Autologous keratinocyte suspensions accelerate epidermal wound healing in pigs

In Vivo Engineering and Transplantation of Axially Vascularized and Epithelialized Flaps in Rats

The arteriovenous loop (AVL) model allows the in vivo engineering of axially vascularized flaps, the so-called AVL flaps. Although AVL flaps can be transplanted microsurgically to cover tissue defects, they lack an epithelial layer on the surface. Therefore, the objective of this study was to engineer axially vascularized AVL flaps with an accompanying epithelial layer for local defect reconstruction. In this study, AVLs were established in 20 male Lewis rats. Minimally invasive injection of keratinocytes onto the surface of the AVL flaps was performed on postoperative day (POD) 21. AVL flaps were explanted from 12 rats on POD 24 or POD 30, then the epithelium formed by the keratinocytes on the surface of the flaps was evaluated using immunofluorescence staining. In six other rats, the AVL flap was locally transposed to cover a critical defect in the rats' leg on POD 30 and explanted for analysis on POD 40. In two control rats, sodium chloride was applied instead of keratinocytes. These control flaps were also transplanted on POD 30 and explanted on POD 40. Our results revealed that 3 days after keratinocyte application, a loose single-layered epithelium was observed histologically on the AVL flaps surface, whereas after 9 days, a multilayered and structured epithelium had grown. The epithelium on the transplanted AVL flaps showed its physiological differentiation when being exposed to an air-liquid interface. Histologically, a layered epithelium identical to the rats' regular skin was formed. In the sodium chloride control group, no epithelium had been grown. This study clearly demonstrates that axially vascularized AVL flaps can be processed in the subcutaneous chamber by minimally invasive injection of keratinocytes. Thus, AVL flaps with an intact epithelial layer were engineered and could be successfully transplanted for local defect coverage in a small animal model.

A Randomized Controlled Study Comparing the Efficacy of Autologous Smashed Follicular Dermal Graft and Epidermal Cell Suspension versus Normal Saline Dressing in the Treatment of Chronic Nonhealing Trophic Ulcers in Patients with Hansen's Disease

Background

Trophic ulcers remain the most common reason for hospitalization in patients with Hansen's disease. With the introduction of new therapeutic regimens, leprosy can now be cured. However, complications of the disease, such as sensory loss, muscle palsy, absorption of extremities, and recurrent ulcers, still lead to substantial morbidity. The management of patients with trophic ulcers and their consequences is difficult, because it is a recurrent and recalcitrant problem.

Aims

To evaluate the efficacy of autologous smashed follicular dermal graft and epidermal cell suspension (ECS) in the treatment of chronic nonhealing trophic ulcers in patients with Hansen's disease and to compare its efficacy with normal saline dressing.

Materials and Methods

A total of 46 chronic nonhealing trophic ulcers were randomized into two groups (23 ulcers in each): Ulcers in Group A were treated with autologous smashed follicular dermal graft and ECS; ulcers in Group B were treated with normal saline dressings. Ulcers were assessed based on the rate of ulcer size reduction at every week till 12 weeks and then once a month till the sixth month.

Results

All 23 (100%) ulcers in Group A had healed within the study period of six months, whereas only 14 (60.9%) ulcers had healed in Group B. Nine (39.1%) ulcers in Group B had not healed even at the end of six months. All 23 (100%) ulcers in Group A had healed within eight weeks, which was statistically significant, P value <0.05.

Conclusion

Trophic ulcers heal faster by autologous smashed follicular dermal graft and ECS, with good results of re-epithelialization of the ulcer bed than by normal saline dressing.

Stem and Somatic Cell Monotherapy for the Treatment of Diabetic Foot Ulcers: Review of Clinical Studies and Mechanisms of Action

Diabetic foot ulcer (DFU) is one of the most severe complications of diabetes mellitus, often resulting in a limb amputation. A cell-based therapy is a highly promising approach for an effective DFU treatment. However, there is no consensus regarding the most effective cell type for DFU treatment. Various cell types contribute to chronic wound healing via different mechanisms. For example, application of keratinocytes can stimulate migration of native keratinocytes from the wound edge, while mesenchymal stem cells can correct limb ischemia. To assess the effectiveness of a certain cell type, it should be administered as a monotherapy without other substances and procedures that have additional therapeutic effects. In the present review, we described therapeutic effects of various cells and provided an overview of clinical studies in which stem and somatic cell-based therapy was administered as a monotherapy. Topical application of somatic cells contributes to DFU healing only, while injection of mesenchymal stem cells and mononuclear cells can break a pathophysiological chain leading from insufficient blood supply to DFU development. At the same time, the systemic use of mesenchymal stem cells carries greater risks. Undoubtedly, cell therapy is a potent tool for the treatment of DFU. However, it is vital to conduct further high-quality clinical research to determine the most effective cell type, dosage and way of administration for DFU treatment. Ischemia, neuropathy and neuro-ischemia are underlying factors of diabetic foot ulcer. Stem and somatic cells monotherapy can improve chronic wound healing via different mechanisms.

Autologous non-cultured keratinocyte cell suspension in non-healing diabetic ulcers: A preliminary study

Background:

Diabetic ulcers are a common morbidity associated with poorly controlled glycemic status. Most patients often have neuropathy and vasculopathy as the etiology behind such ulcers. These factors not only lead to poor wound healing but also nonhealing ulcers. Nonhealing ulcers pose therapeutic challenges as they are usually not amenable to be treated with simple wound care and hence require newer modalities to effectively cure this condition that leads to a plethora of poor health outcomes. This study was conducted to see the effect of autologous noncultured keratinocyte cell suspension in chronic nonhealing diabetic ulcers that failed to normal wound care.

