First Experimental Study of the Influence of Extracellular Vesicles Derived from Multipotent Stromal Cells on Osseointegration of Dental Implants

Abstract

Herein, the aim was to study the state of the bone tissue adjacent to dental implants after the use of extracellular vesicles derived from multipotent stromal cells (MSC EVs) of bone marrow origin in the experiment. In compliance with the rules of asepsis and antiseptics under general intravenous anesthesia with propofol, the screw dental implants were installed in the proximal condyles of the tibia of outbred rabbits without and with preliminary introduction of 19.2 μg MSC EVs into each bone tissue defect. In 3, 7, and 10 days after the operation, the density of bone tissue adjacent to different parts of the implant using an X-ray unit with densitometer was measured. In addition, the histological examinations of the bone site with the hole from the removed device and the soft tissues from the surface of the proximal tibial condyle in the area of intra-bone implants were made. It was found out that 3 days after implantation with the use of MSC EVs, the bone density was statistically significantly higher by 47.2% than after the same implantation, but without the injection of MSC EVs. It is possible that as a result of the immunomodulatory action of MSC EVs, the activity of inflammation decreases, and, respectively, the degree of vasodilation in bones and leukocyte infiltration of the soft tissues are lower, in comparison with the surgery performed in the control group. The bone fragments formed during implantation are mainly consolidated with each other and with the regenerating bone. Day 10 demonstrated that all animals with the use of MSC EVs had almost complete fusion of the screw device with the bone tissue, whereas after the operation without the application of MSC EVs, the heterogeneous histologic pattern was observed: From almost complete osseointegration of the implant to the absolute absence of contact between the foreign body and the new formed bone. Therefore, the use of MSC EVs during the introduction of dental implants into the proximal condyle of the tibia of rabbits contributes to an increase of the bone tissue density near the device after 3 days and to the achievement of consistently successful osseointegration of implants 10 days after the surgery.

Keywords: bone tissue; bone tissue density; dental implantation; extracellular vesicles; implant osseointegration.

Figure 1

Results of studying the bone tissue of the proximal tibial condyle in control rabbits at various times after the introduction of dental implants. (a) X-ray image of the implant in the tibia 3 days after surgery, arrows indicate areas of reduced bone density. (b) Computer 3D modeling of the implant position in the bone on the 3rd day after surgery. (c) On the 3rd day after implantation, there are extensive hemorrhages and a large volume of split bone fragments in the cancellous bone, staining with hematoxylin and eosin. (d) Hemorrhages, vascular distention, and congestion (arrows) near and among the split bone particles 3 days after implant placement, stained with hematoxylin and eosin. (e) On the 10th day, the implant mostly borders with the bone tissue and only in small areas it is adjoined by loose fibrous connective tissue (arrows) with a significant number of hyperemic wide thin-walled vessels, stained with hematoxylin and eosin. (f) After 10 days the implant is delimited from the bone throughout its entire length by connective tissue with wide hyperemic vessels, stained with hematoxylin and eosin.

Figure 1

Results of studying the bone tissue of the proximal tibial condyle in control rabbits at various times after the introduction of dental implants. (a) X-ray image of the implant in the tibia 3 days after surgery, arrows indicate areas of reduced bone density. (b) Computer 3D modeling of the implant position in the bone on the 3rd day after surgery. (c) On the 3rd day after implantation, there are extensive hemorrhages and a large volume of split bone fragments in the cancellous bone, staining with hematoxylin and eosin. (d) Hemorrhages, vascular distention, and congestion (arrows) near and among the split bone particles 3 days after implant placement, stained with hematoxylin and eosin. (e) On the 10th day, the implant mostly borders with the bone tissue and only in small areas it is adjoined by loose fibrous connective tissue (arrows) with a significant number of hyperemic wide thin-walled vessels, stained with hematoxylin and eosin. (f) After 10 days the implant is delimited from the bone throughout its entire length by connective tissue with wide hyperemic vessels, stained with hematoxylin and eosin.

Figure 2

The state of the animal tibia at various times after the introduction of dental implants into the proximal condyle with the preliminary injection of MSC EVs. (a) By the 3rd day after the operation, according to the X-ray examination, the tissue rarefaction near the implant neck is insignificant (arrow), in the apex area—only along its sides (arrows). (b) Computer 3D modeling of the device position in the bone 3 days after implantation. (c) Three days after the operation, the fragments of bone detritus adhere tightly to each other, between them there are practically no corpuscles and blood vessels, stained with hematoxylin and eosin. (d) On the 7th day after implantation, next to the split parts of the bone tissue infiltrated by large cells, there are structures of new bone, possibly formed from these bone fragments, stained with hematoxylin and eosin. (e) By the 10th day, only for a short distance, the implant borders with the connective tissue (arrows), stained with hematoxylin and eosin. (f) Partial lysis, consolidation with each other, and ingrowth of split bone fragments into new forming bone structures 10 days after surgery, stained with hematoxylin and eosin.

Figure 2

The state of the animal tibia at various times after the introduction of dental implants into the proximal condyle with the preliminary injection of MSC EVs. (a) By the 3rd day after the operation, according to the X-ray examination, the tissue rarefaction near the implant neck is insignificant (arrow), in the apex area—only along its sides (arrows). (b) Computer 3D modeling of the device position in the bone 3 days after implantation. (c) Three days after the operation, the fragments of bone detritus adhere tightly to each other, between them there are practically no corpuscles and blood vessels, stained with hematoxylin and eosin. (d) On the 7th day after implantation, next to the split parts of the bone tissue infiltrated by large cells, there are structures of new bone, possibly formed from these bone fragments, stained with hematoxylin and eosin. (e) By the 10th day, only for a short distance, the implant borders with the connective tissue (arrows), stained with hematoxylin and eosin. (f) Partial lysis, consolidation with each other, and ingrowth of split bone fragments into new forming bone structures 10 days after surgery, stained with hematoxylin and eosin.

Figure 3

Results of comparing bone density, vascularization, and leukocyte infiltration in tissues of the rabbit’s proximal tibial condyle at different times after the introduction of screw implants without and with the use of cells. (a) Bone density (optical units) after implantation of metal screw products without and with using MSC EVs. (b) Length of bone contact with implant (% from length of section) after introduction of metal screw products without and with the using MSC EVs. (c) Relative area of blood vessels (% from section area) in section. (d) Numerical density of all cells (per 105 μm² of the section area) in the soft tissues from surface of the condyle. (e) Numerical density of lymphocytes (per 105 μm² of the section area) in the soft tissues from surface of the condyle. (f) Numerical density of neutrophils (per 105 μm² of the section area) in the soft tissues from surface of the condyle.

Figure 3

Results of comparing bone density, vascularization, and leukocyte infiltration in tissues of the rabbit’s proximal tibial condyle at different times after the introduction of screw implants without and with the use of cells. (a) Bone density (optical units) after implantation of metal screw products without and with using MSC EVs. (b) Length of bone contact with implant (% from length of section) after introduction of metal screw products without and with the using MSC EVs. (c) Relative area of blood vessels (% from section area) in section. (d) Numerical density of all cells (per 105 μm² of the section area) in the soft tissues from surface of the condyle. (e) Numerical density of lymphocytes (per 105 μm² of the section area) in the soft tissues from surface of the condyle. (f) Numerical density of neutrophils (per 105 μm² of the section area) in the soft tissues from surface of the condyle.