Phenotypic variation in the production of bioactive hepatocyte growth factor/scatter factor by oral mucosal and skin fibroblasts

Using Microfluidics to Align Matrix Architecture and Generate Chemokine Gradients Promotes Directional Branching in a Model of Epithelial Morphogenesis

The mechanical cue of fiber alignment plays a key role in the development of various tissues in the body. The ability to study the effect of these stimuli in vitro has been limited previously. Here, we present a microfluidic device capable of intrinsically generating aligned fibers using the microchannel geometry. The device also features tunable interstitial fluid flow and the ability to form a morphogen gradient. These aspects allow for the modeling of complex tissues and to differentiate cell response to different stimuli. To demonstrate the abilities of our device, we incorporated luminal epithelial cysts into our device and induced growth factor stimulation. We found the mechanical cue of fiber alignment to play a dominant role in cell elongation and the ability to form protrusions was dependent on cadherin-3. Together, this work serves as a springboard for future potential with these devices to answer questions in developmental biology and complex diseases such as cancers.

Role of Enzymic Antioxidants in Mediating Oxidative Stress and Contrasting Wound Healing Capabilities in Oral Mucosal/Skin Fibroblasts and Tissues

Unlike skin, oral mucosal wounds are characterized by rapid healing and minimal scarring, attributable to the "enhanced" healing properties of oral mucosal fibroblasts (OMFs). As oxidative stress is increasingly implicated in regulating wound healing outcomes, this study compared oxidative stress biomarker and enzymic antioxidant profiles between patient-matched oral mucosal/skin tissues and OMFs/skin fibroblasts (SFs) to determine whether superior oral mucosal antioxidant capabilities and reduced oxidative stress contributed to these preferential healing properties. Oral mucosa and skin exhibited similar patterns of oxidative protein damage and lipid peroxidation, localized within the lamina propria/dermis and oral/skin epithelia, respectively. SOD1, SOD2, SOD3 and catalase were primarily localized within epithelial tissues overall. However, SOD3 was also widespread within the lamina propria localized to OMFs, vasculature and the extracellular matrix. OMFs were further identified as being more resistant to reactive oxygen species (ROS) generation and oxidative DNA/protein damage than SFs. Despite histological evaluation suggesting that oral mucosa possessed higher SOD3 expression, this was not fully substantiated for all OMFs examined due to inter-patient donor variability. Such findings suggest that enzymic antioxidants have limited roles in mediating privileged wound healing responses in OMFs, implying that other non-enzymic antioxidants could be involved in protecting OMFs from oxidative stress overall.

Granulocyte macrophage-colony stimulating factor and keratinocyte growth factor control of early stages of differentiation of oral epithelium

Oral epithelial differentiation is known to be directed by underlying fibroblasts, but the responsible factor(s) have not been identified. We aimed here to identify fibroblast‐derived factors responsible for oral epithelial differentiation. Primary normal human oral keratinocytes and fibroblasts were isolated from healthy volunteers after informed consent (n = 5) and 3D‐organotypic (3D‐OT) cultures were constructed. Various growth factors were added at a range of 0.1‐100 ng/ml. 3D‐OTs were harvested after ten days and assessed histologically, by immunohistochemistry and the TUNEL method. Epithelium developed in 3D‐OT without fibroblasts showed an undifferentiated phenotype. Addition of granulocyte macrophage‐colony stimulating factor (GM‐CSF) induced expression of cytokeratin 13 in suprabasal cell layers. Admixture of GM‐CSF and keratinocyte growth factor (KGF) induced, in addition, polarization of epidermal growth factor (EGF) receptor and β1‐integrin to basal cell layer and collagen IV deposition. Terminal differentiation with polarization of TUNEL‐positive cells to superficial layers occurred only in the presence of fibroblasts in collagen gels either in direct contact or at distance from normal oral keratinocytes. Taken together, these results show that major aspects of oral epithelial differentiation are regulated by the synergic combination of GM‐CSF and KGF. However, the terminal stage seems to be controlled by other yet unidentified fibroblast‐derived diffusible factor(s).

