Use of Homologous Platelet Gel to Manage Refractory Diabetic Lower Extremity Ulcers: Additional Experience at a Tertiary Hospital

Lower extremity complications are common in patients with diabetes. The lifetime risk for developing a foot ulcer in patients with diabetes is estimated to be as high as 34%.^1,2 DLEUs, most often foot ulcers, are a major cause of morbidity, hospitalization, and lower limb amputation.³ Therefore, prompt and appropriate management of DLEU is important, and new methods to achieve ulcer healing have been described, including application of PRP or PG.⁴

Wound healing is a complex process that involves multiple cells, extracellular matrix, and mediators such as growth factors and cytokines.⁵ Neuropathy, peripheral arterial disease, foot deformities, and unnoticed minor trauma contribute to the development of foot ulcers in patients with diabetes.⁴ These patients also experience impaired wound healing, which can result in a chronic wound.^4,6

PRP and PG are rich in platelets and release growth factors, namely, transforming growth factor beta, platelet-derived growth factor, insulin-like growth factor-1, fibroblast growth factor, endothelial growth factor, vascular endothelial growth factor, and endothelial cell growth factor.^7-9 PRP and PG also contain cytokines and chemokines that promote tissue regeneration, modulate the inflammatory response, and have an antibacterial effect owing to the chemotaxis of neutrophils, fibroblasts, macrophages, and smooth muscle cells to the wound site.^4,7,8,10 

The use of PG in diabetic wounds has been recommended by the Italian Society of Transfusion Medicine and Immunohaematology since 2012, and use of this modality has increased since then.^11-13

In 2018, an observational study of patients with diabetic foot ulcers treated with PG over 45 months at Centro Hospitalar Universitário do Porto, Porto, Portugal, was published.¹⁴ Patients were treated with homologous PG obtained from blood donations. Patient comorbidities, number and time of treatment, and outcomes were evaluated. PG appeared to be an effective therapeutic alternative for chronic ulcers, provided compliance and effective metabolic control were ensured.¹⁴ 

The current study builds on that previous study, with the observation period lengthened and number of patients increased to evaluate not only PG effectiveness and safety, but also the possible correlation between response to treatment and patient comorbidities.

Patients

All patients with diabetic ulcers treated with homologous PG between January 2014 and October 2022 were included. Patients were followed up at the Diabetic Foot Multidisciplinary Unit. PG was proposed as a therapeutic option by the endocrinologist, and patient eligibility was assessed by the hematologist. The main inclusion criterion was the presence of a chronic (>4 weeks’ duration) diabetic ulcer that was unresponsive to conventional treatment measures. Patients with infected wounds, osteomyelitis, completely necrotic ulcers, or active oncological disease were excluded. Therefore, only patients with Wagner grades 1 and 2 DLEU were included.

Data collected included sex, age at the first PG application, comorbidities (hypertension, peripheral obstructive arterial disease, dyslipidemia, distal sensorimotor polyneuropathy, retinopathy, nephropathy, ischemic heart disease, and obesity), HbA_1c prior to the commencement of PG treatment, ulcer characteristics (localization, ulcer area, type of tissue [ie, granulated tissue, with some necrotic zone, with epithelialization, with fibrin]), presence vs. absence of inflammatory signs, presence vs. absence of associated pain, number of applications, treatment duration in weeks, and outcome. The clinical evolution, that is, ulcer characteristics and pain improvement, was evaluated weekly. Outcome was classified as complete response (complete healing of the ulcer with reepithelialization), partial response (≥50% reduction in wound area and/or improvement of pain if initially present), or absence of response (no positive evolution after 6 continuous weeks of treatment, or initial partial response but aggravation of the ulcer and/or pain in the following weeks with treatment). Photographs were taken of all patients before, during and after treatment.

Prior to treatment, all patients provided written informed consent to undergo the treatment and to the possible use of their data for publication. Because the patients provided such consent, the need for ethical approval of this study was waived.

Platelet gel

PG was obtained from whole blood donations. The donors were selected in accordance with European Union directives 2002/98/EC, 2004/33/EC, 2005/61/EC, and 2005/62/EC, as well as Portuguese national law number 185/2015.¹⁵ The specific criteria used to select the donations used to produce PG were as follows: donor platelet count greater than 200 × 10⁹/L and no current medication that could interfere with platelet function (eg, nonsteroidal anti-inflammatory drugs). All donations were negative for HIV, hepatitis C virus, hepatitis B virus, and syphilis.

As reported in the initial 2018 study with 45-month follow-up, the whole blood collected in a bag containing citrate phosphate dextrose was centrifuged (speed, 1848 RCF; acceleration, 8; brake, B4; time, 4.40 minutes; temperature, 22ºC), and an erythrocyte concentrate and PRP were obtained.¹⁴ A second centrifugation of PRP was carried out (speed, 4393 RCF; acceleration, 9; brake, B6; time, 6.30 minutes; temperature, 22ºC) to obtain platelet-poor plasma and a layer of platelet and leucocytes. This layer was resuspended in approximately 60 mL plasma and aliquoted into 4 satellite bags (TeT Kabi Fresenius bags, ref. 8002125) and frozen at −30ºC.

On the day of application, the aliquot was thawed at 37ºC for 10 minutes after which, in a sterile environment, it was activated with 10% calcium gluconate (ratio of 1.5 mL 10% calcium gluconate: 15 mL platelet concentrate) to form a PG constituted by activated platelets, leucocytes, and fibrin. The maximum time from activation to application of the PG was 8 hours.

The ulcer was cleaned and debrided, and the PG was applied, covering the entire area of the lesion. A nonadherent gauze patch was applied. 

Statistics

Statistical analysis was performed using SPSS version 26.0 (IBM Corporation). The chi-square test was used to compare groups. A P value of less than .05 was considered statistically significant.

