Buccal Mesenchymal Stromal Cells as a Source of Osseointegration of Titanium Implants.

We studied the interaction of human buccal mesenchymal stem cells (MSCs) and osteoblasts differentiated from them with the surface of titanium samples. MSCs were isolated by enzymatic method from buccal fat pads. The obtained cell culture was presented by MSCs, which was confirmed by flow cytometry and differentiation into adipocytes and osteoblasts. Culturing of buccal MSCs on titanium samples was accompanied by an increase in the number of cells for 15 days and the formation of a developed network of F-actin fibers in the cells. The viability of buccal MSCs decreased by 8 days, but was restored by 15 days. Culturing of osteoblasts obtained as a result of buccal MSC differentiation on the surface of titanium samples was accompanied by a decrease in their viability and proliferation. Thus, MSCs from buccal fat pads can be used to coat implants to improve osseointegration during bone reconstruction in craniofacial surgery and dentistry. To improve the integration of osteoblasts, modification of the surface of titanium samples is required.

[Peculiarities of angiogenesis after the implantation of polyhydroxyalkanoate films with the adsorbed multipotent stromal stem cells of a bone marrow origin].

The processes developing in various rat tissues after implantation of polymeric polyhydroxyalkanoate (PHA) film fragments with adsorbed autologous multipotent stromal (mesenchymal) cells of bone marrow origin (AMMSCBM), were studied by methods of light microscopy. After the implantation of PHA film with AMMSCBM, the number of blood vessels in the surrounding tissues was found to increase as a result of neoangiogenesis. In this case,AMMSCBM did not migrate and were not destroyed at the place of injection, but differentiated into the cells forming blood vessel structures. The processes of angiogenesis in the tissues around PHA implant, in turn, lead to development of a larger number of blood vessels in the granulations formed around the implanted foreign body, higher volume of granulations proper and subsequent development of a thicker capsule delimiting polymer implant.

Reaction of the rat tissues to implantation of polyhydroxyalkanoate films and ultrafine fibers.

The reaction of various tissues of rats to implantation of polyhydroxyalkanoate films and ultrafine fibers was studied by optic microscopy. Implantation of polyhydroxyalkanoate films into the abdominal cavity caused a peritoneal reaction, leading after 1 month to the formation of fibrous adhesions between polyhydroxyalkanoate and intestinal loops. Under the skin and in the muscle tissue polyhydroxyalkanoate films were encapsulated in a thick fibrous capsule. Implantation of polyhydroxyalkanoate ultrathin fibers led to formation of foreign body granulomas in all tissues with perifocal inflammation and sclerosis of the adjacent tissues. The polymer was fragmented in these granulomas and phagocytosed by macrophages with the formation of giant foreign body cells. Hence, polyhydroxyalkanoate materials implanted in vivo caused chronic granulomatous inflammatory reaction and were very slowly destroyed by macrophages.

[Morphological tissue changes after the implantation of elastic lamellar foreign bodies in the experiment].

The reaction of rat tissues was studied using the methods of light microscopy 4, 12, 18 days, 1, 2, 6 and 12 months after hypodermic implantation of polymeric films made of polyhydroxyalkanoates (PHA). It was found that polymer, like any foreign matter in an organism, become immediately covered by fibrin. By day 4, there the deformation and destruction of polymeric films were observed due to fibrin contraction. Further, the foreign body was covered by a connective tissue capsule. Under the action of myofibroblasts, the capsule around PHA contracted, thus further deforming and breaking the polymer. Small particles of polymer were covered by macrophages, after some time the cytoplasm of macrophages fused forming the giant cells of foreign body type. After the prolonged period, small fragments of polymeric films were almost completely degraded by macrophages. Large polymeric fragments that were not deformed or crushed, became encapsulated by fibrous tissue and remained unchanged for long time periods.

Regeneration of red bone marrow in rat lower jaw after transplantation of mesenchymal stem cells into the site of injury.

Regeneration processes in rat mandibular bone after transplantation of a suspension of autologous BM MSC in culture medium were studied by methods of light microscopy and X-ray densitometry. It was found that the structures of red BM in the callus after transplantation of autologous BM MSC formed earlier than in natural reparation. The formation of cavities containing BM determines lower tissue density at the site of injury after transplantation of autologous BM MSC on weeks 4 and 5 of observation than during spontaneous healing. These changes progressed throughout the observation period and attested to accelerated bone tissue reparation.

[The effect of autologous mesenchymal stem cells of bone marrow origin on regeneration of damaged rat bottom jaw bone].

The regeneration processes after introduction in site of damaged bone of rat bottom jaw of autologous mesenchymal stem cells of bone marrow origin (AMSCBMO) in suspension were studied by methods of light microscopy and x-ray densitometry. Morphological methods showed that formation of red bone marrow in bone callosity occurs much earlier after use AMSCBMO than in the time of natural course of reparation. Formation of cavities with a marrow decreases tissue density after application AMSCBMO in a site of damage in 4 and 5 weeks of supervision. The specified changes progress during all time of observation and are the certificate of accelerated development of regenerative processes in bone tissue.

