Ghrelin prevents tumour- and cisplatin-induced muscle wasting: characterization of multiple mechanisms involved

BACKGROUND

Cachexia and muscle atrophy are common consequences of cancer and chemotherapy administration. The novel hormone ghrelin has been proposed as a treatment for this condition. Increases in food intake and direct effects on muscle proteolysis and protein synthesis are likely to mediate these effects, but the pathways leading to these events are not well understood.

METHODS

We characterized molecular pathways involved in muscle atrophy induced by Lewis lung carcinoma (LLC) tumour implantation in c57/bl6 adult male mice and by administration of the chemotherapeutic agent cisplatin in mice and in C2C12 myotubes. The effects of exogenous ghrelin administration and its mechanisms of action were examined in these settings.

RESULTS

Tumour implantation and cisplatin induced muscle atrophy by activating pro-inflammatory cytokines, p38-C/EBP-β, and myostatin, and by down-regulating Akt, myoD, and myogenin, leading to activation of ubiquitin-proteasome-mediated proteolysis and muscle weakness. Tumour implantation also increased mortality. In vitro, cisplatin up-regulated myostatin and atrogin-1 by activating C/EBP-β and FoxO1/3. Ghrelin prevented these changes in vivo and in vitro, significantly increasing muscle mass (P < 0.05 for LLC and P < 0.01 for cisplatin models) and grip strength (P = 0.038 for LLC and P = 0.001 for cisplatin models) and improving survival (P = 0.021 for LLC model).

CONCLUSION

Ghrelin prevents muscle atrophy by down-regulating inflammation, p38/C/EBP-β/myostatin, and activating Akt, myogenin, and myoD. These changes appear, at least in part, to target muscle cells directly. Ghrelin administration in this setting is associated with improved muscle strength and survival.

Prevention of cardiac hypertrophy by atorvastatin in a transgenic rabbit model of human hypertrophic cardiomyopathy

Cardiac hypertrophy, a major determinant of morbidity and mortality in hypertrophic cardiomyopathy (HCM), is considered a secondary phenotype and potentially preventable. To test this hypothesis, we screened 30 5- to 6-month-old beta-myosin heavy chain Q403 transgenic rabbits by echocardiography and selected 26 without cardiac hypertrophy. We randomized the transgenic rabbits to treatment with atorvastatin (2.5 mg/Kg/d), known to block hypertrophic signaling or a placebo. We included 15 nontransgenic rabbits as controls. Cardiac phenotype was analyzed serially before, 6 and 12 months after randomization. Serum total cholesterol levels were reduced by 49% with atorvastatin administration. Left-ventricular mass, wall thickness; myocyte size, myocardial levels of molecular markers of hypertrophy, lipid peroxides, and oxidized mitochondrial DNA; and the number of terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive myocytes were increased significantly in the placebo but not in the atorvastatin group. Myocardium catalase mRNA levels were decreased by 5-fold in the placebo but were normal in the atorvastatin group. Catalase protein level and activity were not significantly changed. Levels of membrane-bound Ras and phospho-p44/42 mitogen-activated-protein kinase (MAPK) were increased in the placebo group (approximately 2.5 fold) but were reduced in the atorvastatin group. Levels of GTP- and membrane-bound RhoA and Rac1, phospho-p38, and phospho-c-Jun NH2-terminal kinases were unchanged. Thus, atorvastatin prevented development of cardiac hypertrophy; determined at organ, cellular, and molecular levels, partly through reducing active Ras and p44/42 MAPK. The results indicate potential beneficial effects of atorvastatin in prevention of cardiac hypertrophy, a major determinant of morbidity in all forms of cardiovascular diseases, and beckon clinical studies in humans with HCM.

