Studies in fetal wound healing. IV. Hyaluronic acid-stimulating activity distinguishes fetal wound fluid from adult wound fluid

Marvels of spiny mouse regeneration: cellular players and their interactions in restoring tissue architecture in mammals

Understanding the cellular and molecular determinants of mammalian tissue regeneration and repair is crucial for developing effective therapies that restore tissue architecture and function. In this review, we focus on the cell types involved in scarless wound response and regeneration of spiny mice (Acomys). Comparative -omics approaches with scar-prone mammals have revealed species-specific peculiarities in cellular behavior during the divergent healing trajectories. We discuss the developing views on which cell types engage in restoring the architecture of spiny mouse tissues through a co-ordinated spatiotemporal response to injury. While yet at the beginning of understanding how cells interact in these fascinating animals to regenerate tissues, spiny mice hold great promise for scar prevention and anti-fibrotic treatments.

In Utero Extrahepatic Bile Duct Damage and Repair: Implications for Biliary Atresia

Biliary atresia (BA) is a cholangiopathy affecting the extrahepatic bile duct (EHBD) of newborns. The etiology and pathophysiology of BA are not fully understood; however, multiple causes of damage and obstruction of the neonatal EHBD have been identified. Initial damage to the EHBD likely occurs before birth. We discuss how different developmental stages in utero and birth itself could influence the susceptibility of the fetal EHBD to damage and a damaging wound-healing response. We propose that a damage-repair response of the fetal and neonatal EHBD involving redox stress and a program of fetal wound healing could-regardless of the cause of the initial damage-lead to either obstruction and BA or repair of the duct and recovery. This overarching concept should guide future research targeted toward identification of factors that contribute to recovery as opposed to progression of injury and fibrosis. Viewing BA through the lens of an in utero damage-repair response could open up new avenues for research and suggests exciting new therapeutic targets.

Comprehensive Characterization of Tissues Derived from Animals at Different Regenerative Stages: A Comparative Analysis between Fetal and Adult Mouse Skin

Tissue regeneration capabilities vary significantly throughout an organism's lifespan. For example, mammals can fully regenerate until they reach specific developmental stages, after which they can only repair the tissue without restoring its original architecture and function. The high regenerative potential of fetal stages has been attributed to various factors, such as stem cells, the immune system, specific growth factors, and the presence of extracellular matrix molecules upon damage. To better understand the local differences between regenerative and reparative tissues, we conducted a comparative analysis of skin derived from mice at regenerative and reparative stages. Our findings show that both types of skin differ in their molecular composition, structure, and functionality. We observed a significant increase in cellular density, nucleic acid content, neutral lipid density, Collagen III, and glycosaminoglycans in regenerative skin compared with reparative skin. Additionally, regenerative skin had significantly higher porosity, metabolic activity, water absorption capacity, and elasticity than reparative skin. Finally, our results also revealed significant differences in lipid distribution, extracellular matrix pore size, and proteoglycans between the two groups. This study provides comprehensive data on the molecular and structural clues that enable full tissue regeneration in fetal stages, which could aid in developing new biomaterials and strategies for tissue engineering and regeneration.

Healing Mechanisms in Cutaneous Wounds: Tipping the Balance

Acute and chronic cutaneous wounds pose a significant health and economic burden. Cutaneous wound healing is a complex process that occurs in four distinct, yet overlapping, highly coordinated stages: hemostasis, inflammation, proliferation, and remodeling. Postnatal wound healing is reparative, which can lead to the formation of scar tissue. Regenerative wound healing occurs during fetal development and in restricted postnatal tissues. This process can restore the wound to an uninjured state by producing new skin cells from stem cell reservoirs, resulting in healing with minimal or no scarring. Focusing on the pathophysiology of acute burn wounds, this review highlights reparative and regenerative healing mechanisms (including the role of cells, signaling molecules, and the extracellular matrix) and discusses how components of regenerative healing are being used to drive the development of novel approaches and therapeutics aimed at improving clinical outcomes. Important components of regenerative healing, such as stem cells, growth factors, and decellularized dermal matrices, are all being evaluated to recapitulate more closely the natural regenerative healing process.

An investigation of the effects of amniotic fluid on experimental ischemia/reperfusion damage in rat testes

INTRODUCTION

Various agents have been tested as preventive treatments for ischemia/reperfusion (IR) damage. In this study, we have investigated for the first time in the literature the efficacy of injection of amniomax (AMX) into testicular parenchyma, which is a commercial medium of rat amniotic fluid, in preventing testicular IR damage related to testicular torsion.

OBJECTIVE

This study aims to evaluate whether or not amniomax has an effect on experimental IR damage in rat testes using biochemical and histopathological methods based on data in the literature. Even if testicular torsion is repaired surgically in early term injury because of de IR damage still occurs. Is it possible to reduce the ischemia reperfusion injury with amniotic fluid and increase the success of treatment?

STUDY DESIGN

40 male Wistar albino rats were included. Four groups were formed with 10 rats in each group: Sham, Ischemia/Reperfusion (IR), injection 1 min before detorsion (AMX-BD), injection 1 min after detorsion (AMX-AD). Total Oxidant Status (TOS) and Oxidative Stress Index (OSI) were computed for oxidative stress, and Total Antioxidant Status (TAS) levels were computed for the antioxidant system, for both serum and tissue. Necrosis and microcalcification levels were assessed in the evaluation of testicular histology. P < 0.05 was considered statistically significant.

RESULTS

AMX-AD group has low necrosis degree than IR, Mean serum and tissue levels of TAS, TOS, and OSI parameters were respectively determined as; for TAS: 0.64 ± 0.11 and 0.96 ± 0.25 mmol Trolox Equivalent/L; for TOS: 6.71 ± 0.87 and 9.40 ± 1.03 μmol H₂O₂ equivalent/L; for OSI: 11.94 ± 3.74 and 10.70 ± 4.23 arbitrary unit.

DISCUSSION

Our study has investigated for the first time in the literature the efficacy of amniotic fluid in preventing testicular IR damage, and used amniomax (AMX) for this purpose. The limitation of our study may be the small number of rat in the groups.

CONCLUSION

We think an injection after detorsion is more favorable considering that the AMX-AD group demonstrated significantly lower levels of TOS in serum and tissue and OSI in serum, and significantly higher serum levels of TAS compared to the AMX-BD group, as well as the fact that the morphological protection effect was only observed for injections performed immediately after detorsion.

