All

All
Insight
Research Services
Preclinical CRO
Animal Resource Bank

Latest News

Focusing on cutting-edge technologies and research advancements,
sharing Aniphe BioLab’s achievements in scientific innovation, Professional insights
and practical experience in the fields of laboratory animals and preclinical research.

Publish an article

2026-10-29

Naming Genetically Engineered Mice (Part II): From Being Understandable to Being Written Correctly

2026-10-29

How should a multi-disease composite mouse model be constructed? Let’s take a look at the CKM approach.

2026-08-12

2026 CKM Guidelines Released: Chronic Diseases Enter the Era of Integrated Cardiorenal-Metabolic Management—It’s Time to Rethink Animal Models

2026-08-12

A Guide to Safe Mouse Handling | Manual on Mouse Transport Protocols and Troubleshooting

Literature Review | Progress in Rat Bone Repair! Umbilical Cord MSC–Derived Exosomes Promote Regeneration

Introduction

Currently, a major challenge facing orthopedic surgeons is how to repair large bone defects. The newly formed microvasculature within the graft is critical to the success of bone tissue engineering. Previously, exosomes derived from mesenchymal stem cells (MSCs) have been shown to play a beneficial role in vascular development and in the repair of various tissues. However, there are few reports on the application of MSC‑derived exosomes in the repair of large bone defects.

-------------------------------------

In 2021, Changhai Hospital, Naval Medical University The team is in ACS Applied Materials & Interfaces (IF= 9.229 ) An article titled “Umbilical Mesenchymal Stem Cell-Derived Exosome-Encapsulated Hydrogels Accelerate Bone Repair by Enhancing Angiogenesis” was published in the journal. The research findings indicate that: Exosomes derived from umbilical cord mesenchymal stem cells ( ^uMSC EXOs) When encapsulated in a hyaluronic acid hydrogel (HA gel) and combined with a custom-designed nano-hydroxyapatite/poly-ε-caprolactone (nHP) scaffold, it can Repair of cranial defects in rats 。

Literature Review

The experimental protocol is as follows:

Experimental Procedure

1. Preparation and Characterization of Composite Material Supports

Exosomes were isolated and purified from the supernatants of uMSCs (umbilical cord mesenchymal stem cells) or HEK293 cell lines using ultracentrifugation, and their morphology and characteristics were analyzed by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting.

Through ¹ The H NMR spectrum was used to characterize the hyaluronic acid hydrogel (HA gel). After 30 minutes of UV irradiation, the HA gel (HA‑Gel) can be molded into any shape. Following successful preparation of the HA‑Gel, its ability to retain exosomes was evaluated. ^uMSC The release profile of EXOs and the degradation curve of HA‑Gel exhibit similar trends. Furthermore, after 20 days of immersion in PBS, approximately 40% of the exosomes remained within the HA‑Gel.

Exosomes derived from umbilical cord mesenchymal stem cells ( ^uMSC EXOs were encapsulated within an HA gel and integrated with a custom-designed nano-hydroxyapatite/poly-ε-caprolactone (nHP) scaffold. Scanning electron microscopy revealed that the three-dimensional porous nHP scaffold exhibited a cylindrical morphology, with a diameter of 5 mm and a height of 1.5 mm, featuring a three-dimensional interconnected pore network whose pore size was approximately 300 μm. The pore structure of the Gel/nHP composite material was fully occupied by the cross-linked hydrogel.

Figure 1. Preparation and characterization of composite scaffolds

2. Exosomes derived from umbilical cord mesenchymal stem cells promote the repair of cranial defects in rats.

A rat cranial defect model was established, and three different scaffolds—Gel/nHP—were used, respectively. ^HEK²⁹³ EXOs/Gel/nHP, ^uMSC EXOs/Gel/nHP repair the defect site, and at 4 and 8 weeks, they are utilized. Micro-CT was used to assess the repair status at the defect site. 。

The results show ^uMSC The EXOs/Gel/nHP group exhibited more newly formed bone compared with the other three groups, and its BMD, BV/Tv, Tb.Th, and Tb.N were all significantly higher than those of the other three groups, whereas no significant differences were observed among the latter three groups. More importantly, in… ^uMSC Collagen ingrowth was observed and significantly increased in the EXOs/Gel/nHP group.

Figure 2. Micro-CT images and quantitative analysis of cranial defects in rats.

Masson Dyeing Display, use ^uMSC The scaffolds treated with EXOs/Gel/nHP composites exhibited abundant bone-like matrix and collagen, whereas the other groups showed only sparse collagen fibers.

H&E staining It shows that, compared with the other three groups, ^uMSC The EXOs/Gel/nHP group generated and grew a greater quantity of tissue within the nHP scaffold.

