Amniotic Product Treatments: Clinical and Basic Science Evidence

Potential novel role of the human amniotic membrane as a sustainable hemostat

OBJECTIVES

Acute hemorrhage can cause significant morbidity and mortality arising from trauma, bleeding disorders, surgical procedures, or obstetric complications. Surgical hemostasis methods may fail to stop acute bleeding due to the complex bleeding dynamics of each bleeding type. Therefore, developing safe and effective topical hemostatic agents remains crucial. The human amniotic membrane (hAM) has established clinical evidence of effectiveness in promoting wound healing and tissue regeneration. Despite its unique biological and immunologic properties and its structural composition of established hemostatic elements, the hemostatic role of hAM has not been yet explored. The present study aimed to investigate this potential role and to describe the development protocol and characterization of hAM-derived topical hemostat.

METHODS

Surface electron microscope (SEM) imaging and Fourier transform infrared (FTIR) spectroscopy were used for characterization, and mouse models with induced peritoneal and tail wound bleeding were employed to evaluate the hemostatic effectiveness using physiological studies, in comparison to a chitosan-based combat-scale hemostat.

RESULTS

The hAM hemostat showed a distinctive composition by SEM and FTIR. Applying equal masses of the hAM hemostat, the commercial hemostat, or a combination reduced peritoneal wound bleeding time to averages of 108.4, 86.2, and 76.8 s, respectively, compared to the control group (300 s). Tail wound bleeding times were similarly reduced with no significant difference between the hAM and the commercial hemostat (P values = 0.29, 0.34 in peritoneal and tail wounds, respectively). Neither hemostat affected coagulation time.

CONCLUSION

This study describes a simple cost-effective preparation protocol for a hAM-based hemostatic agent. The long-recognized safety, sustainability, and immunotolerance advantages of hAM can establish superiority over commercial hemostats with reported safety concerns. Robust research validation in larger-scale bleeding models is required for wider applications and severe bleeding types.

Interposition of acellular amniotic membrane at the tendon to bone interface would be better for healing than overlaying above the tendon to bone junction in the repair of rotator cuff injury

PURPOSE

The retear rate of rotator cuff (RC) after surgery is high, and the rapid and functional enthesis regeneration remains a challenge. Whether acellular amniotic membrane (AAM) helps to promote the healing of tendon to bone and which treatment is better are both unclear. The study aims to investigate the effect of AAM on the healing of RC and the best treatment for RC repair.

METHODS

Thirty-three Sprague Dawley rats underwent RC transection and repair using microsurgical techniques and were randomly divided into the suturing repair only (SRO) group (n = 11), the AAM overlaying (AOL) group (n = 11), and the AAM interposition (AIP) group (n = 11), respectively. Rats were sacrificed at 4 weeks, then examined by subsequent micro-CT, and evaluated by histologic and biomechanical tests. The statistical analyses of one-way ANOVA or Kruskal-Wallis test were performed using with SPSS 23.0. A p < 0.05 was considered a significant difference.

RESULTS

AAM being intervened between tendon and bone (AIP group) or overlaid over tendon to bone junction (AOL group) in a rat model, promoted enthesis regeneration, increased new bone and cartilage generation, and improved collagen arrangement and biomechanical properties in comparison with suturing repair only (SRO group) (AOL vs. SRO, p < 0.001, p = 0.004, p = 0.003; AIP vs. SRO, p < 0.001, p < 0.001, p < 0.001). Compared with the AOL group, the AIP group had better results in micro-CT evaluation, histological score, and biomechanical testing (p = 0 0.039, p = 0.011, p = 0.003, respectively).

CONCLUSION

In the RC repair model, AAM enhanced regeneration of the tendon to bone junction. This regeneration was more effective when the AAM was intervened at the tendon to bone interface than overlaid above the tendon to bone junction.