Material and Methods:

It was an observational pilot study. A total of 05 patients with nonhealing ulcers, attending the tertiary care teaching hospital in North India, were included in the study. Inclusion criteria was type 2 DM with more than 5 years duration of diabetes mellitus and glycated hemoglobin (HbA1c) <9 g%. History was taken in detail; name, age, sex, address, duration of disease and various other treatments taken from outside were noted; and size of ulcer was recorded as per Proforma.

Results:

A total of 5 patients were enrolled in the study, three (60%) and two (40%) patients were male and female, respectively. Three (60%) patients were habitual for tobacco use. Mean age of patients was 45 ± 6.51 years. Mean duration of ulcers was 4.8 ± 1.48 months. Area of ulcers ranged from 31.2 to 122.2 cm². Majority of cases, three (60%) of diabetic foot ulcers, were improved at 9–12 weeks and remaining two cases with large size of ulcer were healed at 13–16 weeks and 17–20 weeks, respectively. Majority (80%) of patients revealed >50% reduction in the size of ulcer within 2 weeks.

Conclusion:

Noncultured keratinocytes are useful in healing of nonhealing diabetic ulcer.

Cell therapy for severe burn wound healing

Cell therapy has emerged as an important component of life-saving procedures in treating burns. Over past decades, advances in stem cells and regenerative medicine have offered exciting opportunities of developing cell-based alternatives and demonstrated the potential and feasibility of various stem cells for burn wound healing. However, there are still scientific and technical issues that should be resolved to facilitate the full potential of the cellular devices. More evidence from large, randomly controlled trials is also needed to understand the clinical impact of cell therapy in burns. This article aims to provide an up-to-date review of the research development and clinical applications of cell therapies in burn wound healing and skin regeneration.

Cultured Human Epidermis Combined With Meshed Skin Autografts Accelerates Epithelialization and Granulation Tissue Formation in a Rat Model

INTRODUCTION

As the take rate of cultured epidermal autografts in burn wound treatment is variable, widely expanded meshed auto skin grafts are often used in combination with cultured epidermal autograft to increase the take rate and achieve definitive wound coverage. However, a long time (3-4 weeks) required to prepare a cultured epidermis sheet is a disadvantage. Allogeneic cultured epidermis can be prepared in advance and cryopreserved to be used in combination with auto meshed skin grafts for treating third-degree burns. Nevertheless, the human cultured epidermis (hCE) has not been proved to accelerate wound healing after meshed skin grafting. Here, we investigated the effect of hCE on wound healing in a rat model of meshed skin grafting.

MATERIALS AND METHODS

Human cultured epidermis was prepared from human neonatal foreskin and assessed by the release of growth factors into the culture medium using enzyme-linked immunosorbent assay. Skin wounds were inflicted on male F344 rats and treated by the application of widely meshed (6:1 ratio) autogenous skin grafts with or without hCE (n = 8 rats per group). Wound area, neoepithelium length, granulation tissue formation, and neovascularization were evaluated on day 7 postgrafting.

RESULTS

Human cultured epidermis secreted IL-1α, Basic fibroblast growth factor, platelet-derived growth factor-AA, TGF-α, TGF-β1, and vascular endothelial growth factor in vitro. In rats, hCE accelerated wound closure (P = 0.003), neoepithelium growth (P = 0.019), and granulation tissue formation (P = 0.043), and increased the number of capillaries (P = 0.0003) and gross neovascularization area (P = 0.008) compared with the control group.

CONCLUSIONS

The application of hCE with meshed grafts promoted wound closure, possibly via secretion of growth factors critical for cell proliferation and migration, suggesting that hCE can enhance the healing effect of widely expanded skin autografts.

Proof of concept of a new autologous skin substitute for the treatment of deep wounds in dogs

Autologous skin grafts are effective for the repair of large skin wounds, but the availability of large amounts of skin is often limited. Through bioengineering, several autologous skin substitutes have been developed for use in human clinical practice. However, few skin substitutes are available for use in animals. The aim of this study was to develop and assess an engineered autologous skin substitute for the treatment of deep wounds in veterinary medicine. Canine keratinocytes and fibroblasts were isolated after double enzyme digestion from 8mm punch biopsies from four healthy Beagle dogs. Skin substitutes were constructed on a fibrin-based matrix and grafting capacity was assessed by xenografting in six athymic mice. Bioengineered autologous skin was assessed clinically in two dogs with large deep skin wounds. The canine skin construct was ready for use within 12-14days after the initial biopsy specimens were obtained. Grafting capacity in this model was confirmed by successful grafting of the construct in athymic mice. In both dogs, grafts were established and permanent epithelialisation occurred. Histological studies confirmed successful grafting. This full thickness skin substitute developed for the management of large skin defects in dogs appears to be a safe and useful tool for clinical veterinary practice. Further studies are needed to validate its efficacy for the treatment of deep wounds.