[Results of fibrin clot application for acceleration of regeneration of the damaged mandible in experiment].

The processes of regeneration of the damaged rat bottom jaw bone after application of enriched thrombocytes a fibrin clot were studied by morphological and radiovisiographic methods. At a natural course of regeneration the artificial aperture of bone was filled with blood and there the blood clot was formed. After 1 week the separate bone islets of a young tissue occurred in bone defect. In 2-3 weeks the aperture in a bottom jaw bone was completely closed by a young bone tissue. After operation with filling of bone bottom jaw defect by fibrin clot there was no formation of a blood clot. Already after 1 week the bone tissue defect was filled by the merged islets of again generated bone. By second week after fibrin use the further formation of bone tissue in defect and formation of a bone callosity was noted.

[The peculiarities of rat tissue reactions to intraperitoneal implants made out of biodegradable polyhydroxyalkanoates].

The reaction of rat tissues to intraperitoneal placement of implants made out of biodegradable polyhydroxyalkanoates (PHA), was studied at different time points after the operation by the methods of light microscopy. It was found that after intraperitoneal PHA implant placement, the active adhesive process started leading to formation of fibrous adhesions between PHA implants and intestinal loops. When PHA implants were used in the form of films, they became surrounded by a thick fibrous capsule. As a result of PHA implant placement in the form of ultrathin fibers, the extensive foreign body granulomas with perifocal inflammation and sclerosis of surrounding tissues were formed. In these granulomas the polymer fragmentation and phagocytosis by macrophages with formation of giant cells of foreign body occured. It is concluded that PHA implants are not biodegradable and induce tissue reactions similar to those caused by other foreign bodies.

Peculiarities of using stem cells for regeneration of the bone and cartilage tissue.

Scientific literature about the use of MSC contains clinical and experimental data on the efficiency of cell technologies for restoration of the osteoarticular apparatus. The use of MSC immobilized in the appropriate carriers and differentiation of these cells towards the bone cells and chondrocytes are of crucial importance. However, the use of MSC, both individual and in combination with other preparations and substances has a number of drawbacks and advantages. The absence of published reports on contraindications and complications of cell therapy is worthy of note, because the analysis of unsuccessful application of MSC will help to determine the indication for this treatment, and hence, to improve the efficiency of cell technologies in the future. Wider use of MSC in clinical practice and experimental studies for acceleration of reparative processes in the bone and cartilage tissue seems to be promising.

[Regeneration of the damaged mandibular bone in rat after the injection of autologous mesenchymal stem cells of bone marrow origin adsorbed on the fibrin clot].

The processes of the repair of the damaged mandibular bone in rats were studied using light microscopy and x-ray densitometry at various time intervals after the local injection of the platelet-rich fibrin clot (PRFC), autologous mesenchymal (stromal) stem cells of bone marrow origin (AMSCBMO) or AMSCBMO, adsorbed on PRFC, into the damaged site. The best results were obtained after the application of PRFC with AMSCBMO. One week after the operation, the mandibular bone defect was largely filled with the newly formed bone tissue. It seems most probable that in this case the effects of fibrin and stem cells on the damaged bone were summarized or even amplified. Bone formation in these cases appeared to begin in the center, but not at the edges, of the defect. AMSCBMO were distributed over the whole volume of PRFC, filling all the defect more or less uniformly. As a result, maximally fast and successful restoration of bone tissue was reached in the area of the defect.

[Cellular technologies in dentistry and maxillofacial surgery].

Recent clinical and experimental researches on application of mesenchymal stem cells (MSC) in dentistry and maxillofacial surgery showed the efficiency of cellular technologies for acceleration of tissue regeneration and implants integration. However use of MSC solely and in combination with other substances has its advantages and disadvantages. There is lack of scientific data on contraindications and complications of cellular therapy whereas the analysis of failures of MSC application will allow accurately define indications and raise the efficiency of cellular technologies. There is a strong need for further clinical and experimental studies on MSC application for bone tissue regeneration.

[Submandibular lymph nodes of rats with arterial hypertension after mandible bone damage].

The structure of submandibular lymph nodes (LN) from rats with arterial hypertension (AH) and normal pressure after mandible damage was investigated by methods of light microscopy. It was revealed that in submandibular LN of both compared groups of animals after induction of inflammatory reaction cortical field was extended, bulk density of lymphoid nodules without reproductive centres was increased, in nodules with centres mantle was extended and germinative centres were decreased. In all structures of LN the numbers of mitosis, imrnuno - and plasmoblasts were increased, the contents of reticular cells and macrophages were increased only to 4-5 week. In structure of LN from rats with normal arterial pressure and with AH the volume of sinus system statistically significantly differed: animals with AH had more volume of sinuses on all points of observation. Inflammation in the conditions of AH the distinction in cellular content of various zones of LN were connected with occurrence or higher number of erythrocytes.