Stable Housekeeping Genes in Bone Marrow, Adipose Tissue, and Amniotic Membrane-Derived Mesenchymal Stromal Cells for Orthopedic Regenerative Medicine Approaches

The therapeutic effect of mesenchymal stromal cells (MSCs) has been described for a variety of disorders, including those affecting musculoskeletal tissues. In this context, the literature reports several data about the regenerative effectiveness of MSCs derived from bone marrow, adipose tissue, and an amniotic membrane (BMSCs, ASCs, and hAMSCs, respectively), either when expanded or when acting as clinical-grade biologic pillars of products used at the point of care. To date, there is no evidence about the superiority of one source over the others from a clinical perspective. Therefore, a reliable characterization of the tissue-specific MSC types is mandatory to identify the most effective treatment, especially when tailored to the target disease. Because molecular characterization is a crucial parameter for cell definition, the need for reliable normalizers as housekeeping genes (HKGs) is essential. In this report, the stability levels of five commonly used HKGs (ACTB, EF1A, GAPDH, RPLP0, and TBP) were sifted into BMSCs, ASCs, and hAMSCs. Adult and fetal/neonatal MSCs showed opposite HKG stability rankings. Moreover, by analyzing MSC types side-by-side, comparison-specific HKGs emerged. The effect of less performant HKG normalization was also demonstrated in genes coding for factors potentially involved in and predicting MSC therapeutic activity for osteoarthritis as a model musculoskeletal disorder, where the choice of the most appropriate normalizer had a higher impact on the donors rather than cell populations when compared side-by-side. In conclusion, this work confirms HKG source-specificity for MSCs and suggests the need for cell-type specific normalizers for cell source or condition-tailored gene expression studies.

An Update on Orthobiologics: Cautious Optimism

Orthobiologics are rapidly growing in use given their potential to augment healing for multiple musculoskeletal conditions. Orthobiologics consist of a variety of treatments including platelet-rich plasma and stem cells that provide conceptual appeal in providing local delivery of growth factors and inflammation modulation. The lack of standardization in nomenclature and applications within the literature has led to a paucity of high-quality evidence to support their frequent use. The purpose of this review was to describe the current landscape of orthobiologics and the most recent evidence regarding their use.

Preparation of human amniotic membrane for transplantation in different application areas

The human amniotic membrane (hAM) is the inner layer of the placenta and plays protective and nutritional roles for the fetus during pregnancy. It contains multiple growth factors and proteins that mediate unique regenerative properties and enhance wound healing in tissue regeneration. Due to these characteristics hAM has been successfully utilized in ophthalmology for many decades. This material has also found application in a variety of additional therapeutic areas. Particularly noteworthy are the extraordinary effects in the healing of chronic wounds and in the treatment of burns. But hAM has also been used successfully in gynecology, oral medicine, and plastic surgery and as a scaffold for in vitro cell culture approaches. This review aims to summarize the different graft preparation, preservation and storage techniques that are used and to present advantages and disadvantages of these methods. It shows the characteristics of the hAM according to the processing and storage methods used. The paper provides an overview of the currently mainly used application areas and raises new application possibilities. In addition, further preparation types like extracts, homogenates, and the resulting treatment alternatives are described.

Prospective use of amniotic mesenchymal stem cell metabolite products for tissue regeneration

Chronic disease can cause tissue and organ damage constituting the largest obstacle to therapy which, in turn, reduces patients' quality-adjusted life-year. Degenerative diseases such as osteoporosis, Alzheimer's disease, Parkinson's disease, and infectious conditions such as hepatitis, cause physical injury to organs. Moreover, damage resulting from chronic conditions such as diabetes can also culminate in the loss of organ function. In these cases, organ transplantation constitutes the therapy of choice, despite the associated problems of immunological rejection, potential disease transmission, and high morbidity rates. Tissue regeneration has the potential to heal or replace tissues and organs damaged by age, disease, or trauma, as well as to treat disabilities. Stem cell use represents an unprecedented strategy for these therapies. However, product availability and mass production remain challenges. A novel therapeutic alternative involving amniotic mesenchymal stem cell metabolite products (AMSC-MP) has been developed using metabolites from stem cells which contain cytokines and growth factors. Its potential role in regenerative therapy has recently been explored, enabling broad pharmacological applications including various gastrointestinal, lung, bladder and renal conditions, as well as the treatment of bone wounds, regeneration and skin aging due to its low immunogenicity and anti-inflammatory effects. The various kinds of growth factors present in AMSC-MP, namely bFGF, VEGF, TGF-β, EGF and KGF, have their respective functions and activities. Each growth factor is formed by different proteins resulting in molecules with various physicochemical properties and levels of stability. This knowledge will assist in the manufacture and application of AMSC-MP as a therapeutic agent.