A Novel Bioreactor Microcarrier Cell Culture System for High Yields of Proliferating Autologous Human Keratinocytes

Rapid and efficient resurfacing of various skin defects by autologous keratinocyte transplantation is significant in skin wound healing. We developed a novel bioreactor microcarrier cell culture system (Bio-MCCS) to produce autologous human keratinocytes on a large scale. In this Bio-MCCS we used porcine gelatin microbeads as microcarriers for autolgous keratinocytes and spinning bottles as fermentation tanks. First, the microbeads were modified by culturing them with autologous dermal fibroblasts that were subsequently killed when they proliferated to confluence on the microbeads. We then performed the Bio-MCCS by expanding ketatinocytes on the microbeads in spinning bottles at 37°C, 5% CO2. Our results showed that keratinocytes rapidly attached to and actively proliferated on the modified microbeads in the Bio-MCCS, achieving high cell densities on the modified microbeads (MTT assay and PI staining). Keratinocytes cultured on the modified microbeads in the Bio-MCCS remained proliferating potentials as shown by positive PCNA staining and BrdU labeling. In contrast, keratinocytes cultured on nonmodified microbeads in the Bio-MCCS proliferated slowly, rapidly ceased to proliferate, and finally dislodged from the microbeads. When removed from the Bio-MCCS and cultured under static conditions, keratinocytes were able to leave the modified microbeads and formed a multilayered epidermal equivalent on the culture surfaces. While stored at room temperature, keratinocytes remained at higher viabilities on the modified microbeads when compared to those on nonmodified microbeads. The achievement of high yields of proliferating autologous keratinocytes by this Bio-MCCS offers a practical potential of resurfacing various skin defects by direct administration of autologous keratinocyte microbeads on various skin defects.

Bioreactor Microcarrier Cell Culture System (Bio-MCCS) for Large-Scale Production of Autologous Melanocytes

Restoration of cutaneous pigmentation can be achieved in stable vitiligo by autologous cultured melanocyte transplantation. It was the goal of this study to construct a bioreactor microcarrier cell culture system (Bio-MCCS) to produce autologous melanocytes in large scale. In this Bio-MCCS, porcine gelatin microbeads were used as microcarriers, spinning bottle as fermented tank. Autologous melanocytes were able to attach to and proliferate on the gelatin microbeads in serum-free melanocyte medium in the Bio-MCCS, reaching up to 24-fold the cells seeded on day 15 (MTT assay). These autologous melanocytes cultured on gelatin microbeads could leave the microbeads and proliferate on the bottom of tissue culture flasks. Although Pluronic F68 has been widely used to protect animal cells from hydrodynamic stress in animal cell bioreactors, Pluronic F68 at a concentration of 0.25–1.0% showed no significant protective effects on the autologous melanocytes cultured on the microbeads and subjected to mechanical stress in the Bio-MCCS. This Bio-MCCS using porcine gelatin microbeads as microcarriers enabled large-scale production of autologous mela-nocytes, offering a potential treatment for large-area stable vitiligo by direct administration of the melanocytes cultured on the gelatin microbeads to the vitiliginous site.

Advances in drug delivery systems (DDSs) to release growth factors for wound healing and skin regeneration

Current advances in novel drug delivery systems (DDSs) to release growth factors (GFs) represent a great opportunity to develop new therapies or enhance the effectiveness of available medical treatments. These advances are particularly relevant to the field of regenerative medicine, challenging healthcare issues such as wound healing and skin repair. To this end, biocompatible biomaterials have been extensively studied to improve in vivo integration of DDSs, to enhance the bioactivity of the released drugs and to deliver bioactive molecules in a localised and controlled manner. Thus, this review presents an overview of DDSs to release GFs for skin regeneration, particularly emphasising on (i) polymeric micro and nanospheres, (ii) lipid nanoparticles, (iii) nanofibrous structures, (iv) hydrogels and (v) scaffolds. In addition, this review summarises the current animal models available for studying wound healing and the clinical trials and marketed medications based on GF administration indicated for chronic wound treatment.

FROM THE CLINICAL EDITOR

Chronic wounds currently pose a significant burden worldwide. With advances in science, novel drug delivery systems have been developed for growth factors delivery. In this comprehensive review, the authors highlighted current drug delivery systems for the enhancement of wound healing and their use in clinical settings.

CCN2 is transiently expressed by keratinocytes during re-epithelialization and regulates keratinocyte migration in vitro by the ras-MEK-ERK signaling pathway

BACKGROUND

CCN2 (previously known as connective tissue growth factor) is a multifunctional matricellular protein that has numerous effects on cell life and cell interactions with the connective tissue. Although the importance of CCN2 for the fibrotic process in wound healing has been well studied, the involvement of CCN2 in keratinocyte function has not yet been explored. Therefore, the aim of the present study was to investigate the role of CCN2 in the epidermis during wound healing.

MATERIALS AND METHODS

Immunohistochemistry was done on sections from full-thickness porcine wounds. The effect of CCN2 on the migration of cultured human keratinocytes exposed to scratch wounds, the effect on phosphorylation of extracellular signal-related kinases (ERK), and the effect of adding inhibitors to the ERK/mitogen-activated protein kinase pathway to human keratinocytes were studied.

RESULTS

The CCN2 protein was transiently expressed in vivo at the leading keratinocyte edge during re-epithelialization of full-thickness porcine wounds. In vitro, exogenous addition of CCN2 to human keratinocyte cultures regulated keratinocyte migration and resulted in phosphorylation of ERK. The addition of inhibitors of ERK/mitogen-activated protein kinase counteracted the effect of CCN2 on migration.

CONCLUSIONS

CCN2 was transiently expressed at the leading keratinocyte edge in vivo. The biologic importance of this was supported in vitro, because CCN2 regulated human keratinocyte migration through activation of the Ras-mitogen-activated protein kinase kinase-ERK signal transduction pathway.