Bisphosphonate-induced reactive oxygen species inhibit proliferation and migration of oral fibroblasts: A pathogenesis of bisphosphonate-related osteonecrosis of the jaw

BACKGROUND

The onset mechanism for bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been reported, with a focus on bone remodeling, biofilm formation, and epithelial cell proliferation and migration. However, the involvement of stromal cells, especially fibroblasts, in the oral cavity is unclear. Therefore, this study was focused on how bisphosphonates (BPs) affect orthotopic periodontal ligament fibroblasts from the viewpoint of oxidative stress compared with ectopically obtained fibroblasts.

METHODS

Normal human periodontal ligament fibroblasts (HPdLFs) and normal human dermal fibroblasts (NHDFs) were used to gain insight into the functional differences in sensitivity and reactions to BPs. Cell growth assay, measurement of reactive oxygen species (ROS) and nitric oxide (NO) production, and wound-healing assay in vitro were performed. Maxillary first molars were extracted in C57BL/6 mice and either BP, N-acetyl-cysteine (NAC), and BP or saline were administered.

RESULTS

BP-induced IC₅₀ values were significantly lower in HPdLFs (30.6 µM) than in NHDFs (109.7 µM). BP resulted in an increase in ROS, but not NO generation in HPdLFs. BPs also inhibited proliferation and migration of HPdLFs but not NHDFs, while the addition of a ROS inhibitor, NAC, reversed those inhibitions. A BRONJ mouse model in which BP was administered and then the tooth was extracted, impaired wound healing of the socket was observed. When NAC was administered before tooth extraction, wound healing was significantly improved.

CONCLUSION

These results suggest that BP causes fibroblasts obtained from the oral cavity but not from skin to generate ROS and that the subsequent ROS-mediated inhibition of fibroblast growth and migration definitely delays wound healing, thereby contributing to BRONJ pathogenesis.

Hepatocyte Growth Factor Mediates Enhanced Wound Healing Responses and Resistance to Transforming Growth Factor-β₁-Driven Myofibroblast Differentiation in Oral Mucosal Fibroblasts

Oral mucosal wounds are characterized by rapid healing with minimal scarring, partly attributable to the "enhanced" wound healing properties of oral mucosal fibroblasts (OMFs). Hepatocyte growth factor (HGF) is a pleiotropic growth factor, with potential key roles in accelerating healing and preventing fibrosis. HGF can exist as full-length or truncated (HGF-NK), NK1 and NK2 isoforms. As OMFs display elevated HGF expression compared to dermal fibroblasts (DFs), this study investigated the extent to which HGF mediates the preferential cellular functions of OMFs, and the influence of pro-fibrotic, transforming growth factor-β₁ (TGF-β₁) on these responses. Knockdown of HGF expression in OMFs by short-interfering RNA (siHGF) significantly inhibited OMF proliferative and migratory responses. Supplementation with exogenous TGF-β₁ also significantly inhibited proliferation and migration, concomitant with significantly down-regulated HGF expression. In addition, knockdown abrogated OMF resistance to TGF-β₁-driven myofibroblast differentiation, as evidenced by increased α-smooth muscle actin (α-SMA) expression, F-actin reorganisation, and stress fibre formation. Responses were unaffected in siHGF-transfected DFs. OMFs expressed significantly higher full-length HGF and NK1 levels compared to patient-matched DFs, whilst NK2 expression was similar in both OMFs and DFs. Furthermore, NK2 was preferentially expressed over NK1 in DFs. TGF-β₁ supplementation significantly down-regulated full-length HGF and NK1 expression by OMFs, while NK2 was less affected. This study demonstrates the importance of HGF in mediating "enhanced" OMF cellular function. We also propose that full-length HGF and HGF-NK1 convey desirable wound healing properties, whilst fibroblasts preferentially expressing more HGF-NK2 readily undergo TGF-β₁-driven differentiation into myofibroblasts.