The Effect of Amniotic Tissue on Spinal Interventions: A Systematic Review

BACKGROUND

Amniotic membrane tissue has been thought to potentiate healing in many soft tissue conditions. Specifically, recent studies have shown its therapeutic potential for treatment in the setting of spinal pathologies. The purpose of this study is to thoroughly review the existing scientific literature and evidence concerning the clinical use of amniotic membrane-derived biologic agents on postoperative outcomes following spinal surgery.

METHODS

A systematic review was conducted following preferred reporting items for systematic reviews and meta-analyses guidelines using PubMed, Embase, and Cochrane databases up to December 2020 to identify animal and clinical studies examining the therapeutic potential for amniotic membrane tissue in the setting of spinal pathologies (including disc herniation, prevention of epidural fibrosis, and spinal fusion). Studies were broken down into 2 categories: experimental model type and the type of amnion product being analyzed.

RESULTS

A total of 12 studies (4 clinical studies and 8 studies utilizing animal models) met inclusion criteria. Additionally, the major types of amnion product were divided into cryopreserved/freeze-dried amniotic membrane, human amniotic fluid, human amniotic membrane, cross-linked amniotic membrane, and amnion-derived epithelial cells. While heterogeneity of study design precludes definitive specific results reporting, most studies showed positive benefits on healing/outcomes with amniotic augmentation. Specifically, amnion products have shown promising effects in reducing epidural adhesions and scar tissue after spine surgery, improving spinal fusion rate and postoperative pain scores, and promoting better functional outcomes after spine surgery.

CONCLUSIONS

A review of the limited number of reported studies revealed a wide variety of amniotic membrane preparations, treatment regimens, and indications, which limit definitive conclusions. To date, while there is no definitive clinical proof that amniotic tissues enhance tissue repair or regeneration, the aggregate results demonstrate promising basic science and outcomes potential in spinal surgery. Further study is warranted to determine whether this application is appropriate in the clinical setting.

CLINICAL RELEVANCE

This systematic review provides a summary of the existing literature regarding the use of amniotic membrane preparations, treatment regimens, and indications within spinal surgery. With the growing popularity and utilization of biologic agents such as amniotic membrane-derived products in orthopedic and neurologic surgery, this systematic review gives physicians a concise summary on the outcomes and indications associated with amniotic membrane products.

LEVEL OF EVIDENCE: 4

An Initial Injection and a Crossover Injection of Amniotic Suspension Allograft Following Failed Treatment with Hyaluronic Acid or Saline Are Equally Effective in the Treatment of Moderate Symptomatic Knee Osteoarthritis Over 12 Months

PURPOSE

The purpose of this crossover study was to determine the efficacy of amniotic suspension allograft (ASA) for moderate symptomatic knee osteoarthritis following failed treatment with hyaluronic acid (HA) or saline through 12 months' postcrossover injection using patient-reported and safety outcomes.

METHODS

In this multicenter study, 95 patients from a 200-patient single-blind randomized controlled trial were eligible to crossover and receive a single injection of ASA 3 months after failed treatment with HA or saline. Patient-reported outcomes, including Knee Injury and Osteoarthritis Outcome Score (KOOS) and visual analog scale (VAS), were collected out to 12 months postcrossover to determine pain and function. Radiographs and blood were collected for assessment of changes. Statistical analyses were performed using mixed effects model for repeated measures.

RESULTS

Treatment with ASA following failed treatment with HA or saline resulted in significant improvements in KOOS and VAS scores compared with crossover baseline. There were no differences in radiographic measures or anti-human leukocyte antigen serum levels compared with baseline and no severe adverse events reported. In addition, more than 55% of patients were responders at months 3, 6, and 12 as measured by the Outcome Measures in Arthritis Clinical Trials-Osteoarthritis Research Society International simplified responder criteria. There were no significant differences between the original ASA randomized group and crossover cohorts at any of the time points evaluated, suggesting that prior failed treatment with HA or saline did not significantly impact outcomes following treatment with ASA.

CONCLUSIONS

This study showed that patients who previously failed treatment with HA or saline had statistically significant improvements in pain and function scores following a crossover injection of ASA that was sustained for 12 months, as measured by KOOS and VAS. There were no serious adverse events reported, and the injection was safe.

LEVEL OF EVIDENCE

II, prospective cohort study.

