Quiescent platelets stimulate angiogenesis and diabetic wound repair.
BACKGROUND
Platelets partake in hemostasis, wound healing, and tumor growth. Although platelet-rich-plasma (PRP) has been used in surgery for several years, its mechanism of action and application methods are still poorly characterized.


METHODS
A single unit of human platelets obtained by plateletpheresis was diluted in plasma and divided into three equal volumes. One volume was stored at room temperature as fresh platelets (RT), another volume was frozen by storage at -80 degrees C (FZ), and the third volume was frozen at -80 degrees C with 6% DMSO (FZ6). Plasma (PL) was used as control. Using flow cytometry, platelets were tested for platelet glycoprotein GPIb and annexin V binding, as survival and activation markers, respectively. Hemostatic function was assessed by thromboelastometry. In vivo, platelets were topically applied on 1 cm,(2) full-thickness wounds on db/db mice (n = 10/group) and healing was staged microscopically and macroscopically.


RESULTS
All platelet preparations showed hemostatic ability. RT platelets were GPIb positive (nonactivated-quiescent platelets) and stimulated angiogenesis by threefold, and cell proliferation by fourfold in vivo. FZ platelets were positive for annexin V, indicating activated platelets and, in vivo, increased only wound granulation. FZ6 platelets contained 30% nonactivated-quiescent and 50% activated platelets and stimulated granulation, angiogenesis, cell proliferation, and promoted re-epithelialization in vivo.


CONCLUSIONS
Platelets showed distinct mechanisms to induce hemostasis and wound healing. Quiescent platelets are required to induce angiogenesis in vivo. Platelets stored at room temperature and frozen with 6% DMSO and stored at -80 degrees C achieved optimal wound healing in diabetic mice.
Pietramaggiori
Giorgio
G
Division of Plastic Surgery, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Scherer
Saja S
SS
Mathews
Jasmine C
JC
Gennaoui
Tony
T
Lancerotto
Luca
L
Ragno
Gina
G
Valeri
C Robert
CR
Orgill
Dennis P
DP
D000818:Animals; D001792:Blood Platelets; D015925:Cryopreservation; D003451:Cryoprotective Agents; D048909:Diabetes Complications / Q000628:therapy*; D004121:Dimethyl Sulfoxide; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018919:Neovascularization, Physiologic; D053657:Platelet-Rich Plasma; D014945:Wound Healing
D003451:Cryoprotective Agents; D004121:Dimethyl Sulfoxide