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Kratz, Gunnar
Publications (10 of 54) Show all publications
Toss, H., Lönnqvist, S., Nilsson, D., Sawatdee, A., Nissa, J., Fabiano, S., . . . Simon, D. T. (2017). Ferroelectric Surfaces for Cell Release. Synthetic metals, 228, 99-104
Open this publication in new window or tab >>Ferroelectric Surfaces for Cell Release
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2017 (English)In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 228, p. 99-104Article in journal (Refereed) Published
Abstract [en]

Adherent cells cultured in vitro must usually, at some point, be detached from the culture substrate. Presently, the most common method of achieving detachment is through enzymatic treatment which breaks the adhesion points of the cells to the surface. This comes with the drawback of deteriorating the function and viability of the cells. Other methods that have previously been proposed include detachment of the cell substrate itself, which risks contaminating the cell sample, and changing the surface energy of the substrate through thermal changes, which yields low spatial resolution and risks damaging the cells if they are sensitive to temperature changes. Here cell culture substrates, based on thin films of the ferroelectric polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) co-polymer, are developed for electroactive control of cell adhesion and enzyme-free detachment of cells. Fibroblasts cultured on the substrates are detached through changing the direction of polarization of the ferroelectric substrate. The method does not affect subsequent adhesion and viability of reseeded cells.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering Clinical Science
Identifiers
urn:nbn:se:liu:diva-121804 (URN)10.1016/j.synthmet.2017.04.013 (DOI)000401599600015 ()
Note

Funding agencies: Swedish Governmental Agency for Innovation Systems (VINNOVA) [2010-00507]; Knut and Alice Wallenberg Foundation; Onnesjo Foundation

Available from: 2015-10-07 Created: 2015-10-07 Last updated: 2018-04-13Bibliographically approved
Lönnqvist, S., Briheim, K. & Kratz, G. (2016). Non-occlusive topical exposure of human skin in vitro as model for cytotoxicity testing of irritant compounds. Toxicology Mechanisms and Methods, 26(2), 82-87
Open this publication in new window or tab >>Non-occlusive topical exposure of human skin in vitro as model for cytotoxicity testing of irritant compounds
2016 (English)In: Toxicology Mechanisms and Methods, ISSN 1537-6516, E-ISSN 1537-6524, Vol. 26, no 2, p. 82-87Article in journal (Refereed) Published
Abstract [en]

Testing of irritant compounds has traditionally been performed on animals and human volunteers. Animal testing should always be restricted and for skin irritancy mice and rabbits hold poor predictive value for irritant potential in humans. Irritant testing on human volunteers is restricted by the duration subjects can be exposed, and by the subjectivity of interpreting the visual signs of skin irritation. We propose an irritant testing system using viable human full thickness skin with the loss of cell viability in the exposed skin area as end point measurement. Skin was exposed to sodium dodecyl sulfate (SDS) at 20% concentration by non-occluded topical exposure to establish a positive control response and subsequent test compounds were statistically compared with the 20% SDS response. Cell viability and metabolism were measured with 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The model presents correlation between increased concentration of SDS and decreased viability of cells in the exposed skin area (R2 = 0.76). We propose the model to be used for cytotoxicity testing of irritant compounds. With fully intact barrier function, the model comprises all cells present in the skin with quantifiable end point measurement.

Place, publisher, year, edition, pages
Taylor & Francis, 2016
Keywords
Human full thickness skin, in vitro model, SDS
National Category
Pharmacology and Toxicology
Identifiers
urn:nbn:se:liu:diva-123312 (URN)10.3109/15376516.2015.1091537 (DOI)000373528000002 ()26446981 (PubMedID)
Available from: 2015-12-10 Created: 2015-12-10 Last updated: 2018-01-10Bibliographically approved
Lönnqvist, S., Rakar, J., Briheim, K. & Kratz, G. (2015). Biodegradable Gelatin Microcarriers Facilitate Re-Epithelialization of Human Cutaneous Wounds - An In Vitro Study in Human Skin. PLoS ONE, 10(6), e0128093
Open this publication in new window or tab >>Biodegradable Gelatin Microcarriers Facilitate Re-Epithelialization of Human Cutaneous Wounds - An In Vitro Study in Human Skin
2015 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 6, p. e0128093-Article in journal (Refereed) Published
Abstract [en]

The possibility to use a suspended tridimensional matrix as scaffolding for re-epithelialization of in vitro cutaneous wounds was investigated with the aid of a human in vitro wound healing model based on viable full thickness skin. Macroporous gelatin microcarriers, CultiSpher-S, were applied to in vitro wounds and cultured for 21 days. Tissue sections showed incorporation of wound edge keratinocytes into the microcarriers and thicker neoepidermis in wounds treated with microcarriers. Thickness of the neoepidermis was measured digitally, using immunohistochemical staining of keratins as epithelial demarcation. Air-lifting of wounds enhanced stratification in control wounds as well as wounds with CultiSpher-S. Immunohistochemical staining revealed expression of keratin 5, keratin 10, and laminin 5 in the neoepidermal component. We conclude that the CultiSpher-S microcarriers can function as tissue guiding scaffold for re-epithelialization of cutaneous wounds.