Identification of coexpressed gene clusters in a comparative analysis of transcriptome and proteome in mouse tissues

A major advantage of the mouse model lies in the increasing information on its genome, transcriptome, and proteome, as well as in the availability of a fast growing number of targeted and induced mutant alleles. However, data from comparative transcriptome and proteome analyses in this model organism are very limited. We use DNA chip-based RNA expression profiling and 2D gel electrophoresis, combined with peptide mass fingerprinting of liver and kidney, to explore the feasibility of such comprehensive gene expression analyses. Although protein analyses mostly identify known metabolic enzymes and structural proteins, transcriptome analyses reveal the differential expression of functionally diverse and not yet described genes. The comparative analysis suggests correlation between transcriptional and translational expression for the majority of genes. Significant exceptions from this correlation confirm the complementarities of both approaches. Based on RNA expression data from the 200 most differentially expressed genes, we identify chromosomal colocalization of known, as well as not yet described, gene clusters. The determination of 29 such clusters may suggest that coexpression of colocalizing genes is probably rather common.

New ligands binding to the human leukocyte antigen class II molecule DRB1*0101 based on the activity pattern of an undecapeptide library

Major histocompatibility complex (MHC) class II molecules present peptide antigens to CD(4+)-T cells. These heterogeneous peptides are derived from internalized exogenous proteins or from endogenous membrane proteins that are processed by the antigen-presenting cell. Peptides are bound to the MHC class II molecules in an extended conformation and extend out of the binding groove. The aim of this study was to estimate the influence of every amino acid in all the possible undecapeptide amides (2.048 x 10(14) individuals) on the binding to human MHC-DRB1*0101 molecules (HLA-DR1) and to identify new peptide ligands. 220 undecapeptide sublibraries, O/X10, each composed of ten degenerate positions and one defined position, were screened for binding to isolated HLA-DR1. Competition of the sublibraries with a fluorescence-labeled peptide ligand allowed definition of the amino acids favourable or unfavourable for DR1-binding at every sequence position. From the activity pattern of the undecapeptide library, 54 individual peptides were deduced (27 potential hits and 27 potential falls) and prepared by chemical synthesis. As anticipated, 27 positive and 27 negative results were obtained from the competition experiments. The 27 peptides that bind obey the rules for the HLA-DR1-binding motif. The synthetic peptide library approach proved to be valuable for the design of synthetic MHC class II ligands and thus can be considered as a basis for drug design in immunotherapy.

Tumour-specific MHC-class-II-restricted responses after in vitro sensitization to synthetic peptides corresponding to gp100 and Annexin II eluted from melanoma cells

In a search for potentially tumour-specific MHC-class-II-restricted antigens, the immunogenicity of endogenous peptides that had been eluted from HLA-DR molecules of the human melanoma cell line FM3 (HLA-DRB1*02x, DRB1*0401) was tested in vitro. Two 16-mers representing gp100 positions 44-59, and annexin II positions 208-223 bound well to isolated DRB1*0401 molecules and are discussed here. HLA-DR-matched normal donors' T cells were cultured with peptide-pulsed artificial antigen-presenting cells (CHO cells cotransfected with genes for HLA-DRB1*0401 and CD80 and coexpressing high levels of both human molecules). Specific sensitization was achieved against both peptides, as measured in assays of autocrine proliferation and interleukin-2 secretion. Moreover, responses to native autologous melanoma cells but not to autologous B cells were also observed. In view of the expression of fas by the activated T cells and of fas ligand by the melanoma cells, blockade of potential fas/ fas-ligand interactions was undertaken using monoclonal antibodies (mAb). The antagonistic fas-specific mAb M3, but not the fas agonist M33, caused a markedly enhanced T cell response to FM3 cells. These results demonstrate that synthetic peptide antigens are able to sensitize T cells in vitro for effective MHC-class-II-restricted recognition of melanoma cells.

