®:

> 24 well: 2 mL

> 6 well: 10 mL

II. Co-culture of collagen embedded fibroblasts and keratinocytes

4. Coating dermal equivalents with fibronectin

Coating dermal equivalents with fibronectin

5. Passaging of primary keratinocytes

Passaging of primary keratinocytes

Splitting of keratinocytes:

1. Remove culture medium.

2. Wash culture with prewarmed PBS/EDTA.

3. Add PBS/EDTA and incubate 10 min at 37°C, 5 % CO2.

4. Add 0.025 % trypsin/EDTA, incubate 5 min at 37°C, 5 % CO2.

- T 25 flask: 2 ml

- T 75 flask: 4 ml

- T175 flask: 8 ml

5. Stop trypsin digestion by KBM + 10 % FCS.

6. Transfer keratinocytes into a centrifuge tube.

6. Seeding of keratinocytes on top of dermal equivalents

Seeding of keratinocytes on top of dermal equivalents

0 - 7 DIV

> Cultivate dermal equivalents for 5-7 DIV.

> Change medium every 2 days.

> Stepwise reduce FCS-concentration from 10 % to 5 %.

during fibronectin incubation

> KBM: keratinocyte basal medium

When trypsinization is inefficient:

> Add recommended volume of trypsin/EDTA, incubate for 2-3 min at 37°C.

> Carefully remove solution from the culture, add trypsin/EDTA again and incubate for another 5 min at 37°C.

> Keratinocytes may react sensible to trypsin. Do not expose keratinocytes for more than 10 min to trypsin.

> Check under a microscope whether cells start to detach!

> Max. activity of trypsin is given at 37°C and between pH 7.6-7.8.

> Make sure that culture flasks are tightly sealed to avoid CO2 dependent pH decrease in the incubator.

after fibronectin coating

> Co-culture fibroblasts and keratinocytes for 6 to 7 DIV. Change medium every 2 days.

> Stepwise reduce FCS-concentration from 5 % to 0.

KGM: Keratinocyte Growth Medium

> KBM final concentration

+ Bovine Pituitary Extract 0.4 % v/v

+ Insulin (recombinant human) 5.0 μg/ml

+ Hydrocortisone 330 ng/ml

+ Epidermal Growth Factor (recombinant human) 125 ng/ml

+ Epinephrine 390 ng/ml

+ Transferrin, holo (human) 10 μg/ml

+ CaCl2 0.06 mM

+ 1 % Gentamycin (accord. to KGM2, PromoCell, Heidelberg, Germany)

 

III. Air-lift culture

7. Keratinocyte proliferation and stratification

Keratinocyte proliferation and stratification

8. Histological characterization of full thickness skin equivalents

Histological characterization of full thickness skin equivalents

8 - 19 DIV

Air-lift-medium:

> KGM supplemented with

+ Recombinant human insulin

+ Hydrocortisone

+ Transferrin, holo (human)

+ Epinephrine

+ 1.88 mM CaCl2

Well known markers for keratinocyte proliferation and differentiation:

Keratin 5 (K5)/ Keratin 14 (K14):

building heterodimers, subunits of a common intermediate filament, proliferation marker, normally expressed by keratinocytes of the stratum basale (Poumay et al., 2004)

Keratin1 (K1)/ Keratin 10 (K10):

building heterodimers, subunits of a common intermediate filament,early differentiation marker, expressed by keratinocytes of stratum spinosum (Poumay et al., 2004).

Involucrin:

localized in stratum spinosum and stratum croneum. Involucrin is part of cornified envelope of corneocytes.

Filaggrin:

a terminal differentiation marker in stratum corneum, present as profilaggin in stratum granulosum, important for skin barrier funtion (Sandiland A et al., 2009)

Loricrin:

expressed in stratum granulosum and deposited beneath the plasma membrane. Cross-linked to other proteins like involucrin, repetin, S100 proteins by transglutaminase-1, loricrin is part of the cornified envelop (Steinert PM et al., 1995).

Summary

The use of the BRANDplates® Insert System has various advantages when compared to common cell culture inserts. The special 6-well plate utilizes a unique conjoined 24- well design to optimize centering of the well inserts during the entire culture process. The geometry of inserts and plates define the so called feeding port. This extra cavity guarantees access to the well without shifting or rotating the inserts and disturbing the culture. The defined location of inserts and feeding ports helps to determine the position of applicators or aspirators integrated in automated processes. These attributes make the BRANDplates® Insert System the only 24-well culture insert- platform which can be implemented totally into a robot handled cell culture.

The described properties of the 6-well plate create even more benefit when combined with BRANDplates® Inserts showing the Inlet Opening System (IOS) (patent pending). The medium of wells and inserts is interconnected by the IOS, so that it is possible to control medium level in both compartments simultaneously resulting in just 6 instead of 48 pipetting steps during medium exchange and when an air-liquid interface needs to be established. The fusion of four inserts into one insert strip provides also remarkable advantages. Whenever inserts have to be moved, it is easy to grip one strip and transfer the four inserts in one move, e.g. transferring inserts from well to well during fixation, dehydration, washing or staining steps.

The use of the BRANDplates® Insert System has various advantages

Ordering Data

BRANDplates® Insert Strips

Insert Strips, smooth-walled or with inlet channels (Inlet Opening System*) PS. cellGrade™ plus surface, sterile. Strips of 4 inserts (divisible).

Description Pore size
μm
Pack of PC membrane
Cat. No.
PET membrane
Cat. No.
smooth-walled 8.0 12 (individually wrapped) 7828 60 7828 70
with Inlet Opening System 8.0 12 (individually wrapped) 7828 61 7828 71

BRANDplates® Insert System

6-well plates filled with 6 insert strips. PS. cellGrade™ plus surface, sterile. Insert strips, smooth-walled or with inlet channels (Inlet Opening System*). With lid with condensation rings.

Description Pore size
μm
Pack of plates with lid PC membrane
Cat. No.
PET membrane
Cat. No.
smooth-walled 8.0 5 (30 insert strips) 7828 62 7828 72
with Inlet Opening System 8.0 5 (30 insert strips) 7828 63 7828 63

* patent pending

BRANDplates®, BIO-CERT® and BRAND® are trademarks of BRAND GMBH + CO KG, Germany.

Other reproduced brands are the property of the respective owner.

Our technical literature is intended to inform and advise our customers. However, the validity of general empirical values, and of results obtained under test conditions, for specific applications depends on many factors beyond our control. Please appreciate, therefore, that no claims can be derived from our advice. The user is responsible for checking the appropriateness of the product for any particular application.

Subject to technical modification without notice. Errors excepted.

Materials