Place, publisher, year, edition, pages
Public Library of Science, 2015
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-120232 (URN)10.1371/journal.pone.0128093 (DOI)000355979500074 ()26061630 (PubMedID)
Available from: 2015-07-21 Created: 2015-07-20 Last updated: 2017-12-04
Rakar, J., Krammer, M. P. & Kratz, G. (2015). Human melanocytes mitigate keratinocyte-dependent contraction in an in vitro collagen contraction assay. Burns, 41(5), 1035-1042
Open this publication in new window or tab >>Human melanocytes mitigate keratinocyte-dependent contraction in an in vitro collagen contraction assay
2015 (English)In: Burns, ISSN 0305-4179, E-ISSN 1879-1409, Vol. 41, no 5, p. 1035-1042Article in journal (Refereed) Published
Abstract [en]

Scarring is an extensive problem in burn care, and treatment can be especially complicated in cases of hypertrophic scarring. Contraction is an important factor in scarring but the contribution of different cell types remains unclear. We have investigated the contractile behavior of keratinocytes, melanocytes and fibroblasts by using an in vitro collagen gel assay aimed at identifying a modulating role of melanocytes in keratinocyte-mediated contraction. Cells were seeded on a collagen type I gel substrate and the change in gel dimensions were measured over time. Hematoxylin and Eosin-staining and immunohistochemistry against pan-cytokeratin and microphthalmia-associated transcription factor showed that melanocytes integrated between keratinocytes and remained there throughout the experiments. Keratinocyte- and fibroblast-seeded gels contracted significantly over time, whereas melanocyte-seeded gels did not. Co-culture assays showed that melanocytes mitigate the keratinocyte-dependent contraction (significantly slower and 18-32% less). Fibroblasts augmented the contraction in most assays (approximately 6% more). Non-contact co-cultures showed some influence on the keratinocyte-dependent contraction. Results show that mechanisms attributable to melanocytes, but not fibroblasts, can mitigate keratinocyte contractile behavior. Contact-dependent mechanisms are stronger modulators than non-contact dependent mechanisms, but both modes carry significance to the contraction modulation of keratinocytes. Further investigations are required to determine the mechanisms involved and to determine the utility of melanocytes beyond hypopigmentation in improved clinical regimes of burn wounds and wound healing.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2015
Keywords
Melanocytes; Keratinocytes; Contraction; Wound healing; Fibroblasts; Scars
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-120329 (URN)10.1016/j.burns.2014.10.034 (DOI)000357350100015 ()25466959 (PubMedID)
Available from: 2015-07-31 Created: 2015-07-31 Last updated: 2017-12-04
Lönnqvist, S., Emanuelsson, P. & Kratz, G. (2015). Influence of acidic pH on keratinocyte function and re-epithelialisation of human in vitro wounds. Journal of Plastic Surgery and Hand Surgery, 49(6), 346-352
Open this publication in new window or tab >>Influence of acidic pH on keratinocyte function and re-epithelialisation of human in vitro wounds
2015 (English)In: Journal of Plastic Surgery and Hand Surgery, ISSN 2000-656X, E-ISSN 2000-6764, Vol. 49, no 6, p. 346-352Article in journal (Refereed) Published
Abstract [en]

Background: Chronic wounds are one of the greatest challenges for the healthcare system. Today, a plethora of dressings are used in the treatment of these wounds, each with specific influence on the wound environment. Due to differences in the permeability of the dressings the use will result in differences in the pH balance in the wound bed. However, little is known about how changes in the pH in the wound environment affect the different phases of the healing process. Aim: The aim of the present study was to investigate the effects of acidic pH on the regeneration phase by studying keratinocyte function in vitro and re-epithelialisation in an in vitro model of human skin. Results:In vitro assays showed reduced viability and migration rates in human keratinocytes when pH was lowered. Real time PCR revealed differential expression of genes related to wound healing and environmental impairment. Tissue culture showed no re-epithelialisation of wounds subjected to pH 5.0 and moderate re-epithelialisation at pH 6.0, compared to controls at pH 7.4. Conclusion: The results indicate that lowering pH down to pH 5.0 in wounds is counterproductive in aspect of keratinocyte function which is crucial for successful wound healing.

