The influence of human amniotic fluid on the potential of rabbit ear perichondrial flaps to form cartilage tissue

Cell-Free Amniotic Fluid and Regenerative Medicine: Current Applications and Future Opportunities

Amniotic fluid (AF) provides critical biological and physical support for the developing fetus. While AF is an excellent source of progenitor cells with regenerative properties, recent investigations indicate that cell-free AF (cfAF), which consists of its soluble components and extracellular vesicles, can also stimulate regenerative and reparative activities. This review summarizes published fundamental, translational, and clinical investigations into the biological activity and potential use of cfAF as a therapeutic agent. Recurring themes emerge from these studies, which indicate that cfAF can confer immunomodulatory, anti-inflammatory, and pro-growth characteristics to the target cells/tissue with which they come into contact. Another common observation is that cfAF seems to promote a return of cells/tissue to a homeostatic resting state when applied to a model of cell stress or disease. The precise mechanisms through which these effects are mediated have not been entirely defined, but it is clear that cfAF can safely and effectively treat cutaneous wounds and perhaps orthopedic degenerative conditions. Additional applications are currently being investigated, but require further study to dissect the fundamental mechanisms through which its regenerative effects are mediated. By doing so, rational design can be used to fully unlock its potential in the biotechnology lab and in the clinic.

Comparative Analysis of Co-Cultured Amniotic Cell-Conditioned Media with Cell-Free Amniotic Fluid Reveals Differential Effects on Epithelial–Mesenchymal Transition and Myofibroblast Activation

Myofibroblast activation is a cellular response elicited by a variety of physiological or pathological insults whereby cells initiate a coordinated response intended to eradicate the insult and then revert back to a basal state. However, an underlying theme in various disease states is persistent myofibroblast activation that fails to resolve. Based on multiple observations, we hypothesized that the secreted factors harvested from co-culturing amniotic stem cells might mimic the anti-inflammatory state that cell-free amniotic fluid (AF) elicits. We optimized an amnion epithelial and amniotic fluid cell co-culture system, and tested this hypothesis in the context of myofibroblast activation. However, we discovered that co-cultured amniotic cell conditioned media (coACCM) and AF have opposing effects on myofibroblast activation: coACCM activates the epithelial–mesenchymal transition (EMT) and stimulates gene expression patterns associated with myofibroblast activation, while AF does the opposite. Intriguingly, extracellular vesicles (EVs) purified from AF are necessary and sufficient to activate EMT and inflammatory gene expression patterns, while the EV-depleted AF potently represses these responses. In summary, these data indicate that coACCM stimulates myofibroblast activation, while AF represses it. We interpret these findings to suggest that coACCM, AF, and fractionated AF represent unique biologics that elicit different cellular responses that are correlated with a wide variety of pathological states, and therefore could have broad utility in the clinic and the lab.

Placental Tissues as Biomaterials in Regenerative Medicine

Placental tissues encompass all the tissues which support fetal development, including the placenta, placental membrane, umbilical cord, and amniotic fluid. Since the 1990s there has been renewed interest in the use of these tissues as a raw material for regenerative medicine applications. Placental tissues have been extensively studied for their potential contribution to tissue repair applications. Studies have attributed their efficacy in augmenting the healing process to the extracellular matrix scaffolds rich in collagens, glycosaminoglycans, and proteoglycans, as well as the presence of cytokines within the tissues that have been shown to stimulate re-epithelialization, promote angiogenesis, and aid in the reduction of inflammation and scarring. The compositions and properties of all birth tissues give them the potential to be valuable biomaterials for the development of new regenerative therapies. Herein, the development and compositions of each of these tissues are reviewed, with focus on the structural and signaling components that are relevant to medical applications. This review also explores current configurations and recent innovations in the use of placental tissues as biomaterials in regenerative medicine.

Proteomic Analysis and Cell Viability of Nine Amnion, Chorion, Umbilical Cord, and Amniotic Fluid-Derived Products

OBJECTIVE

Amnion products are used in various musculoskeletal surgeries and as injections for joint pain with conflicting reports of cell viability and protein contents. The objective of this study was to determine the full proteome and examine cell viability in 9 commercial amnion products using an unbiased bottom-up shotgun proteomics approach and confocal microscopy.

DESIGN

Products were subjected to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and searched against a UniProt Homo sapiens database. Relative protein abundance was determined for each sample. Based on proteomics results, lumican was measured by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis was performed for interleukin-1 receptor antagonist (IL-1Ra) and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2). Cell viability was determined by calcein AM (live) and ethidium homodimer (dead) staining and confocal microscopy.

RESULTS

Proteomic analysis revealed 919 proteins in the nine products. Proteins were primarily collagens, keratin, and albumin. Lumican, a small leucine-rich proteoglycan (SLRP) was found in all samples. Western blot analysis for IL-1Ra and TIMP-2 indicated presence of both proteins, with nonspecific antibody binding also present in all samples. No live cells were identified in any product.

CONCLUSIONS

Several novel proteins were identified through proteomics that might impart the beneficial effects of amnion products, including SLRPs, collagens, and regulators of fibroblast activity. IL-1Ra and TIMP-2 were identified, but concentrations measured by ELISA may be falsely increased due to nonspecific antibody binding. The concept that the amnion tissues provide live cells to aid in tissue regeneration cannot be supported by the findings of this study.

The effects of human amniotic fluid and different bone grafts on vertebral fusion in an experimental rat model

Objective

The high risk of nonunion represents a challenge in vertebral surgery, thus stimulating new strategies to improve fusion rates. We investigated the effect of 2 different bone grafts and amniotic fluid application on radiologically and histologically evaluated vertebral fusion in an experimental rat model.

