Limits...
Theranostic mRNA-loaded microbubbles in the lymphatics of dogs: implications for drug delivery.

Dewitte H, Vanderperren K, Haers H, Stock E, Duchateau L, Hesta M, Saunders JH, De Smedt SC, Lentacker I - Theranostics (2015)

Bottom Line: Our results indicate that both types of microbubbles are equally capable of rapidly entering the lymph vessels and nodes upon injection, and novel, valuable and detailed information on the lymphatic structure in the animals could be obtained.Importantly, neither the microbubble migration distance within the lymphatics, nor the observed contrast signal intensity was influenced by mRNA-loading.Although further optimization of acoustic parameters will be needed, this could represent a first step towards ultrasound-guided, ultrasound-triggered intranodal mRNA delivery using these theranostic microbubbles.

View Article: PubMed Central - PubMed

Affiliation: 1. Laboratory for General Biochemistry and Physical Pharmacy, Faculty of Pharmacy, Ghent University, Ghent, Belgium;

ABSTRACT
Microbubbles have shown potential as intralymphatic ultrasound contrast agents while nanoparticle-loaded microbubbles are increasingly investigated for ultrasound-triggered drug and gene delivery. To explore whether mRNA-nanoparticle loaded microbubbles could serve as theranostics for detection of and mRNA transfer to the lymph nodes, we investigate the behavior of unloaded and mRNA-loaded microbubbles using contrast-enhanced ultrasound imaging after subcutaneous injection in dogs. Our results indicate that both types of microbubbles are equally capable of rapidly entering the lymph vessels and nodes upon injection, and novel, valuable and detailed information on the lymphatic structure in the animals could be obtained. Furthermore, additional observations were made regarding the dynamics of microbubble lymph node uptake. Importantly, neither the microbubble migration distance within the lymphatics, nor the observed contrast signal intensity was influenced by mRNA-loading. Although further optimization of acoustic parameters will be needed, this could represent a first step towards ultrasound-guided, ultrasound-triggered intranodal mRNA delivery using these theranostic microbubbles.

Show MeSH

Related in: MedlinePlus

Influence of animal properties on the lymphatic CEUS images. Pictures show the CEUS images obtained after s.c. injection of unloaded microbubbles around the mammary glands of a male dog (A1), a spayed female dog (B1) and an intact female dog (C1). Respective B-mode images are shown in A2, B2 and C2. The injection site is indicated as “i.s.” (the injection site for images C1 and C2 is out of the field-of-view), arrows indicate the accumulation of microbubbles in the lymph nodes and lymph vessels are pointed out with asterisks. Time after microbubble injection is noted on the CEUS images (in min:s).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4265751&req=5

Figure 2: Influence of animal properties on the lymphatic CEUS images. Pictures show the CEUS images obtained after s.c. injection of unloaded microbubbles around the mammary glands of a male dog (A1), a spayed female dog (B1) and an intact female dog (C1). Respective B-mode images are shown in A2, B2 and C2. The injection site is indicated as “i.s.” (the injection site for images C1 and C2 is out of the field-of-view), arrows indicate the accumulation of microbubbles in the lymph nodes and lymph vessels are pointed out with asterisks. Time after microbubble injection is noted on the CEUS images (in min:s).

Mentions: First of all, we noticed important differences in the migration of the microbubbles depending on the location of the injection site. When injecting the microbubbles in the groin, close to the inguinal lymph node, we could not observe any lymphatic uptake of the contrast agents. The reasons for this are probably dual. First of all, lymphatic uptake occurs through a passive process that depends on the interstitial pressure at the injection site. Hence, regions such as the groin, where the skin is loose and the interstitial pressure is low, are not preferable 27. In addition to pressure-related differences, some tissues, such as the mammary regions of female dogs, contain a more developed lymph vessel network. In accordance to this, initial s.c. injections of the contrast agents in the loose skin of the abdominal region did not result in migration of the contrast agents from the injection site. This despite the fact that the microbubbles were injected at a distance of merely 20 mm from the inguinal lymph node, as indicated by palpation and B-mode ultrasound imaging. On the other hand, injection around the dog's nipple resulted in extensive microbubble drainage in all female dogs, as shown in Figure 2. Migration from the injection site was seen for all injections with both unloaded (8/8) and mRNA-loaded (8/8) microbubbles in the female dogs, and after most of the injections around the nipples of the male dogs (4/4 for the unloaded bubbles and 2/4 for the mRNA-loaded bubbles). This is not unexpected, as the mammary regions accommodate a vast network of lymph vessels that lead to multiple clusters of lymph nodes close to the mammary glands, as well as more distant gastric and mesenteric lymph nodes, depending on the location of the mammary gland (e.g. axillary versus inguinal mammary glands) 28. Based on these observations, further injections were performed s.c. around the left and right nipple of the inguinal mammary gland.