MiR-9-5p promotes MSC migration by activating β-catenin signaling pathway

Mesenchymal stem cells (MSCs) have the potential to treat various tissue damages, but the very limited number of cells that migrate to the damaged region strongly restricts their therapeutic applications. Full understanding of mechanisms regulating MSC migration will help to improve their migration ability and therapeutic effects. Increasing evidence shows that microRNAs play important roles in the regulation of MSC migration. In the present study, we reported that miR-9-5p was upregulated in hepatocyte growth factor -treated MSCs and in MSCs with high migration ability. Overexpression of miR-9-5p promoted MSC migration, whereas inhibition of endogenous miR-9-5p decreased MSC migration. To elucidate the underlying mechanism, we screened the target genes of miR-9-5p and report for the first time that CK1α and GSK3β, two inhibitors of β-catenin signaling pathway, were direct targets of miR-9-5p in MSCs and that overexpression of miR-9-5p upregulated β-catenin signaling pathway. In line with these data, inhibition of β-catenin signaling pathway by FH535 decreased the miR-9-5p-promoted migration of MSCs, while activation of β-catenin signaling pathway by LiCl rescued the impaired migration of MSCs triggered by miR-9-5p inhibitor. Furthermore, the formation and distribution of focal adhesions as well as the reorganization of F-actin were affected by the expression of miR-9-5p. Collectively, these results demonstrate that miR-9-5p promotes MSC migration by upregulating β-catenin signaling pathway, shedding light on the optimization of MSCs for cell replacement therapy through manipulating the expression level of miR-9-5p.

MiR-221 and miR-26b Regulate Chemotactic Migration of MSCs Toward HGF Through Activation of Akt and FAK

The chemotactic migration of mesenchymal stem cells (MSCs) is fundamental for their use in cell-based therapies, but little is known about the molecular mechanisms that regulate their directed migration. MicroRNAs (miRNAs) participate in the regulation of a large variety of cellular processes. However, their roles in regulating the responses of MSCs to hepatocyte growth factor (HGF) remain elusive. Here, we found that microRNA-221 (miR-221) and microRNA-26b (miR-26b) were upregulated in MSCs subjected to HGF. Overexpression of miR-221 or miR-26b enhanced MSC migration through activation of PI3K/Akt signaling. Phosphatase and tensin homolog deleted on chromosome ten (PTEN) was identified as a potential target of miR-221 and miR-26b; overexpression of miR-221 or miR-26b decreased PTEN expression at both mRNA and protein levels. Overexpression of miR-221 or miR-26b in MSCs increased the phosphorylation of focal adhesion kinase (FAK), a downstream effector of PTEN, which regulates cell migration through assembly and distribution of focal adhesions (FAs), and more dot-like FAs were localized at the periphery of these cells. Altering miR-221 or miR-26b expression influenced the directed migration of MSCs toward HGF. Inhibition of miR-221 or miR-26b suppressed the phosphorylation of Akt and FAK and upregulated PTEN expression, which was partly restored by HGF treatment. Collectively, these results demonstrate that miR-221 and miR-26b participate in regulating the chemotactic response of MSCs toward HGF.

Oral Mucosal Lamina Propria-Progenitor Cells Exert Antibacterial Properties via the Secretion of Osteoprotegerin and Haptoglobin

The oral cavity possesses a diverse microflora, yet recurrent infections within healthy individuals are rare. Wound healing within the buccal mucosa is preferential, potentially because of the presence of oral mucosal lamina propria-progenitor cells (OMLP-PCs). In addition to their multipotency, OMLP-PCs demonstrate potent immunosuppressive properties. The present study investigated whether OMLP-PCs possess antibacterial properties, directly interacting with microorganisms and contributing to the maintenance of a balanced oral microflora. Gram-positive and -negative bacteria were cocultured with OMLP-PCs, buccal mucosal fibroblasts, or their respective conditioned media (CM). Bacterial growth was significantly inhibited when cocultured with OMLP-PCs or their CM. No antibacterial activity was apparent within the fibroblasts. Analysis of the OMLP-PC CM indicated constitutive secretion of osteoprotegerin (OPG) and haptoglobin (Hp). Exposure of the bacteria to OPG or Hp demonstrated their differential antibacterial properties, with neutralization/blocking studies confirming that the growth of Gram-positive bacteria was partially restored by neutralizing OPG within OMLP-PC CM; blocking Hp restored the growth of Gram-negative bacteria. The present study demonstrates, for the first time, the broad-spectrum antibacterial properties of OMLP-PCs. We report the direct and constitutive antibacterial nature of OMLP-PCs, with retention of this effect within the CM suggesting a role for soluble factors such as OPG and Hp. Knowledge of the immunomodulatory and antibacterial properties of these cells could potentially be exploited in the development of novel cell- or soluble factor-based therapeutics for the treatment of infectious diseases such as pneumonia or ailments such as chronic nonhealing wounds.