Autologous keratinocyte suspension in platelet concentrate accelerates and enhances wound healing - a prospective randomized clinical trial on skin graft donor sites: platelet concentrate and keratinocytes on donor sites

Background

Wound healing involves complex mechanisms, which, if properly chaperoned, can enhance patient recovery. The abilities of platelets and keratinocytes may be harnessed in order to stimulate wound healing through the formation of platelet clots, the release of several growth factors and cytokines, and cell proliferation. The aim of the study was to test whether autologous keratinocyte suspensions in platelet concentrate would improve wound healing. The study was conducted at the Lausanne University Hospital, Switzerland in 45 patients, randomized to three different topical treatment groups: standard treatment serving as control, autologous platelet concentrate (PC) and keratinocytes suspended in autologous platelet concentrate (PC + K). Split thickness skin graft donor sites were chosen on the anterolateral thighs of patients undergoing plastic surgery for a variety of defects. Wound healing was assessed by the duration and quality of the healing process. Pain intensity was evaluated at day five.

Results

Healing time was reduced from 13.9 ± 0.5 days (mean ± SEM) in the control group to 7.2 ± 0.2 days in the PC group (P < 0.01). An addition of keratinocytes in suspension further reduced the healing time to 5.7 ± 0.2 days. Pain was reduced in both the PC and PC + K groups. Data showed a statistically detectable advantage of using PC + K over PC alone (P < 0.01).

Conclusion

The results demonstrate the positive contribution of autologous platelets combined with keratinocytes in stimulating wound healing and reducing pain. This strikingly simple approach could have a significant impact on patient care, especially critically burned victims for whom time is of the essence.

Clinical trial registry information

Protocol Record Identification Number: 132/03

Registry URL: http://www.clinicaltrials.gov

Keratinocytes in the treatment of severe burn injury: an update

Burns are among the most life-threatening physical injuries, in which fast wound closure is crucial. The surgical burn care has evolved considerably throughout the past decennia resulting in a shift of therapeutic goals. Therapies aiming to provide coverage of the burn have been replaced by treatments that have both functional as aesthetic outcomes. The standard in treating severe burns is still early excision followed by skin grafting. The use of cultured keratinocytes to cover extensive burn wounds appeared very promising at first, but the technique still has several limitations of which the long time to culture, the major costs, the risk of infection and the need for an adequate dermal layer limit clinical application. The introduction of dermal substitutes, composite grafts, tissue engineering based on stem cell application have been advocated. The aim of this review is to assess the use of cultured keratinocytes in terms of technical aspects, clinical application, limitations and future perspectives. Cultured keratinocytes are expected to keep playing a role in wound healing, especially in the field of chronic wounds. In severe burns, despite its limitations, keratinocytes can be beneficial if implemented as one of the elements in a broader wound management.

Regenerative medicine as applied to general surgery

The present review illustrates the state of the art of regenerative medicine (RM) as applied to surgical diseases and demonstrates that this field has the potential to address some of the unmet needs in surgery. RM is a multidisciplinary field whose purpose is to regenerate in vivo or ex vivo human cells, tissues, or organs to restore or establish normal function through exploitation of the potential to regenerate, which is intrinsic to human cells, tissues, and organs. RM uses cells and/or specially designed biomaterials to reach its goals and RM-based therapies are already in use in several clinical trials in most fields of surgery. The main challenges for investigators are threefold: Creation of an appropriate microenvironment ex vivo that is able to sustain cell physiology and function in order to generate the desired cells or body parts; identification and appropriate manipulation of cells that have the potential to generate parenchymal, stromal and vascular components on demand, both in vivo and ex vivo; and production of smart materials that are able to drive cell fate.

A rapid fabricated living dermal equivalent for skin tissue engineering: an in vivo evaluation in an acute wound model

The encapsulation of both cells and a surgical mesh in a polymerizing collagen hydrogel followed by mechanical compression, after polymerization, results in the rapid formation of a living dermal equivalent (LDE) with physical properties suitable for in vivo application. It was found in the current study that the LDE supported the attachment, growth, and differentiation of keratinocytes, allowing for the formation of living skin equivalents (LSEs) with a monolayer epidermis (LSE-M) and a stratified epidermis (LSE-S). The utility of the LDE for the fabrication of living wound dressings was further evaluated by testing the safety and efficacy of the LSE-M and LSE-S in a lapine model of an acute full-thickness skin defect. It was found that the LSE-S significantly stimulated blood vessel formation and accelerated epidermal wound closure compared with controls. The LSE-M showed similar trends but these were not significant. These findings indicate the clinical usefulness of the LDE in the treatment of acute and possibly chronic wounds, such as venous and diabetic ulcerations. The 1-h fabrication time of the LDE is a significant reduction compared with that of dermal components of current FDA-approved dressings, such as Dermagraft, Apligraf, and OrCel, which require days to weeks of in vitro culture. It is therefore proposed that the presented method could reduce the high cost associated with the production of living, tissue-engineered dressings.

Comparison of healing parameters in porcine full-thickness wounds transplanted with skin micrografts, split-thickness skin grafts, and cultured keratinocytes

BACKGROUND

Transplantation of skin micrografts (MGs), split-thickness skin grafts (STSGs), or cultured autologous keratinocytes (CKs) enhances the healing of large full-thickness wounds. This study compares these methods in a porcine wound model, investigating the utility of micrograft transplantation in skin restoration.

STUDY DESIGN

Full-thickness wounds were created on Yorkshire pigs and assigned to one of the following treatment groups: MGs, STSGs, CKs, wet nontransplanted, or dry nontransplanted. Dry wounds were covered with gauze and the other groups' wounds were enclosed in a polyurethane chamber containing saline. Biopsies were collected 6, 12, and 18 days after wounding. Quantitative and qualitative wound healing parameters including macroscopic scar appearance, wound contraction, neoepidermal maturation, rete ridge formation, granulation tissue thickness and width, and scar tissue formation were studied.

