Effects of aging on basement membrane-related gene expression of the skeletal muscle in rats

In vitro modelling of intramuscular injection site events

INTRODUCTION

Intramuscular (IM) injections deliver a plethora of drugs. The majority of IM-related literature details dissolution and/or pharmacokinetic (PK) studies, using methods with limited assessments of post-injection events that can impact drug fate, and absorption parameters. Food and Drug Association guidelines no longer require preclinical in vivo modeling in the U.S.A. Preclinical animal models fail to correlate with clinical outcomes, highlighting the need to study, and understand, IM drug fate in vitro using bespoke models emulating human IM sites. Post-IM injection events, i.e. underlying processes that influence PK outcomes, remain unacknowledged, complicating the application of in vitro methods in preclinical drug development. Understanding such events could guide approaches to predict and modulate IM drug fate in humans.

AREAS COVERED

This article reviews challenges in biorelevant IM site modeling (i.e. modeling drug fate outcomes), the value of technologies available for developing IM injectables, methods for studying drug fate, and technologies for training in performing IM administrations. PubMed, Web-of-Science, and Lens databases provided papers published between 2014 and 2024.

EXPERT OPINION

IM drug research is expanding what injectable therapeutics can achieve. However, post-injection events that influence PK outcomes remain poorly understood. Until addressed, advances in IM drug development will not realize their full potential.

Effects of Aging on Collagen in the Skeletal Muscle of Mice

Aging affects several tissues in the body, including skeletal muscle. Multiple types of collagens are localized in the skeletal muscle and contribute to the maintenance of normal muscle structure and function. Since the effects of aging on muscle fibers vary by muscle fiber type, it is expected that the effects of aging on intramuscular collagen might be influenced by muscle fiber type. In this study, we examined the effect of aging on collagen levels in the soleus (slow-twitch muscle) and gastrocnemius (fast-twitch muscle) muscles of 3-, 10-, 24-, and 28-month-old male C57BL/6J mice using molecular and morphological analysis. It was found that aging increased collagen I, III, and VI gene expression and immunoreactivity in both slow- and fast-twitch muscles and collagen IV expression in slow-twitch muscles. However, collagen IV gene expression and immunoreactivity in fast-twitch muscle were unaffected by aging. In contrast, the expression of the collagen synthesis marker heat shock protein 47 in both slow- and fast-twitch muscles decreased with aging, while the expression of collagen degradation markers increased with aging. Overall, these results suggest that collagen gene expression and immunoreactivity are influenced by muscle fiber type and collagen type and that the balance between collagen synthesis and degradation tends to tilt toward degradation with aging.

Effects of Obesity in Old Age on the Basement Membrane of Skeletal Muscle in Mice

Obesity and aging are known to affect the skeletal muscles. Obesity in old age may result in a poor basement membrane (BM) construction response, which serves to protect the skeletal muscle, thus making the skeletal muscle more vulnerable. In this study, older and young male C57BL/6J mice were divided into two groups, each fed a high-fat or regular diet for eight weeks. A high-fat diet decreased the relative gastrocnemius muscle weight in both age groups, and obesity and aging individually result in a decline in muscle function. Immunoreactivity of collagen IV, the main component of BM, BM width, and BM-synthetic factor expression in young mice on a high-fat diet were higher than that in young mice on a regular diet, whereas such changes were minimal in obese older mice. Furthermore, the number of central nuclei fibers in obese older mice was higher than in old mice fed a regular diet and young mice fed a high-fat diet. These results suggest that obesity at a young age promotes skeletal muscle BM formation in response to weight gain. In contrast, this response is less pronounced in old age, suggesting that obesity in old age may lead to muscle fragility.

Chicken Hypothalamic and Ovarian DNA Methylome Alteration in Response to Forced Molting

Epigenetic modifications play an important role in regulating animal adaptation to external stress. To explore how DNA methylation regulates the expression levels of related genes during forced molting (FM) of laying hens, the hypothalamus and ovary tissues were analyzed at five periods using Whole-Genome Bisulfite Sequencing. The results show that methylation levels fluctuated differently in the exon, intron, 5′UTR, 3′UTR, promoter, and intergenic regions of the genome during FM. In addition, 16 differentially methylated genes (DMGs) regulating cell aging, immunity, and development were identified in the two reversible processes of starvation and redevelopment during FM. Comparing DMGs with differentially expressed genes (DEGs) obtained in the same periods, five hypermethylated DMGs (DSTYK, NKTR, SMOC1, SCAMP3, and ATOH8) that inhibited the expression of DEGs were found. Therefore, DMGs epigenetically modify the DEGs during the FM process of chickens, leading to the rapid closure and restart of their reproductive function and a re-increase in the egg-laying rate. Therefore, this study further confirmed that epigenetic modifications could regulate gene expression during FM and provides theoretical support for the subsequent optimization of FM technology.

