A high yield method for growing primary canine keratinocytes

Characterization of canine epidermal organoid cultures by immunohistochemical analysis and quantitative PCR

BACKGROUND

Keratinocyte organoids can be used as a tool to evaluate epidermal structure, function and dysfunction.

OBJECTIVES

To optimize the canine keratinocyte organoid system and produce organoids that are structurally equivalent to in vivo canine epidermis, in order to enable studies that focus on epidermal diseases and diseases resulting from an impaired epidermal barrier.

ANIMALS

Skin biopsies were obtained from five recently euthanized dogs of different breeds with no skin abnormalities.

METHODS AND MATERIALS

Cells derived from microdissected interfollicular epidermis were seeded in basement membrane extract and epidermal organoids were grown under different media conditions. Organoids were characterized to assess cell morphology and architecture in haematoxylin and eosin-stained slides and expression of selected epidermal markers (keratin 5, keratin 10, loricrin and filaggrin) by immunohistochemical analysis and quantitative reverse transcription PCR.

RESULTS

The selected epidermal markers were expressed in the same epidermal layers in the organoids cultured in expansion medium and differentiation medium as in normal interfollicular epidermis, yet restriction to the distinct layers was best achieved with expansion medium. Comparison of the mRNA expression levels of these markers revealed that relative expression is similar in organoids cultured in expansion medium and normal canine epidermis, while it differs in organoids cultured in differentiation medium.

CONCLUSION AND CLINICAL IMPORTANCE

Organoids cultured in expansion medium have an equivalent structure to the interfollicular epidermis and express key marker proteins in similar proportions. Epidermal organoids are therefore a promising in vitro model to study epidermal structure, function and dysfunction.

Expression of functional TRPV1 receptor in primary culture of canine keratinocytes

The interest for the endovanilloid system and for transient receptor potential vanilloid 1 (TRPV1) is continuously increasing, due to their involvement in inflammation, nociception and pruritus. Even if TRPV1 enrolment was highlighted in both physiological and pathological conditions, some aspects remain unclear, mostly in veterinary medicine. This study aimed to verify the expression and functionality of TRPV1 in canine keratinocytes to investigate in vitro the role of TRPV1 in these cells that are involved in different cutaneous pathologies. Keratinocytes primary cultures were isolated from bioptical samples and cultivated. Binding assay (using ³ [H]-resiniferatoxin), displacement assay (in the presence of 1.2 nM ³ [H]-resiniferatoxin) and functional assays (in the presence of 1 μCi/⁴⁵ Ca²⁺ ) with vanilloid agonists and antagonists, specifically addressed to TRPV1 receptor, were performed. Binding assay demonstrated the presence of measurable concentrations of TRPV1 (B_max  = 1,240 ± 120 fmol/mg protein; K_d  = 0.01 ± 0.004 nM). Displacement assay highlighted the highest affinity for resiniferatoxin (RTX) and 5-iodo-resiniferatoxin (5-I-RTX), among agonists and antagonists, respectively. The same compounds results as the most potent in the functional assays. This study demonstrated the identification and the characterization of TRPV1 receptor in primary canine keratinocytes cultures. The results are promising for a clinical use, but further in vivo investigations are required.

In vitro biocompatibility of chitosan porous skin regenerating templates (PSRTs) using primary human skin keratinocytes

Biopolymer chitosan (beta-1,4-d-glucosamine) comprises the copolymer mixture of N-acetylglucosamine and glucosamine. The natural biocompatibility and biodegradability of chitosan have recently highlighted its potential use for applications in wound management. Chemical and physical modifications of chitosan influence its biocompatibility and biodegradability, but it is unknown as to what degree. Hence, the biocompatibility of the chitosan porous skin regenerating templates (PSRT 82, 87 and 108) was determined using an in vitro toxicology model at the cellular and molecular level on primary normal human epidermal keratinocytes (pNHEK). Cytocompatibility was accessed by using a 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl tetrazolium bromide (MTT) assay from 24 to 72h. To assess the genotoxicity of the PSRTs, DNA damage to the pNHEK was evaluated by using the Comet assay following direct contact with the various PSRTs. Furthermore, the skin pro-inflammatory cytokines TNF-alpha and IL-8 were examined to evaluate the tendency of the PSRTs to provoke inflammatory responses. All PSRTs were found to be cytocompatible, but only PSRT 108 was capable of stimulating cell proliferation. While all of the PSRTs showed some DNA damage, PSRT 108 showed the least DNA damage followed by PSRT 87 and 82. PSRT 87 and 82 induced a higher secretion of TNF-alpha and IL-8 in the pNHEK cultures than did PSRT 108. Hence, based on our experiments, PSRT 108 is the most biocompatible wound dressing of the three tested.

Dietary constituents are able to play a beneficial role in canine epidermal barrier function

Epidermal barrier function is a critical attribute of mammalian skin. The barrier is responsible for preventing skin-associated pathologies through controlling egress of water and preventing ingress of environmental agents. Maintaining the quality and integrity of the epidermal barrier is therefore of considerable importance. Structurally, the barrier is composed of two main parts, the corneocytes and the intercellular lamellar lipid. The epidermal lamellar lipid comprises mainly ceramides, sterols and fatty acids. Twenty-seven nutritional components were screened for their ability to upregulate epidermal lipid synthesis. Seven of the 27 nutritional components (pantothenate, choline, nicotinamide, histidine, proline, pyridoxine and inositol) were subsequently retested using an in vitro transepidermal diffusion experimental model, providing a functional assessment of barrier properties. Ultimately, the best performing five nutrients were fed to dogs at supplemented concentrations in a 12-week feeding study. Barrier function was measured using transepidermal water loss (TEWL). It was found that a combination of pantothenate, choline, nicotinamide, histidine and inositol, when fed at supplemented concentrations, was able to significantly reduce TEWL in dogs after 9 weeks.