RESULTS

Transplanted wounds scored lower on the Vancouver Scar Scale compared with nontransplanted wounds, indicating a better healing outcome. All transplanted wounds exhibited significantly lower contraction compared with nontransplanted wounds. Wounds transplanted with either MGs, STSGs, or CKs showed a significant increase in re-epithelialization compared with nontransplanted wounds. Wounds transplanted with MGs or STSGs exhibited improved epidermal healing compared with nongrafted wounds. Furthermore, transplantation with STSGs or MGs led to less scar tissue formation compared with the nontransplanted wounds. No significant impact on scar formation was observed after transplantation of CKs.

CONCLUSIONS

Qualitative and quantitative measurements collected from full-thickness porcine wounds show that transplantation of MGs improve wound healing parameters and is comparable to treatment with STSGs.

Cultured keratinocytes on urinary bladder matrix scaffolds increase angiogenesis and help in rapid healing of wounds

INTRODUCTION

Urinary Bladder Matrix (UBM) is an extracellular matrix (ECM) scaffold. It is now used in wound care management of partial and full-thickness wounds where conventional methods for wound care usually fail to give satisfactory results.

OBJECTIVE

In this study, the authors are comparing the healing of full-thickness excisional wounds in New Zealand rabbits using either UBM scaffolds alone or in combination with cultured keratinocytes. The wounds were compared grossly and histologically.

MATERIALS AND METHODS

It is a comparative controlled study including 40 full-thickness wounds in 2 groups. Group (A) wounds: treated with UBM scaffolds, Group (B) wounds: treated with UBM scaffolds with cultured keratinocytes. The wounds were examined grossly after 1, 2, and 3 weeks, and were examined histologically at the end of the 3rd week using ordinary hematoxylin-eosin staining techniques.

RESULTS

All the wounds healed completely by the end of the 3rd week. Early wound contraction was significantly less in group B. More angiogenic response was evident in all specimens of group B.

CONCLUSION

This study shows that adding cultured keratinocytes to the rough surface of the UBM scaffold may be beneficial in reducing early wound contraction and improving wound vascularity in treatment of full-thickness wounds.

Meshed skin grafts placed upside down can take if desiccation is prevented

BACKGROUND

The role of the wet environment in wound healing has been investigated in various studies. The current study explores the role of the wet wound environment in promoting healing of skin grafts. The authors hypothesized that the survival of skin grafts is dependent not only on the orientation of transplantation but also on the environment into which the skin is transplanted.

METHODS

This study included 72 full-thickness (2.5 x 2.5-cm) wounds in six Yorkshire pigs. The wounds were grafted with autologous split-thickness skin grafts (meshed or sheet), placed either regularly (dermal side down) or inverted (dermal side up), and treated in a wet or a dry environment. Behavior of the skin grafts and healing were analyzed in histologic specimens collected on days 4, 6, 9, and 12 after wounding. Wound contraction was quantified by photoplanimetry.

RESULTS

In the wet environment, not only did inverted meshed skin grafts survive, but also they proliferated to accelerate reepithelialization. In this environment, wounds transplanted with inverted and regular meshed grafts showed no significant difference in reepithelialization rate and contraction. In contrast, in the dry environment, wounds transplanted with inverted meshed grafts showed a significantly lower reepithelialization rate and a higher contraction rate than wounds transplanted with regular grafts. Inverted meshed grafts in a dry environment and inverted sheet grafts did not survive.

CONCLUSION

The wound environment has an important role in the survival and proliferation of skin grafts, as demonstrated by survival of inverted meshed grafts in the wet environment and their contribution to accelerated reepithelialization, equal to the regularly placed grafts.

Cell suspensions of autologous keratinocytes or autologous fibroblasts accelerate the healing of full thickness skin wounds in a diabetic porcine wound healing model

Autologous dermal fibroblasts may be useful in the treatment of diabetic skin wounds. We hypothesized that cultured fibroblasts or cultured keratinocytes would not only survive in a hyperglycemic wound environment but also enhance the rate of re-epithelialization. We previously developed a new porcine model of delayed cutaneous wound healing in the diabetic pig. Full thickness wounds were created on the dorsum and dressed with polyurethane chambers to keep the wounds wet and to allow for wound fluid monitoring. Suspensions of either autologous fibroblasts or autologous keratinocytes were injected into full thickness wounds and compared with wounds treated in a wet environment in normal saline. Serum glucose and wound fluid glucose concentrations were monitored daily. Wound contraction was monitored and biopsies taken on day 12. Transplantation of suspensions of autologous fibroblasts or autologous keratinocytes enhanced re-epithelialization of cutaneous full thickness wounds. Wounds treated with autologous fibroblasts showed a re-epithelialization rate of 86.75% and wounds treated with autologous keratinocytes showed a re-epithelialization rate of 91.3%. This is compared with a re-epithelialization rate of 56.8% seen in the normal saline treated wounds. While previous studies have shown fibroblasts suspension to have little effect in the treatment of full thickness wounds in nondiabetic wounds, this study shows a clear beneficial effect in the use of fibroblast or keratinocyte suspensions for the cutaneous healing of diabetic wounds in pigs.

Enhanced susceptibility to infections in a diabetic wound healing model

Background

Wound infection is a common complication in diabetic patients. The progressive spread of infections and development of drug-resistant strains underline the need for further insights into bacterial behavior in the host in order to develop new therapeutic strategies. The aim of our study was to develop a large animal model suitable for monitoring the development and effect of bacterial infections in diabetic wounds.

Methods

Fourteen excisional wounds were created on the dorsum of diabetic and non-diabetic Yorkshire pigs and sealed with polyurethane chambers. Wounds were either inoculated with 2 × 10⁸ Colony-Forming Units (CFU) of Staphylococcus aureus or injected with 0.9% sterile saline. Blood glucose was monitored daily, and wound fluid was collected for bacterial quantification and measurement of glucose concentration. Tissue biopsies for microbiological and histological analysis were performed at days 4, 8, and 12. Wounds were assessed for reepithelialization and wound contraction.