The bright side of fibroblasts: molecular signature and regenerative cues in major organs

Fibrosis is a pathologic process characterized by the replacement of parenchymal tissue by large amounts of extracellular matrix, which may lead to organ dysfunction and even death. Fibroblasts are classically associated to fibrosis and tissue repair, and seldom to regeneration. However, accumulating evidence supports a pro-regenerative role of fibroblasts in different organs. While some organs rely on fibroblasts for maintaining stem cell niches, others depend on fibroblast activity, particularly on secreted molecules that promote cell adhesion, migration, and proliferation, to guide the regenerative process. Herein we provide an up-to-date overview of fibroblast-derived regenerative signaling across different organs and discuss how this capacity may become compromised with aging. We further introduce a new paradigm for regenerative therapies based on reverting adult fibroblasts to a fetal/neonatal-like phenotype.

Inflammation as an orchestrator of cutaneous scar formation: a review of the literature

Inflammation is a key phase in the cutaneous wound repair process. The activation of inflammatory cells is critical for preventing infection in contaminated wounds and results in the release of an array of mediators, some of which stimulate the activity of keratinocytes, endothelial cells, and fibroblasts to aid in the repair process. However, there is an abundance of data suggesting that the strength of the inflammatory response early in the healing process correlates directly with the amount of scar tissue that will eventually form. This review will summarize the literature related to inflammation and cutaneous scar formation, highlight recent discoveries, and discuss potential treatment modalities that target inflammation to minimize scarring.

The role of mesenchymal-epithelial transition in endometrial function

BACKGROUND

The human uterine endometrium undergoes significant remodeling and regeneration on a rapid and repeated basis, after parturition, menstruation, and in some cases, injury. The ability of the adult endometrium to undergo cyclic regeneration and differentiation/decidualization is essential for successful human reproduction. Multiple key physiologic functions of the endometrium require the cells of this tissue to transition between mesenchymal and epithelial phenotypes, processes known as mesenchymal-epithelial transition (MET) and epithelial-mesenchymal transition (EMT). Although MET/EMT processes have been widely characterized in embryonic development and in the context of malignancy, mounting evidence demonstrates the importance of MET/EMT in allowing the endometrium the phenotypic and functional flexibility necessary for successful decidualization, regeneration/re-epithelialization and embryo implantation.

OBJECTIVE AND RATIONALE

The objective of this review is to provide a comprehensive summary of the observations concerning MET and EMT and their regulation in physiologic uterine functions, specifically in the context of endometrial regeneration, decidualization and embryo implantation.

SEARCH METHODS

Using variations of the search terms 'mesenchymal-epithelial transition', 'mesenchymal-epithelial transformation', 'epithelial-mesenchymal transition', 'epithelial-mesenchymal transformation', 'uterus', 'endometrial regeneration', 'endometrial decidualization', 'embryo implantation', a search of the published literature between 1970 and 2018 was conducted using the PubMed database. In addition, we searched the reference lists of all publications included in this review for additional relevant original studies.

OUTCOMES

Multiple studies demonstrate that endometrial stromal cells contribute to the regeneration of both the stromal and epithelial cell compartments of the uterus, implicating a role for MET in mechanisms responsible for endometrial regeneration and re-epithelialization. During decidualization, endometrial stromal cells undergo morphologic and functional changes consistent with MET in order to accommodate embryo implantation. Under the influence of estradiol, progesterone and multiple other factors, endometrial stromal fibroblasts acquire epithelioid characteristics, such as expanded cytoplasm and rough endoplasmic reticulum required for greater secretory capacity, rounded nuclei, increased expression of junctional proteins which allow for increased cell-cell communication, and a reorganized actin cytoskeleton. During embryo implantation, in response to both maternal and embryonic-derived signals, the maternal luminal epithelium as well as the decidualized stromal cells acquire the mesenchymal characteristics of increased migration/motility, thus undergoing EMT in order to accommodate the invading trophoblast.

WIDER IMPLICATIONS

Overall, the findings support important roles for MET/EMT in multiple endometrial functions required for successful reproduction. The endometrium may be considered a unique wound healing model, given its ability to repeatedly undergo repair without scarring or loss of function. Future studies to elucidate how MET/EMT mechanisms may contribute to scar-free endometrial repair will have considerable potential to advance studies of wound healing mechanisms in other tissues.

Current Approaches Targeting the Wound Healing Phases to Attenuate Fibrosis and Scarring

Cutaneous fibrosis results from suboptimal wound healing following significant tissue injury such as severe burns, trauma, and major surgeries. Pathologic skin fibrosis results in scars that are disfiguring, limit normal movement, and prevent patient recovery and reintegration into society. While various therapeutic strategies have been used to accelerate wound healing and decrease the incidence of scarring, recent studies have targeted the molecular regulators of each phase of wound healing, including the inflammatory, proliferative, and remodeling phases. Here, we reviewed the most recent literature elucidating molecular pathways that can be targeted to reduce fibrosis with a particular focus on post-burn scarring. Current research targeting inflammatory mediators, the epithelial to mesenchymal transition, and regulators of myofibroblast differentiation shows promising results. However, a multimodal approach addressing all three phases of wound healing may provide the best therapeutic outcome.

Hyaluronic acid as a macromolecular crowding agent for production of cell-derived matrices