Theranostic mRNA-loaded microbubbles in the lymphatics of dogs: implications for drug delivery.

Dewitte H, Vanderperren K, Haers H, Stock E, Duchateau L, Hesta M, Saunders JH, De Smedt SC, Lentacker I - Theranostics (2015)

Influence of animal properties on the lymphatic CEUS images. Pictures show the CEUS images obtained after s.c. injection of unloaded microbubbles around the mammary glands of a male dog (A1), a spayed female dog (B1) and an intact female dog (C1). Respective B-mode images are shown in A2, B2 and C2. The injection site is indicated as “i.s.” (the injection site for images C1 and C2 is out of the field-of-view), arrows indicate the accumulation of microbubbles in the lymph nodes and lymph vessels are pointed out with asterisks. Time after microbubble injection is noted on the CEUS images (in min:s).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4265751&req=5

Figure 2: Influence of animal properties on the lymphatic CEUS images. Pictures show the CEUS images obtained after s.c. injection of unloaded microbubbles around the mammary glands of a male dog (A1), a spayed female dog (B1) and an intact female dog (C1). Respective B-mode images are shown in A2, B2 and C2. The injection site is indicated as “i.s.” (the injection site for images C1 and C2 is out of the field-of-view), arrows indicate the accumulation of microbubbles in the lymph nodes and lymph vessels are pointed out with asterisks. Time after microbubble injection is noted on the CEUS images (in min:s).
Mentions: First of all, we noticed important differences in the migration of the microbubbles depending on the location of the injection site. When injecting the microbubbles in the groin, close to the inguinal lymph node, we could not observe any lymphatic uptake of the contrast agents. The reasons for this are probably dual. First of all, lymphatic uptake occurs through a passive process that depends on the interstitial pressure at the injection site. Hence, regions such as the groin, where the skin is loose and the interstitial pressure is low, are not preferable 27. In addition to pressure-related differences, some tissues, such as the mammary regions of female dogs, contain a more developed lymph vessel network. In accordance to this, initial s.c. injections of the contrast agents in the loose skin of the abdominal region did not result in migration of the contrast agents from the injection site. This despite the fact that the microbubbles were injected at a distance of merely 20 mm from the inguinal lymph node, as indicated by palpation and B-mode ultrasound imaging. On the other hand, injection around the dog's nipple resulted in extensive microbubble drainage in all female dogs, as shown in Figure 2. Migration from the injection site was seen for all injections with both unloaded (8/8) and mRNA-loaded (8/8) microbubbles in the female dogs, and after most of the injections around the nipples of the male dogs (4/4 for the unloaded bubbles and 2/4 for the mRNA-loaded bubbles). This is not unexpected, as the mammary regions accommodate a vast network of lymph vessels that lead to multiple clusters of lymph nodes close to the mammary glands, as well as more distant gastric and mesenteric lymph nodes, depending on the location of the mammary gland (e.g. axillary versus inguinal mammary glands) 28. Based on these observations, further injections were performed s.c. around the left and right nipple of the inguinal mammary gland.

Bottom Line: Our results indicate that both types of microbubbles are equally capable of rapidly entering the lymph vessels and nodes upon injection, and novel, valuable and detailed information on the lymphatic structure in the animals could be obtained.Importantly, neither the microbubble migration distance within the lymphatics, nor the observed contrast signal intensity was influenced by mRNA-loading.Although further optimization of acoustic parameters will be needed, this could represent a first step towards ultrasound-guided, ultrasound-triggered intranodal mRNA delivery using these theranostic microbubbles.

View Article: PubMed Central - PubMed

Affiliation: 1. Laboratory for General Biochemistry and Physical Pharmacy, Faculty of Pharmacy, Ghent University, Ghent, Belgium;

ABSTRACT
Microbubbles have shown potential as intralymphatic ultrasound contrast agents while nanoparticle-loaded microbubbles are increasingly investigated for ultrasound-triggered drug and gene delivery. To explore whether mRNA-nanoparticle loaded microbubbles could serve as theranostics for detection of and mRNA transfer to the lymph nodes, we investigate the behavior of unloaded and mRNA-loaded microbubbles using contrast-enhanced ultrasound imaging after subcutaneous injection in dogs. Our results indicate that both types of microbubbles are equally capable of rapidly entering the lymph vessels and nodes upon injection, and novel, valuable and detailed information on the lymphatic structure in the animals could be obtained. Furthermore, additional observations were made regarding the dynamics of microbubble lymph node uptake. Importantly, neither the microbubble migration distance within the lymphatics, nor the observed contrast signal intensity was influenced by mRNA-loading. Although further optimization of acoustic parameters will be needed, this could represent a first step towards ultrasound-guided, ultrasound-triggered intranodal mRNA delivery using these theranostic microbubbles.

Show MeSH
Related in: MedlinePlus