Place, publisher, year, edition, pages
Taylor & Francis, 2015
Keywords
Keratinocyte; pH; re-epithelialisation; wound model
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-123140 (URN)10.3109/2000656X.2015.1053397 (DOI)000364409400006 ()26051107 (PubMedID)
Available from: 2015-12-07 Created: 2015-12-04 Last updated: 2017-12-01Bibliographically approved
Persson, K., Lönnqvist, S., Tybrandt, K., Gabrielsson, R., Nilsson, D., Kratz, G. & Berggren, M. (2015). Matrix Addressing of an Electronic Surface Switch Based on a Conjugated Polyelectrolyte for Cell Sorting. Advanced Functional Materials, 25(45), 7056-7063
Open this publication in new window or tab >>Matrix Addressing of an Electronic Surface Switch Based on a Conjugated Polyelectrolyte for Cell Sorting
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2015 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 25, no 45, p. 7056-7063Article in journal (Refereed) Published
Abstract [en]

Spatial control of cell detachment is potentially of great interest when selecting cells for clonal expansion and in order to obtain a homogeneous starting population of cells aimed for tissue engineering purposes. Here, selective detachment and cell sorting of human primary keratinocytes and fibroblasts is achieved using thin films of a conjugated polymer. Upon electrochemical oxidation, the polymer film swells, cracks, and finally detaches taking cells cultured on top along with it. The polymer can be patterned using standard photolithography to fabricate a cross-point matrix with polymer pixels that can be individually addressed and thus detached. Detachment occurs above a well-defined threshold of +0.7 V versus Ag/AgCl, allowing the use of a relatively simple and easily manufactured passive matrix-addressing configuration, based on a resistor network, to control the cell-sorting device.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2015
National Category
Clinical Medicine Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-123754 (URN)10.1002/adfm.201503542 (DOI)000366502900010 ()
Note

Funding Agencies|Swedish Foundation for Strategic Research; VINNOVA (the OBOE center) [2010-00507]; Onnesjo foundation (Holmen); Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

Available from: 2016-01-11 Created: 2016-01-11 Last updated: 2017-11-30
Cieślar-Pobuda, A., Vilas Jain, M., Kratz, G., Rzeszowska-Wolny, J., Ghavami, S. & Wiechec, E. (2015). The expression pattern of PFKFB3 enzyme distinguishes between induced-pluripotent stem cells and cancer stem cells.. OncoTarget, 6(30), 29753--29770
Open this publication in new window or tab >>The expression pattern of PFKFB3 enzyme distinguishes between induced-pluripotent stem cells and cancer stem cells.
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2015 (English)In: OncoTarget, ISSN 1949-2553, E-ISSN 1949-2553, Vol. 6, no 30, p. 29753--29770Article in journal (Refereed) Published
Abstract [en]

Induced pluripotent stem cells (iPS) have become crucial in medicine and biology. Several studies indicate their phenotypic similarities with cancer stem cells (CSCs) and a propensity to form tumors. Thus it is desirable to identify a trait which differentiates iPS populations and CSCs. Searching for such a feature, in this work we compare the restriction (R) point-governed regulation of cell cycle progression in different cell types (iPS, cancer, CSC and normal cells) based on the expression profile of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase3 (PFKFB3) and phosphofructokinase (PFK1). Our study reveals that PFKFB3 and PFK1 expression allows discrimination between iPS and CSCs. Moreover, cancer and iPS cells, when cultured under hypoxic conditions, alter their expression level of PFKFB3 and PFK1 to resemble those in CSCs. We also observed cell type-related differences in response to inhibition of PFKFB3. This possibility to distinguish CSC from iPS cells or non-stem cancer cells by PFKB3 and PFK1 expression improves the outlook for clinical application of stem cell-based therapies and for more precise detection of CSCs.