Cell-derived matrices (CDMs) provide an exogenous source of human extracellular matrix (ECM), with applications as cell delivery vehicles, substrate coatings for cell attachment and differentiation, and as biomaterial scaffolds. However, commercial application of CDMs has been hindered due to the prolonged culture time required for sufficient ECM accumulation. One approach to increasing matrix deposition in vitro is macromolecular crowding (MMC), which is a biophysical phenomenon that limits the diffusion of ECM precursor proteins, resulting in increased ECM accumulation at the cell layer. Hyaluronic acid (HA), a natural MMC highly expressed in vivo during fetal development, has been shown to play a role in ECM production, but has not been investigated as a macromolecule for increasing cell-mediated ECM deposition in vitro. In the current study, we hypothesized that HA can act as a MMC, and increase cell-mediated ECM production. Human dermal fibroblasts were cultured for 3, 7, or 14 days with 0%, 0.05%, or 0.5% high molecular weight HA. Ficoll 70/400 was used as a positive control. SDS-PAGE, Sircol, and hydroxyproline assays indicated that 0.05% HA-treated cultures had significantly higher mean collagen deposition at 14 days, whereas Ficoll 70/400-treated cultures had significantly lower collagen production compared to the HA and untreated controls. However, fluorescent immunostaining of ECM proteins and quantification of mean gray values did not indicate statistically significant differences in ECM production in HA or Ficoll 70/400-treated cultures compared to untreated controls. Raman imaging (a marker-free spectral imaging method) indicated that HA increased ECM deposition in human dermal fibroblasts. These results are consistent with decreases in CDM stiffness observed in Ficoll 70/400-treated cultures by atomic force microscopy. Overall, these results indicate that there are macromolecule- and cell type- dependent effects on matrix assembly, turnover, and stiffness in cell-derived matrices. STATEMENT OF SIGNIFICANCE: Cell-derived matrices (CDMs) are versatile biomaterials with many regenerative medicine applications, including as cell and drug delivery vehicles and scaffolds for wound healing and tissue regeneration. While CDMs have several advantages, their commercialization has been limited due to the prolonged culture time required to achieve CDM synthesis in vitro. In this study, we explored the use of hyaluronic acid (HA) as a macromolecular crowder in human fibroblast cell cultures to support production of CDM biomaterials. Successful application of macromolecular crowding will allow development of human cell-derived, xeno-free biomaterials that re-capitulate the native human tissue microenvironment.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Wound Healing: A Cellular Perspective

Wound healing is one of the most complex processes in the human body. It involves the spatial and temporal synchronization of a variety of cell types with distinct roles in the phases of hemostasis, inflammation, growth, re-epithelialization, and remodeling. With the evolution of single cell technologies, it has been possible to uncover phenotypic and functional heterogeneity within several of these cell types. There have also been discoveries of rare, stem cell subsets within the skin, which are unipotent in the uninjured state, but become multipotent following skin injury. Unraveling the roles of each of these cell types and their interactions with each other is important in understanding the mechanisms of normal wound closure. Changes in the microenvironment including alterations in mechanical forces, oxygen levels, chemokines, extracellular matrix and growth factor synthesis directly impact cellular recruitment and activation, leading to impaired states of wound healing. Single cell technologies can be used to decipher these cellular alterations in diseased states such as in chronic wounds and hypertrophic scarring so that effective therapeutic solutions for healing wounds can be developed.

Scarring vs. functional healing: Matrix-based strategies to regulate tissue repair

All vertebrates possess mechanisms to restore damaged tissues with outcomes ranging from regeneration to scarring. Unfortunately, the mammalian response to tissue injury most often culminates in scar formation. Accounting for nearly 45% of deaths in the developed world, fibrosis is a process that stands diametrically opposed to functional tissue regeneration. Strategies to improve wound healing outcomes therefore require methods to limit fibrosis. Wound healing is guided by precise spatiotemporal deposition and remodelling of the extracellular matrix (ECM). The ECM, comprising the non-cellular component of tissues, is a signalling depot that is differentially regulated in scarring and regenerative healing. This Review focuses on the importance of the native matrix components during mammalian wound healing alongside a comparison to scar-free healing and then presents an overview of matrix-based strategies that attempt to exploit the role of the ECM to improve wound healing outcomes.

Moldable Hyaluronan Hydrogel Enabled by Dynamic Metal-Bisphosphonate Coordination Chemistry for Wound Healing

Biomaterial-based regenerative approaches would allow for cost-effective off-the-shelf solution for the treatment of wounds. Hyaluronan (HA)-based hydrogel is one attractive biomaterial candidate because it is involved in natural healing processes, including inflammation, granulation, and reepithelialization. Herein, dynamic metal-ligand coordination bonds are used to fabricate moldable supramolecular HA hydrogels with self-healing properties. To achieve reversible crosslinking of HA chains, the biopolymer is modified with pendant bisphosphonate (BP) ligands using carbodiimide coupling and chemoselective "click" reactions. Hydrogel is formed immediately after simple addition of silver (Ag⁺ ) ions to the solution of HA containing BP groups (HA-BP). Compared with previous HA-based wound healing hydrogels, the HA-BP·Ag⁺ hydrogel is highly suitable for clinical use as it can fill irregularly shaped wound defects without the need for premolding. The HA-BP·Ag⁺ hydrogel shows antimicrobial properties to both Gram-positive and Gram-negative bacterial strains, enabling prevention of infections in wound care. In vivo evaluation using a rat full-thickness skin wound model shows significantly lower wound remaining rate and a thicker layer of regenerated epidermis as compared with the group left without treatment. The presented moldable and self-healing supramolecular HA hydrogel with "ready-to-use" properties possesses a great potential for regenerative wound treatment.

Scarless wound healing: Transitioning from fetal research to regenerative healing

Since the discovery of scarless fetal skin wound healing, research in the field has expanded significantly with the hopes of advancing the finding to adult human patients. There are several differences between fetal and adult skin that have been exploited to facilitate scarless healing in adults including growth factors, cytokines, and extracellular matrix substitutes. However, no one therapy, pathway, or cell subtype is sufficient to support scarless wound healing in adult skin. More recently, products that contain or mimic fetal and adult uninjured dermis were introduced to the wound healing market with promising clinical outcomes. Through our review of the major experimental targets of fetal wound healing, we hope to encourage research in areas that may have a significant clinical impact. Additionally, we will investigate therapies currently in clinical use and evaluate whether they represent a legitimate advance in regenerative medicine or a vulnerary agent. WIREs Dev Biol 2018, 7:e309. doi: 10.1002/wdev.309 This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Regeneration Plant Development > Cell Growth and Differentiation Adult Stem Cells, Tissue Renewal, and Regeneration > Environmental Control of Stem Cells.

Evaluation of gelatin-hyaluronic acid composite hydrogels for accelerating wound healing

Excellent wound dressings maintain a warm and moist environment, thus accelerating wound healing. In this study, we cross-linked gelatin and hyaluronic acid with ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride in different ratios (gelatin/hyaluronic acid = 8:2, gelatin/hyaluronic acid = 5:5, gelatin/hyaluronic acid = 2:8), and explored the effects and mechanisms of gelatinhyaluronic acid hydrogels on wound healing. This was done by examining dressing properties, such as fluid uptake ability, water vapor transmission rate, and the rate of water evaporation. We further verified biological function by using in vitro and in vivo wound models. The hydrogels display appropriate fluid uptake ability and good water vapor transmission rate and rate of water evaporation all of which can provide an adequate moisture environment for wound healing. Cell cytotoxicity and proliferation tests show that the hydrogels have no cytotoxicity, furthermore, gelatin/hyaluronic acid = 8:2 hydrogels have the potential to promote cell proliferation. Animal wound models demonstrate that the hydrogels can effectively promote wound healing in vivo, in particular, the gelatin/hyaluronic acid = 8:2 group which promoted the most rapid healing. Accordingly, gelatin-hyaluronic acid dressings, especially the gelatin/hyaluronic acid = 8:2 hydrogels, have a promising outlook for clinical applications in wound healing.