Glutamic acid decarboxylase T lymphocyte responses associated with susceptibility or resistance to type I diabetes: analysis in disease discordant human twins, non-obese diabetic mice and HLA-DQ transgenic mice

Glutamic acid decarboxylase (GAD65) has been implicated as a targeted self antigen in the immune destruction of pancreatic beta cells. T cell responses to GAD65 peptides have been detected in both patients with type I diabetes and in the non-obese diabetic (NOD) mouse. To establish which GAD65 epitopes are important in the immunopathogenesis of disease we initially compared T cell responses to GAD65 epitopes in conditions of disease susceptibility and protection. T cell responses to GAD65 peptides were measured in monozygotic twin pairs selected on the basis of disease discordance and T cell recognition of immunogenic regions of GAD65. Peptides of interest were then used to immunize susceptible NOD mice and H2-E transgenic NOD mice which are protected from diabetes. A differential response to the epitope GAD65 521-535 discriminated diabetic from non-diabetic human twins as well as susceptible from protected mice. This epitope as well as GAD 505-519 induces T cell responses despite binding the type I diabetes associated HLA-DQA1*0301/DQB1*0302 product with low affinity. Since DQ-restricted T cell responses are difficult to study in humans, HLA-DQ8 transgenic mice were then used: GAD epitopes 521-535 and 505-519 induced responses in DQ8 transgenic mice and T cell lines were established. Long-term T cell lines against GAD 505-519 were HLA-DQ restricted, and responded to peptide with a strong IFN-gamma and IL-10 response. The findings implicate GAD 521-535 as a possible target peptide in pathogenesis and are compatible with a model whereby self-reactive T cells specific for low-affinity peptide-MHC complexes may escape thymic negative selection.

Characterization of peptides bound to extracellular and intracellular HLA-DR1 molecules

Exogenous antigens are internalized by antigen-processing cells and processed within vesicular compartments to produce antigenic peptides that bind to newly synthesized MHC II molecules. These MHC class II peptide complexes are displayed at the plasma membrane and stimulate specific CD4+ T cells. In the present study, we established a method to isolate intracellular MHC molecules in a preparative scale (2-3 mg HLA-DR1) from endosomal compartments by Percoll density-gradient centrifugation. Peptides associated with HLA-DR1 in these intracellular fractions were released, purified by microbore HPLC, characterized by sequencing, and compared with the amino acid composition of peptides derived from MHC class II molecules obtained by solubilization of the plasma membrane. The binding affinity of these MHC fractions was analyzed by our highly sensitive binding assay using different DR1-restricted IM and Ii peptides. The results indicate that (a) intracellular MHC molecules show higher peptide-binding capacity, (b) peptides that are about 18-25 amino acids long need only a core region of 11 amino acids for binding, (c) specific positions of the peptides are important for DR1 binding, (d) most of the naturally processed peptides show a proline at position 2 or 3 that may represent a stop signal for trimming, and (e) Ii peptides are very abundant in DR1 peptide pools derived from intracellular compartments.

Deletion of ghrelin prevents aging-associated obesity and muscle dysfunction without affecting longevity

During aging, decreases in energy expenditure and locomotor activity lead to body weight and fat gain. Aging is also associated with decreases in muscle strength and endurance leading to functional decline. Here, we show that lifelong deletion of ghrelin prevents development of obesity associated with aging by modulating food intake and energy expenditure. Ghrelin deletion also attenuated the decrease in phosphorylated adenosine monophosphate‐activated protein kinase (pAMPK) and downstream mediators in muscle, and increased the number of type IIa (fatigue resistant, oxidative) muscle fibers, preventing the decline in muscle strength and endurance seen with aging. Longevity was not affected by ghrelin deletion. Treatment of old mice with pharmacologic doses of ghrelin increased food intake, body weight, and muscle strength in both ghrelin wild‐type and knockout mice. These findings highlight the relevance of ghrelin during aging and identify a novel AMPK‐dependent mechanism for ghrelin action in muscle.