Results

Diabetic wounds showed a sustained significant infection (>10⁵ CFU/g tissue) compared to non-diabetic wounds (p < 0.05) over the whole time course of the experiment. S. aureus-inoculated diabetic wounds showed tissue infection with up to 8 × 10⁷ CFU/g wound tissue. Non-diabetic wounds showed high bacterial counts at day 4 followed by a decrease and no apparent infection at day 12. Epidermal healing in S. aureus-inoculated diabetic wounds showed a significant delay compared with non-inoculated diabetic wounds (59% versus 84%; p < 0.05) and were highly significant compared with healing in non-diabetic wounds (97%; p < 0.001).

Conclusion

Diabetic wounds developed significantly more sustained infection than non-diabetic wounds. S. aureus inoculation leads to invasive infection and significant wound healing delay and promotes invasive co-infection with endogenous bacteria. This novel wound healing model provides the opportunity to closely assess infections during diabetic wound healing and to monitor the effect of therapeutical agents in vivo.

Cell suspension cultures of allogenic keratinocytes are efficient carriers for ex vivo gene transfer and accelerate the healing of full-thickness skin wounds by overexpression of human epidermal growth factor

The concept of using growth factor therapy to induce wound repair has been endorsed in studies that show reduced growth factors in wound fluid from chronic and aged wounds. In this study, we used cell suspensions of allogenic keratinocytes as gene-delivery vehicles for human epidermal growth factor (hEGF) and analyzed their impact on wound repair in a porcine wound-healing model. Full-thickness wounds were created on the backs of six Yorkshire pigs and covered with a wound chamber to create a wet wound-healing environment. First, 5 x 10(5) allogenic, autogenic, or mixed keratinocytes were transplanted into wounds and healing parameters were analyzed. Second, we measured long-term reepithelialization and contraction rates from day 8 until day 35. In the third experiment, allogenic keratinocytes were transfected with an hEGF-expressing plasmid pCEP-hEGF and transplanted in full-thickness wounds to improve repair. Wounds treated with autogenic, allogenic, or mixed keratinocytes showed a significantly higher rate of reepithelialization relative to saline-treated control wounds. Repetitive biopsies indicated that the use of allogenic keratinocytes did not lead to long-term wound breakdown. Wounds treated with hEGF-expressing allogenic keratinocytes reepithelialized faster than wounds treated with allogenic keratinocytes or control wounds. With a peak hEGF expression of 920.8 pg/mL, hEGF was detectable until day 5 after transplantation compared with minimal hEGF expression in control wounds. This study shows that allogenic keratinocytes can serve as efficient gene transfer vehicles for ex vivo growth factor delivery to full-thickness wounds and overexpression of hEGF further improves reepithelialization rates.

Optimized delivery of skin keratinocytes by aerosolization and suspension in fibrin tissue adhesive

Aerosolized suspensions of keratinocytes provide a potential therapy for wounds, but the effects of aerosolization on cell viability remain unclear. Likewise, little is known of the resulting cell distribution pattern and how this compares to the density required for epithelialization. The potential benefits of cospraying cells in the presence of fibrin adhesive are equally uncertain. Thus, in the present study we have optimized conditions for the aerosolization of cultured keratinocytes using a device (Tissomat) that supports the option for coapplication with fibrin (Tisseel). Cell viability was unaffected when sprayed at 10 psi, but a significant reduction in metabolic activity, as determined by the methylthiazoyldiphenol-tetrazolium assay, was observed at higher pressure. Bursts of 0.2 mL cell suspension (1.5x10(6)/mL) delivered from a height of 10 cm was sufficient to epithelialize an area of 10-15 cm2 within 7 days in vitro. Confluent areas corresponded to those with a density of 5,000-10,000 cells/cm2 at 24 hours. Optimal cell growth in Tisseel was achieved through dilution of fibrinogen (1-3 mg/mL) and thrombin (2-5 IU/mL). This optimized formulation eliminated fluid run-off postspraying and stimulated a twofold increase in cellular response. Therefore, our in vitro data supports the theory that aerosolized suspensions of keratinocytes in fibrin will benefit healing.

The cell based dressing with living allogenic keratinocytes in the treatment of foot ulcers: a case study

In this study, we aimed to investigate the efficacy of cell based dressing with living allogenic keratinocytes in diabetic foot patients. To address this issue, the cultured keratinocytes were attached to the microcarriers produced from polyethylene and silica. The microcarriers were then applied to the wounds at 3-day intervals. Forty patients with grade II and III diabetic foot ulcers were included into the study. The patients were randomised into two groups (n=20). The treatment and control groups received cell based dressing and microcarriers kept in culture medium overnight, respectively. The wound size was recorded at 3 days intervals. The wounds were also categorised by a specific scoring system considering the wound contraction, granulation tissue formation, epithelisation and discharge from the wounds. The high score indicates better condition. The mean reduction of the wound area was 92% in the treatment group and 32% in the control group at the end of the 30 days treatment (p<0.001). When considered the complete healing, the mean number of dressings was 9.2+/-3.2 in the treatment group whereas it was 16.5+/-2.3 in the control group (p<0.001). The initial mean score of the treatment and control groups were 2.5 and 2.35, respectively. At the end of the 30th day, the mean score of the treatment group was 17.15+/-2.7 and of control group was 9.05+/-3. Allogenic keratinocyte treatment delivered with microcarriers can make significant contributions to wound healing in diabetic foot patients.