The neurochemistry of peripheral nerve regeneration

Peripheral nerve injuries (PNIs) can be most disabling, resulting in the loss of sensitivity, motor function and autonomic control in the involved anatomical segment. Although injured peripheral nerves are capable of regeneration, sub-optimal recovery of function is seen even with the best reconstruction. Distal axonal degeneration is an unavoidable consequence of PNI. There are currently few strategies aimed to maintain the distal pathway and/or target fidelity during regeneration across the zone of injury. The current state of the art approaches have been focussed on the site of nerve injury and not on their distal muscular targets or representative proximal cell bodies or central cortical regions. This is a comprehensive literature review of the neurochemistry of peripheral nerve regeneration and a state of the art analysis of experimental compounds (inorganic and organic agents) with demonstrated neurotherapeutic efficacy in improving cell body and neuron survival, reducing scar formation and maximising overall nerve regeneration.

Novel perspectives on the role of the human microbiota in regenerative medicine and surgery

Plastic surgery is transitioning from a fine craftsmanship to a regenerative science. In wound healing, the role of microorganisms is no longer considered to be just counteracting, but also promoting. Furthermore, host-microbe interactions are essential for numerous aspects of normal mammalian physiology, from metabolic activity to immune homeostasis. Each area of the human body hosts a unique microbial community, and the composition of microbiota is dependent on the host, age and the anatomical area, and it changes according to the characteristics of the microenvironment. Every squared centimeter of skin contains ~1 billion bacteria. The majority of microorganisms of the skin are commensal or temporary passing members. Skin flora mechanisms interacting or influencing the human physical skin barrier are not well defined. Resident skin bacteria provide the first line of defence against potentially dangerous pathogens and produce small molecules that influence their microbial neighbours. Furthermore, the microbiota activates and assists innate immunity and influences adaptive immunity. Various types of immune and non-immune cells contribute to wound healing. The proliferative phase of wound healing is inversely proportional to the extent of the post-traumatic inflammatory reaction. Topical bacterial lipopolysaccharide application markedly affects wound healing by accelerating the resolution of inflammation, increasing macrophage infiltration, enhancing collagen synthesis and altering the secretion of mediators involved in skin regeneration. Various studies have investigated the biological contents of thermal spring waters, and their anti-inflammatory and immune protective roles. In addition, the regenerative properties of thermal spring waters were analysed in an experimental animal wound model. The areas treated with thermal water healed faster than the areas treated with conventional dressings, and exhibited a collagen and elastic fiber network comparable with the normal skin. Thus, the microbial environment may be considered as a potential tool in regenerative medicine and surgery.

Identifying Novel Targets for Treatment of Liver Fibrosis: What Can We Learn from Injured Tissues which Heal Without a Scar?

The liver is unique in that it is able to regenerate. This regeneration occurs without formation of a scar in the case of non-iterative hepatic injury. However, when the liver is exposed to chronic liver injury, the purely regenerative process fails and excessive extracellular matrix proteins are deposited in place of normal liver parenchyma. While much has been discovered in the past three decades, insights into fibrotic mechanisms have not yet lead to effective therapies; liver transplant remains the only cure for advanced liver disease. In an effort to broaden the collection of possible therapeutic targets, this review will compare and contrast the liver wound healing response to that found in two types of wound healing: scarless wound healing of fetal skin and oral mucosa and scar-forming wound healing found in adult skin. This review will examine wound healing in the liver and the skin in relation to the role of humoral and cellular factors, as well as the extracellular matrix, in this process. While several therapeutic targets are similar between fibrotic liver and adult skin wound healing, others are unique and represent novel areas for hepatic anti-fibrotic research. In particular, investigations into the role of hyaluronan in liver fibrosis and fibrosis resolution are warranted.

Microchimeric fetal cells play a role in maternal wound healing after pregnancy

Fetal cells persist in mothers for decades after delivery: in a phenomenon called fetal microchimerism. While persistent fetal cells were first implicated in autoimmune disease, parallel studies in animal and human pregnancy now suggest that microchimeric fetal cells play a role in the response to tissue injury. The aim of this study was to investigate the impact of fetal microchimeric cells in the adult wound, using caesarean section (CS) as a model of wound healing in pregnancy. XY-FISH (fluorescence in situ hybridization) and immunostaining was used in multiple tissue sections from CS skin biopsies from 70 women, to locate, quantitate and characterize microchimeric male presumed-fetal cells. Y-FISH and Nested PCR was used to confirm XY-FISH results. XY-FISH demonstrated the presence of isolated 0-9 male fetal cells per section in the epidermis of the healed CS scars from only those women who had their first male child by CS. Both Y-FISH and Y-PCR confirmed the presence of fetal cells in CS scars. Combined FISH and immunostaining showed all male fetal cells present were keratinocytes, as they expressed cytokeratin, and were almost exclusively located in epidermis. Microchimeric fetal cells also expressed Collagen I, III, and TGF-β3 in healed maternal scars. Identification of male-presumed fetal cells in healed maternal CS scars after pregnancy suggests that, possibly in response to signals produced by maternal skin injury at CS, fetal cells migrate to the site of damage to become involved in maternal tissue repair, or proliferate locally.

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.

Scarless wound healing: chasing the holy grail

Over 100 million patients acquire scars in the industrialized world each year, primarily as a result of elective operations. Although undefined, the global incidence of scarring is even larger, extending to significant numbers of burn and other trauma-related wounds. Scars have the potential to exert a profound psychological and physical impact on the individual. Beyond aesthetic considerations and potential disfigurement, scarring can result in restriction of movement and reduced quality of life. The formation of a scar following skin injury is a consequence of wound healing occurring through reparative rather than regenerative mechanisms. In this article, the authors review the basic stages of wound healing; differences between adult and fetal wound healing; various mechanical, genetic, and pharmacologic strategies to reduce scarring; and the biology of skin stem/progenitor cells that may hold the key to scarless regeneration.