A 16mer peptide of the human autoantigen calreticulin is a most prominent HLA-DR4Dw4-associated self-peptide

The human Ca(2+)-binding (storage) protein calreticulin, located in the lumen of the endoplasmic reticulum, is proposed to play a role as autoantigen: anticalreticulin autoantibodies occur in the sera of patients with SLE and patients with onchocerciasis (calreticulin shows a high sequence homology to the Onchocerca volvulus antigen RAL-1). Here we present sequencing data of a HLA-DR4Dw4-associated calreticulin peptide fragment, Cal(295-310), purified from a DR4Dw4 self-peptide pool. Cal(295-310) proved to be one of three commonest self-peptides associated with DR4Dw4 molecules that were isolated from the EBV-transformed B-cell line BSM (DR4Dw4, DRw53). We tested the binding of Cal(295-309) and the analogous RAL-1 peptide to HLA-DR molecules: Cal(295-309) exhibited specific binding characteristics for DR4Dw4. Binding assays using self-peptide analogues with replaced amino acids led us to a DR4Dw4-binding motif with anchor residues at relative positions 1 and 6. The sequencing data suggest that calreticulin is a frequently processed intracellular protein. The abundance of calreticulin makes the presentation of different calreticulin peptides associated with HLA-D molecules likely to occur, supporting the immunologic relevance of this molecule.

Identification of Dll1 (Delta1) target genes during mouse embryogenesis using differential expression profiling

The Notch signaling pathway has pleiotropic functions during mammalian embryogenesis. It is required for the patterning and differentiation of the presomitic and somitic paraxial mesoderm and of the neural tube. We used DNA-chip expression profiling and 2D-gel electrophoresis combined with peptide mass fingerprinting to identify genes and proteins differentially regulated in E10.5 Dll1 (delta-like 1, Delta1) mutant embryos. The differential expression profiling approach identified 47 regulated transcripts and 40 differentially expressed proteins. The majority of these genes has until now not been associated with Notch signaling. Subsequent whole-mount in situ hybridization confirmed that a subset of the identified transcripts has restricted and distinct patterns of expression in E10.5 mouse embryos. For most genes these expression patterns were affected in the presomitic mesoderm, in differentiating somites of Dll1 mutant embryos and in the neural tube and cells differentiating from it. Similar effects were observed in embryos homozygous for the Headturner (Htu) and pudgy (pu) mutations, which are alleles of the Notch ligands Jag1 and Dll3. The regulated expression of a subset of the proteins was validated by immunoblots. Remarkably six of the proteins down-regulated in Dll1 mutant embryos are proteasome subunits. The large set of regulated genes identified in this differential expression profiling approach is an important resource for further functional studies.

Human monoclonal antibody with T-cell-like specificity recognizes MHC class I self-peptide presented by HLA-DR1 on activated cells

Alloreactive T cells recognize peptides presented in the binding groove of major histocompatibility complex molecules (MHCs), whereas B cells mainly recognize the MHCs independent of bound peptides. Here, we demonstrate that the human B-cell repertoire comprises B cells which can be stimulated during pregnancy to produce antibodies reacting with MHCs in a way similar to T cells. The human monoclonal antibody UL-5A1 recognizes DR1(DRA/DRB1*0101) molecules on lymphoblastoid cell lines only if they co-express HLA-A2 or if they have been loaded with HLA-A2-derived peptides. The effect of the HLA-A2 peptide 105-117 on UL-5A1 reactivity was specific, time and dose-dependent. Reactivity increased when naturally processed peptides were removed from DR1 molecules before the HLA-A2 peptide 105-117 was loaded. UL-5A1 reacted specifically with cells that had been activated. The results imply a role of activation of cells in peptide processing and/or loading.

Restoration of lung surfactant protein D by IL-6 protects against secondary pneumonia following hemorrhagic shock

OBJECTIVES

To identify novel approaches to improve innate immunity in the lung following trauma complicated by hemorrhagic shock (T/HS) for prevention of nosocomial pneumonia.