Orthobiologic Use in Sports Injuries

Orthobiologics have gained much popularity in recent years but there has not been a large amount of clinical evidence to support their use. In the limited research that has been published, they have been shown to be effective and safe. They can assist in earlier return to activity with the avoidance of surgery. They can also augment current surgical practice to aid in healing and return to sport with few complications. With new medical innovation, there is unfortunately a higher cost for these products. The use of orthobiologics will only grow and so will the need for high-level clinical evidence.

A minimally manipulated preservation and virus inactivation method for amnion/chorion

Allogeneic amnion tissues have been widely used in tissue repair and regeneration, especially a remarkable trend of clinical uses in chronic wound repair. The virus inactivation procedures are necessary and required to be verified for the clinical use and approval of biological products. Cobalt-60 (Co-60) or electron-beam (e-beam) is the common procedure for virus and bacterial reduction, but the excessive dose of irradiation was reported to be harmful to biological products. Herein, we present a riboflavin (RB)-ultraviolet light (UV) method for virus inactivation of amnion and chorion tissues. We used the standard in vitro limiting dilution assay to test the viral reduction capacity of the RB-UV method on amnion or chorion tissues loaded with four types of model viruses. We found RB-UV was a very effective procedure for inactivating viruses of amnion and chorion tissues, which could be used as a complementary method to Co-60 irradiation. In addition, we also screened the washing solutions and drying methods for the retention of growth factors.

Reporting of Financial Conflicts of Interest in Studies of Placental Membrane Allografts

Objective: To systematically review the accuracy of self-reported financial conflicts of interest (COI) by authors of placental membrane allograft product studies. Approach: A PubMed search identified placental membrane allograft studies published between 2015 and 2019. Industry payments were collected using the Centers for Medicare & Medicaid Services Open Payments database. Self-declared COI were compared with recorded payments. Risk factors for positive product recommendation were determined at study and author levels. Results: Eighty-nine studies (417 authors) were identified. Seventy-five studies (84%) had at least one author receive undisclosed payments. From 2015 to 2019, 5,841 general payments (totaling $15,558,026) and 1,234 research payments (totaling $18,290,062) were made by 46 companies. Travel/lodging was the most commonly reported transaction (34%). Authors were comprised mostly of podiatrists (27%), plastic surgeons (15%), and orthopedic surgeons (15%). Comparative studies were less likely to have a positive product recommendation compared to noncomparative studies (odds ratio [OR] 0.204, 95% confidence interval 0.06-0.066, p = 0.02). Multivariate analysis showed no association between COI discrepancy and product recommendation. Innovation: The accuracy of self-reported financial COI in placental membrane studies is evaluated for the first time. Conclusion: The majority of placental membrane product studies did not declare all industry payments. Whether these payments represent "relevant COI" remains unclear. In addition, not all placental product companies report to the Open Payments database, suggesting that the issue may be even more significant. This study highlights the need for improved definitions of "relevant COI," a standardized reporting system across journals, and the uniform participation of all medical product vendors.

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.

Allogenic Amniotic Tissue for Treatment of Knee and Hip Osteoarthritis

Osteoarthritis (OA) impacts millions of people and places a high burden on healthcare systems in the United States. Current treatment modalities have limitations and do not address underlying pathology. Lately, there has been an immense growth in the use of biologics, including perinatal allogenic tissues for orthopedic regenerative medicine applications. Amniotic tissue is an exciting new alternative for such applications. Despite several published studies that reported its use for treatment of ophthalmic conditions and complex wounds, there are limited clinical studies evaluating its safety and efficacy in treating patients suffering with knee or hip OA. In this manuscript, I focused on three prospective clinical studies which evaluated the safety and efficacy of amniotic tissue in patients suffering with moderate knee or hip OA. The results from these studies presented the scientific community with much needed, well-executed, and prospective clinical trials. Though these trials demonstrated that administration of amniotic tissue in knee or hip joint is safe and potentially effective, more multi-center, prospective, double-blinded, randomized controlled trials are warranted to further establish the efficacy of amniotic tissue to mitigate symptoms of knee and hip OA to ultimately justify its clinical use.