In vivo gene delivery of Ad-VEGF121 to full-thickness wounds in aged pigs results in high levels of VEGF expression but not in accelerated healing

We have previously reported that endogenous vascular endothelial growth factor (VEGF) concentration in older pig wounds peaked later and at one-fourth the level of young pigs. These data suggested that VEGF might play a major role in the healing of full-thickness wounds in the aged pig. By in vivo gene transfer using the microseeding technique, we treated full-thickness wounds with different doses of VEGF-expressing adenoviral vector (Ad-VEGF) varying from 1 x 10(7) to 2.7 x 10(11) particles per wound (ppw). We found that the VEGF expression in wound fluid followed a dose-response pattern. However, when wounds were microseeded with the highest concentration of Ad-VEGF (2.7 x 10(11) ppw), diminished healing rates were found. We then determined the minimal functional concentrations of Ad-VEGF. We used five aged Yucatan minipigs, all retired breeders, to analyze the role of over-expression of 1 x 10(8) and 1 x 10(9) ppw of Ad-VEGF (n= 78) in terms of healing of full-thickness wounds, all 2.5 x 2.5 x 1 cm in size (n= 158). The Ad-VEGF solutions were delivered to the wound floor and borders by in vivo microseeding. Control wounds (n= 80) were microseeded with Ad-Lac-Z (n= 25), treated with saline (n= 49) or treated dry (n= 6). All wounds except for the dry-treated ones were covered with a wound chamber and a wet environment was created by injecting 2.5 ml saline into the chamber. Peak VEGF expression (2300-4000 pg/ml) was detected on days 2 or 3 post gene delivery. This level of VEGF expression was not seen in the saline (n= 49) or Ad-null (n= 25) control groups. The VEGF expression in wounds treated with 1 x 10(8) and 3 x 10(8) ppw (n= 39) exhibited a slower onset with a peak concentration of 400-920 pg/ml on days 5-7. Although high levels of VEGF expression were achieved in the local wound environment, we could not show a significant increase in neovascularization as compared to saline-treated wounds. No significant differences were observed in the rate of reepithelialization and wound contraction among groups of full-thickness wounds treated with Ad-VEGF, Ad-null mutant, or saline in the aged "wet wound healing" pig model. These results indicate that increased levels of VEGF in wounds produced by in vivo gene transfer have little effect on the healing of full-thickness wounds in the aged pig model. Moreover, significantly higher levels of VEGF expression by Ad-VEGF could lead to impaired wound healing.

Gene therapy in the treatment of lower extremity wounds

This article presents a brief overview of the etiology of chronic wounds of the lower extremities and their current medical and surgical treatment. Gene therapy as a potential tool for treating therapeutically challenging wounds is described in terms of the vectors employed in gene transfer, as well as the strategies used to promote wound healing. Results from animal model studies, as well as clinical trials, are presented.

An Improved Organ Culture for Regeneration of Pure Autologous Keratinocytes from Small Split-Thickness Skin Specimens

BACKGROUND

Failure of autologous keratinocyte culture from small split-thickness skin specimens or contamination of the keratinocyte culture by melanocytes represents practical problems in basic medical research and clinical studies.

PURPOSE

To establish a simple and reliable method of harvesting pure autologous keratinocytes from a small split-thickness skin specimen.

METHODS

Split-thickness (0.3 mm) skin explants (1 x 2 mm) were firstly cultured in DMEM containing 10% FCS till formation of keratinocyte strips, then cultured in serum-free keratinocyte growth medium or cocultured with lethally irradiated 3T3 fibroblasts (J2) in a mixture of DMEM and Ham's F12 (DF) medium.

RESULTS

Pure autologous keratinocyte culture is easily and reliably established by this organ culture technique.

CONCLUSION

Culturing of skin explants in serum-free keratinocyte growth medium or coculturing of the skin explants with lethally irradiated 3T3 cells in DF medium is proved to be a useful, simple and reliable method of harvesting pure autologous keratinocytes from a small split-thickness skin biopsy.

In vitro cultured autologous pre-confluent oral keratinocytes for experimental prefabrication of oral mucosa

The reconstruction of large defects after head and neck cancer resection often requires composite tissue transfer to replace a combination of bone, muscle and mucosa. Thus, tissue engineering techniques may be useful for oral mucosal reconstructive surgery to prefabricate mucosal tissue on the muscle flap in vivo, instead of using conventional skin-bearing composite flaps. The aim of this study was to investigate whether autogenous pre-confluent oral keratinocytes (PCOK) cultured in vitro can create mucosal coverage on muscle in vivo, in a single grafting procedure. In 30 Wistar rats, with a small piece of oral mucosa (2 mm x 5 mm), oral keratinocytes were isolated and then seeded on a hydrophilic PTFE membrane (n = 50) in serum-free culture condition. After 48 h, the membrane, together with the PCOK, was transplanted onto the gracilis muscle to fabricate a mucosal flap in vivo. The wound bed was closed primarily until the time of examination. Biopsies were carried out 1, 2, 3, and 4 weeks, respectively, after transplantation and were evaluated immunohistochemically (AE1/AE3 anti-pancytokeratin, cytokeratin 5/6, collagen IV, laminin, lectin-specific labeling of N-acetylglucosamine oligomeres of endothelial cells) with relation to the following criteria: (1) graft acceptance; (2) inflammatory signs; (3) structural changes and keratinocyte lining; (4) expression of basement membrane components; and (5) vascularization. Ninety-one percent of the grafts showed uniform epithelial layers. The mean number of reconstructed epithelial cell layers was 1.7, 2.0, 1.85 and 2.7 at 1, 2, 3 and 4 weeks, respectively after transplantation (P = 0.342). Collagen IV, laminin and lectin-specific capillaries developed between the neoepithelium and the underlying muscular layer. Only two specimens showed signs of infection 2 weeks after transplantation. In conclusion, this experiment demonstrated that PCOK grafts on muscle in vivo can achieve uniform multi-layered oral epithelial coverage in a short period of time. This technique may be a useful alternative tool for oropharyngeal reconstructive surgery and is also worth considering for further clinical studies.

