Allogeneic Platelet Rich Plasma (PRP) to Treat Diabetic Foot Ulcers

Background Skin ulcers are open sores often accompanied by the sloughing-off of inflamed tissue. Chronic skin ulcers pose a major global health burden since they are closely linked to population aging and chronic diseases such as diabetes . There is a strong association between pain and quality of life, which are worse for larger ulcers with longer duration. Women have both more pain and poorer quality of life than men. Chronic skin ulcers recur frequently and heal poorly. 1/5 ulcers are still not healed after 2 years, and 1/12 are still open after 5 years and can last more than 10 years. Diabetes is the most common cause of ulcers in Europe and the USA. Diabetic patients have a lifetime risk of foot ulcer as high as 25%. Non healing chronic ulcers of the lower limbs in patients with type 1 or 2 diabetes are at increased risk of complications, including infections and amputation. Approximately 50% of diabetic foot ulcers become infected, and 20% of these require amputation .

Chronic skin ulcers are difficult to treat also because of impaired blood flow and infection. Present standard treatment of diabetic ulcers includes regular debridement, off-loading, treatment of infection, revascularization when appropriate,optimizing metabolic control, and the treatment of any concomitant diseases, as well as education about foot care and the provision of appropriate footwear. However, healing rates are highly variable, and recurrences frequent .

Autologous Platelet Rich Plasma (PRP) to treat chronic skin ulcers through the reactivation of dormant endogenous regeneration mechanisms is truly innovative. In fact, PRP not only increases endothelial cells recruitment and improves vascularization, but also promotes recruitment of macrophages which, in turn, through their paracrine activity, recruit and stimulate proliferation of mesenchymal and epithelial stem/progenitor cells, leading to synthesis of extracellular matrix molecules and skin regeneration. There is clinical evidence that autologous PRP gel therapy improves healing of chronic skin ulcers, but treatment of diabetic ulcers by autologous PRP is often hampered because diabetes leads to a reduced and/or inadequate production of growth factors, angiogenic response, impaired function of macrophages, reduced formation of granulation tissue, abnormal migration, and proliferation of fibroblasts and keratinocytes.

Moreover, before this new therapeutic approach can be available to a large population of patients, several issues need to be addressed. While some groups reported encouraging results on PRP as enhancer of tissue healing, others failed to observe an improvement in the healing process. This may be due to a poor quality of the PRP. In fact, there is significant inter-individual variability in platelet concentration, which can significantly vary depending on the health status of the different patients. Variability also exists in preparations from different Centers. In many cases, PRP is prepared based on non-standardized protocols, or by using commercially available devices that may be not fully adequate. Further limitations include difficulty to obtain sufficient quantities of blood from the elderly, or from debilitated patients with limited mobility, as well as the lack of prompt PRP availability, and the high production cost.

Hyphothesis and Significance:

The use of allogeneic PRP, obtained from a pool of blood donations, would be advantageous over the use of autologous PRP, and could be the only alternative when the autologous PRP is not available.

This multicenter clinical trial tested an allogeneic platelet-derived product, obtained from pools of blood donations according to standardized large-scale procedures. This product would represent a substantial improvement in the treatment of chronic skin ulcers. Furthermore, allogeneic PRP - produced in batches and not immediately used underwent a rigorous Quality Control analysis before its clinical use.

Specific Aim 1:

Implementation of a phase II, multicenter, double-blind, randomized controlled trial on "off the shelf" allogeneic PRP to treat diabetic foot ulcers. The protocol was approved by the pertinent Ethical Committees prior to project start.

The trial was conducted in accordance with the protocol and in compliance with European and local legal and regulatory requirements, as well as the general principles set forth in the Guidelines for Good Clinical Practice (CPMP/ICH/135/1995) and the Declaration of Helsinki (World Medical Association - 2013).

The primary aim of this study was to evaluate whether allogeneic PRP could improve the rate of healing of foot ulcers in diabetic patients. Preparations of allogeneic PRP in association with hyaluronic acid dressing were compared with hyaluronic acid only.

The primary endpoint is the cumulative rate of wound healing at the end of the 12 week follow-up.

Patients were randomized in a 1:1 ratio to:

• Experimental Group: Treatment with offloading, debridement, and hyaluronic acid gel + PRP gel;
• Control Group: Treatment with offloading, debridement, and hyaluronic acid gel

Specific Aim 2:

Secondary aim was the evaluation of the safety of the allogeneic PRP.

Specific Aim 3:

Third aim was to study the immune response after allogeneic PRP treatment.