Materials and methods

Forty-eight 24-week-old Sprague Dawley rats were included and assigned into 1 of 4 groups: allograft group, allograft plus human amniotic fluid group, demineralized bone matrix (DBM) group, or DBM plus human amniotic fluid group. After decortication and L4–L6 spinal fusion, study treatments were applied. Fusion in each rat was examined radiologically and histologically 8 weeks after the intervention.

Results

The group that received only allograft had better radiologic scores (median = 3.5; range = 3–4) when compared with the group that received only DBM (median = 2; range = 1–4) (P = 0.002); however, histologic scores did not differ. When amniotic fluid was added to the grafting, allograft-based treatments performed better than DBM-based treatments both on radiologic (median = 4; range = 3–4 vs median = 3; range = 3–4; P = 0.003) and histologic (median = 7; range = 6–7 vs median = 5; range = 3–6; P < 0.001) evaluation. Addition of amniotic fluid did not result in better outcomes in the rats that received DBM-based treatments but based on histologic evaluation, rats that received allograft-based treatments benefited from this application.

Conclusions

Amniotic fluid seems to have an enhancing effect on posterior spinal fusion, particularly when combined with allograft.

Effect of freeze dried bovine amniotic membrane extract on full thickness wound healing

This study explored the feasibility of development of solubilized amniotic membrane extract (AME) as a potential wound healing substrate with improved efficacy. Bovine amniotic membrane was extracted using a mixture of acetic acid and 2-mercaptopropionic acid under sonication, which was followed by the frozen, and then lyophilized processes. The effects of AME on cell migration and growth properties were evaluated from 0 to 24 h of post injury using primary human foreskin fibroblast monolayer culture with one line scratch as an in vitro wound model. Its wound healing efficacy and scar preventive effects were investigated using whole thickness biopsy punch (8 mm) wound model obtained from rabbit ear. Intra dermal injections of AME fluid (10 μl of 1.2 μg/μl) on four wound sites were performed at 1 h pre injury, post 1, 2 and 3 day. The processes and levels of re-epithelialization and dermal regeneration were examined through histological assessment with H-E staining. In cell migration study conducted at 24 h post injury, AME (1.7 μg/ml) treated cells significantly increased wound closure with 54.9 % compared to control. Histological image analysis on AME treated wound sites at 36 days post injury showed properly developed epidermal basal cell layers and weave-like dermal collagen bundles, whereas those of untreated control skin showed over-proliferation of epidermis and aggregated collagen bundles with defected dermal regeneration. The results of this study verified the feasibility of dermal injections of freeze dried AME as a potential wound healing substrate which can promote epidermal and dermal regeneration, while avoiding undesirable hyper-proliferation of damaged tissue.

Histological assessment of skin grafts stored in amniotic fluid and saline

We investigated the efficacy of amniotic fluid as a substance in which to store grafts; it is rich in nutrients, proteins, and growth factors, and has well-known antimicrobial features. We compared it with the widely-used and practical saline. Split-thickness grafts 4 × 4 cm were prepared from the back of 20 rats and divided into four groups (n = 5 each). The rolled grafts were wrapped in gauze dampened with saline or amniotic fluid and placed into refrigerators in sterile containers for storage. On days 7, 14, 21, and 28, histological examinations were made. A semiquantitative evaluation of the histological damage to the skin was made by scoring its degree of severity. Compared with saline, histological scores in the grafts stored in amniotic fluid were found to be significantly lower on the 14th, 21st, and 28th days (p values on days 14, 21, and 28; cell swelling: 0.014, 0.006, and 0.005, respectively; nuclear swelling: 0.003, 0.006, and 0.007, respectively; nuclear pleomorphism: 0.004, 0.005, and 0.003, respectively; nuclear haloes: 0.015, 0.005, and 0.005, respectively; nuclear pyknosis: 0.003, 0.005, and 0.003, respectively; dermo-epidermal clefting: 0.005, 0.003, and 0.003, respectively; eosinophilia and mitosis: 0.003, 0.006, and 0.004, respectively; dermal collagen: 0.003, 0.003, and 0.003, respectively). Amniotic fluid maintained preservation better for skin grafts than saline. Comparison with other modern storage media would be beneficial.

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.

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.

Effects of human amniotic fluid on peripheral nerve scarring and regeneration in rats

OBJECT

Peripheral nerve repair surgery is still replete with challenges. Despite technical improvements in microsurgery, classic methods of nerve repair have failed to provide satisfactory results. The purpose of this study was to investigate the effects of amniotic fluid from humans on peripheral nerve scarring and regeneration in rats.

METHODS

Forty adult Sprague-Dawley rats were used in this study. After the right sciatic nerve in each rat was transected and repaired using an epineural suture procedure, the nerves were divided into two groups according to the solution applied around the repair site: experimental group, 0.3 ml human amniotic fluid (HAF); and control group, 0.3 ml saline. Macroscopic and histological evaluations of peripheral nerve scarring were performed 4 weeks postsurgery. Nerves treated with HAF demonstrated a significant reduction in the amount of scar tissue surrounding the repair site (p < 0.05). No evidence of a reaction against HAF was noted. Functional nerve regeneration was measured once every 2 weeks by using a sciatic function index until 12 weeks postsurgery. Functional recovery in nerves treated with amniotic fluid occurred significantly faster than that in nerves treated with saline (p < 0.05). Peripheral nerve regeneration was evaluated histomorphologically at 12 weeks postsurgery. Nerves treated with amniotic fluid showed significant improvement with respect to the indices of fiber maturation (p < 0.05).

CONCLUSIONS

Preliminary data show that HAF enhances peripheral nerve regeneration. The preventive effect of HAF on epineural scarring and the rich content of neurotrophic and neurite-promoting factors possibly contribute to this result.