Effects of bone tissue engineering triad components on vascularization process: comparative gene expression and histological evaluation in an ectopic bone-forming model

Applications of honeybee-derived products in bone tissue engineering

Nowadays, there is an increasing prevalence of bone diseases and defects caused by trauma, cancers, infections, and degenerative and inflammatory conditions. The restoration of bone tissue lost due to trauma, fractures, or surgical removal resulting from locally invasive pathologies requires bone regeneration. As an alternative to conventional treatments, sustainable materials based on natural products, such as honeybee-derived products (honey, propolis, royal jelly, bee pollen, beeswax, and bee venom), could be considered. Honeybee-derived products, particularly honey, have long been recognized for their healing properties. There are a mixture of phytochemicals that offer bone protection through their antimicrobial, antioxidant, and anti-inflammatory properties. This review aims to summarize the current evidence regarding the effects of honeybee-derived products on bone regeneration. In conclusion, honey, propolis, royal jelly, beeswax, and bee venom can potentially serve as natural products for promoting bone health.

Vascularization and osteogenesis in ectopically implanted bone tissue-engineered constructs with endothelial and osteogenic differentiated adipose-derived stem cells

BACKGROUND

A major problem in the healing of bone defects is insufficient or absent blood supply within the defect. To overcome this challenging problem, a plethora of approaches within bone tissue engineering have been developed recently. Bearing in mind that the interplay of various diffusible factors released by endothelial cells (ECs) and osteoblasts (OBs) have a pivotal role in bone growth and regeneration and that adjacent ECs and OBs also communicate directly through gap junctions, we set the focus on the simultaneous application of these cell types together with platelet-rich plasma (PRP) as a growth factor reservoir within ectopic bone tissue engineering constructs.

AIM

To vascularize and examine osteogenesis in bone tissue engineering constructs enriched with PRP and adipose-derived stem cells (ASCs) induced into ECs and OBs.

METHODS

ASCs isolated from adipose tissue, induced in vitro into ECs, OBs or just expanded were used for implant construction as followed: BPEO, endothelial and osteogenic differentiated ASCs with PRP and bone mineral matrix; BPUI, uninduced ASCs with PRP and bone mineral matrix; BC (control), only bone mineral matrix. At 1, 2, 4 and 8 wk after subcutaneous implantation in mice, implants were extracted and endothelial-related and bone-related gene expression were analyzed, while histological analyses were performed after 2 and 8 wk.

RESULTS

The percentage of vascularization was significantly higher in BC compared to BPUI and BPEO constructs 2 and 8 wk after implantation. BC had the lowest endothelial-related gene expression, weaker osteocalcin immunoexpression and Spp1 expression compared to BPUI and BPEO. Endothelial-related gene expression and osteocalcin immunoexpression were higher in BPUI compared to BC and BPEO. BPEO had a higher percentage of vascularization compared to BPUI and the highest CD31 immunoexpression among examined constructs. Except Vwf, endothelial-related gene expression in BPEO had a later onset and was upregulated and well-balanced during in vivo incubation that induced late onset of Spp1 expression and pronounced osteocalcin immunoexpression at 2 and 8 wk. Tissue regression was noticed in BPEO constructs after 8 wk.

CONCLUSION

Ectopically implanted BPEO constructs had a favorable impact on vascularization and osteogenesis, but tissue regression imposed the need for discovering a more optimal EC/OB ratio prior to considerations for clinical applications.

Tissue response to biphasic calcium phosphate covalently modified with either heparin or hyaluronic acid in a mouse subcutaneous implantation model

Biphasic calcium phosphate (BCP) materials are widely employed as bone substitute materials due to their resorption/degradation properties. Inflammation after implantation of such materials represents a prerequisite for bone tissue repair and regeneration but can be also problematic if it is not only transient and if it is followed by fibrosis and scarring. Here, we modified BCP covalently with hyaluronan (HA) and heparin (Hep), glycosaminoglycans that possess anti-inflammatory properties. Beside the characterization of particle surface properties, the focus was on in vivo tissue response after subcutaneous implantation in mice. Histological analysis revealed a decrease in signs of inflammatory response to BCP when modified with either HA or Hep. Reduced vascularization after 30 days was noticed when BCP was modified with either HA or Hep with greater cellularity in all examined time points. Compared to plain BCP, expression of endothelial-related genes Flt1 and Vcam1 was higher in BCP-HA and BCP-Hep group at day 30. Expression of osteogenesis-related genes Sp7 and Bglap after 30 days was the highest in BCP group, followed by BCP-Hep, while the lowest expression was in BCP-HA group which correlates with collagen amount. Hence, coating of BCP particles with HA seems to suppress inflammatory response together with formation of new bone-like tissue, while the presence of Hep delays the onset of inflammatory response but permits osteogenesis in this subcutaneous bone-forming model. Transferring the results of this study to other coated materials intended for biomedical application may also pave the way to reduction of inflammation after their implantation.

The Effect of Conditioned Media of Stem Cells Derived from Lipoma and Adipose Tissue on Macrophages' Response and Wound Healing in Indirect Co-culture System In Vitro

Immunomodulatory and wound healing activities of adipose-derived stem cells (ADSCs) have been reported in various in vitro and in vivo experimental models suggesting their beneficial role in regenerative medicine and treatments of inflammatory-related disorders. Lipoma-derived stem cells (LDSCs) were reported as a potential tool in regenerative medicine due to the similarity with ADSCs but we have previously shown that LDSCs have different differentiation capacity than ADSCs despite a similar mesenchymal phenotype. To further analyze the potential differences and/or similarities between those two stem cell types, in the present study we examined the macrophages (MΦs)’ response, immunomodulatory and wound healing effect of conditioned media (CM) of LDSCs and ADSCs in indirect co-culture system in vitro. We confirmed similar mesenchymal phenotype and stemness state of LDSCs and ADSCs but indicated differences in expression of some inflammatory-related genes. Anti-inflammatory potential of CM of LDSCs and ADSCs, with pronounced effect of LDSCs, in unstimulated RAW 264.7 MΦs was evaluated by decrease in Tnf and increase in Il10 gene expression, which was confirmed by corresponding cytokines’ secretion analysis. Conditioned media of both LDSCs and ADSCs led to the functional activation of MΦs, with slightly more pronounced effect of CM of LDSCs, while both stimulated wound healing in vitro in a similar manner. Results of this study suggest that LDSCs secrete soluble factors like ADSCs and therefore may have a potential for application in regenerative medicine, due to immunomodulatory and wound healing activity, and indicate that LDSCs through secretome may interact with other cells in lipoma tissue.