METHODS

We developed a rat model of T/HS followed by Pseudomonas aeruginosa (PA) pneumonia to assess the effect of alveolar epithelial cell (AEC) apoptosis, and its prevention by IL-6, on lung surfactant protein (SP)-D protein levels, lung bacterial burden, and survival from PA pneumonia, as well as to determine whether AEC apoptosis is a consequence of the unfolded protein response (UPR). Lung UPR transcriptome analysis was performed on rats subjected to sham, T/HS, and T/HS plus IL-6 protocols. Group comparisons were performed via Kaplan-Meier or ANOVA.

RESULTS

T/HS decreased lung SP-D by 1.8-fold (p < 0.05), increased PA bacterial burden 9-fold (p < 0.05), and increased PA pneumonia mortality by 80% (p < 0.001). IL-6, when provided at resuscitation, normalized SP-D levels (p < 0.05), decreased PA bacterial burden by 4.8-fold (p < 0.05), and prevented all mortality from PA pneumonia (p < 0.001). The UPR transcriptome was significantly impacted by T/HS; IL-6 treatment normalized the T/HS-induced UPR transcriptome changes (p < 0.05).

CONCLUSIONS

Impaired innate lung defense occurs following T/HS and is mediated, in part, by reduction in SP-D protein levels, which, along with AEC apoptosis, may be mediated by the UPR, and prevented by use of IL-6 as a resuscitation adjuvant.

T cell reactivity to DR*0401- and DQ*0302-binding peptides of the putative autoantigen IA-2 in type 1 diabetes

Type 1 diabetes is thought to be an autoimmune disease mediated by T lymphocytes recognizing critical islet cell antigens. Recently, the tyrosine phosphatase like protein IA-2 was suggested as a putative autoantigen in type 1 diabetes since autoantibodies are detected in sera of diabetic patients and prediabetic subjects. Similarly, T cell responses of peripheral blood lymphocytes of type 1 diabetic patients to this protein have been described. Only very few data is available about immunodominant epitopes of IA-2 recognized by T cells. We have studied T cell responses in type 1 diabetic patients and age and partly HLA matched controls to IA-2 peptides designed to bind HLA risk alleles of IDDM as DR*0401 and DQ*0302. Both diabetic patients and controls responded to IA-2ic and some of the peptides. Three peptides of the C-terminal region of IA-2 were recognised by T cells of a fraction of diabetic patients but at least two of these peptides triggered also T cell responses in DR*0401/DQ*0302-matched controls. Most peptides bound to different HLA alleles ("promiscous binders"). The identification of autoantigenic epitopes may offer clues to related sequences e.g. of viral origin what relates to models of diabetes pathogenesis ("molecular mimicry"). Secondly, the design of antigen- or even epitope-specific immune intervention strategies aiming at tolerization of disease specific T cells in type 1 diabetes may profit from the knowledge of immunodominant T cell epitopes of a putative autoantigen.

Sexual dimorphism in upper gastrointestinal motility is dependent on duration of fast, time of day, age, and strain of mice

BACKGROUND

An important limitation of gastrointestinal motility testing is high variability. Conditions that could contribute to variability, including the duration of pretest fasting and time of day, are rarely reported and have not been examined systematically. This study aimed to explore whether these conditions, as well as age, sex, and strain of mice, affect the results of a standard laboratory test of upper gastrointestinal motility.

METHODS

Male and female 8-week-old C57BL/6J mice received a gastric gavage of fluorescein isothiocyanate (FITC)-conjugated dextran. FITC-dextran distribution was measured 30 minutes later. Mean geometric centers (MGCs) were calculated to determine the effects of short versus prolonged fasting and morning versus afternoon testing. The influence of age was assessed in 2- to 10-week-old animals, and the influence of strain was determined in C57BL/6J, BALB/c, and CD-1 mice.