Eighty-one patients (63 males, 18 females) with chronic diabetic ulcers unresponsive to standard treatment were included in the study. The median age was 65 years (range, 35–89 years). The study period was 106 months.

In addition to diabetes, patients had multiple comorbidities, with hypertension in 65 patients, peripheral obstructive arterial disease in 56, dyslipidemia in 48, distal sensorimotor polyneuropathy in 41, retinopathy in 25, nephropathy in 24, ischemic heart disease in 23, and obesity in 19. Sixty-two patients had 3 or more comorbidities. Prior to the first PG application, the median HbA_1c was 7.6% (range, 5.2%–14.4%).

Forty-nine patients (60.5%) had Wagner grade 2 ulcers, and 32 (39.5%) had Wagner grade 1 ulcers. Ulcer location was as follows: plantar in 21 patients, toe or hallux amputation stump in 14, malleolus in 13, calcaneus in 12, toe or hallux in 12, lower leg in 5, and metatarsus in 4. The median ulcer area was 2.9 cm² (range, 0.03 cm²–49 cm²). 

The median number of PG applications per patient was 17 (range, 1–67) during a median time of 9 weeks (range, 1–32 weeks). The median application schedule was twice a week.

It was not possible to evaluate efficacy in 12 patients. Four stopped the treatment after only 2 applications because of size, exudate, and poor glycemic control; 4 were suspended for poor compliance; 2 died of conditions unrelated to the treatment; 1 patient had a stroke and suspended the treatment; and 1 patient was lost to follow-up after 2 applications. In the remaining 69 patients, complete response was observed in 22 patients (32%), partial response in 12 patients (17%), and absence of response in 35 patients (51%).

In 7 of the 81 patients, gel was applied on 2 different ulcers. Of these 7 patients, 2 had complete response in both ulcers, 2 had complete response in 1 ulcer and absence of response in the other, 1 had complete response in 1 ulcer and partial response in the other, 1 had partial response in 1 ulcer and absence of response in the other, and 1 had absence of response in both ulcers.

Fourteen of the 69 patients presented with infected ulcer during the treatment period and required temporary suspension; treatment was restarted after the infection was resolved. Of these 14 patients, 2 achieved a complete response and 4 a partial response, and 8 experienced an absence of response.

Figure 1 shows the evolution of a plantar ulcer over a 24-month period in a 58-year-old male with hypertension, dyslipidemia, and peripheral obstructive arterial disease. The patient received 17 applications of PG during a 9-week period and achieved complete healing. Figure 2 shows the evolution of an ulcer above the calcaneus over an 8-month period in an 82-year-old male with peripheral obstructive arterial disease. Although initially the ulcer appeared to be improving, it did not respond to treatment, and treatment was stopped after 9 weeks (17 applications).

No statistically significant relationship was observed between response (partial or complete) and the presence of peripheral obstructive arterial disease, hypertension, dyslipidemia, retinopathy, nephropathy, ischemic heart disease, obesity, sex, age, HbA_1c, the presence of 3 or more comorbidities, or the development of infection during treatment (Table). A significant relationship was noted between the presence of distal sensorimotor polyneuropathy and response, with worse outcomes in patients with polyneuropathy (P = .041) (Table). 

No adverse events or reactions related to the PG were reported. 

DLEU is a serious diabetes-related complication. When standard treatment measures are unsuccessful, newer therapeutic options such as PG may be beneficial for wound healing. The efficacy of PG has been observed in multiple studies.^4,16,17 Patients with DLEUs usually have severe complications and comorbidities, with the need for polymedication that can interfere with platelet function, which can limit the use of autologous platelet-derived therapies. Therefore, allogenic sources have been used and shown to be efficient.^17,18 

In the current study, allogenic PG obtained from whole blood donors was used, utilizing a standardized processing method previously validated and employed by other authors.¹⁹ Allogenic PG was used because most patients had severe complications of diabetes and comorbidities, with 77% of patients having 3 or more comorbidities. These chronic DLEUs were refractory to standard treatment. PG had an overall beneficial effect, with 32% of patients achieving a complete response and 17% achieving a partial response (most with a very good partial response, with pain relief and only a residual lesion remaining). Some patients reported pain relief and decreased need for analgesics, but objective quantification of this finding was not possible.

Although not evaluated, individual biological characteristics of patients and donors could influence outcomes. 

Patient age, sex, HbA_1c prior to treatment, and most comorbidities noted, including peripheral obstructive arterial disease, had no significant effect on healing. Interestingly, statistically significant worse outcomes were observed in patients with polyneuropathy, but the authors observed a trend toward major initial ulcer area in patients with neuropathy compared with patients without neuropathy (median, 8 cm² and 6 cm², respectively). However, the number of patients in the subgroups was too small to achieve statistical power. More prospective studies are needed to validate this finding.

Infection during the treatment course, with postponement of PG application until infection control was achieved, had no effect on outcomes.

Although the findings were not measurable, a better and faster response was observed in patients with good compliance with hygiene, rest, walking, and diet. 

Patient adherence to therapy was good because PG is minimally invasive and easy to apply. Treatment was stopped because of poor compliance in only 4 patients. These patients had a history of poor compliance with other therapies and were lost to follow-up. No adverse reactions to PG were reported.

The first limitation of this study is that the different patient subgroups were too small to achieve statistical power. The second limitation is that HBA_1c and ulcer area were not recorded prior to treatment for all patients. The third limitation is the lack of a control group. 

The authors of the current study consider homologous PG to be a safe and possibly effective therapeutic alternative in patients with DLEUs that are unresponsive to standard therapies. It is believed that the use of PG will positively affect patients’ quality of life and minimize the long-term health care burden of diabetic foot ulcers.