In addition, VEGFA, CD31, BMP-2, and OCN were assessed. Immunohistochemical staining ，^uMSC The positive cell area in the EXOs/Gel/nHP group was significantly greater than that in the other three control groups, with no significant differences observed among the control groups.

Figure 3. Histological and immunohistochemical analysis of the implantation site at 8 weeks postoperatively.

These imaging and histological findings indicate that, ^uMSC EXOs accelerated the repair of critical-sized cranial defects and further promoted intrastent vascularization and osteogenesis.

3. Exosomes derived from umbilical cord mesenchymal stem cells exhibit pro-angiogenic and osteogenic effects in vitro.

In order to further determine ^uMSC The regulatory effects of EXO were evaluated by researchers with respect to Cell proliferation, migration, tubulogenesis, mineralization, and the expression of relevant angiogenic/osteogenic proteins or genes. The impact, the results indicate, ^uMSC EXOs promote the proliferation, migration, and angiogenic differentiation of endothelial progenitor cells (EPCs).

Figure 4. ^uMSC EXO’s pro-angiogenic effects on endothelial progenitor cells in vitro

RT-PCR results show ^uMSC In the EXOs/Gel group, the expression levels of pro-angiogenic genes in EPCs were significantly upregulated, including VEGFA, CD31, and HIF‑1α. With regard to in vitro osteogenic activity, the results of ALP staining, Western blot analysis, and RT‑PCR did not reveal any statistically significant differences among the groups. Based on these experimental findings, ^uMSC EXOs effectively promoted angiogenesis in EPCs in vitro, whereas their osteogenic effects on BMSCs were not significant.

Figure 5. Tube formation assay and expression levels of angiogenesis-related genes

4. Exosomes derived from umbilical cord mesenchymal stem cells are rich in miR‑21.

According to recent studies, the transfer of exosomal miRNAs to recipient cells represents a novel mechanism underlying the biological functions of exosomes. Consequently, researchers have focused on… ^HEK293 EXOs were used as the control, to pick High-throughput sequencing was used to analyze ^uMSC Overall miRNA expression in EXOs 。 Using the existing GEO dataset (GSE46989), we analyzed miRNA expression in uMSCs and found that… ^uMSC EXOs exhibit a specific miRNA peak profile, associated with ^HEK293 EXOs are even quite different from uMSCs.

In ^uMSC Among the most abundant miRNAs in EXOs, miR‑21 is highly expressed in uMSCs, a finding further confirmed by RT‑PCR. Thus, miR‑21 is the most prevalent exosomal miRNA; it may be actively secreted into exosomes by uMSCs or internalized by endothelial progenitor cells, where it can exert significant biological functions.

Figure 6. High-throughput sequencing results and validation of exosomal miRNAs

5. Exosomal miR‑21 derived from umbilical cord mesenchymal stem cells promotes angiogenesis in vitro and in vivo.

to put Transfection with miR‑21 mimics or inhibitors In the cultured uMSCs, miRNA‑21 expression was respectively upregulated and downregulated, and it was further determined whether the exosomal transfer of miR‑21 is associated with the observed… ^uMSC It is related to the functional effects of EXOs.

Endothelial progenitor cells and the regulated ^uMSC Co-culture of EXOs, and proceed with Tubule formation assay to determine the extent to which exosomal miR‑21 secreted by uMSCs influences angiogenesis. When cells were co‑cultured with EXO/miR‑21 mimetic, both the tube length and the number of branches of endothelial progenitor cells increased significantly, whereas in the EXO/miR‑21 inhibitor group, tube length and branch numbers were markedly reduced.

In addition, through Chicken Embryo CAM Assay The impact of exosomal miR‑21 on in vivo angiogenesis was evaluated. Upregulation of exosomal miR‑21 expression enhanced angiogenesis in the chorioallantoic membrane (CAM) assay. Conversely, inhibition of exosomal miR‑21 expression attenuated angiogenesis.

Figure 7. In ^uMSC Establish miR‑21 expression levels of varying intensities in EXOs and validate their ability to promote angiogenesis both in vitro and in vivo.

RT‑PCR analysis revealed that treatment with EXO/miR‑21 mimics increased the mRNA expression levels of VEGFA and HIF‑1α while decreasing those of NOTCH1 and DLL4, whereas the EXO/miR‑21 inhibitor group exhibited the opposite pattern. These findings are consistent with the WB data.

In summary, exosomal miR‑21 participates in the NOTCH1/DLL4/VEGFA signaling axis. ^uMSC EXO-mediated angiogenic function of endothelial progenitor cells promotes angiogenesis.