Influence of platelet-rich plasma on proliferation and osteogenic differentiation of skeletal muscle satellite cells: an in vitro study

Platelet-Rich Plasma Promotes the Expansion of Human Myoblasts and Favors the In Vitro Generation of Human Muscle Reserve Cells in a Deeper State of Quiescence

Stem cell therapy holds significant potential for skeletal muscle repair, with in vitro-generated human muscle reserve cells (MuRCs) emerging as a source of quiescent myogenic stem cells that can be injected to enhance muscle regeneration. However, the clinical translation of such therapies is hampered by the need for fetal bovine serum (FBS) during the in vitro generation of human MuRCs. This study aimed to determine whether fresh allogeneic human platelet-rich plasma (PRP) combined or not with hyaluronic acid (PRP-HA) could effectively replace xenogeneic FBS for the ex vivo expansion and differentiation of human primary myoblasts. Cells were cultured in media supplemented with either PRP or PRP-HA and their proliferation rate, cytotoxicity and myogenic differentiation potential were compared with those cultured in media supplemented with FBS. The results showed similar proliferation rates among human myoblasts cultured in PRP, PRP-HA or FBS supplemented media, with no cytotoxic effects. Human myoblasts cultured in PRP or PRP-HA showed reduced fusion ability upon differentiation. Nevertheless, we also observed that human MuRCs generated from PRP or PRP-HA myogenic cultures, exhibited increased Pax7 expression and delayed re-entry into the cell cycle upon reactivation, indicating a deeper quiescent state of human MuRCs. These results suggest that allogeneic human PRP effectively replaces FBS for the ex vivo expansion and differentiation of human myoblasts and favors the in vitro generation of Pax7High human MuRCs, with important implications for the advancement of stem cell-based muscle repair strategies.

In vitro evidence supporting applications of platelet derivatives in regenerative medicine

The role of platelets in haemostasis has long been known, but understanding of these cells' involvement in wound healing/tissue repair is more recent and has given rise to a multitude of translational studies. Tissue repair processes consist of complex, regulated interactions between cells modulated by biologically active molecules, most of which are growth factors released by activated platelets: this aspect represents the rationale on which the use of platelet derivatives for clinical purposes is based. In the last years, many in vitro studies have focused on the mechanisms of action by which these growth factors affect the biological activities of cells, thus supporting tissue healing. Although limited by some drawbacks (two-dimensional in vitro monocultures cannot replicate the tissue architecture and organisation of organs or the continuous interplay between different cell types), in vitro studies do have the advantages of giving rapid results and allowing precise control of platelet concentrations and other parameters.This review offers an updated overview of the data obtained from the most recent bench-top studies focused on the effects of platelet derivatives on a wide variety of human cells, highlighting their possible impact for in vivo applications. The heterogeneity of the data obtained so far is very evident. This can be explained by the different experimental settings used in each study, which may be the cause of the variability in clinical outcomes. In fact, in vitro studies suggest that the composition of platelet derivatives and the method used for their production and activation (or not) and the platelet concentration used can have profound effects on the final results.

Platelet-rich plasma does not reduce skeletal muscle fibrosis after distraction osteogenesis

Background

Skeletal muscle fibrosis caused by an increase in collagen deposition often occurs after distraction osteogenesis. Although studies are available reporting the effects of platelet-rich plasma (PRP) on tissue healing following injury, current findings remain controversial. This study focused on determining whether PRP reduces skeletal muscle fibrosis caused by distraction osteogenesis.

Methods

Tibial osteotomies were performed on 8-week-old wild type mice, and tibiae were distracted at a rate of 0.42 mm/day for 2 weeks, starting 1 week after osteotomy. Immediately after distraction was completed (3 weeks after osteotomy), PRP or phosphate buffered saline (as a sham) was injected into the gastrocnemius (GC) muscle. The GC muscles were harvested and analyzed.

Results

The amount and area of collagenous tissue increased in both the PRP and control groups following distraction osteogenesis, but the changes were not significantly different between both groups at all time points (p = 0.89, 0.45, 0.33 and 0.52 at 4, 6, 8 and 10 weeks).

Conclusion

From this study, our results suggest that PRP did not significantly reduce skeletal muscle fibrosis due to distraction osteogenesis.

The combination of nano-calcium sulfate/platelet rich plasma gel scaffold with BMP2 gene-modified mesenchymal stem cells promotes bone regeneration in rat critical-sized calvarial defects

BACKGROUND

Mesenchymal stem cells (MSCs) can be differentiated into an osteoblastic lineage in the presence of growth factors (GFs). Platelet-rich plasma (PRP), which can be easily isolated from whole blood, contains a large amount of GFs, and, therefore, promotes bone growth and regeneration. The main goal of this work was to develop and investigate the effect of a new sandwich-like bone scaffold which combines a nano-calcium sulfate (nCS) disc along with PRP fibrin gel (nCS/PRP) with BMP2-modified MSCs on bone repair and regeneration in rat critical-sized calvarial defects.

METHODS

We evaluated the cytotoxicity, osteogenic differentiation and mineralization effect of PRP extract on BMP2-modified MSCs and constructed a sandwich-like nCS/PRP scaffold (mimicking the nano-calcium matrix of bone and carrying multi GFs in the PRP) containing BMP2-modified MSCs. The capacity of this multifunctional bone regeneration system in promoting bone repair was assessed in vivo in a rat critical-sized (8 mm) calvarial bone defect model.