SIGNIFICANCE

Oral mucosal lamina propria-progenitor cells (OMLP-PCs) are a cell source with known immunomodulatory properties. The present report demonstrates the novel finding that OMLP-PCs possess potent antibacterial properties, halting the growth of Gram-positive and -negative bacteria through the secretion of soluble factors. OMLP-PCs constitutively secrete osteoprotegerin (OPG) and haptoglobin (Hp) at levels high enough to exert antibacterial action. OPG, a glycoprotein not previously known to be antibacterial, can suppress Gram-positive bacterial growth. Hp is only active against Gram-negative microorganisms. These findings indicate that OMLP-PCs could offer great potential in the development of novel cell- or soluble factor-based therapies for the treatment of infectious illness, such as bacterial pneumonia, through systemic infusion and of chronic wounds through local administration.

Fibroblast heterogeneity and its implications for engineering organotypic skin models in vitro

Advances in cell culture methods, multidisciplinary research, clinical need to replace lost skin tissues and regulatory need to replace animal models with alternative test methods has led to development of three dimensional models of human skin. In general, these in vitro models of skin consist of keratinocytes cultured over fibroblast-populated dermal matrices. Accumulating evidences indicate that mesenchyme-derived signals are essential for epidermal morphogenesis, homeostasis and differentiation. Various studies show that fibroblasts isolated from different tissues in the body are dynamic in nature and are morphologically and functionally heterogeneous subpopulations. Further, these differences seem to be dictated by the local biological and physical microenvironment the fibroblasts reside resulting in "positional identity or memory". Furthermore, the heterogeneity among the fibroblasts play a critical role in scarless wound healing and complete restoration of native tissue architecture in fetus and oral mucosa; and excessive scar formation in diseased states like keloids and hypertrophic scars. In this review, we summarize current concepts about the heterogeneity among fibroblasts and their role in various wound healing environments. Further, we contemplate how the insights on fibroblast heterogeneity could be applied for the development of next generation organotypic skin models.

Extracellular matrix components of oral mucosa differ from skin and resemble that of foetal skin

OBJECTIVE

Wounds of both the oral mucosa and early-to-mid gestation foetuses have a propensity to heal scarless. Repair of skin wounds in adults, however, regularly results in scar formation. The extracellular matrix (ECM) plays an important role in the process of healing. The fate of scarless or scar forming healing may already be defined by the ECM composition, prior to wounding. In this study, the presence of several ECM components in oral mucosa (palatum) and skin was investigated.

DESIGN

Immunohistochemical stainings of different ECM components were performed on skin, obtained from abdominal dermolipectomy surgery, and oral mucosa, derived after pharynx reconstruction.

RESULTS

Expression of fibronectin, its splice variant ED-A, and chondroitin sulphate was elevated in oral tissue, whereas elastin expression was higher in skin. Tenascin-C, hyaluronic acid, biglycan, decorin, and syndecan-1 were expressed at similar levels in both tissues. Oral mucosa contained more blood vessels than skin samples. Finally, oral keratinocytes proliferated more, while dermal keratinocytes demonstrated higher differentiation.

CONCLUSIONS

Comparing ECM components of the skin and oral mucosa coincides with differences earlier observed between foetal and adult skin, and this might indicate that some ECM components are involved in the mode of repair.

Detrimental dermal wound healing: what can we learn from the oral mucosa?

Wounds in adults are frequently accompanied by scar formation. This scar can become fibrotic due to an imbalance between extracellular matrix (ECM) synthesis and ECM degradation. Oral mucosal wounds, however, heal in an accelerated fashion, displaying minimal scar formation. The exact mechanisms of scarless oral healing are yet to be revealed. This review highlights possible mechanisms involved in the difference between scar-forming dermal vs. scarless oral mucosal wound healing. Differences were found in expression of ECM components, such as procollagen I and tenascin-C. Oral wounds contained fewer immune mediators, blood vessels, and profibrotic mediators but had more bone marrow-derived cells, a higher reepithelialization rate, and faster proliferation of fibroblasts compared with dermal wounds. These results form a basis for further research that should be focused on the relations among ECM, immune cells, growth factors, and fibroblast phenotypes, as understanding scarless oral mucosal healing may ultimately lead to novel therapeutic strategies to prevent fibrotic scars.

