Inhibitory effects of human serum on human fetal skin fibroblast migration: migration-inhibitory activity and substances in serum, and its age-related changes

Human Blood Serum Induces p38-MAPK- and Hsp27-Dependent Migration Dynamics of Adult Human Cardiac Stem Cells: Single-Cell Analysis via a Microfluidic-Based Cultivation Platform

Simple Summary

Adult human stem cells possess the ability to contribute to endogenous regeneration processes of injured tissue by migrating to specific locations. For stem cell-based clinical applications it is highly important to gain knowledge about the migration behavior of adult human stem cells and the underlying molecular mechanisms of this ability. Human blood serum has been shown to have beneficial effects on other regenerative capacities of adult human stem cells. Within this study we tested the effect of human blood serum on the migration behavior of stem cells from the human heart. We used a microfluidic cultivation device, which allowed us to monitor the living cells and their movement behavior in real time. After addition of human blood serum, the heart stem cells increased their speed of movement and covered distance. Further, we observed that this effect could be diminished by inhibition of a specific kinase, p38-MAPK. Thus, our data suggest beneficial effects of human blood serum on adult human heart stem cells dependent on p38-MAPK. Our study contributes to a deeper understanding of the dynamics of stem cell migration and introduces a new platform to monitor stem cell movement in real time.

Abstract

Migratory capabilities of adult human stem cells are vital for assuring endogenous tissue regeneration and stem cell-based clinical applications. Although human blood serum has been shown to be beneficial for cell migration and proliferation, little is known about its impact on the migratory behavior of cardiac stem cells and underlying signaling pathways. Within this study, we investigated the effects of human blood serum on primary human cardiac stem cells (hCSCs) from the adult heart auricle. On a technical level, we took advantage of a microfluidic cultivation platform, which allowed us to characterize cell morphologies and track migration of single hCSCs via live cell imaging over a period of up to 48 h. Our findings showed a significantly increased migration distance and speed of hCSCs after treatment with human serum compared to control. Exposure of blood serum-stimulated hCSCs to the p38 mitogen-activated protein kinase (p38-MAPK) inhibitor SB239063 resulted in significantly decreased migration. Moreover, we revealed increased phosphorylation of heat shock protein 27 (Hsp27) upon serum treatment, which was diminished by p38-MAPK-inhibition. In summary, we demonstrate human blood serum as a strong inducer of adult human cardiac stem cell migration dependent on p38-MAPK/Hsp27-signalling. Our findings further emphasize the great potential of microfluidic cultivation devices for assessing spatio-temporal migration dynamics of adult human stem cells on a single-cell level.

Adult-Fetal Fibroblast Interactions: Effects on Cell Migration and Implications for Cell Transplantation

Wound healing is a complex process involving close cooperation between multiple cell types. During wound healing, fibroblasts are primarily responsible for synthesis of the replacement extracellular matrix. Fibroblast therapy is under investigation in this and other laboratories for its potential use to modulate the final outcome of the wound-healing process. This study addresses the potential interactions between transplanted and host fibroblasts, using a two-dimensional mixed culture model. Our results show that fibroblasts of two different phenotypes, fetal and adult, exhibit different speeds of in vitro migration. These migration speeds are conserved in mixed cocultures, suggesting that the migratory response is an intrinsic property of the fibroblast rather than a response to juxtacrine or paracrine signals. These results have relevance for cell-based therapies in that they demonstrate that donor fibroblasts of a different phenotype may at least partially retain that phenotype in the host environment and in the presence of endogenous fibroblasts.

Chaperonin containing T-complex polypeptide subunit eta (CCT-eta) is a specific regulator of fibroblast motility and contractility

Integumentary wounds in mammalian fetuses heal without scar; this scarless wound healing is intrinsic to fetal tissues and is notable for absence of the contraction seen in postnatal (adult) wounds. The precise molecular signals determining the scarless phenotype remain unclear. We have previously reported that the eta subunit of the chaperonin containing T-complex polypeptide (CCT-eta) is specifically reduced in healing fetal wounds in a rabbit model. In this study, we examine the role of CCT-eta in fibroblast motility and contractility, properties essential to wound healing and scar formation. We demonstrate that CCT-eta (but not CCT-beta) is underexpressed in fetal fibroblasts compared to adult fibroblasts. An in vitro wound healing assay demonstrated that adult fibroblasts showed increased cell migration in response to epidermal growth factor (EGF) and platelet derived growth factor (PDGF) stimulation, whereas fetal fibroblasts were unresponsive. Downregulation of CCT-eta in adult fibroblasts with short inhibitory RNA (siRNA) reduced cellular motility, both basal and growth factor-induced; in contrast, siRNA against CCT-beta had no such effect. Adult fibroblasts were more inherently contractile than fetal fibroblasts by cellular traction force microscopy; this contractility was increased by treatment with EGF and PDGF. CCT-eta siRNA inhibited the PDGF-induction of adult fibroblast contractility, whereas CCT-beta siRNA had no such effect. In each of these instances, the effect of downregulating CCT-eta was to modulate the behavior of adult fibroblasts so as to more closely approximate the characteristics of fetal fibroblasts. We next examined the effect of CCT-eta modulation on alpha-smooth muscle actin (alpha-SMA) expression, a gene product well known to play a critical role in adult wound healing. Fetal fibroblasts were found to constitutively express less alpha-SMA than adult cells. Reduction of CCT-eta with siRNA had minimal effect on cellular beta-actin but markedly decreased alpha-SMA; in contrast, reduction of CCT-beta had minimal effect on either actin isoform. Direct inhibition of alpha-SMA with siRNA reduced both basal and growth factor-induced fibroblast motility. These results indicate that CCT-eta is a specific regulator of fibroblast motility and contractility and may be a key determinant of the scarless wound healing phenotype by means of its specific regulation of alpha-SMA expression.

