Comparison of Collagen and Human Amniotic Membrane Nerve Wraps and Conduits for Peripheral Nerve Repair in Preclinical Models: A Systematic Review of the Literature

Introduction Collagen and human amniotic membrane (hAM) are Food and Drug Administration (FDA)-approved biomaterials that can be used as nerve wraps or conduits for repair of peripheral nerve injuries. Both biomaterials have been shown to reduce scarring and fibrosis of injured peripheral nerves. However, comparative advantages and disadvantages have not been definitively shown in the literature. The purpose of this systematic review is to comprehensively evaluate the literature regarding the roles of hAM and collagen nerve wraps and conduits on peripheral nerve regeneration in preclinical models. Methods The MEDLINE database was queried using the PubMed search engine on July 7, 2019, with the following search strategy: (“amniotic membrane” OR “amnion”) OR (“collagen conduit” OR “nerve wrap”)] AND “nerve.” All resulting articles were screened by two independent reviewers. Nerve type, lesion type/injury model, repair type, treatment, and outcomes were assessed. Results Two hundred and fifty-eight articles were identified, and 44 studies remained after application of inclusion and exclusion criteria. Seventeen studies utilized hAM, whereas 27 studies utilized collagen wraps or conduits. Twenty-three (85%) of the collagen studies utilized conduits, and four (15%) utilized wraps. Six (35%) of the hAM studies utilized conduits and 11 (65%) utilized wraps. Two (9%) collagen studies involving a conduit and one (25%) involving a wrap demonstrated at least one significant improvement in outcomes compared with a control. While none of the hAM conduit studies showed significant improvements, eight (73%) of the studies investigating hAM wraps showed at least one significant improvement in outcomes. Conclusion The majority of studies reported positive outcomes, indicating that collagen and hAM nerve wraps and conduits both have the potential to enhance peripheral nerve regeneration. However, relatively few studies reported significant findings, except for studies evaluating hAM wraps. Preclinical models may help guide clinical practice regarding applications of these biomaterials in peripheral nerve repair.

Differential Response of Human Amniotic Membrane Proteins in Hepatocellular Carcinoma: Analysis of the Glycolytic Metabolism

Background: The human Amniotic Membrane (hAM) has been studied as a potential therapeutic option in cancer, namely in hepatocellular carcinoma. Previously, our research group evaluated the effect of human Amniotic Membrane Protein Extracts (hAMPE) in cancer therapy, demonstrating that hAMPE inhibit the metabolic activity of human hepatocellular carcinoma cell lines: Hep3B2.1-7, HepG2 and Huh7. Therefore, the aim of this study was to evaluate the effect of hAMPE treatment in glucose metabolism of hepatocellular carcinoma. Methods and Results: Glucose uptake and lactate production was assessed by 1H-NMR, and the expression of several mediators of the glycolytic pathway was evaluated by Western blot or fluorescence. Our results showed that hAMPE treatment increased glucose consumption on Hep3B2.1-7, HepG2, and Huh7 through the increase of GLUT1 in Hep3B2.1-7 and Huh7, and GLUT3 in HepG2 cells. It was observed increased expression of 6-phosphofrutokinase (PFK-1L) in all cell lines, indicating that glucose can be converted to pyruvate. Also, it was verified that glucose seems not to be converted to lactate on HepG2 and Huh7 cells, suggesting that hAMPE treatment may contradict the Warburg effect observed in carcinogenesis. In Hep3B2.1-7, the hAMPE treatment induced an increase in expression of lactate dehydrogenase (LDH) and monocarboxylate transporter isoform 4 (MCT4). Conclusions: Overall, this work highlighted the potential usefulness of hAMPE as anticancer therapy through the modulation of the glycolytic metabolism in human hepatocellular carcinoma.

Update on surgical management of complex macular holes: a review

Modern surgical interventions effectively treat macular holes (MHs) more than 90%. Current surgical treatment for MHs is pars plana vitrectomy with epiretinal membrane, internal limiting membrane (ILM) peeling, gas endotamponade, and prone posturing postoperatively. However, a small subset of MHs imposes challenges to surgeons and frustrations on patients. A narrative review was performed on the surgical treatment of challenging MHs including large and extra-large MHs, myopic MHs with or without retinal detachment, and chronic and refractory MHs. There are robust data supporting inverted ILM flap as the first-line treatment for large idiopathic MHs and certain secondary MHs including myopic MHs. In addition, several studies had shown that ILM flap manipulations in combination with surgical adjuncts increase surgical success, especially in difficult MHs. Even in eyes with limited ILM, surgical options included autologous retinal graft, human amniotic membrane, and creation of a distal ILM flap that can assist in MH closure even though the functional outcome may be affected by the MH chronicity. Despite relative success anatomically and visually after each technique, most techniques require a long-term study to analyze their safety profile and to establish any morphological changes of the MH plug in the closed MHs.

