Interest of Bone Histomorphometry in Bone Pathophysiology Investigation: Foundation, Present, and Future

Abstract

Despite the development of non-invasive methods, bone histomorphometry remains the only method to analyze bone at the tissue and cell levels. Quantitative analysis of transiliac bone sections requires strict methodologic conditions but since its foundation more 60 years ago, this methodology has progressed. Our purpose was to review the evolution of bone histomorphometry over the years and its contribution to the knowledge of bone tissue metabolism under normal and pathological conditions and the understanding of the action mechanisms of therapeutic drugs in humans. The two main applications of bone histomorphometry are the diagnosis of bone diseases and research. It is warranted for the diagnosis of mineralization defects as in osteomalacia, of other causes of osteoporosis as bone mastocytosis, or the classification of renal osteodystrophy. Bone biopsies are required in clinical trials to evaluate the safety and mechanism of action of new therapeutic agents and were applied to anti-osteoporotic agents such as bisphosphonates and denosumab, an anti-RANKL, which induces a marked reduction of the bone turnover with a consequent elongation of the mineralization period. In contrast, an increased bone turnover with an extension of the formation site is observed with teriparatide. Romosozumab, an anti-sclerostin, has a dual effect with an early increased formation and reduced resorption. Bone histomorphometric studies allow us to understand the mechanism of coupling between formation and resorption and to evaluate the respective role of bone modeling and remodeling. The adaptation of new image analysis techniques will help bone biopsy analysis in the future.

Keywords: bone biopsy; bone disease; histomorphometry; mechanism of action of treatment; modeling; remodeling.

Figure 1

Double tetracycline labels. Unstained section under ultraviolet light; x100.

Figure 2

(A) Bone section stained with solochrome cyanin R under polarized light showing the lamellar texture of bone tissue (x100); (B) Goldner trichrome differentiates mineralized bone in green and osteoid seam covered by osteoblasts (Ob) in red (x200); (C) Mast cells (*) in bone marrow characterized by the presence of metachromatic granules in the cytoplasm after toluidin blue pH 2.6 staining (x400); (D) Aluminon staining showing the aluminum deposition (→) along the calcification front (x100); (E).TRAP staining of osteoclasts (Oc) (x200); (F): Microcrack (→) stained after bulk staining with xylenol orange (x200).

Figure 3

The measurement of the trabecular bone volume in osteoporotic patients with one vertebral fracture allowed to define a “vertebral fracture threshold” at 11% [From Meunier et al. (126)].

Figure 4

Osteomalacia is characterized by thick and extended osteoid seams (A, solochrome cyanin R, x100) and diffuse tetracycline labels (►) (B, unstained section under ultraviolet ligth; x100).

Figure 5

Different histological forms of renal osteodystrophy. (A) High bone remodeling with increased bone resorption (R) and formation (F) associated with numerous tetracycline labels (→) (B); Osteomalacia with thick osteoid seams (C) and diffuse tetracycline labels (Δ) (D) ;Adynamic bone with no active bone surface (E) with no tetracycline label (F). (A, C, E), Goldner trichrome; (B, D, F), unstained sections under ultraviolet light; x100.

Figure 6

Trabecular perforation due to osteoclastic (Oc) resorption. Goldner trichrome; x100.

Figure 7

Skeletal fluorosis characterized by an osteosclerosis with increased osteoid surfaces and mineralization defects in the trabeculae and around the osteocyte lacunae. Solochrome cyanin R; x50.