Fetal ACL fibroblasts exhibit enhanced cellular properties compared with adults

Fetal tendons and skin heal regeneratively without scar formation. Cells isolated from these fetal tissues exhibit enhanced cellular migration and collagen production in comparison to cells from adult tissue. We determined whether fetal and adult fibroblasts isolated from the anterior cruciate ligament (ACL), a tissue that does not heal regeneratively, exhibit differences in cell migration rates and collagen elaboration. An in vitro migration assay showed fetal ACL fibroblasts migrated twice as fast as adult ACL fibroblasts at a rate of 38.90 +/- 7.69 microm per hour compared with 18.88 +/- 4.18 microm per hour, respectively. Quantification of Type I collagen elaboration by enzyme-linked immunosorbent assay showed fetal ACL fibroblasts produced four times the amount of Type I collagen compared with adult ACL fibroblasts after 7 days in culture. We observed no differences in Type III collagen with time for adult or fetal ACL fibroblasts. Our findings indicate fetal ACL fibroblasts are intrinsically different from adult ACL fibroblasts, suggesting the healing potential of the ACL may be age-dependent.

Microengineered surface topography facilitates cell grafting from a prototype hydrogel wound dressing with antibacterial capability

Skin wounds derive therapeutic benefit from redeployment of dermal tissues, whether as split-thickness allo- and autografts or as biological dressings comprising cultured cells. However, the clinical outcome is strongly influenced by the techniques used for cell/tissue grafting and also the microbiological status of the wound. Here we report that microtopography incorporated into the surface of a novel polymeric material, derivatized with fibronectin to promote attachment and encourage motility, improved the efficiency of cell transfer onto de-epithelialized human skin ex vivo. The microtopography had two functions, first as a conduit for migrating cells to cross between the vehicle and recipient surface and second to shield adherent cells from destruction by mechanical shearing during handling and application. Quantitative analysis showed that topographic projections (columns) rather than recesses (pits) in the hydrogel surface achieved the highest efficiency of cell transfer. In order to address the crucial relevance of microbiological contamination to the success of wound grafting, the effect of iodine on several common bacterial pathogens was examined using an XTT+C(Q10) kinetic cell viability assay. Increasing concentrations of iodine initially stressed and after 0.5% v/v were subsequently bacteriocidal for Gram-negative Pseudomonas aeruginosa and Escherichia coli and Gram-positive Bacillus subtillis and Staphylococcus aureus. Slightly higher doses of iodine (approx 1-1.5% v/v) were required to kill HaCaT cells outright, but for both pro- and eukaryotes the major determinant of cytotoxicity was absolute dose rather than duration of exposure. Iodine delivered by the hydrogel at low concentration was bacteriostatic but not apparently cytotoxic to epithelial cells as measured by MTT end-point cell viability assay. Zone of inhibition studies confirmed that bacteriocidal quantities of neomycin, phenol red, and silver could also be delivered using the same hydrogel. This research suggests that grafting cell-based biological dressings to wounds using a topographically modified hydrogel dressing capable of simultaneous reducing the microbiological threat to a successful outcome may be a realistic clinical proposition.

Influence of serum on adult and fetal dermal fibroblast migration, adhesion, and collagen expression

The wound healing response to injury can be affected by many factors such as cell migration and extracellular matrix elaboration. The objective of this study was to examine the serum- and age-dependent effects on cell migration, adhesion, and collagen expression by skin fibroblasts. Dermal fibroblasts were isolated and plated with and without serum for up to 7 d. Cell migration was determined by quantitative image analysis, adhesion was quantified using a centrifugation assay, and collagen expression was assessed by PCR and immunohistochemical staining. Both adult and fetal fibroblasts migrated significantly faster in serum-containing medium compared to serum-free medium. There was no significant difference in migration between the two cell types in either serum-containing or serum-free medium. There was no significant difference in adhesion in the presence of serum, although there was a greater fraction of adherent fetal skin fibroblasts than adult fibroblasts in serum-free medium. Moreover, the adherent fraction of fetal fibroblasts in serum-free medium was not significantly different from that in serum-containing medium, suggesting that fetal skin fibroblasts possess serum-independent adhesion properties. Collagen mRNA expression was significantly up-regulated in serum-free compared to serum-containing medium for both cell types. With respect to collagen immunohistochemistry, both dermal fibroblast populations exhibited greater type I collagen compared to type III collagen staining. Quantitative assessment of collagen staining indicated significantly enhanced type I collagen secretion in the presence of serum by fetal skin fibroblasts. These findings suggest that intrinsic cellular characteristics may govern the observed differences in adult and fetal wound healing.