Thermolysin in human cultured keratinocyte isolation

Comparison of Two Human Skin Cell Isolation Protocols and Their Influence on Keratinocyte and Fibroblast Culture

For the development of advanced therapies, the use of primary cells instead of cell lines is preferred. The manufacture of human tissue-engineered skin substitutes requires efficient isolation and culture protocols allowing a massive expansion of the cells in culture from an initial specimen of a minimal size. This study compared two skin cell isolation protocols, routinely applied in two clinical laboratories. Epithelial (keratinocytes) and dermal (fibroblasts) cells were isolated and cultured from three human skin biopsies (N = 3). The two-step digestion protocol (LOEX-Protocol) firstly used thermolysin to enzymatically disrupt the dermal-epidermal junction while, for the one-step digestion protocol (UPCIT-Protocol), mechanical detachment with scissors was applied. Then, the epidermal and dermal layers were digested, respectively, to achieve cell isolation. The cell size, viability, yield and growth were analyzed over five passages (P). The colony-forming efficiency (CFE) and Keratin 19 (K19) expression of epithelial cells were also assessed after P0 and P1. Regarding the dermal cells, no significant differences were observed in the tested parameters of isolation and culture. However, for the epithelial cells, viability was higher (93% vs. 85%) and the number of cells extracted per cm2 of skin was 3.4 times higher using the LOEX-Protocol compared to the UPCIT-Protocol. No significant difference was observed for any parameter once the keratinocytes were cultured from P1 to P4. The CFE and K19 expression decreased from P0 to P1 in both protocols, probably due to the culture process. This study shows that both protocols enable the efficient isolation of skin dermal and epithelial cells and subsequent culture to produce grafts destined for the treatment of patients.

Preclinical study models of psoriasis: State-of-the-art techniques for testing pharmaceutical products in animal and nonanimal models

Local and systemic treatments exist for psoriasis, but none can do more than control its symptoms because of its numerous unknown mechanisms. The lack of validated testing models or a defined psoriatic phenotypic profile hinders antipsoriatic drug development. Despite their intricacy, immune-mediated diseases have no improved and precise treatment. The treatment actions may now be predicted for psoriasis and other chronic hyperproliferative skin illnesses using animal models. Their findings confirmed that a psoriasis animal model could mimic a few disease conditions. However, their ethical approval concerns and inability to resemble human psoriasis rightly offer to look for more alternatives. Hence, in this article, we have reported various cutting-edge techniques for the preclinical testing of pharmaceutical products for the treatment of psoriasis.

Efficient isolation and high yield of epidermal cells from foreskin biopsies by dynamic trypsinization

Cultured keratinocytes play important roles in burn wound healing and scientific research studies. We aimed to modify the isolation method to avoid over-digestion, maximize the number of isolated epidermal cells and establish a more efficient and innocuous way of cell isolation. Compared to the conventional method, the modified method combines the more dynamic process of enzymatic digestion with multiple harvestings of dissociated cells via digestion. The cells from each harvesting were immediately re-suspended in culture medium with serum to avoid extended trypsinization and then pooled for further analysis. The number of viable cells isolated per gram of adult foreskin epidermis was (18.88±13.22)×10⁶ cells in the control group and (67.34±30.66)×10⁶ cells in the modified group (p<0.001). No significant differences were observed in the proportion of CD49f-positive cells between the two groups (p>0.05). The modified method was significantly more efficient in dissociating keratinocytes from each unit of skin biopsy, which is particularly important for treating severe burns when donor skin is limited.

Dermal-epidermal separation methods: research implications

Dermal-epidermal separation is an important basic investigation technique for pharmacology, toxicology and biology. To choose the optimal method for a given research need, we reviewed studies on epidermal separation. PubMed, Embase, and Web of Science were utilized. Different separation systems have been compared, including chemical, enzyme, heat and mechanical separation; each has advantages and disadvantages. Heat is simple but causes thermal damage. Chemical reagents are effective but disturb cellular electrolyte equilibrium. Enzymes provide complete separation, but destroy important components. Mechanical division does not alter physical and/or chemical integrity, but necessitates a relatively large sample and may cause cross-contamination of layers. Thus, the appropriate method should be chosen for a given research question, and no single method appears superior for all purposes.

An evaluation of the choice of feeder cell growth arrest for the production of cultured epidermis

Growth arrested 3T3 cells have been used as feeder cells in human epidermal keratinocyte cultures to produce cultured epidermal autografts for the treatment of burns. The feeder cells were ideally growth-arrested by gamma-irradiation. Alternatively, growth arrest by mitomycin C treatment is a cost effective option. We compared the functional efficacy of these two approaches in keratinocyte cultures by colony forming efficiency, the net growth area of colonies, BrdU labeling and histological features of cultured epidermal sheets. The growth area estimation involved a semi-automated digital technique using the Adobe Photoshop and comprised of isolation and enumeration of red pixels in Rhodamine B-stained keratinocyte colonies. A further refinement of the technique led to the identification of critical steps to increasing the degree of accuracy and enabling its application as an extension of colony formation assay. The results on feeder cell functionality revealed that the gamma irradiated feeders influenced significantly higher colony forming efficiency and larger growth area than the mitomycin C treated feeders. The BrdU labeling study indicated significant stimulation of the overall keratinocyte proliferation by the gamma irradiated feeders. The cultured epidermal sheets produced by gamma feeders were relatively thicker than those produced by mitomycin C feeders. We discussed the clinical utility of mitomycin C feeders from the viewpoint of cost-effective burn care in developing countries.

Comparison of the enzymatic and explant methods for the culture of keratinocytes isolated from human foreskin

Currently, culture and growth keratinocytes are important stages in achieving a reliable and reproducible skin tissue. In the present study, two different methods, enzymatic and explant methods, for keratinocytes isolation from human foreskin were compared. Foreskins were cut into 2-3 mm pieces and placed in trypsin at 4°C overnight for separation of the epidermis from the dermis. Subsequently, these samples were divided into two groups: i) Keratinocytes separated from the epidermis by trypsin and ii) by the explant method. These keratinocytes were divided into two groups: i) With no feeder layer and ii) onto a type I collagen scaffold. The cells were evaluated using immunocytochemistry and 4',6-diamidine-2'-phenylindole dihydrochloride (DAPI) staining. In the enzymatic treatment, after 7-10 days no attached cells were found in the cell culture dishes. In the explant method, keratinocytes were separated after ~24 h, attached rapidly and formed big colonies into a collagen scaffold. In the absence of a feeder layer, small colonies were developed with rapid loss of proliferation within 2-3 days. Keratinocytes showed positive immunoreactivity for the pan-cytokeratin marker and keratinocytes' nuclei were clearly observed. This method could be applied and developed as a component of skin substitutes to treat burns and wounds and also in laboratory testing.

Control of the skin scarring response

There comes a time when the understanding of the cutaneous healing process becomes essential due to the need for a precocious tissue repair to reduce the physical, social, and psychological morbidity. Advances in the knowledge on the control of interaction among cells, matrix and growth factors will provide more information on the Regenerative Medicine, an emerging area of research in medical bioengineering. However, considering the dynamism and complexity of the cutaneous healing response, it is fundamental to understand the control mechanism exerted by the interaction and synergism of both systems, cutaneous nervous and central nervous, via hypothalamus hypophysis-adrenal axis, a relevant subject, but hardly ever explored. The present study reviews the neuro-immune-endocrine physiology of the skin responsible for its multiple functions and the extreme disturbances of the healing process, like the excess and deficiency of the extracellular matrix deposition.