Platelet activation, begins within 10 minutes of growth factors secretion. The viability of the platelets and continued release of growth factors into the tissue continues for seven days.
Circulating platelets secrete growth factors such as
- Platelet-derived growth factor (stimulates cell replication, angiogenesis)
- Vascular endothelial growth factor (vessel growth),
- Fibroblast growth factor (Collagen formation)
- Insulin- like growth factor-1 (mediates growth and repair of skeletal muscle),
Meantime, the platelets stimulate the influx of macrophages, stem cells and other repair cells, as discussed previously. Micro-trauma created by the injection itself also stimulates influx of macrophages and growth factors as in the case of dextrose Prolotherapy. Once the platelets die (average life span 7-10 days), the macrophages continue wound healing regulation by secreting some of the same growth factors as the platelets did, as well as others.
The amount of initial platelets present in the wound determines the rate of wound healing and explains why PRP used during a surgical procedure speeds recovery. This may be because PRP has a strong effect in the early phase of healing. Use of a “matrix” such as adipose tissue or collagen fibers to hold the PRP material has been used – especially in the case of a large defect.