A computerised, unbiased method for epithelial measurement

OBJECTIVE

To develop and evaluate a standardised method for unbiased measurements of epithelial thickness taking the variability of the dermal papillae in consideration.

METHODS

A computer-assisted measurement program suitable for haematoxylin and eosin routine stained specimens has been developed.

RESULTS

The developed program was designed to measure four different distance parameters, taking the number, height and width of dermal papillae into account. The measurement program gave very accurate results compared with manual measurements. The measurement results can be presented as tables or star graphs, and the results can be further processed by multivariate analysis.

CONCLUSION

The computer-assisted measurement program is considered to be a valuable and reliable tool for measurements of epithelial thickness, irrespectively of the variability of the epithelial morphology. Since length, size and number of the papillae may change with certain pathological conditions, age and also under hormonal influence, this method can be a helpful diagnostic tool.

Autologous cultured keratinocytes on porcine gelatin microbeads effectively heal chronic venous leg ulcers

We have established a specific bioreactor microcarrier cell culture system using porcine gelatin microbeads as carriers to produce autologous keratinocytes on a large scale. Moreover, we have shown that autologous keratinocytes can be cultured on porcine collagen pads, thereby forming a single cell layer. The objective of this study was to compare efficacy and safety of autologous cultured keratinocytes on microbeads and collagen pads in the treatment of chronic wounds. Fifteen patients with recalcitrant venous leg ulcers were assigned to three groups in a single-center, prospective, uncontrolled study: five underwent a single treatment with keratinocyte monolayers on collagen pads (group 1); another five received a single grafting with keratinocyte-microbeads (group 2); and the last five received multiple, consecutive applications of keratinocyte-microbeads 3 days apart (group 3). All patients were followed for up to 12 weeks. By 12 weeks, there was a mean reduction in the initial wound area of 50, 83, and 97 percent in the three groups, respectively. The changes in wound size were statistically significant between the first and third groups (p= 0.0003). Keratinocyte-microbeads proved to be more effective than keratinocyte monolayers on collagen pads when the former were applied every 3 days. Rapid availability within 10-13 days after skin biopsy and easy handling represent particular advantages.

Cultured autologous fibroblasts augment epidermal repair

BACKGROUND

Autologous dermal fibroblasts may be useful in the treatment of skin wounds and for the enhancement of keratinocyte proliferation. This paper addressed the following questions: (1) can cultured fibroblasts (CF) be transplanted as suspensions to full-thickness skin wounds and do they influence wound healing; (2) will the transplanted CF be integrated into the new dermis; (3) can a transgene that encodes a secretable marker, human epidermal growth factor (hEGF), be expressed in the wound fluid by the transplanted CF; and (4) do CF cotransplanted with cultured keratinocytes (CK) influence the rate of wound healing?

METHODS

Suspensions of CF were transplanted alone or together with CK to full-thickness wounds covered with liquid-containing chambers in an established porcine model.

RESULTS

Transplantation of CF accelerated reepithelialization as determined from wound histologies and sequential measurements of protein efflux over the wound surface. CF transfected with a marker gene, beta-galactosidase, resulted in in vivo gene expression and demonstrated that transplanted CF integrated into the developing dermis. Transplantation of hEGF gene-transfected CF resulted in significant hEGF expression in wound fluid. The hEGF levels peaked at day 1 (2450 pg/ml) and then sharply decreased to low levels on day 6. CF cotransplanted with CK led to greater number of keratinocyte colonies in the wound and accelerated reepithelialization as compared with CK alone.

CONCLUSIONS

Transplanted CF integrated into the dermis, accelerated reepithelialization, and improved the outcome of CK transplantation. CF may also be used for the expression of transgenes in wound and wound fluid.

Autologous skin transplantation: comparison of minced skin to other techniques

BACKGROUND

Skin grafting may be necessary to close nonhealing skin wounds. This report describes a fast and minimally invasive method to produce minced skin suitable for transplantation to skin wounds. The technique was evaluated in an established porcine skin wound healing model and was compared to split-thickness skin grafts and suspensions of cultured and noncultured keratinocytes.

MATERIALS AND METHODS

The study included 90 wounds on 3 pigs. Fluid-treated full-thickness skin wounds were grafted with minced skin, split-thickness skin grafts, noncultured keratinocytes, or cultured keratinocytes. Controls received either fluid or dry treatment. The wound healing process was analyzed in histologies collected at Days 8 to 43 postwounding. Wound contraction was quantified by photoplanimetry.

RESULTS

Wounds transplanted with minced skin and keratinocyte suspension contained several colonies of keratinocytes in the newly formed granulation tissue. During the healing phase, the colonies progressed upward and reepithelialization was accelerated. Minced skin and split-thickness skin grafts reduced contraction as compared to keratinocyte suspensions and saline controls. Granulation tissue formation was also reduced in split-thickness skin-grafted wounds.

CONCLUSIONS

Minced skin grafting accelerates reepithelialization of fluid-treated skin wounds. The technique is faster and less expensive than split-thickness skin grafting and keratinocyte suspension transplantation. Minced skin grafting may have implications for the treatment of chronic wounds.