Platelet Rich Plasma (PRP) to treat Diabetic Foot Ulcers

Diabetes Mellitus (DM) is a disease which spares no tissue in the human body. While the big pharma has always been focused on small molecules (drugs) for curing the symptoms, the underlying pathology remains unattended. This puts the tissues under constant oxidative stress. The most vulnerable ones are the vascular and the neural tissue. Due to the accumulation of the advanced glycation end products and few other pro-oxidative products, the vascular endothelium and supplying nerve cells go for apoptosis. The end result leads to micro & macrovascular complications of diabetes. In this article, I am going to focus exclusively on diabetic foot ulcer (DFU).

DM is one of the leading cause of non-traumatic lower extremity amputation. Foot ulcers and infections are also a major source of morbidity in individuals with DM. The reasons for the increased incidence of these disorders in DM involve the interaction of several pathogenic factors: neuropathy, abnormal foot biomechanics, Peripheral Artery Disease (PAD), and poor wound healing. The peripheral sensory neuropathy interferes with normal protective mechanisms and allows the patient to sustain major or repeated minor trauma to the foot, often without the knowledge of the injury. Disordered proprioception causes abnormal weight bearing while walking and subsequent formation of callus or ulceration. Motor and sensory neuropathy lead to abnormal foot muscle mechanics and to structural changes in the foot (hammertoe, claw toe deformity, prominent metatarsal heads, Charcot joint). Autonomic neuropathy results in anhidrosis and altered superficial blood flow in the foot, which promotes drying of the skin and fissure formation. PAD and poor wound healing impede resolution of minor breaks in the skin, allowing them to enlarge and to become infected.

Approximately 15% of individuals with type 2 DM develop a foot ulcer (great toe or Metatarsal Phalangeal (MTP) areas are most common), and a significant subset will ultimately undergo amputation (14–24% risk with that ulcer or subsequent ulceration). Risk factors for DFU or amputation include: male sex, diabetes >10 years’ duration, peripheral neuropathy, abnormal structure of foot (bony abnormalities, callus, and thickened nails), PAD, smoking, history of previous ulcer or amputation and poor glycemic control. Large calluses are often precursors to or overlie ulcerations.

In a healthy individual, wound healing progresses through three sequential stages: the inflammatory phase which lasts three to five days, the proliferative phase lasting approximately two weeks, and the remodelling phase which can last from several weeks to several months, depending on the wound. Just prior to inflammation, a fibrin clot forms at the site of the wound site to provide hemostasis. Leukocyte infiltration is the hallmark of the inflammatory phase, whereby polymorphonuclear cells (PMNs) arrive to remove bacteria. Macrophages then follow and become the predominant cell by day two. Their function is antigen presentation, phagocytosis and release of various growth factors and cytokines. It is during this stage that granulation tissue formation begins. Around day three of the wound, fibroblasts begin to enter. This marks the beginning of the proliferative phase. The hallmark of this phase includes angiogenesis (neovascularization), re-epithelialization and extracellular matrix (ECM) formation. Immature type III collagen and fibronectin are deposited and make up the ECM. This highly integrated process is mediated by various growth factors and cytokines. The remodelling phase begins when the rate of collagen degradation and deposition equalize. This is characterized by continued collagen remodelling, from type III to mature type I collagen, and cross-linking within the ECM. In patients with diabetes, wounds remain stuck in the inflammatory phase. Neutrophils and macrophages continue to release inflammatory mediators. The critical balance between the proteases and their inhibitors is disturbed, preventing collagen remodelling and ECM formation. Certain functions of neutrophils and macrophages are inherently altered in diabetes, including cell adherence, chemotaxis, phagocytosis, and cytokine production and secretion. In addition, fibroblasts and keratinocytes display decreased response to growth factors, decreased migratory ability, and increased apoptosis.

The optimal therapy for DFU and amputations is prevention through identification of high-risk patients, education of the patient, and the institution of measures to prevent ulceration. High-risk patients should be identified during the routine foot examination performed on all patients with DM. Patients at high risk for ulceration or amputation may benefit from evaluation by a foot care specialist. Attention to other risk factors for vascular disease (smoking, dyslipidemia, and hypertension) and improved glycemic control are also important.