Alternatives for animal wound model systems

In this chapter a review of animal model systems already being utilized to study normal and pathologic wound healing is provided. We also go into details on alternatives for animal wound model systems. The case is made for limitations in the various approaches. We also discuss the benefits/limitations of in vitro/ex vivo systems bringing everything up to date with our current work on developing a cell-based reporter system for diabetic wound healing.

Neural differentiation of mesenchymal stem cells influences chemotactic responses to HGF

Recently, mesenchymal stem cells (MSCs) have been extensively used for cell-based therapies in neuronal degenerative disease. Although much effort has been devoted to the delineation of factors involved in the migration of MSCs, the relationship between the chemotactic responses and the differentiation status of these cells remains elusive. Here, we report that MSCs in varying neural differentiation states display different chemotactic responses to hepatocyte growth factor (HGF): first, the number of chemotaxing MSCs and the optimal concentrations of HGF that induced the peak migration varied greatly; second, time-lapse video analysis showed that MSCs in certain differentiation state migrated more efficiently toward HGF; third, the phosphorylation levels of Akt, ERK1/2, SAPK/JNK, and p38MAPK were closely related to the differentiation levels of MSCs subjected to HGF; and finally, although inhibition of ERK1/2 signaling significantly attenuated HGF-stimulated transfilter migration of both undifferentiated and differentiating MSCs, abolishment of PI3K/Akt, p38MAPK, or SAPK/JNK signaling only decreased the number of migrated cells in certain differentiation state(s). Blocking of PI3K/Akt or MAPK signaling impaired the migration efficiency and/or speed, the extent of which depends on the cell differentiation states. Meanwhile, F-actin rearrangement, which is essential for MSCs chemotaxis, was induced by HGF, and the time points of cytoskeletal reorganization were different among these cells. Collectively, these results demonstrate that neural differentiation of MSCs influences their chemotactic responses to HGF: MSCs in varying differentiation states possess different migratory capacities, thereby shedding light on optimization of the therapeutic potential of MSCs to be employed for neural regeneration after injury.

‘Young’ Oral Fibroblasts Are Geno/Phenotypically Distinct

Wound healing within the oral mucosa results in minimal scar formation compared with wounds within the skin. We have recently demonstrated distinct differences in the aging profiles of cells (oral mucosal and patient-matched skin fibroblasts) isolated from these tissues. We hypothesized that the increased replicative potential of oral mucosal fibroblasts may confer upon them preferential wound-healing capacities. Passage-matched early cultures of oral mucosal fibroblasts and skin fibroblasts demonstrated distinct gene expression profiles, with several genes linked to wound healing/tissue repair. This was related to an increased ability of the ‘replicatively younger’ oral mucosal fibroblasts to repopulate a wound space and reorganize their surrounding extracellular matrix environment, key activities during the wound-healing process. We conclude that oral mucosal fibroblasts exhibit a preferential healing response in vivo, due to their ‘replicatively younger’ phenotype when compared with that of patient-matched skin fibroblasts.

A multipotent neural crest-derived progenitor cell population is resident within the oral mucosa lamina propria

Wounds within the oral mucosa, similarly to fetal wounds, exhibit rapid healing with reduced scarring. We hypothesized that a progenitor population resident within the oral mucosal lamina propria (OMLP) contributes to this preferential healing. Progenitor cells (PC) were reliably isolated from the OMLP by differential adhesion to fibronectin. Isolated colonies originating from a single cell demonstrated a rapid initial phase of proliferation, completing in excess of 50 population doublings (PDs) before entering cellular senescence. These data were supported by the expression of active telomerase within both developing colonies and expanded clones as assessed by immunocytochemistry (ICC) and the quantitative telomeric repeat amplification protocol. FACS analysis confirmed expression of the stem cell markers CD44, CD90, CD105, and CD166, but negative expression of CD34 and CD45 ruling out a hematopoietic or fibrocyte origin for these progenitors. A neural crest origin was confirmed by increased colony-forming efficiency (CFE) in the presence of Jagged 1 and the expression of a number of neural crest markers within the developing colonies by ICC and serially passaged clones by Western blotting. The multipotency of this novel PC population was demonstrated by differentiation of the cells down both mesenchymal (chondrogenic, osteoblastic, and adipogenic) and neuronal (neuron and Schwann-like cells) cell lineages. This article reports for the first time, the isolation and characterization of a novel, clonally derived PC population resident within the OMLP. The attributes of this adult stem cell (ASC) population and its accessibility lends itself to future therapeutic applications.