The role of interleukin-10 and hyaluronan in murine fetal fibroblast function in vitro: implications for recapitulating fetal regenerative wound healing

Background

Mid-gestation fetal cutaneous wounds heal scarlessly and this has been attributed in part to abundant hyaluronan (HA) in the extracellular matrix (ECM) and a unique fibroblast phenotype. We recently reported a novel role for interleukin 10 (IL-10) as a regulator of HA synthesis in the fetal ECM, as well as the ability of the fetal fibroblast to produce an HA-rich pericellular matrix (PCM). We hypothesized that IL-10-mediated HA synthesis was essential to the fetal fibroblast functional phenotype and, moreover, that this phenotype could be recapitulated in adult fibroblasts via supplementation with IL-10 via an HA dependent process.

Methodology/Principal Findings

To evaluate the differences in functional profile, we compared metabolism (MTS assay), apoptosis (caspase-3 staining), migration (scratch wound assay) and invasion (transwell assay) between C57Bl/6J murine fetal (E14.5) and adult (8 weeks) fibroblasts. We found that fetal fibroblasts have lower rates of metabolism and apoptosis, and an increased ability to migrate and invade compared to adult fibroblasts, and that these effects were dependent on IL-10 and HA synthase activity. Further, addition of IL-10 to adult fibroblasts resulted in increased fibroblast migration and invasion and recapitulated the fetal phenotype in an HA-dependent manner.

Conclusions/Significance

Our data demonstrates the functional differences between fetal and adult fibroblasts, and that IL-10 mediated HA synthesis is essential for the fetal fibroblasts' enhanced invasion and migration properties. Moreover, IL-10 via an HA-dependent mechanism can recapitulate this aspect of the fetal phenotype in adult fibroblasts, suggesting a novel mechanism of IL-10 in regenerative wound healing.

A mouse fetal skin model of scarless wound repair

Early in utero, but not in postnatal life, cutaneous wounds undergo regeneration and heal without formation of a scar. Scarless fetal wound healing occurs across species but is age dependent. The transition from a scarless to scarring phenotype occurs in the third trimester of pregnancy in humans and around embryonic day 18 (E18) in mice. However, this varies with the size of the wound with larger defects generating a scar at an earlier gestational age. The emergence of lineage tracing and other genetic tools in the mouse has opened promising new avenues for investigation of fetal scarless wound healing. However, given the inherently high rates of morbidity and premature uterine contraction associated with fetal surgery, investigations of fetal scarless wound healing in vivo require a precise and reproducible surgical model. Here we detail a reliable model of fetal scarless wound healing in the dorsum of E16.5 (scarless) and E18.5 (scarring) mouse embryos.

More than just a filler - the role of hyaluronan for skin homeostasis

In recent years, hyaluronan (HA) has become an increasingly attractive substance as a non-immunogenic filler and scaffolding material in cosmetic dermatology. Despite its wide use for skin augmentation and rejuvenation, relatively little is known about the molecular structures and interacting proteins of HA in normal and diseased skin. However, a comprehensive understanding of cutaneous HA homeostasis is required for future the development of HA-based applications for skin regeneration. This review provides an update on HA-based structures, expression, metabolism and its regulation, function and pharmacological targeting of HA in skin.

Knocking out Smad3 favors allogeneic mouse fetal skin development in adult wounds

Fetal skin development represents a process of the interaction between skin progenitor cells and their unique extracellular matrix niche, which is also important for the mechanism study of skin progenitor cell differentiation and fetal scarless wound healing. Thus, a change in the niche environment, such as altered expression levels of growth factors or cytokines, may also change the outcome of fetal skin development. This study tested the hypothesis that deletion of mouse Smad3 creates a favorable environment for fetal skin development in adult wounds. Fetal skin of green fluorescent protein mouse (C57BL/B6) of gestational day 16.5 was respectively transplanted to the wound beds of wild-type (WT), heterozygous (HT), and homologous (KO) Smad3 deletion mice (C57BL/B6 × 129SV). The results showed that green fluorescent protein fetal mouse skin after its transplantation developed much better into hair follicle containing skin in KO or HT wound beds than in WT wound beds with significant differences in the number of follicles per mm(2) among the three groups at 1, 2, and 3 weeks posttransplantation (p < 0.05). In addition, less fibrosis was observed in KO wounds than in HT and WT wounds with significant difference in the wound bed thickness among the three groups at 3 weeks posttransplantation (p < 0.05). Interestingly, there was a delayed graft rejection in the KO group when compared with the HT and WT groups. In conclusion, deletion of Smad3 in a wound bed creates a better environment for skin progenitor cell differentiation and fetal skin development. Translation of such a concept to the creation of a wound environment that is favorable for adult stem cell differentiation and skin appendage formation may become an important strategy for the regeneration of wounded skin.

Skin wound healing and scarring: fetal wounds and regenerative restitution

The adverse physiological and psychological effects of scars formation after healing of wounds are broad and a major medical problem for patients. In utero, fetal wounds heal in a regenerative manner, though the mechanisms are unknown. Differences in fetal scarless regeneration and adult repair can provide key insight into reduction of scarring therapy. Understanding the cellular and extracellular matrix alterations in excessive adult scarring in comparison to fetal scarless healing may have important implications. Herein, we propose that matrix can be controlled via cellular therapy to resemble a fetal-like matrix that will result in reduced scarring.

Tissue engineering and regenerative repair in wound healing

Wound healing is a highly evolved defense mechanism against infection and further injury. It is a complex process involving multiple cell types and biological pathways. Mammalian adult cutaneous wound healing is mediated by a fibroproliferative response leading to scar formation. In contrast, early to mid-gestational fetal cutaneous wound healing is more akin to regeneration and occurs without scar formation. This early observation has led to extensive research seeking to unlock the mechanism underlying fetal scarless regenerative repair. Building upon recent advances in biomaterials and stem cell applications, tissue engineering approaches are working towards a recapitulation of this phenomenon. In this review, we describe the elements that distinguish fetal scarless and adult scarring wound healing, and discuss current trends in tissue engineering aimed at achieving scarless tissue regeneration.