KEY RESULTS

Motility was sexually dimorphic. MGC progressed 19% further in 8-week-old C57BL/6J males versus females when tested in the morning after a short fast. Similar patterns were observed in morning or afternoon testing after overnight fasting. In males, motility was unaffected by time of day; however, MGC progressed 31% further in females tested in the afternoon versus morning after a short fast. Sex differences also were present in CD-1 but not BALB/c mice. Testing in neonates revealed strikingly low variability and no sex differences.

CONCLUSIONS & INFERENCES

Fasting duration, time of day, age, sex, and strain of mice all influence upper gastrointestinal motility testing. Sex differences are not present in neonatal pups, but develop soon after weaning.

Early-life malnutrition causes gastrointestinal dysmotility that is sexually dimorphic

BACKGROUND

Slow gastrointestinal (GI) transit occurs in moderate-to-severe malnutrition. Mechanisms underlying malnutrition-associated dysmotility remain unknown, partially due to lack of animal models. This study sought to characterize GI dysmotility in mouse models of malnutrition.

METHODS

Neonatal mice were malnourished by timed maternal separation. Alternatively, low-protein, low-fat diet was administered to dams, with malnourished neonates tested at two weeks or weaned to the same chow and tested as young adults. We determined total GI transit time by carmine red gavage, colonic motility by rectal bead latency, and both gastric emptying and small bowel motility with fluorescein isothiocyanate-conjugated dextran. We assessed histology with light microscopy, ex vivo contractility and permeability with force-transduction and Ussing chamber studies, and gut microbiota composition by 16S rDNA sequencing.

KEY RESULTS

Both models of neonatal malnutrition and young adult malnourished males but not females exhibited moderate growth faltering, stunting, and grossly abnormal stomachs. Progression of fluorescent dye was impaired in both neonatal models of malnutrition, whereas gastric emptying was delayed only in maternally separated pups and malnourished young adult females. Malnourished young adult males but not females had atrophic GI mucosa, exaggerated intestinal contractile responses, and increased gut barrier permeability. These sex-specific abnormalities were associated with altered gut microbial communities.

CONCLUSIONS & INFERENCES

Multiple models of early-life malnutrition exhibit delayed upper GI transit. Malnutrition affects young adult males more profoundly than females. These models will facilitate future studies to identify mechanisms underlying malnutrition-induced pathophysiology and sex-specific regulatory effects.

Coagulopathy in Malnourished Mice Is Sexually Dimorphic and Regulated by Nutrient-Sensing Nuclear Receptors

Liver dysfunction, including coagulopathy, is a prominent feature of protein-energy malnutrition. To identify mechanisms underlying malnutrition-associated coagulopathy, we administered a low-protein low-fat diet to lactating dams and examined hepatic transcription and plasma coagulation parameters in young adult weanlings. Malnutrition impacted body composition to a greater extent in male versus female mice. Transcriptional profiles suggested opposing effects of nutrient-sensing nuclear receptors, namely induction of peroxisome proliferator-activated receptor α (PPARα) targets and repression of farnesoid-X-receptor (FXR) targets. Coagulopathy with decreased synthesis of fibrinogen-α (FGA) and factor 11 (F11) was observed in malnourished male animals but not female animals. In primary mouse hepatocytes, FXR agonist increased and PPARα agonist decreased Fga and F11 messenger RNA expression. Nuclear receptor DNA response elements were identified in the Fga and F11 gene regulatory regions, and opposing effects of FXR and PPARα were confirmed with luciferase assays. Unexpectedly, hepatic PPARα protein was markedly depleted in malnourished male liver and was not enriched on Fga or F11 response elements. Rather, there was loss of FXR binding at these response elements. Reduced PPARα protein was associated with loss of hepatocyte peroxisomes, which are necessary for bile acid biosynthesis, and with decreased concentrations of bile acids that function as FXR ligands, most notably the FXR agonist chenodeoxycholic acid. Conclusion: Malnutrition impairs growth and liver synthetic function more severely in male mice than in female mice. Malnourished male mice are coagulopathic and exhibit decreased hepatocyte peroxisomes, FXR agonist bile acids, FXR binding on Fga and F11 gene regulatory elements, and coagulation factor synthesis. These effects are absent in female mice, which have low baseline levels of PPARα, suggesting that nutrient-sensing nuclear receptors regulate coagulation factor synthesis in response to host nutritional status in a sex-specific manner.