Increased Oral Fibroblast Lifespan Is Telomerase-independent

Oral mucosal wound-healing is characterized by rapid re-epithelialization and remodeling, with minimal scar formation. This may be attributed to the distinct phenotypic characteristics of the resident fibroblasts. To test this hypothesis, we investigated patient-matched oral mucosal and skin fibroblasts. Compared with skin fibroblasts, oral mucosal fibroblasts had longer proliferative lifespans, underwent more population doublings, and experienced senescence later, which was directly related to longer telomere lengths within oral mucosal fibroblasts. The presence of these longer telomeres was independent of telomerase expression, since both oral oral mucosal fibroblasts and skin fibroblasts were negative for active telomerase, as assessed according to the Telomeric Repeat Amplification Protocol. This study has demonstrated that, compared with skin fibroblasts, oral mucosal fibroblasts are ‘younger’, with a more embryonic/fetal-like phenotype that may provide a notable advantage for their ability to repair wounds in a scarless fashion.

Non-epithelial oral mucosal progenitor cell populations

This review considers the potential existence and role of stem or progenitor cell populations within the non-epithelial tissues of the oral mucosa. Currently, there is little published evidence supporting this hypothesis; however, because of the similarities in structure and function of the oral mucosa and skin, findings within the dermis of the skin may potentially reflect the situation within the oral mucosa. Over recent years, the identification of the skin as a local reservoir of adult stem cell populations and the idea that multipotent cell populations exist within the dermal tissues of skin has gained increasing credibility. Indeed, numerous multipotent progenitor cells have been identified within the dermis and resident appendages, all capable of differentiating into multiple cell lineages. Furthermore, a number of these cell populations have been implicated in the repair of these tissues following injury. There is increasing evidence suggesting that such populations of progenitor cells may also reside within the lamina propria. In this respect, the ability to isolate large numbers of multipotent progenitor cells from a tissue which when biopsied heals without a scar would be of great interest scientifically and commercially, particularly with respect to future therapeutic applications and the developing discipline of tissue engineering.

The molecular and clinical impact of hepatocyte growth factor, its receptor, activators, and inhibitors in wound healing

Wound healing involves a number of cellular and molecular events, many of which are controlled by soluble growth factors. In the process of healing, hepatocyte growth factor, a cytokine known to act as mitogen, motogen, and morphogen, has been postulated to play multiple roles during several stages of this complex biological process. Produced primarily by stromal fibroblasts, hepatocyte growth factor regulates angiogenesis, vascular permeability, cell migration, matrix deposition and degradation, and other biological processes. The current article discusses recent progress in understanding the multiple roles played by this growth factor in tissue repair.

Functional expression of HGF and HGF receptor/c-met in adult human mesenchymal stem cells suggests a role in cell mobilization, tissue repair, and wound healing

Human mesenchymal stem cells (hMSC) are adult stem cells with multipotent capacities. The ability of mesenchymal stem cells to differentiate into many cell types, as well as their high ex vivo expansion potential, makes these cells an attractive therapeutic tool for cell transplantation and tissue engineering. hMSC are thought to contribute to tissue regeneration, but the signals governing their mobilization, diapedesis into the bloodstream, and migration into the target tissue are largely unknown. Here we report that hepatocyte growth factor (HGF) and the cognate receptor HGFR/c-met are expressed in hMSC, on both the RNA and the protein levels. The expression of HGF was downregulated by transforming growth factor beta. HGF stimulated chemotactic migration but not proliferation of hMSC. Therefore the HGF/c-met signaling system may have an important role in hMSC recruitment sites of tissue regeneration. The controlled regulation of HGF/c-met expression may be beneficial in tissue engineering and cell therapy employing hMSC.