Place, publisher, year, edition, pages
Albany, NY, USA: Impact Journals LLC, 2015
Keywords
PFKFB3; R-point; cancer stem cells; induced pluripotent stem cells
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:liu:diva-121349 (URN)10.18632/oncotarget.4995 (DOI)000363183200098 ()26337471 (PubMedID)
Available from: 2015-09-14 Created: 2015-09-14 Last updated: 2018-01-11Bibliographically approved
Lönnqvist, S., Karlsson, M. & Kratz, G. (2015). Tracing human keratinocytes and melanocytes with carboxyfluorescein hydroxysuccinimidyl ester (CFSE) staining.
Open this publication in new window or tab >>Tracing human keratinocytes and melanocytes with carboxyfluorescein hydroxysuccinimidyl ester (CFSE) staining
2015 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Burn treatment and conditions of hypopigmentation may require autologous transplantation of keratinocytes and melanocytes. The tracing of transplanted cells presents a challenge. We report a methodology based on passive staining with carboxyfluorescein hydroxysuccinimidyl ester (CFSE) that enables localising cells in tissue sections to investigate the fate of transplanted cells in wound re-epithelialisation. CFSE-stained keratinocytes and CFSE-stained melanocytes were transplanted to human full thickness in vitro wounds either as cell suspension for keratinocytes, or with the aid of  macroporous gelatin microcarriers for both cells types in single and co-culture. Viability and migration of CFSE-stained keratinocytes and melanocytes were investigated, and proliferation of the cells cultured on microcarriers was measured with flow cytometry. Wounds with transplanted cells were harvested after seven, 14 and 21 days in culture, cryosectioned and investigated using fluorescence microscopy. Sections from wounds with transplanted co-cultured keratinocytes and melanocytes were stained for pancytokeratin to distinguish double stained keratinocytes. The CFSE-staining of keratinocytes and melanocytes did not affect the viability, migration or proliferation of the cells. Transplanted cells were traced in tissue sections after 21 days and wound re-epithelialisation was not affected. We propose a novel application of CFSE-staining in transplantation studies here presented with primary human keratinocytes and melanocytes.

National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-123310 (URN)
Available from: 2015-12-10 Created: 2015-12-10 Last updated: 2015-12-10Bibliographically approved
Persson, K. M., Lönnqvist, S. L., Tybrandt, K., Gabrielsson, R., Nilsson, D., Kratz, G. & Berggren, M. (2014). Selective Detachment of Human Primary Keratinocytes and Fibroblasts Using an Addressable Conjugated Polymer Matrix.
Open this publication in new window or tab >>Selective Detachment of Human Primary Keratinocytes and Fibroblasts Using an Addressable Conjugated Polymer Matrix
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2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Conjugated polymers have been used in several applications for electronic control of cell cultures over the last years. We have shown detachment of human endothelial cells using a thin film of a self-doped water-soluble conjugated polymer. Upon electrochemical oxidation, the film swells, cracks and finally detaches taking cells cultured on top along with it. The polymer can be patterned using standard photolithography. The detachment only occurs above a threshold potential of +0.7 V and this fact has been used to create a simple actively addressed matrix, based on a resistor network placed in an encapsulated back plane. The matrix has individually detachable pixels. In this paper we have evaluated detachment of human primary keratinocytes and fibroblasts using PEDOT-S:H. In addition, we have studied effects of serum proteins, added as nutrients to the cell culture medium, on the detachment properties. It was found that at prolonged incubation times protein adhesion effectively stopped the detachment. Using shorter incubation times before detachment, both keratinocytes and fibroblasts can be detached using a regular planar device as well as the matrix device for selective detachment. Spatial control of detachment could be of use when selecting cells for clonal expansion and in order to obtain a homogeneous starting population of cells aimed for tissue engineering purposes.

National Category
Polymer Chemistry Cell Biology
Identifiers
urn:nbn:se:liu:diva-106252 (URN)
Available from: 2014-04-30 Created: 2014-04-30 Last updated: 2017-02-03Bibliographically approved
Junker, J., Lönnqvist, S., Rakar, J., Karlsson, L. K., Grenegård, M. & Kratz, G. (2013). Differentiation of human dermal fibroblasts towards endothelial cells. Differentiation, 85(3), 67-77
Open this publication in new window or tab >>Differentiation of human dermal fibroblasts towards endothelial cells
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2013 (English)In: Differentiation, ISSN 0301-4681, E-ISSN 1432-0436, Vol. 85, no 3, p. 67-77Article in journal (Refereed) Published
Abstract [en]

The ultimate goal of vascular tissue engineering is the production of functional grafts for clinical use. Difficulties acquiring autologous endothelial cells have motivated the search for alternative cell sources. Differentiation of dermal fibroblasts towards several mesenchymal lineages as well as endothelial cells has been proposed. The aim of the present study was to investigate the endothelial differentiation capacity of human dermal fibroblasts on a gene expression, protein expression and functional physiological level. Endothelial differentiation of fibroblasts was induced by culturing cells in 30% human serum, but not in fetal calf serum. Expression of proteins and genes relevant for endothelial function and differentiation was increased after induction. Furthermore, fibroblasts exposed to 30% human serum displayed increased uptake of low-density lipoprotein and formation of capillary-like networks. The results of this study may have an impact on cell sourcing for vascular tissue engineering, and the development of methods for vascularization of autologous tissue engineered constructs.

Place, publisher, year, edition, pages
Wiley-Blackwell / Elsevier, 2013
Keywords
Differentiation; Endothelial cell; Fibroblast; Tissue engineering; Human serum
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-96492 (URN)10.1016/j.diff.2013.01.005 (DOI)000320766300001 ()
Available from: 2013-08-23 Created: 2013-08-20 Last updated: 2017-12-06
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