Cellular senescence is suspected to be a central contributing cause, a belief which is supported by benefits seen in patients given senolytic therapy.It is hypothesized that the initial or repetitive injury in IPF occurs to the lung cells, called alveolar epithelial cells (AECs, pneumocytes), which line the majority of the alveolar surface. When type I AECs are damaged or lost, it is thought that type II AECs undergo proliferation to cover the exposed basement membranes. In normal repair, the hyperplastic type II AECs die and the remaining cells spread and undergo a differentiation process to become type I AECs. Under pathologic conditions and in the presence of transforming growth factor beta (TGF-β), fibroblasts accumulate in these areas of damage and differentiate into myofibroblasts that secrete collagen and other proteins. In the current classification of the pathogenesis of IPF, it is believed that it occurs by way of the formation of a UIP (usual interstitial pneumonia) lesion, which then undergoes the aforementioned pathological condition characteristic of IPF. Other proposed repeated injury mechanisms indicate that IPF may result not just from a UIP lesion, but also from NSIP and DAD (nonspecific interstitial pneumonia and diffuse alveolar damage) lesions, or a combination of several. In the past, it was thought that inflammation was the first event in initiating lung tissue scarring. Later findings showed that the development of fibroblastic foci precedes the accumulation of inflammatory cells and the consequent deposition of collagen.
Spotting is more common in longer cycles. A womans vulva may swell just prior to ovulation, especially the side on which ovulation will occur. One of the groin lymph nodes (on the side on which ovulation will occur) will swell to about the size of a pea, and may become tender. Causes
Mittelschmerz is believed to have a variety of causes:

Follicular swelling: The swelling of follicles in the ovaries prior to ovulation. While only one or two eggs mature to the point of being released, a number of follicles grow during the follicular phase of the menstrual cycle (non-dominant follicles atrophy prior to ovulation). Because follicles develop on both sides, this theory explains mittelschmerz that occurs simultaneously on both sides of the abdomen.Ovarian wall rupture: The ovaries have no openings; at ovulation the egg breaks through the ovarys wall. This may make ovulation itself painful for some women. Fallopian tube contraction: After ovulation, the fallopian tubes contract (similar to peristalsis of the esophagus), which may cause pain in some women. Smooth muscle cell contraction: At ovulation, this pain may be related to smooth muscle cell contraction in the ovary as well as in its ligaments. These contractions occur in response to an increased level of prostaglandin F2-alpha, itself mediated by the surge of luteinizing hormone (LH).Irritation: At the time of ovulation, blood or other fluid is released from the ruptured egg follicle. This fluid may cause irritation of the abdominal lining.