Immunoporosis: Role of immune system in the pathophysiology of different types of osteoporosis

Abstract

Osteoporosis is a skeletal system disease characterized by low bone mass and altered bone microarchitecture, with an increased risk of fractures. Classical theories hold that osteoporosis is essentially a bone remodeling disorder caused by estrogen deficiency/aging (primary osteoporosis) or secondary to diseases/drugs (secondary osteoporosis). However, with the in-depth understanding of the intricate nexus between both bone and the immune system in recent decades, the novel field of “Immunoporosis” was proposed by Srivastava et al. (2018, 2022), which delineated and characterized the growing importance of immune cells in osteoporosis. This review aimed to summarize the response of the immune system (immune cells and inflammatory factors) in different types of osteoporosis. In postmenopausal osteoporosis, estrogen deficiency-mediated alteration of immune cells stimulates the activation of osteoclasts in varying degrees. In senile osteoporosis, aging contributes to continuous activation of the immune system at a low level which breaks immune balance, ultimately resulting in bone loss. Further in diabetic osteoporosis, insulin deficiency or resistance-induced hyperglycemia could lead to abnormal regulation of the immune cells, with excessive production of proinflammatory factors, resulting in osteoporosis. Thus, we reviewed the pathophysiology of osteoporosis from a novel insight-immunoporosis, which is expected to provide a specific therapeutic target for different types of osteoporosis.

The Uncharted Landscape of Rare Endocrine Immune-Related Adverse Events

“…Osteoporosis is developed under multiple factors, including genetic factors as well as a range of other acquired and modifiable risk factors. Recently, there has been increasing interest to study the immune involvement in its pathogenesis [ 95 ]. Although current guidelines provide no evidence of direct or indirect effect of ICI therapy on bone metabolism, some published data have proposed that immune activation by ICIs may adversely impact bone remodeling.…”

“…The immune system is considered to play an integral role in the pathogenesis of osteoporosis [ 95 ]. Activated immune cells either directly or indirectly through the secretion of various cytokines and factors regulate bone remodeling.…”

Plasma serotonin precursors and metabolite are correlated with bone mineral density and bone turnover markers in patients with postmenopausal osteoporosis

“…4,5 PMOP patients face the risk of osteoporotic fractures as high as 30-40%, making it one of the most urgent clinical problems to be solved. 6 Bone mineral density (BMD) assessed by dual X-ray absorptiometry (DXA) and the incidence of osteoporotic fractures are the basis of the operational diagnosis of OP. 7,8 PMOP is a high-bone turnover disease with increased bone resorption and bone formation.…”

“…7,8 PMOP is a high-bone turnover disease with increased bone resorption and bone formation. 6 The markers of bone turnover consist of a constellation of proteins or protein derivatives released by osteoblasts or osteoclasts in the process of bone remodeling. 9 Specifically, procollagen type I N-propeptide (PINP) is a marker for bone formation, and β-C-terminal telopeptide of type 1 collagen (β-CTX) is a bone resorption marker.…”

“…4,5 PMOP patients face the risk of osteoporotic fractures as high as 30–40%, making it one of the most urgent clinical problems to be solved. 6…”