Hyaluronic acid, an important factor in the wound healing properties of amniotic fluid: in vitro studies of re-epithelialisation in human skin wounds

Foetal wounds are unique in their ability to heal rapidly without forming scars. The amniotic fluid, rich in nutrients, growth factors, and hyaluronic acid, surrounds the foetus and is essential to foetal wound healing. The wound healing properties of foetal wounds may be the result of high concentrations of hyaluronic acid. This study aimed to verify that amniotic fluid induces re-epithelialisation in human skin wounds in vitro and to study whether this ability is dependent on hyaluronic acid. Standard deep dermal wounds were produced in vitro in human skin. The skin samples, with a central wound, were incubated in different culture media. Varying concentrations of amniotic fluid and amniotic fluid with added hyaluronidase were tested, and re-epithelialisation was assessed at 3, 7, and 12 days using light microscopy, after staining with haematoxylin and eosin. Amniotic fluid 50% resulted in a significantly higher (p < 0.05) grade of re-epithelialisation than Dulbecco's modified Eagle's medium and 10% amniotic fluid at all time points. When 50% amniotic fluid was compared with 10% foetal calf serum, no significant difference was found in grades of re-epithelialisation on days 3 and 12 and significantly higher grades of re-epithelialisation on day 7 (p < 0.05). Degradation of hyaluronic acid in the medium that contained 50% amniotic fluid gave significantly impaired re-epithelialisation (p < 0.05) on culture days 3 and 7. In conclusion, amniotic fluid promotes accelerated re-epithelialisation and hyaluronic acid is an important ingredient.

Effects of a cross-linked hyaluronic acid based gel on the healing of open wounds in dogs

OBJECTIVE

To compare effects of a cross-linked hyaluronic acid (HA) based gel (CMHA-S) to a standard wound management protocol on the healing of acute, full-thickness wounds in dogs.

STUDY DESIGN

A prospective, controlled, experimental study.

ANIMALS

Purpose-bred, adult, female beagles (n = 10).

METHODS

Two 2 × 2 cm wounds were surgically created bilaterally on the trunk of each dog and each side randomized to treatment (CMHA-S) or control (CON) groups. Total and open wound areas were measured with digital image planimetry at 15 time points. From these data, percent contraction and percent epithelialization were calculated. Tissue biopsies were obtained at 6 time points and histologic features were scored.

RESULTS

Total wound area was significantly larger and percent contraction was significantly less in CMHA-S compared to CON wounds at all data points between days 9 and 18. At day 25, and for the remainder of the study, CMHA-S wounds were smaller and contracted more than CON wounds, reaching significance at day 32. Percent epithelialization was significantly less in CMHA-S compared to CON wounds at all data points after day 11. Histologically, fibroblastic cellular infiltration was significantly higher in CMHA-S wounds at day 21.

CONCLUSIONS

CMHA-S wounds healed more slowly than CON wounds. This HA-based gel is not indicated in acute, full-thickness skin wounds in dogs as administered in this study. However, treatment may be beneficial in the mid-to-late repair stage of healing, or if scar minimization is desired. Further studies to evaluate the effects of the CMHA-S gel on canine wounds are indicated.

Peritoneal drainage versus laparotomy as initial surgical treatment for perforated necrotizing enterocolitis or spontaneous intestinal perforation in preterm low birth weight infants

BACKGROUND

Standard surgical management of infants with perforated necrotizing enterocolitis (NEC) or spontaneous intestinal perforation (SIP) is laparotomy with the resection of the necrotic or perforated segments of the intestine. Peritoneal drainage is an alternative approach to the management of such infants.

OBJECTIVES

To evaluate the benefits and risks of peritoneal drainage compared to laparotomy as the initial surgical treatment for perforated NEC or SIP in preterm infants.

SEARCH STRATEGY

Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library 2010, Issue 3), MEDLINE (1966 to July 2010), EMBASE (1980 to July 2010), CINAHL (1982 to July 2010), previous reviews and cross-references were searched. Abstracts of paediatric academic society meetings were also searched (online: 2000 to 2009; handsearching Pediatric Research: 1995 to 2000).

SELECTION CRITERIA

All randomised or quasi-randomised controlled trials in preterm (< 37 weeks gestation), low birth weight (< 2500 g) infants with perforated NEC or SIP allocated to peritoneal drainage or laparotomy as initial surgical treatment.

DATA COLLECTION AND ANALYSIS

Data were excerpted from the trial reports and analysed according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Only two randomised controlled trials (RCT) met the eligibility criteria. Overall, no significant differences were seen between the peritoneal drainage and laparotomy groups regarding the incidence of mortality within 28 days of the primary procedure (28/90 versus 30/95; typical relative risk (RR) 0.99, 95% CI 0.64 to 1.52; N = 185, two trials); mortality by 90 days after the primary procedure (typical RR 1.05, 95% CI 0.71 to 1.55; N = 185, two trials) and the number of infants needing total parenteral nutrition for more than 90 days (typical RR 1.18, 95% CI 0.72 to 1.95; N = 116, two trials). Nearly 50% of the infants in the peritoneal drainage group could avoid the need for laparotomy during the study period (44/90 versus 95/96; typical RR 0.49, 95% CI 0.39 to 0.61; N = 186, two trials). One study found that the time to attain full enteral feeds in infants ≤ 1000 g was prolonged in the peritoneal drainage group (mean difference (MD) 20.77, 95% CI 3.62 to 37.92).

AUTHORS' CONCLUSIONS

Evidence from two RCTs suggests no significant benefits or harms of peritoneal drainage over laparotomy. However, due to the very small sample size, clinically significant differences may have easily been missed. No firm recommendations can be made for clinicians. Large multicentre randomised controlled trials are needed to address this question definitively.

Icodextrin reduces adhesion formation following gynecological surgery in rabbits

BACKGROUND

Adhesion is a common complication of gynecology surgery so different barrier agents and solutions have been used during these operations to separate and protect tissues from adhesion after surgery. Adept is one of these solutions that have been postulated to reduce the chance of adhesion following gynecolgy surgery.

OBJECTIVE

To evaluate the effect of 4% icodextrin in reducing adhesion formation in comparing with sterile water and human amniotic fluid in rabbits.