Asiatic Acid Fabricated Nanoconstructs to Mitigate Amyloid Beta1-42 Induced Injury in SH-SY5Y Cells In-Vitro and Ameliorates Cognitive Impairment by Dual Cholinesterase Inhibition and Attenuation of Oxidative Stress In-Vivo

PURPOSE

Asiatic acid (AA) is reported for its neuroprotective potential in Alzheimer's disease (AD). This present work aimed to develop AA loaded nanostructured lipid carriers (AAN) for targeting the delivery of AA into the brain and ameliorating the cognitive deficits in AD rats.

METHODS

AAN was optimized using the Box-Behnken design, considering 3 factors (soya lecithin, tween 80, and high pressure homogenizer (HPH) pressure) as independent variables while particle size (PS), zeta potential (ZP) and entrapment efficiency (EE) were dependent variables. Cytotoxicity assay and internalization studies of AAN were evaluated in SH-SY5Y cells and further neuroprotective efficiency on intracellular amyloid beta (Aβ) aggregation was evaluated in Aβ _1-42 treated cells with thioflavin T (ThT). The behavioral acquisition effects were evaluated in Aβ _1-42 (5 µg/ 5 µL, intracerebroventricular (ICV), unilateral) induced AD model followed by the histology and quantification of neurotransmitters levels.

RESULTS

The optimized AAN revealed desired PS (44.1 ± 12.4 nm), ZP (- 47.1 ± 0.017 mv) and EE (73.41 ± 2.53%) for brain targeting delivery of AA. In-vitro, AAN exhibited better neuroprotective potential than AA suspension (AAS). AA content was 1.28 folds and 2.99 folds heightened in plasma and brain respectively after the i.p. administration of AAN as compared to AAS. The results of pharmacodynamic studies manifested the AAN treatment significantly (p < 0.05) ameliorated the cognitive deficits.

CONCLUSIONS

Hence, developed AAN has neuroprotective potential and should be further considered as an unconventional platform in preclinical model for the management of AD.

An Insight into Biodegradable Polymers and their Biomedical Applications for Wound Healing

Biodegradable polymers, encompassing both natural and synthetic polymers, have demonstrated efficacy as carriers for synthetic drugs, natural bioactive molecules, and inorganic metals. This is due to their ability to control the release of these substances. As a result, various advanced materials, such as nanoparticle- loaded hydrogels, nanofibrous scaffolds, and nanocomposites, have been developed. These materials have shown promise in enhancing processes, such as cell proliferation, vascular angiogenesis, hair growth, and wound healing management. Natural polymers, including hyaluronic acid, collagen, chitosan, gelatin, and alginate, as well as synthetic polymers like polylactic acid, polyglycolic acid, polylactic co-glycolic acid, and PCA, have significant potential for promoting wound healing. This study examines the advancements in biodegradable polymers for wound healing, specifically focusing on each polymer and its distinctive formulations. It also discusses the in vitro experiments conducted using different cell lines, as well as the in vivo studies that explore the numerous uses of these polymers in wound healing. The discussion also included the exploration of modifications or combinations of several polymers, as well as surface changes, in order to produce synergistic effects and address the limitations of individual polymers. The goal was to expedite the healing process of different chronic wounds. Due to this, there have been notable advancements in the technological use of polymeric mixes, including biodegradable polymer-based scaffolds, which have accelerated the process of wound healing.