Initial studies in animals have shown that in skeletal muscle the repair mechanisms following injury involve expression of two different insulin-like growth factor-1 (IGF-1) splice variants: IGF-1Ea and IGF-1Ec (MGF). These are known to play different roles in muscle repair (Goldspink 1999, Hill and Goldspink 2003). Both up regulate protein synthesis and MGF replenishes the muscle satellite (stem) cell pool that is important for muscle repair. The levator ani (LA) muscle is the main muscle responsible for providing functional support for the different pelvic organs in women. It is also the main muscle that is directly affected by increased intra-abdominal pressure during pregnancy and the strains of vaginal delivery. Damage to the LA muscle following vaginal delivery often results, in the short and long term pelvic floor dysfunction resulting in genitourinary prolapse and incontinence (Allen et al. 1990, MacClennan et al. 2000

This work was given ethical approval by the LREC at The Royal Free Hospital. Fourteen nulliparous women were recruited following vaginal delivery. Biopsies were conducted vaginally on the pubo-visceral component of the LA muscle under epidural analgesia when a tear had occurred or an episiotomy was required to expedite delivery. Ten women attending the Gynaecology Clinic for other reasons than pelvic floor dysfunction were recruited as controls and biopsies obtained under general anaesthetic. Samples ranging from 20 to 40 mg were processed using Real Time Quantitative Polymerase Chain Reaction (RT-PCR). From the delivery group five controls were obtained from the pubo-visceral component of the LA muscle. Part of the biopsy sample was incubated in formalin and paraffin-wax embedded sections were stained with an antibody for MGF. RNA was extracted from the rest of the samples using RNAeasy and reverse transcribed into cDNA. This was then analysed by Real Time RT-PCR using Roche Light Cycler technology with oligonucleotide primers that selectively amplify the two IGF-I splice variants (Hameed et al. 2003).

Compared with the control population (Mann-Whitney test, statistical significance P < 0.05), MGF mRNA levels after delivery showed a marked elevation ranging between 1.81x 10-8 to 8.76×10-6 µg mg-1 (P < 0.02). IGF-1Ea was even more up regulated with values of 4.05×10-8 to 3.16×10-3 µg mg-1 post delivery (P < 0.04). Statistical analysis of these pilot data (Spearman’s correlation test), suggested correlation between the expression of IGF-1 splice variants and length of the second stage. There was no statistical correlation between mother’s BMI, baby’s weight, and age, IGF-1 splice variants. However, individual variations seen in the population studied may reveal those women showing a poor muscle repair capacity and therefore at risk for pelvic floor dysfunction.

This work was supported by the Wellcome Trust.