Early cellular changes of human mesenchymal stem cells and their interaction with other cells

Cell-to-cell interactions between human mesenchymal stem cells and potential adjacent cells such as endothelial cells, dermal fibroblasts, and epidermal keratinocytes was investigated. A modified dual Boyden chamber assay using 8-microm pores revealed a more powerful chemotactic cell migration of human mesenchymal stem cells toward human epidermal keratinocytes than other cells, such as umbilical artery endothelial cells and dermal fibroblasts, during 16 hours of incubation (336.2+/-52.33, 36.0+/-11.20, and 62.7+/-18.16, cells/field, respectively, p<0.01; comparison between endothelial cells and keratinocytes, and fibroblasts and keratinocytes). Scanning electron microscopy showed human mesenchymal stem cell migration through the pores, with endothelial cells, fibroblasts, or keratinocytes in the lower chambers. Mesenchymal stem cell ultrastructural changes occurred, including a larger euchromatin nucleus, when the cells were placed in medium containing 10 percent fetal bovine serum, whereas basic fibroblast growth factor maintained the immature cell morphology for 4 days. Monolayer coculture also showed human mesenchymal stem cell changes in ultrastructural morphology in the vicinity of the epidermal keratinocytes. These data suggest that human mesenchymal stem cells may interact with human epidermal keratinocytes to accelerate wound healing and coverage.

Oral fibroblasts produce more HGF and KGF than skin fibroblasts in response to co-culture with keratinocytes

The production of hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) in subepithelial fibroblasts from buccal mucosa, periodontal ligament, and skin was determined after co-culture with keratinocytes. The purpose was to detect differences between the fibroblast subpopulations that could explain regional variation in epithelial growth and wound healing. Normal human fibroblasts were cultured on polystyrene or maintained in collagen matrix and stimulated with keratinocytes cultured on membranes. The amount of HGF and KGF protein in the culture medium was determined every 24 h for 5 days by ELISA. When cultured on polystyrene, the constitutive level of KGF and HGF in periodontal fibroblasts was higher than the level in buccal and skin fibroblasts. In the presence of keratinocytes, all three types of fibroblasts in general increased their HGF and KGF production 2-3 times. When cells were maintained in collagen, the level of HGF and KGF was decreased mainly in skin cultures. However, in oral fibroblasts, induction after stimulation was at a similar level in collagen compared to on polystyrene. Skin fibroblasts maintained in collagen produced almost no HGF whether with or without stimulation. The results demonstrate that the secretion of KGF and HGF in both unstimulated fibroblasts and in fibroblasts co-cultured with keratinocytes is dependent on the type of fibroblasts. In general, the periodontal fibroblasts had the highest level of cytokine production. This high level of growth factor production may influence the proliferation and the migration of junctional epithelium and thereby influence the development of periodontal disease.

Differences in motility pattern between human buccal fibroblasts and periodontal and skin fibroblasts

Migration of fibroblasts from surrounding normal tissue into the wound bed is an important requirement for successful wound healing. This study investigated the motility pattern of buccal, periodontal and skin fibroblasts to determine whether differences in the wound healing efficiency at these sites can be explained by differences in the motile behavior of their respective fibroblast populations. The migratory characteristics were studied in a two-dimensional culture system. The migration of single cells was time-lapse video recorded at intervals of 15 min for a period of 6 h using a computer-assisted microscope work-station. For evaluation of cell morphology, cell contours were recognized semiautomatically and used for determination of cell area, cell spreading and number and length of processes. We found that the cellular displacement of the buccal fibroblasts was only approximately 50% of the cellular displacement of periodontal and skin fibroblasts. The decreased cellular displacement of the buccal fibroblasts was found to be due to both lower cellular speed and less persistence in direction. The buccal fibroblasts also displayed smaller areas and longer processes. The differences in cellular morphology and motility pattern amongst the three fibroblast types could not be explained by differences in secretion of extracellular matrix components and are therefore believed to reflect phenotypic differences amongst fibroblast subpopulations.