Rational Design of Immunomodulatory Hydrogels for Chronic Wound Healing

With all the advances in tissue engineering for construction of fully functional skin tissue, complete regeneration of chronic wounds is still challenging. Since immune reaction to the tissue damage is critical in regulating both the quality and duration of chronic wound healing cascade, strategies to modulate the immune system are of importance. Generally, in response to an injury, macrophages switch from pro-inflammatory to an anti-inflammatory phenotype. Therefore, controlling macrophages' polarization has become an appealing approach in regenerative medicine. Recently, hydrogels-based constructs, incorporated with various cellular and molecular signals, have been developed and utilized to adjust immune cell functions in various stages of wound healing. Here, the current state of knowledge on immune cell functions during skin tissue regeneration is first discussed. Recent advanced technologies used to design immunomodulatory hydrogels for controlling macrophages' polarization are then summarized. Rational design of hydrogels for providing controlled immune stimulation via hydrogel chemistry and surface modification, as well as incorporation of cell and molecules, are also dicussed. In addition, the effects of hydrogels' properties on immunogenic features and the wound healing process are summarized. Finally, future directions and upcoming research strategies to control immune responses during chronic wound healing are highlighted.

Chondrogenic Potential of Dental-Derived Mesenchymal Stromal Cells

The field of tissue engineering has revolutionized the world in organ and tissue regeneration. With the robust research among regenerative medicine experts and researchers, the plausibility of regenerating cartilage has come into the limelight. For cartilage tissue engineering, orthopedic surgeons and orthobiologists use the mesenchymal stromal cells (MSCs) of various origins along with the cytokines, growth factors, and scaffolds. The least utilized MSCs are of dental origin, which are the richest sources of stromal and progenitor cells. There is a paradigm shift towards the utilization of dental source MSCs in chondrogenesis and cartilage regeneration. Dental-derived MSCs possess similar phenotypes and genotypes like other sources of MSCs along with specific markers such as dentin matrix acidic phosphoprotein (DMP) -1, dentin sialophosphoprotein (DSPP), alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP), and STRO-1. Concerning chondrogenicity, there is literature with marginal use of dental-derived MSCs. Various studies provide evidence for in-vitro and in-vivo chondrogenesis by dental-derived MSCs. With such evidence, clinical trials must be taken up to support or refute the evidence for regenerating cartilage tissues by dental-derived MSCs. This article highlights the significance of dental-derived MSCs for cartilage tissue regeneration.

Intra-Articular Injection of Amniotic Membrane and Umbilical Cord Particulate for the Management of Moderate to Severe Knee Osteoarthritis

Objective

To evaluate the long-term benefit of a single injection of amniotic membrane/umbilical cord (AM/UC) particulate in patients with moderate to severe knee osteoarthritis (OA).

Methods

A single-center, investigator-initiated, retrospective study of patients who received intra-articular injection of 100 mg lyophilized and micronized AM/UC for radiographically confirmed, Kellgren–Lawrence (KL) grade 3 or 4 symptomatic knee OA. Data regarding demographics, OA severity, comorbidities, treatment regimens, complications, and patient-reported outcomes were collected and assessed. Patient Global Impression of Change (PGIC) was assessed on a 7-point scale, and Global Perceived Improvement (GPI), expressed as percent improvement relative to baseline, was used to further quantify the degree of symptomatic change. Clinically important response to treatment was assessed at 12 months using simplified OMERACT–OARSI responder criteria.

Results

A total of 42 patients with KL grade 3 (36%) and 4 (64%) knee OA were included for analysis. Prior to injection, patient-rated pain was 6.6 ± 1.5 out of 10 (median: 7, range: 3–10) despite prior treatment with oral/topical NSAIDs (62%) and intra-articular injection(s) of corticosteroids (57%) and/or hyaluronic acid (48%). Twelve months following AM/UC injection, 31 patients (74%) reported significant clinical improvement via PGIC, and the OMERACT–OARSI treatment response rate was 81% (34/42). GPI of pain and function was 62 ± 24%, 69 ± 27%, 69 ± 27%, and 64 ± 31% at 1, 3, 6, and 12 months, respectively. Symptomatic improvement was maintained for an average duration of 12.1 ± 4.5 months (median: 12, range: 3–22). One patient developed swelling in the knee within 36 hours of injection. No other adverse events or complications were reported.

Conclusion

Intra-articular injection of AM/UC particulate may be effective in alleviating pain and improving function in patients with moderate to severe knee OA, with the potential to delay total knee replacement for up to 12 months.