MATERIALS AND METHODS

In this prospective experimental study 30 white Newzealand female rabbits were selected and randomized in to three treatment groups. The rabbits were anesthetized and an abdominal incison was made, uterine horns were abrated with gauze until bleeding occurred. Before closing the abdomen, the traumatized area was irrigated either by 30cc of sterile water, 30cc of 4% Adept or 30cc of human amniotic fluid. The solutions were labeled only as solutions A (steriel water), B (icodextrin), or C (human amniotic fluid). On the seventh day after surgery, second laparotomy was performed to determine and compare adhesion formation in rabbits.

RESULTS

There was significant difference between mean score of adhesions in 4% icodextrin group (2.1±0.70) in comparison to sterile water group (10.4±0.60) and amniotic fluid group (8.7±0.84). But the difference between mean score of adhesions in amniotic fluid group in comparison to sterile water group was not significant (8.7±0.84) versus (10.4±0.60).

CONCLUSION

The use of 4% icodextrin solution was more effective than human amniotic fluid and sterile water in reducing adhesion formation in a gynecological surgery model in rabbits.

Scarless fetal wound healing: a basic science review

SUMMARY

Scar formation is a major medical problem that can have devastating consequences for patients. The adverse physiological and psychological effects of scars are broad, and there are currently no reliable treatments to prevent scarring. In contrast to adult wounds, early gestation fetal skin wounds repair rapidly and in the absence of scar formation. Despite extensive investigation, the exact mechanisms of scarless fetal wound healing remain largely unknown. For some time, it has been known that significant differences exist among the extracellular matrix, inflammatory response, cellular mediators, and gene expression profiles of fetal and postnatal wounds. These differences may have important implications in scarless wound repair.

Effects of human amniotic fluid and membrane in the treatment of Achilles tendon ruptures in locally corticosteroid-induced Achilles tendinosis: an experimental study on rats

BACKGROUND

To determine the effects of human amniotic fluid and membrane in the treatment of Achilles tendon ruptures, 72 tendons of 36 Wistar rats were injected with betamethasone sodium phosphate.

METHODS

By the end of fourth week, both tendons were tenotomized and repaired, then the samples were divided into three groups. The first group was left untreated after suturing. Human amniotic fluid was injected to the second and amniotic fluid and membrane were both administered to the third group. Twenty-four tendons were scored at the end of the first week, and 24 at the end of the second week histopathologically, and 24 biomechanically at the end of the third week.

RESULTS

There was a significant statistical difference only between the histopathological results of Groups 2 and 3 at the first week.

CONCLUSIONS

Human amniotic membrane and fluid do not add anything to the healing process of Achilles tendon ruptures in the early phase.

Early Fetal Healing as a Model for Adult Organ Regeneration

Evidence is provided pointing out certain basic similarities, though not an identity, between the mechanisms of early fetal regeneration and induced organ regeneration in adults. These similarities favor a model of induced organ regeneration in which biologically active scaffolds block wound contraction and scar formation.

Heavy silicone oil versus standard silicone oil as vitreous tamponade in inferior PVR (HSO Study): design issues and implications

PURPOSE

Proliferative vitreoretinopathy (PVR) is the most important reason for blindness following retinal detachment. Presently, vitreous tamponades such as gas or silicone oil cannot contact the lower part of the retina. A heavier-than-water tamponade displaces the inflammatory and PVR-stimulating environment from the inferior area of the retina. The Heavy Silicone Oil versus Standard Silicone Oil Study (HSO Study) is designed to answer the question of whether a heavier-than-water tamponade improves the prognosis of eyes with PVR of the lower retina.

METHODS

The HSO Study is a multicentre, randomized, prospective controlled clinical trial comparing two endotamponades within a two-arm parallel group design. Patients with inferiorly and posteriorly located PVR are randomized to either heavy silicone oil or standard silicone oil as a tamponading agent. Three hundred and fifty consecutive patients are recruited per group. After intraoperative re-attachment, patients are randomized to either standard silicone oil (1000 cSt or 5000 cSt) or Densiron((R)) as a tamponading agent. The main endpoint criteria are complete retinal attachment at 12 months and change of visual acuity (VA) 12 months postoperatively compared with the preoperative VA. Secondary endpoints include complete retinal attachment before endotamponade removal, quality of life analysis and the number of retina affecting re-operation within 1 year of follow-up.

RESULTS

The design and early recruitment phase of the study are described.

CONCLUSIONS

The results of this study will uncover whether or not heavy silicone oil improves the prognosis of eyes with PVR.

Serum-dependent effects on adult and fetal tendon fibroblast migration and collagen expression

Cell migration and extracellular matrix synthesis play an important role in the wound-healing response to injury. Several studies have described differences in migratory behavior and collagen biosynthetic activity in adult vs. fetal skin fibroblasts. The objective of this study was to examine the serum- and age-dependent effects on cell migration and collagen expression in tendon fibroblasts. Medial tendon fibroblasts were isolated from pregnant ewes and their fetuses, and cultured with and without serum for up to 7 days. Cell migration was determined by quantitative image analysis, and collagen expression was assessed by reverse transcription-polymerase chain reaction and immunohistochemical staining. In serum-containing medium, tendon fibroblasts migrated significantly faster than cells in serum-free medium. Additionally, fetal tendon fibroblasts migrated significantly faster than adult tendon fibroblasts under both culture conditions. The expression of types I and III collagen mRNA was significantly up-regulated in tendon cell populations in serum-free medium compared with those in serum-containing medium. Quantitative assessment of collagen staining indicated that fetal tenocytes produced more type I collagen than adult tenocytes under both culture conditions. These findings suggest that there is an inherent difference between adult and fetal tendon fibroblasts, which may have implications in the wound-healing response in tendons.

Experimental models and high-throughput diagnostics for tissue regeneration

During wound healing, cells recreate functional structures to regenerate the injured tissue. Understanding the healing process is essential for the development of new concepts and the design of novel biomimetic approaches for delivery of cells, genes and growth factors to accelerate tissue regeneration. To this end, realistic experimental models and high-throughput diagnostics are necessary to understand the molecular mechanisms of healing and reveal the genetic networks that determine tissue repair versus regeneration. Following a brief overview of the biology of wound healing, this review covers the in vitro and in vivo models that are employed at present to study the healing process. Discussion then covers the application of high-throughput genomic and proteomic technologies in epithelial development, living skin substitutes and wound healing. Finally, this review provides a perspective on novel technologies that should be developed to facilitate the understanding of wound healing complications and the design of therapeutics that target the underlying deficiencies.