Despite preventive measures, foot ulceration and infection are common and represent a serious problem. Due to the multifactorial pathogenesis of lower extremity ulcers, management of these lesions is multidisciplinary and often demands expertise in orthopaedics, vascular surgery, endocrinology, podiatry, and infectious diseases. The plantar surface of the foot is the most common site of ulceration. Ulcers may be primarily neuropathic (no accompanying infection) or may have surrounding cellulitis or osteomyelitis. A growing number of possible treatments for diabetic foot ulcers exist, but they have yet to demonstrate clear efficacy in prospective, controlled trials. A consensus statement from the ADA identified six interventions with demonstrated efficacy in diabetic foot wounds: (1) off-loading, (2) debridement, (3) wound dressings, (4) appropriate use of antibiotics, (5) revascularization, and (6) limited amputation. Amputation of the foot is 15 times more common in diabetics than in the general population. The male: female ratio among amputees is 30:1 among nondiabetics compared to 2:1 in diabetics. Nearly 20 percent of hospital admissions of diabetics is with problems of the foot. These problems are beset with prolonged suffering, crippling disability and loss of life.

The conventional treatments of diabetic foot ulcers are costly and often require patients to be hospitalized for long periods of time, thus representing a huge burden on any health care system. The use of autologous platelet-rich plasma (PRP), which is rich in multiple growth factors, may bear some similarities to the natural wound healing process. Various growth factors, including platelet-derived growth factor (PDGF), transforming growth factor (TGF), vascular endothelial growth factor (VEGF), and insulin-like growth factor (IGF), are secreted from the α-granules of concentrated platelets activated by aggregation inducers. These factors are known to regulate processes including cell migration, attachment, proliferation and differentiation, and promote extracellular matrix (ECM) accumulation by binding to specific cell surface receptors. Due to the presence of high concentrations of these growth factors, PRP has been used in a wide variety of surgical procedures and clinical treatments, including the treatment of problematic wounds and maxillofacial bone defects, cosmetic surgeries and gastrointestinal surgeries.

In the general aspect, the mechanism by which PRP associates with wound healing begins by α-granules degradation. This phenomenon in turn, activates other related growth factors including platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), platelet-derived endothelial growth factor (PDEGF), transforming growth factor ß (TGF-ß), epidermal growth factor (EGF), insulin-like growth factor (IGF), platelet growth factor 4 (PF-4) and interleukin 1 (IL-1). All these mentioned growth factors have been proved to play roles in wound healing process. PRP is also capable of recruiting macrophages due to its chemotaxis properties and act as an anti-infection agent as well. Angiogenesis, the formation of new blood vessels from pre-existing ones mostly occurs in pathological conditions such as tumour growth, corneal neovascularization and psoriasis. On the other hand in physiological conditions, this process is mainly responsible for two main events: wound healing and female reproductive cycle. Although PRP is consists of different growth factors affecting different cells, it seems that one of the possible pathways of its action is through the induction of angiogenesis. In angiogenesis process, VEGF is a strong inducer of angiogenesis that affects proliferation and migration of endothelial cells (ECs) which are two main steps of angiogenesis. Also, VEGF is responsible for induction of other angiogenic factors. Also PDGF, TGF-ß and IGF in PRP are noted as strong angiogenic factors. In this condition, the new vascular branches could provide enough blood supply (both nutritional and oxygenation support) and also are able to remove the dust of wound healing process.

Now, the next question to be asked is, whether PRP production process has any role in the efficacy of healing DFU?

The Answer is Yes!

PRP can either be autologous (by venesection of patients) or allogeneic (pooled platelet from platelet bags available at the blood banks). The efficacy depends on the patient’s age, disease conditions, lifestyle factors, etc. Also, it depends upon the platelet activation process which determines the amount of angiogenic and other growth factors available in the PRP pool for regeneration. There are different ways of degranulating α-granules, which can also be called as activation and can be done by using calcium chloride (Ca-PRP), fetal bovine serum (FBS-PRP), pooled human thrombin (tPRP),  freeze-thaw cycles (FT-PRP), bead mill homogenizer processing (BM-PRP) and many others. Different companies offer various modalities which I am leaving it to the reader’s choice!

Drugs<>Therapeutics<>Big Pharma
impas Natesh Prabhu Administrator & Chief Editor | Clinical Pharmacologist | Diabetic-Sexual Medicine-Regenerative Therapy Consultant | President, Indian Medical Pharmacologists Association