RESULTS

We developed an optimized nCS/PRP sandwich-like scaffold. Scanning electron microscopy (SEM) results showed that nCS/PRP are polyporous with an average pore diameter of 70-80 μm and the cells can survive in the nCS/PRP scaffold. PRP extract dramatically stimulated proliferation and differentiation of BMP2-modified MSCs in vitro. Our in vivo results showed that the combination of BMP2-modified MSCs and nCS/PRP scaffold dramatically increased new bone regeneration compared with the groups without PRP and/or BMP2.

CONCLUSIONS

nCS/PRP scaffolds containing BMP2-modified MSCs successfully promotes bone regeneration in critical-sized bone defects. This system could ultimately enable clinicians to better reconstruct the craniofacial bone and avoid donor site morbidity for critical-sized bone defects.

The composite of bone marrow concentrate and PRP as an alternative to autologous bone grafting

One possible alternative to the application of autologous bone grafts represents the use of autologous bone marrow concentrate (BMC). The purpose of our study was to evaluate the potency of autologous platelet-rich plasma (PRP) in combination with BMC. In 32 mini-pigs a metaphyseal critical-size defect was surgically created at the proximal tibia. The animals were allocated to four treatment groups of eight animals each (1. BMC+CPG group, 2. BMC+CPG+PRP group, 3. autograft group, 4. CPG group). In the BMC+CPG group the defect was filled with autologous BMC in combination with calcium phosphate granules (CPG), whereas in the BMC+CPG+PRP group the defect was filled with the composite of autologous BMC, CPG and autologous PRP. In the autograft group the defect was filled with autologous cancellous graft, whereas in the CPG group the defect was filled with CPG solely. After 6 weeks radiological and histomorphometrical analysis showed significantly more new bone formation in the BMC+CPG+PRP group compared to the BMC+CPG group and the CPG group. There were no significant differences between the BMC+CPG+PRP group and the autograft group. In the PRP platelets were enriched significantly about 4.7-fold compared to native blood. In BMC the count of mononuclear cells increased significantly (3.5-fold) compared to the bone marrow aspirate. This study demonstrates that the composite of BMC+CPG+PRP leads to a significantly higher bone regeneration of critical-size defects at the proximal tibia in mini-pigs than the use of BMC+CPG without PRP. Furthermore, within the limits of the present study the composite BMC+CPG+PRP represents a comparable alternative to autologous bone grafting.

Platelet-rich plasma promotes healing of osteoporotic fractures

With an aging population worldwide, the frequency of osteoporotic fractures is increasing. Therefore, biological methods to enhance the internal fixation of osteoporotic fractures becomes more important to reduce the societal burden of care. The purposes of this study were to evaluate the role of platelet-rich plasma (PRP) in the treatment of osteoporotic fractures and to clarify the best concentration of PRP. Bone marrow mesenchymal stem cells isolated from osteoporotic rats were cultured in high- (8.21±0.4×10(9)/mL), medium-(2.65±0.2×10(9)/mL), and low-concentration (0.85±0.16×10(9)/mL) PRP and in platelet-poor plasma (8±0.5×10(6) platelet/mL). The capacities of cell proliferation and osteogenic and adipogenic differentiation were compared. A transverse osteotomy was performed in the middle of the left femoral diaphysis followed by K-wire fixation, and various concentrations of PRP were transplanted into the fracture zone. Radiologic, mechanical, and histologic evaluations were performed at 2, 4, and 8 weeks, respectively. The results indicated that PRP could inhibit adipogenic differentiation and that medium-concentration PRP was effective in inducing the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells derived from osteoporotic bone marrow and in promoting fracture healing, whereas high-concentration PRP inhibited osteogenic differentiation and callus remodeling. Certain concentrations of PRP can effectively enhance the healing of osteoporotic fractures. Medium-concentration PRP is a suitable concentration to use in practice.

Cell metabolism sets the differences between subpopulations of satellite cells (SCs)

Background

We have recently characterized two distinct populations of Satellite Cells (SCs) that differ in proliferation, regenerative potential, and mitochondrial coupling efficiency and classified these in Low Proliferative Clones (LPC) and High Proliferative Clones (HPC). Herewith, we have investigated their cell metabolism and individuated features that remark an intrinsic difference in basal physiology but that are retrievable also at the initial phases of their cloning.

Results

Indeed, LPC and HPC can be distinguished for mitochondrial membrane potential (ΔΨ_m) just after isolation from the fiber. This is matched by mitochondrial redox state measured via NAD⁺/NADH analysis and alternative respiratory CO₂ production in cloned cells. All these parameters are accountable for metabolic differences reflected indeed by alternative expression of the glycolytic enzyme 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (Pfkfb3). Also Ca²⁺ handling by mitochondria is different together with the sensitivity to apoptosis triggered via this pathway. Finally, according to the above, we were able to determine which one among the clones represents the suitable stem cell.

Conclusions

These experimental observations report novel physiological features in the cell biology of SCs and refer to an intrinsic heterogeneity within which their stemness may reside.