Molecular Stenting with a Crosslinked Hyaluronan Derivative Inhibits Collagen Gel Contraction

Adult burn wounds, which lack hyaluronan (HA), often undergo excessive tissue remodeling and contraction. In contrast fetal wounds, which contain large amounts of HA, undergo remodeling that culminates in a scarless repair or regeneration. Therefore, adding a HA derivative to burn wounds would better mimic the fetal extracellular matrix and could reduce contraction. To test this hypothesis, we determined the effects of HA and its two derivatives on fibroblast-mediated, collagen gel contraction, an assay widely used to mimic in vivo wound contraction. Interestingly, high molecular weight HA (HMW HA) facilitated collagen gel contraction, whereas a thiol-functionalized derivative HA-DTPH weakly inhibited contraction. In contrast, polyethylene glycol diacrylate (PEGDA)-crosslinked HA-DTPH (HA-DTPH-PEGDA) strongly inhibited contraction in a concentration-dependent manner. Immunofluorescence staining of cellular actin showed that this inhibition was not owing to reduced cell attachment or spreading. Furthermore, the supernatant of contracted collagen-HMW HA gels contained greater amounts of HA than those found in the supernatant of collagen-HA-DTPH-PEGDA gels, suggesting that HMW HA facilitates contraction by effectively diffusing out of the collagen gels. Therefore, the results suggest that the crosslinking of HA-DTPH enhances the structural mechanics of collagen/HA-DTPH composites, which resists the fibroblast contractile forces and may, therefore, be able to reduce excessive wound contraction observed in pathological conditions.

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.

Effect of human amniotic fluid on bone healing

BACKGROUND

Bone healing continues to pose challenges for researchers and clinicians working in the field of plastic surgery. Complete bone regeneration cannot be obtained in critical size osseous defects without the application of osteogenic or osteoinductive bone material. In this study, we hypothesized that because extracellular matrix components are known to play a major role in the first steps of healing during bone or injury healing and because hyaluronic acid as chondroitin sulfate is recognized as an osteogenic compound without osteoinductive activity, human amniotic fluid, which contains high concentrations of hyaluronic acid, gyaluronic acid -stimulating activator, and other factors, might accelerate bone healing when applied subperiosteally to rabbit calvarial defects.

MATERIALS AND METHODS

We created 20 calvarial defects in 10 12-week-old New Zealand white rabbits who were divided into 2 groups. Group 1 defects were instilled with human amniotic fluid, whereas the group with contralateral defects, i.e., group 2, were given with same amount of normal saline solution. We then measured the density of the bone that formed over the defects using computed tomography at the third, fourth, fifth, and sixth weeks postoperatively. After this period, the defects were harvested for histopathologic evaluation.

RESULTS

The defects from group 1, which were treated with human amniotic fluid, showed significantly higher ossification than the group 2 defects, which were instilled with saline solution. Histological examination at 6 weeks postoperatively revealed that the defects treated with human amniotic fluid (group 1) had superior ossification compared with the control group defects (group 2).

CONCLUSION

Because of its positive effects on bone healing and also because of its ability to be stored in deep freeze if made cell-free, human amniotic fluid would appear to be a useful adjunct in the treatment of bone healing.

Effect of amniotic fluid on peri-implant capsular formation

Although commonly used biomaterials are physically and chemically stable, nonimmunogenic, and nontoxic, implanted and blood-contact biomaterials trigger a wide variety of unwanted responses, including inflammation, thrombosis, infection, and fibrosis. Peri-implant fibrosis is the response most commonly seen by plastic surgeons. In this study, the authors hypothesized that as hyaluronic acid (HA) reduces scar formation by inhibiting the activity of mononuclear phagocytes and lymphocytes, human amniotic fluid (HAF), which contains high concentrations of HA, HA-stimulating activator (HASA), and other factors, might prevent the formation of fibrous capsules and capsule contracture when applied intraluminally. Two 1 x 1-cm silicone blocks were placed dorsally into separate surgically created pockets underneath the panniculus carnosus muscle, distant from the incisions, in each of the 10 rats in the study. At the time of implant insertion, 2 ml of HAF was instilled into the cranially located pockets in group 1, whereas 2 ml of saline solution was instilled into the caudally located pockets in group 2. After 6 months, intracapsular static and dynamic pressure measurements were made, and then all the peri-implant capsules were excised and fixed in 10% neutral buffered formaldehyde. The thicknesses of the capsules were measured in three different areas of each section, and a mean was calculated. Capsular firmness, according to the static and dynamic pressure readings, was significantly greater in the control group, which had saline solution introduced into the pocket, than in the treatment group, which had HAF used in the same manner. The mean total thickness of the capsules surrounding the implants was 876.7 microm in the control group, as comparied with 466.8 microm in the HAF-treated group. This difference was statistically significant (p < 0.001). Because of its ability to reduce capsular thickness and firmness and also because it can be stored in a freezer if it is prepared in a cell-free manner, HAF would appear to be a useful adjunct in the prevention of capsular contracture formation.

Effects of human amniotic fluid on cartilage regeneration from free perichondrial grafts in rabbits

After the chondrogenic potential of free grafts of perichondrium was shown in several experimental studies, perichondrium has been used to reconstruct cartilage tissue in various clinical situations. This study investigates the effects of human amniotic fluid on neochondrogenesis from free perichondrial grafts in a rabbit model. Since this fluid contains high concentrations of hyaluronic acid, hyaluronic acid-stimulating activator, growth factors, and extracellular matrix precursors during the second trimester, it may have a stimulating effect on neochondrogenesis. Perichondrial grafts, measuring 20 x 20 mm2 were obtained from the ears of 144 New Zealand young rabbits and were sutured over the paravertebral muscles. The rabbits were randomly divided into three groups with 48 rabbits per group. In group 1, 0.3 ml human amniotic fluid, and in group 2, 0.3 ml saline were injected underneath the perichondrial grafts. Group 3 formed the control group in which no treatment was given. Histologically, neochondrogenesis was evaluated in terms of cellular form and graft thickness at 2, 4, 6, and 8 weeks after surgery. In group 1, the mature cartilage was generated quickly and the cartilage plate in this group was significantly thick and extensive when compared with groups 2 and 3 at 8 weeks ( p<0.05 ANOVA). In conclusion, our study shows that human amniotic fluid enhances neochondrogenesis from free perichondrial grafts. The rich content of hyaluronic acid and growth factors possibly participate in this result.