The angiogenic properties of human amniotic membrane stem cells are enhanced in gestational diabetes and associate with fetal adiposity

Background An environment of gestational diabetes mellitus (GDM) can modify the phenotype of stem cell populations differentially according to their placental localization, which can be useful to study the consequences for the fetus. We sought to explore the effect of intrauterine GDM exposure on the angiogenic properties of human amniotic membrane stem cells (hAMSCs). Methods We comprehensively characterized the angiogenic phenotype of hAMSCs isolated from 14 patients with GDM and 14 controls with normal glucose tolerance (NGT). Maternal and fetal parameters were also recorded. Hyperglycemia, hyperinsulinemia and palmitic acid were used to in vitro mimic a GDM-like pathology. Pharmacological and genetic inhibition of protein function was used to investigate the molecular pathways underlying the angiogenic properties of hAMSCs isolated from women with GDM. Results Capillary tube formation assays revealed that GDM-hAMSCs produced a significantly higher number of nodes (P = 0.004), junctions (P = 0.002) and meshes (P < 0.001) than equivalent NGT-hAMSCs, concomitant with an increase in the gene/protein expression of FGFR2, TGFBR1, SERPINE1 and VEGFA. These latter changes were recapitulated in NGT-hAMSCs exposed to GDM-like conditions. Inhibition of the protein product of SERPINE1 (plasminogen activator inhibitor 1, PAI-1) suppressed the angiogenic properties of GDM-hAMSCs. Correlation analyses revealed that cord blood insulin levels in offspring strongly correlated with the number of nodes (r = 0.860; P = 0.001), junctions (r = 0.853; P = 0.002) and meshes (r = 0.816; P = 0.004) in tube formation assays. Finally, FGFR2 levels correlated positively with placental weight (r = 0.586; P = 0.028) and neonatal adiposity (r = 0.496; P = 0.014). Conclusions GDM exposure contributes to the angiogenic abilities of hAMSCs, which are further related to increased cord blood insulin and fetal adiposity. PAI-1 emerges as a potential key player of GDM-induced angiogenesis.

Could human amniotic membrane be a source for acupoint thread embedding therapy?

Background: Peripheral neuropathy usually leads to a major cause of motor disability, but the functional restoration after treatment continues to show modest results. Acupoint thread-embedding therapy is a subtype of acupuncture treatment in which biodegradable threads are inserted into skin, subcutaneous tissue or muscles at specific points for long stimulation. Different biodegradable materials have been developed and widely used. Human amniotic membrane is rich in collagen, extracellular matrix proteins and growth factors. The avascular, low immunogenic, anti-inflammatory, antibacterial, anti-fibrotic and non-tumorigenic properties of amniotic membrane make it valuable in medical applications and its use has no ethical problems. Elasticity, stiffness and other biomechanical properties also make it possible to use the amniotic membrane for various medical purposes. AM is almost always considered as discarded substance, it satisfies most of the criteria of an ideal biological tissue and shows almost zero rejection phenomenon. Conclusions: The human amniotic membrane, the cellular compounds and extracellular matrix have a lot of benefic proprieties that are or could be used in treatment of many human diseases. Its biological and biomechanical properties are promising in the manufacture and use of filaments in acupoint thread embedding therapy.

The clinical effectiveness of cryopreserved human amniotic membrane in diabetic foot syndrome

Diabetic foot syndrome with long-term unhealed wounds is the most common complication and cause of limb amputation in diabetes. The search for effective therapeutic agents and their inclusion in treatment protocols is a priority due to the increase in the number of cases of this socially significant disease and disability among the working population every year. The aim of the study is to evaluate the effectiveness of cryopreserved human amniotic membrane in the treatment of long-term non-healing wounds of the lower extremities in diabetic foot syndrome. Materials and methods. The pilot clinical study described 4 clinical cases of treatment of patients with diabetes mellitus type I and II (1 woman and 3 men aged 52 to 68 years) with long-term unhealed wounds of the limbs under standard therapy. After previous wound sanation the applications of the cryopreserved human amniotic membrane were performed. Once a week after the application, the dynamics of wound healing was assessed. Blood glucose levels were determined before amniotic membrane treatment and two hours after the procedure. Results. As a results of weekly applications of human amniotic membrane there was a gradual decrease in the area of the wound from the original size and increase the rate of healing. Thus, at the time of the second visit (after 7 days) the reduction in the area of the ulcer from the initial size in patient 1 was 33 %, patient 2 – 25 %, patient 3 – 33 % on the sole and patient 4 – 3 %, and the healing rate – 4.7 %, 3.6 %, 4.7 % and 0.43 % per day, respectively. The use of human amniotic membrane did not affect blood glucose levels when comparing values before application and two hours after the procedure. Regular follow-up visits of patients 3, 6, 9 and 12 months after the start of the study showed no recurrence of ulcers. Conclusions. It has been shown that the use of cryopreserved human amniotic membrane in patients with diabetes mellitus and diabetic foot syndrome with long-term unhealed wounds results in complete healing of ulcers with stable remission during the year of observation.