Age-Related Changes in Extracellular Matrix

Extracellular matrix (ECM) is an extracellular tissue structure that, in addition to mechanical support to the cell, is involved in regulation of many cellular processes, including chemical transport, growth, migration, differentiation, and cell senescence. Age-related changes in the structure and composition of the matrix and increase of ECM stiffness with age affect functioning of many tissues and contribute to the development of various pathological conditions. This review considers age-related changes of ECM in various tissues and organs, in particular, effect of ECM changes on aging is discussed.

Identifying Common Genes and Pathways Associated with Periodontitis and Aging by Bioinformatics Analysis

BACKGROUND

This work used bioinformatic analysis to identify the relationship between periodontitis (PD) and aging, which could lead to new treatments for periodontal disease in the elderly.

METHOD

Four microarray datasets were obtained from the Gene Expression Omnibus (GEO) database and analyzed in R language to identify differentially expressed genes (DEGs). The common DEGs of PD and aging were evaluated as key genes in this investigation by a Venn diagram. These common DEGs were analyzed through additional experiments and analysis, such as pathway analysis and enrichment analysis, and a network of protein-protein interactions (PPIs) was constructed. Cytoscape was used to visualize hub genes and critical modules based on the PPI network. Interaction of TF-genes and miRNAs with hub genes is identified.

RESULT

84 common DEGs were found between PD and aging. Cytohubba was performed on the PPI network obtained from STRING tool, and the top 10 genes (MMP2, PDGFRB, CTGF, CD34, CXCL12, VIM, IL2RG, ACTA2, COL4A2, and TAGLN) were selected as hub genes. VIM may be a potential biomarker in the analysis of linked hub gene regulatory networks, and hsa-mir-21 and hsa-mir-125b are predicted to be associated in PD and aging.

CONCLUSION

This study investigated the key genes and pathways interactions between PD and aging, which may help reveal the correlation between PD and aging. The current research results are obtained by prediction, and follow-up biological experiments are required for further verification.

Downregulation of Sparc-like protein 1 during cisplatin-induced inhibition of myogenic differentiation of C2C12 myoblasts

Patients with cancer often experience muscle atrophy, which worsens their prognosis. Decreased muscle regenerative capacity plays an important role in the complex processes involved in muscle atrophy. Administration of cisplatin, a cancer chemotherapeutic agent, has been implicated as a cause of muscle atrophy. In this study, we examined whether cisplatin affects the differentiation of myoblasts into myotubes. We treated C2C12 myoblasts with a differentiation medium containing cisplatin and its vehicle during for 8 days and observed the changes in the expression of myosin heavy chain (MyHC) and myogenin in the myoblasts. Cisplatin was injected in mice for 4 consecutive days; on Day 5, the mice quadriceps muscles were sampled and examined. The expression of MyHCs increased and that of myogenin decreased after cisplatin treatment. The secretion of acidic cysteine-rich proteins (e.g., Sparc proteins) reportedly promotes C2C12 myoblast differentiation. Therefore, we investigated the Sparc family gene expression during myogenesis in C2C12 myoblasts after cisplatin treatment. Of all the genes investigated, Sparc-like protein 1 (Sparcl1) expression was significantly suppressed by cisplatin on Days 4-8. Simultaneous treatment with recombinant mouse Sparcl1 almost inhibited the cisplatin-induced suppression of total MyHC and myogenin protein levels. Moreover, Sparcl1 expression decreased in the skeletal muscles of mice, leading to cisplatin-induced muscle atrophy. Our results suggest that cisplatin-induced myogenesis suppression causes muscle atrophy and inhibits the expression of Sparcl1, which promotes C2C12 cell differentiation during myogenesis.

Effects of Endurance Exercise on Basement Membrane in the Soleus Muscle of Aged Rats

The basement membrane (BM)-related factors, including collagen IV, are important for the maintenance and recovery of skeletal muscles. Aging impairs the expression of BM-related factors during recovery after disuse atrophy. Muscle activity facilitates collagen synthesis that constitutes the BM. However, the effect of endurance exercise on the BM of aged muscles is unclear. Thus, to understand the effect of endurance exercise on the BM of the skeletal muscle in aged rats, we prescribed treadmill running in aged rats and compared the differences in the expression of BM-related factors between the aged rats with and without exercise habits. Aged rats were subjected to endurance exercise via treadmill running. Exercise increased the mRNA expression levels of the BM-related factors, the area and intensity of collagen IV-immunoreactivity and the width of lamina densa in the soleus muscle of aged rats. These finding suggests that endurance exercise promotes BM construction in aged rats.