The effect of low-molecular-weight heparin on rat tendon healing

Abstract

We investigated the effect of low-molecular-weight heparin (LMWH) on the healing of tendons. Forty-five adult Wistar rats weighing 300 g were randomized into three groups equal in number. All the rats underwent full-thickness surgical incision of the Achilles tendon followed by primary repair. After the operation, two groups received daily subcutaneous LMWH injections (nadroparin calcium) for four weeks at high or low doses (group I, 6 mg/kg, 170 IU AXa; group II, 3 mg/kg, 85 IU AXa). Group III remained untreated as the control group. Histologically, the specimens were examined under light and electron microscopy with regard to the amount of fibrillar collagen synthesis, mitochondrial degeneration, and the composition of the extracellular matrix collagen. Biomechanically, maximum load to failure and correspondent elongation of the tendons were measured. Compared to the control group, histologically, both LMWH-treated groups exhibited increased number of fibroblasts, increased fibrillar collagen formation in the extracellular matrix, and higher counts of granular endoplasmic reticula in cytoplasmic contents of fibroblasts as well as decreased mitochondrial vacuolization and degeneration. Biomechanical assessments showed that tendons in group I had significantly higher maximum load to failure and elongation values than group II and III (31 N vs. 24.6 N and 23.1 N; 25 mm vs. 19.6 mm and 17.3 mm, respectively; p<0.05). Groups II and III did not differ significantly in this respect (p>0.05). Daily administration of single dose LMWH improves tendon healing through increasing the number of fibroblasts and fibrillar collagen synthesis and decreasing mitochondrial degeneration.